Flushing of vascular access devices is a well-established standard of care. According to the Infusion Nurses Society, flushing is defined as: the act of moving fluids, medications, blood, and blood products out of the vascular access device into the bloodstream; used to assess and maintain patency and prevent precipitation due to solution/medication incompatibility. Flushing is a method of accessing catheter function, identifying malfunction, and minimizing the risk of occlusion, thrombosis, and catheter bloodstream infection (CRBSI).
The opportunity for occlusion and blood clots occurs at the outset of the catheter placement. For instance, during insertion, blood is aspirated to confirm the tip is within the blood vessel location. Each time the catheter is used to deliver a dose of medication or to obtain a blood sample, or when the administration set or needleless injection device is changed, microorganisms and blood enter the lumen. Over time, the biofilm-fibrin combination can become thick enough to occlude the lumen partially or completely. Patient activity and suboptimal flushing techniques can also cause blood to reflux into the lumen and cause complication.
Ineffective positive pressure can result in a rebound effect that pulls up blood into the catheter tip as the syringe is detached from the hub, known as reflux. Blood reflux occurs when needle free connectors are used with improper clamping sequences. Without clamping or an anti-reflux valve, the flushing may provide a short-term solution to compensate for backflow if blood, which may later lead to patency problems and other complications. Timely and efficient flushing of VADs using the correct technique for clamping and flushing the needle free connector is therefore important to ensure optimal removal or blood or other medications or infusions.
One way to help eliminate blood reflux is to use a prepared pre-filled syringe. Pre-filled syringes aid in optimal flush objectives by promoting zero blood reflux and reducing the amount of pressure exerted against the catheter wall, minimizing vein injury. For maintaining catheter patency, sodium chloride (normal saline flush) and heparin are commonly used. Sodium chloride is used to assess catheter patency and to aspirate for a positive blood return from the catheter. Heparin is an anticoagulant indicated for both the prevention and treatment of thrombotic events such as deep vein thrombosis, pulmonary embolism, and atrial fibrillation.
Pre-filled syringes have different flush volumes options (3, 5, and 10 mL) for various VAD types, lengths, and sizes. Smaller syringes generate greater pressure on ejection, whereas large syringes reduce the amount of pressure exerted against the catheter wall. For a standard 10 mL syringe, it requires a constant, even force on the syringe plunger during flushing to create an effective means of preventing backflow of blood or reflux into the catheter tip. Flushing with pre-filled syringes is recommended in combination with the pulsatile technique for maximum efficiency.
Positive Pressure Flushing
Most vascular access device associated complications can be minimized and even prevented by strict adherence to the healthcare standards and flushing protocols. A pulsatile pulse involves a rapid stop-start or push-pause technique as the solution is injected into the catheter. Studies have shown that a resulting turbulent flow created by the push-pause technique is considerably more effective at rinsing the lumen, in comparison to a continuous laminar flow. (Guiffant et. Al 2012) The pulsatile pulse technique has been found to significantly reduce catheter, bacterial attachment, and growth in VADs, in comparison to a continuous flushing method without the turbulence. It is a key strategy in occlusion and infection prevention, as clearing the catheter lumen of all traces of blood and medications can reduce the potential for bacterial adhesion and colonization, leading to catheter related bloodstream infection.
A correct, positive pressure technique when using a standard 10 mL syringe, requires a constant, even force on the syringe plunger during flushing, to create an effective means of preventing backflow or blood reflux into the catheter tip. This form of flushing is recommended in combination with a pulsatile technique for maximum efficiency.
INS Positive Pressure Techniques to Minimize Blood Reflux into the VAD Lumen
- Prevent syringe-induced blood reflux by leaving a small amount (eg, 0.5-1.0 mL) of flush solution in a traditional syringe (ie, not a prefilled syringe) to avoid compression of the plunger rod gasket or by using a prefilled syringe designed to prevent this type of reflux.
- Prevent connection/disconnection reflux by using the appropriate sequence of flushing, clamping, and disconnecting determined by the type of needleless connector being used. (Refer to INS Standard 36)
- Use a pulsatile flushing technique. In vitro studies have shown that 10 short boluses of 1-mL solution interrupted by brief pauses may be more effective at removing solid deposits (eg, fibrin, drug precipitate, intraluminal bacteria) compared to continuous low-flow techniques. Clinical studies are needed to provide more clarity on true effect of this technique.
- Consider flushing all lumens of a multilumen catheter after obtaining blood samples to reduce the possibility of changing intraluminal pressure causing blood reflux into other lumens.
- Follow manufactures’ directions for use regarding clamping the VAD when not in use. Clamping can prevent contamination and exsanguination in the event of inadvertent disconnection of any set or add-on device.
Flushing of a vascular access device is a crucial intervention that facilitates a proactive approach in relation to maintaining catheter patency and function. Therefore, it is an essential responsibility that should be carried out by a skilled healthcare professional.
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Guiffant G, Durussel JJ, Merckx J, Flaud P, Vigier JP, Mousset P. Flushing of intravascular access devices (IVADS)—efficacy of pulsed and continuous infusions. J Vasc Access. 2012;13(1):75–8.
Moureau, N. L. (2019). Vessel health and preservation: The right approach for vascular access. Springer International Publishing.