Journal of the Medical Association of Thailand Vol 103, No 2:FEBRUARY 2020 0125-2208 103 2 2020 Feb Single Bolus Intravenous Ephedrine Attenuates Reduction of Core Body Temperature in Patients Undergoing Spinal Anesthesia for Arthroscopic Knee and Ankle Surgery 134-41 EN Thanist Pravitharangul Cherdkiat Karnjanarachata Pornpatra Areeruk Sasithaporn Thananuwong Rojnarin Komonhirun Original Article To determine the efficacy of a single bolus ephedrine on body temperature reduction attenuation during arthroscopic knee and ankle surgery under spinal anesthesia. 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. 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. 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.Trial registration: ClinicalTrials.gov, NCT02948920 Ephedrine Heat Hypothermia Spinal anesthesia TemperatureReceived 11 Mar 2019 | Revised 17 Apr 2019 | Accepted 22 Apr 2019