CARDIOVASCULAR AND ENDOCRINE EFFECTS OF CLONIDINE PREMEDICATION IN NEUROSURGICAL PATIENTS

The present study was conducted to examine the haemodynamic and endocrine effects of clonidine, given as sole preanaesthetic medication, in neurosurgical patients. Nineteen patients of ASA physical status I and II, subjected to craniotomy, randomly received po premedication of either clonidine (300-mu-g, n = 9) or placebo (n = 10). Blood pressure and heart rate were monitored continuously, while arterial blood samples were collected at specific times, from induction of anaesthesia to recovery, for the measurement of plasma concentrations of epinephrine, norepinephrine, cortisol, aldosterone, and glucose. Clonidine treatment led to a decrease in mean arterial blood pressure (MABP), heart rate (HR), and plasma cortisol and aldosterone concentrations throughout the study, compared with placebo (P < 0.05). Clonidine, however, did not prevent increases in MABP (16 +/- 5 mmHg, mean +/- SE, P < 0.05) and HR (18 +/- 4 bpm, P < 0.05) during induction of anaesthesia, which was comparable to the placebo group. Plasma catecholamine concentrations did not differ between the two groups. Plasma glucose concentrations increased in both groups at the end of the study (P < 0.05), but were lower in clonidine-treated patients (P < 0.05). Though statistically significant, the observed inhibitory haemodynamic and endocrine effects of clonidine seem to be of minor clinical importance. As the action of clonidine on cerebral blood flow regulation is not well known, we see not advantage in the preanaesthetic administration of clonidine to neurosurgical patients with normal cardiovascular status.