Changes of Plasma Concentration of Lidocaine Associated with Pediatric Caudal Anesthesia

Kim, Koang In; Choi, Kyu Taek; Cheun, Jae Kyu

Abstract

Caudal anesthesia appears to be a safe and reliable techniuqe for surgical anesthesia as well as an alternative to narcotics for postoperative analgesia for procedures below the umbilicus. The caudal anesthesia might be particularly helpful in infants and children to avoid repetitive injections of narcotics to control postoperative pain. Advantages of caudal anesthesia for pediatric surgery i.e. clearly defined anatomic landmarks, a simplicity of the technique and high success rate have been reported. However, it has not been popular in clinical practice due to several reasons. First of all, small children do not cooperate with technical procedures. Therfore, an additional measure to provide a cooperative state is needed, such as pentothal or ketamine injection, or general anesthesia induced beforehand. Secondly, there is no clear determination or unanimity in anesthetic dosage according to the patient's age or body weight. Lastly, clinical experience and reports have not been enough for clinical practice. The aim of this study was to determine whether commonly accepted dosages used in infants produce blood levels within a safe range. This study was undertaken to measure changes of plasma concentration of lidocaine in patients with pediatric caudal anesthesia, and to check pain and motor scores and analgesic level at the recovery room. The time courses of the plasma concentration were observed in 29 healthty children(0.5-13 yr) to whom were caudally injected with 1% lidocaine mixed 1: 200,000 epinephrine(10 mg/kg). The plasma concentrations were measured by immunofluoresence assay at the intervals of l5, 30, 45, and 60 minutes. The values of plasma concnetration were 1.67+/-0.41, 1.85+/-0.61, 1.73+/-0.46, 1.75+/-0.29mcg/ml(MEAN+/-SD). The peak plasma concentration was 1.85+/-0.61mcg/ml at 30 minutes. However, there no significant differences during the first hour. No data exceeded 5 mcg/ml which is plasma toxic level of lidocaine, nor children had an experience of toxic complications. When the pain and motor scores were checked in the recovery room, most children had no pain and were not ahle to stand but movalble. Sensory levels were checked up to T9 which were suitable for lower abdominal and perineal surgery. These results indicate that the injection of l% lidocaine 10 mg/kg with epinephrine in children is considered to be safe because plasma concentration dose not exceed the toxic levels.