CONJOINED TWINS SEPARATION SURGERY

Conjoined Twins Separation Surgery

Conjoined Twins Separation Surgery

Introduction

There are two congenital anomalies specific to multifetal pregnancies: twin reversed-arterial-perfusion sequence and conjoined twinning. The twin reversed-arterial-perfusion sequence is a rare complication of monozygous twinning in which one fetus (the "pump" twin) perfuses the other fetus (the "perfused" twin), resulting in reversed flow in the umbilical vessels and multiple structural anomalies, including acardia, in the perfused twin. It occurs in fewer than 1 percent of pregnancies with monozygous twins and in about 1 in 35,000 births overall. Conjoined twinning occurs as a result of incomplete duplication of a single blastocyst during the process of monozygotic twinning.4 It is a sporadic complication that occurs at rates ranging from 1 in 30,000 to 1 in 100,000 births (Weinreb JC, Brown CE, Lowe TW, Cohen JM, Erdman WA, 1986).

Surgical separation of conjoined twins is commonly undertaken after birth, but surgery is usually delayed for weeks or months. With time, the infants become larger, the anatomical relations between them can be better delineated, other congenital anomalies may be identified, the risk associated with anesthesia usually decreases, and the separation procedure can be carefully planned. In contrast, a twin reversed-arterial-perfusion sequence may be treated by sacrificing the acardiac twin in utero. We report here a unique case of conjoined twins with reversed-arterial-perfusion sequence. Because the twins were joined, antenatal surgical intervention to treat the twin reversed-arterial-perfusion sequence was not possible, so immediate surgical separation at birth was necessary. Given this situation, we used three-dimensional computer modeling with prenatal magnetic resonance imaging (MRI) to assist planning for the surgical separation of the twins at birth. This approach made it possible for the pump twin to survive ().

Literature Review

It is a multidisciplinary team approach involving extensive medical work-up on patients, multiple meetings and discussions with all the involved specialties and supporting staff, involvement of parents, Psychosocial counseling olparents, rehearsal ofthe planned surgical procedure, media contact prior to Surgery. The rationale for deferring surgery should include single heart, major communicating hearts or major anomalies. Goals of the anaesthesia care are to pay meticulous attention to detail, monitoring, and vigilance, planning for the poserative care in the intensive care unit (ICU), by a dedicated team of anaesthesiologists and intensivists for each child with duplication of all monitoring and equipment in one operating room (Szmuk P. Rabb MF, Curry B, 2006).

Pharmacokinetics and pharmacodynamics are inconsistent in various types of twins. Usually there is more cross-circulation in the thoracopagus and craniopagus twins than in other types, and therefore one can expect altered and unpredictable drug responses. Estimation ofcirculatory mixing is useful to help calculate drug dosage and fluid replacement during surgery. Drugs administered to one twin may have unexpected effects on the other, especially for i.v. administration when circulatory admixing is present. Recommended i.v. doses ofanaesthetic agents for the combined body weight ofthe twins are usually halved and then divided into two equal doses to be administered to each twin. Reduced incremental doses are titrated against response and ...