A comparison of glucose 8mg/ml or glucose 80mg/ml with bupivacaine 5mg/ml for spinal anesthesia for cesarian section

Objectives: 1 ) To assess the onset, spread, quality and duration of spinal anaesthesia for Cesarian section with bupivacaine 5mg/ml in glucose 8mg/ml or glucose 80mg/ml. 2) To assess the cardiovascular stability of the patients receiving each solution . Methods: 40 women (aged 18-40 yr) undergoing elective Cesarian section gave informed consent for the study which was approved by the local medical ethics committee. Patients were placed in the right lateral position, with a pillow under the dependent shoulder. Under aseptic conditions the spinal injection was made with a 25 gauge Whitacre needle at the L3/4 level, and with the needle port facing cephalad. The study solution (2.5ml) was injected at 1.0ml per 5 seconds, and the end of injection was defined as time zero. The study solution in group A was bupivacaine 5mg/ml with dextrose 8mg/ml, and in group B bupivacaine 5mg/ml with dextrose SOmg/ml. Patients were immediately placed in the left wedged position. Level of sensory block was determined using the blunt end of a 27 gauge dental needle at 2, 5, 10, 15, 20, 25, 30 minutes after injection, and every 15 minutes for two hours thereafter. The extent of block was measured on both sides and an average taken if there was a difference. Blood pressure was measured before the procedure, every 2 minutes for 10 minutes, and every 5 minutes for 2 hours. Hypotension (defined as a systolic blood pressure more than 20% below the preoperative figure, or symptoms related to poor perfusion eg nausea, dizziness) was treated with 6mg ephedrine intravenously as required. The spinal anaesthetic was supplemented, with increments of either alfentanil or morphine as required. Post-operatively all patients received diclofenac lOOmg per rectum, unless there was a contraindication. The time to first morphine requirement was noted, and the first bolus was given intravenously by the investigator. Thereafter PCA morphine was used. Results : There was no difference between the two groups in mean age, height or weight. The speed of onset of sensory blockade was significantly faster in group A (dextrose 8mg/ml) than group B (80mg/ml), the median levels at 5 minutes being T8 and T10. Every patient had a sensory block to at least T4 at 20 minutes, and median maximum block height was virtually the same in both groups, although 4 patients in group A had a block to C3 at 25 minutes. Five patients in group A and 8 patients in group B required supplementation with opioid after delivery. Patient satisfaction scores were equivalent in the two groups with all patients feeling that anaesthesia was satisfactory. There was a difference between the 2 groups in regression of the sensory block height (group B faster than group A), but there was no difference in the mean time to first request for morphine. There was no difference between the groups in regard to maternal pulse rate, or systolic and diastolic blood pressures. Ephedrine requirements in the two groups were not significantly different. Discussion: Studies in non-pregnant subjects have suggested that concentrations of glucose much lower than those normally used for spinal anaesthesia might have advantages (1,2). The aim of this study was to see if these advantages applied to the obstetric patient at term. In spite of a tenfold difference in glucose concentration there were only minor differences between the resulting blocks. This suggests that solution baricity is of relatively little importance in spinal anesthesia at term.