Heel stick or heel lance is a minimally invasive method to obtain blood sample. It withdraws capillary blood samples and is used especially in newborn screens and glucose levels.
It can be used for routine tests too as lab techniques now require smaller sample volumes. Heel sticks can be used when venous access cannot be made or veins need to be preserved for the future especially in infants requiring multiple or frequent blood sampling.
Scope of Heel Stick
Heel stick withdraws capillary blood which can be used when a small sample would suffice and another acceptable source of blood.
The sample can be used to perform a biochemistry test, CBC, newborn screening, bedside glucose monitoring, and blood gas analysis. Coagulation studies cannot be performed with capillary samples.
Tests like chromosomal analyses and immunoglobulins and other titers should not be performed.
Blood cultures require absolute sterility and should not, therefore, be done with a heel stick.
Heel stick should not be done if there is any injury, infection, or edema present in the sampling area.
Procedure of Heel Stick
The materials required for a heel stick include the following:
- A heel-warming device if required
- Antiseptic solution
- A heel-lancing device sized appropriately for the infant’s weight [if not available simple lancet or hypodermic needle is used]
- 0.65 mm for infants weighing 1 kg or less
- 0.85 mm
- small-for-gestational-age infants
- Premature infants > 1 kg
- 1 mm for infants aged 6 months or younger
- A towel or pad to cover bed linens
- An appropriate blood collecting apparatus
- A bandage or gauze to dress the wound after the procedure
No local anesthesia is used as it can interfere with sample quality.
Oral sucrose, ambient light, and noise reduction, and swaddling are used in lieu of anesthesia.
The sample is most easily obtained with the patient in supine position but can be taken in a prone or sitting position and flexing the leg.
Proper site selection (see the image ) is important for minimizing pain and avoiding contact with the calcaneus.
The posterior pole of the heel should not be used for a heel stick, as the calcaneus here is in its most superficial.
Technique of Heel Stick Sampling
If heel warming is desired, apply a heel warmer though some studies mention no effects of heel warming.
With gloved hands, prepare the automated heel-lancing device.
Prepare the desired area for sampling.
Hold the feet in such a way that your thumb and index finger hold the heel while the other three fingers hold distal leg and ankle. Keep the foot in mild dorsiflexion.
Place the automated lancing device on the appropriate area on the side of the heel and activate it.
Apply mild pressure for oozing of the blood. Avoid excessive squeezing as it could lead to hemolysis of the sample and pain.
Wipe away the first drop of blood, and collect the sample using a capillary tube. Then transfer the blood to desired tubes.
If blood stops flowing, try to wipe away any clot that may have formed at the site
Release pressure to allow capillary refill, then reapply pressure to allow a blood drop to form again.
When sampling is complete, apply pressure to the incision site until bleeding stops. Apply gauze or a bandage.
In cases of neonatal screening, get the sample drops directly on to the prescribed filter test paper [see the first video below.]
Videos of Heel Stick Procedure
The following are two videos of a heel stick.
The first video is used lancet and supine position for screening. The blood is taken directly on the filter paper.
The second video uses a free needle to take the sample while the child is in the mother’s lap. The blood is collected in the capillaries. This uses a minimum of resources though.
Complications of Procedure
Though quite are, pain, infection, scarring, and piercing of the calcaneus are reported complications.
Inaccurate results have been reported due to hemolysis, trapping of air bubbles [ABG] and platelet clumping.