What is the recommended management for urticaria in the postoperative (post-op) period?

Management of Postoperative Urticaria

For isolated postoperative urticaria without systemic symptoms, start with a second-generation non-sedating H1 antihistamine such as cetirizine, fexofenadine, or loratadine at standard dosing, and escalate up to 4 times the standard dose if symptoms persist after 2-4 weeks. 1, 2

Immediate Assessment and Differential Diagnosis

When urticaria appears postoperatively, first distinguish it from perioperative anaphylaxis:

• Grade I reactions (isolated skin/mucosal signs with generalized erythema or urticaria) do not require epinephrine 3
• If hypotension, bronchospasm, or angioedema involving the airway are present, this is anaphylaxis requiring immediate intramuscular epinephrine—never rely on antihistamines or corticosteroids alone 3, 1
• Isolated urticaria with normal tryptase levels (compared to baseline) suggests non-allergic etiology and may not require extensive allergy investigation 3

First-Line Treatment Algorithm

Start with second-generation H1 antihistamines:

• Preferred agents: cetirizine, desloratadine, fexofenadine, levocetirizine, loratadine, or mizolastine 1, 2
• Cetirizine reaches maximum concentration fastest, making it advantageous when rapid symptom relief is needed 1
• Offer at least two different non-sedating antihistamines to trial, as individual responses vary significantly 1, 2
• Use antihistamines on a regular scheduled basis, not just as needed after hives appear 4

Dose Escalation Strategy

If symptoms persist after 2-4 weeks on standard dosing:

• Increase the dose up to 4 times the standard dose before adding other therapies 1, 5, 2
• This approach has demonstrated superior efficacy, with response rates increasing progressively from 1 to 2 to 3 to 4 tablets daily 6

Adjunctive Measures for Resistant Cases

For inadequate response to high-dose antihistamines:

• Consider adding H2 antihistamines (e.g., ranitidine or cimetidine) in combination with H1 antihistamines 3
• First-generation sedating antihistamines (hydroxyzine) may be added at night for additional symptom control and to aid sleep 2
• Avoid first-generation antihistamines during acute reactions as they can exacerbate hypotension and tachycardia 1

Role of Corticosteroids

Corticosteroids should be restricted to short courses (3-10 days) for severe acute urticaria only:

• Use oral prednisone 40 mg daily or equivalent, tapering to the lowest effective alternate-day dose 4, 7
• Never use corticosteroids for chronic management due to cumulative toxicity that is dose and time dependent 7
• Corticosteroids have slow onset of action (work by inhibiting gene expression) and are ineffective for acute symptom relief 1

Special Consideration: Postoperative Pruritus Without Visible Urticaria

If the patient has generalized itching without visible wheals (postoperative pruritus):

• Consider diclofenac 100 mg given rectally 3
• If opioid-induced, consider naltrexone, methylnaltrexone, ondansetron, droperidol, mirtazapine, or gabapentin 3

Trigger Identification and Avoidance

Identify and minimize aggravating factors:

• Common triggers: overheating, stress, alcohol, aspirin, NSAIDs, codeine 1, 2
• Avoid NSAIDs in aspirin-sensitive patients 2
• Review all perioperative medications for potential drug-induced urticaria 3
• Consider non-specific histamine release from opioids, which may be reduced with antihistamine pretreatment in future procedures 3

Renal and Hepatic Dosing Adjustments

In moderate renal impairment:

• Avoid acrivastine 1, 2
• Halve the dose of cetirizine, levocetirizine, and hydroxyzine 1, 2

In hepatic impairment:

• Avoid mizolastine in significant hepatic impairment 1, 2
• Avoid hydroxyzine in severe liver disease 1, 2

Prognosis and Expected Course

For acute postoperative urticaria:

• Approximately 50% of patients with wheals alone will be clear by 6 months 2
• Patients with both wheals and angioedema have a poorer outlook, with over 50% still having active disease after 5 years 2
• Over 40% of patients with urticaria show good response to antihistamines 3

Critical Pitfalls to Avoid

• Never use antihistamines or corticosteroids in place of epinephrine for anaphylaxis—antihistamines take 30-120 minutes to reach peak plasma concentrations and lack vasoconstrictive, bronchodilatory, and mast cell stabilization properties 1
• Do not confuse isolated urticaria with perioperative anaphylaxis; check for systemic symptoms (hypotension, bronchospasm, angioedema) 3
• Do not perform extensive allergy workup for isolated urticaria with normal tryptase levels 3

Incidence

Postoperative urticaria as an isolated finding (without systemic anaphylaxis) is relatively common, though exact incidence data specific to the postoperative period is limited in the provided evidence. Perioperative allergic reactions occur around the time of induction of anaesthesia, with isolated skin symptoms (Grade I reactions) being the mildest presentation 3.