THE EFFECT OF EPINEPHRINE ON SMALL-DOSE HYPERBARIC BUPIVACAINE SPINAL-ANESTHESIA - CLINICAL IMPLICATIONS FOR AMBULATORY SURGERY

The effect of adding epinephrine to small doses of spinal bupivacaine on the duration of sensory motor block has not been carefully investig ated. Twelve volunteers underwent hyperbaric bupivacaine spinal anesth esia (7.5 mg) with and without epinephrine (0.2 mg) in a randomized, d ouble-blind, cross-over fashion. Sensory block was assessed with pinpr ick, transcutaneous electrical stimulation (TES) equivalent to surgica l stimulation (at umbilicus, pubis, knee, and ankle), and tolerance of a pneumatic thigh tourniquet. Motor block was assessed with isometric force dynamometry. Discharge criteria were defined as return of pinpr ick sensation to dermatome S2, ability to ambulate, and ability to uri nate. Extent of sensory block to pinprick over time was unaffected by the addition of epinephrine. However, epinephrine prolonged tolerance of TES at the pubis, knee, and ankle (33-48 min, P < 0.05) and of thig h tourniquet (30 min, P < 0.01). Motor block was prolonged by epinephr ine at the quadriceps and gastrocnemius muscles (by 23 and 51 min, res pectively, P < 0.002). Achievement of discharge criteria was prolonged by 48 min by the addition of epinephrine (P < 0.01). Thus, epinephrin e may prolong surgical anesthesia for lower abdominal and lower extrem ity surgery and delay time until patients achieve discharge criteria. Implications: Using a cross-over study design, 12 volunteers underwent bupivacaine spinal anesthesia with and without epinephrine. This stud y suggests that adding epinephrine to bupivacaine may prolong surgical anesthesia and also delay patients' discharge.