Registered Nurses' Association of Ontario

Nursing Best Practice Guidelines

Blood Withdrawl from Central Venous Access Devices

Blood Withdrawal

Method of Blood Withdrawal Description Potential Complication
Discard
  • Removes potential contaminate from the catheter (CVAD)
  • Remove a specific amount of blood from catheter (CVAD) via syringe or vacutainer
  • Use a “new” syringe or vacutainer for the blood sample
  • Flush CVAD with 0.9% saline
  • Potential nosocomical blood loss
  • Potential to confuse a discard syringe with blood sample syringe
Push – Pull
  • Requires mixing the blood back and forth in a syringe several times to eliminate contaminates from the catheter (CVAD)
  • Using a 10 ml syringe, flush catheter (CVAD) with 5 ml 0.9% saline
  • Without removing syringe, 6 ml of blood is aspirated, then pushed back into catheter (CVAD)
  • Repeat this process x3
  • Remove the empty syringe and attach new syringe/vacutainer to obtain blood sample
  • Flush CVAD with 0.9% saline
  • May be difficult to obtain enough blood for 3 – 4 push-pull sequences
  • Risk of haemolysis with the agitation of blood
Re-infusion
  • Involves returning the discard specimen after obtaining blood samples
  • Aspirate 6 ml of blood into a syringe and cap with a sterile cap
  • Obtain blood specimen(s) via a syringe or vacutainer
  • Re-infuse the discard from the 1st syringe.
  • Potential to re-infuse clot(s)
  • Potential to re-infuse contaminated discard
  • Potential for error including the possibility of confusing the discard syringe with the blood sample

(Cosca et al., 1998; Holmes, 1998)

Blood Withdrawal – Additional Considerations

Lumen
  • Use the largest Lumen for blood draws
  • Dedicate a lumen for blood draws when CVAD has multiple lumens
  • Generally not recommended to use heparinized catheter (CVAD) for coagulation studies
  • Use of lumens for drug levels if the drug was infused via that lumen:
    • Does not support the use of silastic catheters for sampling drug levels if the drug is given through the same catheter
    • Aminoglycoside drug levels should be obtained by standard venicollection (in leukemia patients with indwelling right atrial catheters)
    • If venipuncture is contraindicated or difficult to perform, the drug level should be obtained from the catheter only after flushing
    • One method describes to infuse a solution a minimum of 30 min after the dose and then obtain peak levels by standard procedure
    • Another method is to administer a 10 mL IV push flush with 0.9% NaCI through the catheter, which would ensure delivery of the full dose of the aminoglycoside to the patient and then obtain the peak level by standard procedures
    • Regardless of methods, one should view all drug levels obtained from these catheters with skepticism since the system has several possible sources for contamination
Amount of Discard
  • Appropriate amount to ensure accuracy of lab results
  • Discard 3-6 mL
  • Consider dead space volume of CVAD
    • 2x dead space volume – non coagulation tests
    • 6x dead space volume – non coagulation tests
Equipment
  • Use the vacutainer or syringe or a combination of both to obtain blood samples
  • Use safety engineered devices whenever possible (e.g., transfer devices) to reduce the potential for negative outcomes (e.g., needle stick injury)
  • Smaller syringes exert less negative pressure when withdrawing blood samples from catheters (CVAD)

(Frey, 2003; INS, 2000; McCall et al., 2003; ONS, 2004)