Management of Allergic Reactions During Blood Transfusion

Initial Assessment and Grading

• Simple allergic reactions present with itching and urticaria without respiratory compromise, hypotension, or angioedema, distinguishing them from anaphylaxis which includes bronchospasm, dyspnea/wheezing, hypotension, angioedema, or life‑threatening respiratory/cardiovascular compromise. Oncology Transfusion Guidelines describe these criteria. 1, 2, 3

• Grade 1 reactions are limited to isolated itching; Grade 2 reactions involve moderate urticaria with itching; Grade 3‑4 reactions include severe systemic signs or anaphylaxis. Oncology Transfusion Guidelines provide the grading framework. 1, 2

Management of Grade 1 (Mild) Reactions

• Continue the transfusion at the current rate, monitor vital signs (heart rate, blood pressure, temperature, respiratory rate) every 15 minutes, and document all parameters. Consider an IV antihistamine if itching persists. Oncology Transfusion Guidelines and Association of Anaesthetists recommend this monitoring schedule. 1, 4

Management of Grade 2 (Moderate) Reactions

• Stop or slow the transfusion immediately and keep IV access with normal saline.
• Administer diphenhydramine 50 mg IV (H1 antagonist) and ranitidine 50 mg IV (H2 antagonist).
• Monitor vital signs continuously until symptoms resolve.
• Once stable, restart the transfusion at 50 % of the original rate and titrate to tolerance while maintaining close observation.
• These steps are endorsed by the Oncology Transfusion Guidelines and supported by evidence from the British Society of Anaesthesia. 1, 2, 3, 4

Use of Corticosteroids

• Routine corticosteroids are not recommended for simple allergic reactions; they should be reserved for Grade 3‑4 reactions or confirmed anaphylaxis. The 2025 Association of Anaesthetists guideline advises against indiscriminate steroid use due to potential immunosuppression. 4, 1, 2

Monitoring Requirements Throughout the Transfusion

These monitoring standards are stipulated by the *Association of Anaesthetists**. 4

Criteria for Escalation and Permanent Cessation

• Permanently stop the transfusion if symptoms progress despite treatment, if any signs of anaphylaxis appear (bronchospasm, hypotension, angioedema), or if severe urticaria with systemic manifestations occurs. Oncology Transfusion Guidelines define these escalation triggers. 1, 2, 3

Management of Suspected Anaphylaxis

• Administer epinephrine 0.2–0.5 mg IM (repeat every 5–15 min as needed).
• Give diphenhydramine 50 mg IV plus ranitidine 50 mg IV as adjunctive therapy.
• Provide methylprednisolone 1–2 mg/kg IV every 6 hours.
• These interventions are recommended by the British Society of Anaesthesia for anaphylactic reactions. 1, 2, 3

Prevention for Patients with Prior Allergic Reactions

• Premedicate with an oral or IV antihistamine (e.g., diphenhydramine 25–50 mg or cetirizine 10 mg) 30–60 minutes before the next transfusion.
• Premedication should be targeted to patients with documented prior reactions; it is not routine for all transfusion recipients. Association of Anaesthetists guidance supports this selective approach. 4, 3

Post‑Reaction Observation

• Observe all patients with allergic reactions for a minimum of 6 hours from reaction onset, monitoring for biphasic responses (risk is low for simple allergic reactions). Association of Anaesthetists and British Society of Anaesthesia outline this observation period. 4, 3

Common Pitfalls to Avoid

• Do not use antihistamines as first‑line treatment for anaphylaxis; epinephrine is the only appropriate initial therapy, with antihistamines serving as adjuncts. British Society of Anaesthesia emphasizes this hierarchy. 3

• Do not assume all transfusion reactions are allergic; febrile non‑hemolytic reactions require antipyretics (e.g., paracetamol) rather than antihistamines. This distinction is highlighted by the Association of Anaesthetists. 4