I.v. clonidine prevents post-extradural shivering

We have studied the efficacy of i.v. clonidine to prevent shivering in 100 healthy patients who received extradural block for knee arthroscopy. Patients were randomly allocated to two groups. Just before extradural anaesthesia (0 min = baseline), group I (n = 50) received i.v. clonidine 1 mu g kg(-1), group II (n = 50) received a saline bolus. Systolic arterial pressure (SAP), heart rate (HR), oxygen saturation (Sp(O2)), cutaneous temperature and level of sedation, were all recorded at baseline and after 10, 20, 30, 45, 60 min. Shivering was evaluated by a blinded investigator for a period of 90 min and was graded as moderate or severe. Three patients in group I shivered compared with 19 in group II (P < 0.001). Patients with severe shivering were seen only in group II. There were no significant differences between the groups during the study period in SAP, HR, Sp(O2), cutaneous temperature or level of sedation. We conclude that preventive use of i.v. clonidine 1 mu g kg(-1) provides a significant reduction in the incidence of post-extradural shivering without clinically relevant adverse side effects.