What is the management for hives (urticaria) after anesthesia?

Management of Hives (Urticaria) After Anesthesia

For isolated hives after anesthesia without systemic symptoms, administer chlorphenamine 10 mg IV or IM slowly for adults (5 mg for children 6-12 years, 2.5 mg for 6 months-6 years) and observe closely for progression to anaphylaxis. 1

Immediate Assessment and Triage

Determine if this is isolated urticaria or part of systemic anaphylaxis:

• Isolated hives alone (no hypotension, no bronchospasm, no angioedema) suggest a less severe reaction that may represent non-specific histamine release rather than true anaphylaxis 1
• Hives plus any of the following indicate anaphylaxis requiring immediate epinephrine: hypotension (>30 mmHg drop in MAP), bronchospasm, angioedema, or cardiovascular collapse 1
• Cutaneous signs are present in 72% of allergic anaphylaxis cases, but their absence does not exclude anaphylaxis 1

Management Based on Severity

For Isolated Urticaria (No Systemic Symptoms)

Primary treatment:

• Administer chlorphenamine (H1-antihistamine) 10 mg IV or IM slowly for adults over 12 years 1
• Pediatric dosing: 5 mg (6-12 years), 2.5 mg (6 months-6 years), 250 µg/kg (<6 months) 1
• Do NOT administer epinephrine for isolated Grade I reactions (cutaneous signs only without systemic involvement) 1

Secondary measures:

• Consider hydrocortisone 200 mg IV slowly for adults if symptoms are moderate or persistent 1, 2
• Pediatric hydrocortisone dosing: 100 mg (6-12 years), 50 mg (6 months-6 years), 25 mg (<6 months) 1
• Remove all potential causative agents including IV colloids, latex, and chlorhexidine 1

For Urticaria With Systemic Symptoms (Anaphylaxis)

Epinephrine is mandatory and must be given immediately:

• Initial dose: 50 µg IV (0.5 mL of 1:10,000 solution) for adults 1
• Repeat every 5-15 minutes if hypotension or bronchospasm persists 1, 3
• Consider continuous IV epinephrine infusion if multiple boluses are required 1

Concurrent management:

• Use ABC approach (Airway, Breathing, Circulation) 1
• Administer 100% oxygen and secure airway if needed 1
• Elevate legs for hypotension 1
• Rapid IV fluid resuscitation with 0.9% saline or lactated Ringer's at high rates (10-20 mL/kg boluses) 1, 3
• Add chlorphenamine 10 mg IV and hydrocortisone 200 mg IV as adjunctive therapy 1

Critical Pitfalls to Avoid

Common diagnostic errors:

• Isolated hypotension during anesthesia occurs in 10% of anaphylaxis cases and may be the only sign, especially with neuraxial blockade 1
• Bradycardia (not tachycardia) occurs in approximately 10% of allergic anaphylaxis during anesthesia 1
• Symptoms may be delayed up to one hour with latex, antibiotics, IV colloids, or surgical instrument disinfectants 1

Treatment errors:

• Never delay epinephrine to give antihistamines first if any systemic symptoms are present 3, 4
• Antihistamines alone do not reverse life-threatening cardiovascular or respiratory manifestations 3
• Opioids commonly cause non-specific histamine release with isolated flushing/urticaria that does not require epinephrine 1, 5

Observation and Monitoring

All patients with urticaria after anesthesia require:

• Minimum 4-6 hours observation even if symptoms resolve quickly 3
• Extended 12-hour observation if epinephrine was administered or symptoms were severe 3
• Continuous monitoring for biphasic reactions (occur in up to 20% of cases) 3

Mandatory Follow-Up Investigation

Every patient with widespread urticaria, flushing, or suspected anaphylaxis must be referred to a specialist Allergy/Immunology center 1

Required documentation for referral:

• Legible copy of anesthetic record and recovery room chart 1
• All drug charts with exact timing of administration relative to symptom onset 1, 2
• Description of reaction severity and time of onset after induction 1
• Serum tryptase levels (if obtained during reaction and baseline) 1

Skin testing should be performed:

• As soon as patient has fully recovered clinically 1
• After antihistamine effects have worn off (discontinue antihistamines several days before testing) 1
• To identify specific causative agents including neuromuscular blockers, antibiotics, latex, and other perioperative drugs 1

Special Considerations

Most common causative agents in order of frequency:

• Neuromuscular blocking agents (most common) 1
• Natural rubber latex (second most common, often delayed 15-30 minutes) 1, 6
• Hypnotic induction agents (third most common) 1
• Antibiotics (especially β-lactams and vancomycin) 1
• IV colloids including hydroxyethyl starch 1, 7

Cross-reactivity concerns:

• Patients with latex allergy may react to fruits (banana, avocado, kiwi) 6, 8
• History of cutaneous sensitivity to cosmetics or quaternary ammonium compounds raises caution for muscle relaxant reactions 1