Effect of intravenous clonidine on prevention of postepidural shivering.

The effects of intravenous clonidine, a central adrenergic alpha-2 agonist, on the incidence of shivering and hemodynamic changes after epidural anesthesia were assessed in patients undergoing extracorporeal shock wave lithotripsy (ESWL). Forty ASA class I or II patients were randomly assigned in a double-blind manner to one of two groups. Twenty patients received intravenous clonidine 150 micrograms/10 ml (clonidine group) and twenty patients received normal saline (control group) at 20 min before epidural administration of 1.5% lidocaine. Shivering was determined objectively by observing involuntary muscle activity. Arterial blood pressure, heart rate, respiratory rate and oxygen saturation were measured at 5-min intervals during the first 50 minutes following IV pretreatment. There was significant difference between clonidine and control groups in the incidence of shivering (5% vs. 55%, p = 0.002). Shivering began at an average of 16.8 +/- 9 min (range: 5-30 min) in control group and only one patient shivered at 18 min in clonidine group. The mean sensory level was T7 in both groups. There were no differences between the two groups in mean arterial pressure and respiratory rate, though there was a trend in reduction of MAP in clonidine group. Heart rate and oxygen saturation decreased slightly in clonidine group. The main adverse effect of clonidine pretreatment was drowsiness. In conclusion, intravenous clonidine 150 micrograms was effective in preventing shivering with minor hemodynamic changes in patients receiving epidural anesthesia.