Comparative study of intrathecal pethidine versus lignocaine as an anaesthetic and a postoperative analgesic for perianal surgery.

100 patients with ASA risk I & II and undergoing perianal surgery were studied for anaesthetic effects and postoperative analgesia following either intrathecal pethidine or lignocaine. Saddle block was performed either with intrathecal pethidine 5% (50 mg/ml) 0.5 mg/kg or 1 ml of 5% lignocaine. Sensory and motor block postoperative analgesia, need for additional analgesia were studied. The onset of sensory and motor blockade with lignocaine was faster than pethidine. However the sensory and motor blockade lasted longer with pethidine. The duration of postoperative analgesia was 15.39 +/- 5.14 hours as against duration of postoperative analgesia with lignocaine which was 1.3 +/- 0.53 hours. Only 10% of patients in the pethidine group required intramuscular analgesic supplementation whereas 30% of patients in the lignocaine group required intramuscular analgesic supplementation.