Registered Nurses' Association of Ontario

Blood Withdrawal – Additional Considerations


  • 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


  • 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)
Clinical Management
Care and Maintenance to Reduce Vascular Access Complications
Point of Care Resources