[An increase in intracranial pressure following fentanyl]

We report an unusual fentanyl-induced reaction in an 8-year-old boy who had to be sedated and hyperventilated because of a severe head injury. Following the intravenous administration of a bolus of fentanyl, the intracranial pressure rose markedly for about 10 min. Simultaneously, the arterial blood pressure fell and heart rate increased, critically reducing the cerebral perfusion pressure temporarily. This reaction could be due to histamine-induced vasodilation.