///2010 Abstract Details
2010 Abstract Details2018-05-01T17:52:49+00:00

Comparison of cardiac output changes associated with the use of prophylactic phenylephrine infusion versus bolus administration

Abstract Number: 55
Abstract Type: Original Research

Ashraf S Habib MBBCh, MSC, FRCA1 ; William D White MPH2; Kristin E Weaver BS3; Terrence K Allen MB, FRCA4

Introduction: Maternal hemodynamic changes associated with the use of a prophylactic phenylephrine (PE) infusion during spinal anesthesia for cesarean section have not been well described. This study compares the hemodynamic changes between patients receiving a prophylactic PE infusion, with those receiving PE boluses for the treatment of established hypotension.

Methods: Women undergoing cesarean section under spinal anesthesia were enrolled. Cardiac output (CO) was measured noninvasively using a transthoracic bioimpedance monitor, the Physio Flow. Baseline CO, stroke volume (SV), heart rate (HR) and systolic blood pressure (SBP) were measured in the preoperative holding area with the patients lying supine with left uterine displacement (LUD). Following a standardized spinal anesthesia in the sitting position, patients were laid supine with LUD. In the infusion group, a variable rate prophylactic PE infusion was started at 50 mcg/min and adjusted according to SBP measurements and HR according to a predefined algorithm. In the boluses groups, a 100-200 mcg PE bolus was given if SBP was < 20 % of baseline. Patients in both groups received a 2L crystalloid coload. After delivery, oxytocin 5 U bolus dose was administered followed by an infusion of 25 U/h. Hemodynamic parameters were monitored throughout surgery. Within and between group comparisons were performed. We also compared median performance error, and median absolute performance error (MADPE) between the two groups during the spinal to incision period relative to baseline values.

Results: 31 women completed this ongoing study. In both groups, there was a decrease in CO and HR following spinal anesthesia, however this decrease was only statistically significant in the infusion group. There was a significant increase in CO and HR following delivery in both groups. During the predelivery period CO was significantly lower in the infusion group compared to the bolus group. HR was significantly lower in the infusion group during the spinal until incision and predelivery periods. The CO and SV MDAPE during the period from spinal to incision was 10.9 % and 9.1 % in the bolus group, and 24.8 % and 14.3 % in the infusion group respectively (p<0.0001, and p=0.0456 respectively).

Conclusions: In patients receiving a prophylactic PE infusion, CO and HR are significantly lower than in patients receiving boluses. The magnitude of the CO and SV change is also significantly greater with the use of an infusion.

SOAP 2010