Comparison of prophylactic use of midazolam, ketamine, and ketamine plus midazolam for prevention of shivering during regional anaesthesia: a randomized double-blind placebo controlled trial.

BACKGROUND Regional anaesthesia, like general anaesthesia, influences the thermoregulatory process. The aim of the present study was to compare the efficacy of low-dose prophylactic midazolam with that of placebo, ketamine, and a combination of ketamine and midazolam in the prevention of shivering caused by regional anaesthesia. METHODS In this double-blind study, 120 ASA I and II patients undergoing orthopaedic surgery were included. Subarachnoid anaesthesia was performed in all patients with bupivacaine 15 mg. The patients were randomly allocated to receive saline (Group C), ketamine 0.5 mg (Group K), midazolam 75 microg kg(-1) (Group M), or ketamine 0.25 mg+midazolam 37.5 microg kg(-1) (Group KM). During surgery, a shivering score was recorded at 5 min intervals. Tympanic and axillary temperature were recorded at 10 min intervals during the perioperative period. RESULTS After 15 min, the incidences of shivering in Groups C, M, K, and KM were 60%, 50%, 23.3%, 3.3%, respectively (P=0.000). The differences between Group KM and Groups M, K, and C were statistically significant (P=0.000, P=0.026, P<0.001, respectively). The number of patients with a shivering score of > or =3 was significantly higher in Group C compared with Groups M, K, and KM (8 vs 4, 1, and 0, respectively, P=0.040). CONCLUSIONS Prophylactic use of ketamine 0.25 mg kg(-1)+midazolam 37.5 microg kg(-1) i.v. was more effective than ketamine 0.5 mg kg(-1) i.v. or midazolam 75 microg kg(-1) i.v. in preventing shivering developed during regional anaesthesia.