Central venous catheters (CVC) secure vascular access for fluids, medications, blood products, total parenteral nutrition (TPN), and hemodialysis. They are employed for both inpatients and outpatients. The Centers for Disease Control and Prevention (CDC) estimates that 41 000 central line-associated bloodstream infections (CLABSIs) occur annually in hospital intensive care units in the United States. Among patients with long-term CVCs, more than 250 000 CLABSIs occur annually. The National Healthcare Safety Network (NHSN) reports a rate of 1.5 CLABSIs per 1000 central line-days in the United States with a mortality rate of 12% to 25%. A healthcare cost of $45 814 is estimated for each CLABSI in the United States.
Colonization is universal after insertion of a CVC, occurring as early as 1 day after insertion, and is independent of catheter-related infection. Electron microscopy studies of catheter surfaces show that adherent microorganisms can be found in either a free-floating form or a sessile form embedded in a biofilm.
The process of adherence results from the interaction of three factors: intrinsic properties of the catheter, microbial factors, and host-derived proteins. The surface irregularities and charge difference of the catheter facilitate bacterial adherence. Some microorganisms adhere better to polyvinyl chloride, silicone, and polyethylene. Concomitantly, a thrombin sheath forms on the internal and external surfaces of the catheter. This sheath results from the deposition of proteins such as fibrinogen, fibronectin, laminin, and thrombospondin.
Microorganisms colonize vascular catheters through different sources: For short-term catheters, the skin of the site of insertion is the major source for colonization; bacterial skin flora migrate along the external surface of the catheter. The hub of the vascular device is the most common source of colonization for long-term catheters, with microorganisms introduced from the hands of medical personnel. In this case, colonizing bacteria migrate along the internal surface of the catheter. Hematogenous seeding and contamination of the infusate or additives such as contaminated heparin flush are rare causes of colonization and infection of vascular devices.