Blood collection in newborns and infants is an important procedure for monitoring their health and diagnosing potential medical conditions. While the idea of a blood draw can be concerning for parents, established and safe methods are routinely employed. These procedures are designed to be as gentle and efficient as possible, prioritizing the well-being of the infant. Healthcare providers utilize specific techniques to gather the necessary samples for various screenings and tests.
The Heel Stick: The Standard Method
The heel stick, also known as a heel prick or capillary blood sampling, is the routine method for obtaining blood samples from newborns and infants. This minimally invasive technique involves making a small puncture on the baby’s heel to collect a small volume of blood. The collected blood is typically used for various screening tests, including mandated newborn screenings.
Why the Heel Stick is Preferred for Infants
The heel stick is preferred for infants due to several physiological and practical benefits, making it a safe and effective method. Infant heels have a rich supply of capillaries located close to the skin’s surface, making them easily accessible for blood collection. This accessibility means a smaller, less invasive puncture can yield a sufficient sample.
The procedure is minimally invasive, which results in a lower risk of complications compared to drawing blood from a vein or artery. Capillary blood sampling can also help preserve venous access for future intravenous lines, which is particularly useful for infants who may require frequent blood draws. The heel stick provides enough blood for common newborn screening tests, such as those for metabolic disorders, bilirubin levels, and complete blood counts, including those mandated by newborn screening programs for conditions like phenylketonuria (PKU), congenital hypothyroidism, and sickle cell disease. This method is generally less traumatic for the infant and easier to perform than venipuncture on tiny, fragile veins.
Preparing for and Performing a Heel Stick
Before a heel stick, healthcare professionals take steps to prepare the infant and minimize discomfort. The baby’s heel is often warmed, which helps increase blood flow to the capillaries, making collection easier and quicker. Positioning the baby comfortably, often swaddled or held by a parent, also contributes to a smoother process.
The procedure itself involves a quick puncture, typically performed with an automatic lancet designed to control the depth of the puncture. After the puncture, a large droplet of blood forms, which is then gently collected into a capillary tube or onto a specialized filter paper. Gentle, intermittent pressure is applied to the heel to facilitate blood flow, avoiding excessive squeezing which can damage blood cells and affect test results.
To minimize discomfort during and after the heel stick, several comfort measures are often employed. Skin-to-skin contact with a parent, swaddling, and the use of a pacifier can provide comfort and distraction for the baby. Oral sucrose, a sweet solution, is also frequently given to infants before or during the procedure, as it has been shown to reduce pain perception. After the blood collection, gentle pressure is applied to the puncture site with cotton or gauze to stop any bleeding, and a small bandage may be placed. Parents are encouraged to observe the site for any prolonged redness or bruising, although these typically resolve within a few days.
When Other Collection Methods Are Necessary
While the heel stick is the preferred method for routine newborn blood collection, other methods may be used in specific circumstances. Venipuncture, which involves drawing blood from a vein, is typically performed when larger blood volumes are required for certain diagnostic tests, or if a heel stick is unsuccessful or not suitable. This method usually involves drawing blood from a vein in the arm or hand, and it can be more challenging in infants due to their small, fragile veins.
Arterial stick procedures are rarely performed for routine blood collection in newborns. This method is usually reserved for specific situations in critical care settings, such as obtaining blood for accurate blood gas analysis, which measures oxygen and carbon dioxide levels in the blood. Umbilical cord blood collection is another method, but it is done at birth, primarily for tests related to the birth process, genetic conditions, or for cord blood banking, rather than for ongoing infant care after discharge.