Prevention of Allergic Transfusion Reactions

Evidence Against Routine Premedication

• The Association of Anaesthetists recommends against the indiscriminate use of antihistamines and steroids for transfusion prophylaxis, due to lack of efficacy and potential harm, due to the risk of masking early warning signs of serious transfusion reactions and immunosuppression concerns in immunocompromised patients 1, 2
• Routine premedication may delay critical intervention for serious transfusion reactions, such as hemolytic reactions or bacterial contamination, and repeated steroid doses can further suppress immunity in already immunocompromised patients 1, 2

Recommended Prevention Strategy

• The Association of Anaesthetists suggests a personalized risk assessment approach, where no premedication is recommended for first-time transfusions, and antihistamine premedication is considered only after documented previous reactions, or on a case-by-case basis for patients with multiple drug allergies or severe asthma 1, 2, 3
• The American Journal of Hematology recommends considering antihistamine premedication for patients with prior allergic transfusion reactions, and reserving corticosteroids for moderate-to-severe reactions 3

Optimal Monitoring Protocol

• The Association of Anaesthetists recommends vigilant monitoring to detect reactions early, including continuous monitoring of respiratory rate, and documentation of vital signs before, during, and after transfusion, as well as immediate availability of emergency medications 1, 2
• Monitoring should include checking for early warning signs such as dyspnea and tachypnea, and documenting vital signs at regular intervals, to ensure prompt intervention in case of a reaction 1, 2

Management When Reactions Occur

• The Association of Anaesthetists recommends stopping the transfusion immediately if allergic symptoms develop, administering antihistamines for symptomatic treatment, and reserving corticosteroids for moderate-to-severe reactions, while avoiding first-generation antihistamines like diphenhydramine when possible 1, 2, 3, 4

Prevention of Future Allergic Transfusion Reactions

Recommended Prevention Strategies

• The American Journal of Hematology recommends considering antihistamine premedication for patients with prior allergic transfusion reactions, and using second-generation antihistamines like loratadine 10 mg orally or cetirizine 10 mg IV/oral, rather than first-generation antihistamines like diphenhydramine, which can cause sedation and potentially exacerbate hypotension 5, 6
• The American Society of Anesthesiologists, as referenced in Anesthesiology (ASA), suggests avoiding first-generation antihistamines when possible due to side effects 5, 6

Prevention of Allergic Transfusion Reactions

Evidence-Based Prevention Strategy

• Rapid infusion of blood products increases reaction severity, and slower infusion rates are protective, not harmful, according to the Journal of Allergy and Clinical Immunology 7
• Fast pushing the blood bag is dangerous and contraindicated, as it can increase reaction severity, as stated in the Annals of Oncology 8

Optimal Management

• Plasma and platelet products carry a higher risk of allergic reactions (1:591 to 1:2,184 units) compared to red blood cells, although the specific citation for this fact is not provided, it is implied to be related to 8 or 7, however since there is no direct citation it will not be included.

Management of Allergic Reactions to Plasma Transfusion

Assessment of Possible Anaphylaxis

• When itching occurs during or shortly after plasma transfusion, clinicians should evaluate for anaphylaxis by checking for (1) hypotension (systolic BP < 90 mmHg or a ≥30 mmHg drop from baseline), (2) respiratory compromise such as dyspnea, wheezing, or oxygen saturation < 92 %, and (3) additional skin findings like urticaria, angio‑edema, or generalized flushing, and they should document all vital signs. 9

Immediate Treatment of Confirmed Anaphylaxis

• If anaphylaxis is identified, administer epinephrine 0.01 mg/kg intramuscularly (maximum 0.5 mL of a 1 mg/mL solution) into the lateral thigh immediately; the dose may be repeated every 5–15 minutes if there is no clinical response. 9
• Position the patient in Trendelenburg if hypotensive or upright if experiencing respiratory distress, provide supplemental oxygen as needed, and summon emergency medical assistance. 9

Post‑Reaction Transfusion Management

• When itching resolves completely after antihistamine therapy and no anaphylactic signs persist, the plasma transfusion may be re‑started cautiously at a slower infusion rate, with continuous monitoring for the remainder of the transfusion. 9

Escalation Criteria (Red Flags)

• Development of hypotension, respiratory distress, or multi‑system involvement during or after transfusion mandates immediate epinephrine administration as described above. 9

Strength of evidence: not explicitly graded in the source.

Management of Urticaria During Blood Transfusion

Immediate Actions

• Stop the transfusion at the first sign of urticaria, keep the IV line open with normal saline at a keep‑vein‑open rate, and give a second‑generation antihistamine (cetirizine 10 mg IV/PO or loratadine 10 mg PO) for symptom relief. 10
• Perform a rapid assessment for anaphylaxis by checking for hypotension (systolic < 90 mmHg or ≥30 mmHg drop), respiratory compromise (dyspnea, wheezing, oxygen saturation < 92 %), or angioedema of the tongue/airway. 10

Pharmacologic Management of Isolated Urticaria

• Use a second‑generation antihistamine as first‑line therapy for urticaria without systemic signs. 11
• Preferred agents are cetirizine 10 mg IV or PO and loratadine 10 mg PO. 11
• Avoid first‑generation antihistamines such as diphenhydramine because they may mask early warning signs, cause sedation, and potentially worsen hemodynamics. 11
• Observe the patient for at least 15 minutes after antihistamine administration to confirm symptom resolution. 11

Criteria for Escalation to Moderate or Severe Reaction

• Presence of any red‑flag symptom—transient cough, shortness of breath, bronchospasm; tachycardia or hypotension; chest tightness, back pain, gastrointestinal upset; or angioedema of the tongue/airway—requires treatment as a moderate‑to‑severe hypersensitivity reaction or anaphylaxis. 11

Treatment of Moderate Reactions

• Add intravenous hydrocortisone 100–500 mg and consider an H₂‑receptor antagonist (famotidine 20 mg IV). 11

Treatment of Severe Reactions / Anaphylaxis

• Administer epinephrine 0.3 mg IM (1 mg/mL) into the anterolateral mid‑thigh, call emergency services, place the patient supine if hypotensive, give a normal‑saline bolus of 1–2 L, and provide supplemental oxygen. 11

Decision to Resume or Discontinue Transfusion

• If urticaria fully resolves after antihistamine therapy and no systemic symptoms develop, the transfusion may be restarted at 50 % of the original rate after approximately 15 minutes of observation. 11
• If urticaria recurs, the transfusion should be permanently discontinued. 11
• Persistent or worsening urticaria despite antihistamine treatment mandates cessation of the transfusion and further investigation of alternative causes. 10

Common Pitfalls to Avoid

• Do not use diphenhydramine routinely; it offers no benefit over second‑generation antihistamines and its sedative effect can obscure assessment of serious reactions. 11