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Continuous Hemodynamic Monitoring during Cesarean Delivery: Phenylephrine Infusion versus Lower Extremity Compression. A Randomized, Double-blinded, Placebo-controlled Study
Abstract Number: O2-02
Abstract Type: Original Research
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 few small studies showing moderate success. The primary aim of this trial was to compare the prophylactic effect of low-dose phenylephrine infusion and lower limb wrapping on maternal hemodynamic condition. Secondly, we intended to examine the hemodynamic effects of including a start-bolus into low-dose phenylephrine infusion. Thirdly, this is the first study using continuous invasive monitoring to investigate the hemodynamic effects of lower limb wrapping, and to compare prophylactic interventions based on different physiologic strategies.
Methods: In this randomized double-blinded placebo-controlled study, 120 healthy women either received phenylephrine (starting bolus of 0.25 μg⋅kg-1and infusion of 0.25 μg⋅kg-1⋅min-1), leg wrapping, or placebo during spinal anesthesia for elective cesarean delivery. LiDCOplus was used for continuous minimally invasive hemodynamic monitoring.
Results: In the phenylephrine group, systolic blood pressure and systemic vascular resistance were statistically significantly higher, duration of hypotension shorter, stroke volume was similar, and heart rate and cardiac output were statistically significantly lower compared to the leg-wrapping group. Compared to placebo, the leg-wrapping group had statistically significantly higher blood pressure, stroke volume, and cardiac output.
Conclusions: Low-dose phenylephrine infusion is superior to lower limb compression and placebo for hemodynamic stability during spinal anesthesia for cesarean delivery. Phenylephrine stabilizes blood pressure more efficiently and more physiologically, by counteracting arterial vasodilation, the main hemodynamic effect of spinal anesthesia. Our findings suggest that phenylephrine also improves preload, by increasing venous return, likely via splanchnic recruitment.
Lower limb wrapping reduces hypotension compared to placebo by impeding venous pooling to the lower extremities, thus increasing venous return. Concerning the recent debate on the role of venous and arterial circulation in obstetric spinal hypotension, this finding supports that there actually is some early venodilatation after induction of spinal anesthesia which contributes to hypotension.