Prospective evaluation of systolic arterial pressure control with a phenylephrine infusion regimen during spinal anaesthesia for caesarean section

Background: Hypotension and nausea occur frequently during spinal anaesthesia for caesarean section. The aim of this evaluation was to assess systolic arterial pressure control with our routine prophylactic intravenous phenylephrine infusion regimen. We audited a local standard for an incidence of hypotension of <= 25% during the first 15 min of anaesthesia. Methods: One hundred healthy women undergoing elective caesarean section were assessed. Following intravenous preload with 10 mL/kg Hartmann's solution, 0.5% hyperbaric bupivacaine 2.8 mL combined with diamorphine 400 was given intrathecally in the sitting position. Intravenous phenylephrine was then started at 67 mu g/min (the maximum rate). Systolic arterial pressure was recorded every 2 min. The infusion was titrated, according to local guidelines, to maintain systolic arterial pressure close to baseline. Results: The median dose of phenylephrine given by infusion was 1000 [interquartile range 670-1000] mu g, with 51 patients not requiring any change to the infusion rate. Eleven patients (11%, 95% CI 6-19) developed hypotension, defined as a systolic arterial pressure <80% of baseline. A further four patients were given a bolus of phenylephrine for suspected hypotension. The incidence of hypotension. or suspected hypotension was therefore 15% (95% CI 9-24). Thirteen patients (13%, 95% CI 7-21) developed nausea. No patient vomited. Conclusions: Our routine phenylephrine infusion regimen was effective at minimizing hypotension and nausea during relatively high-dose spinal anaesthesia. This was achieved with a low intervention rate, in conjunction with a 2-min rather than a 1-min non-invasive blood pressure cycle time and a relatively low volume of intravenous fluid. (C) 2012 Elsevier Ltd. All rights reserved.