Clonidine at induction reduces shivering after general anaesthesia

Postanaesthetic shivering occurs in 5-65% of patients. In addition to causing discomfort, it is associated with deleterious consequences. Our objective was to investigate the effect of 150 micrograms clonidine, at induction of anaesthesia, on perioperative core and peripheral temperature, incidence of postanaesthetic shivering and patients' perception of cold.

Sixty ASA 1 or 2 patients scheduled for elective orthopaedic limb surgery were randomly allocated to group 1, who received 150 micrograms clonidine iv, or group 2, who received a saline bolus iv, before induction. In all patients, anaesthesia was induced with fentanyl and propofol and maintained by spontaneous respiration (via a laryngeal mask airway) of oxygen, nitrous oxide and enflurane. Core (nasopharyngeal) and peripheral (dorsal hand) temperatures were recorded at induction and 15-min intervals. Nurses, unaware of the treatment groups, recorded visible shivering in the recovery room. When cognitive function returned, patients were asked to grade their perception of cold on a 10 cm linear analogue scale, higher scores indicating heat discomfort.

While core temperature decreased and peripheral temperature increased in both groups, there was no difference between the groups at any time. However, there was a lower incidence of shivering in the clonidine group (20% vs 66.7%, P < 0.001). Patients receiving clonidine felt warmer; thermal comfort score (median interquartile range) 5.9 (5.0-7.2) vs 5.0 (4.5-6.0), P < 0.05).

Clonidine 150 g iv at induction of anaesthesia reduces the incidence of shivering and patients' subjective perception of cold on emergence from general anaesthesia.