Effectiveness of Isobaric Bupivacaine Saddle Blocks in Pelvic Surgery

Abstract

Background: Saddle anaesthesia entails a selective spinal anaesthetic technique that directs a small dose of local anaesthetic towards sacral and coccygeal nerve roots, ideal for short gynaecological and urological surgery. It uses a long-acting local anaesthetic. The use of 1ml 0.5% bupivacaine (5mg) has been shown to be effective for spinal anaesthesia in other settings but local data on the effectiveness of this dose for surgical procedures is lacking. Study objectives: The study aimed to determine the effectiveness of 1ml 0.5% isobaric bupivacaine (5mg) used in saddle blocks for short urological and gynaecological procedures using the following parameters: level and duration of sensory and motor blockade, and the adverse effect profile. Haemodynamic stability, time to ambulate and time to void were also assessed. Patients and methods: 44 patients ASA I and II patients were recruited into the study. In theatre, they were positioned seated and 1ml of 0.5% isobaric bupivacaine was administered intrathecally. They all sat for 10 minutes and then put in lithotomy position. Level of sensory and motor blockade were noted at induction and at the end of surgery. Duration of block was also recorded. Adverse effects, time to first ambulation and voiding were noted during the perioperative period. Results: Female patients were 97.7%, males were 2.3%. The mean BMI was 24.6 (15.9-33). Mean surgery time was 54.5 minutes (15-90). ASA I were 52%, and ASA II 48%. At induction, level of sensory blockade was S2-S5, and level of motor blockade was between 1 and 4. Duration of sensory blockade was 127.2 minutes (88-143), and motor blockade 137.2 minutes (98-200). There were no cases of post-dural puncture headache, but 2.3% had nausea and vomiting, and 11.4% had hypotension. Conclusion: 5mg of isobaric bupivacaine is adequate for perineal surgery giving a dense sensory block lasting over 2 hours, motor blockade up to level 4 on induction lasting 137 minutes, and minimal incidence of nausea-vomiting, hypotension, and post-dural puncture headache.