A comparative study of low-dose hyperbaric spinal lidocaine 0.5% versus 5% for continuous spinal anesthesia

Concerns of cauda equina syndrome have discouraged clinicians to use 5% lidocaine for continuous spinal anesthesia. Earlier reports indicated that single-shot spinal lidocaine 0.5% is effective for minor gynecologic and perianal surgery. In 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 urologic surgery.

Spinal anesthesia was induced via an indwelling subarachnoid catheter in 42 elderly male patients (range, 57-84 years) undergoing transurethral prostate and bladder procedures. Patients were randomly assigned to receive an initial 30-mg bolus of hyperbaric lidocaine in the form of either 6 mL of 0.5% solution or 0.6 mL of 5% solution. Additional 30-mg boluses (to a total of 90 mg) were given, if necessary, to establish initial sensory block to T10 or higher and lower limb paralysis. Supplemental doses of 30 mg or less were given during surgery, as needed. Dermatomal level of sensory anesthesia and degree 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.

Forty patients were studied successfully. Both hyperbaric 0.5% and 5% lidocaine provided adequate surgical anesthesia in 75% (30/40) of patients after a single 30-mg dose. A median peak sensory level of T5 (range, T2-T9) achieved 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 after a 30-mg dose was similar in both groups--48.1 +/- 12.1 minutes versus 50.8 +/- 16.5 minutes respectively. Of the 30 patients (15 in each group) who received 30 mg initially, 25 required repeat lidocaine dosing 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 five patients in the 0.5% group 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 (90 mg).

Continuous spinal anesthesia produced by 0.5% lidocaine with 7.5% dextrose is as effective as that produced by the 5% lidocaine solution in elderly patients undergoing urologic surgery. An initial 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.