Dosage and Plasma Concentration of Local Anesthetics in Epidural Anesthesia for Cesarean Section

Song, Jeong Ja; Han, Young Jin; Lee, Jun Rae; Song, He Sun

Abstract

Epidural anesthesia for cesarean section requires sensory blockade up to T4 level. 18 to 20 ml of 0.5% bupivacaine, 1.5 to 2.0% lidocaine, or 3.0% chloropmcaine usually produces an adequate sensory blockade to T4 level. However, when we used that amount of local anesthetics, most of the patients often complained of mild to moderate pain or discomfort during delivery of baby, manipulation of peritoneum or the uterus. So we feeled the need of increase in dosage of local anesthetics and we used 26 ml of local anesthetics or local anesthetic-fentanyl mixture. This study was undertaken to measure plasma concentration of lidocaine and observe the possible systemic toxicity of local anesthetics with the total dosage of beyond maximum recom-mended dose. Epidural anesthesia were performed with a 17 gauge Tuohy needle and local anesthetics were injected as follows. Group 1 (n;17): 0.5% bupivacaine 100 mg+2% lidocaine 80 mg+fentanyl 100 ug (50 ug/ml) Group 2 (n; 15): 2% lidocaine 520 mg without epinephrine Group 3 (n; ll): 2% lidocaine 480 mg + fentanyl 100 ug All groups were received 26 ml of local anesthetics or local anesthetic-fentanyl mixture. We checked the level of anesthesia, length of spinal column, cardiovascular changes, plasma concen- tration of lidocaine, toxic systemic reactions and patient's complaints. The plasma concentration of lidocaine were measured by immunofluorescence assay at 2, 5, 7, 10, 12 and 15 minutes after injection of local anesthetics. The results were as follows; 1) The peak plasma concentration of lidocaine were measured 12 minutes after administration of local anesthetics in the group 2 and 3. 2) Sensory blockade up to T4 level could be accomplished within 10 minutes after epidural anesthesia in the group l. 3) In the group 2 and 3, onset of action was more rapid. These groups had a tendency to fall in blood pressure than the group 1, but recovered soon with small dose of ephedrine. 4) In one patient, maximum peak plasma concentration of hdocaine was 6.8 ug/ml, but no adversereaction was observed. Above results suggested that 26 ml of local anesthetics in all groups could be used for appropriate anesthesia for cesarean section with minimal camplications and patient's satisfaction.