Postoperative Shivering Among Cannabis Users at a Public Hospital in Trinidad, West Indies

Abstract

Postoperative shivering has been anecdotally observed to be frequent and severe in Cannabis smokers following general anesthesia in the Caribbean. The aim of this study was to compare the frequency and intensity of postoperative shivering in Cannabis users versus non-users. A prospective, cross-sectional, observational design was used. Demographic data were obtained. Patients were grouped into Cannabis users and non-users. All patients received standardized general anesthesia and were administered warmed fluids intraoperatively. Ambient room temperatures and clinical data were recorded. Patients' core body temperature was recorded at 10-minute intervals both in the operating room and the post-anesthesia care unit (PACU). Postoperatively an independent observer assessed the patients who had shivering using a scoring system ranging from 0 to 3. Treatment for shivering and post-treatment shivering scores were also recorded. Fifty-five patients were studied, of which 71% were male. There were 25 (45%) Cannabis users, of which 50% smoked < 5 joints per week, and 35% smoked >10 joints per week; 30 (55%) patients were non-users. The overall incidence of postoperative shivering was 36%; 16% had a shivering score of '3', 13% had '2' and 7% had a score of '1'. The incidence of postoperative shivering among Cannabis users was 40% while it was 33.3% in non-users. Also, 90% of Cannabis users had shivering scores of 2 and 3, compared to 70% of non-users. There was a higher incidence and intensity of shivering in Cannabis smokers, although the study could not establish a statistically significant difference in the frequency and severity of shivering between Cannabis users and non-users.