Procaine compared with lidocaine for incidence of transient neurologic symptoms.

BACKGROUND AND OBJECTIVES: Transient neurologic symptoms (TNS) have been reported to occur after 16% to 40% of ambulatory lidocaine spinal anesthetics. Patient discomfort and the possibility of underlying lidocaine neurotoxicity have prompted a search for alternative local anesthetic agents. We compared the incidence of TNS with procaine or lidocaine spinal anesthesia in a 2:1 dose ratio. METHODS: Seventy outpatients undergoing knee arthroscopy were blindly randomized to receive either 100 mg hyperbaric procaine or 50 mg hyperbaric lidocaine. An interview by a blinded investigator established the presence or absence of TNS, defined as pain in the buttocks or lower extremities beginning within 24 hours of surgery. Onset of sensory and motor block, patient discomfort, supplemental anesthetics, and side effects were recorded by the unblinded managing anesthesia team. Anesthetic adequacy was determined from these data by a single blinded investigator. Hospital discharge time was recorded from the patient record. Groups were compared using appropriate statistics with a P < .05 considered significant. RESULTS: TNS occurred in 6% of procaine patients versus 31% of lidocaine patients (P = .007). Sensory block with procaine and lidocaine was similar, while motor block was decreased with procaine (P < .05). A trend toward a higher 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 than with lidocaine. However, procaine resulted in a lower overall quality of anesthesia and a prolonged average discharge time. If the shortfalls of procaine as studied can be overcome, it may provide a suitable alternative to lidocaine for outpatient spinal anesthesia to minimize the risk of TNS.

Does epidural anesthesia have general anesthetic effects? A prospective, randomized, double-blind, placebo-controlled trial.

BACKGROUND: Clinically, patients require surprisingly low end-tidal concentrations of volatile agents during combined epidural-general anesthesia. Neuraxial anesthesia exhibits sedative properties that may reduce requirements for general anesthesia. The authors tested whether epidural lidocaine reduces volatile anesthetic requirements as measured by the minimum alveolar concentration (MAC) of sevoflurane for noxious testing cephalad to the sensory block. METHODS: In a prospective, randomized, double-blind, placebo-controlled trial, 44 patients received 300 mg epidural lidocaine (group E), epidural saline control (group C), or epidural saline-intravenous lidocaine infusion (group I) after premedication with 0.02 mg/kg midazolam and 1 microg/kg fentanyl. Tracheal intubation followed standard induction with 4 mg/kg thiopental and succinylcholine 1 mg/kg. After 10 min or more of stable end-tidal sevoflurane, 10 s of 50 Hz, 60 mA tetanic electrical stimulation were applied to the fifth cervical dermatome. Predetermined end-tidal sevoflurane concentrations and the MAC for each group were determined by the up-and-down method and probit analysis based on patient movement. RESULTS: MAC of sevoflurane for group E, 0.52+/-0.18% (+/- 95% confidence interval [CI]), differed significantly from group C, 1.18+/-0.18% (P < 0.0005), and from group I, 1.04+/-0.18% (P < 0.001). The plasma lidocaine levels in groups E and I were comparable (2.3+/-1.0 vs. 3.0+/-1.2 microg/ml +/- SD). CONCLUSIONS: Lidocaine epidural anesthesia reduced the MAC of sevoflurane by approximately 50%. This MAC sparing is most likely caused by indirect central effects of spinal deafferentation and not to systemic effects of lidocaine or direct neural blockade. Thus, lower concentrations of volatile agents than those based on standard MAC values may be adequate during combined epidural-general anesthesia.