General anaesthesia for nonobstetric surgery during pregnancy: A narrative review

Nonobstetric surgery may be required in up to 1% of pregnancies. Most common procedures are urgent abdominal surgeries requiring general anaesthesia. Maintaining normal maternal physiology during anaesthesia is vital. Left lateral tilt position prevents aortocaval compression and preserves normal venous return. Preparation for a difficult airway is required in all obstetric patients due to the known anatomical and physiological changes. Aspiration prophylaxis and a rapid sequence induction are traditionally recommended to avoid the (probably overestimated) risk of aspiration. Although the minimum alveolar concentration (MAC) of volatile anaesthetic agents is reduced by 30 to 40%, awareness occurs more frequently in the obstetric population. Maternal outcomes from surgery are comparable with those of nonpregnant women, but increased incidences of foetal loss, preterm delivery, low birth weight and caesarean section have been reported. Although animal studies have observed impaired foetal brain development after antenatal exposure to anaesthesia, the translational value of these studies remain controversial. Clinical evidence is nearly absent. Withholding urgent/essential procedures is certainly more threatening than proceeding with the surgery. To increase the safety of mother and foetus, nonurgent or nonessential procedures should be postponed until after delivery, and if procedures cannot wait, locoregional anaesthesia should be used if possible. Where general anaesthesia cannot be avoided, the duration of exposure should be kept to a minimum. This narrative review summarises the literature of the past 20 years concerning the anaesthetic management and outcomes of nonobstetric surgery under general anaesthesia during pregnancy.