• Gregory L Bryson, Robert Macneil, Leo M Jeyaraj, and Ola P Rosaeg.
• Department of Anesthesiology, The Ottawa Hospital, Ottawa, Ontario, Canada. glbryson@ohri.ca
• Can J Anaesth. 2007 Jul 1;54(7):531-7.

BackgroundMaternal hypotension occurs in 60-94% of Cesarean deliveries with 10-15 mg spinal bupivacaine. Reduced doses of bupivacaine may decrease the incidence of hypotension, nausea, and vasopressor use. The primary objective of this study was to compare 4.5 mg and 12 mg doses of intrathecal bupivacaine on maternal hemodynamics. The secondary objective was to determine if anticipated reductions in side effects were reflected in increased patient satisfaction.MethodsFollowing Research Ethics Board approval and informed consent 52 term parturients undergoing elective Cesarean delivery were randomly assigned to isobaric bupivacaine 4.5 mg or hyperbaric bupivacaine 12 mg for spinal anesthesia. All patients received fentanyl 50 microg and morphine 200 microg intrathecally. Intravenous fluid and vasopressor administration were standardized. Maternal hemodynamics, and sensorimotor levels were recorded at regular intervals. Side effects and patient satisfaction were documented.ResultsMedian cepahalad sensory block was C8 in both groups (NS) but the intensity of motor block was significantly less (P < 0.001) and of shorter duration (P < 0.001) with bupivacaine 4.5 mg. The proportion of patients requiring ephedrine (> 70%) and the quantities of ephedrine used were similar in both groups (NS). Use of supplemental analgesia, side effects, and measures of patient satisfaction were comparable in both groups.DiscussionIntrathecal bupivacaine 4.5 and 12 mg yielded similar sensory block and side effects during Cesarean delivery. Patients receiving 4.5 mg did, however, experience significantly less motor blockade of shorter duration.

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