Clinical Presentation - Isolated Hypotensive

Symptoms typically appear within minutes of initiation of transfusion. Hypotension may be the only symptom and rapid response is seen once the transfusion is stopped. Other symptoms, if present, are minor.

Signs and symptoms include:

Primary

• A hypotensive episode is defined as a drop in systolic and/or diastolic blood pressure of greater than 30 mm Hg.

Secondary (±)

• Dyspnea
• Urticaria
• Flushing
• Pruritis
• Diarrhea
• Nausea

Mechanism

Thought to involve the generation of bradykinin and/or the metabolite des-Arg3-BK. Plasma contact with a negatively charged surface activates the contact system of plasma leading to the generation of plasma kallikrein that cleaves high molecular weight kininogen to liberate the nonapeptide bradykinin which is further metabolized. When ACE inhibitor is present the transformation of BK to des-Arg3-BK is inhibited. For reactions that occur in the absence of negatively charged bedside leukoreduction filters and/or ACE inhibitor therapy, unidentified mechanisms not involving BK generation may be responsible.