Incidence

Because of the significant number of conjoined twins who are aborted or who are stillborn, the exact incidence is not known, but the reported incidence worldwide is estimated at 1:50,000 to 1:100,000 live births, with a higher incidence of 1:14,000 to 1:25,000 experienced in Africa and Asia (Hoyle, 1990). Of those that are born, many may have congenital abnormalities that are incompatible with life. The presence of associated congenital anomalies in live twins is common. Congenital diaphragmatic hernia, pulmonary hypoplasia, congenital heart disease, anomalous hepatic arterial and venous drainage, biliary tree anomalies, bowel atresia, Meckel’s diverticulum, complex urogenital anatomy, and spinal dysraphism have all been reported.

Historical perspectives

Conjoined twins are one of nature’s greatest enigmas. Cave drawings, pottery, figurines, and folklore indicate that conjoined twins have occurred since prehistoric times. Embryonic duplication also occurs in plant and other animal forms of life (Fig. 29-1) (Thomas and Lopez, 2004). The famous and most celebrated pair of conjoined twins, Chang and Eng Bunker, who were joined at their xiphisterna, was born in Siam (now Thailand) in 1811. Because of their fame and the rarity of this pathology, the term Siamese twins has become synonymous with conjoined twins. Over time, the bridge of skin and tissue between them stretched, and they were able to stand side by side. The twins were taken to America, where they were on display by Phineas T. Barnum in his circus. Surgery for separation was deemed too risky unless one of the twins was to die. The Bunker twins lived very interesting lives—they married sisters and fathered 22 children between them. They died within hours of each other at the age of 63 (Spitz, 2003). Interestingly, the twins who have become most famous have all remained conjoined, whereas there is very little literature on the lives of those who have been separated. Votteler and Lipsky (2005) have reported on the long-term results of ten separations, as have Hoyle and Thomas (1989) with their experiences studying ischiopagus twins over 23 years. The first set of omphalopagus twins separated at the Red Cross Children’s Hospital now each has children of their own (Cywes and Louw, 1967; Cywes et al., 1982).

FIGURE 29-1 Conjoined twinning occurs in plants and animals, as well as in human life. This photograph is of twin roses of the Double Delight variety.

The first successful separation of conjoined twins was performed by Konig in 1689, when he separated omphalopagus twins by slowly tightening an encircling band around the connection until it necrosed the connecting bridge. The first successful separation of thoracopagus twins with a conjoined heart was reported in 1979 when, after the interatrial bridge was interrupted, there was a single survivor (Synhorst et al., 1979).

During the 1960s and 1970s, emphasis in the perioperative management of conjoined twins was on preoperative discussions and planning, dress rehearsals, and on the then-new techniques of invasive intraoperative monitoring for blood loss and hemodynamic status (Diaz and Furman, 1987). From the 1980s onward, most improvements have occurred in obstetric and fetal ultrasound; fetal and neonatal surgery; magnetic resonance imaging (MRI); contrast computed tomography (CT); numerous radiographic technological options to help delineate anatomic variations in different twins; in the anesthetic advances of oximetry, capnography, agent analysis; and in techniques for monitoring brain oxygenation and blood flow.

For the induction of omphalopagus twins, Allen et al. (1959) described the use of cyclopropane and oxygen, supplemented by ether via the open-drop method. He describes the attempts at intubation by holding one infant above the other to facilitate easier intubation as a “near fatal mistake.” In this position, the upper twin became pale and apneic, whereas the condition of the lower infant rapidly deteriorated and it became plethoric. Once they were returned to their normal position, they were successfully intubated. He comments that “there are few vital signs available for monitoring infants of this size. The most important signs are respirations, color, and muscle tone.” Both infants survived the surgical separation.

The anesthesia provided to separate the first set of twins in 1967 in Cape Town, South Africa, was described as “uneventful” (Cywes and Louw, 1967). Preoperative investigations in these omphalopagus twins indicated that there was no cross-circulation between the infants and this was confirmed at the induction of anesthesia, when the pancuronium given to one infant had no effect on the other.

In Furman’s report (Furman et al., 1971), intubation on a set of xiphopagus twins was performed when both infants were awake, and vascular cannulation was done when they were under local anesthetic. Jarem (Jarem et al., 1977), in his classic paper, describes the double breathing circuit fashioned from readily available parts of anesthetic equipment.

Roy (1980) described his experience with craniopagus twins. His group used two anesthetic teams, but only one anesthetic machine with a non–rebreathing Jackson-Rees breathing system from the gas outlet leading to two T pieces. Monitoring included: electrocardiograph (ECG), Doppler arm-cuff pressures, esophageal stethoscopes, and rectal telethermometers. Each infant received preoperative atropine, and they were induced simultaneously with halothane, nitrous oxide, and oxygen. He continued to describe the 15-month preparation time before their separation. This was successfully achieved, but he describes the anesthetic challenges as severe hemorrhage and maintenance of a clear airway with obstruction from secretions, kinking, or accidental extubation. Harrison and his team (1985) commented on the need for modification of the breathing circuit to accommodate the process of ventilating neonatal conjoined twins simultaneously and stated that adequate intravascular fluid replacement was essential to prevent hypotension at separation. They also commented on the intraoperative challenges of these infants.

Diaz and Furman, (1987), in their well-known paper on the perioperative management of conjoined twins, highlighted many factors that are now integral to the care of these patients. Advances in anesthetic equipment, monitoring, and drugs (inhalational or intravenous) give us options for anesthesia that earlier anesthetic specialists did not have. Similarly, outcomes for surgical procedures in these patients have improved. The developments in pediatric intensive care have had a positive impact on both the preoperative and postoperative care and outcomes of these children.

Embryology

Two theories have been proposed as to the etiology of conjoined twins: fusion and fission. Although the differences between these theories have yet to be resolved, fission is the generally accepted and older theory, where the fertilized egg fails to split completely (Kaufman, 2004). The theory of fusion, proposed by Spencer (2000a, 2000b, 2003), suggests that the fertilized egg splits completely, but a secondary union of two separate embryonic discs at the dorsal neural tube or ventral yolk sac takes place at 3 to 4 weeks’ gestation. This theory was also held by Aristotle (Millar et al., 2009).

Monozygotic twins are the result of one ovum being fertilized by one sperm and then dividing into two embryos. In conjoined twins, this division, at the 13th to 17th day of the blastocyst stage, is incomplete.

Conjoined twins are identical, with what has always been thought to be an identical chromosomal pattern. With new molecular genetics, this has been shown to not necessarily be the case, and the twins may neither be completely identical nor have the same chromosome pattern (Hall, 2003). It has been hypothesized that monozygotic twinning occurs at four possible phases: up to 3 days’ postconception, after 4 to 6 days, after 7 to 12 days, and finally after 13 to 17 days. It is during this latter period that conjoined twins, fetus-in-fetu, or a teratoma may arise (Hall and Lopez-Rangel, 1996). Parasitic twins are thought to result from the embryonic death of one twin, with the remaining parts of the body vascularized by the surviving autocyte. Fetus-in-fetu are asymmetric monozygotic diamniotic intraparasitic twins (Hall and Lopez-Rangel, 1996). Conjoined triplets and quadruplets have been documented, although all have been aborted (O’Neill, 1998; Rode et al., 2006). These cases are exceptionally rare, with an even more obscure pathogenesis.

Conjoined twins are always the same gender. There is a 3:1 female-to-male incidence in live births, but more males are stillborn (Hoyle, 1990; Rejjal et al., 1992). They are monozygotic, monoamniotic, and monochorionic. Despite this, the infants usually vary in size, appearance, personality, internal anatomy, and degree of organ-sharing and duplication. Many of the challenges for all disciplines relate to the vast diversity in the anatomic variations that may possibly occur. Organs may be conjoined, duplicated, or absent. Investigations are crucial to clarifying these differences in order to make decisions about surgery, interventions, and survival. Even then, surprises occur at the time of surgery, and innovative techniques may be necessary.

Survival depends on the site and complexity of conjunction, the degree of organ sharing, and the presence of other congenital anomalies, with the extent of cardiac fusion and lung development being major determining factors (Andrews et al., 2006).

Classification, nomenclature, and terminology

Conjoined twins are typically classified by the anatomic site of conjunction (which may be complex) followed by the suffix -pagus—the Greek word meaning that which is joined (Box 29-1). There is an international collaboration attempting to create a more uniform classification of conjoined twins (Spencer, 1996). This considers a ventral (front, caudal, or lateral) or dorsal (back-to-back, sacrum-to-sacrum, or head-to-head) fusion, with further classification described in the following paragraphs (Fig. 29-2).

FIGURE 29-2 Illustrations depicting the anatomic relationships of the different types of symmetric conjoined twins.

(Modified from Spencer R: Conjoined twins: developmental malformation and clinical implications, Baltimore, 2003, John Hopkins University Press.)

Twins are described as being symmetric or asymmetric, although these terms are often misleading, because even when the twins are fully formed they are seldom truly symmetric. According to the most prominent site of conjunction, the following sites of conjunction are the most common: the chest (thoracopagus twins), the abdomen (omphalopagus twins), sacrum (pygopagus twins), pelvis (ischiopagus twins), and back (rachipagus twins) (Table 29-2).

TABLE 29-2 Types of Symmetric Conjoined Twins

GI, Gastrointestinal.

Symmetric twins are two anatomically identifiable infants with a physical appearance suggestive of two possible survivors. With asymmetric, or parasitic, twins, one twin is a potential survivor and usually appears normal, but the other is incomplete and attached as a parasite. This may be externally visible, or it may be internal. Where there is an attachment of an anatomically identifiable part, but not of a total individual, the term heteropagus is used. It is in this group, that regional anesthesia is particularly useful. Within a classified group, especially with complex conjunctions, the external physical appearance and spatial arrangement of the infants may be very different (Figs. 29-3 and 29-4).

FIGURE 29-3 These ischiopagus twin girls were born via vaginal delivery to a very surprised mother and her midwife.

FIGURE 29-4 This set of twin boys has a complex conjunction at the thoracic, abdominal and pelvic levels, and despite also being ischiopagus, show no physical resemblance to the twins in Figure 29-3.

Conjoined twins are further classified by the number of limbs present and the internal organs that are involved in the conjunction. The following list shows this classification system:

The degree of cardiac fusion, or degree of cardiopagus, can be considered as follows (Andrews et al., 2006):

A: Separate hearts and pericardium

B: Separate hearts and a common/shared pericardium

C: Fused atria and separate ventricles

D: Fused atria and ventricles

Outcomes for separation in groups C and D are poor.

Ethics

In broad terms, ethics are a set of standards of professional conduct (Atkinson, 2004). Whenever planned separation of conjoined twins takes place, and when there is a possibility or probability that one twin may not survive the procedure, moral, ethical, and legal arguments are raised. Many of these issues have been addressed in the literature (Pearn, 2001; Unknown author, 2000; Spitz and Kiely, 2000; Spitz, 2000; Bratton and Chetwynd, 2004). The Hastings report identified three cardinal issues (London and Knowles, 2001):

In his review of this subject, Atkinson (2004) commented that the birth of a handicapped child is an immense burden to any parents. If they are to avoid greater challenges, the clinicians require sensitivity and patience as they steer the family along a pathway to survival. The question most often asked is whether it is justified to sacrifice one life to save another, or should both infants be allowed to die? Answers are seldom simple, and each case should be assessed on its own merits. Decisions depend on the type and complexity of the conjunction, the overall health of both infants, the laws of the country, and the religion and beliefs of the parents. If the sacrifice of one twin is necessary for the other twin to survive, it is important to recognize that both would die without separation. If they were separated, at least one would live (O’Neill et al., 1988).

Especially in centers where these operations are done more often, medical staff is more confident of their ability to provide insightful management decisions pertaining to these care of conjoined twins. They are supported by investigations that provide valuable information, allowing rational decisions to be made about the immediate and long-term futures of these infants. These investigations, performed to clarify anatomic structures include radiologic imaging, ultrasonography, CT, MRI, radioisotope studies, echocardiography, cardiac catheterization, and neuroradiologic imaging. As a consequence, in the perioperative period the pediatric surgeons and anesthesiologists in these centers have reported much higher rates of success in operating on these infants. Developments in intensive care also have a positive impact on these improved outcomes.

Ian Aird (1954, 1959) wrote that if there was a possibility of at least one twin surviving, surgery should be performed. The operation does not decide which twin will survive; this is determined by their relative conditions (O’Neill et al., 1988).

Great Ormond Street Ethical Guidelines for Conjoined Twin Separation has been adopted by a number of units. Where separation is feasible with a reasonable chance of success, it should be carried out. When surgery is not possible, custodial care should be offered, and nature should be allowed to take its course. When one twin is dead or has a lethal abnormality and cannot survive independently from its normal twin, and if there is no surgery both twins would die, separation to save the healthy twin should be attempted (Rode et al., 2006; Millar et al., 2009).

Perinatal considerations

Improved techniques of antenatal diagnosis and fetal imaging have allowed the diagnosis of conjoined twins to be made during pregnancy, so that counseling of the parents may allow them the option to have the pregnancy terminated. Conjoined twins can be identified as early as 11 weeks’ gestation, and in this series of cases studied by Sebire et al. (2000), all the parents opted for termination. Complex craniopagus and cardiopagus anatomy in particular may tilt the decision in this direction. Conjoined hearts are easier to study via ultrasound in utero, because the amniotic fluid acts as a buffer, whereas after birth the lungs inflate with air and prevent optimal visibility (Kingston et al., 2001).

Obstructed labor with difficult vaginal delivery may necessitate an emergency cesarean section, but this can be avoided by antenatal diagnosis and elective cesarean section at 36 to 38 weeks’ gestation (Millar et al., 2009). In many developing countries, the birth of conjoined twins may come as a surprise to the mother and the attending midwife or medical practitioner (Thomas, 2004; Thomas and Lopez, 2004).

Perinatal management of conjoined twins involves a close collaboration between anesthesiologists, obstetricians, and pediatricians so that birth trauma for both the mother and the infants can be minimized. Unborn conjoined twins may be referred to pediatric surgeons for advice in order to plan the delivery and the immediate perinatal management.

Careful prenatal investigations may identify cases in which emergency separation at birth is life saving (MacKenzie et al., 2002). Advances in prenatal ultrasound, as well as the use of color-flow Doppler and prenatal MRI, have improved the antenatal diagnosis of conjoined twins. In particular, prenatal and postnatal echocardiography has been shown to accurately delineate the extent of cardiac fusion, the intracardiac anatomy, and the ventricular function (Andrews et al., 2006). Planning of the antenatal course and the perinatal management of twins can be facilitated by identifying those twins at particular risk, such as twins with twin reversed–arterial perfusion sequence. In this situation, vascular communications between the two fetuses allows deoxygenated blood from one fetus (the pump twin) to perfuse the other fetus (the perfused twin), resulting in reversed flow in the umbilical vessels and the development of multiple anomalies, including acardia, in the perfused twin (Norwitz et al., 2000). Antenatal surgical intervention, removing the acardiac twin in utero, may allow for the survival of the remaining (pump) twin. If they are conjoined, however, this is not possible, and immediate surgical intervention at birth is necessary. In order to make rational and sound decisions as to the anesthetic management, anesthesia for fetoscopic fetal surgery requires knowledge of the pathophysiology of the fetus, the fetoplacental unit, and the condition of the mother (Galankin et al., 2000).

Plans may be necessary, in those units providing that option, for an ex utero intrapartum treatment (EXIT) procedure (Bouchard et al., 2002). In this operation, access to the fetus is achieved when the fetus is brought into the surgical field while it is still attached to the mother’s placenta. The planned procedure, whether for access to the fetal airway in the case of an airway tumor, or to allow separation of a conjoined twin from its non–survivable twin, is then carried out. Once it has been completed, the infant is then delivered from the mother and separated from its placenta. This procedure has also been used for airway control of both twins when the antenatal airway and cardiopulmonary status of the twins was not known (Ossowski and Suskind, 2005).

At delivery, it is optimal to have two sets of all neonatal resuscitation equipment available and a pediatrician (or anesthesiologist) present for each infant. A conventional open incubator usually provides a large enough surface area to accommodate both infants. If one twin is doing poorly, it should be attended to first. Especially with thoracopagus twins, over-vigorous ventilation of one may compromise the other because of the chest contents moving across into the chest cavity of the other. If intubation is necessary, this should be performed on one infant at a time, with the other twin being supported, if necessary, with bag face-mask oxygen and ventilation. A T piece and small mask is easier to use than an Ambu bag. While laryngoscopy is being performed on one twin, care must be taken to protect the infant who is not being intubated from trauma to the face and eyes by the laryngoscope. The aim of immediate postnatal management should be the resuscitation and stabilization of both infants, thorough physical examination and special investigations that will allow for definition of the relevant anatomy, and subsequent medical and surgical management.

Cardiopulmonary resuscitation (CPR) in conjoined twins has significant limitations. Not only can it be physically challenging, but it may also be unreliable because the anatomy is distorted and access to the heart, especially in thoracopagus twins, is limited. Damage to other organs, particularly the upper gastrointestinal tract and liver, may occur (Millar et al., 2009). The basics of neonatal and pediatric resuscitation should be followed.

Medical and surgical management

Spitz and Kiely (2002) describe the management of conjoined twins in the prenatal and postnatal stages. When complex thoracopagus or craniopagus twins are diagnosed, termination of pregnancy is recommended. The postnatal management involves the following options:

Some overlap occurs when the twins arrive for emergency surgery before the results of all the investigations have enabled decisions around survival to be made (e.g., when intestinal obstruction develops). Emergency surgery is then performed, but later findings may indicate that other anomalies that are incompatible with life are present. In all studies, emergency surgery for separation is associated with a poor prognosis.

Indications for emergency separation include the following (O’Neill, 1998, Millar et al., 2009; Rode et al., 2006; Cywes et al., 1997):

Elective separation for simple conjunctions can be performed in the neonatal period with minimal problems. No benefit is gained from waiting for the infants to grow or for further investigations to be done. The maternal hormonal influences are still present; thus, the skin is more pliable to cover the wound defect. In general, separation is planned for some time between 4 and 11 months of age when the infants are bigger and their investigations are more meaningful and when they have had adequate tissue expansion to allow closure of the skin defect (O’Neill et al., 1988).

Investigations

Accurate preoperative imaging is essential to surgical planning and prognosis, and the area(s) of fusion determine the imaging modality used. MRI and CT provide very good anatomic and bone detail and show organ positions, shared structures, and limited vascular anatomy (Kingston et al., 2001). Radiography with contrast material provides excellent gastrointestinal and urogenital evaluation. When there is liver conjunction, its anatomy, the vascular supply, and assessment of the biliary tree are required. Angiography helps clarify the vascular supply of organs and determine blood supply between the twins. Careful use of contrast material is important, because there may be overenthusiastic administration of this in an attempt to achieve better views. Evaluation of vascular shunts and cross circulation is vital for anesthesiologists—loss of blood from these during surgery can be catastrophic.

Cardiac catheterization is required to identify intracardiac connections and to clarify cardiac chambers. Echocardiographic technology is constantly improving, so the need for catheterization (and therefore anesthesia) is becoming less common. When cardiac surgery is required, however, this is the preferred investigation (Fig. 29-5).

FIGURE 29-5 A cardiac catheterization image of complex cardiopagus thoracopagus twins with a catheter and contrast material in each heart. These twins could not be separated.

Results of these tests clarify anatomic variations in each infant. Understanding the complexity of organ conjunctions enables investigators to identify those structures that are present or missing. The results of complex investigations are best evaluated by a multidisciplinary team, because many factors are raised that anesthesiologists do not consider but that are important for both anesthetic management and good overall care of the infants. Each test has its own role for all of these requirements. Box 29-2 details investigations for craniopagus twins. The order in which procedures occur is also determined by the results of the investigations.

Planning before surgery

Multidisciplinary Team Preparation

Although the surgeons take the primary responsibility for the twins, it is often the anesthesiology team that assumes the role of the perioperative operating room organizers. Anesthesiologists are the caregivers who are present from the very beginning of the anesthesia, through each stage of surgical intervention (especially when more than one or two surgical disciplines are involved), until the end when handover to the intensive care unit staff occurs. Communication with the nursing personnel is imperative. The following list details all the disciplines that should be present at preparatory meetings:

Anesthesiology: Head of department team leader, specialists, technologists (especially when technical assistance is anticipated), trainees, and anesthesia nurses

Surgeons: General, plastic and reconstructive, cardiothoracic, orthopedic, neurosurgical, urologic, and ophthalmologic

Nursing: Operating-room manager or operating nurse leader

Intensive Care: Head of department or representative, nursing staff, pediatricians, cardiologists, and pulmonologists

Other Disciplines: Physiotherapist, occupational therapist, child life specialist

Hospital Management

Public Relations

In multidisciplinary meetings, the following should be discussed: the results of all investigations of all disciplines; an assessment of how they overlap in the different specialties; the order in which these surgical specialties will operate; any planned changes in the positions of the infants; locations where intravenous lines may or may not be placed; any anticipated problems or concerns; and whether or not intensive care will be necessary after the procedure. An example to illustrate the importance of such a discussion is a pair of ischiopagus twins who require defunctioning colostomies for intestinal obstruction. The pediatric general surgeon needs to perform the colostomies, the urologist needs to do an examination of the urogenital system under anesthesia, the orthopedic surgeons and neurosurgeons may require input for assessment of the sacrum and pelvis, and finally, the otolaryngologic surgeon has to assess one of the twins for upper airway obstruction and possible adenoidectomy. The use of diagrams of the anatomy, three-dimensional or CT-reconstructed models, and rehearsals in the operating room allow the process to proceed as smoothly as possible (Fig. 29-6).

FIGURE 29-6 This is a CT reconstructed image of a surviving ischiopagus twin’s spine after emergency separation when the other twin did not survive. This twin has required a number of surgical procedures to correct the abnormal anatomy of both the spine and pelvis.

Anesthetic care of conjoined twins

Anesthetic Challenges in the More Common Types of Conjoined Twins

Thoracopagus Conjunctions

Thoracopagus conjunctions are the most common form of conjunction. They are associated with a significant risk of complications, either when they are an isolated abnormality or when they are part of a complex cephalad or caudal conjunction. Sudden unexpected deterioration in respiratory and cardiovascular function in the preoperative period may occur, resulting in the untimely demise of both infants. Early intubation and ventilation with cardiac support may be necessary. Sudden death in this group is not uncommon.

Airway management is difficult because of the extreme lordosis and hyperextension of the infants, with variability of the proximity of their faces (Fig. 29-7). The higher the conjunction, the more difficult airway access becomes. This improves as they grow. Emergency intubation in either or both twins should be avoided. Their deterioration and the need for intervention should be anticipated, and the procedures should be carried out in a quiet and controlled way. Intubation should be done on one infant at a time, taking care not to damage the other twin in the process. It is not advisable to paralyze either infant until there is airway support and control in both infants. Except in moribund patients, awake intubation may be very difficult. It is usually easier to intubate the infants when they are on their sides, turned with the face upward. Positioning one infant above the other causes adverse hemodynamic and respiratory consequences in both infants and is not recommended.

FIGURE 29-7 This lateral photograph of a thoracopagus twin demonstrates the typical hyperextension of the head and neck and the exaggerated lordosis of this group of conjoined twins.

The use of laryngeal mask airways is not as successful in this group as in those twins whose heads face away from each other or in twins whose heads are at opposite ends of the body. Once the infants have been anesthetized, fiberoptic intubation has been used with success, but most intubations can be performed without it. It may be useful to insert a nasopharyngeal tube (a short endotracheal tube [ETT]) into one nostril to provide oxygen and an inhalational agent while attempting to intubate the trachea, either orally or nasally. Direct laryngoscopy and distal airway evaluation may be of value in the work-up before separation, but it is often difficult to insert a rigid bronchoscope without causing damage to the infants (Strocker et al., 2005). A fiberoptic technique is easier. There is little emphasis placed on investigating the respiratory systems of these infants. Lung abnormalities have been identified and include tracheomalacia and the presence of aberrant bronchi (Strocker et al., 2005).

Cardiac complications, especially cardiac failure in the neonatal period, are common. Anatomic possibilities include twins with a single normal heart, twins with two conventional hearts, or twins with compound hearts. The anatomy of major vessels may be extremely variable. With compound hearts, the extent of sharing may vary from minimal to almost complete (Gerlis et al., 1993). Coronary artery sharing usually coexists, even with minor venous sharing, and fusion may occur at the level of the sinus venosus, at the atrial level, or at the atrial and ventricular levels. Cruciate connections from the right atrium of one infant to the right atrium of the other, or from the left ventricle of one to the left ventricle of the other, may be present (Gerlis et al., 1993). Many of the components may only be determined at surgery (or postmortem). For technical reasons, it is often difficult to differentiate whether the ventricles are contiguous or fused.

Electrocardiograms (ECGs) in these infants are interesting, but are not conclusive. The presence of two complexes does not rule out significant abnormalities, and a single complex does not necessarily mean significant sharing of heart structures. Reciprocal complexes, or those appearing as a mirror image, usually indicate shared hearts. (Fig. 29-8)

FIGURE 29-8 This is the ECG of thoracopagus twins who share a pericardium but have separate hearts. The complex of one twin is superimposed on that of the other.

Cardiovascular and respiratory instability may occur with any maneuver that alters the intrathoracic pressures and moves the hearts and lungs of each infant back and forth between them. Coughing, crying, and breath-holding are all contributing factors. Positive pressure ventilation should be timed in both infants to avoid this complication. This can be achieved with manual ventilation, synchronized intermittent positive pressure ventilation, or with the use of circuits made up to ventilate both infants with a single ventilator. With the latter method, good chest movement (and capnography) is a vital clinical indicator of adequate ventilation.

Central vascular access, whether subclavian, internal jugular, or femoral, is difficult because of variable anatomic differences, which make the usual anatomic landmarks unreliable. Ultrasound has been helpful in identifying these vessels. Blood loss, as with most conjoined twins, may be significant (two to three times the estimated blood volumes).

After separation, postoperative ventilation is generally the rule rather than the exception. The repair of deficits in the anterior chest wall needs to be planned, because most require some sort of structural support to facilitate normal ventilatory mechanics and to avoid the development of a flail segment (Hoshina et al., 1987).

Omphalopagus Conjunctions

Omphalopagus twins range from a very simple conjunction containing fibrous tissue or a sliver of liver, to an extremely complex conjunction. If the livers are extensively fused, blood loss may be considerable. Complex hepatobiliary fusion and proximal gastrointestinal sharing of organs may complicate surgery. Airway access may be difficult but not as hazardous as it is in thoracopagus twins. In more complex conjunctions, ventilatory challenges are the same as those for thoracopagus twins (i.e., coughing and straining in one twin affects the other’s ability to breathe properly).

Ischiopagus and Pygopagus Conjunctions

Airway management is not usually a problem except in those cases where a compound or complex conjunction is present. In general, the twins’ faces, heads, and necks are easily accessible for intubation. As with thoracopagus twins, if their abdomens are joined, abdominal contents can move between the infants with Valsalva maneuvers and may compromise the ventilation and diaphragmatic excursion of the other infant. In ischiopagus twins before separation, bowel surgery for intestinal obstruction may be necessary.

Especially in twins where posterior osteotomies are required for pelvic ring closure, blood loss may be extensive. This may also occur suddenly and unexpectedly with dural incision and when vascular structures are unpredictable (Fieggen et al., 2004).

Tethering of the cord, spinal dysraphism, cord fusion, and syringomyelia, in association with anorectal and urogenital abnormalities, are often encountered in ischiopagus, pygopagus, and dipagus twins (Peter et al., 1996). This may preclude the use of spinal or epidural anesthesia in these twins unless ultrasound views clearly identify the anatomy.

If nerve stimulation is required by the surgeon to identify the nerve routes, muscle relaxation should not be used. Preoperative documentation of the neurologic status is essential.

Preoperative bowel preparation may cause fluid losses that need to be factored into preoperative and intraoperative fluid-administration requirements.

Neurosurgeons are experts in the management of craniopagus twins, but their expertise is also required for both ischiopagus and pygopagus conjoined twins who may have a variety of spinal abnormalities (Peter and Fieggen, 2004). These may present challenges both at the time of separation as well as for long-term management. In the presence of hemivertebrae, asymmetric or small chest cavities, or spinal anomalies, progressive scoliosis may develop and will require diligent follow-up care and possible intervention (Fig. 29-9) (Fieggen et al., 2004; Rode et al., 2006).

FIGURE 29-9 This is the surviving infant of ischiopagus twins with spinal deformities who requires follow-up surgery. His CT is shown in Figure 29-6.

Duplication of an anatomic area (e.g., ischiopagus dipagus, a single trunk but four legs) is amenable to surgical correction with a good outcome (Fig. 29-10). Anesthetic problems in this group are similar to those that would be experienced with tumors of that region, namely vagal stimulation with manipulation of the mass and blood loss.

FIGURE 29-10 Ischiopagus dipagus twins are seen here. One with lower extremity duplication, where the abnormal segment comprises the middle two limbs. A pelvic osteotomy is usually performed to facilitate rotation of the legs into a normal position. If a heteropagus parasite occurs at this site, an osteotomy is not usually necessary.

Craniopagus Conjunctions

Because of the proximity of the infants’ heads and faces, airway management of these twins is often a challenge. Stabilization of the ETT requires particular attention, and fluid or blood from the surgical field can result in dislodgement or displacement during surgery with potentially catastrophic consequences. Especially if significant flexion is anticipated, a reinforced ETT may be the best option. Many of the principles of pediatric neurosurgery apply, including the potential for venous air embolism, and these are affected by the complexity of the conjunction (Girshin et al., 2006). Walker and Browd (2004) provide a comprehensive approach to the embryology, classification, surgical anatomy, and separation of craniopagus twins.

If the venous sinuses of the twins are in communication in the fusion, blood loss may be enormous, and it is often this factor that limits the possibility of surgery for separation. The abnormal development of the arteriovenous system is one of the greatest challenges faced during the separation procedure. To reduce blood loss and allow each child to develop adequate independent vascular drainage and to prevent perioperative cerebral edema, staged separation may be indicated (Walker and Browd, 2004; Girshin et al., 2006). These staged operations have been attempted to encourage the development of a collateral circulation before final separation and to improve outcome.

The preoperative neurologic status needs meticulous documentation, because the degree of neurologic deficit after surgery depends on the extent of brain, vascular, and meningeal conjunction and the complexity of the procedure.

Central vascular access may be limited to the femoral route.

Preoperative Evaluation

Each type of conjoined twins has challenges specific to their type of conjunction. A comprehensive knowledge and understanding of the pathophysiology of conjoined twins is essential to good anesthetic management. Procedural planning sessions and rehearsals are invaluable to identifying potential or actual stumbling blocks.

The preoperative visit should be as that for any pediatric patient, but there should be particular emphasis on a number of the factors previously described. For urgent operations or separation, rapid preoperative evaluation and assessment before transportation to the operating room is necessary. Prior experience with conjoined-twin management provides considerable advantages at this time.

A thorough goal-directed review that includes the history of perinatal events and growth since birth, exposure to infectious diseases (e.g., human immunodeficiency virus), and whether or not and what prophylaxis was taken (mother-to-child transmission medication), as well as previous intubation experience for respiratory or cardiovascular pathology, is required. An understanding of the complexities of each investigation and the implications of these for surgery (and therefore anesthesia) is vital. It is especially important to understand the degree of cross circulation between the twins and at what anatomic level this may be present (e.g., heart, liver, brain, or bowel) (Table 29-3).

TABLE 29-3 Summary of Multidisciplinary Investigations Commonly Required for Conjoined Twins

System	Investigation
Cardiorespiratory Cross circulation	Radiography: total body X-ray Electrocardiogram Echocardiography/Doppler ultrasound in all conjoined twins MRI/CT with contrast Angiogram Radioisotope scan Tc-99-DMSA, radiolabeled albumin, or red blood cells45
Alimentary tract	Contrast meal and enema Ultrasound Radioisotope scans53 (liver); technetium Tc-99m-(Sn), colloid and excretion Tc-99m mebrofenin Radioisotope scintigraphy
Genitourinary	Ultrasound Isotope renography Micturating cystourethrography Genitogram
Skeletal system	Radiography MRI (spinal cord) Ultrasound
Vascular	Doppler ultrasound Angiography

Modified from Di Rocco C, Caldarelli M, Tamburrini G, et al: Craniopagus: the Thessaloniki-Rome experience, Childs Nerv Syst 20:576–586, 2004; Mann M, Coutts JP, Kaschula ROC, et al: The use of radionucleotides in the investigation of conjoined twins, J Nucl Med 24:479–484, 1984; Rode H et al: Four decades of conjoined twins at Red Cross Children’s Hospital: lessons learned, S Afr Med J 96(9):931, 2006; Rutka JT, Souweidane M, ter Brugge K, et al: Separation of craniopagus twins in the era of modern neuroimaging, interventional neuroradiology, and frameless stereotaxy, Childs Nerv Syst 20:587–592, 2004.

Especially in thoracopagus twins, signs of cardiovascular decompensation should be sought. These include tachypnea, tachycardia, decreasing saturations, loss of appetite, and failure to thrive.

Regardless of the degree of cross-circulation, drugs should be administered as they would be for two separate individuals. The weight of a heteropagus infant, however, should include the weight of the parasitic part until it is removed and can be regarded in the same light as a pediatric patient who has a tumor that requires resection. For most symmetric twins, the two infants are more or less the same size, so it is appropriate to take their combined weight and halve it to arrive at the weight of each infant.

Careful consideration should be given to where catheter lines should be placed, which cannulae should be used, and how many will be necessary for the particular procedure. Doppler ultrasound has been useful in identifying the site of central vessels, but because of space limitations in some sets of twins, it is not always easy to insert the catheter lines under direct vision. In these infants, it is easier to identify the vessels, place the ultrasound probe aside, and then attempt cannulation, or to have an assistant hold the probe while cannulation is attempted.

Physical Examination

Importance must be given to assessing the following:

The Airway

Managing the airway is crucial to good anesthetic management, and certain types of patients have predictably more difficult airways than others. In general, airway management of ventrally conjoined twins is more difficult. Problems with the airway in conjoined twins include:

• Access to the mouth and larynx is difficult.

• Visualization of the vocal cords may be impossible. Close faces leave little room to move to insert instruments in the airway.

• Placement of the ETT through the cords is challenging, because it tends to get caught on the subglottis. Rotation of the tube through 180 degrees as it passes through the cords facilitates this maneuver. Fiberoptic intubation, either directly or via a laryngeal mask, may be a valuable adjunct. Other techniques that may help include all the usual pediatric anesthetists’ tricks to bring the larynx into view: the use of one’s little finger, having an assistant provide rotational pressure on the larynx; and the use of a stitch into the infant’s tongue to pull the hypomandibular structures forward and allow visualization of the epiglottis and cords (Fig. 29-11). The successful use of the Magill’s forceps is often compromised by lack of space both inside and outside the mouth, but oral intubation is usually easier than the nasal route. Once placed correctly, secure strapping of the ETT is critical.

FIGURE 29-11 Intubation of thoracopagus twins demonstrating the use of an assistant’s finger to bring the vocal cords into view. This photograph also shows the airway of the other twin being managed while the intubation is taking place.

Thoracopagus Twins

Thoracopagus twins have difficult airways until proven otherwise. There is invariably some degree of opisthotonus and hyperextension of the head and neck, making visualization of the vocal cords very difficult. Plans for fiberoptic-assisted intubation may be necessary. In order to facilitate long-term ventilation, tracheostomy has been described in one set of twins, but this should not be regarded as the routine recommendation of airway management (Mair and Mair, 2006). Depending on the relative positions of the heads and faces, craniopagus airway access may also be problematic.

Mechanisms of Ventilation

It is important to ascertain whether or not the diaphragm is involved in the junction, or whether its function will be affected by surgery. In those twins where conjunction involves the chest wall and its contents, serious consideration needs to be given to breathing and ventilation. Lung compliance is affected, areas of atelectasis develop because of the limited space between the two infants and the abnormal anatomy of thoracic structures, the hearts are usually abnormal, and cardiac failure is common in thoracopagus twins. As one twin develops cardiorespiratory compromise with tachycardia, tachypnea, and coughing, the other is also affected. This has significant short- and long-term consequences and should be a major consideration when planning for separation. New synthetic substances that enable reconstruction of an unstable sternum and anterior chest wall are now available. Muscle flaps and skin grafts may be needed (Rabeeah, 2006). In the postoperative period, these grafts avoid the development of a flail chest, which causes significant respiratory compromise and affects long-term survival and quality of life. In cases where one twin has not survived, autologous tissue has been used to cover the deficit caused at separation (Rode et al., 2006; Spitz and Kiely, 2002; Fisherman et al., 2002).

Cardiovascular System

Assessment of the heart and major vascular anatomy is crucial, because this impacts anesthesia and vice versa. Craniopagus twins may, as with thoracopagus twins, have cardiac failure. Because many of these infants will have spent considerable time in the hospital, venous access may be a challenge, and ultrasound guidance for central venous access may be necessary. Intravenous catheters within the surgical field should be avoided.

Disability

In craniopagus twins or any of the types where the spinal cord may be involved in surgery, a full neurologic examination is required. This is especially the case if any neuroaxial intervention or procedure is planned as part of the anesthetic. Bowel and bladder function must be documented. It may not always be possible to place a urinary catheter, and urine output may not always come from the kidneys of that infant. This problem occurs when one or both ureters cross over from one infant to the other’s bladder.

Gastroesophageal Reflux

Gastroesophageal reflux is most common in thoracopagus twins, although it may occur in any type of conjoined twins. Nursing the infants with their heads up is helpful, and the use of antireflux medication should be considered.

While they are waiting for separation, good nutrition is crucial to the infants’ growth. The body composition differs between the two twins, as does their resting energy expenditure and caloric intake. This difference stabilizes after separation, with both twins having similar requirements (Powis et al., 1999; Spitz and Kiely, 2002).

Skin Cover: Tissue Expanders

Tissue expanders are inserted to facilitate skin closure when surgery will leave a significant area uncovered. There are numerous reports in the literature of the use of tissue expanders in many sets of all types of conjoined twins. The advantage of their use includes the provision of autologous tissue to cover the defect, thus avoiding the need for the use of foreign material. The disadvantages are the effects of pressure exerted by the expanders in all directions on contiguous tissue where pressure is not desirable. Areas of skin covering the expanders may become necrotic or infected, and the expanders may need to be removed. The inward pressure may affect cardiorespiratory function and result in twins with preexisting lung disease requiring ventilation before separation (Losee et al., 2009). Immediately after insertion, intraabdominal tissue expanders may initially cause an ileus, and they may cause anorexia as the volume in the expanders increase. For craniopagus twins’ skin expansion, especially in younger infants, the pressure effects may impact the growth of underlying bone, resulting in a deformed skull. Depending on the age of the infants, the site chosen for placement of the expanders, the number of expanders inserted, the length of time they will be in place vary, as does the volume of fluid injected (100 to 1,000 mL) to expand the tissue sufficiently. The smaller the infant, the more critical is the volume injected. The shape of the expanders are determined by the age of the infants and the sites chosen for their placement. Depending on the decision of the surgeon, the expanders may remain in situ for anything from 6 weeks to several months.

Wound closure in craniopagus twins is critical, because skin, dura, and bone cover are necessary to prevent perioperative wound breakdown, cerebrospinal leaks, and meningitis. Skull defects may be left to granulate closed, or bone from other sites such as ribs may be used. Fascia lata may be used for dural cover, and prosthetic material (e.g., a titanium plate) may be considered. Malformation in the skull configuration may not allow or accommodate tissue expanders. The risks associated with the prolonged time necessary for tissue expansion may preclude their use (Walker and Browd, 2004).

The site(s) for tissue expanders need to be chosen carefully, and everything possible should be done to avoid complications that may necessitate their removal because this leaves areas of fibrosis and scarring, thus limiting availability of suitable skin for cover later. Skin sepsis and wound breakdown are the most common reasons for the removal of expanders, and this delays surgery for separation.

An important consideration for all medical staff caring for children with tissue expanders is that of pain at the injection port when injecting fluid into the expanders. The port(s) may be on only one or on both of the infants, and before injection of the expanders local anesthetic should be used on the skin covering the port. In one set of twins, this problem was ignored, and at the time of each injection the twin with the port developed significant anxiety, whereas the other remained unconcerned. This also impacted on the management of postoperative pain and anxiety of the same twin.

Alternatives to the use of tissue expanders include the use of pedicle flaps, periosteal flaps, and skin grafts. Methods for reconstruction of the deficit caused by separation continue to be explored.

The size of the deficit can be measured preoperatively by physical assessment of the size of the potential defect (measuring with a tape measure and three-dimensional CT reconstruction), as well as by the use of acrylic models (Campbell, 2004). This information may then be used to facilitate reconstruction.

Anesthetic implications of the use of tissue expanders include preoperative assessment of the pressure effects of the expanders on the different organ systems. This includes the effects on the skin and the cardiovascular system. The need to remove the expanders may present significant logistic implications for the operating room staff. All of the challenges of anesthetizing these infants, albeit for a relatively small operation, present themselves—two teams, two sets of equipment, and the need for vascular access are just a few to mention.

Anesthesia for non–separation procedures

A variety of preseparation or palliative procedures and investigations can be expected. These may include surgery to remove an inappropriately sited limb, place tissue expanders, perform laparotomy for intestinal obstruction, divert stomas, repair an inguinal hernia in one twin, perform gastroschisis, complete urologic procedures such as vesicostomy, do an adenoidectomy for adenoidal hypertrophy and obstructive sleep apnea in one twin, and to repair necrotizing enterocolitis (Hoyle, 1990; O’Neill, 1998; Jaffray et al., 1999; Seefelder et al., 2003; Lonnee et al., 2007). The possible investigations are listed in Table 29-3. Anesthesia preparation and preoperative evaluation for these procedures should be based on the same principles of management as for separation, but the planning for separation involves a more comprehensive approach to the intraoperative and postoperative care.

To prevent confusion and to allow all medical staff to understand the procedure, simple but accurate diagrams of the anatomy should be provided at preoperative discussions.

The questions that need to be answered preoperatively are listed in Box 29-4. Routine pediatric anesthetic preoperative blood tests are required, and blood should be cross-matched according to the procedure planned.

The size, age, and state of health of the infants; the site and complexity of their conjunction; the anatomy of organs involved; the organs or structures that are missing; the presence of other congenital anomalies; and the degree and location of cross circulation are all vital factors in planning for anesthesia and surgery. Regardless of the procedure or operation, neonatal conjoined twins are a considerable challenge. The younger and smaller the patients are, the more complex the conjunction, and the presence of associated congenital anomalies may complicate all aspects of the anesthetic management. Thoracopagus and craniopagus twins have a higher perioperative morbidity and mortality. The greater the extent of the junction, the more organs are affected by fusion or by being absent.

A dead or dying twin, if not quickly separated from its twin, aggravates the acidosis and causes deterioration and death of both infants (Fig. 29-12). That error was made in one set of twins. By the time they were prepared for surgery nearly 24 hours after birth, one of the twins was regarded as moribund and was not resuscitated or ventilated in the intensive care unit, and this nearly resulted in the death of his brother. As the ill twin deteriorates and dies, there is extensive vasodilation and acidosis, so the intravascular volume of the surviving infant transfuses into the dead twin, causing the healthier twin to succumb. The biochemical challenges are similar to those of a reperfusion syndrome.

FIGURE 29-12 A set of ischiopagus twins where one twin deteriorated rapidly before surgery, necessitating emergency separation. To minimize the metabolic consequences, the dying twin should also have been intubated and ventilated.

Airway difficulties are more common in those infants where the conjunction is high on the chest, where the heads face each other and are close together, where the head and facial anatomy is abnormal, when hyperextension of the head and neck with exaggerated lordosis is present, and where the parasite of a heteropagus twin is around the head, neck, or upper chest (Fig. 29-13). Vascular access is anticipated to be difficult in this group.

FIGURE 29-13 A heteropagus conjunction of the upper chest may have an impact on airway management. This one did not cause any problems.

Vascular access, especially central venous access, is challenging, because deviation from normal anatomic relationships of arteries and veins is common. When available, ultrasound guidance is recommended.

The greater the extent of the fusion, and the more complex the organ involvement, the greater is the propensity for significant blood loss (more than one estimated blood volume) at the time of separation. Blood loss may be obvious (e.g., with thoracopagus or craniopagus), but it may also be covert, as occurs in ischiopagus twins, where posterior osteotomies result in a slow, constant ooze under the dressing and out of sight of the anesthetist. Appropriate preoperative cross-matching of blood and products for intraoperative use is essential.

The need for cardiopulmonary bypass brings with it technical difficulties in inserting cannulae, space in the operating room, and all the consequences and complications of open heart surgery (Suan et al., 1998). Preoperative planning is critical for successful outcomes.

During the week before surgery, in order to ascertain whether the infants will fit onto the operating table, their length and width must be measured. This is especially important in larger, older sets of twins, who will have grown since their previous procedure. In consultation with each of the surgical specialties (especially if the positions need to be changed) and nursing staff, positioning of the infants for surgery must be defined and accommodated. All catheter lines, monitoring, and diathermy should be placed accordingly.

Support materials, such as sponge supports for upright twins or a special chair, may take time to prepare (Fig. 29-14) (Mair and Mair, 2006). When extra limbs or abnormally sited limbs are present, careful protection of these limbs during surgery should be ensured.

FIGURE 29-14 Thoracoomphaloischiopagus twins, with tissue expanders in the upper abdomen and lower chest. Because of the unusual positioning during surgery, careful attention to blood pressure, oxygen delivery, and cerebral perfusion is necessary.

Anesthesiologists should prepare for numerous changes in position. When conjunctions are very complex and a number of surgical specialties are involved, the changes in position require forethought and planning. Color coding is of particular value at this time. Meticulous care of the ETTs is essential. Arterial and venous lines need to be moved in an orderly fashion so as to avoid the otherwise inevitable tangle that takes a long time to unravel. Certain equipment, such as diathermy, may need a new site after each change in position.

A rehearsal in the operating room may be very useful to all concerned. Infants should be handled gently and safely; as they grow, they are heavier and more active. If they are fed immediately before their arrival for this exercise, the infants are usually very cooperative.

A preoperative discussion with all role players is necessary, but especially among those anesthetists involved in the procedure; they should display a diagram of the anatomy and the planned surgery and discuss the extent of circulatory mixing, the positions required, and the order of the procedures. This discussion allows rational ordering of blood and blood products based on calculations of anticipated blood and fluid losses. It is also useful to have a written agenda to follow during the procedures.

Anesthesia providers should be sure to have a double supply of all necessary equipment: anesthesia machines, monitoring, infusion devices, blood warmers, and temperature control modalities. Point-of-care blood analyzing facilities must be checked and ready for use.

As space is often a problem, a drug cart may be shared between the two anesthesiology teams, but drugs should be drawn up independently for each infant. The routine drugs available should include analgesics, anesthetic agents, muscle relaxants, inotropes, and other specific requirements of any of the surgical specialties. Emergency drugs include epinephrine, phenylephrine, norepinephrine, sodium bicarbonate, calcium, and steroids. Aggressive cardiac resuscitation may be necessary in all but the simplest conjunctions.

The operating room should be arranged to suit the type of twins; thoracopagus and craniopagus twins tend have the anesthetic machines at the same end of the table, whereas ischiopagus twins’ surgery necessitates that the machines be at opposite ends of the operating room table (Fig. 29-15).

FIGURE 29-15 The arrangement of the operating room for thoracopagus twins’ separation is shown here. A single operating table but duplicate anesthetic machines, monitoring and warm air devices, syringes drivers, and drug carts were used.

Color coding of each infant’s equipment with all the lines, monitors, equipment, and drugs is very useful (Fig. 29-16). Color coding for each team is also valuable, especially when there are two surviving infants to be operated on in two operating rooms or on two separate operating tables.

FIGURE 29-16 Color coding of each child, equipment, lines, and monitoring provides easy identification and prevents drug and fluid administration errors.

At the separation of ischiopagus or pygopagus twins, posterior osteotomies may be performed to facilitate pelvic ring closure (Verrier et al., 2000). The approach to the iliac spines is from the back of each infant, and appropriate positioning may be a problem. Positions are rehearsed when the infants are awake, and innovative plans may be necessary to achieve the correct positioning of the infants for surgery (Fig. 29-17). Postoperatively, the legs of the infants are anteromedially rotated and strapped in position for 6 weeks; this will impact their diaphragmatic excursions with the potential for atelectasis and pneumonia (Fig. 29-18). Physiotherapy is crucial to their recovery.

FIGURE 29-17 For many of the surgical procedures on conjoined twins, innovative positioning for the operation may be necessary. Because of their complex conjunction, this was the most ideal position possible to expose the back of each infant for its posterior osteotomies.

FIGURE 29-18 After pelvic ring closure in ischiopagus twins, the legs need to be kept in the same position for up to 6 weeks after surgery. This requires firm bandaging of the legs and pelvis, as shown in this photograph.

Drug pharmacokinetics and pharmacodynamics may be inconsistent. The use of contrast, radioisotopes, and drugs have all been used to determine the extent of cross circulation, but it is safest to assume some degree of it until proven otherwise. In practical terms, thoracopagus and craniopagus twins have a considerable degree of cross circulation, and few have none at all. The option of local and regional anesthesia use should always be considered, and it should be used whenever possible. Where there is the potential for considerable blood loss, or where there are other contraindications, these techniques should be used with caution.

Control of traffic in the operating room is essential. Noise and congestion are distracting and not in the patients’ best interests. Strict guidelines, drawn up by operating room staff and hospital management, must be in place well before embarking on any surgical procedure. Advances in communication technology allow for operations to be viewed via constant in-operating room camera feed, to a distant venue where interested parties can observe proceedings. This also provides a valuable teaching experience for students of all disciplines who cannot be directly involved in the anesthesia and surgery.

Everyone should take time to check everything as a team just before the twins are brought into the operating room.

Anesthesia for separation

Nonemergency surgical separation is usually planned for between 4 and 11 months, when the infants are larger and the investigations have given information that is clearer and more meaningful. After this age, psychological issues with separation become more problematic (O’Neill et al., 1988). This operation is the culmination of a multidisciplinary preparation that hopefully will end in the successful separation of a pair of conjoined twins.

Transport

Transportation of the infants to operating room may well be a simple process, and they may be brought to the operating room door by the parents and accompanied by a nurse. In ill twins who have been in intensive care and who are intubated with all invasive catheter lines in place, transportation to the operating room involves the use of a transport monitor and a ventilator for each twin, and the accompaniment of two anesthesiologists. Maintaining normothermia in transit is essential, and meticulous attention to the airways and intravascular lines reduces the possible risk of disconnection or dislodgement at this time. Each anesthesiologist must clearly understand his or her role during this process. Box 29-5 gives a preparatory checklist for the anesthesiologists before caring for conjoined twins.

Box 29-5 Preoperative Conjoined Twin Checklist

• Preparation of operating room (duplicates of all equipment): anesthetic machines; infusion pumps; temperature of operating room set between 26° and 28° C; warm air devices and blankets; grounding pads (one between two at the beginning of surgery is acceptable and changed to one each after separation); a second operating room table to be brought into the operating room (or preparation of another operating room if one of the twins is to be moved); invasive monitoring equipment ready for use; egg-box sponge; silicone pads or rings or an equivalent for pressure protection during the procedure (Fig. 29-19); labels to distinguish drugs and equipment for each twin

• Vascular access devices (central and peripheral)

• Ultrasound machine for intravenous access

• All drugs, routine and emergency, drawn up in duplication for each infant

• Intravenous fluid and blood administration sets for each twin

• Blood cross-matched and immediately available

• Techniques to minimize blood loss, such as the use of cell savers or a protocol for major blood loss, should be considered when massive or sudden blood loss is anticipated (Paterson, 2009)

• Confirmed availability of intensive care beds

FIGURE 29-19 The use of soft bandages and plastic protect the legs during surgery and prevent heat loss.

Induction

Techniques for induction of anesthesia are determined by the airway, the availability of intravenous access at induction, the state of health of each infant, the drugs available, and the preferences of the attending anesthesiologists. In those twins with potentially difficult airways, spontaneous respiration with inhalational induction with sevoflurane or the intravenous use of ketamine is helpful (Fig. 29-20) (Thomas, 2004; Thomas and Lopez, 2004; Diaz and Furman, 1987). In this same group, a lidocaine “gargle” before induction to partially anesthetize the airway is a useful technique (2% lidocaine sprayed into the infant’s mouth before starting the anesthetic). In infants with cyanotic congenital heart disease or in those with complex anatomy, intravenous ketamine is a safe option (Thomas and Lopez, 2004; Diaz and Furman, 1987).

FIGURE 29-20 This inhalational induction in thoracopagus twins with a high conjunction demonstrates the close proximity of the airways of many of these infants.

Muscle relaxation must not be used until airway access is assured. Rapid sequence induction is often not possible in ventrally conjoined twins. Ideally, intravenous access should be established in the ward before transfer to the operating room, but because many of the infants have been in the hospital for some time, this may not always be possible. When this is the case, inhalational induction may be followed by the use of topical local anesthetic spray (2% lidocaine) to the vocal cords to facilitate intubation. The type of ETT and the route used (oral or nasal) are determined by the type of conjunction (nasal is not suitable for craniopagus twins surgery, and this route is often very difficult in thoracopagus twins), whether or not postoperative ventilation is planned, whether the surgical position requires the use of a reinforced tube, and how accessible the infants’ faces and ETTs are during surgery. To facilitate postoperative ventilation, oral tubes may be changed to nasal tubes at the end of the procedure. Good securement of the ETT is crucial, and inadvertent extubation during surgery may be disastrous.

In cases when the airway is not a problem and the infants are hemodynamically stable, any agent commonly used for pediatric anesthesia is suitable. Intravenous inductions using propofol, etomidate, thiopentone, and ketamine have all been used successfully.

Prognosis

Immediate and long-term survival of conjoined twins is extremely variable. Outcomes are better in twins who do not share vital organs, but many of these children still have considerable rehabilitation requirements. Despite tissue expansion, the use of prosthetic materials, skin grafts, complex plastic surgical flaps, and innovative methods to provide skin cover to close those areas exposed by the separation remains an ongoing challenge.

Hidden long-term morbidity and mortality occur with unresolved aspiration after thoracopagus separation; bronchopneumonia, arrhythmias, and embolic cerebrovascular pathology occurred in one survivor when the entire cardiac complex had been assigned to one infant (Rode et al., 2006; Millar et al., 2009).

For many years after their separation, some patients must undergo further surgery to reconstruct shared pelvises and urogenital systems, to improve wound closure with skin grafts, and to revise their anatomic abnormalities in an ongoing effort to improve the quality of their lives. Some survivors will be disabled and require lifelong follow-up care. For many others, life goes on with minimal sequelae (Figs. 29-21 and 29-22).

FIGURE 29-21 The ischiopagus twin girls from Figure 29-3, 5 years later.

FIGURE 29-22 An ischiopagus dipagus survivor, 4 years after surgery to remove the duplicate segment, riding his tricycle in the ward.

Conclusion

Many lessons have been learned over generations, and these include the need to consult widely—locally and internationally. The Internet makes this extraordinarily easy. It is important to search using both the American and English spellings of anesthesia and anaesthesia, because different references appear as the result of a search, and there is very little overlap. Descriptions of anesthetic challenges are being reported from all over the world in different socioeconomic and political circumstances, and each article teaches something of value (Bloch and Karis, 1980; Norsidah et al., 1996; Huanc et al., 2004; Leelanukrom et al., 2004). Whether surgery for separation is an option or not, an experienced multidisciplinary team approach to the management of these infants results in the overall improved handling of the patients and their parents. Success requires an experienced team functioning in a tertiary referral center with the full range of medical, surgical, and anesthetic specialties (Spitz and Kiely, 2003).

As technologies improve, anesthesia and intensive care will continue to positively impact the surgical outcomes of this fascinating and challenging group of patients. Some of these infants and children will grow up to become adults, so a greater understanding of the long-term outcome of this extraordinary pathology is essential. Although the physical needs of these children are usually addressed, the emotional consequences of their pathology should always be kept in mind and addressed.

Many of the basic principles of anesthetic care have not changed much in 60 years, but advances in anesthetic equipment, monitoring, investigative technology, pharmacology, and surgical materials make the desirable outcome of surgery, as well as the long-term prognosis for a good quality of life for conjoined twins, an attainable reality.