Hypobaric 0.15% bupivacaine versus hypobaric 0.6% lidocaine for posterior spinal anesthesia in outpatient anorectal surgery.

BACKGROUND AND OBJECTIVES Low doses of bupivacaine and lidocaine have been used for spinal anesthesia in outpatient surgery. The objective of this study was to compare hypobaric solutions of bupivacaine and lidocaine in outpatient anorectal surgery. METHODS One hundred and fifty patients, divided in two groups, physical status ASA I-II, scheduled for anorectal surgery in the jackknife position received 3 mL (4.5 mg) of hypobaric 0.15% bupivacaine or 3 mL (18 mg) of hypobaric 0.6% lidocaine. The selectivity of the blockade, quality of surgical anesthesia, intensity of the motor blockade, and time for patient recovery were compared. After patients were discharged, daily phone contact was maintained for three days and on the 30th postoperative day. RESULTS Adequate surgical blockade was achieved in all patients. The mean level of cephalad dispersion was L(1), ranging from T(10)-L(3), with bupivacaine, and L(1), ranging from T(11)-L(2), with lidocaine. Motor blockade was not observed in 135 patients (65 in the bupivacaine group x 70 in the lidocaine group). None of the patients developed hypotension and bradycardia. The sensorial blockade had a mean duration of 99.1 (11.0) minutes, with bupivacaine, and 64.1 (7.6) minutes, with lidocaine (p < 0.0005). Post-lumbar puncture headache was not observed in any patient. CONCLUSIONS Hypobaric solution of bupivacaine or lidocaine promotes, predominantly, sensorial blockade after subarachnoid injection in patients in the jackknife position. Hypobaric lidocaine provides analgesia with the same dispersion of that of bupivacaine, but with shorter duration. Hemodynamic stability and the absence of motor blockade represent the major advantages.