[Caudal anesthesia in pediatric surgery. Pharmacokinetic study and clinical significance]

In 1987, 758 caudal anaesthesia allowed the execution of 41% of all our department's operations. Urological, genital, inguinal and lower limbs surgery were the most frequent. The injection into the extradural space through the hiatus sacralis always included the mixture of lidocaine with bupivacaine to speed up the beginning of the operation. The patients were split up into 2 equal groups and were given 1.25 ou 2.50 mg.kg-1 of bupivacaine (i.e. 0.50 ml.kg-1 of a 2.50 or 0.50% solution). Bupivacaine plasma levels were determined by high performance liquid chromatography in 40 patients from the first group and in 42 patients from the second. They reached their maximum about 500 or 1,000 ng.ml-1 respectively, 30 mn after the injection and always fell back 4 hours after the administration. These concentrations were compared with the levels obtained by infusion to the dog, which cause serious cardiac disorders with 6,000 to 8,000 ng.ml-1 levels, and elicit ventricular fibrillation with 8,000 to 10,000 ng.ml-1. So the safety margin appears greater when overdose and/or intravascular injection are avoided. Caudal anaesthesia is easy, fast acting and allows to relieve post-operative pain. It is suitable for all surgery below the umbilicus and can be used on an outpatient basis.