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Collect blood samples when only a small amount of blood is needed or when there is difficulty obtaining samples by venipuncture or other source. Common studies include complete blood count (CBC), chemistries, liver function tests, sickle cell anemia, thyroid, bilirubin levels, toxicology/drug levels, bedside glucose monitoring, and newborn metabolic screening. Coagulation studies, chromosomal analyses, immunoglobulin titers, and some other, more sophisticated tests cannot be done on capillary sampling.
Capillary blood gas determination gives satisfactory pH and Pco2, but not Po2.
Blood cultures when venous access or other access is not possible. Sterile technique is required but heelstick is not the preferred method.
Newborn metabolic screen is ideally performed in the first 48–72 hours of life (however, can be done after 24 hours). It should be done before a transfusion and antibiotic therapy and ideally after receiving breast milk or formula to ensure accurate testing. See Chapter 15.
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Automated self-shielding lancets are preferred in neonates (Table 33–1); sterile manual lancets are not recommended but may be used in some units if automated lancets are not available (sizes: 2 mm for <1500 g and 4 mm for >1500 g). Capillary tube (for rapid hematocrit and bilirubin tests) or larger BD Microtainer™ collection tubes (if more blood is needed [eg, for chemistry determinations]), filter paper card for newborn screening (if appropriate), clay to seal the capillary tube, a warm washcloth or heel warming device (eg, a chemical activated packet), antiseptic solution, gloves, and a diaper.
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Automated self-shielding lancets are preferred in neonates because they are associated with fewer complications and decreased pain. Automated devices cause less hemolysis and less lab value error, ...