Low dose of lidocaine: comparison of 15 with 20 mg/ml with dextrose for spinal anesthesia in lithotomy position and ambulatory surgery

Abstract

Spinal anesthesia with the local anesthetic lidocaine has come under scrutiny because it is associated with transient neurologic symptoms (TNS). Although TNS is not associated with either lidocaine concentration or dose, its incidence has never been examined with very small doses of hyperbaric spinal lidocaine in patients in the lithotomy position. We designed this study prospectively to compare the efficacy of low-dose 15 mg/ml with low-dose 20 mg/ml hyperbaric lidocaine in patients undergoing elective outpatient surgery in the lithotomy position. A total of 100 patients were randomized to receive either 30 mg of 15 mg/ml or the same dose of 20 mg/ml hyperbaric lidocaine. Lidocaine density at 37 degrees C is 1.0241 g/ml for the 15 mg/ml and 1.0260 g/ml for the 20 mg/ml solution. Patients were examined for motor block, sensory block, and block duration. Patients were contacted at 24, 48 and 72 h and questioned about their perceptions of pain after the spinal anesthesia with specific questions designed to diagnose TNS. The spread of analgesia was the same with both solutions of lidocaine. Motor block was incomplete in all patients in both groups. TNS were not observed when low doses of both solutions of lidocaine with dextrose were used in these ambulatory patients in the lithotomy position. Hyperbaric lidocaine results in rapid recovery from sensory block and motor blockade. It may have advantages for patients in a day-case setting. No patients complained of TNS after discharge.