The Teratogenic Risk

Preoperative Assessment of the Pregnant Patient Undergoing Nonobstetric Surgery

The anesthetic management of pregnant patients can present a variety of challenges and a thorough preoperative assessment is necessary before initiating any anesthetic services. Both the mother and the fetus need to be considered when formulating an anesthetic plan and discussing informed consent. The overall aims in assessing a pregnant patient are to identity potential issues that can lead to catastrophic complications, provide adequate information allowing the mother to make informed decisions, and to obtain knowledge for tailoring an anesthetic that maintains maternal and fetal homeostasis.

Anaesthesia for non-obstetric surgery during pregnancy

Non-obstetric surgery during pregnancy posts additional concerns to anaesthesiologists. The chief goals are to preserve maternal safety, maintain the pregnant state and achieve the best possible foetal outcome. The choice of anaesthetic technique and the selection of appropriate anaesthetic drugs should be guided by indication for surgery, nature, and site of the surgical procedure. Anaesthesiologist must consider the effects of the disease process itself and inhibit uterine contractions and avoid preterm labour and delivery. Foetal safety requires avoidance of potentially dangerous drugs and assurance of continuation of adequate uteroplacental perfusion. Until date, no anaesthetic drug has been shown to be clearly dangerous to the human foetus. The decision on proceeding with surgery should be made by multidisciplinary team involving anaesthesiologists, obstetricians, surgeons and perinatologists. This review describes the general anaesthetic principles, concerns regarding anaesthetic drugs and outlines some specific conditions of non-obstetric surgeries.

Anaesthetic considerations for non-obstetric surgery during pregnancy

Surgery during pregnancy is complicated by the need to balance the requirements of two patients. Under usual circumstances, surgery is only conducted during pregnancy when it is absolutely necessary for the wellbeing of the mother, fetus, or both. Even so, the outcome is generally favourable for both the mother and the fetus. All general anaesthetic drugs cross the placenta and there is no optimal general anaesthetic technique. Neither is there convincing evidence that any particular anaesthetic drug is toxic in humans. There is weak evidence that nitrous oxide should be avoided in early pregnancy due to a potential association with pregnancy loss with high exposure. There is evidence in animal models that many general anaesthetic techniques cause inappropriate neuronal apoptosis and behavioural deficits in later life. It is not known whether these considerations affect the human fetus but studies are underway. Given the general considerations of avoiding fetal exposure to unnecessary medication and potential protection of the maternal airway, regional anaesthesia is usually preferred in pregnancy when it is practical for the medical and surgical condition. When surgery is indicated during pregnancy maintenance of maternal oxygenation, perfusion and homeostasis with the least extensive anaesthetic that is practical will assure the best outcome for the fetus.

Teratogenic effects of methylnitrosourea on pregnant mice before implantation

Methylnitrosourea at a dose of 10 mg/kg is teratogenic when applied to pregnant mice on gestational days 2.5, 3.5 or 4.5, but has no such effects on gestational days 0.5 and 1.5.