Intraoperative clonidine administration to neurosurgical patients.

The goals of this two-part study were to determine the dose of clonidine to prevent postoperative shivering after mild hypothermia and to evaluate the effect of clonidine on recovery from anesthesia in patients undergoing surgery for intracranial lesions. We enrolled 48 patients undergoing elective supratentorial neurosurgical procedures into one of two studies. In study 1 (n=14) we determined the ED50 of clonidine to prevent postoperative shivering after mild hypothermia (35 degrees C) using Dixon's up-and-down method. Clonidine dose for the first study patient was 3 microg/kg. The dose was then adjusted in 1-microg/kg increments for the following patients. Shivering was assessed for 1 h postoperatively. Study 2 (n=34) was a prospective, randomized, double-blind, placebo controlled study to evaluate the effect of 3 microg/kg clonidine on recovery from anesthesia. At the beginning of dural closure, patients randomly received a 15-min infusion of either clonidine or normal saline. Recovery variables were studied for 2 h after the end of anesthesia. The ED50 of clonidine to prevent shivering was 1.1 +/- 1.5 microg/kg in neurosurgical patients whose target core temperature was 35 degrees C at the end of surgery. Compared with saline, 3 microg/kg of clonidine administered to neurosurgical patients 1 h before the end of anesthesia did not delay emergence from anesthesia nor did it have clinically significant sedative or hemodynamic effects. Our results imply that clonidine may be used in neurosurgical patients to prevent postoperative shivering after mild hypothermia.