Intrathecal Hypobaric Versus Hyperbaric Bupivacaine with Morphine for Cesarean Section

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Abstract
Both hyper- and hypobaric solutions of bupivacaine are often combined with morphine to provide sub- arachnoid anesthesia for cesarean section. Differ- ences in the baricity of subarachnoid solutions influ- ence the intrathecal distribution of anesthetic drugs and would be expected to influence measurable clin- ical variables. We compared the effects of hyper- and hypobaric subarachnoid bupivacaine with morphine to determine whether one has significant advantages with regard to intraoperative anesthesia and postop- erative analgesia in term parturients undergoing elective cesarean section. Thirty parturients were randomized to receive either hyper- or hypobaric bu- pivacaine (15 mg) with morphine sulfate (0.2 mg). Intraoperative outcomes compared included extent of sensory block, quality of anesthesia, and side ef- fects. Postoperative outcomes, including pain visual analog scale scores, systemic analgesic requirements, and side effects, were monitored for 48 h. Sedation effects were quantified and compared using Trieger and digit-symbol substitution tests. We detected no differences in sensory or motor block, quality of an- esthesia, quality of postoperative analgesia, inci- dence of side effects, or psychometric scores. Both preparations provide highly satisfactory anesthesia for cesarean section and effective postoperative anal- gesia. Implications: Dextrose alters the density of in- trathecal bupivacaine solutions and is thought to in- fluence subarachnoid distribution of the drug. We randomized parturients undergoing cesarean section to one of two often used spinal bupivacaine prepara- tions, hypobaric and hyperbaric. We detected no dif- ferences in clinical outcomes between groups. (Anesth Analg 1998;87:33640)