Registered Nurses' Association of Ontario

Locking Techniques

  • Locking prevents blood from backing up into the catheter lumen when the device is not in use.
  • Positive pressure technique
    • Positive pressure locking techniques maintain positive pressure inside the lumen in order to prevent blood reflux from the vein into the lumen of the VAD, thus preventing fibrin buildup, clots and thrombotic device occlusions.
  • Value technology – positive pressure caps
    • Devices with positive fluid displacement reduce or eliminate the variable of inconsistent flushing technique.
    • Several positive pressure cap products consistently achieve positive fluid displacement and positive end-pressure.
    • Catheters using positive pressure valves should not be clamped until after disconnection of the flush syringe.
  • Value technology – VAD
    • A closed or open-ended valved CVAD is designed to resist blood reflux into the catheter lumen from the vein.
    • The closed-ended valved CVAD (e.g., Groshong®) has an internal three way valve at the tip of the catheter.
    • Alternately, the open-ended valved CVAD (e.g., Pressure Activated Safety Valve (PASV®) has an open ended tip, and a pressure valve in the hub of the catheter.
    • The nurse needs to maintain positive pressure on the syringe plunger when disconnecting the syringe from the cap or hub.
    • Positive pressure caps can also be used with valved catheters.
Clinical Management
Care and Maintenance to Reduce Vascular Access Complications
Point of Care Resources