What are the indications for fetal surgery?
What are the maternal and fetal physiological considerations?
What are the surgical considerations and how can the anesthetic plan best facilitate surgical conditions?
Fetal surgery is a rapidly evolving field in which the developing fetus receives therapy with the goal of decreasing mortality and/or morbidity. It provides unique challenges and requires the integration of both obstetric and pediatric anesthesia practice. Fetal therapies range from minimally invasive techniques to open mid-gestation procedures to near-term procedures performed with the fetus partially delivered while on placental circulation. In this chapter, we describe the indications for fetal surgery, review the principles for providing anesthesia for these cases, and outline the anesthetic approach to minimally invasive, open mid-gestation, and ex utero intrapartum treatment (EXIT) procedures.
A BRIEF HISTORY OF FETAL SURGERY
The first successful fetal therapy in humans began in the 1960s when hydrops fetalis caused by Rh sensitization was treated with in utero transfusion. However, successful exposure of the fetus would have to wait until the 1980s when better prenatal imaging techniques such as sonography and MRI, surgical techniques, and safer anesthetic agents were available. Select milestones in fetal surgery include the first congenital cystic adenomatous malformation (CCAM) resection in 1984, congenital diaphragmatic hernia (CDH) repair in 1989, aortic valvuloplasty in 1991, sacrococcygeal tumor (SCT) resection in 1992, laser ablation of placental vessels in 1995, EXIT procedure in 1995, fetoscopic surgery in 1996, myelomeningocele (MMC) open repair in 1997, hypoplastic left heart balloon septoplasty and valve dilation in 2004, and hypoplastic left heart laser atrial septotomy in 2005.1 Many of these therapies have since become standard of care and the field of fetal surgery continues to evolve rapidly.
INDICATIONS FOR FETAL SURGERY
While many fetal anomalies can be detected prenatally with sonography and MRI, only select cases have compelling physiological rational for intrauterine therapy. Untreated, the risk of death or severe disability to the fetus must be high. The risk of surgery to the mother should be relatively low. In twin-twin transfusion syndrome, blood passes unequally between twins that share a placenta. The smaller donor twin pumps blood to the larger recipient twin. Twin reversed arterial perfusion (TRAP) sequence is a severe form of twin-twin transfusion syndrome in which one twin is developmentally normal and the other has a serious condition such as a missing heart or missing head that prevents it from surviving on its own. The goal of therapy in twin syndromes is to interrupt the blood flow between the twins. This can be accomplished under visualization with a fetoscope and laser coagulation of the shared vessels. In the case of TRAP syndrome, radiofrequency ablation or ligation of the cord of the abnormal twin can be used to stop the blood flow to the abnormal twin (Figure 26-1). These surgeries are usually ...