Different Crystalloid Coload Volumes on the 90% ED of Norepinephrine

Up-and-Down Determination of Different Crystalloid Coload Volumes on the 90% Effective Dose of Prophylactic Norepinephrine Infusions for Preventing Postspinal Anesthesia Hypotension During Cesarean Section

The purpose of this study is to investigate the effect of different crystalloid coload volumes on the 90% effective dose of prophylactic norepinephrine infusions for preventing postspinal anesthesia hypotension during cesarean section.

Post-spinal anesthesia hypotension is a frequent complication during spinal anesthesia for cesarean section. The incidence of post-spinal anesthesia hypotension is as high as 62.1-89.7% if prophylactic measures are not taken. Coload has been highly demonstrated for prevention and/or treatment of post-spinal anesthesia hypotension. In addition, there's some evidence that prophylactic infusion of norepinephrine could effectively reduce the incidence of post-spinal anesthesia hypotension in parturients undergoing cesarean section. The purpose of this study is to investigate the effect of different crystalloid coload volumes on the 90% effective dose of norepinephrine infusion prophylaxis for hypotension during spinal anesthesia for cesarean section.

No fluid coload was given. An initial infusion dose of prophylactic norepinephrine simultaneous with spinal anesthesia

5 ml/kg crystalloid coload combined with an initial infusion dose of prophylactic norepinephrine simultaneous with spinal anesthesia.

10 ml/kg crystalloid coload combined with an initial infusion dose of prophylactic norepinephrine simultaneous with spinal anesthesia.

No fluid coload was given. An initial infusion dose of prophylactic norepinephrine (0.025 ug/kg/min) simultaneous with spinal anesthesia. The dose administered to subsequent patients varied by increments or decrements of 0.005 ug/kg/min of prophylactic norepinephrine according to the responses of previous patients according to the up-down sequential allocation.

5 ml/kg crystalloid coload combined with an initial infusion dose of prophylactic norepinephrine (0.025 ug/kg/min) simultaneous with spinal anesthesia. The dose administered to subsequent patients varied by increments or decrements of 0.005 ug/kg/min of prophylactic norepinephrine according to the responses of previous patients according to the up-down sequential allocation.

10 ml/kg crystalloid coload combined with an initial infusion dose of prophylactic norepinephrine (0.025 ug/kg/min) simultaneous with spinal anesthesia. The dose administered to subsequent patients varied by increments or decrements of 0.005 ug/kg/min of prophylactic norepinephrine according to the responses of previous patients according to the up-down sequential allocation.

The dose of prophylactic norepinephrine that would be effective in preventing postspinal anesthesia hypotension in 50% (effective dose, ED 50) and 90% (ED90) of patients

Inclusion Criteria: 18-45 years Primipara or multipara Singleton pregnancy ≥37 weeks American Society of Anesthesiologists physical status classification I to II Scheduled for cesarean section under spinal anesthesia Exclusion Criteria: Body height < 150 cm Body weight > 100 kg or body mass index (BMI) ≥ 40 kg/m2 Eclampsia or chronic hypertension or baseline blood pressure ≥180 mmHg Hemoglobin < 7g/dl Fetal distress, or known fetal developmental anomaly