Background and objectives: Surgical procedures previously considered too lengthy for the ambulatory surgery setting are now being performed during spinal anesthesia. The complete recovery profile of tetracaine and bupivacaine are now of interest but are not available in the literature. This study was conducted to compare times to ambulation, voiding, and complete block resolution, as well as the incidence of back and radicular pain, after spinal anesthesia with lidocaine, bupivacaine, and tetracaine.
Methods: Twelve adult volunteers underwent spinal anesthesia on three separate occasions with three local anesthetics (lidocaine 100 mg, bupivacaine 15 mg, and tetracaine 15 mg in hyperbaric solutions) in random order and in a double-blind fashion. A 24-gauge Sprotte spinal needle was placed at the L2-3 interspace. The level of analgesia to pinprick was determined moving cephalad in the midclavicular line until a dermatome was reached at which the prick felt as sharp as over an unblocked dermatome. One dermatome caudad to this point was recorded every 5 minutes as the level of analgesia. We also recorded the times to voiding, unassisted ambulation, and complete resolution of sacral anesthesia.
Results: There was no difference between tetracaine and bupivacaine in time taken for two- and four-segment regression of the analgesia level. However, times to ambulation and complete resolution of the block were significantly shorter with bupivacaine then with tetracaine. With lidocaine, times to four-segment regression, ambulation, voiding, and complete regression of the block were significantly shorter than with bupivacaine and tetracaine. Time to two-segment regression did not differ among local anesthetics. Back and radicular pain symptoms were reported by three subjects after lidocaine subarachnoid block but not after tetracaine or bupivacaine.
Conclusion: Among individual subjects, lidocaine exhibited the shortest recovery profile. However, the recovery profiles of the three anesthetics were very variable between subjects. Time to meeting discharge criteria after bupivacaine or tetracaine was faster in a few subjects than that after lidocaine in other subjects. For ambulatory anesthesia, times to two- and four-segment regression do not accurately predict time to readiness for discharge after spinal anesthesia.