[Maternal and fetal levels of local anaesthetics after epidural injection of a triple mixture].

Twenty-four parturients received an epidural injection of a 5.10(-6) adrenaline mixture containing: lidocaine 295 +/- 19 mg, bupivacaine 58 +/- 4 mg and etidocaine 58 +/- 4 mg. The mean serum levels measured in the mother (peripheral vein) and in the fetus (umbilical vein) and in the fetus (umbilical vein) and the fetus/mother ratios were, respectively:--1.05 +/- 0.47 micrograms . ml-1, 0.68 +/- 0.34 micrograms . ml-1 and 0.66 +/- 0.15 for lidocaine; --0.25 +/- 0.10 micrograms . ml-1, 0.14 +/- 0.06 micrograms . ml- and 0.51 +/- 0.16 for bupivacaine; ---0.27 +/- 0.10 micrograms . ml-1, 0.17 +/- 0.10 micrograms . ml-1 and 0.63 +/- 0.23 for etidocaine. From the sum of these concentrations the maternal and fetal serum levels and the fetus/mother ratio could be calculated in lidocaine equivalents. The values obtained were: 3.14 +/- 0.74 . ml-1, 1.90 +/- 0.68 micrograms . ml-1 and 0.60 +/- 0.13 respectively. A comparison of these data with those found in the literature led to the following conclusions: (1) The maternal serum levels of each anaesthetic drug in the mixture are the same as if it had been injected separately; (2) owing to tissue competition, the transplacental passage is increased by majoration of the free form, this being more pronounced with bupivacaine and etidocaine; (3) the circulating drug concentrations evaluated as lidocaine equivalent in the mother and fetus are comparable to those determined at the end of conventional local anaesthetic procedures.