Pulse Oximetry Screening for Congenital Heart Disease

Pulse oximetry screening measures arterial oxygen saturation in the newborn to detect critical congenital heart disease. Saturation is measured in the right hand (pre-ductal) and in one foot (post-ductal). Differences between the two sites, and low readings, suggest a cardiac lesion that causes hypoxaemia.

The screen identifies infants who need echocardiography. It does not diagnose the lesion, and it misses some conditions that do not cause early hypoxaemia.

Usage. It is used as a universal screen after the first day of life, when the ductus arteriosus has begun to change and post-ductal saturation is more informative.

Indications. Universal newborn screening, and screening of infants with risk factors for congenital heart disease.

Preparation and technique. The infant is screened at least 24 hours after birth, ideally when settled and warm. Probes are applied to the right hand and to one foot, and readings are taken once the waveform is stable. Readings are repeated when the trace is unstable.

Contraindications and precautions. Poor peripheral perfusion, cold extremities, excessive movement and nail polish can prevent a valid reading. Infants in severe illness are assessed clinically first.

Interpretation.

• A pass is a saturation of 95% or more in the right hand and foot, with a difference of 3 percentage points or less between sites.
• A refer result is a saturation under the threshold at either site, or a difference over the threshold between sites.
• A refer result requires echocardiography, and the result is not interpreted as a diagnosis.

Causes of a refer result. Critical congenital heart disease, lung disease, sepsis, pulmonary hypertension of the newborn, and technical error.

Critical values and findings needing immediate action.

• A saturation well under the threshold in an infant who is unwell requires immediate medical assessment and echocardiography.
• A refer result with cyanosis or respiratory distress requires urgent transfer to a neonatal service.

Limitations and artefacts. Screening misses some lesions, including those that do not cause early hypoxaemia and those that present later. Early screening before 24 hours can miss post-ductal differences. Warm or cold conditions alter readings.

Follow up tests. Echocardiography for any refer result, repeat oximetry after an interval for borderline results, and blood gas analysis in unwell infants.

Special groups. Preterm and neonatal intensive care infants have different baselines and are assessed in the context of their illness. Lung disease can cause a refer result without heart disease.