How should urticaria that develops during a blood transfusion be managed?

Management of Urticaria During Blood Transfusion

Stop the transfusion immediately, maintain IV access with normal saline, and administer a second-generation antihistamine such as cetirizine 10 mg IV/PO or loratadine 10 mg PO for symptomatic treatment. 1, 2

Immediate Actions When Urticaria Develops

Stop the transfusion immediately at the first sign of urticaria to prevent progression to more severe reactions. 2, 3

• Maintain IV access with normal saline at a keep-vein-open (KVO) rate to preserve venous access for medication administration. 1
• Notify the blood bank and physician immediately, as this is a reportable transfusion reaction. 3, 4
• Perform a rapid assessment to exclude anaphylaxis by checking for hypotension (systolic BP <90 mmHg or ≥30 mmHg drop from baseline), respiratory compromise (dyspnea, wheezing, oxygen saturation <92%), or angioedema of the tongue/airway. 1, 2

Pharmacologic Management of Isolated Urticaria

Administer a second-generation antihistamine as first-line treatment for urticaria without systemic symptoms. 1, 2

• Preferred agents: Cetirizine 10 mg IV or PO, or loratadine 10 mg PO. 1
• Avoid first-generation antihistamines (diphenhydramine) as they can mask early warning signs of serious reactions, cause sedation, and potentially worsen hemodynamic status. 1, 2
• Monitor the patient for at least 15 minutes after antihistamine administration to ensure symptom resolution. 1

When to Escalate Treatment

If urticaria is accompanied by any of the following red flags, treat as moderate-to-severe hypersensitivity or anaphylaxis:

• Transient cough, shortness of breath, or bronchospasm 1
• Tachycardia or hypotension (≥30 mmHg drop in systolic BP) 1
• Chest tightness, back pain, or gastrointestinal symptoms 1
• Angioedema, particularly of the tongue or airway 1, 2

For moderate reactions: Add IV corticosteroid (hydrocortisone 100-500 mg IV) and consider H2 antagonist (famotidine 20 mg IV). 1

For severe reactions/anaphylaxis: Immediately administer epinephrine 0.3 mg IM (1 mg/mL solution) into the anterolateral mid-thigh, call emergency services, position patient supine if hypotensive, administer NS bolus 1000-2000 mL, and provide supplemental oxygen. 1, 2

Decision to Resume or Discontinue Transfusion

If urticaria completely resolves after antihistamine therapy and no systemic symptoms develop:

• Consider restarting the transfusion at 50% of the initial infusion rate after approximately 15 minutes of symptom resolution. 1, 2
• Monitor continuously for recurrence of symptoms during the remainder of the transfusion. 2
• If symptoms recur, permanently discontinue the transfusion. 1

If urticaria persists or worsens despite antihistamine treatment, do not resume the transfusion and investigate for other causes. 1, 3

Prevention for Future Transfusions

Routine premedication is NOT recommended for patients without prior transfusion reactions, as it may mask early warning signs of serious reactions and lacks efficacy. 2

For patients with documented prior allergic transfusion reactions:

• Consider premedication with a second-generation antihistamine (cetirizine 10 mg PO or loratadine 10 mg PO) 30-60 minutes before transfusion. 5, 2
• Start the infusion at a slower rate (50% of standard rate) and monitor for 15 minutes before increasing to full rate. 5
• Document the reaction in the patient's transfusion record to guide future management. 3

Common Pitfalls to Avoid

Do not use diphenhydramine routinely as it provides no advantage over second-generation antihistamines and causes problematic sedation that can obscure assessment of serious reactions. 1, 2

Do not administer corticosteroids for mild urticaria alone, as they are not indicated for isolated skin reactions and may cause unnecessary immunosuppression. 2, 3

Do not continue the transfusion while evaluating urticaria, even if symptoms seem mild, as progression to anaphylaxis can occur rapidly. 2, 4