comparison of Plain 0.25% and 0.5% Bupivacaine for Spinal Anesthesia

Abstract

Background: The extent of sensory and motor block following subarachnoid injection of local anesthetic is thought to depend on several factors such as total dosage and volume of solution. This study was an evaluation of the effects of varying doses and concentrations of plain bupivacaine: 15mg given as 3m1 of 0.5% or as 6ml of 0.25% solution. Methods: In a double-blind trial, 40 patients scheduled for lower extremity surgery were administered, spinal anesthesia using 15 mg bupivacaine, given either as 3.0 ml of plaine 0,5% solution(group 1) or 6m1 of 0.25% solution(group 2). The patients were in a lateral position during the injection and for 3 minutes after. Results: 1) No significant differences were found in onset time and uppermost dermatome level of sensory anesthesia between the two groups. 2) The onset time to complete motor block was 11.6±1.2(group 1), 11.0± 1.4(group 2)([Mean±SE] minutes) in the nondependent leg and 19A±L1(group 1) 18.4±2.0(group 2)([Mean±SE] minutes) in the dependent leg. These differences between nondependent and dependent leg were statistically significant but there were no significant differences between the group 1 and group 2. 3) The systolic and diastolic arterial pressures and heart rate decreased only by about 10 to 15% in both groups; only 3 patients(two in group 1 and one in group 2)required a vasopressor because systolic arterial pressure had decreased by 30% from the preanesthetic value and symptoms resulting from the hypotension and bradycardia were evident. 4) Anesthesia was satisfactory in all patients. Conclusions: In terms of anaesthetic efficacy, there was no significant difference according to either volume or concentration of the plain bupivacaine solution. Either plain 0.25% or 0.5% bupivacaine solution were suitable for lower extremity surgery.