Abstract

Spinal anesthesia using equal dosages (15 mg) of bupivacaine, either as 3.0 ml of a 0.5% or 6.0 ml of a 0.25% glucose-free solution, was compared in a double-blind study including 35 patients scheduled for orthopedic or urologic surgery. There were no differences between the groups with regard to onset time of sensory or motor blockade, segmental level of analgesia, or frequency of different degrees of motor blockade. The mean maximum level of analgesia, T8-9, was reached approximately 20 minutes after injection. Fourteen patients (40%) had complete motor blockade after approximately 15 minutes. Analgesia and muscle relaxation were judged satisfactory for surgery in all patients but one. No statistically significant differences in heart rate or blood pressure were found between the groups. Eleven patients (31%) required ephedrine to treat hypotension. Four patients (11%) suffered from mild to moderate post-lumbar puncture headache. The results from this study show that equal dosages (15 mg) of 0.25% or 0.5% bupivacaine provided equally effective surgical anesthesia. These results indicate that the spread of sensory and motor blockade of bupivacaine are more related to dosage than variations in concentration or volume when used for spinal anesthesia.