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Hypotensive Transfusion Reaction

Hypotension is a rare complication of blood transfusion. The reported incidence has ranged from 0.04 to 1.3 cases per 10, 000 units issued. Hypotension reactions have been reported to occur with blood products that were leukocyte reduced using negatively charged leukocyte reduction filters. Negatively charged blood filters can activate the kallikrein-kinin system by binding coagulation factor XII. Activated factor XII cleaves prekallikrein to kallikrein, which in turn cleaves high molecular weight kininogen releasing bradykinin. Bradykinin binds to endotherlial cells, causing vasodilation and hypotension.

Normally, bradykinin is rapidly inactivated by angiotensin converting enzyme (ACE). Patients treated with ACE inhibitors are more prone to these reactions. Some patients appear to have an inherent defect in their ability to degrade kinins. Bradykinin binds to receptors on vascular endothelium, causing vasodilation.

Approximately one third of patients with hypotensive reactions have undergoine cardiac surgery. Cardiopulmonary bypass results in increased bradykinin generation and decreased degradation. Bypassing the lungs increases the concentration of bradykinin because the lungs are the major site of bradykinin metabolism. Other extracorporeal circuits such as ECMO and dialysis may also activate the coagulation contact system and interfere with bradykinin degradation.

Hypotensive reactions usually occur within 15 minutes of the start of transfusion. Less commonly they develop between 15 minutes after start and 1 hour after cessation of transfusion. The National Healthcare Safety Network (NHSN) hemovigilance protocol defines hypotensive transfusion reactions as the occurrence of hypotension during or within one hour after cessation of transfusion.

Criteria for adults, 18 years or older, includes:

  • a drop in systolic blood pressure greater than or equal to 30 mm Hg AND
  • Systolic blood pressure less than or equal to 80 mm Hg.

Criterion for infants, children and adolescents (1 year to less than 18years old) is:

  • Greater than 25% drop in systolic blood pressure from baseline.

Criterion for neonates and small infants less than 1 year old and less than 12 kg body weight is greater than 25% drop in blood pressure from baseline value.

All other adverse reactions presenting with hypotension should be excluded before making this diagnosis. These include acute hemolytic transfusion reactions, anaphylaxis, transfusion related acute lung injury (TRALI) and sepsis.

Patients typically respond quickly to cessation of transfusion and supportive treatment.


Arnold DM, et al. Hypotensive transfusion reactions can occur with blood products that are leukocyte reduced before storage, Transfusion September 2004;44:1361-66.

Pagano, MB, et al. Hypotensive transfusion reactions in the era of prestorage leukoreduction. Transfusion 2015;55:1668-74.


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