Blood samples from Paediatric CVCs

Submitted by Paula Wallis, IVNNZ Inc. Educator 2003 - 2005. Orginally printed in IVNNZ Inc. Newsletter

Central venous catheters in paediatrics allow for the administration of fluid and medications and now more commonly as an alternative to venipuncture. As with all central venous catheters, blood sampling carries the increased risk of catheter occlusion and so this has been where manufactures of central venous catheters have not always supported the practice of blood sampling from these lines (Knue et al, 2005).

Knue et al (2005) completed a study of 204 children with 3 French PICC’s insitu and found that it was safe and effective to use this size catheter for blood sampling. They did mention that there was a higher occlusion rate with children who had blood samples obtained from their 3 French PICC however, concluded that this was not statistically significant.

So what are some of the considerations? Every time blood is drawn off a PICC line there is the risk of occlusion therefore, care needs to be taken to ensure that an adequate push pause flush is performed following the technique – in younger children and babies double the amount of the catheter lumen and for older children 10-20 mls is sufficient – this is of course dependent on the child’s height and weight and your institutional policies.

Other considerations that need to be considered are:

• IV infusions should be stopped prior to blood sampling for at least 1 minute
• Anticoagulant therapy should be stopped for 5 minutes prior to sampling – it should be   documented on the laboratory form that the patient is on anticoagulant therapy and how long  infusion stopped prior to sample being taken
• A discard sample should always be taken – once again if the patient is on anticoagulant  therapy more discard blood is required.
• It should always be documented on the laboratory form that the sample was taken from a  PICC line – studies have shown that the catheter material can alter blood sample results)
• Amount of blood to take – if unsure always check with your institutions laboratory – drawing too much blood off a child can cause iatrogenic anaemia – weight and height should once again be taken into consideration and having a knowledge of paediatric circulating blood volumes – the amount of blood drawn should be documented on the fluid balance chart
• Order of draw of blood samples – on the BD website – www.bd.com – there is a very good educational resource that informs you on what order to take the blood samples – this does matter!

Blood sampling from a central venous catheter should always be a credentialed procedure and should always follow your institutional policies and guidelines.
Blood sampling from a paediatric central venous catheter can help to reduce unnecessary venipuncture attempts that are associated with pain and anxiety and if performed correctly can be very successful. However, if performed incorrectly and without considering the above points can lead to increased central venous catheter occlusions and possibly inaccurate blood results as well as possible harm to the patient.

References

Frey,A.M, Drawing Blood samples from vascular access devices. Journal of Infusion Nursing; 26(5). September/October 2003: 285-293.
Infusion Nurses Society. Policies and procedures for Infusion Nursing. Second edition. 2002. 142 -143.

Knue, M. Doellman, D. Rabin, K. Jacobs, B.R. The Efficacy and Safety of Blood Sampling through Peripherally Inserted Central Devices in Children. Journal of Infusion Nursing; 28(1). January/February 2005: 30-35.
http://www.bd.com/vacutainer/pdfs/microtainer_tubes_orderofdraw_pocketcard_VS5845.pdf
http://www.bd.com/vacutainer/labnotes/pdf/Volume11Number1_VS7105.pdf