Transfusion-associated hypotension

When to suspect this reaction

Transfusion-associated hypotension is defined in adults as an isolated fall in systolic blood pressure of 30 mmHg or more occurring during or within one hour of completing transfusion and systolic blood pressure of 80 mmHg mm or less in the absence of allergic or anaphylactic symptoms.

This is a diagnosis of exclusion with no other transfusion related adverse symptoms and signs, like no fever, no urticaria/hives, no respiratory distress or haemolysis.

A patient with hypotension may complain of dizziness, headache, feeling unwell or visual changes. Sitting or standing from the bed or chair may result in syncope. This may occur during or after a transfusion.

Hypotension may be detected when performing routine observations and before any other symptoms are seen.

Always consider other potential causes of hypotension including:

Patient’s underlying condition (unrelated to transfusion, i.e. medications, sepsis, bleeding).
Anaphylaxis (may present as isolated hypotension)
Transfusion related acute lung injury (TRALI)
Transfusion-transmitted bacterial infection
Acute haemolytic reactions/ ABO incompatibility

Usual causes

Isolated hypotension is rare. The most likely cause is an excess of bradykinin, a vasoactive peptide, particularly where bradykinin metabolism is inhibited, for example, in patients taking ACE inhibitors. Factors that increase bradykinin concentrations include leucocyte reduction of blood components using negatively charged filters and ACE activity in donors and recipients.

Bradykinin causes blood vessels to relax or vasodilate, directly leading to hypotension. In most patients this process is trivial and has no clinical consequences.

Normally ACE rapidly inactivates bradykinin. Patients taking an ACE inhibitor may therefore have a higher risk of transfusion-associated hypotension, although the correlation is unclear.

Investigation

There are no specific investigations for this reaction.

Other reactions that feature hypotension must be excluded.

What to do

Stop the transfusion immediately and do not restart this unit.

Give IV fluids as required.

Follow other steps for managing suspected transfusion reactions.