The effect of clonidine on intracranial pressure (ICP), mean arterial pressure (MAP), cerebral perfusion pressure (CPP), heart rate (HR), and drug requirements was studied in 24 patients scheduled for elective cerebral tumor resection (ICP < or = 20 mm Hg). The patients were randomly assigned to one of two groups: Group P (placebo), 12 patients; Group C (clonidine 3 micrograms/kg 10 min before induction), 12 patients. In all patients, anesthesia was induced with a propofol infusion (500 micrograms/kg/min) combined with fentanyl 2 micrograms/kg, lidocaine 1.5 mg/kg, and vecuronium 0.1 mg/kg. Propofol was also used for maintenance. During the preinduction period, clonidine had no effect on ICP or HR, but in clonidine-treated patients, MAP and CPP decreased significantly in comparison to those of the placebo group. During induction, ICP and HR were stable and similar in both groups. MAP and CPP remained significantly lower in Group C. At intubation and Mayfield clamp application, ICP increased in both groups, with similar values at all times. MAP increased in both groups at intubation, Mayfield clamp application, and incision, staying lower, however, in Group C. CPP followed a pattern similar to that of MAP. Propofol requirements up to the 20th min were lower in Group C than in Group P (2.08 +/- 0.83 vs. 3.3 +/- 0.7 mg/kg, p < 0.05). Finally, throughout the study, eight patients in Group C versus two in Group P had a CPP value < 60 mm Hg for > or = 1 min (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)