SPINAL ANAESTHESIA WITH HYPERBARIC BUPIVACAINE: EFFECTS OF CONCENTRATION AND VOLUME ADMINISTERED

A double-blind study was earned out using hyperbaric solutionsof bupivacaine to compare the effects of varying the concentrationof bupivacaine and the volume of solution administered intrathecallyFifty-seven patients were studied. Ten patients received eachvolume of each concentration: 0.5% bupivacaine in 8% dextrose,2 ml, 3 ml or 4 ml and 0.75% bupivacaine in 8% dextrose, 1.3ml or 2 ml A further seven patients received 3 ml of the 0.75%solution Both solutions consistently produced good nerve blockade.With the 0.5% solution, increases in the volume administeredhad no effect on the spread of sensory loss, whereas with the0 75% solution, increasing the volume administered resultedin a significantly greater cephalad spread. The use of 3 mlof this solution was abandoned after seven patients had receivedit because of the excessive spread. With both solutions, increasingthe volume produced a longer duration of action. The use ofa 0 75% solution of hyperbaric bupivacaine for spinal anaesthesiadid not appear to confer any advantage over the 0.5% solution.