Congenital Heart Disease and Anesthesia-Related Cardiac Arrest

In this issue of Anesthesia & Analgesia, Ramamoorthy et al.1 report results from the Pediatric Perioperative Cardiac Arrest (POCA) Registry over an 11-year period from 1994 to 2005. The primary goal of this analysis was to compare reports of anesthesia-related cardiac arrest (CA) in children with underlying heart disease (HD) with those who did not have a preexisting cardiac condition. In summary, the authors found that 34% of reported CAs occurred in patients with congenital or acquired HD, more than half of whom (54%) were undergoing noncardiac procedures in the general operating room (OR). The most common cardiac diagnosis category comprised anatomic constellations resulting in a single ventricle. The overall mortality after CA was higher in children with HD (33% vs 23% in patients without HD), although this difference disappeared when corrected for ASA physical status. Before expounding on the implications of this study, it is important to understand the limitations of the data, as the authors acknowledge. The POCA Registry is comprised of voluntary reports from a varying number (58–79) of institutions, 72% of which are university-affiliated hospitals. The reports are anonymous, not independently validated for completeness and accuracy, and no denominator data are available for comparative statistics. In addition, given this collection method, it is almost certain that the numerator reflects underreporting and perhaps even disproportionate reporting of patients with or without HD. The authors also appropriately question whether data derived largely from university-affiliated children's hospitals can be extrapolated across the vast range of settings in which children may undergo procedures. Despite all these stipulations, this study does make an important contribution to our understanding of the unique vulnerability of children with congenital HD in the perioperative setting. Taken in conjunction with prior studies on this topic, the following 3 important questions emerge. 1. Are Pediatric HD Patients at Greater Risk for CA in the Noncardiac Procedure Setting Compared with Patients without HD? Although the limitations of the POCA study do not permit an indisputable answer, there is support for this inference. Although the authors suggest that the larger number of CA reports emanating from the general OR may reflect a greater number of procedures performed on patients with HD in that setting, other data do not support that hypothesis. At the Children's Hospital of Philadelphia, only 18% of the procedures that children with HD undergo occur in the general ORs, and if other POCA Registry institutions have a similar distribution in this population, the fact that 54% of CAs occur in this venue suggests greater risk. Moreover, HD patients are only 2.3% of the general OR case volume at Children's Hospital of Philadelphia. In a large study of 191,261 noncardiac pediatric operations over 4 years in the University Hospital Consortium, Baum et al.2 reported that 3.1% had a diagnosis of congenital HD. The POCA Registry reveals that 22% of the reported CAs in general ORs are patients with HD, representing a disproportionate share in relation to their prevalence. This figure coincides with the findings from a comprehensive quality assurance database at the Mayo Clinic that captured 92,881 pediatric anesthetic cases over 17 years.3 Children with HD accounted for 56% of the reported CAs in both cardiac and noncardiac operations, although most were not considered anesthesia related. In the general OR, 27% of the CA patients had HD. Thus, there is rather compelling data that children with HD face greater risk of CA in the general OR setting compared with those without HD. Although there is some suggestion that HD patients confront greater risk of anesthesia-related CA in the general OR than the cardiac OR,3 that comparison requires assumptions about case classification and reporting that may not be appropriate. 2. Is the Risk in the General OR Related to Selection Bias, the Nature of the Procedures Performed, or the Anesthetic Care Provided? The underlying mechanisms for CA in children with HD are most often deterioration in cardiac performance as a consequence of insufficient coronary oxygen delivery or primary myocardial disease. The former can occur in malformations such as single-ventricle variants with a systemic to pulmonary shunt or truncus arteriosus where direct connection to the pulmonary vasculature results in diastolic runoff and diminished coronary perfusion. Alternatively, left ventricular outflow obstruction will result in myocardial hypertrophy resulting in greater sensitivity to hemodynamic changes that jeopardize coronary perfusion pressure. The distribution of HD among CA reports seems to support these mechanisms in the current series as well as other reports.1,4 Given the types of surgical interventions reported, the young age of the CA patients (38% ≤6 months) and the distribution of HD, one would suspect that this a particularly vulnerable patient population with HD predisposing to CA or other significant comorbidities that require relatively straightforward procedures such as gastrostomy, tracheostomy, or central venous access for long-term support. For the high-risk HD patient undergoing relatively minor interventions, whether this added vulnerability is related to inexperience with the nuances of the HD pathophysiology or the faulty assumptions that minor interventions do not pose major risk remains a matter of speculation. When compared with the outcomes of anesthesia-related CA in a comparable series reported by Odegard et al.4 at Children's Hospital Boston with a team skilled in the management of HD, the outcome differences are striking. Although methodological constraints preclude comparisons of CA rates, the Boston series had no mortality or significant morbidity in any of the anesthesia-related CA events in contradistinction to the mortality of 33% among POCA reports with HD, suggesting significantly better ability to promptly recognize deteriorating hemodynamics and rescue. 3. What are Viable Strategies to Mitigate the Risk for Pediatric HD Patients Undergoing Noncardiac Surgery Even accounting for significant underreporting, these are rare events, particularly from the perspective of a general pediatric anesthesiologist. Although one might hope that further education in the pitfalls of particular subpopulations of children with HD, as Ramamoorthy et al. strive to provide in their article, would be sufficient to equip all anesthesiologists to handle these rare events, this is not a realistic goal. As the medical and surgical advances in pediatric cardiac care succeed in generating an ever-increasingly fragile and complex group of survivors, we have seen highly skilled pediatric anesthesiologists grow increasingly estranged from the evolving anesthetic considerations in the pediatric HD population. Odegard et al.4 attribute their remarkable success in recognition and rescue of these patients to an experienced cadre of anesthesiologists who routinely manage infants with HD. The acquisition of this specific skill requires both focused training and ongoing professional commitment to the anesthetic management of children with HD. Averting CA and perhaps less extreme morbidity in children with HD during procedures in the general OR will require the experience, knowledge, and skills of a pediatric cardiac anesthesiologist. Whether those skills can be effectively imparted through a consultative relationship with a pediatric general anesthesiologist remains to be demonstrated. Such a model would need to provide ready access to advice throughout the procedure because 48% of the CA events occur during the maintenance phase of anesthesia care. At a minimum, one might devise an approach that enlists a cardiac subspecialist to oversee care for the subset of children with HD who pose the greatest risk, e.g., young infants with cardiovascular physiology predisposing them to coronary insufficiency, myocardial dysfunction, or marked pulmonary vascular disease. The model for training a pediatric cardiac anesthesiologist continues to evolve. Although the obvious need for such specialists exists in the context of therapeutic and diagnostic cardiac interventions, the POCA registry provides important evidence that these skills would benefit the care of pediatric HD patients in the general OR as well.