Introduction

Patent peripheral and central venous catheters, the goal for all healthcare settings, will flush easily without resistance; produce a brisk, free-flowing blood return on aspiration; and allow for unimpeded fluid flow through the catheter. Lack of patency is a common and confusing problem. Resistance when the catheter is flushed or failure to obtain the required brisk blood return before catheter use indicates a nonfunctioning catheter. Fluid flow by gravity may be extremely slow, or the infusion pump could present occlusion alarms. This problem disrupts patient care, threatens attainment of treatment goals, adds to the burden of limited nursing resources, increases the risk of additional complications such as infiltration or extravasation, and increases cost of care.1,2

Catheter occlusion may be categorized as partial or complete occlusion. Partial occlusion means that although the nurse flushes or infuses through the catheter, it does not yield the brisk blood return required for complete assessment of catheter patency. Complete occlusion is defined as the inability to flush, infuse, and aspirate from the catheter. Catheter occlusion can be caused by drug precipitates and several mechanical issues, although intraluminal thrombosis is thought to be the most common factor. Many factors cause blood to move into the catheter lumen from many sources (Table 1). Catheter patency is also affected by fibrin and thrombosis development inside the vein around the catheter tip, where the flushing solution or technique will have no effect. This discussion will be limited to intraluminal causes of thrombotic occlusion, focusing specifically on solutions used to flush and lock the catheter.

Dilute heparin is used as a standard flush to lock most central venous catheters. The exceptions are valved catheters and needleless connectors that are indicated to be used with saline only.3 However, numerous issues regarding the use of heparin have led to serious concerns in recent years. These issues drive the many questions about the continued use of heparin for catheter-locking procedures, including technology changes, cultural concerns, impact on coagulation laboratory values, drug compatibility, biofilm growth, heparin-induced thrombocytopenia, and medication errors.