Hemodynamics of Phenylephrine Infusion Versus Lower Extremity Compression During Spinal Anesthesia for Cesarean Delivery: A Randomized, Double-Blind, Placebo-Controlled Study

BACKGROUND: Phenylephrine infusion is the current first-line choice for prevention of spinal hypotension during cesarean delivery. The optimal dosage regimen is still undetermined. A mechanical alternative, lower limb wrapping, has been examined in a few small studies showing moderate success. In this trial, we compared the effect of leg wrapping with low-dose phenylephrine infusion and with placebo treatment on systolic arterial blood pressure during spinal anesthesia for cesarean delivery. METHODS: In this randomized, double-blinded, placebo-controlled study, healthy women received either phenylephrine (n = 38; initial bolus of 0.25 g kg(-1) and infusion of 0.25 g kg(-1) min(-1)), leg wrapping (n = 38), or no treatment (control; n = 36) during spinal anesthesia for elective cesarean delivery. LiDCOplus was used for continuous minimally invasive hemodynamic monitoring. The extent of decrease in systolic arterial blood pressure (for 13 minutes after spinal induction) was the primary outcome. Cardiac output, systemic vascular resistance, stroke volume, heart rate, neonatal acid-base status, and Apgar score were secondary outcome variables. Mixed model analysis of continuous hemodynamic trends during the first 13 minutes after induction of spinal anesthesia was performed. RESULTS: In the phenylephrine group, the decrease in systolic arterial blood pressure was significantly less (difference in rate of change, 0.09 mm Hg 5 s(-1); 95% confidence interval, 0.02-0.16; P = 0.013); systemic vascular resistance (P < 0.001) was significantly higher; stroke volume (P = 0.41) was similar; and heart rate (P = 0.002) and cardiac output (P < 0.001) were significantly lower compared with the leg wrapping group. Compared with control, the leg wrapping group had a significantly smaller decrease in systolic arterial blood pressure (0.39 mm Hg 5 s(-1); 95% confidence interval, 0.32-0.46; P < 0.001), higher stroke volume (P < 0.001), and higher cardiac output (P = 0.001). CONCLUSIONS: An initial bolus of phenylephrine followed by a low-dose phenylephrine infusion was superior to leg wrapping and no intervention for the prevention of hypotension during spinal anesthesia for cesarean delivery. Phenylephrine prevented hypotension primarily by restoring systemic vascular resistance and did not cause hypertension or a clinically relevant reduction in cardiac output. Leg wrapping prevented hypotension compared with no intervention by limiting modest early spinal anesthesia-mediated venodilation.