Fixed dilated pupils in association with a thiopentone infusion in severe head injury

We report a case of thiopentone induced mydriasis in a 17-year-old, head injured patient. Two initial 50 mg intravenous boluses and 12 h of a 125 mg/h infusion (total of 1500 mg) of thiopentone were used to reduce intracranial pressure in this patient. The patient developed fixed dilated pupils (> 8 mm) and hypothermia (27 degrees C). Thiopentone plasma concentrations were performed giving a level of 309 mumol/1; withdrawing the thiopentone infusion resulted in the pupil diameter returning to 5 mm within 24 h. A new drug plasma concentration was performed revealing a level of 198 mumol/1. We discuss the clinical implications of such a drug response and review the relevant literature.