Abstract

Design, function, and performance vary between negative displacement, positive displacement and pressure-activated antireflux needleless connectors (NCs). Marketing terms used to classify needleless connectors do not adequately describe function and performance, leading to confusion and poor understanding of the correct flush-clamp-disconnect sequence specific to each NC design. We compared commercially available NCs without integrated anti-reflux technology to their exact design counterpart with anti-reflux technology. The goal of this study was to evaluate each NC’s ability to control bi-directional fluid movement caused by mechanical and physiological pressure changes and measure reflux volume. A venous simulator was used to measure and visualize fluid displacement associated with each NCs design upon connection and disconnection of a syringe. A bi-directional flow test was also performed by creating a pressure gradient between two reservoirs which were connected using the NC being tested. The fluid displacement at syringe disconnection was negative for all devices tested. All NCs with integrated anti-reflux technology significantly reduced the reflux volume compared to their design counterparts without anti-reflux technology (P < .0001). The difference in reflux volume was statistically significant (P < .0001) between all NC devices with integrated anti-reflux technology (0.27µL; 95% CI 0.21-0.34µL) compared to all devices without anti-reflux technology (4.15µL; 95% CI 3.76-4.54µL). All NCs without anti-reflux technology failed to demonstrate the ability to control blood reflux and bi-directional fluid movement. These results demonstrate that integrated anti-reflux technology is effective at preventing blood reflux caused by mechanical and physiological pressure changes in a closed IV system.

Keywords: Blood; Biofilm; Catheter-related blood stream infections; Infection control; Vascular access devices; Needleless connectors.

Introduction

Needleless connectors (NCs) were originally introduced as an intravenous (IV) catheter accessory in the early 1990s to prevent needlestick injury among healthcare workers and to maintain closed systems. Half of all post-insertion catheter-related infections are attributed to bacterial colonization of catheter hubs and NCs [1-5]. When refluxed blood contacts IV catheter surfaces, a layer of plasma proteins, which are responsible for platelet adhesion, activation and biomaterial-induced thrombus [6-8] adsorb to the intraluminal surface instantly forming a thin conditioning film [6,9]. This conditioning film sets in motion a series of biological reactions that help form the fibrin mesh that traps blood cells and promotes thrombus formation within the catheter lumen [6,8,10,11] (Figure 1). Bacteria entering through the NC [12,13] can bind to the protein-coated surfaces of the IV catheter and proliferate into biofilm [9,14,15]. Thrombolytics such as tissue plasminogen activators (tPA) commonly used to treat intraluminal catheter occlusions catalyze the conversion of plasminogen to plasmin which cleaves fibrin into fibrin degradation products and dissolves the thrombus [11] (Figure 2). Studies have demonstrated the risk of infection is approximately 3 to 4 times higher when thrombolytics are used to treat intraluminal catheter occlusions [16-18]. This increased infection risk is due to the release of dissolved bacteria-riddled thrombus into the bloodstream during flushing.

Figure 1: Foreign body response following blood contact to IV catheter material leading to intraluminal thrombotic catheter occlusions. Abbreviations: IV, intravenous.

Figure 2: Illustration depicting how bacteria within an occluded IV catheter are dislodged by tPA when a clot is dissolved, thereby allowing the microbes to enter the bloodstream. Abbreviations: tPA, tissue plasminogen activator.

The external design of NCs is similar but there are significant internal differences among the available devices that affect function, performance, and patient safety. For example, all NCs allow for bi-directional fluid movement, defined as the ability to administer or withdraw fluids or medication for infusion and aspiration [20], but not all NCs contain an internal mechanism to control when and how much fluid movement occurs. Commercially available NCs are classified as negative displacement, positive displacement, neutral, or pressure activated anti-reflux devices according to the internal mechanism for fluid displacement by the device [19] (Table 1). It is important that clinicians know which type of NC they are using so that they can employ the appropriate flushing, clamping, and disconnection sequence. However, the 8th edition of the Infusion Therapy Standards (Standards) cautions that there are no established criteria from device regulatory agencies that can help clinicians determine whether a commercial NC is assigned to a particular category [19]. Given this information, it is not surprising that in a survey of 4,000 healthcare workers, 544 responded reporting that over 47% did not understand the correct method to flush and clamp a catheter with the NC or within multiple types of NCs used by their institution [20].

Table 1: Classification of needleless connectors (NCs) by internal mechanism for fluid displacement by the device.

According to the Standards, there is limited evidence to support the superiority of one type of NC over another, particularly regarding the ability to prevent internal contamination [19]. Instead, clinicians are urged to evaluate the latest evidence when making decisions about the choice of NC. In the absence of guidelines and standardized classification criteria, deciphering the marketing terms (Table 2) used by NC manufacturers is problematic and can make it challenging for clinicians to integrate NCs into practice. The aim of this study is to add to the existing body of knowledge by using in vitro methods to evaluate the performance of commercially available NCs without integrated anti-reflux technology compared to their exact design counterpart with anti-reflux technology based on reflux volume and their ability to control bi-directional fluid movement.

Table 2: Common terms and definitions associated with NC design and function.

Materials and methods

Four commercially available NCs without anti-reflux technology (Microclave™, ICU Medical, San Clemente, CA, USA; NIS®6P, Nexus Medical, Lenexa, KS, USA; Bionector®, Vygon, Ecouen, France, and NeutraClear™ CAIR LGL/BD, Teolo, Italy) were compared to their exact design counterpart with anti-reflux diaphragm technology (Neutron™, ICU Medical, San Clemente, CA, USA; TKO®-6P, Nexus Medical, Lenexa, KS, USA; Bionector TKO®, Vygon, Ecouen, France, and NeutroX™, CAIR LGL/BD, Teolo, Italy)(Figure 3).