Paediatrics: Capillary blood sampling

Capillary blood sampling

Capillary blood sampling is used when small volumes of blood are neces-sary for analysis, e.g. FBC, blood gas, blood glucose. An automated device to pierce the skin is preferred over a lancet, as it causes less pain and punctures to a predetermined depth, thereby reducing the risk of underly-ing bone damage or infection.

Equipment

•   Alcohol impregnated swab.

•   Automated device or sterile lancet.

•   Appropriate sample bottles or capillary tubes.

•   Cotton wool or gauze swab.

Site

•   Plantar heel surface outside the medial and lateral limits of calcaneous bone in the young infant (Fig. 7.1).

•   Finger site in the older child.

Procedure

•   Warm the heel or finger.

•   In the case of foot, hold dorsiflexed.

•   Clean with an alcohol impregnated swab.

•   Gently massage area to improve blood flow and use your hand as a tourniquet.

•   Puncture skin with an automated device or sterile lancet.

•   ‘Scoop’ droplets of blood into an appropriate sample container or on to blood glucose-measuring strip. Note that excessive squeezing leads to falsely high serum potassium and haematocrit levels, and bruising.

•   Once sample has been collected stop any residual bleeding by local pressure with a cotton wool ball or gauze swab.