ARTICLE |
| ABSTRACT |
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METHODS. This was a prospective cohort study of all liveborn infants with congenital diaphragmatic hernia who were cared for at tertiary referral centers belonging to the Congenital Diaphragmatic Hernia Study Group between 1995 and 2004. Factors thought to influence death included birth weight, Apgar scores, size of defect, and associated anomalies. Survival to hospital discharge, duration of mechanical ventilation, and length of hospital stay were evaluated as end points.
RESULTS. A total of 51 centers in 8 countries contributed data on 3062 liveborn infants. The overall survival rate was 69%. Five hundred thirty-eight (18%) patients did not undergo an operation and died. The defect size was the most significant factor that affected outcome; infants with a near absence of the diaphragm had a survival rate of 57% compared with infants having a primary repair with a survival rate of 95%. Infants without agenesis but who required a patch for repair had a survival rate of 79% compared with primary repair.
CONCLUSIONS. The size of the diaphragmatic defect seems to be the major factor influencing outcome in infants with congenital diaphragmatic hernia. It is likely that the defect size is a surrogate marker for the degree of pulmonary hypoplasia. Future research efforts should be directed to accurately quantitate the degree of pulmonary hypoplasia or defect size antenatally. Experimental therapies can then be targeted to prospectively identify high-risk patients who are more likely to benefit.
Key Words: congenital diaphragmatic hernia pulmonary hypoplasia neonatal surgery ECMO
Abbreviations: CDH—congenital diaphragmatic hernia ROC—receiver operating characteristic
Congenital diaphragmatic hernia (CDH) has a reported incidence of between 1 in 2500 and 1 in 4000 live births.1,2 With improvements in neonatal intensive care in the 1970s and 1980s, sicker patients survived to receive surgery in tertiary centers. During this time, mortality rates from CDH approximated 50%.3,4 Because of this persistently high mortality rate, newer techniques for the management of neonatal respiratory failure including extracorporeal membrane oxygenation, high-frequency oscillatory ventilation, exogenous surfactant, and inhaled nitric oxide were rapidly adopted. Attempts at CDH repair in utero were pioneered by Harrison and colleagues,5–7 but recent data have not shown a survival advantage for patients who undergo fetal surgery. Survival to hospital discharge seems to have improved over the past 2 decades, although some authors dispute these conclusions.8–11 The reported mortality rate in liveborn infants of 20% to 40% makes CDH responsible for >1% of the annual infant mortality in the United States.12 Furthermore, CDH ranks among the most costly of neonatal conditions. Metkus and colleagues13 reported that CDH had an estimated hospital cost of $250000 per case to hospital discharge, and an estimated yearly cost of $264000000 in the United States (1995 dollars) for the initial hospital care alone.
The relative rarity of the condition makes the conduct of well-designed clinical studies extremely difficult because no single center can accrue sufficient patients to reach meaningful conclusions. Therefore, the management of CDH has evolved based largely on retrospective reviews from centers with small numbers of patients and differing treatment algorithms. A number of factors complicate interpretation of these studies. Institutions differ with respect to referral patterns and hospital resources such that the case mix or range of severity in patients treated may not be comparable. Some centers do not offer surgical repair for certain infants that are deemed "nonsalvageable," whereas others do, and this bias can clearly affect comparisons of survival rates.14,15 Stratification systems that have been reported to date, however, have been unwieldy or have not proven useful when applied to other centers or other populations of infants.16,17
The purpose of this study was to evaluate hospital-based outcomes for infants with CDH from a large number of institutions and to determine clinical factors associated with a poor outcome.
| METHODS |
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4 consecutive years of data submission. The data from the registry forms were entered into a Microsoft (Redmond, WA) Access database and were cross-checked against the original forms. Patient demographics, birth information, Apgar scores, treatments received, and outcome were recorded. The Apgar scores were recoded into 3 categories (0–3, 4–6, and 7–10) for analysis. The size of the diaphragm defect was determined by the surgeon at the time of repair and coded as "agenesis" if the diaphragm or most of the diaphragm was absent (based on surgeons' reports and/or operative notes with findings of "absent or missing rim of diaphragm" or repair requiring "suturing the patch to the ribs anteriorly and posteriorly"). All patients with diaphragm agenesis required a patch to repair the defect. In those patients without agenesis, either the defect could be repaired primarily, or a patch was required to close the defect. A fourth group of patients never underwent operation; most had a combination of either severe other anomalies or were thought to have fatal pulmonary hypoplasia. Central or bilateral diaphragmatic defects comprise a rare variant with a very high mortality; patients with these defects were not included in the analysis.
Significant associated anomalies, including chromosomal anomalies, syndromes, and complex congenital heart disease, were evaluated to see whether their presence with CDH affected outcomes. The most common chromosomal anomalies were trisomies 13, 18, and 21; the most common syndrome was Fryns syndrome. Complex congenital heart disease included hypoplastic left heart syndrome, coarctation of the aorta, and tetralogy of Fallot. An isolated ventricular septal defect or atrial septal defect was considered minor.
Statistical Analysis
Death before hospital discharge was the primary outcome variable. The length of stay in the hospital and duration of mechanical ventilation were secondary outcomes. Univariate logistic regressions were used to evaluate the associations between clinical variables and death before hospital discharge. Those variables associated with death are presented as unadjusted odds ratios and their 95% confidence intervals. The Wald test statistic was used to evaluate statistical significance. A P value of .05 was considered significant. Patients who did not undergo repair were not included in the analysis.
Multiple logistic regression models including the clinical variables evaluated (inborn status, birth weight, prenatal diagnosis, major cardiac anomalies, chromosomal anomalies, 5-minute Apgar score, and defect size) were calculated. Receiver operating characteristic (ROC) curves of these models were evaluated to determine how well they classified patients that died before discharge. The area under the ROC curve was used to summarize the classification accuracy of the logistic regression models. The classification accuracies of full (including all the clinical variables) and reduced models were contrasted to identify the minimal set of clinical variables predictive of death before discharge. Kruskal-Wallis rank order 1-way analyses of variance were used to compare outcomes among patients grouped by defect size for length of hospital stay and duration of mechanical ventilation. Analysis of the database was approved by the University of Texas Institutional Review Board. Participating centers filed a waiver of consent for data submission or signed a data use agreement for a limited data set. The analyses were conducted using the NCSS 2004 (NCSS, Kaysville, UT) statistical software package.
| RESULTS |
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Survival in the surgically repaired patients was 2100 (83%) of 2524. A number of factors were significantly associated with death in the surgically repaired patients by univariate analysis (Table 2). Younger gestational age and lower birth weight were highly correlated, and both were associated with worse outcomes. Other significant factors included inborn status, prenatal diagnosis, presence of cardiac and chromosomal anomalies, low Apgar score, and large defect size (either a patch repair or diaphragm agenesis).
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We examined the impact of defect size on length of hospitalization and duration of mechanical ventilation as well. In patients who underwent repair and survived to transfer or hospital discharge, the size of the hernia defect was strongly associated with duration of mechanical ventilation and length of hospital stay (Fig 1).
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| DISCUSSION |
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This analysis shows that the size of the diaphragm defect correlates well with mortality, as well as morbidity in liveborn infants with CDH. Patients with diaphragm agenesis have previously been reported to have a high mortality.21–26 Defect size is likely to be a marker for the degree of pulmonary hypoplasia. Animal models suggest that a large defect is associated with much smaller lungs. It is possible to modify the degree of lung hypoplasia in the lamb model by the size of the defect created. In transgenic mice and toxicology models, timing of the insult is a contributing factor in determining size of the defect and outcome.27
An important criticism of this study is the accurate determination of the size of the defect. Clearly, there is some overlap between the groups defined by defect size because there is not an absolute value that defines agenesis or a "large" defect. There are also variations in surgical practice that determine whether a patch is used. However, there is a clear trend to liberal use of a patch to repair the defect.12,28 Also, it is not possible to close the defect in a patient with agenesis or a very large defect without a patch of some kind. Similarly, the definition of agenesis is likely to vary between centers. Despite this limitation, there is a clear differentiation in outcome by defect size in this data set.
The CDH Registry was formed to allow collection and analysis of data on presentation, treatment, and outcome of CDH from a large number of centers. Registries have proven to be a good way of collecting data on rare conditions and of mitigating institutional bias in patient selection and treatment. As with any data from registries, there are caveats to their interpretation. The database is observational, and conclusions about therapies should be interpreted cautiously. The data are collected from institutions that differ significantly in their patient recruitment and selection. These differences are especially important when interpreting patients in the nonrepaired category because criteria for "nonsalvageable" patients vary between centers. Many infants with severe cardiac and chromosomal anomalies did not undergo repair making the true impact of these factors difficult to determine. Furthermore, these data only represent outcome to hospital transfer or discharge; both long-term survival and morbidity are likely to be worse.30–33 Nonetheless, these data do represent a significant collection of patients with an uncommon disease process.
| CONCLUSIONS |
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| ACKNOWLEDGMENTS |
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The centers that contributed to the CDH Registry were Arnold Palmer Hospital for Women and Children (Orlando, FL), Astrid Lindgren Children's Hospital (Stockholm, Sweden), Central Hospital Aichi Prefectural Colony (Kasugai Aichi, Japan), Children's Hospital at Carolinas Medical Center (Charlotte, NC), Children's Hospital Boston (Boston, MA), Children's Hospital of Akron (Akron, OH), Children's Hospital of Alabama (Birmingham, AL), Children's Hospital of Illinois (Peoria, IL), Children's Hospital of Los Angeles (Los Angeles, CA), Children's Hospital of Minneapolis (Minneapolis, MN), Children's Hospital of Oakland (Oakland, CA), Children's Hospital of Oklahoma (Oklahoma City, OK), Children's Hospital of Wisconsin (Milwaukee, WI), Cincinnati Children's Hospital Medical Center (Cincinnati, OH), Cleveland Clinic Foundation-Children's Hospital (Cleveland, OH), Columbus Children's Hospital, Columbus, OH), DeVos Children's Hospital (Grand Rapids, MI), Emory University (Atlanta, GA), Hershey Medical Center (Hershey, PA), James Whitcomb Riley Children's Hospital (Indianapolis, IN), Kosair Children's Hospital (Louisville, KY), Legacy Emanuel Children's Hospital (Portland, OR), Loma Linda University Children's Hospital (Loma Linda, CA), Lucile Salter Packard Children's Hospital (Palo Alto, CA), Mattel Children's Hospital at UCLA (Los Angeles, CA), Medical College of Georgia (Augusta, GA), Children's Memorial Hermann Hospital (Houston, TX), Miami Valley Hospital (Dayton, OH), National Center for Child Health and Development (Tokyo, Japan), Oespedale Pediatrico Bambino Gesu (Rome, Italy), Oespedale Riunite Bergamo (Bergamo, Italy), Osaka University Graduate School of Medicine (Osaka, Japan), Phoenix Children's Hospital (Phoenix, AZ), Rainbow Babies & Children's Hospital (Cleveland, OH), Royal Alexandra Hospital (Edmonton, Alberta, Canada), Royal Children's Hospital Parkville (Victoria, Australia), Royal Hospital for Sick Children (Glasgow, Yorkhill, Scotland), San Diego Children's Hospital (San Diego, CA), Santa Rosa Children's Hospital (San Antonio, TX), Shands Children's Hospital/University of Florida (Gainesville, FL), Sophia Children's Hospital (Rotterdam, Netherlands), St Francis Children's Hospital (Tulsa, OK), St Joseph's Hospital and Medical Center (Phoenix, AZ), Strong Children's Hospital (Rochester, NY), Sydney Children's Hospital (Randwick NWS, Australia), Hospital for Sick Children (Toronto, Ontario, Canada), University of Michigan Medical Center (Ann Arbor, MI), University of Nebraska Medical Center (Omaha, NE), University of Texas Medical Branch (Galveston, TX), University of Virginia Health System (Charlottesville, VA), and Vanderbilt Children's Hospital (Nashville, TN).
The Congenital Diaphragmatic Hernia Study Group writing committee is as follows: Kevin P. Lally, MD, MS (University of Texas Medical School and Children's Memorial Hermann Hospital), Pamela A. Lally, MD (University of Texas Medical School and Children's Memorial Hermann Hospital), Robert E. Lasky, PhD (University of Texas Medical School and Children's Memorial Hermann Hospital), Dick Tibboel, MD (Sophia Children's Hospital), Tom Jaksic, MD, PhD (Children's Hospital Boston), Jay M. Wilson, MD (Children's Hospital Boston), Bjorn Frenckner, MD (Astrid Lindgren Children's Hospital), Krista P. Van Meurs, MD (Stanford University School of Medicine and Lucile Packard Children's Hospital), Desmond J. Bohn, MD (Hospital for Sick Children), Carl F. Davis, MD (Royal Hospital for Sick Children), and Ronald B. Hirschl, MD (University of Michigan).
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Address correspondence to Kevin P. Lally, MD, MS, Department of Surgery, University of Texas Health Sciences Center, 6431 Fannin St, Suite 5.258, Houston, TX 77030. E-mail: kevin.p.lally{at}uth.tmc.edu
The authors have indicated they have no financial relationships relevant to this article to disclose.
* See "Acknowledgments" for complete listing of writing committee. ![]()
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