Table of Contents

Priming Filter Cap

cap with filter


Priming filter cap is a part of the IV set. Its primary function is to cover the end of an intravenous (IV) line, which is not attached to a catheter or a needle. It prevents the flow and spillage of the intravenous fluid to the outside environment. But it allows the passage of air that has been entrapped in the intravenous line or tubing.

plastic cap with air filter
Priming filter cap

Functions and Uses of Priming Filter Cap

  • As part of the IV set, it covers the distal end of the intravenous line or tubing, which is otherwise open and unprotected when it is not attached to a catheter or a needle;
  • Priming filter cap prevents the flow of intravenous fluid to the outside environment. But it allows the passage of air that has been entrapped in the intravenous tubing;
  • It prevents the entry of debris and disease-causing microorganisms through the open distal end of the intravenous line, minimizing infections.

Relevant Clinical Studies

Supportive of the Use of Priming Cap

“Capping Intravenous Tubing and Disinfecting Intravenous Ports Reduce Risks of Infection”

Based on the study conducted by Matthew Grissinger titled “Capping Intravenous Tubing and Disinfecting Intravenous Ports Reduce Risks of Infection” and published in the National Center for Biotechnology Information (NCBI) journal in February 2011, it was found that (1) medication errors and (2) healthcare-associated infections (HAIs) still top the list of problems that have been endangering the patients’ safety. Supportive of these findings, the Center for Disease Control and Prevention (CDC) cited HAIs as one of the top 10 primary causes of death in the U.S. In 2006, HAIs caused an estimated 1.7 million infections in hospitals, 99,000 associated deaths, and $4.5 billion in added patient care cost each year.

The risks of infections are increased when the medical staff—nurses and doctors—do not practice and maintain aseptic techniques in preparing and administering injectable drugs and solutions. The Institute for Safe Medication Practices (ISMP) revealed that hepatitis outbreaks and other infectious diseases took place because of improper use of syringes and multiple-dose vials.

However, from all possible causes, two medical practices were cited as perennial causes of infections: (1) The failure to use a sterile cap at the end of the reusable intravenous administration set. While temporarily removed, the tubing was left hanging while not in use. If this was done without covering the end of the tubing, contaminants, and microorganisms could cause diseases to enter the bloodstream when the said tubing is reconnected to the patient. (2) The failure to adequately sterilize the injection port when injecting medications. While not in use, this port is exposed to possible causes of infections, and re-using it as the site of injecting drugs will seed and introduce infections in the bloodstream.

We could primarily prevent the risks of infections coming and entering through the end of an open IV tubing if priming filter cap is placed over the opening.

The Fatality Analysis Reporting System (FARSO)

The Fatality Analysis Reporting System (FARSO) reported in 1999 that 88,000 deaths took place among two million patients who developed hospital-acquired infections or nosocomial infections. Out of these 2,000,000 nosocomial infections, 850,000 were classified as catheter-associated infections (CAIs). Of the 850,000 infections, 50,000 infections were considered as catheter-associated bacteremias (CABs), which could arise from central IV catheters. The case fatality rate of CABs is very high. More than 20% (10,000 deaths for every 50,000 cases) died from CABs.

It was reported in the same article that the primary origin of most disease-causing microorganisms were the catheter insertion sites or the catheter hubs. The report did not mention the possible reasons why the catheter hubs or insertion sites were the primary entrance of disease-causing microorganisms. Still, it can be surmised that some—if not many—were due to unprotected ends of IV tubes. We could have prevented these deaths and added expenditures if we had adequately protected the ends of IV tubes with priming filter caps.

Based on, the following were the rates of infections based on the sites: (1) 33-45% took place in needleless connector hubs, (2) 37% in male Luer, (3) 50% in catheter hubs, (4) no specific rate was mentioned, but 3-way stopcocks could be the source of the significant and independent risk factor for catheter-related bloodstream infections.

If we add the rates of contaminations from both the male Luer and catheter hubs, it sums up to around 87%. If all of these were protected with priming filter caps, the contamination rates could have been reduced by at least 50%. 

“Disinfection of Needleless Connector Hubs: Clinical Evidence Systematic Review”

Based on the study of Nancy L. Moureau and Julie Flynn titled “Disinfection of Needleless Connector Hubs: Clinical Evidence Systematic Review,” which was published in the Nursing Research Practice Journal on May 14, 2015, we find that there will be a significant reduction in the infection rates by 48-86% if passive alcohol disinfection caps are used. This means that if the priming filter cap is provided with additional passive alcohol disinfection, there will be a significant infection rate reduction.

Capping Your IV Line

If you are using an individual IV line for the day and you need to infuse on more than one occasion on the same day, you may use the same tubing if the medication that you are infusing is the same. If you infuse different kinds of drugs, you need to use the other tubing for each one. If you are infusing any fluid without interruptions—that is, continuously—you can use the same tubing for up to 72 hours. However, if your infusion is interrupted within the same day—that is, you stopped the infusion for some time—the tubing must not be used for more than 24 hours. If you are infusing total parenteral nutrition (TPN), you need to change the tubing with every bag. Ideally, change the tubing every 24 hours.

infusion set with cap
Infusion set with cap

If you need to interrupt your infusion and you plan to use the same tubing, you must keep the end of the tubing clean, sterile, and free from possible contaminants. You can do this if you use the cap with the filter to plug the tip of the tubing. The tip of the tubing, even if already plugged, must not touch anything else.

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Infusion Set with Auto Air Stop and Priming Cap


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