[Comparison of 8 mg and 10 mg hyperbaric bupivacaine during spinal anesthesia for cesarean section in Japanese parturients].

Background: Hypotension after spinal anesthesia for cesarean section is common and may result in serious complications despite the use of uterine displacement and volume preloading. Adequate amount of hyperbaric bupivacaine for Japanese parturients whose frames are generally smaller than those of Caucasian counterparts have not yet been examined. We compared the analgesic efficacy and the incidence of hypotension with 8 mg versus 10 mg hyperbaric bupivacaine during spinal anesthesia for cesarean section in Japanese parturients.

Methods: Thirty six parturients were randomly divided into two groups, one receiving 8 mg (n = 19) and the other receiving 10 mg (n = 17) hyperbaric bupivacaine. Sensory block level and the incidence of hypotension were evaluated from the time of injection to delivery. Hypotension was defined as a decrease in systolic blood pressure below 100 mmHg and to less than 80% of the baseline value.

Results: 15 minutes after spinal injection, the difference in sensory block level was not significant. Ten minutes after the spinal anesthesia, in 79% of 8 mg group and in 88% of 10 mg group, sensory block level reached T 4. Hypotension occurred in 19 parturients (7 in 8 mg group and 12 in 10 mg group). The incidence of hypotension was significantly lower in 8 mg group (37%) than in 10 mg group (71%). There were no significant differences either in neonatal Apgar scores or umbilical blood gas pH.

Conclusions: Injection of 8 mg hyperbaric bupivacaine is preferable than 10 mg in spinal anesthesia for cesarean section to obtain adequate analgesic efficacy and to avoid maternal hypotension.