Pharmacokinetic optimisation of general anaesthesia in pregnancy.

A significant proportion of women require general anaesthesia during pregnancy or for delivery. There are many practical difficulties in studying anaesthetic drugs and techniques to determine what may be best for both the mother and fetus. Physiological changes of pregnancy may alter the pharmacokinetics and pharmacodynamics of anaesthetics and the fetal disposition of drugs is largely unknown. With the limited pharmacokinetic data available, conclusions on the suitability of drugs are reached in conjunction with sophisticated neonatal neurobehavioural testing. The normal fetus appears able to withstand a variety of anaesthetic techniques but there is little information regarding the compromised fetus or premature neonate. Provided that adequate maternal anaesthesia is achieved, it is prudent to choose an anaesthetic technique which minimises fetal exposure to drugs and use agents which can be eliminated quickly by the neonate. Currently available drugs with rapid maternal and neonatal elimination include propofol, suxamethonium, atracurium, nitrous oxide and isoflurane.