Prone position results in enhanced pressor response to ephedrine compared with supine position during general anesthesia.

STUDY OBJECTIVE: To elucidate and compare the pressor response to ephedrine in the prone or supine position during general anesthesia (GA). DESIGN: Prospective cohort study. SETTING: Department of General Surgery or Spine Surgery, Zhongda Hospital, Southeast University, Nanjing, China. PATIENTS: Fifty-six patients who were scheduled to undergo elective surgery in the supine or prone position (n = 28 each) and using a generic GA protocol. INTERVENTIONS: During surgery, the patients received intravenous (IV) ephedrine when their systolic blood pressure (SBP) decreased to 90 to 110 mm Hg. MEASUREMENTS: Hemodynamic changes were measured at 1-minute intervals for 10 minutes and were compared with baseline. MAIN RESULTS: Forty-nine patients (23 in the prone position and 26 in the supine position) completed the study. There were no significant differences between the groups with regard to demographic characteristics, hemodynamic parameters, end-tidal concentration of sevoflurane, and dose of propofol and remifentanil (all P> .05). After the bolus injection of ephedrine, a significant increase in SBP was observed in both groups compared to baseline, but the duration and magnitude of the increase in SBP were longer and greater in the prone position than in the supine position. The magnitude of increase of the mean blood pressure was significantly greater in the prone position compared to the supine position at 2 to 7 minutes after ephedrine injection. Ephedrine could cause significant increase in diastolic blood pressure 2 minutes after IV injection, which could last until at least 9 minutes in the prone position group compared to only for 5 minutes in the supine position group (all P< .05). CONCLUSION: Compared to the supine position, the prone position could augment the pressor response to IV ephedrine during GA. Further studies are recommended to identify its association with other confounding factors such as surgery type or duration, patient history of cardiovascular disease, or patient hydration status.