A. What are the vital signs? Respiratory rate and respiratory effort are important indicators of the severity of illness in an infant. Increased respiratory rate with retractions, nasal flaring, and
grunting indicates significant respiratory disease. An infant who has cyanosis with increased respiratory rate but no increased effort (so-called comfortable tachypnea) is more likely to have congenital heart disease. Oxygen saturation, obtained by peripheral pulse oximetry, may help establish a differential diagnosis, especially if saturations are different in upper versus lower extremities (differential saturations). Significant tachycardia or bradycardia is an indicator of severe physiologic derangement requiring immediate attention.
B. How easily does air move into and out of lungs? Wheezing or stridor indicates airway obstruction. Poor air movement, prolonged expiration, or other lung sounds (rales, wheezes, rhonchi) assist in the differential diagnosis. Poor aeration on only one side may indicate pneumothorax or pneumonia.
C. Is there a murmur? A murmur is present in some types of cyan-otic congenital heart disease (eg, significant right ventricular outflow obstruction seen in critical pulmonary stenosis or tetralogy of Fallot) but may not be present in others (eg, transposition of the great arteries, atrioventricular canal defect, total anomalous pulmonary venous connection, and hypoplastic left heart syndrome). An infant with a hypercyanotic episode (so-called tet spell) may not have a murmur if the episode is severe, because there is not enough pulmonary blood flow to create a murmur.
D. Is cyanosis peripheral, central, or differential? Cyanosis that affects skin and lips but spares oral mucosa, tongue, and conjunctivae is termed peripheral cyanosis. It occurs in the presence of normal arterial saturation. Cyanosis that affects mucosa of the mouth and conjunctivae in addition to skin and lips is termed central cyanosis and suggests arterial desaturation or abnormal hemoglobin. Differential cyanosis, blueness of the upper or lower portion of the body, only, is an indicator of heart disease. Cyanosis of the lower extremities is seen in infants with critical aortic coarc-tation or interrupted aortic arch. The lower portion of the body is supplied by systemic venous blood coursing right to left across a patent ductus arteriosus (PDA). This differential cyanosis may also be seen in a newborn with persistent pulmonary hypertension. Transposition of the great arteries with PDA may produce differential cyanosis of the upper extremities (oxygenated blood courses right to left across ductus arteriosus, supplying the lower body).
E. When does cyanosis occur? Cyanosis that occurs intermittently is associated with apnea, cold exposure (acrocyanosis), or intermittent airway obstruction. Intermittent cyanosis that occurs with feeding is seen with choanal atresia, esophageal atresia (especially with coughing, sputtering), or severe gastroesophageal reflux. Cyanosis as a result of cardiac disease, respiratory disease, or abnormal hemoglobin usually is present continuously.
F. How old is patient? Differential diagnosis for a child or an adolescent with cyanosis can be quite different from that of a newborn. In-depth prenatal and birth history and past medical history may supply important information for diagnosis. For example, patients presenting outside of infancy generally do not have a cardiac cause for cyanosis without a known history of cardiac disease or illness predisposing them to cardiac disease.
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