Collecting Blood Specimens
Management guidelines for students, interns and registrars on a variety of routine and emergency situations in our neonatal service at Tygerberg Children’s Hospital. Published in 2014.
Always document the source of specimens (capillary, arterial or venous) so that results can be compared. Use gloves. See special investigations (specimen tubes and volumes) for type of specimen tube and volumes required.
Capillary Blood
- Used for the collection of the following specimens:
- Urea, creatinine, electrolytes, calcium, albumin, bilirubin,glucose, CRP.
Procedure
Use gloves. Warm the heel of the foot in water (40°C) or move the foot with dorsi and plantar flexion in order to increase blood flow.
Clean the area (heel) with an alcohol swab and allow drying. Smear a little Vaseline or paraffin wax on the heel to limit blood smearing. Hold the foot in dorsiflexion with the finger and thumb around the heel.
Use a lancet or stylet (Autolet) to prick the heel on the lateral or medial aspect (see sketch) and not over the calcaneous.
Complications include necrotising chondritis, especially in babies < 1kg.
The blood is collected directly into an Eppendorff tube(s) or a capillary tube and then transferred directly into the Eppendorff tube. Fill the tube. The following volume Eppendorff tubes (with gel) are required:
1 tube: Required if Hct < 50% for determination of urea, electrolytes, calcium, albumin and bilirubin.
2 tubes: If Hct > 50% and the above investigations are required or for “liver function” determination.
CRP’s are done on 1 tube (without gel).
Precautions
Do not squeeze the heel. This results in falsely elevated potassium and Hct values. Always examine the heel for previous repeated punctures.