Effects of fentanyl on intracranial pressure and cerebral perfusion pressure during hypocapnia.

Ten patients presenting for carniotomy were studied. Each was anaesthetized with thiopentone or Althesin followed by tubocurarine and the lungs were hyperventilated with nitrous oxide in oxygen. Fentanyl 0.2 mg was administered i.v. and the intracranial pressure (i.c.p.) and mean arterial pressure were recorded continuously for 10 min. At the time of administration of fentanyl nine of the 10 patients were hypocapnic (PaCO2 less than 4 kPa). The changes in i.c.p. were small. Cerebral perfusion pressures less than 50 mm Hg were observed in two patients who had moderate hypotension before the drug was given. We conclude that fentanyl is a valuable agent in the hyperventilation technique in patients with intracranial space-occupying lesions, provided that hypotension is absent.