Paediatrics: Capillary blood sampling

2021-03-05 12:00 AM

Capillary blood sampling is used when small volumes of blood are necessary for analysis, e.g. FBC, blood gas, blood glucose.

Capillary blood sampling

Capillary blood sampling is used when small volumes of blood are necessary 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 calcaneus bone in the young infant (Fig. 7.1).
  • Finger site in the older child.

Procedure

  • Warm the heel or finger.
  • In the case of a foot, hold dorsiflexed.
  • Clean with an alcohol impregnated swab.
  • Gently massage the 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 the sample has been collected stop any residual bleeding by local pressure with a cotton wool ball or gauze swab.