Spinal anaesthesia for paediatric day-case surgery: a double-blind, randomized, parallel group, prospective comparison of isobaric and hyperbaric bupivacaine.

We have compared bupivacaine 5 mg ml-1, either isobaric in saline 0.9% or hyperbaric in 8% glucose, for spinal anaesthesia in 100 children, aged 2-115 months, in a double-blind, randomized, parallel group, prospective study. Children were premedicated with diazepam 0.5 mg kg-1 orally. Seventy-two children were sedated before, and 25 children after, lumbar puncture, with either propofol or thiopental (thiopentone). After lumbar puncture in the lateral decubitus position with a 24-27-gauge paediatric spinal needle, isobaric or hyperbaric bupivacaine 5 mg ml-1 was injected in a dose of 0.3-0.5 mg kg-1 using a blinded procedure. Maximum cephalad extent of the block was tested by transcutaneous electrical stimulation. The success rate of the block was greater with hyperbaric bupivacaine (96%) compared with isobaric bupivacaine (82%) (P = 0.025, 95% confidence intervals (CI) 0-28%). Intense motor block was associated with adequate sensory block. Spread and duration of sensory block showed a similar wide scatter in both groups. The highest median level of sensory block was T4 (range T1-12) in the isobaric group and T4 (T1-7) in the hyperbaric group. Times to two segment regression of block were similar: 80 (55-190) min in the isobaric and 80 (30-190) min in the hyperbaric group. Cardiovascular stability was good. Etilefrin was administered to one child to treat hypotension and atropine to one child to treat bradycardia. The study gave an impression of a delayed onset time of spinal block, as most of the nine children who required either fentanyl or a sedative for a mild reaction to skin incision had complete block when transferred to the recovery room after operation. Five children developed a mild, position-dependent headache.