ED50 Determination of Hydroxyethylstarch for Treatment of Hypotension During Cesarean Section Under Spinal Anesthesia

ED50 Determination of Hydroxyethylstarch for Treatment of Hypotension During Cesarean Section Under Spinal Anesthesia

ED50 Determination of Hydroxyethylstarch for Treatment of Hypotension During Cesarean Section Under Spinal Anesthesia

The purpose of this trial is to determine the effective volume of hydroxyethylstarch 130/0.4 which would prevent the occurence of maternal hypotension in 50% of healthy pregnant women undergoing a cesarean section under spinal anesthesia.

The incidence of spinal anesthesia-induced hypotension in pregnant women undergoing a cesarean section is high. A preoperative fluid bolus of undetermined volume is frequently administered to lower the incidence of maternal hypotension, with a somewhat poor efficacy. Recently, several investigations have shown that the use of a phenylephrine infusion after the induction of spinal anesthesia results in a significant reduction in hypotensive episodes. Given the high efficacy of this therapy (incidence of hypotension around 20%), it is possible to determine the effective volume of fluid which would prevent hypotension in 50% of the patients studied (ED50). Healthy term pregnant women undergoing elective cesarean section under spinal anesthesia will be recruited in this trial. The spinal anesthesia regimen will be standardized and all subjects will receive a phenylephrine infusion. The fluid investigated is hydroxyethylstarch (HES) 130/0.4 (Volulyte(R)). The ED50 will be determined using an up-down sequential allocation method initially described by Dixon & Massey. The determination of the HES ED50 will help the anesthesiologist in further treating maternal hypotension appropriately.

Obstetric anesthesia, Spinal anesthesia, Hypotension, Fluid therapy, Cesarean section, phenylephrine, cardiac output

first patient : 500 mL. Following volumes according to up-down sequential allocation, with increments or decrements of 100 mL. An absence of hypotension will lead to an decrement while a presence of hypotension will result in an increment.

Inclusion Criteria: Healthy pregnant women (ASA I or II) Normal pregnancy Term gestation (37 weeks and above) Elective cesarean section Spinal anesthesia Exclusion Criteria: Cardiopathies Hypertensive disease/ pre-eclampsia / eclampsia Any contraindication to neuraxial anesthesia Patient refusal Body mass index > 30 at first antenatal visit and > 32 at cesarean section Twin pregnancy Known allergies to HES Emergency cesarean section