BACKGROUND: The purpose of this study is to compare the clinical effects of isobaric 0.5% bupivacaine 8 mg and hyperbaric 0.5% bupivacaine 8 mg on sensory and motor block in aged patients undergoing spinal anesthesia. METHODS: Thirty patients, aged 65 years or more, undergoing orthopedic surgical operation of the lower extremities were randomly assigned to two groups for spinal anesthesia. In the isobaric group (n = 15), isobaric 0.5% bupivacaine 8 mg was administered and in the hyperbaric group (n = 15), hyperbaric 0.5% bupivacaine 8 mg was administered. We measured the maximal sensory level, the time to maximal sensory block, the duration of sensory block, the time to complete motor block, degree of motor block and hemodynamic variables every 2 minutes for 10 minutes in lateral decubitus position and then every 5 minutes for 20 minutes in supine position after spinal anesthesia. RESULTS: The maximal sensory block level and the duration of sensory block were not significantly different between the two groups. The time to maximal sensory block was significantly shorter in the hyperbaric group than in the isobaric group in both lower extremities. The time to complete motor block was significantly longer in the hyperbaric group than in the isobaric group in the nondependent extremity. CONCLUSIONS: These results suggest that isobaric 0.5% bupivacaine 8 mg for spinal anestheisa is more suitable for orthopedic operations requiring rapid and complete motor block than hyperbaric 0.5% bupivacaine 8 mg and that it can be performed in lateral decubitus position with the operating site up.
Anesthesia, Spinal* ; Bupivacaine* ; Extremities ; Hemodynamics ; Humans ; Lower Extremity* ; Orthopedics ; Supine Position