Intraoperative allergic reactions to hydroxyethyl starch: a report of two cases.

The presentation, evolution, and treatment of two cases of intraoperative allergic reactions are described. In each case, the offending agent was felt to be hydroxyethyl starch (HES), a synthetic polymer colloid solution used for intravascular volume expansion. Symptoms included urticaria, angioedema, and hypotension in the first patient, and urticaria, hypoxia, and haemoconcentration in the second patient. Both patients had earlier received multiple drugs and/or blood products. However, HES administration in both patients immediately produced allergic symptomatology. The first patient had concurrent depression of serum total complement levels (CH50) and no elevation of plasma histamine levels, which suggested a complement-mediated reaction to HES. Levels of CH50 and histamine were not obtained from the second patient. Direct stimulation of mast cell degranulation by the offending agent, complement activation, or conventional antigen-antibody interaction in a previously exposed patient may initiate intraoperative allergic reactions. Anaesthesia personnel should be aware of the risk of intraoperative allergic reactions to HES and be prepared to treat them rapidly and effectively.