Children may have blood tests to help their healthcare provider evaluate their illness,
or to help keep track of their health after surgery.
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Complete blood count. This test measures the size, number, and maturity of different blood cells in the
blood. These are red blood cells, white blood cells, and platelets. Red blood cells
are important because they carry oxygen through the blood to the organs and cells
of the body. If you don't have enough red blood cells to carry the oxygen your body
needs, you may have anemia. White blood cells multiply when your child has inflammation
or an infection. Platelets help the blood clot. This helps stop bleeding from cut,
for example.
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Electrolytes. This test measures minerals in the bloods that are needed for the organ to work as
they should. Minerals include sodium, potassium, calcium, and magnesium. If a child
is taking water pills (diuretics), the medicine may cause electrolyte problems. Potassium
levels are especially important for healthy heart function.
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BNP. This test measures how much BNP hormone is in your child’s blood. BNP stands for
B-type natriuretic peptide. The heart’s pumping chambers (ventricles) make BNP. When
the heart is working well, there are low levels of BNP in the blood. When the heart
has to pump harder than usual, BNP levels are higher. BNP testing can tell if your
child has a problem with the heart or lungs.
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Total protein and albumin. These tests can help evaluate a child's nutrition and how well the liver is working.
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Prothrombin time (PT), partial thromboplastin time (PTT), and international normalized
ratio (INR). These look at how well the blood clots. Sometimes these tests are done to check
how well blood-thinning medicines (anticoagulants) are working. Or to see if there
is a risk of bleeding. These medicines are taken for various heart problems.
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Blood gas. A blood sample is taken from an artery to measure the amounts of oxygen and carbon
dioxide in the blood. The acidity (pH) of the blood is also measured. This test may
be done after a pulse oximetry. This is a painless, noninvasive test. It measures
the amount of oxygen in the blood through a small, infrared sensor placed on a child's
finger, toe, or earlobe.
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Genetic blood tests. These tests may be used to find chromosome problems linked to congenital heart defects.
These lab tests must be sent to a special genetics lab. It often takes days or weeks
before results are available.
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Troponin. Cardiac troponin I and troponin T are sensitive biomarkers. Troponin is found in
cells in your heart muscle. When these cells are injured, they can release troponin
and other substances into the blood. Higher troponin levels may mean there's a problem
with the heart.