Double-blind randomized trial of 0.75% levobupivacaine compared to 0.75% bupivacaine for epidural anesthesia in patients undergoing major elective abdominal surgery

S281 Introduction. The possibility of severe cardiotoxic reactions after the accidental intravenous injection of racemic bupivacaine has prompted the search for safer long-acting local anesthetic agents [1]. Many practitioners have abandoned the use of the 0.75% concentration, particularly in obstetrics. Bupivacaine is commercially available as only a racemic mixture - a mixture of equal amounts of its L- and R-stereoisomers. The isolated L-isomer, levobupivacaine, when compared to racemic bupivacaine and to the isolated R-isomer, is less cardiotoxic when injected intravenously at equal doses and concentrations in animal and man [2,3], and is currently being developed for use in humans. We report the clinical characteristics of 0.75% levobupivacaine (L) compared to racemic bupivacaine (B) when used for epidural anesthesia. Methods. After Review Board approval and informed consent, 56 ASA I-III patients having major elective abdominal surgery were studied in a randomized, double-blind manner. Epidural anesthesia was initiated with 20 ml (3 ml 'test' dose containing 15 [micro sign]g epinephrine, followed by 17 ml plain solution) 0.75% levobupivacaine or 0.75% racemic bupivacaine over 5 minutes through an 18 gauge Tuohy needle at the L2-3 or L3-4 interspace. Propofol +/- N2 O were provided for sedation / light general anesthesia as desired. Muscle relaxants and volatile anesthetics were excluded. All patients received 3 mg. of epidural morphine after 2 hours. Sensory anesthesia to pinprick was tested at the end of injection, and 2, 5, 10, 15, 20, 25, 30 minutes and every 30 minutes thereafter, until complete resolution of blockade. Motor blockade of the lower extremities (modified Bromage scale) was assessed at 0, 10, 20, 30, and every 30 minutes thereafter. Adequacy of abdominal muscle relaxation were measured using the rectus abdominis muscle (RAM) test and by surgeon and anesthesiologist scoring. Results. The planned surgical procedure was successfully completed in 53 of 56 patients with the initial 20 ml epidural injection; the remaining three patients (1 levobupivacaine and 2 bupivacaine) required a single reinforcement dose (7 ml) of local anesthetic during surgery. Onset and regression of sensory blockade to the T10 dermatome were equivalent between the groups (p=0.78 and p=0.22, respectively). Total duration of sensory was slightly longer with levobupivacaine (*p=0.02). Onset of motor blockade of the abdomen (RAM test >or=to 3) was more rapid than in the lower extremities (Bromage scale >or=to 2) with both drugs, and was rated as 'good' or 'excellent' in 91% of patients. Duration of motor blockade was not significantly different between groups (p=0.31). (Table 1)Table 1Discussion. Levobupivacaine 0.75% produces reliable sensory and motor blockade for major lower abdominal surgery, with an onset and duration of block equivalent to, or better than, that of racemic bupivacaine. As preclinical studies demonstrate a reduced potential for toxicity, levobupivacaine is a safer choice than racemic bupivacaine for epidural anesthesia, especially when the 0.75% concentration is used. Further investigation of levobupivacaine in other regional anesthetic and analgesic techniques, and at additional concentrations for epidural anesthesia and analgesia, is warranted.