Extracorporeal Membrane Oxygenation After Congenital Heart Surgery: Does One Database Fit All?*

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With the increasing complexity of congenital cardiac surgical repairs, the use of extracorporeal membrane oxygenation (ECMO) support in the immediate postoperative period remains common. Indications for initiation of ECMO in cardiac patients include failure to wean from cardiopulmonary bypass, perioperative circulatory collapse, pulmonary hypertension, and in some centers routinely after surgical repair of highly complex surgical lesions such as hypoplastic left heart syndrome and its variants (1–3). However, the indications, timing, and threshold for utilization of ECMO after congenital heart surgery (CHS) vary between institutions. Due to this variability, it has been difficult to quantify impact of ECMO utilization on overall outcomes of cardiac surgery. The measurement of improvement in patient outcomes is dependent on accurate assessments of its implementation, performance, and the ability to distinguish truly high-performing centers. Center specific performance in CHS has been evaluated using a variety of clinical databases, clinical registries using comprehensive coding and classification systems, and administrative databases containing information collected mainly for hospital billing purposes (4, 5).
The Extracorporeal Life Support Organization (ELSO) registry remains the largest international database incorporating roughly 310 centers. In the most recent ELSO report (2016), the survival rate for neonates after cardiac ECLS was shown to be roughly 62%, compared with respiratory ECMO survival of 84% (6). Although this database contains detailed standardized information regarding perisupport period one of its major limitations is lack of data on preoperative risk factors, operative characteristics, individual congenital heart lesions, and interhospital variation. Most importantly, it also fails to capture patients who were considered for ECMO support but ultimately did not receive this therapy, limiting our ability to study the true benefit of ECMO.
The Society of Thoracic Surgeons Congenital Heart Surgery Database (STS-CHSD) collects perioperative data on all children undergoing cardiac surgical repair at more than 100 North American centers. The perioperative data include information regarding the primary procedures of index cardiovascular operation of the admission which is analyzed individually and categorized using the International Pediatric and Congenital Cardiac Code risk stratification system (7). Mascio et al (8) used this database to describe the patterns of mechanical circulatory support (MCS) use and outcomes across STS-CHSD participating centers. They revealed that MCS (> 95% ECMO) was used in 2.4% cardiac operations at 80 centers with the greatest number used in those with single ventricle palliative procedures and complex biventricular repairs. More than half of those treated with MCS (53%) did not survive to hospital discharge with mortality reaching greater than 70% for the more complex operations and a significant variation in MCS rates between high- and low-volume hospitals. Although STS-CHSD captures detailed data on perioperative variables with excellent completion and agreement rates, it fails to incorporate the details regarding indication for MCS, omitting detailed information regarding timing of the initiation, type and duration of perioperative MCS as well as related complications.
In this issue of Pediatric Critical Care Medicine, Bratton et al (9) embark on yet another quest to shed more light on ECMO support in the setting of CHS. In their retrospective cross-sectional study, they choose the Pediatric Health Information System (PHIS) database. The PHIS database includes administrative and billing data from more than 40 U.S. children’s hospitals, providing generalized reflection of surgical experience in the country. Diagnoses and procedures for all children hospitalized at these institutions are coded by billing personnel using International Classification of Diseases, 9th Edition (ICD-9) codes. Using the combination of ICD-9 diagnosis and procedure codes, one is able to identify and group surgical mortality risk using the Risk Adjustment in CHS (RACHS)-1 system (10).

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