What is the management of a severe allergic reaction post spinal anesthesia?

Management of Severe Allergic Reaction Post Spinal Anesthesia

Immediately administer intravenous epinephrine as the first-line treatment, with initial dosing based on reaction severity: 50 mcg IV for Grade II reactions, 100-200 mcg IV for Grade III life-threatening reactions, or 1 mg IV for cardiac arrest, followed by aggressive crystalloid resuscitation. 1

Immediate Recognition and Initial Actions

Stop all potential causative agents immediately including any ongoing infusions, remove latex if present, and maintain anesthesia with inhalational agents only if needed. 1

• Call for help and note the time of reaction onset 1
• Secure airway with 100% oxygen; intubate if necessary 1
• Elevate legs if hypotension is present 1
• Establish or maintain IV access urgently 1

Clinical features typically appear within minutes but may be delayed up to one hour, particularly with local anesthetics, latex, or antiseptics. 1 Hypotension may be the sole presenting feature in approximately 10% of cases, especially with neuraxial blockade. 1 Cutaneous signs are absent in up to 28% of allergic anaphylaxis cases during anesthesia, so their absence does not exclude the diagnosis. 1

Epinephrine Dosing by Reaction Severity

Grade II Reactions (Moderate: measurable but not life-threatening hypotension or bronchospasm)

• Initial dose: 20 mcg IV bolus 1
• Escalate to 50 mcg IV at 2 minutes if inadequate response 1
• If IV access is lost or unavailable: 300 mcg IM into anterolateral thigh 1

Grade III Reactions (Life-threatening hypotension or bronchospasm)

• Initial dose: 50 mcg IV if no other vasopressors given 1
• Escalate to 100 mcg IV if unresponsive to other vasopressors 1
• Further escalate to 200 mcg IV at 2 minutes if still unresponsive 1

Grade IV Reactions (Cardiac or respiratory arrest)

• Follow advanced life support guidelines with 1 mg IV epinephrine 1
• Initiate cardiac compressions immediately for inadequate cardiac output 1
• Consider compressions for systolic BP <50 mmHg or end-tidal CO₂ <3 kPa (20 mmHg) 1

Common pitfall: The 2009 guidelines recommended starting with 50 mcg for all reactions 1, but the more recent 2019 international consensus provides severity-graded dosing that allows for more precise titration in moderate reactions while maintaining aggressive treatment for severe cases. 1

Aggressive Fluid Resuscitation

• Grade II reactions: 500 mL crystalloid rapid bolus, repeat as needed 1
• Grade III reactions: 1 L crystalloid rapid bolus, repeat as needed 1
• Escalate up to 20-30 mL/kg for refractory cases 1
• Use balanced salt solutions or 0.9% NaCl 1

Large volumes are frequently required due to massive vasodilation and capillary leak. 1

Management of Refractory Anaphylaxis (Inadequate Response After 10 Minutes)

For Persistent Hypotension:

• Double the epinephrine bolus dose 1
• Start epinephrine infusion at 0.05-0.1 mcg/kg/min peripherally 1
• Consider 500 mcg IM epinephrine bolus while preparing infusion 1
• Add norepinephrine infusion (0.05-0.5 mcg/kg/min), phenylephrine, or metaraminol 1
• Add vasopressin 1-2 IU bolus with or without infusion (2 units/hour) 1
• For patients on beta-blockers: add IV glucagon 1-2 mg 1
• Consider extracorporeal life support where available 1

For Persistent Bronchospasm/High Airway Pressures:

• Administer inhaled bronchodilators (salbutamol) or volatile anesthetics 1
• Consider IV bronchodilators: ketamine or salbutamol 1
• IV aminophylline or magnesium sulfate may be considered 1

Critical note: Sugammadex has no immediate role in anaphylaxis resuscitation. 1

Secondary Medications (After Adequate Epinephrine and Fluid Resuscitation)

Antihistamines and corticosteroids are NOT priorities and should only be given after adequate epinephrine and fluid resuscitation. 1

• Chlorphenamine 10 mg IV (or locally available IV antihistamine formulation) 1
• Hydrocortisone 200 mg IV 1
• Do NOT use IV promethazine - it is not appropriate for managing anaphylaxis 1

Diagnostic Testing

Obtain serum mast cell tryptase levels at specific time points: 1

• First sample: at 1 hour after symptom onset (do not delay resuscitation to obtain) 1
• Second sample: 2-4 hours after symptom onset 1
• Third sample: 24 hours or later for baseline comparison 1

An increase >1.2 × baseline + 2 μg/L confirms mast cell degranulation. 2 Some individuals have elevated baseline tryptase, making the baseline sample essential for interpretation. 1

Observation and Monitoring

• Observe in monitored area for minimum 6 hours or until stable and symptoms regressing 1
• The risk of biphasic reactions is likely low 1
• Transfer to appropriate critical care area 1

Documentation and Follow-Up

Meticulous documentation is essential: 2, 3

• Record exact timing of all drug/substance exposures before reaction
• Document symptom onset time and progression
• List all treatments given with times and doses
• Note response to each intervention

All patients with Grade II-IV reactions must be referred to specialized allergy clinics for formal investigation 4-6 weeks post-reaction. 1, 2, 3 Testing should include skin testing, specific IgE antibody testing, and potentially drug provocation testing in specialized centers. 1

Provide written information to the patient detailing all exposures to avoid until formal allergy testing is completed. 1 The identified culprit must be strictly avoided in future, with all healthcare personnel informed to prevent accidental re-exposure. 1

Common culprits in spinal anesthesia context: Local anesthetics (particularly dibucaine) 4, chlorhexidine, latex, antibiotics, and adhesive materials. 1, 2 While anaphylaxis to amide local anesthetics is rare, it has been documented. 4