[Conduction anesthesia and the newborn infant].

The placental transfer of local anaesthetics (LA) depends on maternal, placental and fetal factors. The assessment of effects of LA and epidural anaesthesia (EA) on the fetus is based on the monitoring of fetal heart rate (FHR) and the measurement of the fetal pH. Apgar score and neurobehavioral tests allow an evaluation of the neonatal effects of the drugs used. Direct effects of LA: a diminution of variability of FHR was observed shortly after the beginning of an EA using lidocaine but there was no modification of FHR after EA using bupivacaine or lidocaine with epinephrine. Fetal neurological toxicity is rare and there are very few alterations of neurobehavioral scores after EA. Indirect effects on uteroplacental blood flow (UBF): in high concentration, LA can induce vasoconstriction of uterine arteries but maternal arterial hypotension that impedes directly uteroplacental blood flow is the main effect. Prevention of aortocaval compression is essential because it allows better Apgar scores and arterial pH at birth. Use of colloids has not a better preventive efficacy than an equal volume of cristalloids while dextrans are formally contra-indicated because of serious fetal accidents. Large iv infusion of dextrose solutions are responsible for maternal and fetal hyperglycemia and hyperinsulinemia leading to neonatal hypoglycemia. The utilization of IM prophylactic ephedrine is not useful while the therapeutic administration of ephedrine to treat maternal arterial hypotension is efficient. Phenylephrine used in case of maternal arterial hypotension seems as efficient as is ephedrine. Epidural narcotics: the use of morphine by epidural route can induce neonatal respiratory depression and low neurobehavioral scores. The epidural administration of fentanyl does not alter the variability of the FHR and does not modify neither Apgar or neurobehavioral scores, nor respiratory adaptation of the newborn. Use of epidural alfentanil or sufentanil does not lead to low neurobehavioral scores unless very high doses are used. For elective caesarean section, newborns present a lower Apgar score at 1 min and necessitate respiratory assistance more frequently after general anaesthesia (GA) than after EA. Neurobehavioral scores are better after EA than after GA. For emergency caesarean section, the percentage of newborns with an Apgar score < 4 or necessitating a respiratory assistance is more important after GA than after EA. However, the perinatal mortality is not more important after GA than after EA.