Procaine compared with lidocaine for incidence of transient neurologic symptoms

Background and Objectives: Transient neurologic symptoms (TNS) have been re ported to occur after 16% to 40% of ambulatory lidocaine spinal anesthetics . Patient discomfort and the possibility of underlying lidocaine neurotoxic ity have prompted a search for alternative local anesthetic agents. We comp ared the incidence of TNS with procaine or lidocaine spinal anesthesia in a 2:1 dose ratio. Methods: Seventy outpatients undergoing knee arthroscopy were blindly rando mized to receive either 100 mg hyperbaric procaine or 50 mg hyperbaric lido caine. An interview by a blinded investigator established the presence or a bsence of TNS, defined as pain in the buttocks or lower extremities beginni ng within 24 hours of surgery. Onset of sensory and motor block, patient di scomfort, supplemental anesthetics, and side effects were recorded by the u nblinded managing anesthesia team. Anesthetic adequacy was determined from these data by a single blinded investigator. Hospital discharge time was re corded from the patient record. Groups were compared using. appropriate sta tistics with a P < .05 considered significant. Results: TNS occurred in 6% of procaine patients versus 31% of lidocaine pa tients (P = .007). Sensory block with procaine and lidocaine was similar, w hile motor block was decreased with procaine (P < .05), A trend toward a hi gher rate of block inadequacy (17% v 3%, P =.11) and intraoperative nausea (17% v 3%, P = .11) occurred with procaine. Average hospital discharge time with procaine was increased by 29 minutes (P <.05). Conclusions: The incidence of TNS was substantially lower with procaine tha n with lidocaine. However, procaine resulted in a lower overall quality of anesthesia and a prolonged average discharge time. Ii the shortfalls of pro caine as studied can be overcome, it may provide a suitable alternative to lidocaine for outpatient spinal anesthesia to minimize the risk of TNS.