ED50/ED90 of Phenylephrine Infusion for Preventing Spinal Anesthesia-Induced Hypotension: Supine vs Left-Tilt 15°

Condition(s) studied

Investigational drug(s) / intervention(s)

Phenylephrine hydrochloride infusion: Prophylactic fixed-rate IV infusion (pump rate 0.6 mL/kg/h, concentration-blinded), from completion of spinal anesthesia until delivery

Study summary

The purpose of this study is to determine the 50% and 90% effective doses (ED50 and ED90) of prophylactic phenylephrine infusion for preventing spinal anesthesia-induced hypotension during elective cesarean delivery, in the supine position and in the left-lateral-tilt 15° position, respectively. Two hundred parturients with singleton term pregnancies will be randomized 1:1 to the supine group or the left-tilt 15° group, and within each position 1:1:1:1 to one of four fixed phenylephrine infusion rates (0.2, 0.4, 0.6, or 0.8 μg/kg/min; 25 per group), with the rate allocation masked by concentration blinding (identical pump rate, different solution concentrations). Spinal anesthesia consists of hyperbaric bupivacaine 12 mg plus morphine 0.15 mg. The primary outcome is the incidence of hypotension (systolic blood pressure \< 80% of baseline or \< 90 mmHg) from completion of the intrathecal injection to delivery. ED50 and ED90 will be estimated by probit regression within each position.

Eligibility

Primary outcome measure(s)

• hypotension incidence of hypotension from completion of intrathecal injection to delivery of the infant — From completion of spinal anesthesia to fetal delivery
  Hypotension defined as systolic blood pressure \< 80% of baseline (measured in the assigned study position) or \< 90 mmHg

Trial sites (1)

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