A comparison of minidose lidocaine-fentanyl and conventional-dose lidocaine spinal anesthesia

The syndrome of transient neurologic symptoms (TNS) after spinal lidocaine has been presumed to be a manifestation of local anesthetic neurotoxicity. Although TNS is not associated with either Lidocaine concentration or dose, its incidence has never been examined with very small doses of spinal lido caine. One hundred ten adult ASA physical status I and II patients presenti ng for arthroscopic surgery of the knee were randomly assigned to receive s pinal anesthesia with either 1% hypobaric lidocaine 50 mg (Group WO) or 1% hypobaric lidocaine 20 mg + 25 mu g fentanyl (Group L20/F25). Hemodynamic d ata, block height and regression, and time to first micturition and dischar ge were recorded. Follow-up phone calls were made by a blinded researcher a t 48-72 h using a standardized questionnaire. Both groups had a median peak cephalad block level of T10. Lidocaine 50 mg was associated with a greater decrease in systolic blood pressure and a greater need for ephedrine. Time until block regression to the S2 dermatome (80 vs 110 min) and outpatient time to void (130 vs 162 min) and discharge (145 vs 180 min) were faster in the L20/F25 group. Complaints of TNS were found in 32.7% of the patients i n the L50 group and in 3.6% of the patients in the L20/F25 group. We conclu de that spinal anesthesia with lidocaine 20 mg + fentanyl 25 mu g provided adequate anesthesia with greater hemodynamic stability and faster recovery than spinal anesthesia with lidocaine 50 mg. The incidence of TNS after spi nal lidocaine 20 mg + fentanyl 25 mu g was significantly less than that aft er spinal lidocaine 50 mg.