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

To produce selective spinal anesthesia for adult anorectal surgery.

Double-blinded, randomized, controlled trial.

Operating room and postoperative recovery area.

152 adult, consecutive ASA physical status I, II, and III patients.

After 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.

Rate 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.

Spinal 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).

A 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.