Spinal analgesia with hyperbaric bupivacaine: effects of volume of solution.

The effects of 0.5% bupivacaine 1.5, 2 and 3 ml in 8% glucose was compared in a double-blind study involving 30 patients undergoing spinal analgesia. The time to the onset of maximum segmental spread of analgesia was approximately 15 min for all three volumes. Cephalad spread of analgesia was related to the volume used: 1.5 ml reached T10, 2 ml T8 and 3 ml T7. The duration of analgesia increased with increasing volume, 3 ml producing analgesia in T8-T12 for 1.5-2 h, and in the lumbar region for 2.5-3 h. Increasing the volume increased the extent of motor blockade and speeded up its onset. Significant decreases in arterial pressure were observed in the 2- and 3-ml groups. The changes in heart rate were moderate and not correlated with the amount of drug. Spinal headache occurred in two patients.