A Height-Based Dosing Algorithm of Bupivacaine in Spinal Anesthesia for Decreasing Maternal Hypotension in Cesarean Section Without Prophylactic Fluid Preloading and Vasopressors: A Randomized-Controlled Non-Inferiority Trial

Background: There is a high incidence of maternal hypotension in spinal anesthesia for cesarean section. The aim of the study is to investigate whether there is a height-based dosing algorithm of bupivacaine that provides adequate anesthesia with less maternal hypotension. Methods: There were 2 groups of 280 parturients who did not receive prophylactic fluid preloading: Test and Conventional group. In Test group, a height based dosing algorithm was used to confirm the dose of bupivacaine in parturients without prophylactic vasopressors. In the Conventional group, a constant dose of bupivacaine was used. The complications and quality of anesthesia were evaluated. Results: In the Conventional group, the shorter participants had higher incidence of hypotension, faster sensory block time, and more participants with complete motor block (p = 0.030, 2.957 x 10(-14), and 0.012). In the Test group, the incidence of hypotension, sensory block time, and number of participants with complete motor block did not change with height (p = 0.199, 0.617, and 0.209). The height-based dosing algorithm of bupivacaine decreased the incidence of hypotension (p = 0.004), induced lower sensory block level and less degree of motor block (p = 3.513 x 10(-7) and 5.711 x 10(-11)). The quality of analgesia, quality of muscle relaxation, and degree of intraoperative comfort were similar in both groups (p = 0.065, 0.498, and 0.483). Conclusions: The height influences the dose of bupivacaine in spinal anesthesia; without prophylactic fluid pre-loading and vasopressors, the height-based dosing algorithm of bupivacaine is suitable, and meets the cesarean section' requirement with less maternal hypotension.