Surgical Procedures and Special Techniques

The ultimate objectives for congenital heart surgery are (1) physiologic separation of the circulation, (2) relief of outflow obstruction, (3) preservation or restoration of ventricular mass and function, (4) normalization of life expectancy, and (5) maintenance of quality of life. The available surgical procedures to accomplish these objectives are diverse and complex ( Table 51-4 ). Compared with cardiac operations in adult patients, pediatric congenital heart repairs involve more intracardiac surgery, with a greater preponderance performed via the right atrium and RV. In general, operations performed for congenital heart defects can be divided into palliative and corrective procedures.^[25] The type and timing of repair depend on the age of the patient, the specific anatomic defect, and the experience of the surgeon and the team (see Table 51-4 ).

Palliation in infancy is usually performed when there are missing anatomic parts, as in pulmonary atresia (absent RV and pulmonary artery), tricuspid atresia (absent RV and tricuspid valve), hypoplastic left heart syndrome (aortic atresia and hypoplastic LV), univentricular heart (absent RV or LV), and mitral atresia (absent LV). These palliative procedures can be further subdivided into those that will increase pulmonary blood flow (PBF), those that decrease PBF, and those that increase mixing (see Table 51-4 ). Palliative procedures that increase PBF include shunts (Blalock-Taussig, central, and Glenn), outflow patch, and enlargement of the VSD. Those that decrease PBF include pulmonary artery banding and ligation of a PDA. Those that improve intracardiac mixing include atrial septostomy (balloon, blade, and Blalock-Hanlon).

The improvements in surgical technique, coupled with advancements in anesthetic and technologic support, make repair in early infancy not only feasible but in many cases preferable.^[26] Currently, repair in infancy can be offered for a number of congenital heart defects, as shown in Table 51-4 . The timing of surgical intervention reflects medical necessity, physiologic and technical feasibility, and optimal outcome. Cardiac defects that require a PDA to sustain sufficient systemic or pulmonary blood flow (e.g., pulmonary atresia, hypoplastic left heart syndrome, interrupted aortic arch, critical aortic stenosis, and critical pulmonic stenosis) require an intervention in the neonatal period. A variety of defects are optimally repaired in early infancy. Lesions such as transposition of the great arteries may exhibit better left ventricular

2013

Figure 51-3 Changes in ventricular physiology that accompany abnormal pressure and volume loading in human adolescents and adults. Schematic represents the changes in cross-sectional ventricular geometry that accompany abnormal pressure and volume loads. Data are measured and derived from catheterization and echocardiography of 30 adolescent and adult human subjects. Pressure overload triggers significant increases in wall thickness and wall thickness:radius ratio (h/r), but these compensatory mechanisms preserve σ within normal limits. Whereas volume overload causes dilation and enough hypertrophy to preserve normal σ_S , diastolic function deteriorates significantly. h-LV, posterior myocardial wall thickness; LVp, left ventricular pressure; r, radius of the LV chamber; σ_D end-diastolic wall stress; σ_S , peak systolic wall stress; * p < .01. (From Grossman W, Jones D, McLaurin LP: Wall stress and patterns of hypertrophy in the human left ventricle. J Clin Invest 56:56, 1975.)

2014

Although some lesions merit repair whenever they are diagnosed (e.g., total anomalous pulmonary venous return, coarctation of the aorta), others exhibit such a wide spectrum of physiologic disturbance that the timing of an intervention must be made individually (e.g., VSD, aortic stenosis, pulmonic stenosis). A few cardiac malformations produce pathophysiologic changes that are sufficiently mild that repair is typically deferred to later infancy or childhood (e.g., isolated ASD). Palliative surgery is entertained when a physiologic derangement requires intervention, but circumstances preclude definitive repair.

In general, the recent trend in pediatric cardiovascular surgery has been to repair defects in infancy rather than palliate.^[26] This trend reflects improved technical capabilities coupled with a desire to limit the morbidity and mortality associated with long-term medical management and the sequelae of multiple palliative operations. Early corrective surgery is expected to decrease the incidence of the chronic complications of congenital heart disease, such as the problems associated with ventricular overload, cyanosis, and pulmonary vascular obstructive disease.^[27] Early infant repair may also have the selective advantage of enhancing organ system protection during repair because of poorly understood factors promoting resistance to injury and enhanced recovery potential (i.e., enhanced plasticity). With the continued improvement in surgical techniques and the early treatment of congenital heart disease, specific organ systems such as the brain, heart, and lungs will be spared the detrimental effects of chronic derangements of hemodynamics and oxygen delivery.

Procedures for the treatment of congenital heart disease continue to evolve to decrease long-term morbidity and enhance survival. For example, the long-term problems with right ventricular dysfunction and failure associated with the Mustard procedure for repair of transposition of the great arteries encouraged many surgical groups to develop the neonatal arterial switch operation.^[28] Early indications suggest that the latter procedure provides an anatomic correction with better long-term results. A second example of the continuing evolution of technique is surgery for tetralogy of Fallot. Longstanding pulmonary insufficiency after right ventricular outflow repair for tetralogy of Fallot is associated with right ventricular dysfunction and failure. Preservation of the pulmonary valve at initial repair using a combined transatrial and transpulmonary approach during correction or the early insertion of a pulmonary homograft in the setting of pulmonary insufficiency are techniques being used in an attempt to avoid the long-term problems of right ventricular dysfunction and failure.^[29] Surgery for hypoplastic left heart syndrome, once considered a fatal disease, has achieved significant long-term survival in a growing number of institutions after a series of staged reconstructive procedures.^{[30] [31]}

Surgical management has evolved in a broader application of certain surgical procedures initially designed for a specific defect. For example, modifications of the Fontan operation, which was originally devised for patients with tricuspid atresia, are now being used to repair a variety of univentricular hearts, including hypoplastic left heart syndrome.^{[32] [33]} Initially, the wider application of the Fontan operation to include complex defects once considered inoperable was associated with a rise in morbidity and mortality. However, this trend has been reversed in recent years by several groups who have demonstrated improved outcome with the staging of the operation (superior cavopulmonary anastomosis, subsequent completion of the Fontan operation), the creation of a fenestration between the right and left atrium at the time of the Fontan operation and the use of modified ultrafiltration.^[34] The communication allows for right-to-left shunting, thereby preserving cardiac output at lower systemic venous pressure in the early postoperative period. When necessary, once the patient has convalesced from the acute postoperative changes, the fenestration can be closed at the bedside with a snare placed at the time of the operation or in the catheterization laboratory with a clamshell device. In a substantial proportion of cases, these fenestrations close spontaneously without further intervention.

Ingenuity and innovation such as demonstrated with the difficult Fontan patient have permitted continued improvements in survival for all patients with congenital heart disease. As incisions in the myocardium become smaller and sutures more precisely placed, and as improvements in surgical techniques continue to evolve, the complications of ventricular dysfunction, arrhythmias, and residual obstruction should decline, contributing to improved patient quality of life.

One final difference unique to congenital heart surgery that has a major impact on anesthetic management relates to the type of cardiopulmonary support. Because of the complexity of repair in small patients, surgery often requires significant alterations in the bypass techniques, such as the use of deep hypothermic CPB at temperatures of 18°C and total circulatory arrest.^{[35] [36]} Many operations are undertaken in this setting of extreme biologic conditions of temperature and perfusion. Current methods of CPB management in neonates, infants, and children involve extensive alterations in temperature, hemodilution, systemic perfusion pressure, and flow. Despite widespread use of these techniques during bypass, their physiologic effects on major organ system function are just beginning to be understood. These effects are discussed in subsequent sections.

In summary, there are unique features that need to be considered when caring for children with congenital heart disease who are undergoing pediatric cardiac surgery. These features include the patient's growth and development, the developing cardiovascular system of the young, the pathophysiology of congenital heart disease, the surgical procedures, and the CPB techniques. A basic understanding of these differences coupled with the fundamental knowledge of adult and pediatric cardiac anesthesia principles underlie the approach to the perioperative management of these patients.