Needleless Connectors and Bacteremia: Is There a Relationship?
By Marilyn Hanchett, RN, PhD
Needleless connectors, used today as integral components of an infusion system, evolved in response to demands for enhanced healthcare worker safety and as part of the continuing development of infusion technology. At this time, there are three design categories among needleless connectors: split septum connectors, luer activated valves, and luer valves with positive displacement. Numerous branded products are available within each category. Although needleless connectors offer enhanced safety features, there have been recurrent concerns about an increased risk of bacteremia associated with their use. This article reviews the development of these devices, examines the available evidence base, identifies unresolved issues, and suggests strategies to facilitate optimum use of needleless connectors within infusion systems.
During the past two years there has been increasing concern expressed by infection control practitioners, infusion specialists, and epidemiologists that the use of needleless connectors, either generally or specifically according to design category or brand, is directly responsible for increased bacteremia inpatients receiving intravenous therapy.
Bacteremia associated with infusion therapies is known to increase morbidity, prolong inpatient hospitalizations, and significantly increase the economic impact of care.1 The incidence of catheter-related bloodstream infections is disturbingly high, especially among central catheters, and the mortality risk has been reported as high as 30 percent in ICUs.2 Since intravenous therapy is among the most widely used invasive procedures in all healthcare settings, the risk of complications is often also high. If any part of an intravenous system increases patient risks, then the clinician must be aware of it and be prepared to respond accordingly.
The Evolution of Needleless Connectors
First Generation Products
Prior to the 1980s, intermittent access to an intravenous system was accomplished by inserting a beveled, hollow bore needle into a latex cap positioned either along the administration set or at its termination. The needle was often secured with tape and was prone to disconnection. Emerging technology soon combined with engineering controls required under the Occupational Safety and Health Administration (OSHA) Boodborne Pathogens Standard to produce a new generation of connectors.
This first generation of devices featured a split septum that could be repeatedly accessed with a blunt cannula. These connectors were designed to accommodate the need for intermittent access to the intravenous system while simultaneously eliminating the use of needles. The split septum connectors were used in combination with other emerging technology, including safety catheters that typically offered recessed or retractable needles. Although this new technology was neither immediately nor universally adopted and the costs associated with its use often posed a barrier to implementation, these first generation safety products were successful in reducing the exposure incidents reported by healthcare workers.3 However, the first generation split-septum products did not address the problem of catheter occlusion. Split-septum connectors created negative pressure when the blunt cannula was withdrawn. Any negative pressure at the time of disconnection can jeopardize device patency by allowing retrograde flow into the lumen of the catheter.
Second Generation Products
During the 1980s, technology continued to evolve. The second generation of needleless connectors replaced the split-septum design with an anti-reflux valve activated by the use of a malefemale luer configuration. The process of joining the luer components created a locking action that exceeded the stability of the connection possible with the splitseptum product. Since female and male luer mechanisms were already a well-established concept within medical device design, the integration of a luer into a connector was easily understood and accepted by clinicians.
Like the first generation of connectors, the luer devices permitted intermittent access and eliminated the use of needles. However, its unique design was compatible with the use of most syringes and the need for a blunt cannula was eliminated. In addition, the ant-reflux design of the luer activated valve helped neutralize any negative pressure occurring when the syringe (or other luer device) was disconnected from the needleless connector. And when used according to manufacturer guidelines, these products did not demonstrate an increased safety risk.
Unfortunately, the luer compatible design has been demonstrated to pose other, non-infectious safety risks to patients. The serious incidents that have been reported have all involved incorrect product use. For example, in 1996 and 2002 the Institute for Safe Medicine Practices cautioned the healthcare industry about the potential to connect a syringe containing oral medication to an intravenous system by attaching it to a needleless valve.4 In 2003, the Food and Drug Administration (FDA) issued a safety alert following a patient death when oxygen was accidentally connected to a needleless luer device.5 However, during these years intravenous systems were also evolving. Implanted infusion ports were introduced for patients requiring long-term therapies.
Tunneled central catheters became a viable option for patients no longer candidates for peripheral infusions. Peripherally inserted central catheters (PICCs) offered a safer alternative when therapy was expected to continue for more than several days.
Third Generation Products
With more advanced catheter design and the clinical demand for extended catheter dwell times, the need to maintain patency became a growing clinical concern. Replacement of clotted catheters was expensive and traumatic for the patient. A clotted lumen can also increase the risk of infection. A number of solutions emerged to address this need, including the development of a valved catheter, the use of fibrinoloytics for catheter clearance, and the introduction of a positive displacement connector.
The third generation of connectors combined the existing lueractivated valve concept with a displacement action. This action expels a small amount of the solution used to flush the catheter when the syringe used for flushing is disconnected from the leur. The displacement is a passive feature and occurs automatically. Once this action has occurred, the remaining solution (usually heparin or saline) is retained within the catheter and no further positive pressure exists. The positive pressure luer connector is designed to reduce retrograde flow into the catheter more effectively that either split-septum or standard luer connectors.
However, although the third generation of connectors offered advantages over previous designs, they cannot prevent occlusion completely or under all circumstances. Nonetheless, positive displacement connectors are now widely used to help reduce complications in central catheters. Today, examples of split-septum, luer-activated and positive displacement luer connectors are commercially available and commonly used in intravenous systems (see Table 1).
Emerging Infection Concerns
The gradual introduction of and product diversification within needleless connectors was accompanied in the 1990s by concerns regarding their infection risks. Studies published during this time period revealed a number of issues that could potentially lead to increased infections. For example, needleless connectors were not always used according to manufacturer guidelines. Infection risks increased when connectors were changed less frequently than specified in protocols.6-8 An increased infection risk was also linked to specific infusates such as TPN or other independent risk factors such as use of multilumen catheter or recent BMT.9-10
Although a variety of needleless connectors were investigated, no individual products were conclusively associated with either increased risk or national outbreaks. While initial concerns focused on device failure, a better understanding of device use in conjunction with enhanced product design, helped allay clinician fears and allow needleless connectors to remain an integral safety component of most, if not all, intravenous systems. In fact in 2002 the HICPAC IV Guideline stated that when devices are used according to manufacturer recommendations, they do not substantially affect the incidence of CRBSI.11
A Limited Base of Evidence
Since the 1990s, concerns have lingered about the relationship of needleless connectors to bacteremia. Infection control experts have remained alert to the serious complications that can potentially be associated with these seemingly innocuous devices. But the need for better device-related science remains an elusive goal.
A review of the literature indicates that the studies of the 1990s have not been significantly expanded by subsequent experimental research. In fact, although millions of needleless connectors are used in patient care, the scientific evidence upon which to base their use remains limited. Current studies vary widely in their scope, design, and scientific rigor.
For example, from 1999 to 2004, three new studies attempted to examine the efficacy of positive pressure in maintaining the patency of central venous catheters. These prospective studies show that positive displacement of fluid within central catheters is more effective than negative pressure (or displacement) in preventing occlusions. However, these studies also show that the positive displacement action accomplished with valve technology cannot eliminate the problem of occlusion in all central venous catheters.12-14
Recent published reports have investigated the issue of infection. Two studies, using different products, have reported a reduced potential for microbial contamination when traditional caps were replaced with a needle-free, luer valve that was been appropriately disinfected prior to use.15-16
As risks associated with needleless connectors have become an international infection control concern, published reports are now available in non-U.S. based clinical journals. For example, an evaluative study conducted in Britain reported inconsistency of use and routine care of all connectors used with central catheters prior to staff education and standard implementation of a luer valve.17 A randomized controlled trial conducted in Spain among intensive care patients requiring central venous catheters found a significant reduction in bacteremia when a needleless connector was used in place of a three-way stopcock.18
In addition to the studies published in scientific, peer-reviewed journals there are also a number of product evaluation studies or reports that have appeared in clinical practice journals, on Web sites, and in trade publications. These articles generally describe an institutions experience in using a needleless connector or after changing brands. This level of evidence is typically presented either as a quasi-experimental study or as descriptive research and lacks the scientific rigor and control used in the experimental designs. Their lack of control is especially problematic when attempting to infer causation and/or generalize the findings to other practice settings.
Understanding the Current Controversy
Similar to the experiences of a decade ago, reports of bacteremia have resurfaced. The implied cause of these new or increased infection rates appears to be the use of needleless connectors. Concern about the use of needleless connectors has been expressed in presentations, posters, and/or abstracts presented at annual meetings such as the Society of Healthcare Epidemiologists of America (SHEA), the Association for Professionals in Infection Control and Epidemiology (APIC), and other professional organizations since 2004. Simultaneously, some manufacturers have attempted to leverage infection concerns to better position their individual brands. For clinicians struggling to understand the issue, the result is often a confusing jumble of genuine, albeit unanswered, device concerns with product marketing claims, data from bench studies, expert speculation, and over-generalization of findings from institutional reports.
The dilemma remains, as it did a decade ago, the same for all who currently attempt to analyze the infectious risk potential of these devices. There is simply not enough scientifically rigorous evidence upon which to make a conclusion. Although there have been sporadic reports of increased infections, there is insufficient evidence to indicate a trend that can be reliably associated with a specific type of connector or any particular product.
Potential Risk Factors Requiring Further Investigation
In order to fully understand the risk potential of any type or brand of needleless connector, several important factors need to be clarified.
1. User Error or Device Failure?
Most published reports have not measured the potential for user error. Any break in aseptic technique when using a needleless connector sets the stage for potential infection. At this time, the lack of information related to user error with needleless connectors is a significant barrier in analyzing the underlying cause of actual or presumed increases in bactermia. Although the devices are mechanically simple and their use intuitive, user errors can still occur. For example, clinicians may not disinfect the surface of the connector before accessing the intravenous system. Connectors may not be flushed completely after use or may not be changed according to established protocols. Luer valves may not fully rebound upon disconnection. Split-septum connectors may be damaged by incorrect access with a needle or an incorrectly placed needle rather than a blunt cannula. Extension sets, attached to connectors and intended for intermittent IV access, may not be clamped as required by the manufacturer.
In any study that attempts to identify causation, it is essential that all reasonable contributing variables be identified and controlled. Without this essential step, it is easy to draw the wrong conclusion. Allegations of device failure are often the initial and presumptive cause attributed to sudden increases in bloodstream infections. While concern over device failure is a possibility that must always be considered, it cannot be presumed to the primary cause when insufficient evidence exists to support the claim. At the same time, designing a clinical study that can achieve the necessary level of control is very challenging and can be cost prohibitive for the sponsoring institution. This is particularly problematic when studying needleless connectors since both the number of potential users and opportunities for intentional or accidental misuse is high in all practice settings where infusion therapies are administered.
The potential impact of incorrect use cannot be ignored, especially since the study by Cookson et al. reported that only 60 percent to 70 percent of nurses maintained needleless connectors correctly.6 While procedural compliance by clinicians performing infusion therapy has not been thoroughly studied, other aspects of infection control have been. Perhaps the best-known focuses on hand washing where, no matter how frequent or extensive the education provided, clinician compliance rarely exceeds 40 percent.22 If compliance with the use of needleless connectors is similar to compliance with handwashing, user error could emerge as the most important contributing factor in device-related infections. At this time, however, it remains an unknown variable.
2. Device Design In spite of marketing claims to the contrary, the superiority of one type of design for needleless connectors has not been proven. In fact, the impact of residual volumes, dead spaces, and flow rates on infection risk has not been extensively analyzed. Manufacturers will inoculate the access surface and/or the fluid pathway of their device with bacteria to test, under strict laboratory conditions, the efficacy of surface decontamination with an approved disinfectant as well as the possibility of bacterial growth and transfer along the fluid pathway. Such testing is usually limited to seven or eight consecutive days. Longer-term outcomes, especially in less rigidly controlled environments, have not been discussed in the literature.
Part of the current controversy focuses on determining whether split septum or luer-activated valve technology represents the safest approach in preventing catheter-related bloodstream infections. Until more evidence exists regarding the impact of mechanical design aspects on infection risk, none of the three currently available categories of needleless connectors can claim superiority.
3. The Impact of Biofilm Microbial biofilm is the accumulation of polymers excreted by bacterial cells adhering to a device surface. The accumulation of biofilm on medical devices, including intravenous catheters, cannot be prevented and creates clinical management challenges for long-term, indwelling devices. Biofilm accumulates rapidly on central venous catheters and once in place, is difficult to eradicate. Biofilm-related infections often require removal of the device.19
There has been minimal investigation on the role that biofilm may play in the needleless connector controversy. A study published in 2001 examined needleless connectors used at a bone marrow transplant center. The results of this analysis showed that 63 percent of the 24 needleless connectors tested contained biofilms comprised predominantly of coagulase-negative staphylococci.20-21 These results suggest additional questions. If biofilm has been detected on central venous catheters is less than 72 hours after placement, is development within needleless connectors equally as rapid? Is the accumulation of biofilm facilitated by mechanical design aspects of these devices? Does biofilm demonstrate an affinity for split-septum products, luer-activated valves, or is there no difference? Answers to these and many other questions will remain unanswered until more research is done.
Taking Action When Evidence is Lacking
The lack of reliable evidence, although highly problematic, is not an insurmountable obstacle for ICPs urgently seeking to prevent bacteremia in patients receiving infusion therapies. Awareness of a limited evidence base helps direct decisions and actions along lines of the best available data and objective reasoning. The following list summarizes steps that infection control practitioners can take now.
- Use interdisciplinary collaboration to verify that surveillance systems and collection of epidemiological data for intravenous procedures are adequate. Although device-specific surveillance often focuses on critically ill patients, risks may also be high among those who are less acutely ill but require long-term catheters and therapies. Collaboration is essential in identifying these patient groups and mobilizing the resources to conduct the necessary data collection and analysis.
- Critically examine the impact of intravenous education and training in your institution. Although infusion therapy is among the most commonly performed invasive procedures, most clinicians have received very little formal education about it. While manufacturers can provide excellent in-service programs and training materials, it is the responsibility of the institution to make sure that procedural compliance and infection control standards are maintained, reinforced and reviewed as often as necessary to meet patient care goals.
- Carefully analyze all product literature and studies. Understand the scope of published studies and whether their design, methods, findings, and conclusions meet the standards of scientific evidence. Insist that claims of product superiority be supported with reliable information. Be an informed, skeptical, and objective consumer when confronted with product marketing.
- Remember that while intravenous therapy systems and products are always changing and it is important to keep current with new technology, no product can replace sound clinical judgment, critical decision-making, and rigorous infection control practice.
- Look for new scientific evidence. Research in the use of needleless connectors, and especially the impact of biofilm, continues and clinicians should expect that the current evidence base with be expanded by future studies.
- Involve your patients. This is especially important in patients who require long-term or chronic therapies. These individuals are often experts in managing their catheters and supplies that far exceed that of many healthcare professionals; their feedback can be an important addition to your regular sources of information and evaluation.
Needleless connectors, initially designed to reduce needlestick exposures among clinicians, have contributed to a safer workplace and helped reduce the injury risks associated with performing infusion procedures. Whether or not needleless connectors increase the risk of bacteremia or prevent catheter occlusion is less certain.
Effectiveness of intraluminal fluid displacement triggered by specific valved connectors is suggested by current studies but has not been extensively examined in the literature. At the same time, as needleless connectors have been the alleged cause of infection outbreaks, studies have failed to conclusively demonstrate the link or identify any product trends. Many products have been investigated but none have shown greater or lesser risk for potential infections. Many important variables in the infection equation, including user error, mechanical design, and the role of biofilm, remain unknown.
Like all medical products, needleless connectors present the clinicians with both advantages and disadvantages. And like other products, they are only as safe and reliable as the individuals using them. Until conclusive evidence becomes available to differentiate among existing products or as part of a new generation of products, clinicians must continue to include monitor needleless connectors, evaluate device-related outcomes, and seek to better understand the potential for user error within all practice settings. ICT Marilyn Hanchett, RN, PhD, is director of clinical affairs for IgG America.
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