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OBSTETRIC ANESTHESIA

Prophylactic Phenylephrine Infusion for Preventing Hypotension During Spinal Anesthesia for Cesarean Delivery

Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong, China

Address correspondence to Warwick D. Ngan Kee, MBChB, MD, FANZCA, Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong, China. Address e-mail to warwick{at}cuhk.edu.hk Reprints will not be available.

In a randomized, double-blinded, controlled trial, we investigated the prophylactic infusion of IV phenylephrine for the prevention of hypotension during spinal anesthesia for cesarean delivery. Immediately after intrathecal injection, phenylephrine was infused at 100 µg/min (n = 26) for 3 min. From that point until delivery, phenylephrine was infused at 100 µg/min whenever systolic arterial blood pressure (SAP), measured each minute, was less than baseline. A control group (n = 24) received IV bolus phenylephrine 100 µg after each measurement of SAP <80% of baseline. Phenylephrine infusion decreased the incidence (6 [23%] of 26 versus 21 [88%] of 24; P < 0.0001), frequency, and magnitude (median minimum SAP, 106 mm Hg; interquartile range, 95–111 mm Hg; versus median, 80 mm Hg; range, 73–93 mm Hg; P < 0.0001) of hypotension compared with control. Heart rate was significantly slower over time in the infusion group compared with the control group (P < 0.0001). Despite a large total dose of phenylephrine administered to the infusion group compared with the control group (median, 1260 µg; interquartile range, 1010–1640 µg; versus median, 450 µg; interquartile range, 300–750 µg; P < 0.0001), umbilical cord blood gases and Apgar scores were similar. One patient in each group had umbilical arterial pH <7.2. Prophylactic phenylephrine infusion is a simple, safe, and effective method of maintaining arterial blood pressure during spinal anesthesia for cesarean delivery.

IMPLICATIONS: In patients receiving spinal anesthesia for elective cesarean delivery, a prophylactic infusion of phenylephrine 100 µg/min decreased the incidence, frequency, and magnitude of hypotension with equivalent neonatal outcome compared with a control group receiving IV bolus phenylephrine.

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