Cerebrovascular effects of isoflurane in man. Intracranial pressure and middle cerebral artery flow velocity.

Twelve hydrocephalic patients undergoing hydrodynamic studies and shunt procedures during general anaesthesia were subjected to short term observations of the cerebrovascular effects of isoflurane. Intraventricular pressure (IVP), arterial pressure (AP); cerebral perfusion pressure (CPP = AP-IVP), end-tidal PCO2, Cerebral Function Monitor (CFM) activity and middle cerebral artery (MCA) flow velocity were measured. Introduction of 1% isoflurane for a 10-min period did not cause significant changes in IVP or MCA flow velocity, but caused marked and significant reductions in arterial pressure and CPP, and increases in CFM activity. In five patients 2% isoflurane was administered for another 5 min before discontinuation of the isoflurane. This caused further significant reduction in arterial pressure and increased IVP in four of the five patients. The decrease in CPP was thus even greater than the reduction in arterial pressure and the CFM activity decreased in four out of five patients. The MCA flow velocity did not change significantly.