Guillain-Barré Syndrome

Quick Answer

\u003e One-liner: Guillain-Barré Syndrome is an acute immune-mediated polyradiculoneuropathy causing rapidly ascending flaccid paralysis with areflexia, frequently requiring ICU admission for respiratory failure, mechanical ventilation, immunotherapy (IVIg or plasma exchange), and management of life-threatening autonomic dysfunction.

GBS is the most common cause of acute flaccid paralysis worldwide, with 20-30% of patients requiring mechanical ventilation. [1] The critical ICU priorities are: (1) respiratory monitoring with serial pulmonary function tests (intubate if FVC \u003c20 mL/kg or NIF \u003c-30 cmH₂O), (2) autonomic monitoring on continuous cardiac telemetry (arrhythmias occur in 60-70%), (3) early immunotherapy (IVIg 2 g/kg over 5 days OR plasma exchange, initiated within first 2 weeks), and (4) prevention of ICU complications (VTE prophylaxis, nutrition, physiotherapy). [2,3] Mortality is 3-7% acutely, with autonomic instability and respiratory complications being the leading causes of death. [4] At 1 year, 20% have severe disability despite treatment. [5] Early recognition, timely ICU admission, and aggressive supportive care improve outcomes. [6]

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CICM Exam Focus

Second Part Written Exam

• Diagnostic criteria: Brighton criteria levels, CSF albuminocytologic dissociation (protein \u003e0.55 g/L, WCC \u003c10), nerve conduction studies (demyelination: prolonged distal latencies, conduction block, temporal dispersion; axonal: reduced amplitudes)
• Respiratory monitoring: Serial FVC measurements, negative inspiratory force (NIF), maximum expiratory pressure (MEP), 20/30/40 rule for intubation, bulbar assessment
• Immunotherapy indications: IVIg 0.4 g/kg/day × 5 days vs plasma exchange 40-50 mL/kg × 5 exchanges, evidence base (RCTs showing equivalent efficacy), contraindications (IgA deficiency for IVIg, coagulopathy/hemodynamic instability for plasma exchange)
• Autonomic management: Cardiac arrhythmias (bradycardia requiring pacing, tachycardia), labile blood pressure (avoid aggressive treatment of transient hypertension), urinary retention, ileus, SIADH
• Ventilatory management: Lung-protective ventilation, weaning challenges (diaphragmatic weakness, bulbar dysfunction), tracheostomy timing (if predicted ventilation \u003e2-3 weeks)
• Prognostication: EGRIS score (Erasmus GBS Respiratory Insufficiency Score), modified Erasmus GBS Outcome Score (mEGOS), predictors of prolonged ventilation and poor outcome

Viva Voce Topics

• Differential diagnosis of acute flaccid paralysis in ICU
• Approach to the intubated patient with suspected neuromuscular respiratory failure
• Management of autonomic crisis in GBS (severe bradycardia, labile BP)
• Weaning from mechanical ventilation in GBS
• Complications of immunotherapy (IVIg: renal dysfunction, thrombosis; plasma exchange: hypocalcemia, citrate toxicity, catheter-related infections)
• Critical illness polyneuropathy/myopathy vs GBS in the ICU patient

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Key Points

• GBS is an acute immune-mediated polyradiculoneuropathy, most commonly the demyelinating form (AIDP, 85-90% in Western countries). [7]
• 20-30% require mechanical ventilation; respiratory failure is the leading cause of ICU admission and mortality. [8]
• Classic presentation: ascending symmetrical weakness with areflexia, peaking at 2-4 weeks, following a preceding infection (Campylobacter jejuni, CMV, EBV, Zika virus). [9]
• CSF findings: Albuminocytologic dissociation (protein \u003e0.55 g/L with WCC \u003c10/µL), sensitivity 50% in week 1, increasing to \u003e85% by week 3. [10]
• Electrophysiology: Nerve conduction studies show demyelination (AIDP: prolonged distal latencies, conduction block, slowed velocities) or axonal loss (AMAN/AMSAN: reduced amplitudes). [11]
• Respiratory monitoring: Serial FVC and NIF measurements at least every 4-6 hours; intubate electively if FVC \u003c20 mL/kg, NIF \u003c-30 cmH₂O, or MEP \u003c40 cmH₂O (20/30/40 rule). [12,13]
• Immunotherapy: IVIg (2 g/kg over 5 days) and plasma exchange (5 exchanges) are equally effective; combining both offers no benefit and may increase adverse effects. [14,15]
• Autonomic dysfunction: Occurs in 60-70%; includes cardiac arrhythmias (bradycardia requiring pacing, sinus tachycardia), labile BP (avoid aggressive treatment of transient hypertension), urinary retention, ileus, and SIADH. [16]
• Steroids are NOT beneficial: Multiple RCTs show no benefit from corticosteroids alone; may be harmful when combined with IVIg. [17,18]
• Prognosis: 3-7% mortality during acute phase, 15% with severe complications; 20% have severe disability at 1 year; 3-5% relapse. [19]

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Classification and Subtypes

Guillain-Barré Syndrome is classified into several subtypes based on electrophysiological and clinical features: [20,21]

Acute Inflammatory Demyelinating Polyneuropathy (AIDP)

• Most common form in Western countries (85-90%). [7]
• Pathology: Primary demyelination of peripheral nerves due to antibody and complement-mediated attack on myelin sheaths.
• Electrophysiology: Prolonged distal motor latencies, conduction block, temporal dispersion, slowed conduction velocities, prolonged or absent F-waves.
• Recovery: Generally good, as remyelination can occur over weeks to months.

Acute Motor Axonal Neuropathy (AMAN)

• Predominantly in Asia (30-50% of cases in China, Japan). [22]
• Pathology: Antibody-mediated attack on motor nerve axons at nodes of Ranvier (anti-GM1, anti-GD1a antibodies).
• Electrophysiology: Reduced compound muscle action potential (CMAP) amplitudes, normal or mildly slowed conduction velocities, normal sensory nerve action potentials (SNAPs).
• Clinical: Pure motor involvement, no sensory symptoms.
• Prognosis: Can be severe with axonal degeneration, but reversible conduction failure (nodo-paranodopathy) may allow rapid recovery in some cases.

Acute Motor and Sensory Axonal Neuropathy (AMSAN)

• Severe axonal variant affecting both motor and sensory nerves.
• Pathology: Widespread axonal degeneration.
• Electrophysiology: Reduced CMAP and SNAP amplitudes, denervation on EMG.
• Prognosis: Poorest of all GBS subtypes; prolonged recovery, significant residual deficits common.

Miller Fisher Syndrome (MFS)

• Classic triad: Ophthalmoplegia (extraocular muscle weakness), ataxia, areflexia.
• Anti-GQ1b antibodies positive in \u003e90% of cases. [23]
• Usually does not require ICU admission unless overlaps with AIDP or bulbar involvement develops.
• Sensory symptoms minimal; limb weakness rare.
• Prognosis: Excellent, most recover fully within 3-6 months.

Pharyngeal-Cervical-Brachial Variant

• Weakness predominantly affecting oropharyngeal, neck, and shoulder muscles.
• High risk of respiratory failure due to bulbar and diaphragmatic involvement.
• Often requires ICU admission for airway protection and ventilatory support.

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Clinical Presentation in ICU

Progressive Weakness

• Onset: Typically develops over hours to days (up to 4 weeks from symptom onset to nadir). [24]
• Pattern: Ascending symmetrical weakness starting in distal lower limbs, progressing proximally and to upper limbs.
• Severity: Ranges from difficulty walking to complete quadriplegia.
• Progression: 50% reach nadir by 2 weeks, 90% by 4 weeks. [25]
• Reflexes: Areflexia or hyporeflexia is a cardinal feature (present in 90% at nadir). [26]

Respiratory Failure

• Incidence: 20-30% of GBS patients require mechanical ventilation. [27]
• Mechanism: Diaphragmatic weakness (phrenic nerve involvement), intercostal muscle weakness, bulbar dysfunction with aspiration.
• Timing: Respiratory failure typically develops within the first 2 weeks; median time to intubation is 7 days from symptom onset. [28]
• Predictors of respiratory failure (EGRIS score): [29]
  • Time from onset to admission \u003c7 days (3 points)
  • Inability to stand unaided (3 points)
  • Inability to lift elbows (2 points)
  • Inability to lift head (1 point)
  • Facial or bulbar weakness (1 point)
  • "EGRIS ≥5: 85% probability of requiring ventilation within 1 week"

Bulbar Dysfunction

• Incidence: 40-50% have bulbar weakness. [30]
• Features: Dysphagia, dysarthria, facial weakness (bilateral lower motor neuron CN VII palsy), inability to cough or clear secretions.
• Risk: High aspiration risk, even with adequate respiratory muscle strength.
• Management: May require intubation for airway protection even if FVC is adequate.

Autonomic Dysfunction

• Incidence: 60-70% develop significant autonomic instability. [31]
• Cardiac: [32]
  • Sinus tachycardia (most common)
  • Bradycardia or asystole (may require temporary pacing)
  • Arrhythmias (atrial fibrillation, ventricular ectopy)
  • Orthostatic hypotension
• Blood pressure lability:
  • Episodes of severe hypertension alternating with hypotension
  • Exaggerated response to vasopressors and sedatives
  • Avoid aggressive treatment of transient hypertension (may precipitate severe hypotension)
• Other autonomic features:
  • Urinary retention (50%)
  • Ileus and gastroparesis
  • Syndrome of inappropriate ADH secretion (SIADH)
  • Abnormal sweating
• Mortality: Autonomic dysfunction is a leading cause of death in GBS (sudden cardiac arrest). [33]

Sensory Symptoms

• Paraesthesias: Tingling and numbness in distal extremities (common early symptom).
• Pain: Neuropathic pain occurs in 50-80% of patients; can be severe and difficult to treat. [34]
  • Back pain, radicular pain, dysesthetic pain.
  • May occur before weakness develops.
• Proprioception: Loss of position sense can contribute to ataxia.

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Diagnosis in ICU

Clinical Diagnostic Criteria (Brighton Criteria)

Level 1 (Highest diagnostic certainty):

• Bilateral flaccid weakness of limbs
• Decreased or absent deep tendon reflexes in weak limbs
• Monophasic illness pattern
• Time to peak weakness: 12 hours to 28 days, then plateau
• CSF: Cell count \u003c50/µL, protein elevated
• Electrophysiology: Nerve conduction studies consistent with GBS
• Absence of alternative diagnosis

Level 2-4: Progressive levels of diagnostic uncertainty

In the ICU, empiric treatment should be initiated in patients with Level 2 or higher certainty while investigations are pending. [35]

Cerebrospinal Fluid (CSF) Analysis

• Timing: CSF protein may be normal in the first week (50% sensitivity), but increases to \u003e85% sensitivity by weeks 2-3. [36]
• Classic finding: Albuminocytologic dissociation
  • "Protein: \u003e0.55 g/L (often 1-3 g/L in severe cases)"
  • "White cell count: \u003c10 cells/µL (typically \u003c5/µL)"
• If WCC \u003e50/µL: Consider alternative diagnoses (Lyme disease, HIV, sarcoidosis, lymphomatous meningitis).
• Glucose: Normal.

Nerve Conduction Studies (NCS) and Electromyography (EMG)

Electrophysiology is the gold standard for confirming GBS and differentiating subtypes, but should NOT delay treatment. [37]

AIDP (Demyelinating) Pattern:

• Prolonged distal motor latencies (\u003e110% upper limit of normal, \u003e150% if amplitude \u003c lower limit of normal)
• Conduction velocity slowing (\u003c90% lower limit of normal)
• Conduction block (reduction in proximal:distal CMAP amplitude \u003e50%)
• Temporal dispersion (prolongation and desynchronization of waveforms)
• Prolonged or absent F-waves (\u003e120% upper limit of normal)
• Normal or mildly reduced CMAP amplitudes (initially)

AMAN/AMSAN (Axonal) Pattern:

• Reduced CMAP amplitudes (\u003c80% lower limit of normal)
• Normal or mildly reduced conduction velocities (\u003e80% lower limit of normal)
• Normal distal latencies
• Reduced SNAP amplitudes in AMSAN, normal in AMAN
• EMG: Denervation potentials (fibrillation potentials, positive sharp waves) after 2-3 weeks

Serum Antibodies

• Anti-ganglioside antibodies: Present in 60% of GBS cases. [38]
  • "Anti-GM1: AMAN, AMSAN"
  • Anti-GD1 a: AMAN
  • Anti-GQ1 b: Miller Fisher Syndrome (\u003e90% positive)
• Clinical utility: Confirmatory but not required for diagnosis; results often not available acutely.

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Respiratory Monitoring and Intubation Criteria

Serial Pulmonary Function Testing

• Frequency: Every 4-6 hours in patients with progressive weakness or respiratory symptoms. [39]
• Key measurements:
  • "Forced Vital Capacity (FVC): Most important bedside test"
  • Negative Inspiratory Force (NIF) or Maximal Inspiratory Pressure (MIP)
  • Maximum Expiratory Pressure (MEP)

The 20/30/40 Rule for Intubation

Elective intubation should be considered when: [40,41]

• FVC \u003c20 mL/kg (or \u003c1.5 L absolute)
• NIF \u003c-30 cmH₂O (normal: -80 to -120 cmH₂O)
• MEP \u003c40 cmH₂O (normal: 100-150 cmH₂O)

Additional Intubation Indications

• Bulbar dysfunction: Inability to protect airway, pooling secretions, aspiration risk
• Inability to cough effectively: Inability to clear secretions
• Rapid progression: FVC declining \u003e30% in 24 hours
• Severe autonomic instability: Requiring airway protection during hemodynamic instability
• Inability to maintain oxygen saturation despite supplemental O₂

Intubation Considerations

• Prefer elective intubation over emergency intubation (better outcomes, fewer complications). [42]
• Rapid sequence induction:
  • "Avoid suxamethonium (succinylcholine): Risk of hyperkalemia due to denervation hypersensitivity."
  • Use rocuronium or vecuronium (may have prolonged effect).
• Post-intubation: Lung-protective ventilation (tidal volume 6-8 mL/kg predicted body weight).

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Immunotherapy

Intravenous Immunoglobulin (IVIg)

• Dosing: 0.4 g/kg/day IV for 5 consecutive days (total dose: 2 g/kg). [43]
• Mechanism: Neutralizes pathogenic antibodies, modulates complement activation, reduces inflammation.
• Efficacy: Reduces time on ventilator, improves disability grade at 4 weeks. Equivalent to plasma exchange. [14]
• Timing: Most effective when started within 2 weeks of symptom onset; efficacy diminishes after 4 weeks. [44]
• Advantages: Easier to administer than plasma exchange, no need for vascular access suitable for apheresis, fewer hemodynamic fluctuations.

IVIg Adverse Effects:

• Renal dysfunction: Osmotic nephrosis (sucrose-containing formulations), acute tubular necrosis. Monitor renal function; ensure adequate hydration.
• Thrombotic events: Stroke, MI, pulmonary embolism (2-5% incidence). Risk higher with pre-existing cardiovascular disease. [45]
• Aseptic meningitis: Headache, photophobia, fever (usually self-limiting).
• Hemolytic anemia: Especially with blood group A, B, or AB recipients.
• Anaphylaxis: Rare; risk higher in IgA-deficient patients (check IgA levels before administration).
• Volume overload: Caution in heart failure, renal impairment.

Plasma Exchange (Plasmapheresis, PLEX)

• Dosing: 5 exchanges of 40-50 mL/kg plasma over 10-14 days (typically every other day). [46]
• Mechanism: Removes circulating pathogenic antibodies, complement, and inflammatory mediators.
• Efficacy: Equivalent to IVIg; improves time to independent ambulation, reduces time on ventilator. [15]
• Access: Requires large-bore central venous catheter (dialysis catheter, Vascath).

Plasma Exchange Adverse Effects:

• Hemodynamic instability: Hypotension (especially with albumin replacement), hypovolemia.
• Electrolyte disturbances: Hypocalcemia (citrate binds calcium), hypomagnesemia, hypokalemia.
• Catheter-related complications: Infection (5-10%), thrombosis, bleeding.
• Coagulopathy: Transient reduction in clotting factors (avoid in patients with active bleeding or coagulopathy).
• Allergic reactions: To fresh frozen plasma (FFP) or albumin.

IVIg vs Plasma Exchange: Which to Choose?

• Equivalent efficacy: Multiple RCTs show no significant difference in outcomes. [47]
• IVIg preferred when:
  • Hemodynamic instability (plasma exchange causes BP fluctuations)
  • Coagulopathy or anticoagulation
  • Difficult vascular access
  • Logistical constraints (plasma exchange requires specialized equipment and training)
• Plasma exchange preferred when:
  • IgA deficiency (IVIg contraindicated)
  • Renal impairment (IVIg risk of osmotic nephrosis)
  • Previous IVIg failure or intolerance

Combination Therapy: NOT Recommended

• Multiple RCTs show no additional benefit from combining IVIg and plasma exchange. [48]
• May increase adverse effects and costs.
• Sequential therapy (plasma exchange followed by IVIg, or vice versa) also not beneficial.

Corticosteroids: NOT Effective

• No benefit from oral or IV corticosteroids alone. [18]
• Combination of methylprednisolone + IVIg: Not superior to IVIg alone; possibly harmful. [17]
• Current recommendation: Do NOT use steroids in GBS.

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Mechanical Ventilation Management

Ventilatory Strategy

• Lung-protective ventilation: Tidal volume 6-8 mL/kg predicted body weight, plateau pressure \u003c30 cmH₂O. [49]
• PEEP: 5-8 cmH₂O to prevent atelectasis.
• Mode: Assist-control or pressure support ventilation depending on patient's respiratory drive.
• Avoid hyperventilation: May worsen autonomic instability.

Duration of Mechanical Ventilation

• Median duration: 2-4 weeks, but can range from days to months. [50]
• Predictors of prolonged ventilation (\u003e2 months): [51]
  • Age \u003e60 years
  • Rapid progression to nadir (\u003c7 days)
  • Bulbar weakness
  • Low CMAP amplitudes (indicating axonal loss)
  • Pre-existing pulmonary disease

Tracheostomy Timing

• Consider early tracheostomy (within 7-10 days) if predicted ventilation \u003e2-3 weeks: [52]
  • Facilitates weaning
  • Reduces sedation requirements
  • Improves patient comfort
  • Allows earlier communication and oral intake
• Percutaneous vs surgical: Either approach acceptable; percutaneous dilatational tracheostomy can be performed at bedside.

Weaning from Mechanical Ventilation

• Challenges: [53]
  • Diaphragmatic weakness and atrophy (prolonged ventilation)
  • Bulbar dysfunction (extubation failure due to aspiration)
  • Autonomic instability triggered by weaning trials
• Weaning predictors:
  • FVC \u003e15-20 mL/kg
  • NIF \u003c-30 cmH₂O
  • Rapid shallow breathing index (RSBI = RR/VT) \u003c105 breaths/min/L
  • Improving motor strength (ability to lift head off bed, lift limbs against gravity)
• Spontaneous breathing trials (SBT):
  • T-piece or pressure support (PS 5-7 cmH₂O) for 30-120 minutes
  • Monitor for respiratory distress, hemodynamic instability
• Extubation criteria:
  • Successful SBT
  • Adequate cough strength
  • Minimal secretions
  • Bulbar function assessment (swallow evaluation, gag reflex) is critical
• Post-extubation: High-risk for failure; consider prophylactic non-invasive ventilation (NIV) or high-flow nasal cannula (HFNC).

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Autonomic Dysfunction Management

Cardiac Monitoring

• Continuous telemetry: Mandatory for all ICU patients with GBS due to risk of life-threatening arrhythmias. [54]
• Common arrhythmias:
  • Sinus tachycardia (most common, usually benign)
  • Bradycardia or sinus pauses
  • Asystole (rare but potentially fatal)
  • Atrial fibrillation
  • Ventricular ectopy

Bradycardia and Heart Block

• Severe bradycardia (HR \u003c40 bpm) or asystole:
  • Temporary pacing (transcutaneous or transvenous) may be required. [55]
  • Atropine often ineffective (vagal denervation).
• Avoid vagal stimulation: Suctioning, turning can precipitate bradycardia.

Blood Pressure Lability

• Episodic hypertension: [56]
  • Often transient and self-limiting (minutes to hours).
  • Avoid aggressive treatment with short-acting antihypertensives (may precipitate severe hypotension).
  • "If sustained severe hypertension (SBP \u003e180 mmHg): Use short-acting titratable agents (esmolol, labetalol, nitroprusside)."
• Hypotension:
  • Exaggerated response to sedatives, vasodilators, positive pressure ventilation.
  • Treat with judicious fluid resuscitation.
  • "If vasopressor required: Start at low doses, titrate carefully (exaggerated response)."

Other Autonomic Complications

• Urinary retention: Bladder catheterization; monitor for SIADH (hyponatremia).
• Ileus and gastroparesis: Nasogastric decompression, prokinetics (metoclopramide, erythromycin), early enteral nutrition when possible.
• SIADH: Fluid restriction, hypertonic saline if severe symptomatic hyponatremia.

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ICU Complications and Supportive Care

Venous Thromboembolism (VTE) Prophylaxis

• High risk: Immobility, paralysis, mechanical ventilation, autonomic dysfunction.
• Pharmacologic prophylaxis: Low-molecular-weight heparin (LMWH) or unfractionated heparin (UFH) unless contraindicated. [57]
• Mechanical prophylaxis: Sequential compression devices (SCDs), early mobilization once stable.

Nutrition

• Enteral nutrition preferred: Start within 24-48 hours if hemodynamically stable.
• Route: Nasogastric or post-pyloric feeding tube (if gastroparesis).
• Parenteral nutrition: If enteral feeding not tolerated due to ileus.
• Energy requirements: 25-30 kcal/kg/day; higher in hypermetabolic patients.

Pain Management

• Incidence: Neuropathic pain in 50-80% of patients. [58]
• First-line agents:
  • Gabapentin (300-1200 mg TDS)
  • Pregabalin (75-150 mg BD)
  • Amitriptyline (10-75 mg nocte, caution in autonomic dysfunction)
• Adjuncts: Opioids (tramadol, oxycodone), NSAIDs, paracetamol.
• IV options: Ketamine infusion (sub-anesthetic doses), lidocaine infusion.

Physiotherapy and Rehabilitation

• Early mobilization: Passive range-of-motion exercises to prevent contractures.
• Progressive mobilization: Sit-to-stand, gait training as motor function recovers.
• Respiratory physiotherapy: Chest physiotherapy, assisted cough techniques, incentive spirometry.
• Occupational therapy: ADL retraining, adaptive equipment.

Psychological Support

• High incidence: Anxiety, depression, PTSD in ICU survivors with GBS. [59]
• Communication: Communication boards, eye-tracking devices for intubated/tracheostomized patients.
• Psychological support: Reassurance, explanation of disease course, involvement of family.

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Prognosis and Outcome Prediction

Mortality

• Acute phase mortality: 3-7% in developed countries. [60]
• With severe complications: Up to 15% mortality.
• Leading causes of death:
  • Respiratory failure and ventilator-associated complications
  • Autonomic dysfunction (sudden cardiac arrest)
  • Sepsis (pneumonia, catheter-related infections)
  • Pulmonary embolism

Functional Recovery

• Good recovery (able to walk independently): 60-70% at 6 months, 80-85% at 1 year. [61]
• Severe disability at 1 year: 15-20% (unable to walk independently). [5]
• Residual deficits: Weakness, sensory symptoms, fatigue common even with good recovery.

Predictors of Poor Outcome

• Clinical factors: [62]
  • Age \u003e60 years
  • Rapid progression to nadir (\u003c7 days)
  • Severe weakness at nadir (unable to lift arms above head)
  • Bulbar or facial weakness
  • Preceding diarrheal illness (Campylobacter jejuni)
  • Requirement for mechanical ventilation
• Electrophysiological factors:
  • Axonal subtype (AMAN, AMSAN)
  • Low CMAP amplitudes (\u003c20% of lower limit of normal)
  • Denervation on EMG
• Prognostic scores:
  • "Modified Erasmus GBS Outcome Score (mEGOS): Predicts inability to walk independently at 6 months based on age, diarrhea, GBS disability score at 2 weeks. [63]"

Relapse and CIDP

• Relapse: 3-5% of patients have recurrent GBS episodes. [64]
• Treatment-related fluctuations: 5-10% worsen within 2 months after initial improvement (may respond to repeat immunotherapy).
• Chronic Inflammatory Demyelinating Polyneuropathy (CIDP): 3-5% progress to CIDP (defined as continued progression \u003e8 weeks or relapsing course requiring maintenance immunotherapy).

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SAQ Practice Questions

SAQ 1: Respiratory Failure in GBS

Question: A 45-year-old male with Guillain-Barré Syndrome is admitted to ICU. He has progressive limb weakness over 5 days. His forced vital capacity (FVC) is currently 25 mL/kg and negative inspiratory force (NIF) is -35 cmH₂O. Outline your approach to respiratory monitoring and intubation criteria.

Model Answer:

Respiratory Monitoring:

• Serial FVC and NIF measurements every 4-6 hours
• Maximum expiratory pressure (MEP) monitoring
• Clinical assessment: Bulbar function, ability to cough, clear secretions
• Continuous pulse oximetry and respiratory rate monitoring
• Arterial blood gas analysis to assess hypercapnia or hypoxemia

Intubation Criteria (20/30/40 Rule):

• FVC \u003c20 mL/kg or \u003c1.5 L absolute
• NIF \u003c-30 cmH₂O (normal -80 to -120 cmH₂O)
• MEP \u003c40 cmH₂O
• Additional indications:
  • Bulbar weakness with aspiration risk
  • Inability to clear secretions
  • Rapid deterioration (FVC decline \u003e30% in 24 hours)
  • Severe autonomic instability

Current Status:

• This patient's FVC is 25 mL/kg and NIF is -35 cmH₂O
• Both values are borderline but NOT yet meeting intubation criteria
• However, given trend toward deterioration, prepare for elective intubation

Management Plan:

• Continue close monitoring with frequent reassessments
• Prepare for elective intubation (safer than emergency intubation)
• Avoid suxamethonium (risk of hyperkalemia due to denervation)
• Use rocuronium or vecuronium for rapid sequence induction
• Consider early ICU/anesthetic consultation

Examiner Comment: Excellent understanding of respiratory monitoring and intubation thresholds. Recognizes the importance of elective versus emergency intubation.

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SAQ 2: Immunotherapy in GBS

Question: A 55-year-old female presents with rapidly progressive ascending weakness and areflexia over 3 days. GBS is suspected. Discuss the evidence-based immunotherapy options for GBS, including dosing, efficacy, and adverse effects.

Model Answer:

Immunotherapy Options:

1. Intravenous Immunoglobulin (IVIg):

• Dosing: 0.4 g/kg/day IV for 5 consecutive days (total 2 g/kg)
• Mechanism: Neutralizes pathogenic antibodies, modulates complement, reduces inflammation
• Efficacy: Reduces time on ventilator, improves disability grade at 4 weeks; equivalent to plasma exchange
• Timing: Most effective within 2 weeks of symptom onset
• Advantages: Easier to administer, no specialized vascular access required, fewer hemodynamic fluctuations
• Adverse Effects:
  • Renal dysfunction (osmotic nephrosis), ensure hydration
  • "Thrombotic events (stroke, MI, PE): 2-5%"
  • Aseptic meningitis
  • Hemolytic anemia (blood groups A, B, AB)
  • Anaphylaxis (IgA deficiency, check IgA levels)
  • Volume overload

2. Plasma Exchange (PLEX):

• Dosing: 5 exchanges of 40-50 mL/kg plasma over 10-14 days
• Mechanism: Removes circulating antibodies, complement, inflammatory mediators
• Efficacy: Equivalent to IVIg; reduces time on ventilator, improves functional recovery
• Adverse Effects:
  • Hemodynamic instability (hypotension)
  • Hypocalcemia (citrate toxicity)
  • Catheter complications (infection, thrombosis, bleeding)
  • Coagulopathy
  • Allergic reactions to FFP/albumin

3. Combination Therapy:

• NOT recommended: No additional benefit from IVIg + PLEX
• May increase adverse effects

4. Corticosteroids:

• NOT effective: Multiple RCTs show no benefit
• Methylprednisolone + IVIg: Not superior to IVIg alone

Choice of Therapy:

• IVIg and PLEX are equally effective
• IVIg preferred if: hemodynamic instability, coagulopathy, difficult vascular access
• PLEX preferred if: IgA deficiency, renal impairment, previous IVIg failure

This Patient:

• Start IVIg 0.4 g/kg/day × 5 days immediately (within 2 weeks window)
• Monitor renal function, ensure adequate hydration
• Consider thromboprophylaxis given IVIg thrombotic risk

Examiner Comment: Comprehensive answer covering both therapies, correct dosing, and evidence base. Correctly identifies that corticosteroids are not beneficial.

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Viva Scenarios

Viva 1: Autonomic Crisis in GBS

Examiner: You are called to ICU to review a 38-year-old male with GBS who is intubated and ventilated day 5. The nurse reports episodes of severe bradycardia (HR 30s) alternating with tachycardia (HR 140s) and labile blood pressure (SBP ranging 90-200 mmHg over the past hour). How do you approach this?

Candidate: This patient is experiencing severe autonomic dysfunction, a potentially life-threatening complication of GBS occurring in 60-70% of patients.

Examiner: What are your immediate priorities?

Candidate:

1. Ensure continuous cardiac monitoring - the patient should already be on telemetry, but I'd confirm ECG monitoring is functioning.
2. Assess for reversible causes: hypoxia, hypercapnia, pain, full bladder, suction-related vagal stimulation.
3. Check current medications and recent interventions: sedatives, vasopressors, positioning changes that may have triggered this.

Examiner: The patient is well sedated, no recent interventions. ABG shows adequate gas exchange. What's your management plan for the bradycardia?

Candidate:

• Severe bradycardia (\u003c40 bpm or symptomatic) management:
  • Atropine is often ineffective in GBS due to vagal denervation, but can trial 0.5-1 mg IV
  • "If recurrent or persistent: Consider temporary cardiac pacing (transcutaneous pads or transvenous pacing wire)"
  • "Avoid triggers: minimize suctioning, repositioning"

Examiner: Good. Now the blood pressure is 210/110 mmHg. Nursing staff want to give IV labetalol. What do you advise?

Candidate: I would caution against aggressive antihypertensive treatment.

Examiner: Why?

Candidate:

• Hypertensive episodes in GBS autonomic dysfunction are typically transient and self-limiting (minutes to hours)
• Aggressive treatment can precipitate severe rebound hypotension
• The exaggerated response to medications is due to autonomic instability
• I would:
  1. Observe if BP episode is self-limiting (most are)
  2. Treat only if sustained severe hypertension (SBP \u003e180 mmHg for \u003e15 minutes) or evidence of end-organ damage (hypertensive encephalopathy, pulmonary edema)
  3. If treatment needed: Use short-acting titratable agents (esmolol infusion, labetalol, nitroprusside) at low starting doses with careful titration

Examiner: The hypertension settles after 10 minutes, but now the patient's SBP is 70 mmHg. How do you manage this?

Candidate:

• Hypotension management:
  1. Fluid bolus (250-500 mL crystalloid), but cautiously as these patients can be fluid sensitive
  2. If persistent: Low-dose vasopressor (noradrenaline starting at 0.05-0.1 mcg/kg/min)
  3. Titrate carefully - exaggerated response to vasopressors in GBS
  4. Consider reducing sedation if causing vasodilation

Examiner: Excellent. What is the mortality risk from autonomic dysfunction in GBS?

Candidate: Autonomic dysfunction is a leading cause of death in GBS. Sudden cardiac arrest from arrhythmias (bradycardia, asystole) accounts for a significant proportion of the 3-7% acute phase mortality. Continuous cardiac monitoring is mandatory in the ICU setting.

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Viva 2: Weaning and Extubation in GBS

Examiner: A 50-year-old female with GBS has been intubated for 3 weeks. She has shown gradual improvement in motor strength. You are asked to assess her for weaning. How do you approach this?

Candidate: Weaning from mechanical ventilation in GBS presents unique challenges due to neuromuscular weakness, bulbar dysfunction, and autonomic instability. I would perform a comprehensive assessment before attempting weaning.

Examiner: What specific assessments would you perform?

Candidate:

1. Respiratory Muscle Strength:

• Forced vital capacity (FVC): Target \u003e15-20 mL/kg for successful weaning
• Negative inspiratory force (NIF): Target \u003c-30 cmH₂O (more negative is better)
• Maximum expiratory pressure (MEP): Adequate cough strength
• Rapid shallow breathing index (RSBI): RR/VT \u003c105 breaths/min/L on minimal support

2. Bulbar Function:

• Swallow assessment: Critically important; can patient swallow safely?
• Gag reflex: Present?
• Cough strength: Ability to clear secretions
• Secretion volume: Minimal secretions
• This is crucial because extubation failure due to aspiration is common in GBS even with adequate respiratory muscle strength

3. Motor Strength:

• Can patient lift head off bed? (indicates neck muscle strength)
• Can patient lift limbs against gravity?
• Overall improvement trend

4. Autonomic Stability:

• No recent episodes of severe BP lability or arrhythmias
• Weaning trials can trigger autonomic instability

Examiner: Her FVC is 18 mL/kg, NIF is -35 cmH₂O. She can lift her head and arms off the bed. How do you proceed?

Candidate:

• FVC is borderline (target \u003e20 mL/kg ideally, but \u003e15 mL/kg acceptable)
• NIF is adequate
• Motor strength improving

I would proceed with a spontaneous breathing trial (SBT):

• Method: T-piece or pressure support 5-7 cmH₂O + PEEP 5 for 30-120 minutes
• Monitoring:
  • Respiratory rate (should not be \u003e35/min or increase \u003e50% from baseline)
  • Oxygen saturation \u003e90%
  • Heart rate, blood pressure (watch for autonomic instability)
  • Subjective dyspnea, anxiety
  • ABG at end of trial (pH, PaCO₂)

Examiner: She tolerates the SBT well. Would you extubate?

Candidate: Not yet. I need to assess bulbar function first as this is a critical factor in GBS.

Examiner: How do you assess this in an intubated patient?

Candidate:

• Cuff leak test: Deflate ETT cuff and assess for air leak around tube (predicts upper airway edema)
• Bedside swallow evaluation: Can be difficult while intubated
• Consider: Speech and language therapist (SLT) assessment
• Gag reflex: Assess with suction catheter
• Secretion management: Volume and character of secretions, frequency of suctioning required

If bulbar function is concerning, options include:

• Post-extubation prophylactic NIV or HFNC (high-flow nasal cannula) to reduce reintubation risk
• Consider tracheostomy if prolonged weaning anticipated or high aspiration risk

Examiner: Good, what is the extubation failure rate in GBS?

Candidate: Extubation failure rates are higher in GBS compared to other causes of respiratory failure, reported at 15-25%, primarily due to:

• Bulbar dysfunction and aspiration
• Respiratory muscle fatigue
• Autonomic instability triggered by extubation

Prophylactic NIV or HFNC may reduce reintubation rates in high-risk patients.

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