What is the prevention for a patient with a history of allergic reactions, specifically itchiness all over the body, after a blood transfusion, to minimize the risk of a similar or more severe reaction during future transfusions?

Prevention of Future Allergic Transfusion Reactions After Generalized Itching

Yes, antihistamine premedication before future transfusions is recommended for patients who have experienced a prior allergic transfusion reaction such as generalized itching. 1

Evidence-Based Prevention Strategy

For Patients with Prior Allergic Reactions

Antihistamine premedication is the appropriate preventive measure for patients with documented previous allergic transfusion reactions. 1 The American Journal of Hematology specifically recommends considering antihistamine premedication for patients with prior allergic transfusion reactions. 1

Use second-generation antihistamines rather than first-generation agents. 1 The recommended options include:

• Loratadine 10 mg orally 1
• Cetirizine 10 mg IV or oral 1

Avoid first-generation antihistamines like diphenhydramine when possible because they cause sedation and can potentially exacerbate hypotension, which may mask early warning signs of more serious transfusion reactions. 1

Important Distinction: Not for Routine Use

Do not use antihistamine premedication routinely for all transfusions. 1 The Association of Anaesthetists explicitly recommends against indiscriminate use of antihistamines for transfusion prophylaxis in patients without prior reactions, as routine premedication may delay critical intervention for serious transfusion reactions such as hemolytic reactions or bacterial contamination. 1

No premedication is recommended for first-time transfusions. 1 Antihistamine premedication should only be considered after documented previous reactions or on a case-by-case basis for patients with multiple drug allergies or severe asthma. 1

Evidence Against Routine Premedication

Multiple high-quality studies demonstrate that routine premedication lacks efficacy:

• A 2021 meta-analysis of 22,060 cases found no significant differences in fever, pruritus, rash, airway spasm, or overall transfusion reaction rates between groups receiving anti-allergic agents (dexamethasone, chlorpheniramine, or promethazine) and control groups. 2
• A 2007 systematic review concluded that acetaminophen and diphenhydramine failed to prevent transfusion reactions in the studies performed to date. 3

Routine premedication can cause harm by masking early warning signs of serious reactions and causing immunosuppression in already immunocompromised patients. 1

Additional Prevention Measures

Consider Washed Blood Products

For patients with recurrent or severe allergic reactions despite antihistamine premedication, washed blood products should be considered. 4, 5 Washed platelets have been shown to be effective for preventing allergic transfusion reactions, particularly in patients with multiple food allergies where donor-derived allergens may be the trigger. 6, 5

A case report documented a 13-year-old patient with multiple food allergies who experienced allergic reactions to platelet transfusions despite premedication with antihistamines and corticosteroids, but tolerated washed platelet concentrates without problems. 5

Reserve Corticosteroids Appropriately

Corticosteroids should be reserved for moderate-to-severe reactions, not for routine prevention. 1 The American Journal of Hematology recommends considering corticosteroids only for moderate-to-severe reactions, not as routine premedication. 1

Essential Monitoring Protocol

Vigilant monitoring is critical to detect reactions early, even with premedication. 1 The monitoring protocol should include:

• Baseline vital signs within 60 minutes before starting transfusion 7
• 15-minute check after starting each unit (most critical period, as most reactions manifest during this time) 7
• Continuous monitoring of respiratory rate, as dyspnea and tachypnea are early indicators of serious reactions 1, 7
• Documentation of vital signs before, during, and after transfusion 1
• Final assessment within 60 minutes of completion 7
• Immediate availability of emergency medications including epinephrine 1

Management Algorithm for Future Transfusions

For a patient with prior generalized itching after transfusion:

1. Administer antihistamine premedication (loratadine 10 mg PO or cetirizine 10 mg IV/PO) 30-60 minutes before transfusion 1
2. Ensure emergency equipment and medications are immediately available 1
3. Monitor closely during the first 15 minutes of transfusion 7
4. If allergic symptoms develop despite premedication:
   • Stop the transfusion immediately 4
   • Administer additional antihistamines for symptomatic treatment 4
   • For severe reactions with bronchospasm or hypotension, administer IV epinephrine 50 mcg (0.5 mL of 1:10,000 solution) 4, 8
5. For recurrent reactions despite antihistamine premedication, consider washed blood products for future transfusions 4, 5

Critical Pitfalls to Avoid

Do not restart the transfusion even if mild symptoms improve, as reactions may progress with continued exposure. 7, 4

Do not attribute symptoms to other causes without considering transfusion reaction. 7

Do not use corticosteroids routinely for prevention, as repeated steroid doses can further suppress immunity in already immunocompromised patients. 1