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Cyanotic congenital heart disease Pt01 ("The Cardiac Blues")

Jeffrey Gossett MD and Andi Marmor, MD
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26:06

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You’re called to the nursery to evaluate a baby with low oxygen saturations who is looking blue. How do you know if it’s cardiac or pulmonary and what can you do to distinguish the two? What steps do you need to take to stabilize this baby?  Luckily, Andi sits down with UCSF pediatric cardiologist Jeff Gossett to discuss cyanotic congenital heart disease and answer these questions and so many more.

  • When evaluating a newborn for possible cyanosis, it is important to determine if the baby appears gray or blue. 
    • A neonate that appears gray is under perfused. This can be due to inadequate cardiac output from a cardiac cause or from sepsis. These infants often have cool or mottled extremities, delayed cap refill and weak pulses. 
    • A blue infant has central cyanosis which is often noted when looking at the mucous membrane and/or nail beds. These infants have abnormally low pulse oximetry reading.
  • Cyanosis is difficult to see as it often does not become apparent until the infant has at least 4 grams per deciliter of deoxygenated hemoglobin (<80 percent saturation). In darkly pigmented infants, cyanosis can be especially difficult to appreciate.
  • Screening for critical congenital heart disease (CHD) should be done at 24 hours of life or as late as possible if early discharge is planned. Screening within the first 24 hours of life is not as specific as later screening because hypoxemia commonly occurs during the transition from fetal circulation to extrauterine circulation. 
  • Screening is done by measuring the oxygen saturation in the right hand (preductal) and either foot (postductal). 
  • The CHD screen is positive if any one of the following occur:
    • The oxygen saturation measurement is < 90 percent in either extremity
    • The oxygen saturation measurement is between 90 to 94 percent in both upper and lower extremities on three measurements, each separated by one hour
    • There is a difference >3 percent in the oxygen saturation measurement between the upper and lower extremities on three measurements, each separated by one hour
  • There are several non-cardiac etiologies for cyanosis in a newborn including:
    • pulmonary causes (such as from meconium aspiration, pulmonary hypertension) 
    • neurologic causes (like apnea).
  • Infants that are cyanotic secondary to a respiratory pathology typically have signs of respiratory distress including tachypnea and retraction in addition to possibly having a history of meconium aspiration or prematurity. 
  • The hyperoxia test can be used to help distinguish cardiac from pulmonary causes of cyanosis. 
  • The hyperoxia test is performed by measuring the partial pressure of oxygen (PaO2) in the right radial artery (preductal) before and after the patient breathes 100 percent oxygen concentration for 5 to 10 minutes. An increase in the PaO2 to a level >150 mmHg during the hyperoxia test suggests pulmonary disease.
  • Differential cyanosis is defined as a difference in oxygen saturation of at least 5% between the arms and legs associated with congenital heart disease or persistent pulmonary hypertension of the newborn.

Editor’s Note: Reverse differential cyanosis (upper extremity oxygen saturation less than lower extremity oxygen saturation) is rare and usually seen with D-transposition of the great arteries.

  • Four extremity blood pressure measurements are also helpful and can aid in the diagnosis of coarctation, a condition in which the blood pressures are lower in the legs (normally, we see slightly higher blood pressures in the lower extremities). 
  • Absence of a murmur does not rule out cardiac disease. Some of the most severe CHD, like hypoplastic left heart syndrome, may not have a murmur as there is nothing obstructing flow within the heart. 
  • A chest radiograph is helpful in differentiating between cardiac and pulmonary disorders presenting with cyanosis. Look at the heart shape and size, pulmonary markings, as well as the location of the aortic arch. 
  • An EKG can also be used to help distinguish a cardiac from a noncardiac process especially if it is grossly abnormal.

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August 2020 Peds RAP Written Summary 460 KB - PDF

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