Fetal surgery is an attractive option in cases where an isolated abnormality would be otherwise fatal to the fetus or neonate, and is clearly amenable to correction, such as neck tumours with airway obstruction, sacrococcygeal teratomas, obstructive uropathy and diaphragmatic hernia. However, results of intrauterine surgery are variable depending on the type of surgery, and there is no clear consensus on its place. There are three main types of intrauterine surgery:
• Ex-utero intrapartum treatment (EXIT). This occurs immediately before delivery, and the fetus remains attached to the placenta, allowing brief procedures such as tracheal intubation or tracheostomy for airway obstruction to occur. Corrective surgery may then occur post-delivery.
• Open procedures such as correction of a meningomyelocoele. A vertical uterine incision may be required for access, necessitating caesarean delivery if the pregnancy proceeds.
• Minimally invasive procedures such as intrauterine blood transfusion in haemolytic disease or laser ablation of communicating vessels in twin-to-twin transfusion syndrome.
Problems and special considerations
Each procedure must be assessed on a risk-benefit basis, since there is a risk of up to 50% fetal loss associated with premature labour, haemorrhage, abruption and infection. Surgery is technically difficult because of the small size of the fetus and its mobility when small, but leaving the surgery until later may result in increased end-organ damage caused by the malformation. The optimal timing for most procedures is uncertain, although most open ones have been performed at around 18-24 weeks. Percutaneous procedures (e.g. transfusions) may be performed later or at intervals.
Maternal risks include haemorrhage, uterine scarring and amniotic fluid embolism. Postoperatively, the mother may be confined to bed and receive p2-agonists, with the risks of deep-vein thrombosis and pulmonary oedema, respectively.
Each lesion must be carefully defined and a chromosomal abnormality or other malformation excluded. For example, intrauterine placement of intraventricular shunts is no longer considered suitable for treatment of hydrocephalus, since the risk-benefit ratio cannot be calculated for individual fetuses because of the difficulty in predicting outcome antenatally. Since most conditions that might be amenable to intrauterine surgery are rare or uncommon and already associated with poor outcome, it is difficult to demonstrate that outcome after fetal surgery is better than that after conventional postpartum therapy, because any expected improvement will be small.
Management options
Anaesthetic management is along the lines of that for incidental surgery during pregnancy, with maintenance of uteroplacental perfusion the main concern (see Chapter 8, Incidental surgery in the pregnant patient). Local anaesthetic infiltration of the abdominal wall, with or without conscious sedation, may be adequate for percutaneous procedures, although there may be a need for emergency caesarean section if fetal bradycardia occurs, and so adequate preparation and facilities are required for this. Regional anaesthesia is a suitable alternative if extensive percutaneous procedures are required.
Fetal and maternal general anaesthesia for corrective surgery is administered by using standard techniques, though placental transfer of anaesthetic agents may be desirable in this scenario, unlike during caesarean section. Total uterine relaxation may be required, and this may be achieved with 2-3 MAC of an inhalational agent; this may result in maternal haemorrhage or hypotension, both of which must be anticipated and treated aggressively. Alternatively, magnesium sulfate or glyceryl trinitrate may be used. Fetal injection of a neuromuscular blocking drug may be required to stop fetal movement. Analgesics may also be injected into the fetus, since there is increasing evidence that the fetus can experience pain. Fetal monitoring may be difficult, but pulse oximetry, ultrasonography and cardiotocography have been used. Bleeding may be excessive in prolonged open procedures.
Key points
• The place of intrauterine surgery is uncertain.
• To be suitable for intrauterine surgery, malformations must be clearly defined, fatal if untreated and amenable to corrective surgery.
• General principles of anaesthesia are as for incidental surgery during pregnancy.
Further reading
De Buck F, Deprest J, Van de Velde M. Anesthesia for fetal surgery. Curr Opin Anaesthesiol 2008; 21: 293-7.
Garcia PJ, Olutoye OO, Ivey RT, Olutoye OA. Case scenario: anesthesia for maternal-fetal surgery: the ex utero intrapartum therapy (EXIT) procedure. Anesthesiology 2011; 114: 1446-52.
Tran KM. Anesthesia for fetal surgery. Semin Fetal Neonatal Med 2010; 15: 40-5.