Effect of pH adjustment of bupivacaine on onset and duration of epidural anaesthesia.

The effect of pH adjustment of bupivacaine on onset and duration of sensory and motor block was studied in 45 patients undergoing lower abdominal and lower limb surgery. The study was done in 3 groups with the mean pH adjustment of 5.85, 7.14 and 7.21. Each patient was given 30 ml of 0.4% pH adjusted bupivacaine solution in epidural space. Onset of sensory block and duration were noticed by pin-prick method while motor block was observed by asking the patient to raise the thigh. It was observed that increase in pH of bupivacaine solution quickens the onset of sensory and motor block and increases the overall duration of neural blockade.