A years-long national effort to minimize catheter-related bloodstream infections (CR-BSIs) has produced only modest results. The Centers for Disease Control and Prevention (CDC) compared data from January through June 2009 to data from 2006 through 2008, and found these infections had decreased only 18%. The statistics are troubling, especially given the current intense focus on preventing hospital-acquired infections.
Why do CR-BSIs still kill patients every year? Some experts believe I.V. connector design is a contributing factor. The Food and Drug Administration (FDA) requires all manufacturers of positive-displacement (PD) I.V. connectors to conduct postmarketing surveillance studies to assess whether they could be linked to a higher CR-BSI rate than other types and to assess factors that may contribute to the possible increased risk.
FDA has taken this step because it has received information on possible safety problems linked to PD needless connectors, including three reports of deaths. But despite mounting evidence against these connectors, they’re still used widely. William Jarvis, MD, an internationally recognized infection control expert, notes that studies also link negative-displacement (ND) connectors with increased CR-BSIs.
As primary caregivers, nurses are responsible for the care and maintenance of central venous catheters. This article describes the various I.V. connector designs available and explains why some designs are more effective than others in preventing infections.
Connector’s role in CR-BSI
Because I.V. connectors are attached to catheter hubs, they serve as gatekeepers of the intraluminal fluid pathway (the inside of the catheter). Their design plays a critical role in supporting—or thwarting—your care and maintenance efforts. If their design makes them hard to disinfect with thorough swabbing and flushing, infections are more likely. If their design promotes thorough swabbing and flushing, they can help minimize infections.
Keeping the intraluminal fluid pathway free of contamination is crucial in preventing infection. When bacteria migrate into the fluid pathway and adhere to the inside catheter wall, they colonize and develop a protective biofilm cover. Preventing the intraluminal pathway from becoming an infection source hinges on:
- thorough handwashing
- swabbing the I.V. connector before each access to disinfect the septum
- flushing the I.V. connector to clean the fluid pathway of residual blood.
Connector designs and care routines
All I.V. connectors available have four design elements in common—external housing, a septum, a fluid pathway, and a mechanism that permits entry into the fluid pathway on connection and allows it to close to its original position with disconnection. Dead space refers to areas within the fluid pathway that can’t be cleared with flushing.
Three categories of I.V. connectors
I.V. connectors fall into three categories based on reflux:
- Split-septum (SS) and negative-displacement (ND) connectors are associated with blood moving back into the catheter (reflux) on disconnection. This repeated reflux is thought to coat the intraluminal fluid pathway with blood fibrin, to which bacteria adhere.
- Positive-displacement (PD) connectors are associated with reflux on connection. They cause a final outward push with disconnection; for this to occur, reflux equal to the outward push occurs on connection.
- Zero-fluid displacement (ZFD) connectors cause zero reflux on connection or disconnection and eliminate fluid displacement associated with use.
The septum of an I.V. connector is exposed to and contaminated by the environment. An I.V. catheter may be accessed several times daily to withdraw blood or deliver medications. Each connection provides an opportunity for bacteria to enter the fluid pathway via the septum. Therefore, the septum must be disinfected before each access.
Every blood withdrawal or drug administration requires three separate connections (or four, if heparin is instilled):
- Before any procedure, check for blood return to verify placement.
- Flush the catheter.
- After blood withdrawal or drug administration, flush again to clean the catheter and connector.
Some connector designs make complete disinfection difficult even when performed meticulously. In an effort to improve disinfection, some clinicians have increased swabbing times and use chlorhexidine instead of alcohol. But some connectors are hard to disinfect even with thorough and prolonged scrubbing. An in vitro study of five popular connectors that was designed to replicate the clinical practice outlined above found that microorganisms migrated into the fluid pathway after routine disinfection. The connectors with the most colony-forming units (CFUs) to the least CFUs included one SS type (Q-Syte), two ND types (TKO Clave, MicroCLAVE), one PD type (MaxPlus-Clear), and one ZFD (RyMed-500) connector. (See by clicking the PDF icon above.)
The best septum design is smooth with a tight seal to the connector housing to prevent bacterial entry. A smooth septum eases disinfection. In vitro studies show that ZFD connectors, which have a smooth septum and tight seal, can be disinfected completely with three twists of an alcohol swab. A connector that’s easy to swab reduces the risk of infection due to bacterial migration and supports nursing practice. Although nursing practice is attempting to overcome I.V. connector design issues with long and complicated swabbing procedures, it’s often blamed when infections occur.
Comparing internal mechanisms
ND connectors depend on internal mechanisms to return the septum to the closed position. These mechanisms commonly are associated with dead space. Snapping the septum back in place causes blood pooling (reflux). PD connectors have a mechanism in the fluid pathway that compresses on connection, forming a negative pressure that causes reflux equal to the final push that occurs with disconnection when mechanism expansion occurs. The fluid pathway flows around this mechanism.
Both PDs and NDs have dead spaces in their fluid pathways. When you draw back to verify blood return, the entire fluid pathway (including dead space) fills with blood. But when you flush, dead space doesn’t contact the flush solution, so the blood can’t be removed totally. Because fluid follows the path of least resistance, it flows around these internal mechanisms, missing the “nooks and crannies.” Fibrin remains in the dead space, setting up the surface conditioning needed for bacteria to attach and colonize. In contrast, ZFD connectors have a straight fluid pathway with no dead space and can be flushed clean with as little as 1 mL of saline solution.
Differences in clamping sequence
With SS, ND, and PD connectors, a procedure called a clamping sequence must be done when a blunt cannula, syringe, or tubing is disconnected from the connector, to minimize blood reflux associated with use. This procedure can cause confusion for clinicians because with an SS or ND connector, it’s done exactly the opposite way it’s done with a PD connector. With an SS or ND connector, you apply pressure to the syringe plunger, close the clamp, and then disconnect. But with a PD connector, you disconnect first and then close the clamp. (See by clicking the PDF icon above.)
Adding to the confusion, to access a SS or ND connector, you must follow this sequence: swab the septum, connect the syringe to the connector, apply pressure on the syringe plunger, and open the clamp just before injection. If you open the clamp before connecting the syringe, reflux occurs, even though it was minimized at disconnection.
Performing the right clamping sequence is crucial to minimizing use-related reflux and associated fibrin build-up. Many facilities stock a variety of connector types. Even for nurses well-educated in I.V. connector maintenance procedures, this variety can pose a challenge to remembering the right sequence for each connector type. Also, you need to visually identify the connector type; the package label doesn’t state if the connector is a PD or ND and doesn’t describe the clamping sequence required. Many manufacturers’ connector directions for use state simply, “Follow hospital policy”; but hospital policy may state, “Follow manufacturer’s directions for use.” Dr. Jarvis suggests using an I.V. connector that doesn’t require a clamping sequence or using only one connector type throughout the facility.
What the research shows
According to researcher and author Cynthia Chernecky, “based on the serious consequences of infection and as connectors are a statistically significant variable in the development of occlusions and CR-BSIs, practitioners must be astute to the latest research and recommendations to help patients.” Her research supports the use of ZFD connectors to enhance intraluminal protection and improve patient outcomes. At Methodist Extended Care Hospital in Memphis, Tennessee, an acute long-term care facility, three different connectors were studied over 3.5 years—Q-Syte (SS), SmartSite (ND), and InVision-Plus (ZFD). Use of the SS yielded the highest CR-BSI rate—six per 1,000 catheter days. The ND performed better at 3.3 per CR-BSIs per 1,000 days. Only the ZFD connector produced an acceptable rate by today’s standards—0.5 per 1,000, including the most desired “zero” rate for the final 10 months of the study period. All patients in this facility had complex comorbidities and therapeutic regimens and came to the facility with the catheter in place. Even with this challenging population, combining technology with practice offers a better approach than depending strictly on nursing practice.
Although FDA’s requirement of postmarketing surveillance study centers on PDs, a closer look at the record shows that SS and ND connectors are linked to elevated CR-BSI incidence. Only in the last decade has the intraluminal pathway has been studied and identified as a problem. Protecting the pathway requires specific I.V. connector features developed to minimize bacterial migration and internal surface adhesion in addition to eliminating needles. Only the ZFD connector design, created to protect the intraluminal fluid pathway by offering fail-safe backup to nursing care and maintenance efforts, achieves this higher standard.
Nonetheless, while the ZFD connector is the safest choice, it’s unrealistic to expect healthcare facilities to switch to it right away. In fact, many facilities are contractually bound to purchasing groups that don’t stock them. Until regulators act more comprehensively against risky connector products, facilities should take these crucial steps:
- Teach all clinicians involved with vascular access to identify all catheter connector types they’re using.
- If possible, stock only one connector type to minimize confusion about the proper clamping procedure.
- Develop swabbing protocols based on the connector type in use, instead of imposing an artificial swabbing time.
- Educate all clinicians about the importance of swabbing and flushing catheter connectors.
Pressure is mounting for healthcare facilities to eliminate CR-BSIs. The Center for Medicare & Medicaid Services no longer reimburses hospitals for treating these infections because it deems them preventable. It also requires all Medicare-eligible hospitals to report certain hospital-acquired infections, including CR-BSIs, to get full payment in its pay-for-reporting program. Obviously, patients pay the heaviest price for CR-BSIs, but the price is rising for healthcare facilities, too.
Denise Macklin consults on I.V. clinical education for RyMed Technologies, Inc. and has coauthored several nursing textbooks.
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