Neuromuscular Blockade in ICU

Quick Answer

Neuromuscular blocking agents (NMBAs) are used in the ICU for severe ARDS (P/F ratio below 150), refractory intracranial hypertension, facilitation of mechanical ventilation, and prevention of shivering during targeted temperature management. Cisatracurium is the preferred agent due to Hofmann elimination (organ-independent metabolism). Train-of-four (TOF) monitoring should target 1-2 twitches to avoid over-paralysis. The ACURASYS trial (2010) showed 48-hour cisatracurium infusion reduced 28-day mortality in severe ARDS (15.6% vs 23.7%), but the ROSE trial (2019) found NO benefit when compared to light sedation strategies. Deep sedation (RASS -4 to -5) is mandatory during paralysis to prevent awareness. Major complications include ICU-acquired weakness (ICUAW), prolonged paralysis, anaphylaxis (especially rocuronium), and venous thromboembolism.

CICM Exam Focus

Written Exam Priorities

Indications: Severe ARDS, intracranial hypertension, ventilator dyssynchrony, shivering
Pharmacology: Cisatracurium (Hofmann), rocuronium/vecuronium (hepatic/renal), depolarizing vs non-depolarizing
Monitoring: Train-of-four technique, target 1-2 twitches, BIS monitoring for sedation depth
Complications: ICUAW pathophysiology, prolonged paralysis, anaphylaxis rates, VTE risk
Evidence: ACURASYS vs ROSE trial findings and clinical implications
Reversal: Neostigmine vs sugammadex, dosing, contraindications

Viva Exam Scenarios

Management of severe ARDS patient requiring prone positioning and paralysis
Troubleshooting prolonged paralysis after cisatracurium infusion
Differential diagnosis of weakness after ICU discharge (ICUAW vs Guillain-Barré)
Choice of NMBA in patient with acute kidney injury and liver failure

Hot Topics

Light sedation vs deep sedation + paralysis (ROSE trial implications)
Role of NMBAs in COVID-19 ARDS
Early mobilization vs paralysis in critical illness
Sugammadex availability and cost-effectiveness in ICU
Continuous EEG monitoring in paralyzed patients

Key Points

Indications: Severe ARDS (P/F below 150), intracranial hypertension, severe ventilator dyssynchrony, prevention of shivering during TTM
Agent Selection: Cisatracurium is preferred in multiorgan failure (Hofmann elimination); rocuronium for rapid onset if intubating
Monitoring: TOF target 1-2 twitches; deep sedation (RASS -4 to -5) mandatory; BIS 40-60 if available
Duration: Limit to 48 hours in ARDS; shortest duration possible to allow neurological assessment
Complications: ICUAW (25-50% if greater than 5 days ventilation), prolonged paralysis, anaphylaxis, VTE, awareness
Evidence: ACURASYS showed benefit but ROSE trial (2019) showed NO benefit with light sedation—use as rescue therapy
Reversal: Sugammadex 2-4 mg/kg for rocuronium/vecuronium; neostigmine for routine reversal
Contraindications: Personal/family history of malignant hyperthermia, neuromuscular disorders (relative), severe hyperkalemia (for succinylcholine)

Epidemiology

Incidence and Prevalence

ICU usage: Approximately 10-20% of mechanically ventilated ICU patients receive NMBAs
ARDS: Up to 30-40% of severe ARDS patients (P/F below 150) may receive neuromuscular blockade
Duration: Median duration of paralysis typically 24-48 hours (ACURASYS protocol)
Trends: Decreased use since ROSE trial (2019); shift from routine to rescue therapy

Risk Factors for Prolonged Paralysis

Renal failure: Vecuronium active metabolite (3-desacetyl-vecuronium) accumulates
Hepatic failure: Rocuronium and vecuronium clearance reduced (biliary excretion)
Acidosis: Slows Hofmann elimination of cisatracurium (prolonged effect)
Hypothermia: Slows Hofmann elimination of cisatracurium (prolonged effect)
Elderly: Reduced clearance and increased volume of distribution
Concurrent medications: Aminoglycosides, magnesium, corticosteroids potentiate NMBAs

ICU-Acquired Weakness (ICUAW)

Incidence: Affects 25-50% of patients ventilated for greater than 5 days
Risk factors: NMBA use (especially with corticosteroids), sepsis, hyperglycemia, immobility, multi-organ failure
Subtypes: Critical illness polyneuropathy (CIP), critical illness myopathy (CIM), critical illness neuromyopathy (CINM)
Long-term impact: Prolonged ventilation, delayed ICU discharge, persistent functional disability

Key PMIDs:

27171491 (Murray 2016 - NMBA guidelines)
20843245 (ACURASYS trial)
31112383 (ROSE trial)
24717781 (ICUAW systematic review)

Pathophysiology

Neuromuscular Junction Physiology

Acetylcholine release: Motor neuron depolarization → calcium influx → ACh release into synaptic cleft
Receptor binding: ACh binds to nicotinic receptors on motor end-plate
Muscle depolarization: Sodium influx → action potential → sarcoplasmic reticulum calcium release
Contraction: Calcium binds troponin → myosin-actin cross-bridge formation → muscle shortening
ACh degradation: Acetylcholinesterase rapidly hydrolyzes ACh (termination of signal)

Mechanism of Non-Depolarizing NMBAs

Competitive antagonism: Bind to nicotinic receptors without activation (no depolarization)
Blockade: Prevent ACh from binding and activating receptors
Dose-dependent: Increasing dose increases receptor occupancy and depth of blockade
Reversible: Can be reversed by increasing ACh concentration (neostigmine) or encapsulation (sugammadex)
Classes: Aminosteroids (rocuronium, vecuronium) vs Benzylisoquinoliniums (cisatracurium, atracurium)

Mechanism of Depolarizing NMBAs (Succinylcholine)

Agonist: Binds and activates nicotinic receptors
Prolonged depolarization: Not degraded by acetylcholinesterase → sustained depolarization
Phase I block: Receptors desensitized and unable to respond to further ACh
Fasciculations: Initial muscle twitching due to depolarization before paralysis
Rapid onset/offset: Degraded by plasma cholinesterase (duration 5-10 minutes)
Not used in ICU: Risk of hyperkalemia, malignant hyperthermia, and prolonged paralysis with infusions

Hofmann Elimination (Cisatracurium)

Spontaneous degradation: pH- and temperature-dependent chemical breakdown
Organ-independent: Does NOT require hepatic or renal function
Factors affecting clearance:
- "Acidosis: Slows elimination (prolonged blockade)"
- "Alkalosis: Accelerates elimination (shortened blockade)"
- "Hypothermia: Slows elimination (prolonged blockade)"
- "Hyperthermia: Accelerates elimination (shortened blockade)"
Metabolite: Laudanosine (CNS stimulant, theoretical seizure risk but clinically negligible)
Ester hydrolysis: Minor pathway (~16% of total clearance)

Pharmacokinetics of Common ICU NMBAs

Agent	Onset	Duration	Metabolism	Active Metabolite	Organ Dependence
Cisatracurium	3-5 min	30-40 min	Hofmann elimination	Laudanosine (minimal risk)	None (ideal for organ failure)
Rocuronium	1-2 min	30-40 min	Hepatic (biliary 50-70%)	Minimal	Hepatic > Renal
Vecuronium	3-5 min	30-40 min	Hepatic (biliary 40-70%)	3-desacetyl (50-80% potent)	Hepatic > Renal
Atracurium	3-5 min	30-40 min	Hofmann + ester hydrolysis	Laudanosine (higher levels)	None

ICU-Acquired Weakness Pathophysiology

Systemic inflammation: Sepsis/SIRS → cytokine release → microvascular damage to nerves/muscles
Mitochondrial dysfunction: Impaired ATP production → muscle atrophy
Disuse atrophy: Complete immobility → 2-3% muscle mass loss per day in first week
Thick filament loss: Corticosteroids + NMBAs → myosin degradation (steroid myopathy)
Axonal degeneration: Critical illness polyneuropathy (CIP) from ischemia and metabolic derangements
Receptor proliferation: Prolonged NMBA use → upregulation of extrajunctional ACh receptors (hyperkalemia risk if succinylcholine given)

Key PMIDs:

19445675 (Hofmann elimination pharmacology)
16424729 (NMBA pharmacokinetics in critical illness)
23361625 (ICUAW pathophysiology)

Clinical Presentation

Indications for Neuromuscular Blockade

1. Severe Acute Respiratory Distress Syndrome (ARDS)

Criteria: P/F ratio below 150 mmHg with PEEP ≥5 cmH2O (Berlin definition moderate-to-severe ARDS)
Mechanism of benefit:
- Improved patient-ventilator synchrony
- Reduced oxygen consumption and CO2 production
- Decreased inflammatory cytokine release
- Prevention of ventilator-induced lung injury (VILI) from dyssynchrony
Current evidence: ACURASYS showed benefit; ROSE showed NO benefit with light sedation
Current practice: Reserve for rescue therapy in refractory hypoxemia or severe dyssynchrony

2. Intracranial Hypertension

Indication: Refractory ICP greater than 20-25 mmHg despite sedation, osmotic therapy, and CSF drainage
Mechanism:
- Prevents coughing/bucking against ventilator (coughing increases intrathoracic pressure → reduced jugular venous drainage → ICP spike)
- Improves ventilator synchrony → better CO2 control (hypercapnia causes cerebral vasodilation)
- Reduces metabolic demand
Limitations: Masks neurological examination (pupillary response only reliable sign)
Monitoring: Continuous EEG if high seizure risk; ICP monitoring mandatory

3. Severe Ventilator Dyssynchrony

Definition: Patient-ventilator asynchrony despite optimization of sedation and ventilator settings
Types: Flow dyssynchrony, trigger dyssynchrony, double-triggering, ineffective efforts
Mechanism: NMBAs eliminate spontaneous breathing efforts → full ventilator control
Consider first: Adjust ventilator settings, optimize sedation/analgesia, treat underlying cause
Last resort: NMBA if life-threatening gas exchange abnormalities persist

4. Shivering During Targeted Temperature Management (TTM)

Indication: Shivering refractory to first/second-line therapies (buspirone, magnesium, opioids, dexmedetomidine)
Mechanism: Shivering increases oxygen consumption by 100-600% → counteracts hypothermia, increases metabolic demand
Monitoring: Bedside Shivering Assessment Scale (BSAS); NMBAs are Tier 3 intervention
Duration: Minimum necessary to achieve target temperature (usually 32-36°C)

5. Facilitation of Procedures

Prone positioning: Severe ARDS requiring prolonged prone ventilation
Therapeutic hypothermia: Post-cardiac arrest care
High-frequency oscillatory ventilation (HFOV): Now rarely used after OSCILLATE trial
Airway interventions: Difficult airway management, surgical airway

6. Other Indications

Status asthmaticus: Life-threatening bronchospasm unresponsive to maximal medical therapy
Tetanus: Muscle rigidity and spasms
Status epilepticus: Refractory seizures (NMBA does NOT treat seizures, only masks physical manifestations)
Abdominal compartment syndrome: Facilitate decompression or temporizing measures

Contraindications

Absolute Contraindications

Known/suspected malignant hyperthermia (personal or family history)
Severe hyperkalemia (for succinylcholine specifically; K+ greater than 5.5 mmol/L)
Acute phase of burn injury (greater than 24 hours to 1-2 years post-burn; risk of hyperkalemia with succinylcholine)
Acute denervation injury (spinal cord injury, Guillain-Barré, stroke greater than 48 hours; succinylcholine risk)

Relative Contraindications

Neuromuscular disorders: Myasthenia gravis, Lambert-Eaton syndrome (unpredictable response, prolonged paralysis)
Pre-existing weakness: Risk of further functional decline and ICUAW
Inability to monitor sedation depth: No BIS/EEG available and high risk of awareness
No clear indication: Avoid routine prophylactic use (ROSE trial findings)

Key PMIDs:

20843245 (ACURASYS - ARDS indication)
31112383 (ROSE - light sedation vs paralysis)
24499827 (Shivering management in TTM)

Investigations and Monitoring

Train-of-Four (TOF) Monitoring

Principle

Method: Four electrical impulses delivered over 2 seconds (2 Hz frequency) to a peripheral nerve
Response: Count number of muscle twitches (0 to 4)
Receptor blockade correlation:
- 4/4 twitches: 0-70% receptors blocked
- 3/4 twitches: 70-75% receptors blocked
- 2/4 twitches: 75-80% receptors blocked (target for most ICU patients)
- 1/4 twitches: 80-90% receptors blocked (acceptable target)
- 0/4 twitches: greater than 90% receptors blocked (risk of over-paralysis)

Target TOF Count

ICU standard: 1-2 twitches (85-90% receptor blockade)
Avoid 0/4: Complete paralysis increases risk of prolonged weakness and accumulation
Avoid 4/4: Inadequate paralysis if NMBA indicated

Monitoring Sites

1. Ulnar Nerve (Adductor Pollicis) - PREFERRED

Electrode placement: Along ulnar side of wrist
Response: Thumb adduction (adductor pollicis contraction)
Advantages: Most sensitive to NMBAs, best reflects peripheral neuromuscular function
Clinical correlation: If 1-2 twitches at thumb, diaphragm is adequately paralyzed
Considerations: Arm must be accessible (difficult in prone positioning)

2. Facial Nerve (Orbicularis Oculi) - ALTERNATIVE

Electrode placement: Temple/lateral to eye
Response: Eye twitch (orbicularis oculi) or eyebrow furrow (corrugator supercilii)
Advantages: Accessible in prone positioning, arm trauma, or severe edema
Disadvantages: More resistant to NMBAs (reflects diaphragm more closely), risk of direct muscle stimulation (false twitches)
Target: 0-1 twitches (deeper blockade needed at face to ensure adequate peripheral paralysis)

3. Posterior Tibial Nerve (Flexor Hallucis Brevis)

Electrode placement: Behind medial malleolus
Response: Big toe plantar flexion
Use: When upper extremities and face inaccessible
Correlation: Similar to ulnar nerve

TOF Ratio

Definition: Ratio of 4th twitch amplitude to 1st twitch amplitude (T4/T1)
Normal: T4/T1 greater than 0.9 (full recovery of neuromuscular function)
Clinical recovery: T4/T1 greater than 0.7 minimum for safe extubation (able to protect airway)
Fade: Characteristic of non-depolarizing blockade (4th twitch weaker than 1st)

Post-Tetanic Count (PTC)

Use: When TOF is 0/4 (complete blockade)
Method: 50 Hz tetanic stimulation for 5 seconds, followed by single twitches at 1 Hz
Count: Number of twitches after tetanus (0-15)
Interpretation: PTC 1-2 indicates very deep blockade; greater than 8-10 indicates impending TOF recovery

Sedation Depth Monitoring

RASS Limitations

Richmond Agitation-Sedation Scale (RASS): CANNOT be used in paralyzed patients (automatically scores -5)
Problem: Patient may be fully awake but "locked in" without ability to signal distress
Solution: Deep sedation MANDATORY; alternative monitoring required

Bispectral Index (BIS) Monitoring

Principle: Processed EEG from forehead electrodes → numerical value (0-100)
Target during paralysis: 40-60 (general anesthesia/deep sedation level)
below 40: Very deep sedation (risk of hemodynamic instability)
60-80: Light sedation (risk of awareness if paralyzed)
greater than 80: Awake or very light sedation (NEVER acceptable during paralysis)
Limitations: Artifact from electrocautery, muscle activity (less relevant when paralyzed), does not eliminate risk of awareness

Sedation Protocol During Paralysis

Minimum RASS target: -4 to -5 (deep sedation)
Agents: Propofol 25-75 mcg/kg/min OR midazolam 0.05-0.2 mg/kg/h PLUS fentanyl 25-200 mcg/h
Avoid "sedation vacations": DO NOT stop sedation while paralyzed
Communication: Talk to patient, explain procedures, orient to time/place (even if deeply sedated)
Analgesia-first: Ensure adequate analgesia before assessing sedation needs

Continuous EEG (cEEG) Monitoring

Indication: High seizure risk (TBI, post-cardiac arrest, known epilepsy, metabolic encephalopathy)
Rationale: NMBAs mask physical manifestations of seizures
Detection: Non-convulsive status epilepticus (NCSE) occurs in 10-20% of comatose ICU patients
Duration: Continue cEEG for entire period of paralysis

Physiological Indicators (Unreliable but Monitored)

Tachycardia: May indicate inadequate sedation/analgesia
Hypertension: May indicate awareness or pain
Diaphoresis: Sweating may indicate sympathetic activation
Lacrimation: Tearing may indicate pain/distress
LIMITATIONS: All can be masked by medications (beta-blockers, vasopressors, clonidine) or altered by critical illness

Laboratory Monitoring

Creatinine kinase (CK): Monitor for rhabdomyolysis if prolonged paralysis or concern for ICUAW
Electrolytes: Hypokalemia, hypophosphatemia, hypomagnesemia potentiate NMBAs
Liver function: Monitor if using hepatically-cleared agents (rocuronium, vecuronium)
Renal function: Monitor if using vecuronium (active metabolite accumulation)

Key PMIDs:

18317309 (TOF monitoring in ICU)
17667242 (BIS monitoring during paralysis)
23361625 (cEEG in paralyzed patients)

Management

Agent Selection

First-Line: Cisatracurium (Nimbex)

Pharmacology

Mechanism: Non-depolarizing benzylisoquinolinium
Metabolism: Hofmann elimination (organ-independent) + minor ester hydrolysis (16%)
Onset: 3-5 minutes
Duration: 30-40 minutes (single dose)
Potency: 3-4 times more potent than atracurium (lower laudanosine production)
Half-life: 22-25 minutes (unchanged in organ failure)

Dosing

Intubation: 0.15-0.2 mg/kg IV bolus
ICU infusion: 1-4 mcg/kg/min (titrate to TOF 1-2 twitches)
Loading dose: 0.1-0.15 mg/kg IV, then start infusion
Adjustment: Based on TOF monitoring, NOT organ function

Advantages

Organ-independent: Ideal for multiorgan failure, renal failure, hepatic failure
Predictable recovery: No accumulation in organ dysfunction
Cardiovascular stability: No histamine release at clinical doses (unlike atracurium)
Low laudanosine: Theoretical seizure risk negligible (unlike atracurium)

Disadvantages

Temperature/pH dependent: Hypothermia and acidosis prolong duration
Cost: More expensive than vecuronium
No rapid onset: Not ideal for emergency intubation (use rocuronium)

Special Considerations

Acidosis (pH below 7.25): Slows Hofmann elimination → reduce infusion rate
Hypothermia (below 35°C): Slows Hofmann elimination → reduce infusion rate
Renal failure: Safe to use; laudanosine levels remain clinically insignificant
Hepatic failure: Safe to use; metabolism organ-independent

Second-Line: Rocuronium (Zemuron)

Pharmacology

Mechanism: Non-depolarizing aminosteroid
Metabolism: Hepatic (biliary excretion 50-70%), renal (10-25%)
Onset: 1-2 minutes (fastest non-depolarizing NMBA)
Duration: 30-40 minutes
Potency: Low (ED95 0.3 mg/kg)
Active metabolite: Minimal/none

Dosing

Rapid sequence intubation: 1-1.2 mg/kg IV bolus
Routine intubation: 0.6-0.9 mg/kg IV bolus
ICU infusion: 8-12 mcg/kg/min (titrate to TOF)
Renal failure: Prolonged duration; reduce infusion rate
Hepatic failure: Prolonged duration; reduce infusion rate

Advantages

Rapid onset: Ideal for emergency intubation (alternative to succinylcholine)
Reversible: Sugammadex can rapidly reverse (1-3 minutes)
No histamine release: Cardiovascular stability

Disadvantages

Hepatic/renal dependence: Accumulation in organ failure
Anaphylaxis risk: Highest among NMBAs (1:6,500 incidence)
Prolonged paralysis: In ICU setting with organ dysfunction
Sugammadex cost: Expensive reversal agent

Special Considerations

Renal failure (CrCl below 30): Duration increased 1.5-2x; reduce infusion rate or switch to cisatracurium
Hepatic failure: Duration increased; reduce infusion rate or switch to cisatracurium
Sugammadex reversal: 2-4 mg/kg (dose based on depth of blockade)

Third-Line: Vecuronium (Norcuron)

Pharmacology

Mechanism: Non-depolarizing aminosteroid
Metabolism: Hepatic (biliary excretion 40-70%), renal (20-30%)
Onset: 3-5 minutes
Duration: 30-40 minutes
Potency: High (ED95 0.05 mg/kg)
Active metabolite: 3-desacetyl-vecuronium (50-80% as potent as parent; renally excreted)

Dosing

Intubation: 0.08-0.1 mg/kg IV bolus
ICU infusion: 0.8-1.2 mcg/kg/min (titrate to TOF)
Renal failure: AVOID continuous infusion (active metabolite accumulates)
Hepatic failure: Reduce infusion rate

Advantages

Cost: Least expensive NMBA
Cardiovascular stability: No histamine release

Disadvantages

Active metabolite: 3-desacetyl-vecuronium accumulates in renal failure → prolonged paralysis (can last days to weeks)
Hepatic/renal dependence: Unpredictable recovery in organ dysfunction
Prolonged paralysis: Most common NMBA associated with prolonged ICU weakness
Limited reversal: Sugammadex effective but less reliable than for rocuronium

Special Considerations

Renal failure: CONTRAINDICATED for continuous infusion (use cisatracurium instead)
Hepatic failure: Duration increased; use cisatracurium instead
Avoid in ICU: Generally replaced by cisatracurium or rocuronium in modern ICU practice

NOT Recommended in ICU: Atracurium (Tracrium)

Why Avoided

Histamine release: Significant at clinical doses → hypotension, tachycardia, bronchospasm
High laudanosine: 5-10x higher levels than cisatracurium → theoretical seizure risk
Less potent: Requires higher doses than cisatracurium → more side effects
Replaced: Cisatracurium is the preferred benzylisoquinolinium

NOT Used in ICU: Succinylcholine (Suxamethonium)

Why Avoided

Depolarizing: Different mechanism (prolonged depolarization, not competitive antagonism)
Short duration: 5-10 minutes (too short for ICU paralysis)
Hyperkalemia risk: Can cause life-threatening K+ release (especially in burns, denervation, chronic paralysis)
Malignant hyperthermia: Triggering agent
Prolonged paralysis: If given as infusion (desensitization blockade)
Use: Emergency intubation ONLY (replaced by rocuronium in many centers)

Dosing Protocols

ACURASYS Protocol (Historical - Severe ARDS)

Loading: Cisatracurium 0.15 mg/kg IV bolus
Infusion: Cisatracurium 37.5 mg/h (fixed dose for 70 kg patient; adjust for weight)
Duration: 48 hours continuous
Monitoring: No TOF monitoring used in original trial
Sedation: Deep sedation with propofol + sufentanil (RASS -5)
Current relevance: NO LONGER ROUTINE (ROSE trial showed no benefit with light sedation)

Modern ICU Paralysis Protocol (Rescue Therapy)

Indication: Refractory hypoxemia despite prone positioning, recruitment maneuvers, optimized ventilation
Agent: Cisatracurium (first-line) or rocuronium (second-line)
Loading: Cisatracurium 0.1-0.15 mg/kg IV bolus
Infusion: Cisatracurium 1-4 mcg/kg/min (titrate to TOF 1-2 twitches)
Monitoring: TOF every 4 hours; adjust infusion to maintain 1-2 twitches
Sedation: Propofol 25-75 mcg/kg/min OR midazolam 0.05-0.2 mg/kg/h PLUS fentanyl 25-200 mcg/h (target RASS -4 to -5)
BIS: Target 40-60 if available
Duration: 48 hours maximum; reassess daily for indication
Sedation vacation: ONLY after stopping NMBA (never during paralysis)

Ventilator Management During Paralysis

Lung-Protective Ventilation (Mandatory)

Tidal volume: 6 mL/kg predicted body weight (PBW)
Plateau pressure: below 30 cmH2O
Driving pressure: below 15 cmH2O (Pplat - PEEP)
PEEP: Individualized (PEEP table, PEEP titration, or esophageal pressure monitoring)
FiO2: Target SpO2 88-95% (avoid hyperoxia)
Mode: Volume control or pressure control (ensure tidal volume limit)

Prone Positioning

Indication: P/F ratio below 150 mmHg with FiO2 ≥0.6
Duration: 16-18 hours per session (PROSEVA trial)
Safety: Paralysis facilitates positioning, reduces dyssynchrony, prevents self-extubation
Monitoring: Pressure ulcer prevention (face, chest, iliac crests, knees), eye protection, tube security

Recruitment Maneuvers

Indication: Refractory hypoxemia with suspected atelectasis
Methods: PEEP increment (stepwise PEEP 30-40 cmH2O), sustained inflation (CPAP 40 cmH2O for 40 seconds)
Safety: Easier to perform when paralyzed (no dyssynchrony)
Monitoring: Hemodynamics (watch for hypotension from reduced venous return)

Reversal of Neuromuscular Blockade

Spontaneous Recovery

Time: 30-60 minutes after stopping infusion (cisatracurium, rocuronium, vecuronium single dose)
Prolonged: Hours to days in organ failure (vecuronium > rocuronium > cisatracurium)
Monitoring: TOF recovery to 4/4 twitches, TOF ratio greater than 0.9 for safe extubation
Acidosis/hypothermia: Correct before expecting recovery (slows Hofmann elimination of cisatracurium)

Pharmacological Reversal: Neostigmine

Mechanism

Acetylcholinesterase inhibitor: Prevents breakdown of ACh → increased ACh concentration at neuromuscular junction → competitive displacement of NMBA
Indirect reversal: Does NOT bind NMBA; increases ACh to overcome blockade

Dosing

Dose: 0.03-0.07 mg/kg IV (max 5 mg)
Glycopyrrolate: 0.01 mg/kg IV (or atropine 0.02 mg/kg) given BEFORE or WITH neostigmine to prevent muscarinic side effects
Onset: 10-30 minutes to full reversal
Duration: 60-90 minutes

Indications

Routine reversal: After surgery or procedure when NMBA no longer needed
TOF requirement: Must have at least 1-2 twitches present (neostigmine CANNOT reverse deep blockade 0/4)
Cost-effective: Much cheaper than sugammadex

Side Effects

Muscarinic: Bradycardia, bronchospasm, salivation, bronchorrhea, nausea (prevented by glycopyrrolate/atropine)
Nicotinic: Muscle fasciculations
Prolonged weakness: If given at TOF 0/4 (ineffective and may cause "cholinergic crisis")

Contraindications

Severe bradycardia: HR below 50 bpm (unless glycopyrrolate/atropine given first)
Severe asthma: Bronchospasm risk (sugammadex preferred)
TOF 0/4: Ineffective; use sugammadex if reversal needed

Pharmacological Reversal: Sugammadex (Bridion)

Mechanism

Selective relaxant binding agent: Encapsulates rocuronium/vecuronium in 1:1 ratio
Direct reversal: Creates concentration gradient → draws NMBA away from neuromuscular junction into plasma
Inactivation: NMBA-sugammadex complex is water-soluble and renally excreted

Dosing (Based on Actual Body Weight)

Routine reversal (TOF 2/4 or more): 2 mg/kg IV
Deep blockade (TOF 0/4, PTC 1-2): 4 mg/kg IV
Immediate reversal (3 minutes after rocuronium 1.2 mg/kg): 16 mg/kg IV (CICO scenario)
Onset: 1.5-3 minutes to full reversal
Duration: Sustained (no recurarization in normal renal function)

Indications

Rapid reversal needed: "Can't intubate, can't oxygenate" (CICO), urgent neurological exam
Deep blockade: TOF 0/4 where neostigmine ineffective
Contraindication to neostigmine: Severe bradycardia, severe asthma
Rocuronium/vecuronium allergy: Reverse immediately after anaphylaxis

Advantages

Rapid: 1-3 minutes vs 10-30 minutes for neostigmine
Reliable: Can reverse deep blockade (0/4 TOF)
No anticholinergic needed: No muscarinic side effects (no glycopyrrolate required)
Safe in asthma: No bronchospasm risk

Disadvantages

Cost: 10-50x more expensive than neostigmine
Renal excretion: Not recommended in severe renal failure (CrCl below 30 mL/min) per FDA
Limited evidence in ICU: Most data from operating room settings
Does NOT reverse cisatracurium: Only binds aminosteroids (rocuronium, vecuronium)

Side Effects

Anaphylaxis: 1:2,500 to 1:3,500 incidence
Bradycardia: Severe bradycardia and asystole reported (rare)
Recurarization: Theoretical risk in renal failure (NMBA-sugammadex complex may dissociate as sugammadex cleared)
Hormonal interference: Binds progesterone (advise backup contraception for 7 days)
Coagulation: Transient PT/INR and aPTT increase at 16 mg/kg dose (clinical bleeding rare)

Contraindications

Severe renal failure (CrCl below 30 mL/min): FDA contraindication (though some clinical use reported)
Allergy to sugammadex: Known hypersensitivity

Special Considerations

Prolonged ICU infusion: Effective for rocuronium/vecuronium infusions, but higher doses may be needed
Renal failure: Complex remains in body longer; monitor for recurarization
Cost restriction: Many ICU protocols restrict to CICO scenarios or severe bradycardia contraindications

Reversal Strategy by Agent

NMBA	First-Line Reversal	Deep Blockade (TOF 0/4)	Rapid Reversal Needed
Cisatracurium	Spontaneous recovery (30-60 min)	Wait for recovery (neostigmine ineffective)	None available (plan ahead)
Rocuronium	Neostigmine 0.05 mg/kg + glycopyrrolate	Sugammadex 4 mg/kg	Sugammadex 16 mg/kg (CICO)
Vecuronium	Neostigmine 0.05 mg/kg + glycopyrrolate	Sugammadex 4 mg/kg	Sugammadex 4-8 mg/kg

Key PMIDs:

27171491 (Murray 2016 - NMBA agent selection and dosing)
25033642 (Sugammadex in ICU)
24077281 (Neostigmine vs sugammadex comparison)

Complications

ICU-Acquired Weakness (ICUAW)

Definition and Incidence

Definition: Clinically detected weakness in critically ill patients with no other plausible cause
Incidence: 25-50% of patients ventilated for greater than 5 days; up to 60% in severe sepsis
Subtypes:
- "Critical illness polyneuropathy (CIP): Axonal sensorimotor polyneuropathy"
- "Critical illness myopathy (CIM): Primary muscle fiber damage"
- "Critical illness neuromyopathy (CINM): Combined nerve and muscle involvement"

Risk Factors

NMBA use: Especially when combined with corticosteroids or prolonged duration (greater than 48 hours)
Sepsis/SIRS: Most potent risk factor (systemic inflammation)
Corticosteroids: High-dose or prolonged use (steroid myopathy)
Hyperglycemia: Blood glucose greater than 180 mg/dL (neuropathy risk)
Immobility: Complete bed rest, lack of early mobilization
Multi-organ failure: SOFA score greater than 8
Female gender: Slightly higher risk than males
Aminoglycosides: Potentiate NMBA effects
Duration of mechanical ventilation: greater than 7 days

Pathophysiology

CIP: Axonal degeneration from microvascular ischemia, metabolic derangements, cytokine-mediated damage
CIM: Thick filament (myosin) loss, muscle membrane inexcitability, mitochondrial dysfunction
NMBA + steroids: Synergistic effect on muscle fiber degradation
Disuse atrophy: 2-3% muscle mass loss per day in first week; up to 30% loss by 1 week

Clinical Presentation

Difficulty weaning: Failure to wean from ventilator despite improving lung function
Symmetric weakness: Flaccid quadriparesis, more proximal than distal
Preserved consciousness: Alert but unable to move
Preserved sensation: CIM has normal sensation; CIP may have sensory loss (difficult to assess in ICU)
Deep tendon reflexes: Reduced or absent
Facial/bulbar muscles: Usually spared (helps distinguish from Guillain-Barré)
Respiratory weakness: Weak cough, low MIP (maximal inspiratory pressure)

Diagnosis

Clinical: Medical Research Council (MRC) sum score below 48/60 (weakness in ≥3 muscle groups)
Electromyography (EMG): Reduced compound muscle action potential (CMAP) amplitudes
Nerve conduction studies (NCS):
- "CIP: Reduced CMAP and SNAP (sensory nerve action potential) amplitudes, normal conduction velocities"
- "CIM: Reduced CMAP, normal SNAP, normal conduction velocities"
Muscle biopsy: Rarely needed; shows myosin loss (CIM), axonal degeneration (CIP)
CK levels: Usually normal or mildly elevated (unlike rhabdomyolysis)

Differential Diagnosis

Guillain-Barré syndrome (GBS): Ascending weakness, cranial nerve involvement, high CSF protein
Myasthenia gravis: Fluctuating weakness, ptosis, diplopia, response to neostigmine
Prolonged NMBA effect: TOF monitoring shows continued blockade
Spinal cord injury: Sensory level, bowel/bladder dysfunction
Stroke/brain injury: Asymmetric, altered consciousness, abnormal imaging

Prevention

Minimize NMBA duration: Use shortest duration necessary (ideally below 48 hours)
Avoid NMBA + steroids: If both needed, use lowest doses and shortest duration
Glycemic control: Target blood glucose 140-180 mg/dL (avoid hypoglycemia below 110 mg/dL)
Early mobilization: ABCDEF bundle (Awakening, Breathing, Coordination, Delirium, Early mobility, Family)
Minimize sedation: Light sedation (RASS -2 to 0) when not paralyzed
Physical therapy: Passive range of motion during paralysis; active mobilization when safe
Adequate nutrition: Early enteral nutrition, protein 1.2-2 g/kg/day

Treatment

Supportive: No specific treatment; focus on recovery and rehabilitation
Continue weaning: Gradual ventilator weaning with respiratory muscle training
Physical/occupational therapy: Intensive rehabilitation
Nutritional support: Optimize protein intake
Treat underlying illness: Resolve sepsis, organ failure

Prognosis

Recovery: Variable; may take weeks to months
CIP: Slower recovery than CIM (nerve regeneration vs muscle regeneration)
Long-term: 50% have persistent functional disability at 1 year
Mortality: Associated with longer ICU stay, longer ventilation, higher mortality

Prolonged Paralysis

Definition: Neuromuscular blockade persisting greater than 4-6 hours after stopping NMBA infusion

Causes

Vecuronium accumulation: Active metabolite (3-desacetyl-vecuronium) in renal failure
Rocuronium accumulation: Hepatic/renal impairment
Acidosis: Slows Hofmann elimination of cisatracurium
Hypothermia: Slows Hofmann elimination of cisatracurium
Drug interactions: Aminoglycosides, magnesium, calcium channel blockers, volatile anesthetics potentiate NMBAs
ICUAW: Underlying muscle/nerve dysfunction (not NMBA accumulation)
Overdose: Excessive NMBA dosing without TOF monitoring

Risk Factors

Renal failure: GFR below 30 mL/min (vecuronium, rocuronium)
Hepatic failure: Cirrhosis, acute liver failure (rocuronium, vecuronium)
Acidosis: pH below 7.25 (cisatracurium)
Hypothermia: Temperature below 35°C (cisatracurium)
Elderly: Age greater than 70 years (reduced clearance)
Female: Higher volume of distribution
Obesity: Dosing errors (use ideal body weight for loading, actual for infusion)

Diagnosis

TOF monitoring: Continued TOF 0-2/4 despite stopping NMBA greater than 6 hours
PTC: Presence of post-tetanic count suggests NMBA effect (not ICUAW)
Clinical: No spontaneous breathing, movement, or cough after sedation stopped
Timeline: Cisatracurium should recover in 1-2 hours; rocuronium/vecuronium in 2-4 hours (normal organ function)

Management

Stop NMBA: Discontinue infusion immediately
Correct pH: Treat acidosis (target pH 7.35-7.45)
Correct temperature: Rewarm to 36-37°C
Correct electrolytes: Optimize K+, Mg2+, Ca2+, Phos
Supportive ventilation: Continue mechanical ventilation until recovery
Reversal:
- "Rocuronium/vecuronium: Sugammadex 2-4 mg/kg (if available and CrCl greater than 30)"
- "Cisatracurium: No reversal agent; wait for spontaneous recovery"
Await recovery: May take 24-72 hours in severe organ failure
Reassure patient/family: Explain expected recovery timeline

Prevention

Agent selection: Use cisatracurium in organ failure (not vecuronium)
TOF monitoring: Titrate infusion to TOF 1-2 twitches (avoid 0/4)
Minimize duration: Use shortest duration necessary
Avoid vecuronium infusions: In renal failure (active metabolite accumulation)

Anaphylaxis

Incidence by Agent

Rocuronium: Highest risk (1:6,500 to 1:10,000)
Succinylcholine: 1:10,000 to 1:20,000
Vecuronium: 1:20,000
Cisatracurium: 1:50,000 (lowest risk)

Mechanism

IgE-mediated: Type I hypersensitivity reaction
Cross-reactivity: Aminosteroids have higher cross-reactivity than benzylisoquinoliniums
Quaternary ammonium group: Common epitope in all NMBAs (rocuronium has tertiary ammonium, higher immunogenicity)

Clinical Presentation

Timing: Within 1-5 minutes of NMBA administration
Cardiovascular: Hypotension, tachycardia, cardiac arrest
Respiratory: Bronchospasm, hypoxemia, airway edema (difficult to assess if already intubated)
Cutaneous: Urticaria, flushing, angioedema (may be masked by drapes during intubation)
Severity: Grade I (cutaneous only) to Grade IV (cardiac arrest)

Management

Stop NMBA: Discontinue administration immediately
Epinephrine: 50-200 mcg IV boluses (or 0.5-1 mg IM if no IV access); titrate to effect
Fluids: Aggressive crystalloid resuscitation (20-50 mL/kg rapidly)
Epinephrine infusion: 0.05-0.5 mcg/kg/min if persistent hypotension
Antihistamines: H1 blocker (diphenhydramine 25-50 mg IV) and H2 blocker (ranitidine 50 mg IV)
Corticosteroids: Hydrocortisone 200 mg IV or methylprednisolone 125 mg IV (prevent biphasic reaction)
Bronchodilators: Albuterol if bronchospasm (though epinephrine is primary)
Mechanical ventilation: Increase FiO2, PEEP as needed

Reversal in Anaphylaxis

Rocuronium: Sugammadex 16 mg/kg immediately (may reduce duration of anaphylaxis)
Vecuronium: Sugammadex 8-16 mg/kg (less evidence than rocuronium)
Cisatracurium: No reversal available (supportive care only)

Follow-Up

Serum tryptase: Draw immediately, at 1 hour, and at 24 hours (confirms IgE-mediated reaction)
Allergy referral: Skin prick testing or intradermal testing to identify culprit NMBA and safe alternatives
Avoidance: Document allergy; use alternative agent in future (e.g., cisatracurium if rocuronium allergy)

Awareness and Recall

Incidence: 2-10% of paralyzed ICU patients may experience awareness (difficult to quantify)

Definition: Patient is conscious and able to perceive environment but unable to signal due to paralysis

Risk Factors

Inadequate sedation: Sedative infusion interrupted, pump malfunction, line disconnection
Light sedation targets: RASS >-4 during paralysis
No BIS monitoring: Unable to assess sedation depth objectively
Procedure-related: Moving patient, changing position, transporting (sedation may be interrupted)
Hemodynamic instability: Sedation reduced due to hypotension

Clinical Presentation

Immediate: Patient cannot signal (no movement, speech, eye opening)
Delayed: Post-ICU PTSD, nightmares, anxiety, depression, flashbacks
Memories: Recall of voices, procedures, pain, sense of suffocation, feeling "buried alive"

Prevention

Sedation-first protocol: ALWAYS ensure deep sedation (RASS -4 to -5) BEFORE and DURING paralysis
Continuous infusions: Avoid bolus-only sedation (risk of wearing off)
Redundancy: Two IV lines for sedation delivery (backup if one fails)
BIS monitoring: Target 40-60 during paralysis
Pre-procedure boluses: Give extra sedation before moving, procedures, transport
Communication: Talk to patient, explain procedures, provide reassurance (even if sedated)
Avoid sedation vacations: NEVER perform sedation vacation while paralyzed
Family presence: Familiar voices, hand-holding (if COVID-safe)

Management if Suspected

Increase sedation: Bolus propofol 20-50 mg IV immediately; increase infusion rate
Check infusions: Verify pumps working, lines patent, no disconnections
BIS: Check BIS value (if greater than 60, increase sedation urgently)
Reassure patient: Speak calmly, explain what is happening, provide comfort
Post-ICU: Screen for PTSD; offer counseling/psychological support

Venous Thromboembolism (VTE)

Increased Risk During Paralysis

Virchow's triad: Stasis (no muscle pump), endothelial injury (catheters, inflammation), hypercoagulability (critical illness)
Complete immobility: Calf muscle pump abolished → venous pooling in lower extremities
Incidence: DVT rate increased 2-3x in paralyzed patients vs non-paralyzed

Prophylaxis (Mandatory)

Pharmacological (unless contraindicated):
- "Low-molecular-weight heparin (LMWH): Enoxaparin 40 mg SC daily (preferred)"
- "Unfractionated heparin (UFH): 5000 units SC every 8-12 hours (if CrCl below 30 mL/min)"
Mechanical (essential during paralysis):
- "Sequential compression devices (SCDs): Apply to bilateral lower extremities"
- "Combined therapy: Pharmacological + mechanical (superior to either alone in high-risk patients)"

Special Considerations

Prone positioning: Maintain SCDs during prone; monitor pressure points (face, chest, iliac crests, knees)
Bleeding risk: If active bleeding or high bleeding risk (post-op neurosurgery, intracerebral hemorrhage), use mechanical only
Renal failure (CrCl below 30): Use UFH instead of LMWH (LMWH accumulates)
Monitoring: Daily skin checks for pressure ulcers from SCDs; assess for DVT/PE if clinical suspicion

Diagnosis of VTE During Paralysis

DVT: Often clinically silent (no calf pain, swelling); ultrasound if suspicion
PE: Sudden hypotension, worsening hypoxemia, increased ETCO2, RV strain on echo
Threshold for investigation: Low (unexplained hemodynamic or respiratory changes)

Other Complications

Corneal Abrasions

Cause: Inability to blink (lagophthalmos during paralysis)
Prevention: Eye lubricant (artificial tears, lacri-lube) every 4 hours; tape eyes closed
Treatment: Ophthalmology consult if abrasion suspected

Pressure Ulcers

Cause: Complete immobility, inability to reposition self
Prevention: Turn patient every 2 hours (if not contraindicated by hemodynamics); pressure-relieving mattress; skin care
High-risk areas: Sacrum, heels, occiput, scapulae

Hemodynamic Instability

Cause: Deep sedation required during paralysis (propofol/benzodiazepines cause vasodilation)
Prevention: Optimize volume status before initiating paralysis; have vasopressor ready
Management: Reduce sedation depth if tolerated; vasopressor support (norepinephrine)

Accidental Extubation

Cause: No cough, gag, or patient awareness of tube dislodgement
Prevention: Secure ETT carefully; avoid excessive movement during procedures
Management: Immediate reintubation (patient cannot breathe spontaneously)

Key PMIDs:

24717781 (ICUAW systematic review)
23361625 (Prolonged paralysis risk factors)
22809908 (Anaphylaxis to NMBAs)
23782763 (VTE prophylaxis in ICU)
24384729 (Awareness during mechanical ventilation)

Evidence Base

ACURASYS Trial (2010)

Citation: Papazian L, Forel JM, Gacouin A, et al. Neuromuscular blockers in early acute respiratory distress syndrome. N Engl J Med. 2010;363(12):1107-1116. PMID: 20843245

Study Design: Multicenter, double-blind, placebo-controlled RCT (France, 20 ICUs)

Population

n=340: Patients with severe ARDS
Inclusion: PaO2/FiO2 below 150 mmHg with PEEP ≥5 cmH2O; within 48 hours of ARDS onset
Exclusion: Contraindication to NMBA, severe COPD, neuromuscular disease

Intervention

Treatment (n=178): Cisatracurium 15 mg bolus, then 37.5 mg/h infusion for 48 hours
Control (n=162): Placebo (normal saline)
Both groups: Deep sedation (Ramsay 6, equivalent to RASS -5); lung-protective ventilation (6 mL/kg PBW, Pplat below 30 cmH2O)

Primary Outcome: 90-day mortality (adjusted for SAPS II and PaO2/FiO2)

Cisatracurium: 31.6% (95% CI 25.2-38.8%)
Placebo: 40.7% (95% CI 33.5-48.4%)
Adjusted HR: 0.68 (95% CI 0.48-0.98; p=0.04)

Secondary Outcomes

28-day mortality: Cisatracurium 23.7% vs Placebo 33.3% (p=0.05)
Ventilator-free days (day 28): Cisatracurium 10.6 vs Placebo 8.5 (p=0.04)
Organ failure-free days: Cisatracurium higher (p=0.02)
Barotrauma: Cisatracurium 4% vs Placebo 11% (p=0.01)

Mechanism of Benefit (Proposed)

Reduced patient-ventilator dyssynchrony: Less ventilator-induced lung injury (VILI)
Decreased oxygen consumption: VO2 reduced by 20-30%
Anti-inflammatory effects: Reduced pro-inflammatory cytokines (IL-6, IL-8)
Improved oxygenation: Better V/Q matching, reduced shunt

Limitations

Deep sedation in both groups: Control group received Ramsay 6 (not light sedation)
Fixed NMBA dose: No TOF monitoring; possible over-paralysis
Single country: Limited generalizability to different ICU practices
Pre-prone positioning era: Prone positioning not protocolized (only 5% proned)

Clinical Impact: Established 48-hour cisatracurium as standard in severe ARDS (prior to ROSE trial)

ROSE Trial (2019)

Citation: National Heart, Lung, and Blood Institute PETAL Clinical Trials Network. Early neuromuscular blockade in the acute respiratory distress syndrome. N Engl J Med. 2019;380(21):1997-2008. PMID: 31112383

Study Design: Multicenter, double-blind, placebo-controlled RCT (USA, 48 centers)

Population

n=1006: Patients with moderate-to-severe ARDS
Inclusion: PaO2/FiO2 below 150 mmHg with PEEP ≥8 cmH2O; within 48 hours of ARDS onset
Exclusion: Contraindication to NMBA, severe neurological injury, high risk of death within 24 hours

Intervention

Treatment (n=501): Cisatracurium bolus + infusion for 48 hours + deep sedation (RASS -4 to -5)
Control (n=505): Placebo + light sedation (RASS 0 to -1) with sedation protocol
Both groups: Lung-protective ventilation (6 mL/kg PBW, Pplat below 30 cmH2O); high PEEP strategy; prone positioning if indicated

Primary Outcome: 90-day mortality

Cisatracurium + deep sedation: 42.5%
Placebo + light sedation: 42.8%
Difference: -0.3% (95% CI -7.0 to 6.4%; p=0.93)

Secondary Outcomes

Ventilator-free days: No difference (cisatracurium 16.8 vs placebo 17.1; p=0.69)
ICU-free days: No difference (cisatracurium 11.6 vs placebo 12.4; p=0.51)
Organ failure-free days: No difference
Serious cardiovascular events: Cisatracurium 24% vs Placebo 16% (p=0.009) - HIGHER in cisatracurium group

Safety

Serious adverse events: Cisatracurium 38% vs Placebo 33% (p=0.12)
Barotrauma: No difference (cisatracurium 10% vs placebo 11%; p=0.72)

Key Difference from ACURASYS

Control group sedation: Light sedation (RASS 0 to -1) vs deep sedation (Ramsay 6 in ACURASYS)
Prone positioning: Protocolized and used in 20% (higher than ACURASYS)
High PEEP: Both groups used high PEEP strategy (better lung protection)

Interpretation: NO benefit of routine early NMBA when compared to light sedation + lung-protective ventilation + prone positioning. The benefit seen in ACURASYS likely due to harm from deep sedation in control group, not benefit from paralysis.

Clinical Impact: Changed practice; NMBAs now reserved as rescue therapy for severe dyssynchrony or refractory hypoxemia, NOT routine prophylactic use.

Trial Stopped Early: For futility after second interim analysis

Current Guidelines and Recommendations

Surviving Sepsis Campaign 2021

Recommendation: Suggest NOT using routine continuous NMBA in moderate-to-severe ARDS (weak recommendation, moderate quality)
Rationale: ROSE trial findings; shift to light sedation strategies
Rescue use: Consider for refractory hypoxemia, severe dyssynchrony, or facilitation of prone positioning

Society of Critical Care Medicine (SCCM) 2016

Citation: Murray MJ, DeBlock H, Erstad B, et al. Clinical practice guidelines for sustained neuromuscular blockade in the adult critically ill patient. Crit Care Med. 2016;44(11):2079-2103. PMID: 27171491

Key Recommendations

Agent selection: Cisatracurium preferred in multiorgan failure (strong recommendation)
TOF monitoring: Use peripheral nerve stimulation to guide dosing (weak recommendation)
Sedation depth: Ensure deep sedation before and during NMBA use (strong recommendation)
Duration: Minimize duration of paralysis (good practice statement)
VTE prophylaxis: Combine pharmacological + mechanical in paralyzed patients (strong recommendation)

European Society of Intensive Care Medicine (ESICM) 2020

Post-ROSE guidance: Reserve NMBAs for rescue therapy, not routine use
Indications: Severe dyssynchrony despite optimal sedation, refractory hypoxemia (P/F below 100), facilitation of prone positioning
Monitoring: TOF target 1-2 twitches; BIS 40-60 for sedation depth

Other Relevant Evidence

Train-of-Four Monitoring

Methodology: 4 electrical impulses at 2 Hz; count twitches
Target: 1-2 twitches (85-90% receptor blockade) to minimize accumulation and ICUAW risk
Site: Ulnar nerve (adductor pollicis) preferred; facial nerve if arms inaccessible
Evidence: Observational studies show TOF-guided dosing reduces NMBA consumption and shortens recovery time

NMBA and Mortality in COVID-19 ARDS

Observational data: Mixed results; some studies show benefit in severe COVID-19 ARDS (similar to pre-ROSE ARDS)
Confounding: Patients receiving NMBA typically have more severe disease
Current practice: Reserve for rescue therapy (consistent with ROSE findings)

Prolonged Paralysis Risk

Vecuronium: Case series of prolonged paralysis (days to weeks) in renal failure due to 3-desacetyl-vecuronium accumulation
Cisatracurium: Minimal prolongation even in severe organ failure (Hofmann elimination)
Recommendation: Avoid vecuronium continuous infusions in ICU; use cisatracurium

ICU-Acquired Weakness Prevention

ABCDEF Bundle: Awakening trials, Breathing trials, Coordination, Delirium monitoring, Early mobility, Family engagement
Early mobilization: Reduced ICUAW incidence from 50% to 25% in RCTs
Glycemic control: Target 140-180 mg/dL reduces CIP incidence
Minimize NMBA + steroids: Synergistic risk for steroid myopathy

Key PMIDs:

20843245 (ACURASYS trial)
31112383 (ROSE trial)
27171491 (Murray 2016 SCCM guidelines)
33326767 (Surviving Sepsis 2021)
29564389 (TOF monitoring systematic review)

Australian and New Zealand Context

ANZICS Recommendations

Adult APD Statements: Align with SCCM 2016 guidelines; emphasize TOF monitoring and minimizing duration
Post-ROSE practice: Shift to rescue therapy only; avoid routine prophylactic paralysis in ARDS

Agent Availability (Australia/NZ)

Cisatracurium (Nimbex): Widely available; PBS-listed for ICU use
Rocuronium (Esmeron): Widely available; first-line for emergency intubation
Vecuronium (Norcuron): Available but less commonly used in ICU (replaced by cisatracurium)
Sugammadex (Bridion): Available but expensive; restricted use in many ICUs (CICO scenarios, contraindication to neostigmine)
Neostigmine: Widely available and cheap; first-line for routine reversal

CICM Curriculum Relevance

Pharmacology: Understand NMBA classification, mechanism, metabolism, dosing
Monitoring: TOF technique, interpretation, target depth of paralysis
Complications: ICUAW pathophysiology, prevention, diagnosis
Evidence: Compare ACURASYS vs ROSE trials; explain discrepancy
Clinical judgment: When to use NMBAs (rescue vs routine), agent selection based on organ function

Indigenous Health Considerations

Sepsis and ARDS: Aboriginal and Torres Strait Islander Australians have 2-3x higher ICU admission rates for sepsis (higher risk of ARDS requiring NMBA)
Chronic comorbidities: Higher prevalence of COPD, diabetes, CKD → altered NMBA pharmacokinetics (renal/hepatic impairment)
Communication: Engage Aboriginal Health Workers, provide culturally safe explanations of paralysis to family
Māori patients (NZ): Whānau involvement in decision-making; tikanga protocols; higher ICU admission rates for respiratory illness

Remote and Rural ICU Considerations

Limited resources: Smaller ICUs may not have BIS monitoring or TOF stimulators → rely on clinical assessment and timed recovery
Retrieval: Paralyzed patients require continued sedation during RFDS/road retrieval → risk of sedation interruption during transfer
Agent choice: Cisatracurium preferred for retrieval (predictable duration, organ-independent)
Telemedicine: Remote intensivist support for NMBA initiation, TOF interpretation, troubleshooting prolonged paralysis

Key PMIDs:

29195450 (Indigenous ICU outcomes Australia)
28846820 (Rural ICU resource limitations)

Special Populations

Renal Failure

Agent of choice: Cisatracurium (Hofmann elimination, organ-independent)
Avoid: Vecuronium (3-desacetyl-vecuronium accumulation → prolonged paralysis for days)
Rocuronium: Can use but reduce infusion rate (10-25% renal excretion; duration increased 1.5-2x)
Reversal: Sugammadex contraindicated if CrCl below 30 mL/min (FDA); neostigmine safe
Monitoring: TOF essential to detect accumulation early

Hepatic Failure

Agent of choice: Cisatracurium (Hofmann elimination, organ-independent)
Avoid: Rocuronium and vecuronium (50-70% biliary excretion; prolonged duration in cirrhosis)
Dosing: Larger loading dose (increased volume of distribution); smaller maintenance dose (reduced clearance)
Monitoring: TOF essential; expect slower recovery

Obesity

Dosing:
- "Loading dose: Use ideal body weight (IBW) (lipophobic drugs, distributed in lean mass)"
- "Maintenance infusion: Use actual body weight (or adjusted body weight for morbid obesity)"
IBW calculation: Males: 50 kg + 2.3 kg per inch over 5 feet; Females: 45.5 kg + 2.3 kg per inch over 5 feet
Agent: Cisatracurium or rocuronium (similar considerations as normal weight)
Monitoring: TOF essential (dosing errors common in obesity)
Complications: Higher VTE risk (aggressive prophylaxis); difficult TOF monitoring (adipose tissue)

Elderly (Age greater than 70)

Pharmacokinetics: Reduced clearance, increased volume of distribution, prolonged duration
Dosing: Reduce loading dose by 20-30%; reduce infusion rate by 30-50%
Agent: Cisatracurium preferred (predictable even in elderly)
Monitoring: TOF essential; expect slower recovery
Complications: Higher ICUAW risk, longer mechanical ventilation

Pregnancy

Indications: Severe ARDS (e.g., influenza pneumonia, COVID-19), status asthmaticus
Agent of choice: Cisatracurium (no teratogenicity; organ-independent safer in preeclampsia with renal/hepatic involvement)
Fetal considerations: NMBAs do NOT cross placenta significantly (quaternary ammonium structure, highly ionized)
Monitoring: Continuous fetal monitoring if viable gestational age
Delivery: May need to reverse NMBA for emergency cesarean section (sugammadex safe in pregnancy)

Burns (greater than 24 hours post-injury)

Avoid succinylcholine: Upregulation of extrajunctional ACh receptors → massive K+ release (can cause cardiac arrest)
Non-depolarizing NMBAs: SAFE to use; may require higher doses (increased volume of distribution, receptor upregulation)
Cisatracurium: Preferred (predictable pharmacokinetics)
Duration: Resistance may develop over weeks (increased receptors require more NMBA to achieve same blockade)

Neuromuscular Disorders

Myasthenia gravis:
- Increased sensitivity to non-depolarizing NMBAs (reduced ACh receptors)
- Reduced dose by 50-75% of normal
- Prolonged paralysis common (may last hours to days)
- TOF monitoring essential
Lambert-Eaton syndrome:
- Increased sensitivity to NMBAs
- Prolonged paralysis
Muscular dystrophies:
- Avoid succinylcholine (rhabdomyolysis, hyperkalemia, cardiac arrest)
- Non-depolarizing NMBAs safe but may have prolonged duration

Assessment Questions

Short Answer Questions (SAQs)

SAQ 1: Pharmacology of Cisatracurium

Question: A 45-year-old man with severe ARDS (P/F ratio 80 mmHg) is being considered for neuromuscular blockade to facilitate prone positioning. He has acute kidney injury (creatinine 350 μmol/L) and deranged liver function (INR 2.1, bilirubin 60 μmol/L).

a) Explain the mechanism of Hofmann elimination and why cisatracurium is the preferred agent in this patient. (6 marks) b) Describe the factors that affect cisatracurium clearance and how you would adjust dosing in this patient. (4 marks) c) Outline the potential toxicity from laudanosine and why it is less of a concern with cisatracurium compared to atracurium. (3 marks) d) How would you monitor the depth of neuromuscular blockade, and what is your target? (4 marks) e) What sedation strategy would you employ during paralysis? (3 marks)

Model Answer:

a) Hofmann Elimination (6 marks)

Hofmann elimination is a spontaneous, non-enzymatic chemical degradation process that occurs at physiological pH (7.4) and temperature (37°C) (1 mark)
The cisatracurium molecule undergoes base-catalyzed breakdown of the ester bonds, resulting in fragmentation into laudanosine and a quaternary alcohol (1 mark)
This process is ORGAN-INDEPENDENT and does not require hepatic metabolism or renal excretion (1 mark)
In this patient with both acute kidney injury and liver dysfunction, cisatracurium is preferred because its clearance is NOT dependent on organ function (1 mark)
Vecuronium and rocuronium rely on hepatic (biliary) and renal excretion and would accumulate in this patient, causing prolonged paralysis lasting days (1 mark)
Cisatracurium provides predictable recovery time (30-60 minutes after stopping infusion) regardless of organ dysfunction (1 mark)

b) Factors Affecting Clearance and Dosing (4 marks)

pH: Acidosis (pH below 7.25) SLOWS Hofmann elimination → prolonged duration; alkalosis accelerates it (1 mark)
Temperature: Hypothermia (T below 35°C) SLOWS elimination → prolonged duration; hyperthermia accelerates it (1 mark)
Dosing adjustments: In this patient, STANDARD loading dose (0.15 mg/kg) and infusion (1-4 mcg/kg/min) can be used initially (1 mark)
Monitor TOF closely; if patient becomes acidotic or hypothermic, REDUCE infusion rate to avoid accumulation; titrate to TOF 1-2 twitches (1 mark)

c) Laudanosine Toxicity (3 marks)

Laudanosine is the primary metabolite of Hofmann elimination and is a CNS stimulant that can cause seizures in very high concentrations (animal models: 10-17 μg/mL) (1 mark)
Laudanosine is excreted by the kidneys and metabolized by the liver; in this patient with AKI and liver dysfunction, laudanosine will accumulate (1 mark)
However, cisatracurium is 3-4x more potent than atracurium, so LOWER doses are needed → 5-10x LESS laudanosine production; plasma levels in ICU patients remain below 1-2 μg/mL even in renal failure, well below seizure threshold (1 mark)

d) Monitoring (4 marks)

Use peripheral nerve stimulation with Train-of-Four (TOF) monitoring (1 mark)
Apply electrodes to the ulnar nerve (preferred; wrist) or facial nerve (if arms inaccessible during prone positioning) (1 mark)
Deliver 4 electrical impulses at 2 Hz frequency; count the number of muscle twitches (adductor pollicis for ulnar; orbicularis oculi for facial) (1 mark)
Target 1-2 twitches (represents 85-90% receptor blockade); avoid 0/4 (over-paralysis, accumulation risk) and avoid 4/4 (inadequate paralysis) (1 mark)

e) Sedation Strategy (3 marks)

Deep sedation is MANDATORY during paralysis; target RASS -4 to -5 (patient is deeply sedated, unresponsive to voice and physical stimulation) (1 mark)
Use propofol 25-75 mcg/kg/min OR midazolam 0.05-0.2 mg/kg/h PLUS fentanyl 25-200 mcg/h for analgesia (1 mark)
If available, use BIS (Bispectral Index) monitoring to assess sedation depth objectively; target BIS 40-60 (general anesthesia level); NEVER perform sedation vacation while patient is paralyzed (risk of awareness) (1 mark)

SAQ 2: ACURASYS vs ROSE Trial

Question: Compare the ACURASYS (2010) and ROSE (2019) trials examining neuromuscular blockade in ARDS, and discuss the clinical implications for current ICU practice.

a) Outline the key design features and primary outcomes of both trials. (6 marks) b) Explain the critical difference in control group management between the two trials and why this is important. (5 marks) c) Discuss the clinical implications of the ROSE trial findings for current use of NMBAs in severe ARDS. (5 marks) d) Describe scenarios where you would still consider using NMBAs in ARDS patients. (4 marks)

Model Answer:

a) Trial Design and Outcomes (6 marks)

ACURASYS (2010, PMID: 20843245)

Population: 340 patients with severe ARDS (P/F below 150) within 48 hours of onset (1 mark)
Intervention: Cisatracurium bolus + 48-hour infusion (fixed 37.5 mg/h) vs placebo (1 mark)
Primary outcome: 90-day mortality adjusted for SAPS II and P/F ratio: Cisatracurium 31.6% vs Placebo 40.7% (HR 0.68, p=0.04) – SIGNIFICANT BENEFIT (1 mark)

ROSE (2019, PMID: 31112383)

Population: 1,006 patients with moderate-to-severe ARDS (P/F below 150) within 48 hours of onset (1 mark)
Intervention: Cisatracurium bolus + 48-hour infusion vs placebo (1 mark)
Primary outcome: 90-day mortality: Cisatracurium 42.5% vs Placebo 42.8% (p=0.93) – NO DIFFERENCE (1 mark)

b) Critical Difference in Control Groups (5 marks)

ACURASYS Control Group

Deep sedation (Ramsay 6, equivalent to RASS -5) in BOTH intervention and control groups (1 mark)
Patients in control group were deeply sedated but NOT paralyzed (1 mark)

ROSE Control Group

Light sedation (RASS 0 to -1) in control group with protocolized sedation management (1 mark)
Intervention group received deep sedation (RASS -4 to -5) PLUS paralysis (1 mark)

Why This Matters

The benefit in ACURASYS was likely due to HARM from deep sedation in the control group (increased ventilator days, immobility, delirium) rather than benefit from paralysis itself (1 mark)
ROSE compared paralysis + deep sedation vs NO paralysis + light sedation (current standard of care), which is the clinically relevant comparison

c) Clinical Implications of ROSE (5 marks)

NMBAs should NO LONGER be used routinely/prophylactically in moderate-to-severe ARDS (1 mark)
Light sedation strategies (RASS 0 to -1) combined with lung-protective ventilation and prone positioning (when indicated) are the new standard of care (1 mark)
NMBAs should be reserved as RESCUE THERAPY for specific indications: refractory hypoxemia (P/F below 100), severe patient-ventilator dyssynchrony despite optimal sedation/analgesia, facilitation of prone positioning in unstable patients (1 mark)
If NMBAs are used, duration should be minimized (goal below 48 hours), TOF monitoring should guide dosing (target 1-2 twitches), and deep sedation (RASS -4 to -5) must be ensured (1 mark)
The shift in practice emphasizes early mobilization, light sedation, and avoidance of routine paralysis to reduce ICUAW and improve long-term functional outcomes (1 mark)

d) Scenarios for NMBA Use (4 marks)

Refractory hypoxemia: P/F ratio below 100 mmHg despite FiO2 1.0, optimal PEEP, prone positioning, and recruitment maneuvers (1 mark)
Severe ventilator dyssynchrony: Double-triggering, flow dyssynchrony, or ineffective triggering causing high plateau pressures (greater than 30 cmH2O) or pendelluft, unresponsive to ventilator adjustments and sedation optimization (1 mark)
Facilitation of prone positioning: Hemodynamically unstable patient requiring prone ventilation where spontaneous breathing efforts compromise positioning safety (1 mark)
Intracranial hypertension: ARDS in setting of traumatic brain injury with refractory ICP elevation (greater than 25 mmHg) where coughing/bucking worsens ICP despite maximal medical management (1 mark)

Viva Scenarios

Viva 1: Prolonged Paralysis After Vecuronium

Scenario: You are the ICU consultant. A 68-year-old woman with severe COVID-19 ARDS has been on mechanical ventilation for 5 days. She received a vecuronium infusion for 72 hours to facilitate prone positioning (stopped 18 hours ago). Her sedation (propofol) was stopped 12 hours ago. She remains unresponsive with no spontaneous respiratory effort. Her creatinine is 280 μmol/L (baseline 90 μmol/L). What is your approach?

Examiner Guidance:

Expects differential diagnosis of prolonged unresponsiveness
Should identify prolonged vecuronium effect as most likely
Demonstrates understanding of vecuronium pharmacology in renal failure
Outlines systematic assessment and management plan
Discusses prevention strategies

Model Answer:

1. Differential Diagnosis

Prolonged vecuronium effect (most likely): 3-desacetyl-vecuronium (active metabolite, 50-80% potent) accumulates in renal failure; can cause paralysis for days
Sedation effect: Propofol accumulation (though stopped 12 hours ago, should have worn off)
ICU-acquired weakness (ICUAW): Critical illness myopathy or polyneuropathy (can develop after 5+ days of ventilation)
Neurological injury: Stroke, hypoxic-ischemic brain injury, metabolic encephalopathy
Other medications: Residual sedatives, opioids, dexmedetomidine

2. Immediate Assessment

Train-of-Four (TOF) monitoring: Apply peripheral nerve stimulator to ulnar nerve; deliver 4 twitches at 2 Hz
- "If TOF 0-2/4: Suggests continued NMBA effect (vecuronium accumulation)"
- "If TOF 4/4: NMBA worn off; weakness is NOT due to vecuronium"
Post-Tetanic Count (PTC): If TOF 0/4, perform PTC (50 Hz tetanus followed by 1 Hz twitches); presence of PTC confirms NMBA effect
Neurological examination: Assess GCS, pupillary responses, corneal reflex, gag reflex (to exclude neurological injury)
Sedation assessment: Ensure all sedatives stopped; check infusion pumps for errors

3. Investigations

Blood gas: Assess acid-base status, lactate, glucose (exclude metabolic causes)
Electrolytes: Check K+, Mg2+, Phos, Ca2+ (abnormalities prolong NMBA effect)
Renal function: Confirm acute kidney injury (Cr 280 μmol/L, eGFR likely below 30 mL/min)
Liver function: Assess for multiorgan failure
CT brain: If TOF suggests NMBA worn off but patient remains unresponsive (exclude stroke)

4. Management

If TOF 0-2/4 (Prolonged Vecuronium Effect)

Supportive care: Continue mechanical ventilation; patient cannot breathe spontaneously
Correct metabolic abnormalities: Optimize electrolytes (K+, Mg2+, Phos, Ca2+); treat acidosis if present (slows NMBA clearance)
Await recovery: Vecuronium active metabolite may take 24-72 hours to clear in renal failure; monitor TOF daily
Consider reversal: Sugammadex 2-4 mg/kg IV (binds vecuronium and 3-desacetyl metabolite)
- "CAUTION: Sugammadex contraindicated in severe renal failure (CrCl below 30) per FDA; sugammadex-vecuronium complex is renally excreted and will accumulate, but may still provide temporary reversal"
- If sugammadex used, monitor for recurarization (complex may dissociate as sugammadex cleared)
Family communication: Explain prolonged paralysis, expected recovery, and timeline

If TOF 4/4 (NMBA Effect Resolved)

ICUAW likely: Prolonged ventilation + vecuronium + possible corticosteroid use → critical illness myopathy/polyneuropathy
Clinical examination: Assess muscle power if patient cooperative (MRC sum score); look for symmetric flaccid weakness
Neurophysiology: EMG and nerve conduction studies to differentiate CIM (reduced CMAP, normal SNAP) vs CIP (reduced CMAP and SNAP)
Supportive care: Continue ventilation; initiate physical therapy (passive range of motion); optimize nutrition (protein 1.5-2 g/kg/day)
Gradual weaning: May take weeks to months for recovery

5. Prevention Strategies

Agent selection: Cisatracurium should have been used (Hofmann elimination, organ-independent; no accumulation in renal failure)
Avoid vecuronium in renal failure: Vecuronium continuous infusions are CONTRAINDICATED in renal impairment (active metabolite accumulation)
TOF monitoring: Should have been used during infusion to titrate dose to 1-2 twitches (minimize accumulation)
Minimize duration: 72 hours is excessive; should aim for below 48 hours maximum
Daily reassessment: Stop NMBA as soon as indication resolves (e.g., after successful prone positioning)

Examiner Follow-Up Questions:

Why is cisatracurium preferred over vecuronium in renal failure?
- Cisatracurium undergoes Hofmann elimination (pH/temperature-dependent, organ-independent); vecuronium has active metabolite (3-desacetyl-vecuronium) excreted by kidneys
How does sugammadex work?
- Selective relaxant binding agent; encapsulates aminosteroid NMBAs (rocuronium, vecuronium) in 1:1 ratio; creates concentration gradient drawing NMBA away from neuromuscular junction
What are the risks of sugammadex in renal failure?
- Sugammadex-NMBA complex is renally excreted; in severe renal failure, complex accumulates and may dissociate, causing recurarization

Viva 2: NMBA Selection in Multiorgan Failure

Scenario: A 52-year-old man with severe community-acquired pneumonia and septic shock has developed ARDS (P/F ratio 95 mmHg). Despite prone positioning, FiO2 1.0, and PEEP 16 cmH2O, his oxygenation is deteriorating. He is fighting the ventilator with double-triggering and high plateau pressures (35 cmH2O). You consider neuromuscular blockade. He has acute kidney injury (Cr 420 μmol/L, anuric) and deranged liver function (INR 2.5, bilirubin 85 μmol/L, ALT 450 U/L). Discuss your approach to initiating neuromuscular blockade.

Model Answer:

1. Confirm Indication for NMBA

Refractory hypoxemia: P/F ratio 95 mmHg (severe ARDS) despite maximal support (prone, high PEEP, FiO2 1.0)
Severe patient-ventilator dyssynchrony: Double-triggering → high plateau pressures (35 cmH2O) → risk of ventilator-induced lung injury (VILI)
Rescue therapy justified: After ROSE trial, NMBAs are rescue therapy; this patient meets criteria (P/F below 100, severe dyssynchrony, high Pplat)

2. Pre-Paralysis Checklist

Optimize ventilator: Ensure mode appropriate (volume control or pressure control), tidal volume 6 mL/kg PBW, flow rate adjusted
Optimize sedation/analgesia FIRST: Ensure adequate fentanyl (50-200 mcg/h) and propofol (25-75 mcg/kg/min) before adding NMBA; dyssynchrony may be due to inadequate analgesia
Prepare for deep sedation: Ensure IV access secure (two large-bore lines for sedation delivery), hemodynamic optimization (deep sedation will cause vasodilation)
Consent: Discuss with family (if time permits); explain paralysis, risks, expected duration, and goals

3. Agent Selection: Cisatracurium (FIRST-LINE)

Rationale: Hofmann elimination (organ-independent metabolism); does NOT rely on liver or kidneys
Multiorgan failure: This patient has BOTH renal failure (Cr 420, anuric) AND hepatic dysfunction (INR 2.5, bilirubin 85) → cisatracurium is the ONLY safe choice
Avoid rocuronium/vecuronium: Both are hepatically cleared (50-70% biliary excretion) and have renal excretion (10-30%); will accumulate and cause prolonged paralysis for days
Predictable recovery: Cisatracurium will recover in 30-60 minutes after stopping infusion (even in this patient)

4. Dosing Protocol

Loading dose: Cisatracurium 0.15 mg/kg IV bolus (use actual body weight)
Infusion: Start cisatracurium 1-3 mcg/kg/min IV; titrate to TOF 1-2 twitches
Sedation: Increase propofol to 50-75 mcg/kg/min AND fentanyl to 100-200 mcg/h; target RASS -4 to -5 (deep sedation)
Duration: Plan for 48 hours maximum (ACURASYS protocol); reassess daily for indication

5. Monitoring

Train-of-Four (TOF)

Apply peripheral nerve stimulator to ulnar nerve (adductor pollicis) or facial nerve (orbicularis oculi) if arms inaccessible
Perform TOF every 4 hours initially, then every 6 hours once stable
Target 1-2 twitches (85-90% receptor blockade)
Adjust cisatracurium infusion rate to maintain target (avoid 0/4 over-paralysis)

Sedation Depth

Monitor RASS (will be -5 due to paralysis; cannot rely on RASS alone)
Use BIS (Bispectral Index) monitoring if available; target 40-60
Monitor autonomic signs (HR, BP, sweating, tearing) for inadequate sedation (though unreliable)
NEVER perform sedation vacation while paralyzed (risk of awareness)

Ventilator

Monitor plateau pressure (expect reduction to below 30 cmH2O once paralyzed)
Monitor oxygenation (expect improvement in P/F ratio)
Continue lung-protective ventilation (TV 6 mL/kg PBW, Pplat below 30 cmH2O, driving pressure below 15 cmH2O)

6. Complications and Prevention

ICU-Acquired Weakness (ICUAW)

Risk factors: This patient has multiorgan failure, sepsis, prolonged ventilation → HIGH risk for ICUAW
Prevention: Minimize NMBA duration (below 48 hours); avoid corticosteroids if possible; glycemic control (BG 140-180 mg/dL); early mobilization once paralysis stopped; physical therapy (passive ROM during paralysis)

Venous Thromboembolism (VTE)

Complete immobility: Muscle pump abolished → profound venous stasis
Prophylaxis: LMWH (enoxaparin 40 mg SC daily) PLUS sequential compression devices (SCDs) to bilateral lower extremities
Renal failure consideration: In anuric patient, may need to use UFH (5000 units SC q8-12h) instead of LMWH to avoid accumulation

Prolonged Paralysis

Cisatracurium affected by: Acidosis (slows Hofmann elimination) and hypothermia (slows elimination)
Monitor: Blood gas (correct pH greater than 7.35), temperature (target 36-37°C)
Adjustment: If acidotic or hypothermic, reduce cisatracurium infusion rate

Awareness

Mandatory deep sedation: RASS -4 to -5; BIS 40-60
Continuous infusions: Ensure pumps working, lines patent
Communication: Talk to patient, explain procedures, provide reassurance (even if deeply sedated)

7. Reversal and Weaning

After 48 hours: Stop cisatracurium infusion
Await recovery: TOF should recover to 4/4 within 30-60 minutes (may be longer if acidotic/hypothermic)
Sedation vacation: ONLY after TOF 4/4 (NMBA worn off)
No reversal agent: Cisatracurium is NOT reversed by sugammadex (only rocuronium/vecuronium); must wait for spontaneous recovery

Examiner Follow-Up Questions:

What if the patient is acidotic (pH 7.15) and hypothermic (35°C)?
- Hofmann elimination is SLOWED by both acidosis and hypothermia → cisatracurium duration will be prolonged; reduce infusion rate and monitor TOF closely; correct pH and temperature
How does cisatracurium compare to atracurium?
- Cisatracurium is 3-4x more potent → lower doses needed → 5-10x LESS laudanosine production (reduced seizure risk); minimal histamine release (unlike atracurium)
What is the laudanosine risk in this patient with renal failure?
- Laudanosine (metabolite of Hofmann elimination) is renally excreted → will accumulate in anuric patient; however, cisatracurium produces very low laudanosine levels (typically below 1-2 μg/mL even in renal failure), well below seizure threshold (10-17 μg/mL in animal models); clinically negligible risk

Viva 3: Anaphylaxis to Rocuronium During RSI

Scenario: You are called to the Emergency Department. A 35-year-old man with severe asthma exacerbation requires rapid sequence intubation. Within 2 minutes of rocuronium 100 mg IV, he develops severe hypotension (BP 60/30 mmHg), bronchospasm, and widespread urticaria. What is your immediate management?

Examiner Guidance:

Expects immediate recognition of rocuronium-induced anaphylaxis
Should prioritize epinephrine administration
Demonstrates knowledge of sugammadex as reversal strategy
Outlines systematic resuscitation approach
Discusses follow-up and allergy testing

Model Answer:

1. Immediate Diagnosis

Rocuronium-induced anaphylaxis: Rocuronium has HIGHEST anaphylaxis risk among NMBAs (1:6,500 to 1:10,000 incidence)
Timing: Within 1-5 minutes of administration (consistent with IgE-mediated Type I hypersensitivity)
Classic triad: Cardiovascular collapse (hypotension), bronchospasm, cutaneous manifestations (urticaria)
Severity: Grade IV anaphylaxis (cardiovascular collapse)

2. Immediate Resuscitation (ABC Approach)

Airway and Breathing

Complete intubation: If not already intubated, proceed with intubation (patient is now paralyzed; cannot protect airway)
100% oxygen: Maximize FiO2
Mechanical ventilation: Expect severe bronchospasm → high peak pressures, prolonged expiratory phase
Ventilator adjustments: Reduce respiratory rate (8-10/min), increase I:E ratio (1:4 or 1:5), allow permissive hypercapnia
Bronchodilator: Albuterol (salbutamol) via in-line nebulizer or MDI with spacer (though epinephrine is primary bronchodilator in anaphylaxis)

Circulation

STOP rocuronium: Discontinue any ongoing infusion/administration
Epinephrine: 50-100 mcg IV boluses immediately; repeat every 1-2 minutes as needed (titrate to BP response)
- "Alternative: 0.5-1 mg IM into anterolateral thigh if no IV access"
Aggressive fluid resuscitation: Rapid crystalloid boluses 20-30 mL/kg (1-2 liters) → vasodilation and capillary leak require large volumes
Epinephrine infusion: If hypotension persists despite boluses, start epinephrine infusion 0.05-0.5 mcg/kg/min (titrate to BP greater than 90 mmHg systolic)
Positioning: Trendelenburg position (legs elevated) to improve venous return

3. Secondary Management

Adjunctive Medications

H1 antagonist: Diphenhydramine 25-50 mg IV (or chlorpheniramine 10 mg IM)
H2 antagonist: Ranitidine 50 mg IV (or famotidine 20 mg IV)
Corticosteroids: Hydrocortisone 200 mg IV OR methylprednisolone 125 mg IV (prevent biphasic reaction at 4-12 hours)
Rationale: Antihistamines and steroids are SECONDARY; epinephrine is the PRIMARY treatment

Rocuronium Reversal with Sugammadex

Dose: Sugammadex 16 mg/kg IV immediately (high-dose immediate reversal protocol)
Rationale: Encapsulates rocuronium in 1:1 ratio → reduces free rocuronium available to trigger ongoing anaphylaxis → may shorten duration and severity
Evidence: Case reports show reversal of anaphylaxis within 3-5 minutes of sugammadex administration
Limitation: Does NOT reverse histamine already released or mast cell degranulation already triggered; mainly theoretical benefit
Availability: May not be immediately available in ED (expensive, restricted formulary); do NOT delay epinephrine while waiting for sugammadex

4. Monitoring and Investigations

Monitoring

Continuous: ECG, SpO2, ETCO2, arterial line for continuous BP monitoring
Hemodynamics: Target MAP greater than 65 mmHg, SBP greater than 90 mmHg
Bronchospasm: Monitor peak airway pressures, plateau pressures, auto-PEEP
Urine output: Foley catheter; target greater than 0.5 mL/kg/h

Investigations

Serum tryptase: Draw STAT (within 15 minutes), at 1 hour, and at 24 hours
- Peak at 1 hour post-reaction
- Elevated tryptase confirms mast cell degranulation (IgE-mediated anaphylaxis)
- Baseline (24 hours) distinguishes acute elevation from baseline mastocytosis
Arterial blood gas: Assess oxygenation, ventilation, acid-base status, lactate
ECG: Monitor for arrhythmias, ST changes (Kounis syndrome - allergic coronary vasospasm)
Serum IgE: Not useful acutely; may be measured later for allergy confirmation

5. Ongoing Management

ICU Admission

Mandatory: All Grade III-IV anaphylaxis require ICU monitoring for 24-48 hours
Biphasic reaction risk: 5-20% of patients have recurrent symptoms at 4-12 hours (hence corticosteroids)
Monitoring: Continuous hemodynamics, ventilation; wean epinephrine infusion slowly (over 12-24 hours)

Ventilator Weaning

Rocuronium duration: 30-40 minutes (single dose); sugammadex reversal reduces to 1-3 minutes
Bronchospasm resolution: May take hours; continue bronchodilators, consider magnesium sulfate 2 g IV if refractory
Sedation: Propofol or benzodiazepine for sedation while intubated; fentanyl for analgesia
Extubation: Once bronchospasm resolved, hemodynamics stable, and patient awake

6. Allergy Work-Up and Follow-Up

Immediate Documentation

Chart: Document anaphylaxis to rocuronium clearly in medical record
Allergy alert: Add to patient's allergy list (electronic medical record, MedicAlert bracelet)
Notify pharmacy: Flag patient to prevent future rocuronium administration

Allergy Testing (6-8 weeks post-reaction)

Skin prick testing: Rocuronium and cross-reactive NMBAs
Intradermal testing: More sensitive than skin prick
Identification: Determine safe alternative NMBA for future anesthesia
- "If rocuronium allergy confirmed: Cisatracurium is typically safe (different chemical class: benzylisoquinolinium vs aminosteroid)"
- "Cross-reactivity: High within aminosteroid class (rocuronium, vecuronium); low between aminosteroids and benzylisoquinoliniums"

Future Anesthesia

Avoid rocuronium: Lifelong contraindication
Safe alternatives: Cisatracurium (benzylisoquinolinium class) generally safe
Premedication: If NMBA required in future, consider premedication with H1/H2 antagonists and corticosteroids (though evidence limited)

7. Asthma Exacerbation Management

Concurrent treatment: Once anaphylaxis managed, continue asthma treatment
Bronchodilators: Continuous albuterol nebulization
Corticosteroids: Already given for anaphylaxis (hydrocortisone 200 mg IV); continue for asthma
Magnesium: 2 g IV over 20 minutes if refractory bronchospasm

Examiner Follow-Up Questions:

Why is rocuronium associated with the highest anaphylaxis risk among NMBAs?
- Rocuronium has a tertiary ammonium structure (vs quaternary in other NMBAs) → higher immunogenicity; aminosteroid class has higher cross-reactivity than benzylisoquinoliniums
What is the mechanism of sugammadex reversal of anaphylaxis?
- Sugammadex encapsulates free rocuronium in plasma → reduces rocuronium available to bind IgE on mast cells → may reduce ongoing degranulation; does NOT reverse histamine already released
Why measure tryptase at three time points?
- Immediate (acute), 1 hour (peak), 24 hours (baseline); acute elevation confirms mast cell degranulation; baseline distinguishes acute reaction from underlying mastocytosis

Viva 4: TOF Monitoring and Depth of Paralysis

Scenario: You are managing a 60-year-old woman with severe ARDS on cisatracurium infusion. The nurse reports she has been receiving 3 mcg/kg/min for 24 hours. You perform TOF monitoring on the ulnar nerve and get 0/4 twitches. Discuss your interpretation and management.

Examiner Guidance:

Expects understanding of TOF interpretation and target range
Should identify over-paralysis (0/4 twitches)
Demonstrates knowledge of dose adjustment based on TOF
Discusses risks of complete paralysis
Outlines alternative monitoring sites

Model Answer:

1. Interpretation of TOF 0/4

Meaning

0/4 twitches: greater than 90-95% of acetylcholine receptors are blocked (complete or near-complete paralysis)
Over-paralysis: This exceeds the target of 1-2 twitches (85-90% blockade)
Clinical significance: Risk of drug accumulation, prolonged paralysis after stopping infusion, and possible increased ICUAW risk

Target TOF Range

ICU standard: 1-2 twitches out of 4
1/4: ~80-90% receptors blocked (acceptable)
2/4: ~75-80% receptors blocked (ideal)
0/4: greater than 90% receptors blocked (too deep; increase risk of accumulation)
4/4: below 70% receptors blocked (inadequate paralysis if NMBA indicated)

2. Immediate Management

Reduce Cisatracurium Dose

Current rate: 3 mcg/kg/min
Action: Reduce infusion to 1-2 mcg/kg/min (33-50% dose reduction)
Rationale: Minimize further accumulation and allow partial recovery to 1-2 twitches

Recheck TOF

Timing: Recheck TOF every 30-60 minutes until 1-2 twitches achieved
Adjustment: Once 1-2 twitches, titrate infusion to MAINTAIN this depth (may need 1.5-2.5 mcg/kg/min)
Ongoing monitoring: TOF every 4-6 hours once stable

3. Assess for Factors Potentiating Cisatracurium

Check Blood Gas

Acidosis: pH below 7.25 SLOWS Hofmann elimination → prolonged cisatracurium effect
Management: If acidotic, optimize ventilation or consider sodium bicarbonate if severe metabolic acidosis (pH below 7.2)
Target: pH 7.35-7.45

Check Temperature

Hypothermia: T below 35°C SLOWS Hofmann elimination → prolonged effect
Management: Rewarm to 36-37°C (use warming blanket, warmed IV fluids, increase ambient temperature)

Check Electrolytes

Hypokalemia (K+ below 3.5 mmol/L): Potentiates NMBAs
Hypomagnesemia (Mg2+ below 0.7 mmol/L): Potentiates NMBAs
Hypophosphatemia (Phos below 0.8 mmol/L): Associated with muscle weakness
Hypocalcemia (iCa2+ below 1.0 mmol/L): Potentiates NMBAs
Management: Correct electrolyte abnormalities to normal range

Review Concurrent Medications

Aminoglycosides (gentamicin, tobramycin): Potentiate NMBAs (inhibit presynaptic ACh release)
Magnesium sulfate: Potentiates NMBAs
Calcium channel blockers: Potentiate NMBAs
Volatile anesthetics (if patient recently transferred from OR): Potentiate NMBAs
Management: Reduce cisatracurium dose if any of these medications present

4. Assess Sedation Depth

Mandatory Deep Sedation During Paralysis

RASS target: -4 to -5 (cannot be assessed in paralyzed patient; RASS will automatically be -5)
BIS monitoring: If available, check BIS value; target 40-60
- "If BIS greater than 60: Increase sedation URGENTLY (risk of awareness)"
- "If BIS 40-60: Adequate sedation"
- "If BIS below 40: Very deep sedation (may contribute to hemodynamic instability)"

Review Sedation Infusions

Propofol: Ensure infusion running at adequate rate (25-75 mcg/kg/min)
Fentanyl: Ensure analgesia adequate (50-200 mcg/h)
Pump function: Check pumps working, lines patent, no disconnections
Never perform sedation vacation: While patient paralyzed (risk of awareness)

5. Risks of Over-Paralysis (TOF 0/4)

Prolonged Paralysis

Accumulation: Complete blockade suggests drug accumulation → may take LONGER to recover after stopping infusion
Unpredictable recovery: May extend from expected 30-60 minutes to several hours

ICU-Acquired Weakness (ICUAW)

Depth of blockade: Some evidence suggests deeper paralysis (TOF 0/4) associated with higher ICUAW risk vs lighter paralysis (TOF 1-2/4)
Mechanism: Complete muscle disuse atrophy vs partial receptor occupancy allowing some muscle tone

Drug Wastage

Unnecessary paralysis: Deeper than needed to achieve clinical goal (ventilator synchrony, oxygenation)
Cost: Cisatracurium is expensive; avoid excessive dosing

6. Alternative TOF Monitoring Sites

Facial Nerve (If Ulnar Nerve Inaccessible)

Indication: Prone positioning, arm trauma, severe edema, lines/dressings obscuring wrist
Electrode placement: Temple, lateral to eye
Response: Orbicularis oculi contraction (eye twitch) or corrugator supercilii (eyebrow furrow)
Interpretation: Facial muscles are MORE RESISTANT to NMBAs than hand muscles
- Facial nerve TOF 0/4 suggests VERY deep blockade (hand would be 0/4 for even longer)
- Facial nerve TOF 1-2/4 may correspond to hand TOF 0-1/4
Target at facial nerve: 0-1 twitches (deeper than hand target of 1-2 twitches)
Caution: High risk of direct muscle stimulation (false twitches if electrodes too close to muscle)

Posterior Tibial Nerve

Indication: When both upper extremities and face inaccessible
Electrode placement: Behind medial malleolus
Response: Flexor hallucis brevis contraction (big toe plantar flexion)
Interpretation: Similar sensitivity to ulnar nerve
Target: 1-2 twitches

7. Post-Tetanic Count (PTC) When TOF 0/4

Indication

When TOF is 0/4, PTC provides additional information about depth of very deep blockade

Technique

Deliver 50 Hz tetanic stimulation for 5 seconds
Wait 3 seconds
Deliver single twitches at 1 Hz
Count number of twitches (0-15)

Interpretation

PTC 0: Extremely deep blockade (greater than 95% receptors blocked)
PTC 1-2: Very deep blockade (~90-95% receptors blocked); TOF recovery imminent (within 10-20 minutes)
PTC 8-10: Deep blockade (~85-90% receptors blocked); TOF will likely recover to 1-2/4 soon
PTC greater than 10: Moderate blockade; TOF likely to recover to 4/4 within 30 minutes

Action Based on PTC

PTC 0: STOP cisatracurium temporarily; allow recovery to PTC 1-2, then restart at lower rate
PTC 1-5: Reduce cisatracurium rate by 50%; recheck in 30 minutes
PTC 6-10: Reduce cisatracurium rate by 25%; recheck in 30 minutes

8. Clinical Correlation

Assess Patient Response

Ventilator synchrony: If patient WAS fighting ventilator (indication for NMBA) and now TOF 0/4, ask: Is 0/4 necessary?
- "Answer: NO; 1-2/4 sufficient to prevent dyssynchrony"
Oxygenation: Monitor P/F ratio, SpO2, FiO2 requirement
- If improving, consider whether NMBA still indicated at all (may be able to stop after 48 hours)

Daily Reassessment

Indication: Does patient still meet criteria for NMBA? (Refractory hypoxemia, severe dyssynchrony)
Duration: Goal below 48 hours maximum (ACURASYS protocol)
TOF vacation: Some centers perform daily "TOF vacation" (stop cisatracurium for 1-2 hours to allow TOF recovery to 4/4, reassess need, then restart if still indicated)

Examiner Follow-Up Questions:

Why is the target TOF 1-2 twitches instead of 0/4?
- 1-2 twitches (85-90% blockade) is sufficient to prevent ventilator dyssynchrony and achieve clinical goals; 0/4 risks accumulation, prolonged paralysis, and possibly higher ICUAW incidence; minimizes drug dose and cost
How does acidosis affect cisatracurium?
- Hofmann elimination is pH-dependent; acidosis (pH below 7.25) SLOWS the spontaneous chemical degradation → prolonged duration of cisatracurium; alkalosis accelerates elimination
Why is the facial nerve more resistant to NMBAs than the ulnar nerve?
- Facial muscles (orbicularis oculi) have higher blood flow and are closer to central circulation → paralyzed LAST during onset, recover FIRST during offset; ulnar nerve (adductor pollicis) is peripheral → paralyzed FIRST, recovers LAST; facial nerve better reflects diaphragm paralysis (also central)

Summary and Key Takeaways

CICM Exam Essentials

Must-Know Facts

Cisatracurium is first-line in multiorgan failure due to Hofmann elimination (organ-independent)
ROSE trial (2019) changed practice: NMBAs are NOW rescue therapy, NOT routine prophylaxis in ARDS
TOF monitoring target: 1-2 twitches (85-90% receptor blockade); avoid 0/4 complete paralysis
Deep sedation mandatory: RASS -4 to -5 or BIS 40-60 during paralysis to prevent awareness
ICUAW risk: 25-50% in patients ventilated greater than 5 days; increased by NMBA + corticosteroids
Rocuronium has highest anaphylaxis risk: 1:6,500 incidence among NMBAs
Vecuronium contraindicated in renal failure: Active metabolite (3-desacetyl-vecuronium) accumulates
VTE prophylaxis essential: Combined pharmacological (LMWH/UFH) + mechanical (SCDs) in paralyzed patients
Sugammadex reverses rocuronium/vecuronium: 2-4 mg/kg dose; contraindicated in severe renal failure (CrCl below 30)
Duration should be minimized: Ideally below 48 hours; stop as soon as indication resolves

Clinical Decision-Making Framework

When to Use NMBAs (Post-ROSE Era)

Rescue therapy ONLY: Reserve for severe, refractory cases
Indications: P/F below 100 mmHg, severe dyssynchrony despite optimal sedation, prone positioning in unstable patient, refractory ICP
Optimize first: Ensure lung-protective ventilation, adequate sedation/analgesia, prone positioning if indicated
Avoid routine use: Light sedation + lung protection superior to routine early paralysis

Agent Selection Algorithm

Multiorgan failure (renal + hepatic): Cisatracurium (ONLY choice)
Renal failure alone: Cisatracurium (vecuronium CONTRAINDICATED)
Hepatic failure alone: Cisatracurium preferred; rocuronium acceptable with dose reduction
Normal organ function: Cisatracurium (first-line); rocuronium acceptable if rapid reversal needed
Emergency intubation: Rocuronium 1-1.2 mg/kg (fastest onset non-depolarizing NMBA)

Monitoring Checklist

TOF: Every 4-6 hours; target 1-2 twitches
Sedation depth: RASS -4 to -5 (if assessable); BIS 40-60 if available
Ventilator: Monitor Pplat, driving pressure, P/F ratio
VTE prophylaxis: LMWH/UFH + SCDs
Daily reassessment: Is NMBA still indicated? Can we stop?

Common Pitfalls and How to Avoid Them

Pitfall 1: Using vecuronium in renal failure

Consequence: Prolonged paralysis for days due to 3-desacetyl-vecuronium accumulation
Avoidance: ALWAYS use cisatracurium in renal failure

Pitfall 2: Not monitoring TOF

Consequence: Over-paralysis (TOF 0/4), drug wastage, prolonged recovery, increased ICUAW risk
Avoidance: TOF every 4-6 hours; titrate to 1-2 twitches

Pitfall 3: Inadequate sedation during paralysis

Consequence: Awareness, post-ICU PTSD, psychological trauma
Avoidance: Deep sedation (RASS -4 to -5) BEFORE initiating paralysis; BIS 40-60; NEVER perform sedation vacation while paralyzed

Pitfall 4: Forgetting VTE prophylaxis

Consequence: DVT, PE (VTE risk increased 2-3x in paralyzed patients)
Avoidance: LMWH/UFH + SCDs for ALL paralyzed patients

Pitfall 5: Prolonged paralysis without reassessment

Consequence: Unnecessary ICUAW risk, delayed mobilization, worse outcomes
Avoidance: Daily reassessment; stop NMBA as soon as indication resolves; target below 48 hours

Pitfall 6: Using rocuronium without allergy history

Consequence: Anaphylaxis (1:6,500 incidence)
Avoidance: Ask about previous anesthesia reactions; have epinephrine ready; know sugammadex reversal dose (16 mg/kg for immediate reversal in anaphylaxis)

References and Further Reading

Key Primary Literature

Papazian L, et al. (2010) - ACURASYS trial: Neuromuscular blockers in early ARDS. N Engl J Med 363:1107-1116. PMID: 20843245
National Heart, Lung, and Blood Institute PETAL Network (2019) - ROSE trial: Early neuromuscular blockade in ARDS. N Engl J Med 380:1997-2008. PMID: 31112383
Murray MJ, et al. (2016) - Clinical practice guidelines for sustained neuromuscular blockade in the adult critically ill patient. Crit Care Med 44:2079-2103. PMID: 27171491

Additional Key PMIDs

27171491 (Murray 2016 SCCM NMBA guidelines)
24717781 (ICUAW systematic review)
23361625 (Prolonged paralysis risk factors)
22809908 (Anaphylaxis to NMBAs)
23782763 (VTE prophylaxis in ICU)
24384729 (Awareness during mechanical ventilation)
18317309 (TOF monitoring in ICU)
17667242 (BIS monitoring during paralysis)
19445675 (Hofmann elimination pharmacology)
16424729 (NMBA pharmacokinetics in critical illness)
25033642 (Sugammadex in ICU)
24077281 (Neostigmine vs sugammadex comparison)
33326767 (Surviving Sepsis Campaign 2021)
29564389 (TOF monitoring systematic review)
24499827 (Shivering management in TTM)
29195450 (Indigenous ICU outcomes Australia)
28846820 (Rural ICU resource limitations)

Recommended CICM Resources

CICM OE-07-3: Pharmacology of neuromuscular blocking drugs
CICM OE-08-4: Monitoring neuromuscular blockade
ANZICS Adult APD Statements: Sedation and analgesia guidelines
UpToDate: "Neuromuscular blocking agents in critically ill patients"
Deranged Physiology: ICU pharmacology section on NMBAs

Document Information

Version: 1.0
Last Updated: 2026-01-24
Word Count: ~11,500 words
Target Audience: CICM Second Part candidates, ANZCA Final candidates, EDIC Part II candidates
Evidence Level: High (Multiple RCTs, systematic reviews, clinical practice guidelines)

This topic provides comprehensive, evidence-based coverage of neuromuscular blockade in the ICU with specific focus on CICM examination requirements. All recommendations are based on current best evidence and Australian/New Zealand practice standards.

Clinical board

Urgent signals

Neuromuscular Blockade in ICU

Quick Answer

CICM Exam Focus

Written Exam Priorities

Viva Exam Scenarios

Hot Topics

Key Points

Epidemiology

Incidence and Prevalence

Risk Factors for Prolonged Paralysis

ICU-Acquired Weakness (ICUAW)

Pathophysiology

Neuromuscular Junction Physiology

Mechanism of Non-Depolarizing NMBAs

Mechanism of Depolarizing NMBAs (Succinylcholine)

Hofmann Elimination (Cisatracurium)

Pharmacokinetics of Common ICU NMBAs

ICU-Acquired Weakness Pathophysiology

Clinical Presentation

Indications for Neuromuscular Blockade

1. Severe Acute Respiratory Distress Syndrome (ARDS)

2. Intracranial Hypertension

3. Severe Ventilator Dyssynchrony

4. Shivering During Targeted Temperature Management (TTM)

5. Facilitation of Procedures

6. Other Indications

Contraindications

Absolute Contraindications

Relative Contraindications

Investigations and Monitoring

Train-of-Four (TOF) Monitoring

Principle

Target TOF Count

Monitoring Sites

TOF Ratio

Post-Tetanic Count (PTC)

Sedation Depth Monitoring

RASS Limitations

Bispectral Index (BIS) Monitoring

Sedation Protocol During Paralysis

Continuous EEG (cEEG) Monitoring

Physiological Indicators (Unreliable but Monitored)

Laboratory Monitoring

Management

Agent Selection

First-Line: Cisatracurium (Nimbex)

Second-Line: Rocuronium (Zemuron)

Third-Line: Vecuronium (Norcuron)

NOT Recommended in ICU: Atracurium (Tracrium)

NOT Used in ICU: Succinylcholine (Suxamethonium)

Dosing Protocols

ACURASYS Protocol (Historical - Severe ARDS)

Modern ICU Paralysis Protocol (Rescue Therapy)

Ventilator Management During Paralysis

Lung-Protective Ventilation (Mandatory)

Prone Positioning

Recruitment Maneuvers

Reversal of Neuromuscular Blockade

Spontaneous Recovery

Pharmacological Reversal: Neostigmine

Pharmacological Reversal: Sugammadex (Bridion)

Reversal Strategy by Agent

Complications

ICU-Acquired Weakness (ICUAW)

Prolonged Paralysis

Anaphylaxis

Awareness and Recall

Venous Thromboembolism (VTE)

Other Complications

Evidence Base

ACURASYS Trial (2010)

ROSE Trial (2019)

Current Guidelines and Recommendations

Surviving Sepsis Campaign 2021

Society of Critical Care Medicine (SCCM) 2016

European Society of Intensive Care Medicine (ESICM) 2020

Other Relevant Evidence

Australian and New Zealand Context