Objective: To determine the efficacy of a single bolus ephedrine on body temperature reduction attenuation during arthroscopic knee and ankle surgery under spinal anesthesia.

Materials and Methods: The present study was a single-center prospective randomized clinical trial. Patients undergoing arthroscopic ankle or knee surgery were randomized to receive a single intravenous bolus dose of placebo (normal saline) or ephedrine 9 milligrams (mg) just after a subarachnoid injection for spinal anesthesia. Tympanic membrane temperature and blood pressure were recorded at time points. Two-way repeated-measures ANOVAs was performed to analyze the difference of temperature at time points compared with before performing spinal block as primary outcome.

Results: Forty patients were randomized, and 34 patients were included in outcome analysis (control n=18 and ephedrine n=16). Patients in the ephedrine group demonstrated better body temperature preservation. The earliest significant effect could be seen 7.5 minutes after the spinal block (control group – 0.32 ± 0.39℃ and ephedrine group – 0.24 ± 0.5℃, p = 0.007). The ephedrine effect on blood pressure was subtle.

Conclusion: For patients undergoing knee or ankle arthroscopic surgery, a single bolus 9 mg of ephedrine given intravenously just after the subarachnoid injection for spinal anesthesia can preserve core temperature.