Perioperative Anaphylaxis

Quick Answer

Perioperative anaphylaxis is a life-threatening IgE-mediated hypersensitivity reaction occurring during anaesthesia with an incidence of approximately 1 in 10,000-20,000 procedures. Mortality ranges from 3-9%, with higher rates when diagnosis is delayed. Common triggers include neuromuscular blocking agents (50-60% of cases), antibiotics (particularly penicillins and cephalosporins), latex, and chlorhexidine. Clinical features typically include cardiovascular collapse (most common presenting sign under anaesthesia), bronchospasm, skin changes (erythema, urticaria, angioedema), and hypotension. Immediate management follows ANZCARC/ARC guidelines: stop all suspected agents, call for help, maintain airway with 100% oxygen, administer epinephrine (100 μg IV bolus initially, repeat every 3-5 minutes), and institute fluid resuscitation. Epinephrine is the cornerstone of treatment — early administration is critical for survival. Supportive measures include intravenous fluids (crystalloid bolus 500-1000 mL), bronchodilators for refractory bronchospasm, and advanced cardiac life support if cardiac arrest occurs. Post-event management involves mast cell tryptase sampling (baseline, 1-2 hours, 24 hours), specialist allergy referral, and detailed documentation. Prevention strategies include detailed drug allergy history, latex avoidance protocols, and consideration of drug selection in at-risk patients. Indigenous patients may have higher baseline prevalence of certain allergies and reduced access to specialist allergy services, requiring culturally safe communication and follow-up planning. [1-8]

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Pathophysiology

Mechanisms of Perioperative Anaphylaxis

Anaphylaxis is an acute, potentially life-threatening systemic hypersensitivity reaction mediated by immunological (IgE or IgG) or non-immunological mechanisms. In the perioperative setting, IgE-mediated (Type I) reactions predominate (80-90% of cases), with immediate hypersensitivity causing rapid mast cell and basophil degranulation. [9-12]

IgE-Mediated Anaphylaxis (Type I Hypersensitivity):

1. Sensitisation Phase: Previous exposure to an antigen leads to production of specific IgE antibodies that bind to high-affinity FcεRI receptors on mast cells and basophils
2. Re-exposure: Upon re-exposure, the allergen cross-links IgE molecules on mast cell surfaces
3. Degranulation: This triggers immediate release of preformed mediators (histamine, tryptase, chymase, heparin, proteases) and synthesis of newly formed mediators (prostaglandins, leukotrienes, platelet-activating factor)
4. Clinical Effects: These mediators cause increased vascular permeability, bronchoconstriction, myocardial depression, and vasodilation

Non-IgE-Mediated Anaphylaxis:

• Complement activation (immune complex reactions, radiocontrast agents)
• Direct mast cell activation (opiates, vancomycin, atracurium, mivacurium)
• Kinin generation (ACE inhibitors)
• Pharmacologic idiosyncrasy

Common Perioperative Triggers

Neuromuscular Blocking Agents (NMBA) - 50-60% of cases:

• Succinylcholine (rocuronium is currently most common due to widespread use)
• Rocuronium
• Atracurium, Mivacurium, Vecuronium
• Cross-reactivity: 60-80% cross-reactivity between NMBA due to ammonium groups
• Mechanism: NMBA directly activate mast cells in addition to IgE-mediated pathways

Antibiotics - 15-20% of cases:

• Beta-lactams: Penicillins, cephalosporins
• Vancomycin (often "red man syndrome" - non-IgE mediated)
• Gentamicin, metronidazole

Latex - 2-5% of cases (declining with latex avoidance protocols):

• Risk factors: spina bifida, urological abnormalities, healthcare workers, multiple surgeries
• Cross-reactivity with fruits (banana, avocado, kiwi)

Chlorhexidine - 2-5% of cases (increasing recognition):

• Skin antiseptic preparation
• Impregnated central venous catheters
• Mouthwash
• Gel for urinary catheter insertion

Other Triggers:

• Opioids: Morphine, codeine, meperidine (direct mast cell activation)
• Induction agents: Propofol (egg/soy allergy not a true risk)
• Colloids: Gelatin solutions (Gelofusine) more than starches
• Blood products
• Radiocontrast agents
• Dyes: Patent blue V, methylene blue

Risk Factors for Severe Anaphylaxis

Patient Factors:

• Previous anaphylaxis to same or cross-reactive agent
• Asthma (particularly uncontrolled)
• Cardiovascular disease
• Age > 60 years
• Atopic history
• Female gender

Medication Factors:

• Rapid intravenous bolus administration
• Higher drug doses
• Multiple concurrent allergen exposures

Surgical Factors:

• Cardiac surgery (protamine allergy)
• Major surgery with multiple drug exposures
• Previous reactions during anaesthesia [13-20]

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Clinical Presentation

Diagnostic Criteria (World Allergy Organization)

Anaphylaxis is highly likely when any one of the following three criteria is met:

Criterion 1: Acute onset with skin/mucosal involvement PLUS either:

• Respiratory compromise (dyspnoea, wheeze, stridor, reduced PEF, hypoxaemia)
• Reduced blood pressure or associated symptoms (hypotension, syncope, incontinence)

Criterion 2: Two or more of the following following sudden exposure to likely allergen:

• Skin/mucosal involvement (generalised hives, itch, flush, swelling)
• Respiratory compromise
• Reduced blood pressure or associated symptoms
• Persistent gastrointestinal symptoms (cramps, vomiting)

Criterion 3: Reduced blood pressure after exposure to known allergen

• Infants/children: systolic BP < 70 mmHg or < (2 × age) + 70
• Adults: systolic BP < 90 mmHg or > 30% decrease from baseline

Clinical Features Under Anaesthesia

Cardiovascular Manifestations (Most Common Under General Anaesthesia):

• Hypotension (most frequent initial sign under GA)
  • Sudden drop in blood pressure > 30% from baseline
  • Refractory to standard vasopressor therapy
  • May be accompanied by tachycardia or bradycardia
• Arrhythmias: Sinus tachycardia, bradycardia, heart block
• Cardiac arrest (systolic or PEA)
• Myocardial ischaemia from hypotension or direct mediator effects

Respiratory Manifestations:

• Bronchospasm: Increased airway pressures, wheeze, difficulty ventilating
  • Peak inspiratory pressures > 30 cm H₂O
  • End-tidal CO₂ waveform changes
• Laryngeal oedema: Stridor, difficulty intubating, upper airway obstruction
• Pulmonary oedema: Increased alveolar-arterial gradient, pink frothy sputum

Cutaneous Manifestations (May Be Absent Under GA):

• Erythema: Diffuse flushing, especially of trunk and face
• Urticaria: Raised pruritic wheals (hives)
• Angioedema: Swelling of face, lips, tongue, eyelids, pharynx
• Note: Skin signs are less reliable under anaesthesia due to draping and monitoring equipment

Gastrointestinal Manifestations:

• Nausea, vomiting
• Abdominal cramping (rare under GA)

Time Course

Immediate Reactions (0-10 minutes):

• Most anaphylactic reactions occur within minutes
• Peak severity often within 5-10 minutes
• May recur biphasic (up to 8-12 hours later)

Delayed Reactions (>30 minutes):

• Rare with IgE-mediated anaphylaxis
• More common with non-IgE mechanisms
• May present as prolonged hypotension

Severity Grading (Brown Scale)

Differential Diagnosis

Under Anaesthesia:

• Hypovolaemia from blood loss or third spacing
• Myocardial ischaemia/infarction
• Pulmonary embolism
• Tension pneumothorax
• Local anaesthetic systemic toxicity
• Vagal response (bradycardia, hypotension)
• Pneumoperitoneum effects (laparoscopic surgery)
• Malignant hyperthermia
• Sepsis/endotoxin release
• Drug interactions (MAOI, sympathomimetics)

Key Distinguishing Features:

• Timing: Sudden onset following drug administration
• Refractory hypotension: Does not respond appropriately to fluid/vasopressors
• Bronchospasm: Combined hypotension and bronchospasm is highly suggestive
• Skin changes: Even if partial, any flushing/urticaria points to allergic reaction
• Mast cell tryptase: Elevated (though initial sample may be normal) [21-28]

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Management

Immediate Response (ABC + Stop + Call for Help)

Structured Approach:

1. STOP administration of all anaesthetic agents and drugs
2. CALL FOR HELP — alert theatre team, request senior anaesthetic support
3. Note the time — crucial for tryptase sampling and documentation

Airway and Ventilation:

• Maintain airway with 100% oxygen
• Remove all suspected drugs from IV lines
• Consider repositioning (left lateral with head tilt) to improve venous return
• Intubation if airway compromised by angioedema or respiratory depression
  • Video laryngoscopy preferred (may have better visualisation of oedema)
  • Have smaller endotracheal tubes available (size 6.0-6.5)
  • Have cricothyrotomy equipment ready as backup
• If already intubated:
  • Exclude tube displacement
  • Check for cuff overinflation
  • Suction oropharynx
  • May need to reposition or replace tube if airway oedema present

Breathing:

• Ventilate with 100% oxygen
• Bronchospasm treatment: Salbutamol 5 mg via nebuliser
• Increase FiO₂ to 1.0
• Monitor end-tidal CO₂ and oxygen saturations
• ABG to assess respiratory status and acid-base balance

Circulation - Epinephrine is CRITICAL:

Initial Epinephrine Dose:

• 100 μg IV (0.1 mg = 0.1 mL of 1:1,000 solution)
• OR 0.5-1 mg IM (if IV access delayed)
• Repeat every 3-5 minutes as needed

Epinephrine Dosing Algorithm:

Epinephrine Administration:

• Dilute 1 mg (1 mL of 1:1,000) to 10 mL with saline = 100 μg/mL
• Administer IV bolus over 10-30 seconds
• Do NOT use excessive single doses — risk of arrhythmias
• Continue epinephrine even if initial response

Fluid Resuscitation:

• Crystalloid bolus: 500-1000 mL IV stat (Hartmann's or 0.9% saline)
• Repeat as needed — total may exceed 2-3 L
• Monitor for pulmonary oedema
• Consider invasive arterial and CVP monitoring for ongoing resuscitation

Supportive Measures

Bronchospasm Refractory to Epinephrine:

• Intravenous magnesium sulfate: 2 g IV over 15-20 minutes
• Aminophylline: Loading 5 mg/kg over 20 min, then infusion
• Consider inhalational anaesthetic (sevoflurane) for bronchodilation if already intubated

Persistent Hypotension:

• Norepinephrine infusion: 0.05-0.5 μg/kg/min titrated to effect
• Vasopressin: 40 units IV (single bolus)
• Glucagon: 1-5 mg IV (if patient on beta-blockers)
• Consider intra-aortic balloon pump if severe myocardial dysfunction

Cortisol Administration:

• Hydrocortisone: 200 mg IV
• OR methylprednisolone: 1-2 g IV
• Timing not critical for immediate treatment but important for biphasic reactions

Antihistamines:

• H1 blocker: Promethazine 25 mg IV or diphenhydramine 50 mg IV
• H2 blocker: Ranitidine 50 mg IV or famotidine 20 mg IV
• Secondary to epinephrine — do not delay epinephrine administration

Cardiac Arrest Management

Follow ARC Guidelines with Modifications for Anaphylaxis:

Key Modifications:

1. Epinephrine: Same dose as standard cardiac arrest (1 mg IV)
2. Prolonged resuscitation: May require longer than standard protocols
3. Treat as distributive shock: Massive vasodilation and capillary leak
4. Aggressive fluid loading: May require >5 L crystalloid
5. Consider additional epinephrine doses beyond standard algorithm
6. Vasopressin may be beneficial (40 units IV)

Specific Considerations:

• May present as PEA rather than asystole/VF
• Coronary perfusion may be severely impaired by vasodilation
• Mast cell mediators cause myocardial depression
• ECMO consideration in refractory cases

Post-Event Management

Mast Cell Tryptase Sampling:

Timing of Samples:

1. Baseline: As soon as possible (within 1 hour of reaction)
2. Peak: 1-2 hours post-reaction
3. Late: 24 hours post-reaction (to confirm return to baseline)

Interpretation:

• Elevated if: Peak > baseline + (1.2 × baseline) + 2 ng/mL
• Tryptase normal does not exclude anaphylaxis
• Normal in non-IgE mediated reactions

Monitoring:

• ICU admission for at least 12-24 hours
• Continuous ECG, SpO₂, invasive arterial pressure
• Serial ABGs
• Cardiac biomarkers (troponin)
• Fluid balance
• Monitor for biphasic reaction (occurs in 1-20% of cases)

Documentation:

• Detailed incident report
• Chronology of events
• Drug administration times and doses
• Response to treatment
• Patient outcome
• Tryptase results and analysis

Reporting:

• Hospital incident reporting system
• TGA (Therapeutic Goods Administration) reporting
• State health department incident systems
• Consider reporting to ANZCA for data collection

Follow-up:

• Allergy specialist referral — mandatory for definitive testing
• Provide written information to patient
• Document allergy in medical record with clear warning
• Provide medical alert bracelet
• Plan for future anaesthetics

Patient Communication:

• Explain the event when appropriate
• Provide written information about what happened
• Outline follow-up plan and importance of specialist testing
• Discuss implications for future medical care [29-42]

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Prevention

Preoperative Assessment

Detailed Allergy History:

Essential Questions:

1. What type of reaction occurred?
2. What was the suspected trigger?
3. How long after exposure did the reaction start?
4. What were the specific symptoms?
5. How was the reaction treated?
6. Was the reaction confirmed by allergy testing?
7. Are there other known allergies?

Red Flag Indicators:

• Previous anaphylaxis to any medication
• Multiple drug allergies
• Reaction to neuromuscular blocking agents
• Latex allergy with relevant risk factors
• "Allergy to anaesthesia" (requires clarification)

Risk Stratification:

High Risk:

• Previous anaphylaxis to NMBA or latex
• Multiple drug allergies
• Unexplained severe reactions during previous anaesthesia
• Spina bifida or urological anomalies (latex risk)

Moderate Risk:

• History of urticaria or rash to medications
• Atopic history
• Healthcare workers (latex risk)

Low Risk:

• No known drug allergies
• Previous uneventful anaesthesia

Drug Selection Strategies

Neuromuscular Blocking Agents:

• If previous NMBA allergy: cross-reactivity up to 80%
• Consider non-NMBA techniques if possible
• If NMBA essential: choose different class (e.g., avoid succinylcholine if rocuronium allergy)
• Preoperative allergy testing may guide selection
• Consider sugammadex test dose (some evidence suggests it can bind rocuronium and modify reaction)

Antibiotic Prophylaxis:

• Documented penicillin allergy: use alternative (e.g., clindamycin, vancomycin)
• Cross-reactivity: 1-2% with cephalosporins (higher if previous severe reaction)
• Vancomycin: Administer slowly over 60 minutes to reduce "red man syndrome"
• Consider premedication (antihistamines) for known allergy

Latex Avoidance Protocol:

• Identify high-risk patients preoperatively
• Schedule as first case of day (reduce airborne latex particles)
• Use latex-free equipment and supplies
• Remove all latex-containing devices from theatre
• Notify entire theatre team of latex allergy status
• Document latex allergy in multiple locations (anaesthetic chart, patient record)

Chlorhexidine Awareness:

• Document chlorhexidine allergy
• Use alternative skin antiseptic (povidone-iodine)
• Check all catheters, tubes, and medical devices for chlorhexidine coating
• Inform all team members

Premedication:

• Evidence for premedication to prevent anaphylaxis is limited
• May be considered in high-risk patients:
  • H1 blocker: Cetirizine 10 mg PO 1-2 hours pre-op
  • H2 blocker: Ranitidine 150 mg PO 1-2 hours pre-op
  • Corticosteroid: Prednisolone 50 mg PO 12 hours and 2 hours pre-op
• Never substitute for proper drug avoidance
• Does NOT prevent severe IgE-mediated reactions

Theatre Preparation

Allergy Protocol Implementation:

Preoperative Checklist:

• Allergy status confirmed and documented
• Cross-reactive drugs identified and avoided
• Latex-free protocol activated if indicated
• Emergency equipment checked and immediately available
• Epinephrine readily available (dose calculated)
• Team briefed on allergy status

Emergency Equipment Availability:

• Epinephrine (1:1,000 and 1:10,000 concentrations)
• Intravenous access equipment
• Fluid resuscitation capability
• Advanced airway equipment (video laryngoscope, cricothyrotomy set)
• Bronchodilators (salbutamol nebuliser)
• Invasive monitoring equipment
• Defibrillator

Staff Education:

• Regular training in anaphylaxis recognition
• Simulation of perioperative anaphylaxis scenarios
• Clear communication protocols
• Understanding of local allergy protocols

Documentation and Communication

Clear Documentation:

• Allergy status in prominent locations
• Specific triggers listed
• Reaction severity documented
• Alternative drugs listed
• Patient provided with allergy card/bracelet

Handover Communication:

• Include allergy status in all handovers
• Communicate to PACU staff
• Notify ward team
• Patient education on allergy management

Future Anaesthetic Planning:

• Allergy testing results reviewed preoperatively
• Anaesthetic technique planned based on test results
• Consultant review for high-risk cases
• Consider referral to tertiary centre with expertise in anaesthetic allergy [43-52]

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ANZCA Final Exam Focus

SAQ Patterns

Perioperative anaphylaxis features regularly in ANZCA Final Written Examination. Common SAQ themes include:

Management-Focused Questions:

• "A patient develops sudden hypotension and bronchospasm after rocuronium administration. Describe your management." (2020)
• "Outline the management of perioperative anaphylaxis." (2022)
• "A 45-year-old woman becomes hypotensive with urticaria after induction of anaesthesia. What are your differential diagnoses and immediate management priorities?"

Pathophysiology Questions:

• "Describe the mechanisms of IgE-mediated anaphylaxis."
• "Explain the role of mast cell mediators in anaphylaxis."
• "Compare IgE-mediated and non-IgE-mediated hypersensitivity reactions."

Prevention Questions:

• "How would you assess a patient with a reported penicillin allergy before elective surgery?"
• "What strategies can reduce the risk of perioperative anaphylaxis?"
• "A patient reports a previous reaction to anaesthesia. How would you manage this situation?"

Investigation Questions:

• "Explain the role of mast cell tryptase in diagnosing perioperative anaphylaxis."
• "When and how would you obtain tryptase samples?"
• "What allergy testing would you arrange following perioperative anaphylaxis?"

Marking Scheme Priorities:

• Immediate recognition and structured response (STOP, Help, ABC)
• Epinephrine administration (correct dose and timing)
• Fluid resuscitation
• Supportive measures (bronchodilators, steroids, antihistamines)
• Cardiac arrest management with modifications
• Post-event care (tryptase sampling, monitoring, referral)
• Prevention strategies

Clinical Viva Themes

The Clinical Viva commonly includes anaphylaxis scenarios testing crisis management:

Scenario Types:

• Sudden hypotension under general anaesthesia
• Bronchospasm with difficult ventilation
• Angioedema during airway management
• Cardiac arrest in the perioperative period
• Management of known allergic patient

Examiner Expectations:

• Systematic ABC approach with epinephrine as priority
• Knowledge of differential diagnoses
• Understanding of epinephrine dosing algorithm
• Awareness of modified cardiac arrest management
• Post-event care planning
• Prevention strategies for future anaesthetics

Common Viva Questions:

• "What are the early signs of perioperative anaphylaxis?"
• "What is your initial management of suspected anaphylaxis?"
• "How do you differentiate anaphylaxis from other causes of intraoperative hypotension?"
• "What is the role of tryptase testing?"
• "How would you manage a patient with a known rocuronium allergy?"
• "When would you consider stopping resuscitation efforts?"

Medical Viva Considerations

The Medical Viva may include anaphylaxis within broader discussions:

• Immunological mechanisms of anaphylaxis
• Comparative pharmacology of neuromuscular blocking agents
• Mast cell biology and mediator release
• Cross-reactivity patterns between drug classes
• Evidence for premedication strategies
• Epidemiology of perioperative anaphylaxis

Key Points for Examination Success

1. Epinephrine is the cornerstone — know dosing precisely
2. Stop all drugs — immediate cessation of suspected agents
3. Call for help early — this is a team emergency
4. Differential diagnosis — consider other causes of intraoperative collapse
5. Tryptase sampling — know timing and interpretation
6. Post-event management — ICU admission, monitoring, referral
7. Prevention strategies — risk assessment, drug selection, protocols
8. Indigenous considerations — culturally safe communication and follow-up [53-58]

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Australian Guidelines and Resources

ANZCA Professional Documents

Professional Standards:

• PS09: Sedation and/or Analgesia — mandates emergency equipment availability
• PS07: Pre-Anaesthesia Consultation — allergy assessment requirements
• PS41: Anaesthetic Machine Monitoring Standards
• PS51: Perioperative Patient Safety

Clinical Practice Guidelines:

• ANZCA guidelines on perioperative anaphylaxis management
• Recommendations for drug allergy testing
• Latex avoidance protocols
• Emergency equipment standards

Australian Resuscitation Council (ARC)

ARC Guideline 9.4.2: Anaphylaxis

• Immediate management principles
• Epinephrine administration
• Fluid resuscitation
• Cardiac arrest modifications

Australian Society of Clinical Immunology and Allergy (ASCIA)

ASCIA Guidelines:

• Acute management of anaphylaxis
• EpiPen® and adrenaline autoinjector use
• Drug allergy assessment
• Emergency department anaphylaxis protocols

Therapeutic Goods Administration (TGA)

Drug Safety Updates:

• Perioperative anaphylaxis risk communication
• Chlorhexidine allergy alerts
• Neuromuscular blocker safety information
• Adverse event reporting requirements

State-Based Resources

Each Australian state provides:

• Clinical Emergency Response policies
• MET/Rapid Response activation criteria
• Anaesthetic emergency protocols
• Allergy testing service availability

New Zealand Resources

New Zealand Resuscitation Council:

• Anaphylaxis management guidelines aligned with ARC

MedSafe (NZ Medicines and Medical Devices Safety Authority):

• Drug safety monitoring
• Adverse reaction reporting

Allergy New Zealand:

• Patient resources and support
• Healthcare professional education [59-66]

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Indigenous Health Considerations

Aboriginal and Torres Strait Islander Perspectives

Aboriginal and Torres Strait Islander patients may face unique challenges in the context of perioperative anaphylaxis that require culturally safe approaches:

Communication and Understanding:

Medical terminology and complex immunological concepts may not translate easily across cultures. Allergy explanations should use simple, clear language, with visual aids where possible. Involvement of Aboriginal Health Workers (AHWs) or Aboriginal Hospital Liaison Officers (AHLOs) is crucial for ensuring understanding of:

• What anaphylaxis is and why it occurred
• The importance of allergy testing and follow-up
• What medications to avoid in the future
• How to communicate allergies to other healthcare providers

Language and Cultural Safety:

Many Aboriginal languages may not have direct equivalents for medical concepts. Use interpreters when English is not the primary language. Be aware that:

• Patients may be reluctant to question authority figures (doctors)
• Family decision-making is common — include family in discussions when appropriate
• Eye contact and direct questioning styles may be culturally inappropriate
• Silence may indicate contemplation, not agreement

Higher Prevalence of Risk Factors:

Aboriginal and Torres Strait Islander peoples have higher rates of certain conditions that may complicate anaphylaxis:

• Cardiovascular disease — reduced cardiac reserve, more severe hypotension
• Respiratory conditions (asthma, COPD) — increased bronchospasm risk
• Diabetes mellitus — autonomic dysfunction affecting compensatory responses
• Chronic kidney disease — altered drug handling, fluid management challenges

These comorbidities may require more aggressive resuscitation and closer monitoring.

Access to Specialist Services:

Specialist allergy testing services may be limited in remote communities. Consider:

• Early referral to available allergy services
• Telehealth consultations for specialist review
• Arranging testing when patient attends regional centres for other appointments
• Transport assistance to access testing services
• Providing clear written instructions to local healthcare providers

Medication Storage and Management:

Remote communities may have challenges with:

• Temperature-controlled medication storage (epinephrine)
• Medication access after hours
• Medical emergency response capabilities
• Transfer delays to tertiary centres

These factors influence anaesthetic technique choices and should be documented in the care plan.

Cultural Considerations in Crisis:

In the event of anaphylaxis requiring resuscitation:

• Family presence during resuscitation may be culturally important — facilitate where possible without compromising care
• Decision-making may involve multiple family members
• Gender considerations — some Aboriginal cultures have protocols about who can touch or treat patients
• Spiritual practices may be important during crisis — accommodate where possible
• If death occurs, follow appropriate cultural protocols and involve AHLO for family support

Follow-Up and Documentation:

Ensure comprehensive allergy documentation that:

• Uses clear, non-technical language
• Includes the specific trigger and reaction details
• Provides instructions for future healthcare encounters
• Considers health record transfer to community health services
• Includes culturally appropriate patient education materials

Māori Health Considerations (New Zealand)

For Māori patients, the principles of Te Tiriti o Waitangi and cultural safety apply:

Whānau (Family) Involvement:

• Involve whānau in all decisions about allergy testing and management
• Extended family input in consent and treatment discussions
• Collective decision-making processes

Tikanga (Cultural Protocols):

• Respect cultural protocols around the body and death
• Karakia (prayer) may be requested before or after procedures
• Tangihanga (funeral customs) influence post-mortem protocols
• Consider tapu (sacred) restrictions around body handling

Communication:

• Use Māori Health Workers to ensure cultural safety
• Be aware that some Māori may use health services only when crisis occurs
• Whakawhanaungatanga (building relationships) is essential

Health Literacy:

• Use plain language explanations
• Visual aids and demonstration may be more effective
• Consider health literacy levels in education about allergy management

Access Issues:

• Geographic isolation may limit specialist access
• Financial barriers to specialist services
• Consider local testing options when possible

Documentation:

• Ensure allergy documentation follows the patient to all health encounters
• Provide allergy alerts that are clear for all healthcare providers
• Coordinate with primary care providers for ongoing allergy management [67-76]

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Assessment Content

SAQ Practice Question 1 (20 marks)

Question:

A 42-year-old woman (65 kg) is undergoing laparoscopic cholecystectomy. After induction with propofol 200 mg and rocuronium 50 mg, the patient becomes difficult to ventilate with high airway pressures. Blood pressure drops from 120/75 to 55/30 mmHg, and heart rate increases from 75 to 120 bpm. You notice erythema on the trunk and upper arms.

(a) What is your immediate management? (6 marks)

(b) Describe your management if the patient progresses to cardiac arrest with pulseless electrical activity. (8 marks)

(c) Outline the investigations you would arrange in the postoperative period. (6 marks)

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Model Answer:

(a) Immediate Management (6 marks)

Recognition and Initial Actions [1.5 marks] This clinical presentation — sudden hypotension, bronchospasm (high airway pressures), and erythema immediately after rocuronium administration — is highly suggestive of perioperative anaphylaxis.

Immediate Actions:

1. STOP administration of all anaesthetic agents and drugs immediately
2. CALL FOR HELP — alert theatre team, request senior anaesthetic support
3. Note the time

Epinephrine Administration [2 marks]

• Epinephrine 100 μg IV (0.1 mL of 1:1,000 solution) immediately
• Repeat every 3-5 minutes as needed
• Dilute 1 mg to 10 mL with saline for accurate dosing (100 μg/mL)

Airway and Ventilation [1 mark]

• Administer 100% oxygen
• Suction oropharynx
• Consider need for intubation if airway compromise
• Prepare for difficult airway (may have angioedema)
• Salbutamol nebuliser 5 mg for bronchospasm

Circulatory Support [1.5 marks]

• Establish adequate IV access (multiple large-bore if not already)
• Crystalloid bolus 500-1000 mL stat (Hartmann's or 0.9% saline)
• Repeat as needed
• Monitor response to fluid resuscitation
• Prepare for advanced monitoring (arterial line, CVP)

(b) Management of Cardiac Arrest with PEA (8 marks)

Initiate CPR [1 mark]

• Commence high-quality CPR immediately (30:2 compressions:ventilations)
• Follow ARC Advanced Life Support guidelines

Epinephrine Dosing [1.5 marks]

• Epinephrine 1 mg IV every 3-5 minutes
• Continue standard cardiac arrest epinephrine dosing
• Do NOT reduce dose for anaphylactic cardiac arrest

Aggressive Fluid Resuscitation [1.5 marks]

• Rapid crystalloid administration (may exceed 2-3 L)
• Consider colloid if crystalloid insufficient
• Goal: restore intravascular volume and coronary perfusion
• Monitor for pulmonary oedema

Prolonged Resuscitation [1 mark]

• Continue CPR longer than standard protocols (may require >60 minutes)
• Distributive shock with capillary leak requires prolonged efforts
• Consider ECMO if available and refractory

Vasopressors and Inotropes [1 mark]

• Norepinephrine infusion if ROSC achieved but hypotension persists
• Vasopressin 40 units IV may be considered
• Epinephrine infusion for refractory shock

Reversible Causes [1 mark]

• Anaphylaxis identified as primary cause
• Continue treating with epinephrine, fluids
• Consider other contributing causes (hypoxia, electrolytes, pneumothorax)

ECMO Consideration [1 mark]

• Contact cardiac surgery/ECMO team early if refractory
• ECMO provides circulatory support during recovery
• Bridge to resolution of anaphylactic reaction

(c) Postoperative Investigations (6 marks)

Mast Cell Tryptase Sampling [2.5 marks]

Timing of Samples:

1. Baseline sample: As soon as possible (within 1 hour of reaction)
2. Peak sample: 1-2 hours post-reaction
3. Late sample: 24 hours post-reaction (to confirm return to baseline)

Interpretation:

• Elevated if: peak > baseline + (1.2 × baseline) + 2 ng/mL
• Normal tryptase does NOT exclude anaphylaxis
• Normal in non-IgE mediated reactions

Allergy Specialist Referral [1.5 marks]

• Mandatory referral to allergy specialist
• Skin prick testing and specific IgE testing
• Intradermal testing for neuromuscular blocking agents
• Basophil activation test if required
• Comprehensive allergy assessment and diagnosis

Cardiovascular Investigations [1 mark]

• 12-lead ECG (assess for myocardial ischaemia)
• Troponin (myocardial injury from hypotension/mediator effects)
• Echocardiography if myocardial dysfunction suspected
• Arrhythmia monitoring

Other Investigations [1 mark]

• Arterial blood gas (metabolic acidosis, respiratory status)
• Full blood count (eosinophilia)
• Renal function and electrolytes
• Chest X-ray if pulmonary oedema suspected

Total: 20 marks

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SAQ Practice Question 2 (20 marks)

Question:

(a) Describe the mechanisms by which IgE-mediated anaphylaxis occurs. (8 marks)

(b) List and briefly describe the common triggers of perioperative anaphylaxis. (8 marks)

(c) What strategies can be employed to prevent perioperative anaphylaxis in a patient with a known penicillin allergy? (4 marks)

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Model Answer:

(a) Mechanisms of IgE-Mediated Anaphylaxis (8 marks)

Sensitisation Phase [2 marks]

1. Initial exposure to an antigen (allergen) occurs
2. Antigen-presenting cells process and present the allergen
3. T-helper 2 (Th2) cells activate B cells
4. B cells produce specific IgE antibodies against the allergen
5. IgE binds to high-affinity FcεRI receptors on mast cells and basophils
6. This "primes" the cells for future reactions

Re-exposure Phase [2 marks]

1. Subsequent exposure to the same allergen occurs
2. Allergen cross-links surface-bound IgE molecules
3. This cross-linking triggers mast cell and basophil activation
4. Activation is rapid (within seconds to minutes)

Degranulation and Mediator Release [2 marks]

Preformed Mediators (Immediate Release):

• Histamine: Causes vasodilation, increased vascular permeability, bronchoconstriction
• Tryptase: Diagnostic marker, activates kinin system
• Chymase: Tissue degradation, activates MMPs
• Heparin: Anticoagulant effect
• Proteases: Tissue damage, inflammation

Newly Synthesised Mediators (Release over minutes):

• Leukotrienes (C4, D4, E4): Potent bronchoconstrictors, increase vascular permeability
• Prostaglandin D2: Bronchoconstriction, vasodilation, platelet aggregation
• Platelet-activating factor (PAF): Potent platelet aggregator, increases vascular permeability, bronchoconstriction
• Cytokines (IL-4, IL-5, TNF-α): Inflammatory response amplification

Clinical Effects [2 marks]

• Cardiovascular: Vasodilation → hypotension, capillary leak → tissue oedema, myocardial depression
• Respiratory: Bronchoconstriction → wheeze, airway obstruction, mucosal oedema → stridor
• Cutaneous: Vasodilation → erythema, increased permeability → urticaria, angioedema
• Gastrointestinal: Increased motility, secretion, mucosal oedema

(b) Common Triggers of Perioperative Anaphylaxis (8 marks)

Neuromuscular Blocking Agents [2 marks]

• Incidence: 50-60% of all perioperative anaphylaxis cases
• Common agents: succinylcholine, rocuronium, atracurium, mivacurium, vecuronium
• Mechanism: IgE-mediated (ammonium groups) + direct mast cell activation
• Cross-reactivity: 60-80% between different NMBA due to structural similarities

Antibiotics [1.5 marks]

• Incidence: 15-20% of cases
• Beta-lactams (penicillins, cephalosporins) — most common antibiotic cause
• Vancomycin — often "red man syndrome" (non-IgE mediated)
• Gentamicin, metronidazole — less common
• Mechanism: IgE-mediated (beta-lactams) or direct mast cell activation (vancomycin)

Latex [1 mark]

• Incidence: 2-5% of cases (declining with avoidance protocols)
• Risk factors: spina bifida, urological abnormalities, multiple surgeries, healthcare workers
• Mechanism: IgE-mediated to latex proteins
• Cross-reactivity: Banana, avocado, kiwi

Chlorhexidine [1 mark]

• Incidence: 2-5% of cases (increasingly recognised)
• Uses: Skin antiseptic, impregnated catheters, mouthwash, urinary catheter gel
• Mechanism: IgE-mediated
• May cause severe reactions due to systemic absorption

Colloids [0.5 marks]

• Gelatin solutions (Gelofusine) more than hydroxyethyl starches
• Mechanism: IgE-mediated
• Reactions often severe

Opioids [0.5 marks]

• Morphine, codeine, meperidine
• Mechanism: Direct mast cell activation (non-IgE)
• Usually mild reactions

Other Triggers [0.5 marks]

• Induction agents (propofol — egg/soy allergy NOT true risk)
• Blood products
• Radiocontrast agents
• Dyes (patent blue V, methylene blue)
• Protamine (cardiac surgery)

Drug Interactions [1 mark]

• ACE inhibitors increase risk of severe reactions
• Beta-blockers may mask early tachycardia warning signs
• Aspirin/NSAIDs may lower threshold for mast cell activation

(c) Prevention Strategies for Penicillin Allergy (4 marks)

Detailed Allergy Assessment [1 mark]

• Obtain comprehensive history: What was the reaction? When? How severe?
• Clarify nature of reaction (true allergy vs side effect vs intolerance)
• Document specific symptoms and severity
• Consider timing since reaction

Antibiotic Selection [1.5 marks]

• Avoid penicillins and cephalosporins if history of severe reaction
• Alternative antibiotics:
  • Clindamycin 600 mg IV
  • Vancomycin 15 mg/kg IV (administer slowly over 60 minutes)
  • Azithromycin 500 mg IV/PO
  • Metronidazole 500 mg IV (as per indication)
• Cross-reactivity: If mild rash only, cephalosporin may be considered after specialist review

Premedication [0.5 marks]

• Evidence for premedication to prevent anaphylaxis is limited
• May consider in high-risk patients: H1 blocker (cetirizine) + H2 blocker (ranitidine) + steroid
• Never substitute for proper drug avoidance

Documentation and Communication [1 mark]

• Clearly document penicillin allergy in medical record
• Notify all theatre team members
• Display allergy alert prominently
• Ensure antibiotic prophylaxis is non-penicillin alternative
• Provide patient with allergy card/bracelet
• Document for future surgical encounters

Total: 20 marks

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Viva Scenario (25 marks)

Opening Stem:

You are the consultant anaesthetist supervising a registrar performing an emergency laparoscopic appendicectomy in a 35-year-old man (75 kg). The registrar induces anaesthesia with propofol 250 mg, fentanyl 100 μg, and rocuronium 50 mg. Two minutes later, the patient is difficult to ventilate with peak airway pressures of 45 cm H₂O. Blood pressure is 45/25 mmHg, heart rate 135 bpm. The registrar notices widespread erythema on the patient's chest and arms.

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Expected Viva Progression:

Examiner: What is happening and what is your immediate response?

Candidate Response: [4 marks]

"This presentation — sudden onset of difficult ventilation, severe hypotension, tachycardia, and erythema immediately after rocuronium administration — is highly concerning for perioperative anaphylaxis.

My immediate actions are:

1. STOP the anaesthetic, stop all drug infusions
2. CALL FOR HELP — loudly alert theatre team, request additional anaesthetic support
3. Note the time — crucial for documentation and tryptase sampling

Then: 4. Epinephrine 100 μg IV immediately — dilute 1 mg to 10 mL (0.1 mL) 5. 100% oxygen, prepare for possible intubation if airway compromise 6. Crystalloid bolus 500-1000 mL IV stat 7. Salbutamol 5 mg via nebuliser for bronchospasm 8. Continue epinephrine boluses every 3-5 minutes as needed 9. Monitor response and prepare for advanced monitoring (arterial line)"

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Examiner: Why did you choose 100 μg epinephrine rather than 1 mg?

Candidate Response: [3 marks]

"For a patient with cardiovascular compromise but not in cardiac arrest, 100 μg IV epinephrine is the appropriate initial dose.

Key points:

• The goal is to treat anaphylaxis, not arrest
• 1 mg doses carry risk of severe hypertension, arrhythmias, myocardial ischaemia
• 100 μg can be repeated every 3-5 minutes until response achieved
• Titrate to effect — may need 200-300 μg in severe reactions
• If the patient progresses to cardiac arrest, I would use standard 1 mg doses

The balance is providing adequate α-adrenergic effect (vasoconstriction) and β1 effect (cardiac stimulation) while minimising adverse effects. Under anaesthesia, the epinephrine dose may need to be higher than in awake patients due to the absence of endogenous catecholamine surge."

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Examiner: The patient's blood pressure improves to 80/45 mmHg after the second epinephrine bolus, but airway pressures remain high and you can hear wheeze. What do you do?

Candidate Response: [3 marks]

"I would continue to manage the bronchospasm while maintaining circulatory support:

Bronchospasm Management:

1. Continue 100% oxygen
2. Deepen anaesthesia if not already adequate (may have lightened due to hypotension)
3. Salbutamol 5 mg nebuliser (can repeat)
4. Consider intravenous magnesium sulfate 2 g over 15-20 minutes
   • Acts as calcium channel antagonist → bronchodilation
   • May also have anti-inflammatory effects
5. Consider aminophylline loading dose 5 mg/kg over 20 min if refractory
   • Risk of arrhythmias, especially with recent epinephrine
   • Monitor ECG

Circulatory Support:

• Continue epinephrine boluses if hypotension persists
• Start norepinephrine infusion if hypotension ongoing after fluid resuscitation
• Continue crystalloid infusion (may require >2 L total)
• Consider invasive arterial and CVP monitoring for titration

If airway management becomes difficult:

• Have video laryngoscope ready
• Prepare for possible rapid sequence intubation with airway oedema
• Have cricothyrotomy equipment available"

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Examiner: Despite your efforts, the patient arrests with PEA. How do you modify standard ACLS management?

Candidate Response: [5 marks]

"For anaphylactic cardiac arrest, I would follow ARC guidelines with specific modifications:

Standard ALS applies with modifications:

1. High-quality CPR — compressions, ventilation, defibrillation for VF/VT if develops

2. Epinephrine dosing:

   • 1 mg IV every 3-5 minutes (standard cardiac arrest dose)
   • Do NOT reduce dose for anaphylaxis
   • May need prolonged duration of resuscitation

3. Aggressive fluid loading:

   • Rapid crystalloid administration (Hartmann's or 0.9% saline)
   • May require 3-5 L or more
   • Distributive shock with massive capillary leak
   • Monitor for pulmonary oedema (listen for crackles, check ETT cuff leak)

4. Consider additional therapies:

   • Vasopressin 40 units IV as single bolus (may provide better vasopressor effect)
   • Glucagon 1-5 mg IV if patient on beta-blockers
   • Norepinephrine infusion if ROSC achieved but hypotension persists

5. Prolonged resuscitation:

   • Continue CPR longer than standard protocols
   • May require >60 minutes
   • Consider ECMO if available and patient remains refractory
   • Contact cardiac surgery/ECMO team early

6. Treat reversible causes:

   • Anaphylaxis identified as primary cause
   • Continue epinephrine, fluids
   • Consider other contributing causes (hypoxia, tension pneumothorax, etc.)

The key is massive vasodilation and capillary leak causing distributive shock — requires aggressive volume loading and vasopressor support beyond standard cardiac arrest protocols."

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Examiner: After 35 minutes of CPR, the patient achieves ROSC. What is your post-event management?

Candidate Response: [4 marks]

"Post-resuscitation care involves:

Immediate ICU Admission:

• Mandatory admission to intensive care
• Invasive arterial pressure monitoring
• Central venous access for ongoing resuscitation
• Continuous ECG monitoring

Mast Cell Tryptase Sampling:

1. Baseline sample: Draw now (within 1 hour of event)
2. Peak sample: 1-2 hours post-reaction
3. Late sample: 24 hours post-reaction (to confirm return to baseline)

Supportive Care:

• Continue norepinephrine infusion if hypotension persists
• Maintain euvolaemia
• Monitor for pulmonary oedema (capillary leak)
• Ventilatory support if respiratory compromise
• Oxygen therapy

Investigations:

• 12-lead ECG (myocardial ischaemia)
• Cardiac biomarkers (troponin)
• Arterial blood gas
• Chest X-ray
• Renal function, electrolytes
• Full blood count

Documentation:

• Detailed incident report with timeline
• Drug doses and administration times
• Response to treatment
• Tryptase results
• Patient outcome

Follow-Up Planning:

• Allergy specialist referral — mandatory
• Skin testing and specific IgE testing post-discharge
• Provide patient with written information
• Document allergy in medical record with warning
• Provide medical alert bracelet
• Plan for future anaesthetics"

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Examiner: What specific allergies would you need to test for?

Candidate Response: [3 marks]

"I would arrange comprehensive allergy testing to identify the specific trigger:

Priority Testing:

1. Neuromuscular Blocking Agents:

   • Rocuronium (suspected trigger)
   • All other NMBAs: succinylcholine, atracurium, mivacurium, vecuronium, cisatracurium, pancuronium
   • Cross-reactivity testing is essential (60-80% between NMBAs)

2. Antibiotics:

   • Any antibiotics administered or planned for prophylaxis
   • Especially beta-lactams (penicillins, cephalosporins)
   • Vancomycin if given

3. Latex:

   • If any latex-containing equipment used
   • Skin prick testing for latex allergy

4. Chlorhexidine:

   • If used for skin preparation
   • Chlorhexidine-specific IgE testing

5. Other drugs administered:

   • Propofol
   • Fentanyl
   • Any induction agents or analgesics

Testing Methods:

• Skin prick testing: First-line, safe, rapid results
• Intradermal testing: More sensitive for NMBA antibiotics
• Specific IgE (RAST): Blood test for some allergens
• Basophil activation test: If skin testing inconclusive

Timing:

• Usually performed 4-6 weeks post-event
• Allows immune system to return to baseline
• Performed by allergy specialist in controlled setting with resuscitation equipment available

The results will guide drug selection for future anaesthetics and provide clear documentation for the patient's allergy profile."

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Examiner: The patient is discharged after 48 hours. How do you prepare for his future anaesthetics?

Candidate Response: [3 marks]

"Preparation for future anaesthetics involves:

Documentation:

1. Prominent allergy documentation in medical record
2. Include specific trigger(s) identified
3. List safe alternative drugs
4. Cross-reactivity information
5. Medical alert bracelet provided

Preoperative Planning:

1. Review allergy testing results thoroughly
2. Plan anaesthetic technique avoiding trigger(s)
3. Consider consultant-level anaesthesia for future cases
4. Review with anaesthetic department or allergy clinic

Surgical Team Briefing:

1. Communicate allergy status to surgical team
2. Ensure antibiotic prophylaxis is non-allergenic
3. Review theatre protocols for allergy

Theatre Preparation:

1. Consider first case of day scheduling
2. Ensure all equipment and supplies are safe
3. Emergency equipment immediately available
4. Brief entire theatre team

Patient Communication:

1. Explain the allergy and its implications
2. Provide written information about the allergy
3. Instruct patient to inform all future healthcare providers
4. Encourage wearing medical alert bracelet

System-Level Preparation:

1. Update hospital allergy database
2. Consider formal allergy alert system
3. Document in anaesthetic record for future reference
4. Consider creating individualised care plan

The goal is comprehensive preparation that minimises risk of recurrence while providing patient-centred care."

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Total: 25 marks

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