Spinal anaesthesia with hyperbaric 0.5% bupivacaine: effects of volume.

Different volumes (1.5, 2, 3 and 4 ml) of hyperbaric 0.5% bupivacaine (8% glucose) were compared in spinal anaesthesia for urological surgery in 40 patients. The blockade was given with the patient in the sitting position. Two minutes after the injection the patient was placed in the lithotomy position. The time required for maximum cephalad spread of analgesia was about 20 min for all volumes. The maximum cephalad spread was directly related to log volume of the local anaesthetic solution. The onset time for motor blockade of the lower limbs decreased and the frequency increased with increasing volume. Four ml produced complete blockade in all patients. The duration of analgesia increased with increasing volume: 3-4 ml produced analgesia at T8 for 1.5-2.5 h and at L1 for 2-3 h. With this volume, complete motor blockade was obtained for 1.5-2.5 h. Satisfactory surgical anaesthesia for transurethral resection was obtained with 3-4 ml of the local anaesthetic solution.