[Pharmacokinetic study on the lidocaine concentration in serum during epidural anesthesia].
This study was performed on humans to find a safety format for clinical application of lidocaine, a most popular local anesthetic in Japan, by following serum concentration of the drug epidural anesthesia, with or without repeated supplemental addition of the anesthetic. Twenty-five patients (ASA 1-2) were used for observations of short duration and 7 patients (ASA 1-3) for long duration. Changes in serum drug concentration after single epidural or intravenous injection were analyzed pharmacokinetically in 7 and 15 patients with or without hepatic disfunction, respectively. The serum lidocaine concentration was determined by an EMIT assay. It was found that during epidural anesthesia of 3 h duration with 1.5% lidocaine E (priming dose 15-20 ml, supplemental doses one or two thirds of the priming dose) an interval of about 50 min was preferable for the first supplementation, followed by longer intervals: serum drug concentration did not exceed 5 micrograms/ml over which is dangerous clinically. During epidural anesthesia of longer duration (maximum 11 h), the peak concentrations remained below 5 micrograms/ml which was seen after the 9th supplementation. There was a trend of increase in serum drug concentration by each supplementation. Actual mean values were lower than those estimated pharmacokinetically. This was due partly to dilution effect induced by bleeding and transfusions that followed. Addition of epinephrine to lidocaine (lidocaine E) reduced reabsorption of supplemented lidocaine by 20%, thereby increased the local concentration of the drug, resulting in an elongation of interval for supplementation. The combination was beneficial to patients also by preventing a sharp rise of drug level even after repeated supplementation. No difference was observed in the absorption, degradation and excretion of the drug between patients with and without hepatic dysfunctions examined.
D000368:Aged; D000767:Anesthesia, Epidural; D005260:Female; D006801:Humans; D007700:Kinetics; D008012:Lidocaine / Q000097:blood; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D013997:Time Factors
D008012:Lidocaine