A prospective, double-blinded, randomized, clinical trial comparing the efficacy of 40 mg and 60 mg hyperbaric 2% prilocaine versus 60 mg plain 2% prilocaine for intrathecal anesthesia in ambulatory surgery.

BACKGROUND: In this prospective, double-blind, randomized trial we compared 60 mg and 40 mg of 2% hyperbaric prilocaine with 60 mg of 2% plain prilocaine for spinal anesthesia in terms of sensory block onset in outpatients undergoing elective short-duration (<60 minutes) surgery under spinal anesthesia. METHODS: Ninety patients were enrolled and randomly allocated to receive 1 of the 3 treatments. Times to sensory and motor block onsets, time to the maximum sensory block level, readiness for surgery, time to first urinary voiding, time to Bromage's score 0, and side effects were registered blindly. A blinded observer also questioned patients about transient neurological symptoms 24 hours and 7 days after spinal anesthesia. RESULTS: Mean times to achieve a T10 level of sensory block were comparable in the 3 groups. However, 20% of patients receiving plain prilocaine did not achieve a T10 level. The 2 hyperbaric dosages (60 mg and 40 mg) showed significantly faster times to motor block onset (P = 0.0091, P = 0.0097), to the maximum sensory block level (P = 0.0297, P = 0.0183), to motor block offset (P = 0.0004, P < 0.0001), and to first urinary voiding (P = 0.0013, P = 0.0002, respectively) than did plain prilocaine. No major adverse reactions or transient neurological symptoms were observed in the study. CONCLUSIONS: Spinal anesthesia with 60 mg or 40 mg of 2% hyperbaric prilocaine is comparable to 60 mg of 2% plain prilocaine in terms of onset of sensory block at T10. The hyperbaric solution showed faster times to motor block onset and shorter duration of surgical block, suggesting its superiority for the ambulatory setting.