• Yan-Ping Zhao, Xu-Feng Zhang, Jing Qian, Fei Xiao, and Xin-Zhong Chen.
• From the Department of Anesthesia, Women's Hospital, Zhejiang University School of Medicine, Hangzhou, China.
• Anesth. Analg. 2024 Jun 13.

BackgroundIncreasing the temperature of intrathecal local anesthetics has been shown to increase the speed of onset and block height of spinal anesthesia. However, how this influences dose requirement has not been fully quantified. The aim of this study was to determine and compare the effective dose for anesthesia for cesarean delivery in 50% of patients (ED50) of intrathecal bupivacaine given at temperatures of 37 °C (body temperature) or 24 °C (room temperature).MethodsEighty healthy parturients having elective cesarean delivery under combined spinal-epidural anesthesia were randomly assigned to receive intrathecal hyperbaric bupivacaine stored at 37 °C (body temperature group) or 24 °C (room temperature group). The first subject in each group received a bupivacaine dose of 10 mg. The dose for each subsequent subject in each group was varied with an increment or decrement of 1 mg based on the response (effective or noneffective) of the previous subject. Patients for whom the dose was noneffective received epidural supplementation after data collection with lidocaine 2% as required until anesthesia was sufficient for surgery. Values for ED50 were calculated using modified up-down sequential analysis with probit analysis applied as a backup sensitivity analysis. These values were compared and the relative mean potency was calculated.ResultsThe ED50 (mean [95% confidence interval, CI]) of intrathecal hyperbaric bupivacaine was lower in the body temperature group (6.7 [5.7-7.6] mg) compared with the room temperature group (8.1 [7.7-8.6] mg) (P < .05). The relative potency ratio for intrathecal bupivacaine for the room temperature group versus the body temperature group was 0.84 (95% CI, 0.77-0.93).ConclusionsWarming hyperbaric bupivacaine to body temperature reduced the dose requirement for spinal anesthesia for cesarean delivery by approximately 16% (95% CI, 7%-23%).Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the International Anesthesia Research Society.

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