Use of a Prophylactic Phenylephrine Infusion for Elective Cesarean Delivery under Spinal Anesthesia is Protective against Intraoperative Heat Loss.
Abstract Number: T-16
Abstract Type: Original Research
Introduction: Perioperative hypothermia is associated with serious adverse outcomes.  The primary mechanism leading to hypothermia from regional anesthesia is core-to-peripheral redistribution of body heat from arterial and venous vasodilatation which may be reduced by phenylephrine infusions.  This study compares PACU admission temperatures in women receiving prophylactic phenylephrine infusions (PI) vs. intermittent phenylephrine boluses (PB) for hypotension after spinal anesthesia for cesarean delivery (CD).
Methods: This is a retrospective chart review of all scheduled CD under spinal anesthesia (12mg bupivacaine, 15 mcg fentanyl and 150 mcg PF morphine) before and after implementation of routine phenylephrine infusions (9/2010) for spinal anesthesia on labor and delivery. Medical charts of patients who underwent CD utilizing prophylactic PI were reviewed from 12/2010-2/2011 and charts from 6/2010-8/2010 were used as historical controls when intermittent phenylephrine boluses were routine. Exclusion criteria included laboring women, general/epidural anesthesia, 3 or more previous CD, BMI >40 kg/m2, multiple gestations, blood loss (> 1000 ml), use of uterotonic agents excluding oxytocin, or blood transfusion. Patient demographics, intraoperative variables, admission temperature, post anesthesia care unit (PACU) admission and discharge temperatures, and total phenylephrine dose were evaluated. Data were compared using a two-sided equal variance T-Test.
Results: There were 133 patients in the PI group and 129 patients in the PB group. There were no differences in demographics, surgical time, fluid administration or blood loss between the PI and PB groups. Baseline temperatures were not significantly different between the groups (median 36.40C in both groups). The mean total dose of phenylephrine was different, the PI group received 1663 mcg vs. the PB group who received 373mcg (P<0.001). The decrease in temperature from baseline to PACU admission was -0.30C (CI= -0.2-0.40C, P<0.001) greater in the bolus group. (Figure)
Discussion: Women who received phenylephrine infusions after spinal anesthesia for CD, had PACU admission temperatures closer to their baseline temperature than those treated with intermittent phenylephrine boluses, suggesting that infusions may protect against postoperative hypothermia in the obstetric population.
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