Needleless connectors (NCs) are devices connected at the end of vascular catheters. Once connected to the vascular catheter, two critical clinical activities could be done: (1) infusion can be done through it, or (2) aspiration can be performed. Suppose no needleless connector is attached at the end of the vascular catheter. In that case, the infusion can still be done, but the aspiration of fluid, such as blood, is very unlikely.
NCs are not solely meant to connect two lines. Other functions are outlets for infusion and aspiration. However, the most crucial role is to serve as microbial gatekeepers. Being at the end of the catheter, NCs prevent the unnecessary entry of disease-causing microorganisms while infusion or aspiration is occuring.
Precursors of NCs
Intravenous Plastic Line with Injection Bung
Before the advent of NCs, the intravenous plastic line was used to convey fluid to patients’ vascular systems. This was provided with an injection bung where medications are injected now and then. With frequent injections, leakages are produced wherein bacteria could enter, and infusate could flow out. As more drugs with irritant pH or chemical composition are injected, the development of phlebitis (inflammation of veins) occurs. We have to replace the catheter and the intravenous frequently. To prevent phlebitis and its worsening, we need to replace the catheter and the intravenous line every 24 hours.
The three-way stopcocks came next in the market. This device also allows the administration of the drug(s) and blood aspiration for laboratory examinations. However, when healthcare workers (HCWs) arrive, they discover that the protective caps are missing. This means that the openings of the stopcocks have been left open for some time, allowing the entry of disease-causing bacteria. Besides, the female luers of the stopcocks cannot be decontaminated or disinfected before their use. This increases further the occurrences of infections.
Another drawback of the three-way stopcocks is that needles are used for the many intravenous administrations as more and more injections are done. Consequently, needlestick injuries occur, and a lot of the HCWs will likely be exposed to the risk of blood-borne virus infections. A not long time ago, in the US, needles for intravenous access had been disallowed so that exposing the HCWs to highly infectious diseases will not occur.
Birth of Needleless Connectors
needleless connectors were developed and reached the market for acquisition and use by the healthcare industry, such as hospitals and medical clinics, to avoid leakages in the injection bungs and the spread of infections.
Designs of Needleless Connectors
There are several types of NCs; each differs from another based on how they look and how they work.
The external housing of the NCs may be opaque, colored, or transparent, and the outer connection surface may possess an angled center and appears as virtually flat, concave, or indented.
There are minimal differences in terms of external appearances. However, there are several internal differences because each interior design dictates and performs a particular function.
Classifications of NCs Based on the Internal Designs
Simple versus complex
NCs can be categorized into simple or complex needleless connectors. Straightforward NCs do not have moving parts in their lumen, which can control the flow of fluid within the device, while complex NCs possess moving parts, such as a mechanical valve, to control the fluid flow in the device. Controlling the fluid flow inside the device could be in two ways: fluid displacement or fluid pathway.
In terms of fluid displacement, NCs can be classified as either negative, positive, or neutral. Suppose the NC has negative displacement when something is connected or disconnected or when an administration set is connected. In that case, the blood is allowed to move back or reflux into the catheter’s lumen. If the NC has positive displacement, it keeps a reservoir of fluid that will occupy the catheter’s lumen when an IV set or syringe is disconnected. In this case, blood is not allowed to move back or reflux into the catheter’s lumen. The reservoir of fluid overcomes the intraluminal pressure arising from the blood. Neutral displacement prevents the blood from occupying the catheter’s lumen when a connection or disconnection is made.
Considering that NCs vary in terms of displacements, there is a need to read the product information and instructions before using any particular NC. More often than not, if the NC has positive or neutral displacement, manufacturers of said products usually emphasize it in their labeling information. However, if the displacement is negative, manufacturers seldom discuss it. On some occasions, NC manufacturers mention “pressure” to mean positive displacement. To some extent, this implies that the device is generating a “pressure.” This is not so. It is a misnomer because no extra pressure is generated. Instead, the fluid which could reflux in the lumen of the catheter is pushed forward.
If the NCs have mechanical valves, and this mechanical valve has negative displacement, fluid flows through the centerpiece. If it has positive displacement, the fluid flow is split. Then It passes between the outer housing and the movable centerpiece.
Associated Risk Factors with the Use of NCs
The use of NCs is not free from risk factors. These risk factors could arise from the device design, user knowledge deficits, inattention to the management of the entire IV administration system, and the frequency of changing the connectors.
The use of split-septum needleless connectors is recommended over the device with mechanical valves. This is because the space between the external housing and the valve’s moving centerpiece could entrap microorganisms.
User knowledge deficits
Many healthcare workers are not aware of the proper cleaning and disinfecting NCs. They do not know when to use a particular type and design of NC.
Inattention to system management
Even if the connection surface of the NC is sterile and clean, if the male Luer end of the IV set or syringe is not, then the infection could still occur.
Frequency of changing the NCs and improper use of NCs
In a continuous infusion system, there might be no need to use NCs. The IV set needs to be luer-locked directly to the catheter hub without using NC. This is done to avoid frequent manipulation of the IV line and connections.