Routine neonatal oximetry screening for critical congenital heart defects in British Columbia: It’s time!

Keyvan Hadad, MD, MHSc, FRCPC (biography and disclosures)

What is the question?

Congenital heart defects account for more newborn deaths than any other type of congenital defect, representing up to 40% of all deaths from congenital defects and 3–7·5% of all infant deaths.¹ Cardiac surgery has significantly improved survival, especially for neonates with potentially life-threatening critical disorders. Antenatal ultrasonography and meticulous newborn examination have led to improvements in early diagnosis but have a fairly low detection rate in newborns with critical congenital heart defects (CCHD) defects.² The incidence of CCHD is approximately 1.8 per 1000 babies born every year (this compares to 1 per 4000 for congenital hypothyroidism or 1 in 15000 for PKU). If defects are not detected prior to hospital discharge, there is a risk of circulatory collapse, which can result in shock and acidosis with a substantial adverse effect on prognosis. Surgical morbidity and mortality increase significantly with poor pre-operative clinical status.³

Screening all newborns at hospital discharge with pulse oximetry has been suggested as a method to improve detection rates for CCHD. Many CCHD have a degree of hypoxemia in the immediate neonatal period that would not necessarily produce visible cyanosis and therefore might not be detected clinically.

Pulse oximetry screening for CCHD in all neonates has already been legislated in a number of European countries and in many states in the US.⁴

What is the evidence

Over a dozen good quality prospective studies have been conducted to study this question with well-defined populations, tests, and reference standards in various newborn care settings.⁵-⁶

Pooled data of over 229000 neonates has shown that pulse oximetry is a highly specific test (99.9%) for detection of CCHD in asymptomatic newborn babies with low false-positive rate (0.14%).⁷ The false-positive rate was significantly lower when the screening was done after 24 hours of birth rather than when it was done before 24 hours. The sensitivity of the test was moderate overall, 76.5% for the pooled data (range of 67.7-83.5%). There was no significant difference in sensitivity before or after 24 hours of life. In studies that used both preductal (right hand) and postductal (usually either foot) saturations, individual defects were detected which would not have been identified by postductal saturations alone.⁷

There are seven defects classified as CCHD that are shown to be most likely to be picked up by pulse oximetry. These lesions include hypoplastic left heart syndrome, transposition of the great arteries, pulmonary atresia with intact ventricular septum, tricuspid atresia, Tetralogy of Fallot, total anomalous pulmonary venous return, and truncus arteriosus.

The screening has not been shown to detect left to right shunt lesions but the measurement of peripheral perfusion index by newer generation pulse oximeters may eventually lead to improved pickup rates for critical left heart obstruction lesions.⁸

Practice tips

There is compelling evidence for the introduction of routine neonatal pulse oximetry as a screening method, resulting in significant improvement in the timely diagnosis of CCHD, superior to the present strategy of antenatal ultrasonography and physical examination alone.

The false positive rate is quite low, especially when done after 24 hours of birth. Newborns, classified as false positives for CCHD screening, are likely to have other potentially serious conditions, such as pulmonary or infectious diseases, and would need to be fully evaluated on their own merit.

Pulse oximetry is painless, readily available, and non-invasive. Nursing staff responsible for newborn care should have the prerequisite skill sets to conduct oximetry. If not, the education is routine.

A “Negative Screen” is achieved when oxygen saturations in the right hand and either foot are 95% or greater and the difference between the two readings is 3% or less.

If there is concern of the possibility of CCHD, a pediatrician will need to be consulted and further care, including possible transfer to a larger centre, will need to be initiated.

The cost of the screening program includes the fixed price of oximetry units and sensors, available already in most centres, and disposable wraps, pending the local institution’s infection control policy. Babies who test positive through the screening program will carry the economic cost of further care which is believed to be significantly offset by the heavy cost of the care of those babies presently missed.⁹

Newborn oximetry screening is an evidence-based program to improve the pickup of critical congenital heart disease, leading to improved outcome for such babies. In British Columbia, Interior Health and Island Health have led the way with the establishment of regional programs. It is time for the rest of the province to follow this lead.

References

1. Knowles R, Griebsch I, Dezateux C, Brown J, Bull C, Wren C. Newborn screening for congenital heart defects: a systematic review and cost-effectiveness analysis. Health Technol Assess 2005; 9: 1–152. (View)
2. Garne E, Stoll C, Clementi M, Euroscan Group. Evaluation of prenatal diagnosis of congenital heart diseases by ultrasound: experience from 20 European registries. Ultrasound Obstet Gynecol 2001; 17: 386–91. (View)
3. Brown KL, Ridout DA, Hoskote A, Verhulst L, Ricci M, Bull C. Delayed diagnosis of congenital heart disease worsens preoperative condition and outcome of surgery in neonates. Heart 2006; 92: 1298–1302. (View)
4. Kemper AR, Mahle WT, Martin GR, et al. Strategies for implementing screening for critical congenital heart disease. Pediatrics 2011; 128: e1259–67. (View)
5. Mahle W, Koppel R. Screening with pulse oximetry for congenital heart disease. Lancet 2011; 378: 749–50. (View with CPSBC or UBC)
6. Wren C, Richmond S, Donaldson L. Presentation of congenital heart disease in infancy: implications for routine examination. Arch Dis Fetal Neonatal Ed 1999; 80: F49–53. (Request from  CPSBC)
7. Thangaratinam S, Brown K, Zamora J, Khan K, Ewer A. Pulse oximetry screening for critical congenital heart defects in asymptomatic newborn babies: a systematic review and meta-analysis. Lancet 2012; 379:2459-64 (View with CPSBC)
8. Granelli A, Ostman I. Noninvasive peripheral perfusion index as a possible tool for screening for critical left heart obstruction. Acta Paediatr. 2007 Oct;96(10):1455-9 (Request from  CPSBC or view with UBC)
9. Roberts T, Barton P, August P. Pulse oximetry as a screening test for congenital heart defects in newborn infants: a cost-effectiveness analysis. Arch Dis Child. 2012 Mar;97(3):221-6 (Request from  CPSBC or view with UBC)

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