Procedure for blood sampling

NHS Ayrshire & Arran guidelines
NHS Ayrshire and Arran

Blood samples should never be taken from a CVAD that is designated for total parenteral nutrition (TPN) feeding, unless blood cultures are required. An aseptic technique must be adhered to when taking blood samples. A trolley should be set up in the same way as to do the dressing change and flushing the line with the required equipment.

Steps 1 to 13 for flushing the CVAD should be followed. Only step 5 & 9 should be omitted. Laboratory bloods should be taken at step 6 once the 5-10mls of stagnant blood has been removed and discarded (unless blood cultures required). The syringe with blood for blood sampling should be placed at the side of the sterile field.

Once the line care has been completed the syringe with the blood should gently agitated prior to transferring into the appropriate laboratory blood bottles over the sterile field at waist level. If blood is left to sit in the syringe for a few minutes the blood sediments therefore red cells drift down and plasma/platelets are left at the top. If the syringe is not gently agitated prior to transferring into the blood bottles there is a risk of either concentrated red cells (elevated haemoglobin and Haematocrit) or dilute plasma (reduced haemoglobin and Haematocrit) – so the full blood count result could be inaccurate.

Procedure for obtaining blood cultures from a CVAD

An aseptic technique must be adhered to when taking blood cultures. Blood cultures require to be taken peripherally and then from each lumen of the CVAD. For the peripheral blood cultures follow G083 Guideline for Obtaining Peripheral Blood Cultures in Adults (16 years and over)

It is important to emphasize that peripheral blood cultures must be taken prior to blood cultures from the CVAD.

The rationale for this is: If the CVAD blood cultures are taken first the CVAD will need to be flushed / locked and this will inoculate the organisms into the bloodstream. If the peripheral blood culture is then taken it will then contain more organisms than it should do, and this blunts the differential time to positivity that is recorded in the blood culture machine.

To diagnose a systemic CVAD infection, the CVAD blood culture and the peripheral blood culture should grow the same organism. The CVAD blood culture should become positive at least 2 hours faster (because of the biofilm inside the lumen) than the peripheral blood culture.

Take peripheral blood cultures first. For blood cultures from a CVAD, a trolley should be set up in the same way as to flush the CVAD.

Procedure:

Please note: if your hands are not socially clean and you need to wash your hands with soap and water (rather than alcohol gel), this must be carried out a minimum of 2 meters away from the working surface/dressing trolley and any CVAD equipment.

  1. Clean working surface/dressing trolley with detergent wipe and allow to dry completely for at least 30 seconds. Clean hands with alcohol gel as per the WHO5 moments for hand hygiene. Put on a plastic apron.
  2. Open dressing pack onto clean area and open the necessary equipment onto the dressing pack aseptically.
  3. Check sample bottles and equipment are not faulty and within expiry dates (Do not place these on the top of the trolley as these are not sterile, place these on the lower shelf of the trolley).
  4. Clean hands with alcohol gel as per the WHO 5 moments for hand hygiene and apply sterile gloves.
  5. Remove the curos port protector (oncology only). Decontaminate the needle free device with chlorhexidine gluconate BP 2% & isopropyl alcohol 70% wipe for 30 seconds and allow to dry completely for 30 seconds.
  6. Attach a Luer-Lok syringe and aspirate 20mls of blood (2 x 10ml Luer-Lok syringes), place the sample in the sterile container within the sterile pack ensuring it does not contaminate any other equipment. Remember when withdrawing blood from a CVAD without clamps (valved CVAD) gently pull back 1-2mls wait 2-5 seconds for the valve to open and blood to start gently flowing through, prior to aspirating the full amount.
  7. Flush with 10mls of 0.9% sodium chloride using a brisk push/pause action, closing the clamp on the last push to create positive pressure in the line.
  8. (If the Hickman or PICC line has a clamp) Attach syringe with Heparin Sodium solution into needle free device, open clamp and inject the solution with a brisk push/pause action closing the clamp as the last of the solution is inserted. Remove the syringe from the needle free device. Do not use heparin in central lines.
  9. Repeat this process for each lumen. Attach a new curos port protector to the end of each lumen (oncology only).
  10. The tops of media bottles are clean but not sterile and should be wiped with 70% isopropyl alcohol swab and allowed to dry, a new blunt needle used to inoculate blood into bottles.
  11. Approximately 5-10mls blood should be introduced into each bottle as results are dependent on the volume of blood cultured.
  12. Dispose of all waste appropriately as per waste management guidelines
    1. NHS Ayrshire & Arran segregation of waste
    2. NHS Ayrshire & Arran waste management policy.
  13. Remove PPE and perform hand hygiene as per the WHO 5 moments for hand hygiene.
  14. Document procedure any problems, action taken and review date in the care bundle DRS 6104 (Appendix 5) and appropriate notes.

Label the bottles correctly and complete microbiology form, stating the date and time of sample, sign and print name as instructed on the form. Label the site of the culture set (e.g. white lumen, red lumen or peripheral), as it is important in helping to distinguish pathogens from contaminants. Do not remove bar code from bottles; these are for Laboratory use only.