Effect of lateral posture on epidural blockade for surgery

In a prospective double-blind study, single-dose lumbar epidural blockade was administered to 60 healthy patients undergoing lower abdominal surgery, the patients lying in the lateral position only during the time of injection of the local anaesthetic. Solutions used were bupivacaine HCl 0.5%, lignocaine HCl 2% and lignocaine-bupivacaine mixtures in the ratios of 1:3, 1:1 and 3:1 by volume. Data were pooled and analysed for the effects of posture on epidural blockade. Using skin temperature as a criterion of sympathetic blockade, onset of blockade was more rapid and there was more prolonged blockade on the dependent side. Initial onset of sensory blockade was faster on the dependent side by 1 minute and 3.1 minutes for partial and complete blockade, respectively. Mean duration of sensory blockade was longer in the dependent dermatomes for partial (14, SD 7, minutes, T6-L4) and complete blockade (20, SD 6, minutes, T8-L3) respectively. Initial onset of complete motor blockade was 5 minutes more rapid on the dependent side, with mean myotome score consistently greater at all time intervals on the dependent side. Our study therefore suggests that a more efficacious sensory and motor blockade could be achieved by lying the patient on the operative side during the administration of the epidural and injection of the local anaesthestic solution close to the operative dermatomes.