Blood concentrations of lidocaine, mepivacaine and bupivacaine during caudal analgesia in children.

The venous blood concentrations of lidocaine, mepivacaine and bupivacaine were measured in children following the caudal epidural administration of these local anaesthetic solutions with adrenaline. The mean maximum concentrations of lidocaine and mepivacaine were 2.20 micrograms/ml and 2.53 micrograms/ml, respectively, which occurred at 45 min after injection of lidocaine or mepivacaine 11 mg/kg. By combined administration of 5.5 mg/kg equally of lidocaine and mepivacaine, the blood concentration of mepivacaine was significantly higher than that of lidocaine. The mean maximum concentration of bupivacaine was 0.67 micrograms/ml and occurred at 45 min after injection of bupivacaine 3.7 mg/kg. The blood concentration of bupivacaine was consistently significantly lower than that of lidocaine or mepivacaine. These results demonstrate that the blood concentrations of the three local anaesthetics following caudal administration are all below the toxic levels in spite of application of the maximum dosage recommended for adults.