Episode #75 The Luer of Anesthesia Patient Safety, Part 2

Hello and welcome back to the Anesthesia Patient Safety Podcast.  My name is Alli Bechtel and I am your host. Thank you for joining us for another show. This week, we are going right back into the Rapid Response section of the October 2021 Newsletter. You could say that we have been “lured” into it!

Before we dive into the episode today, we’d like to recognize Fresenius Kabi, a major corporate supporter of APSF. Fresenius Kabi has generously provided unrestricted support to further our vision that “no one shall be harmed by anesthesia care”. Thank you, Fresenius Kabi – we wouldn’t be able to do all that we do without you!”

Last week, we discussed the case of “Air Entrainment by Extension Connectors to Central Venous Cather” in the article by Michael Kuntz and Alfonso Casta. This article highlights an important patient safety concern discovered by the authors when an intravenous line extension was connected to a central line, but the connection did not seal completely. Then, we discussed the response by Jeffrey Feldman who is the chair of the APSF Committee on Technology in his article with the clever title, “The ‘Luer’ of a Simple Device.” If you have not listened to episode #74 yet, we encourage you to go check it out.

There is still more to learn about this important piece of medical technology, the Luer Connector. For further information, we are going to return to the Rapid Response section of the October 2021 APSF Newsletter for our featured article today, “Managing Luer Connections” by Bruce Hansel who is the principal and chief scientist of Accident and Forensic Investigation of ECRI and this article stems from his experience over many years of medical accident investigation. So, head over to APSF.org and click on the newsletter heading. First one down is the current issue. Then scroll down until you see our featured article today.

The article opens with some history about the Luer device. Did you know that it was named after the German instrument maker, Hermann Luer. Luer devices were one of the first medical devices that created leak-free, continuous lumen connections between syringes and needles. We use this simple device every day and often take it for granted. The components for the device include mated fittings that are cone-shaped with a. 6% taper. Luer fittings are often made out of plastic, but glass or metal can also be used as well. When pressure is applied to device to create a connection, the inner wall presses against the outer wall of the taper leading to a leak-free connection. You will find Luer devices used for vascular access as well as enteral connections and pneumatic connections. Last week, we talked about the new standard, ISO 80369, which limits the standard Luer fitting to vascular use only. Another part of the new standard specific for intravascular connections is ISO 80369-7 which is related to the softness of the plastic so that the connection will not be altered under pressure. The new standards are an important step for patient safety to help prevent dangerous cross connections and leaking connections.

Next up, let’s review the different types of luer fittings. First, the Luer Slip is the originally designed luer taper fitting which requires applied pressure leading to friction between the opposing conical surfaces and a leak-free connection as long as the compression is maintained. When pulling forces are applied to the connection, the continuous lumen is not maintained leading to separation. In addition, when the taper surfaces are wet, this is a risk for accidental disconnection. Check out figure 1 in the article which shows this connection.

The next fitting is the Luer-lock which was designed to prevent the accidental separation that can occur with the luer slip fitting.  The Luer lock includes a threaded skirt on the male taper with flanges on the female taper that engage the threads when compressed together. As a result of the threaded coupling, the connection is maintained and cannot be pulled apart. The Luer lock has two separate fittings: The fixed skirt and the swivel skirt. The fixed skirt involves a single piece with the skirt and taper. For the swivel skirt design, the taper fit is first engaged and then secured with the swivel skirt, importantly without any twisting forces on the intravenous tubing. When engaging the fixed skirt luer device, twisting forces or torque must be applied to the IV tubing in order to secure the connection. For a visual representation of these designs, check out Figures 2 and 3 in the article.

Now that we understand these devices a little better, it’s time to figure out how misconnections occur…and how to keep our patients safe. There are a couple of important points that Hansel makes. First, the Luer-lock does not involve a locking or latching mechanism. Next, the skirt component does not contribute to additional leak protection. And finally, even though the luer lock does not easily pull apart, it may unscrew which separates the tapers leading to an unintended disconnection. Have you seen this in the OR when an extension has become disconnected from the IV line at the Luer lock connection? As =an example of this “Luer leverage,” the term used by the ECRI to describe this event, when a syringe is connected to a three-way Luer stopcock, the luer connection that is perpendicular to the syringe may be loosened when connecting the syringe. This is likely to happen because only a ¼ turn will separate the tapers and loose the connection. “Luer Leverage” events are a big threat to patient safety. In fact, there is a case report of a patient mortality following hemorrhage and air embolism after a central line sheath disconnection from a hemostasis valve with an integral 6 inch sideport connected to the sheath with a luer lock device. After placement of the central line, the sheath was secured to the patient’s skin at the hub which meant that the female hub was fixed in place and could not rotate. IV tubing was attached to the hemostasis valve on the side port of the sheath. The disconnection occurred from pulling on the IV tubing leading to torque on the luer lock and unintended disconnection. This is a call to action to remain vigilant with any Luer lock connections and be on the lookout for any unintended disconnections.

So, what are the complications that may arise from partial or complete disconnection of the Luer-lock device? Keep in mind that a partial disconnection may appear to have a leak-free seal and may be difficult to detect.

There are 4 major complications from a disconnection that may include:

1. Infection
2. Blood loss
3. Air embolism
4. Medication leakage

We are going to look closer at the complications of blood loss and air embolism which may occur when there is leak between the intravascular system and the atmosphere with a pressure gradient that determines which complication will occur, blood loss or air embolism. In addition, the severity of the complication depends on the magnitude of the pressure gradient, the resistance in the leak, and the length of the tubing. When the pressure in the lumen of the tube is greater than the ambient air pressure, this is a set up for blood loss through a leaking luer connection. When the pressure in the lumen of tube is lower than ambient air pressure, this is a set up for air embolism. Keep in mind that when pressure or a vacuum is applied to the tubing either with attached syringes or pumps and there is a luer disconnection, then the severity of the complication will be increased. The author provides the example of massive blood loss following inadvertent luer disconnection during hemodialysis.

So, now that we know some of the big threats to patient safety, how can we work to help keep patients safe when using Luer devices? Hansel offers some strategies with luer-lock connections and the Luer taper fitting.

The first step is making the connection. Important steps in this process include the following:

• Ensure that the Luer components are dry when making the connection. Dry fittings will be more secure than wet connections. However, it may not be possible to avoid having IV solutions or blood on the tapers or in the skirt. You can still create a secure connection even with wet fittings, but the connection must be made correctly and safely.
• Tighten the fittings on the connection by hand without the use of grasping instruments. The use of grasping instruments may lead to damaged fittings which are more likely to leak. You may need to use grasping instruments to separate luer fittings when the connection is tight and unable to be disconnected by hand twisting.
• Make Luer connections only between fittings made from the same material, such as plastic to plastic. There is a higher risk for leak with luer connections made from two different materials such as metal to plastic.
• Do not cross-thread the male Luer skirt threads on the lugs of the female taper. This is part of the design process with the male taper extending beyond the end of the threaded skirt so that the tapers can engage before the skirt and help to align the fittings. When you are using a swivel skirt design, it may be helpful to retract the skirt then make the taper connection that is correctly aligned.
• Only make connections when they are necessary for patient care. Increased connections lead toa. Higher risk for leak or unintended disconnection.

Next up, we are going to reviewing strategies for maintain luer connections and keeping patients safe.

• Make sure that there is no tension on the lines near any Luer connections that are attached to indwelling catheters.
• Organize the IV tubing lines to minimize the risk for snagging the lines on the patient and equipment, especially when you need to turn the patient. But this doesn’t mean to just add excess slack to the lines since this increases the risk for disconnection as well
• Avoid Luer leverage by minimizing the use of devices that extend perpendicularly from the adjacent Luer connections. Orient these devices so that if they are snagged or lines connected to them are pulled, they will not unscrew the adjacent Luer-lock.
• Unused Luer ports should be closed with solid (non-vented) Luer caps. Stopcocks and pinch clamps should not be relied on as the sole means of preventing leakage or air ingress at unused Luer fittings.

Finally, let’s talk about strategies for monitoring the connections.

• Avoid placing or using luer connections that you cannot monitor visually or have easy access to. Keep in the mind, that you will need to maintain visualization of the luer connections on any extracorporeal circulation equipment in order to avoid massive blood loss.
• Inspect the luer connection including the proximal and distal lines to the connection to make sure that there is no snagging or entrapment.
• Be on the lookout downstream of the luer connection for air in the tubing. If there is air distal to the luer connection, it is time to tighten and secure the connection while inspecting any additional upstream connectors as well.
• Another important consideration is the dressing that covers the IV tubing and the luer connection. When these dressings are clear, it makes it easier to assess for any sign of a leak such as blood or IV solutions.

We are almost out of time for today, but first, the authors leaves us with the final message that I am going to read now.

“Like any medical device, the potential for patient harm from a Luer connection can be reduced by understanding the design considerations, potential for injury, and strategies for proper use. Following the guidance provided here should reduce the potential for a Luer-related adverse event or outcome.”

If you have any questions or comments from today’s show, please email us at [email protected].

Visit APSF.org for detailed information and check out the show notes for links to all the topics we discussed today.  Please keep in mind that the information in this show is provided for informational purposes only and does not constitute medical or legal advice.

We hope that you will consider applying for the Joint APSF and Foundation of Anesthesia Education and Research Mentored Research Training Grant. This is an exciting opportunity for the next generation of perioperative patient safety scientists. This is a two-year, $300,000 award with a goal for anesthesiologists within 10 years of their first faculty appointment to develop skills and collect preliminary data to go on an become independent investigators in the field of anesthesia patient safety. The submission period is open now.

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Until next time, stay vigilant so that no one shall be harmed by anesthesia care.

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