Up-and-Down Determination of Different Crystalloid Coload Volumes on the ED 90 of Prophylactic Norepinephrine Infusion for Preventing Postspinal Anesthesia Hypotension During Cesarean Section

Yi Chen,1,* Xiangsheng Xiong,2,* Rui Qin,1 Lei Guo,1 Yongqiang Shi,1 Xinli Ni1 1Department of Anesthesiology and Perioperative Medicine, General Hospital of Ningxia Medical University, Yinchuan, People’s Republic of China; 2Department of Anesthesiology, the Fifth People’s Hospital of Huaian, Huaian, People’s Republic of China*These authors contributed equally to this workCorrespondence: Xinli Ni, Department of Anesthesiology and Perioperative Medicine, General Hospital of Ningxia Medical University, Yinchuan, People’s Republic of China, Email xinlini6@nyfy.com.cnBackground: Fluid loading improves hemodynamic stability and reduces the incidence rate of post-spinal anesthesia hypotension when prophylactic vasopressors are administered. We investigated the impact of different crystalloid coload volumes on the 90% effective dose (ED) of prophylactic norepinephrine infusion for preventing post-spinal anesthesia hypotension in non-hypertensive patients undergoing cesarean section.Methods: Patients were randomly allocated to receive one of the different crystalloid coload volumes (0mL/kg [0mL/kg Group], 5mL kg [5mL/kg Group], and 10mL kg [10mL/kg Group]) in combination with prophylactic norepinephrine infusion immediately after the induction of spinal anesthesia. The prophylactic norepinephrine infusion doses were determined using the up-and-down sequential allocation methodology, with an initial dose of 0.025 μg/kg/min and a gradient of 0.005 μg/kg/min. The primary endpoint was the effective dose at which 90% (ED 90) of patients responded to prophylactic norepinephrine infusion for preventing post-spinal anesthesia hypotension.Results: The estimated effective dose of norepinephrine infusion, at which 90% (ED 90) of patients responded, was found to be 0.084 (95% CI, 0.070 to 0.86), 0.074 (95% CI, 0.059 to 0.077), and 0.063 (95% CI, 0.053 to 0.064) μg/kg/min in the three groups, respectively.Conclusion: A crystalloid coload of 5 mL/kg or 10 mL/kg, as opposed to the groups receiving 0 mL/kg crystalloid coloads, resulted in a reduction of approximately 11.9% and 25.0%, respectively, in the ED90 of prophylactic norepinephrine infusion for preventing post-spinal anesthesia hypotension during cesarean section.Keywords: crystalloid, coload, norepinephrine, postspinal anesthesia hypotension, cesarean section