A COMPARATIVE-STUDY OF LOW-DOSE HYPERBARIC SPINAL LIDOCAINE 0.5-PERCENT VERSUS 5-PERCENT FOR CONTINUOUS SPINAL-ANESTHESIA

Background and Objectives. concerns of cauda equina syndrome have disc ouraged clinicians to use 5% lidocaine for continuous spinal anesthesi a. Earlier reports indicated that single-shot spinal lidocaine 0.5% is effective for minor gynecologic and perianal surgery. Ln the present study, we evaluate the anesthetic and hemodynamic effects of low dose hyperbaric 0.5% lidocaine for continuous spinal anesthesia and compare with those of the 5% lidocaine solution in patients undergoing urolog ic surgery. Methods. Spinal anesthesia was induced via an indwelling s ubarachnoid catheter in 42 elderly male patients (ran,ae, 57-84 years) undergoing transurethral prostate and bladder procedures. Patients we re randomly assigned to receive an initial 30-mg bolus of hyperbaric l idocaine in the form of either 6 mL of 0.5% solution or 0.6 mt of 5% s olution. Additional 30-mg boluses (to a total of 90 mg) were given, if necessary, to establish initial sensory block to T10 or higher and lo wer limb paralysis. Supplemental doses of 30 mg or less were given dur ing surgery, as needed. Dermatomal level of sensory anesthesia and deg ree of motor blockade were assessed at regular intervals by a blinded observer. Heart rate and blood pressure (mean systolic and diastolic) values were monitored at regular intervals. Results. Forty patients we re studied successfully. Both hyperbaric 0.5% and 5% lidocaine provide d adequate surgical anesthesia in 75% (30/40) of patients after a sing le 30-mg dose. A median peak sensory level of T5 (range, T2-T9) achiev ed within 11.1 +/- 4.5 minutes in patients receiving the 0.5% solution was significantly higher than the peak sensory level of T7 (range, T4 -T12) in the 5% group (P =.043). The duration of surgical anesthesia a fter a 30-mg dose was similar in both groups-48.1 +/- 12.1 minutes ver sus 50.8 +/- 16.5 minutes respectively. Of the 30 patients (15 in each group) who received 30 mg initially, 25 required repeat lidocaine dos ing through the catheter during surgery. The maximum decrease in heart rate and blood pressure values was within 10% and 20%, respectively, of baseline values in both groups. In the remaining patients (10/40), anesthesia was achieved successfully in live patients in the 0.5% grou p and three patients in the 5% group after two 30-mg lidocaine boluses (60 mg) and two patients in the 5% group after three 30-mg boluses (9 0 mg). Conclusions. Continuous spinal anesthesia produced by 0.5% lido caine with 7.5% dextrose is as effective as that produced by the 5% li docaine solution in elderly patients undergoing urologic surgery. An i nitial 30-mg bolus delivered via indwelling subarachnoid catheter was sufficient to achieve surgical anesthesia for approximately 50 minutes in most patients. Hemodynamic effects of the two lidocaine solutions were also comparable.