Baseline heart rate may predict hypotension after spinal anesthesia in prehydrated obstetrical patients.

PURPOSE: Hypotension is the most frequent complication of spinal anesthesia in pregnant patients. This study was designed to identify patients at risk for postspinal hypotension based on preoperative vital signs before and after an orthostatic challenge.

METHODS: Forty healthy women scheduled for elective Cesarean section were enrolled in this prospective trial. Blood pressure (BP) and heart rate (HR) were recorded with the patient in the lateral supine position and after standing up. After a bupivacaine spinal anesthetic, BP was obtained every two minutes for 30 min. Ephedrine treatment was administered based on the degree of hypotension observed. Hemodynamic parameters were correlated to ephedrine requirements (Spearman's rank order correlation).

RESULTS: There was a significant correlation in baseline maternal HR and ephedrine requirements (P=0.005). The degree of orthostatic changes in mean arterial BP and HR did not correlate with postspinal hypotension.

CONCLUSIONS: Baseline HR may be predictive of obstetric spinal hypotension. Higher baseline HR, possibly reflecting a higher sympathetic tone, may be a useful parameter to predict postspinal hypotension.