Allergic and hypotensive reactions

Allergic reactions

Definition

Allergic reactions are those occurring up to 24 hours following a transfusion of blood components, for which no other obvious cause is evident.

These are reactions to plasma proteins in the donor unit (often against a specific donor); difficult to avoid and usually unpredictable.

They range from mild to severe (including anaphylaxis), with symptoms including flushing, urticaria or rash, wheeze, bronchospasm, stridor, angiodema and circulatory problems (not typically associated with fever type symptoms).

Frequency

Mild: Common (≥1 in 100 to <1 in 10).

Moderate and severe: Rare (≥1 in 10,000 to <1 in 1,000).

Reducing the risk

A small number of people may have recurrent allergic reaction to transfusion.

Measures to mitigate this include use of:

  • Platelets in additive solution
  • Prophylactic antihistamine
  • 'Washed' red cells
  • Solvent-detergent treated plasma

Treatment as per local protocol: it is recommended giving appropriate targeted treatment and where required, preventative cover for future transfusion episodes; measures can include the use of pre-transfusion antihistamine, steroids are not recommended for the prevention of allergic reactions.

Hypotensive reactions

Hypotensive reactions are defined as a decrease in blood pressure during or within 1 hour after cessation of a transfusion, most often present as a sudden, profound drop in blood pressure within 15 minutes of starting the transfusion and respond rapidly to stopping the transfusion.

These reactions are thought to be mediated by bradykinin response.

They range from moderate (a drop in systolic blood pressure of ≥30 mmHg and a systolic blood pressure of ≤80 mmHg) to severe (shock).

Further information and resources

Serious Hazards of Transfusion (SHOT) resources:

British Society for Haematology (BSH) guidelines:

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