Phenylephrine Dose and Mode of Administration for Spinal Anesthesia Induced Hypotension

Correlation and Effects on Cardiac Output With Intermittent Phenylephrine Administration of 50 mcg Versus 100 mcg or 100mcg/Min Prophylactic Infusion for Treatment of Hypotension in Parturients After Receiving Spinal Anesthesia for Cesarean Delivery

Three different regimens of phenylephrine are being evaluated to see if one is superior over the other in the maintenance of cardiac output while keeping normotension and/or treating hypotension experienced when receiving spinal anesthesia for cesarean delivery.

Phenylephrine will be administered in one of 3 regimens: Intermittent bolus of 50 mcg, Intermittent bolus of 100 mcg, or continuous infusion of 100 mcg/min. The infusion will contain either phenylephrine or normal saline (placebo). Subjects who are randomized to receive a bolus dose will receive placebo in the infusion. Subjects who are randomized to receive the phenylephrine infusion will have normal saline (placebo) in the bolus syringe. Baseline blood pressures will be obtained prior to surgery and then maintained using these drugs. Blood pressure and heart rate will be monitored as usual standard of care. Continuous cardiac output and hemodynamic monitoring will be obtained using CNAP (Tm) or similar (equivalent) monitoring device. Blood pressure will be maintained at 90-120% of baseline utilizing infusion and/or bolus with the 3 regimens.

Magnitude of cardiac output reduction for the duration from preoperative baseline from time of spinal anesthesia to delivery of fetus and placenta.

Inclusion Criteria: scheduled for cesarean delivery age >/=18 years of age >/= 37 weeks EGA ASA status I-III Exclusion Criteria: allergy to medications used in the study non-English speaking