Comparison of Different HES Coload Volumes on the 90% ED of Norepinephrine

Comparison of Different 6% Hydroxyethyl Starch (130/0.4) Coload Volumes on the 90% Effective Dose of Norepinephrine Infusion Prophylaxis for Hypotension During Spinal Anesthesia for Cesarean Section

The purpose of this study is to investigate the effect of different 6% hydroxyethyl starch (130/0.4) coload volumes on the 90% effective dose of norepinephrine infusion prophylaxis for hypotension during spinal anesthesia for 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 6% hydroxyethyl starch (130/0.4) coload volumes on the 90% effective dose of norepinephrine infusion prophylaxis for hypotension during spinal anesthesia for cesarean section.

Norepinephrine, Hydroxyethyl starch 130/0.4, Postspinal anesthesia hypotension, Coload, Cesarean section

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

5 ml/kg 6% Hydroxyethyl starch (130/0.4) coload combined with an initial infusion dose of prophylactic norepinephrine simultaneous with spinal anesthesia.

10 ml/kg 6% Hydroxyethyl starch (130/0.4) 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 6% Hydroxyethyl starch (130/0.4) 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 6% Hydroxyethyl starch (130/0.4) 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) of patients

The dose of prophylactic norepinephrine that would be effective in preventing postspinal anesthesia hypotension in 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