Abstract:Background: Spinal hyperbaric ropivacaine may produce more predictable and reliable anesthesia than plain ropivacaine for cesarean section. The dose-response relation for spinal hyperbaric ropivacaine is undetermined. This double-blind, randomized, dose-response study determined the ED50 (50% effective dose) and ED95 (95% effective dose) of spinal hyperbaric ropivacaine for cesarean section anesthesia. Methods: Sixty parturients undergoing elective cesarean section delivery with use of combined spinal-epidural anesthesia were enrolled in this study. An epidural catheter was placed at the L1~L2 vertebral interspace, then lumbar puncture was performed at the L3~L4 vertebral interspace, and parturients were randomized to receive spinal hyperbaric ropivacaine in doses of 10.5 mg, 12 mg, 13.5 mg, or 15 mg in equal volumes of 3 ml. Sensory levels (pinprick) were assessed every 2.5 min until a T7 level was achieved and motor changes were assessed by modified Bromage Score. A dose was considered effective if an upper sensory level to pin prick of T7 or above was achieved and no intraoperative epidural supplement was required. ED50 and ED95 were determined with use of a logistic regression model. Results: ED50 (95% confidence interval) of spinal hyperbaric ropivacaine was determined to be 10.37 (5.23~11.59) mg and ED95 (95% confidence interval) to be 15.39 (13.81~23.59) mg. The maximum sensory block levels and the duration of motor block and the rate of hypotension, but not onset of anesthesia, were significantly related to the ropivacaine dose. Conclusion: The ED50 and ED95 of spinal hyperbaric ropivacaine for cesarean delivery under the conditions of this study were 10.37 mg and 15.39 mg, respectively. Ropivacaine is suitable for spinal anesthesia in cesarean delivery.

Emerging evidence has demonstrated that exposure to anesthetics early in life caused neurohistopathologic changes and persistent behavioral impairments. In this study, a maternal fetal rat model was developed to study the effects of isoflurane exposure during pregnancy on postnatal memory and learning in the offspring. Pregnant rats at gestational day 14 were either exposed to 1.3% isoflurane in a humidified 100% oxygen carrier gas or simply humidified 100% oxygen without any inhalational anesthetic for 2 h every day before delivery. Four weeks later, spatial learning and memory of the offspring were examined using the Morris Water Maze. The expression levels of GAP-43 and NPY in the hippocampal CA1 region of the pups were determined by immunohistochemistry and RT-PCR. Simultaneously, the ultrastructure changes in synapse of the hippocampus were also observed by transmission electron microscopy (TEM). Isoflurane exposure during pregnancy impaired postnatal spatial memory and learning in the offspring as shown by the longer escape latency and the fewer original platform crossings in the Morris Water Maze test. The number and optical densities of GAP-43 and NPY positive cells, as well as the levels of GAP-43 and NPY mRNA, decreased significantly in the hippocampus of isoflurane-exposed pups. Furthermore, TEM studies showed remarkable changes in synaptic ultrastructure of hippocampus. These results indicate that isoflurane exposure during pregnancy could cause postnatal spatial memory and learning impairments in offspring rats, which may be partially explained by the down-regulation of GAP-43 and NPY in the hippocampal area.

Purpose Remimazolam has demonstrated the potential as a valuable medication for procedural sedation. However, there were some shortcomings for higher doses of remimazolam during hysteroscopy in spite of less frequent adverse events. The aim of this study was to find the 50% and 95% effective dose (ED 50 and ED 95 ) of remimazolam when combined with propofol for intravenous sedation during day-surgery hysteroscopy. Patients and Methods Patients were randomly assigned evenly (20 per group) to one of five different dosage of remimazolam: group A (0.05mg/kg), group B (0.075mg/kg), group C (0.1mg/kg), group D (0.125mg/kg) or group E (0.15mg/kg). Intravenous injection of sufentanil 0.1µg/kg was administered before sedative medication. Intravenous anesthesia was commenced with remimazolam. Subsequently, propofol was administered at 1mg/kg and maintained at 6mg/kg/h. Success was defined when the patient did not move during cervical dilation, had sufficient sedation as judged by SE <60 and no requirement for rescue doses. The success rate, induce and average dosage of propofol, the induction time, total surgery time, recovery time, and adverse events were recorded. Estimate of ED 50 and ED 95 with 95% confidence interval (CI) was performed by probit regression. Results The mean (95% CI) values for ED 50 and ED 95 of remimazolam in patients were 0.09 (0.08−0.11) mg/kg and 0.21 (0.16–0.35) mg/kg, respectively. There was no difference in the induction time, total surgery time, and recovery time among groups. No serious adverse events occurred in all patients. Conclusion The dose–response effects of remimazolam were evaluated for intravenous sedation during hysteroscopy. A combination of remimazolam and propofol was recommended to produce stabler sedation, reduce the total dosage and have less effect on cardiovascular and respiratory depression.