Spinal anesthesia using hyperbaric 0.75% versus hyperbaric 1% bupivacaine for cesarean section.

UNLABELLED: Although 0.75% hyperbaric bupivacaine is commonly administered to provide spinal anesthesia for cesarean section in the United States, in some countries, only the 1% hyperbaric solution of spinal bupivacaine is available. The aim of this study was to compare 0.75% with 1% hyperbaric spinal bupivacaine for cesarean section. In this prospective study, 50 patients undergoing elective cesarean section were randomized to receive a spinal anesthetic with either 1.5 mL of 0.75% bupivacaine (n = 25) or 1.125 mL of 1% bupivacaine (n = 25). There were no statistically significant differences in patient demographics, time to onset of block, or intraoperative pain. All patients had a successful block for surgery. The time from injection of the spinal anesthetic to first request for pain medication in the postanesthesia care unit was longer in the women who received 0.75% bupivacaine (4.3 vs 3 h; P < 0.05). Six women (24%) who received 1% bupivacaine versus one woman (4%) who received 0.75% bupivacaine complained of postoperative backache (P < 0.05). In addition, postdural puncture headache occurred in four women, all of whom received 1% bupivacaine (P = 0.04). In conclusion, our data suggest that 0.75% bupivacaine results in fewer postoperative problems and offers several significant benefits compared with the 1% concentration. IMPLICATIONS: Although 0.75% bupivacaine is usually used to provide spinal anesthesia for cesarean section in the United States, a more concentrated solution is popular in Europe. In this study, we compared 0.75% bupivacaine with 1% bupivacaine when administered for cesarean section and found that the 0.75% solution offers several significant benefits.

Reversal of extinction by scopolamine.

The aim of this experiment was to determine the effects of muscarinic blockade on extinction of passive avoidance conditioning. Rats were trained with a foot shock of 2.5, 3.0, or 6.0 mA and were tested for retention for 8 weeks (once weekly). Five minutes before the seventh test they were injected with 8 mg/kg scopolamine. The groups that had been trained with 2.5 and 3.0 mA showed extinction, which was reversed by the scopolamine; the overreinforced group (6.0 mA) did not show extinction and the scopolamine did not alter the conditioned response. The data support the hypothesis that extinction represents the learning of a new response sustained by a set of cholinergic neurons, different from that which mediated original passive avoidance learning.