Know your connectors….

…the devices that allow connections of infusion sets and catheter hubs. Unless you have been living under a rock, no one should be using needles to make that connection, thus the term…needleless connectors.

In a previous blog, I posted about an FDA Alert on Positive Displacement Needleless Connectors . After I did, I realized that perhaps it would be helpful to describe and differentiate some terms often used with these devices. So here’s it is…

Negative Fluid Displacement – many of the connectors have fluid inside the device either from an IV solution or flush solution. The connectors allow for negative fluid displacement, which means that blood will be pulled back into the catheter lumen and this occurs while the IV administration set is connected, when fluid container is empty and IV set remains connected, or when IV set or syringe is disconnected (blood reflux). When blood is allowed to stay inside the lumen of the catheter, this can lead to catheter occlusion.

Positive Fluid Displacement – connectors with mechanical valves are designed to produce a positive fluid displacement upon disconnection of the IV set or syringe. Upon disconnection, the fluid in the valve is pushed out to the catheter lumen to remove the blood that has refluxed. Blood can still move into the catheter tip but the displacement valve prevents blood from staying inside and causing occlusion.

Neutral Fluid Displacement – some connectors are considered neutral because the device prevents blood reflux upon connection and disconnection of IV sets or syringe. Many argue that neutral doesn’t exist and the device still exhibit some degree of blood reflux into the catheter lumen.

These connectors do not generate “pressure”  or “force” during fluid movement. For more information on Needleless Connectors, read the reference article cited below.


Hadaway L. Richardson D. Needleless Connectors: A Primer on Terminology. Journal of Infusion Nursing: January/February 2010 – Volume 33 – Issue 1 – p 22–31

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2 thoughts on “Know your connectors….

  1. for information on further care of connectors of all types see an article by chernecky et al in CJON and one by Macklin in Seminars on oncology, they are very helpful. if anyone wants to know of their connector has reflux just use dye or jello works too. also there are several scientific and research papers out there too to help.

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