Pediatric emergency medicine trisk 2462 2462
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incidence of false positives, but within the first week. Importantly, the pulse
oximetry screen for CHD does not detect nonhypoxic heart disease (e.g.,
coarctation of the aorta, single ventricle, or double outlet right ventricle). The
American Academy of Pediatrics (AAP) and the CDC endorse screening for
critical CHD for all newborns ( Fig. 96.1 ). An infant who fails the initial screen
should be referred for an echocardiogram.
Hypoxia without respiratory distress, specifically without signs of grunting,
retractions, or accessory muscle use, is more common in cardiac disease than
respiratory disease. To better distinguish the etiology of hypoxemia, the clinician
can perform the hyperoxia test. To complete the test, the infant is given 100%
oxygen to breathe for 5 to 10 minutes. Serial pulse oximetry or arterial blood gas
measurements are obtained on room air and after the infant has breathed 100%
oxygen. If there is little to no increase in oxygenation, the hypoxia can be
attributed to extrapulmonary causes of right-to-left shunting. Extrapulmonary
right-to-left shunting occurs in persistent pulmonary hypertension and in cardiac
disease. To distinguish between the two, the clinician can perform the
hyperventilation test. In this circumstance, hyperventilating to a PaCO2 of 25 to
30 mm Hg in conjunction with 100% oxygen is more likely to elicit an increase in
PaO2 levels (typically >100 mm Hg) in persistent pulmonary hypertension of the
newborn (PPHN) due to relaxation of the pulmonary bed. Infants that continue to
have low PaO2 despite hyperoxia and hyperventilation are more likely to have a
fixed, intracardiac right-to-left shunting. In either circumstance, an
echocardiogram is the definitive study to differentiate between the two.
