Phenylephrine Dose and Mode of Administration for Spinal Anesthesia Induced Hypotension

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.