Subarachnoid analgesia for caesarean section. A double-blind comparison of plain and hyperbaric 0.5% bupivacaine.

Equal volumes (2.5 ml, 12.5 mg) of plain 0.5% bupivacaine (glucose-free) and hyperbaric 0.5% bupivacaine (in 8% glucose) were compared in a randomized double-blind study of 40 patients undergoing Caesarean section under subarachnoid anaesthesia. There were no differences in the rate of onset, maximum spread, number of patients with high cervical levels, duration of anaesthesia or incidence of post-spinal headaches between the two solutions. The median maximum cephalad levels of analgesia were (hyperbaric) T1 (range C1-T4), and (plain) T2 (range C1-T4). Thirteen patients in the hyperbaric group and 10 in the isobaric group required i.v. ephedrine to treat hypotension. Nine patients (23%) developed a post-spinal headache, and three were treated with an extradural blood patch.