Low-dose spinal hyperbaric bupivacaine for adult anorectal surgery: a double-blinded, randomized, controlled study

Background and objectiveTo produce selective spinal anesthesia for adult anorectal surgery.Study designDouble-blinded, randomized, controlled trial.SettingOperating room and postoperative recovery area.Patients152 adult, consecutive ASA physical status I, II, and III patients.InterventionsAfter patients underwent dural puncture in the sitting position at L3-L4 or L4-L5, 0.5% hyperbaric bupivacaine was injected over two minutes: Group S7.5 received 1.5 mL, Group S5 received 1.0 mL, and Group S4 0.8 mL. After sitting for 10 minutes, patients were positioned for surgery.MeasurementsRate of success, level and duration of sensory and motor block, time to voiding and ambulation, complications, and quality of anesthesia according to the patient and medical staff, were recorded.ResultsSpinal block had a 98% rate of success. Mean level of sensory block was 10.4 ± 1.7, 7.4 ± 2.2, and 7.0 ± 1.8 dermatomes in Groups S7.5, S5, and S4 (P < 0.01 S7.5 vs S5, and S7.5 vs S4). Mean duration of sensory block was 310.5 ± 42.6, 255.9 ± 43.7, and 228.8 ± 34.8 min in Groups S7.5, S5, and S4 (P < 0.01 S7.5 vs S5, S7.5 vs S4, and S5 vs S4). Motor block was Bromage score 2-3 in 70.5% of Group S7.5 patients versus Bromage score 0-1 in 97.3% of Group S5 and 92.1% of Group S4 patients (P < 0.05).ConclusionA dose of 4 mg of hyperbaric bupivacaine produces a similar level of sensory and motor block as a 5 mg dose but with shorter duration and faster recovery.