The “Luer” of a Simple Device

Jeffrey M. Feldman, MD, MSE

Luer connectors are ubiquitous in patient care and generally serve the purpose for which they were designed—to allow caregivers to quickly make a leak-free connection and maintain a continuous lumen. The success of this basic design is evidenced by the multitude of different devices that use this same basic connection and continue to be used daily.1 We have known for many years however, that this simple connector can lead to patient injury due to leaks or disconnections and when devices intended for different purposes are inadvertently interconnected, e.g., connecting a vascular infusion to an epidural catheter.2 New designs for preventing misconnections have been available for more than a decade. As a formal response: ISO 80369 is a seven-part standard that “provides the methodology to assess non-interconnectable characteristics of small-bore connectors based on their inherent design and dimensions in order to reduce the risk of misconnections between medical devices or between accessories for different applications.”3 Despite efforts to implement the ISO 80369 standards to prevent misconnections, widespread adoption has yet to be realized.4,5 Part 7 of the standard pertains to connectors for intravascular or hypodermic applications and adopts the current luer fitting for those connections The new standard does not alter the basic design of using a tapered fitting to create a leak-free connection so strategies for making a secure connection are germane to all of the new connectors.

In this issue of the newsletter, Michael Kuntz, MD, and Alfonso Casta, MD, from Boston Children’s Hospital report an experience where presumably compatible luer connectors allowed air to be entrained into the vascular tubing when a syringe was used to aspirate and check the connection. After trying different tubing sets to make the connection, all fitted with a “standard” Luer connection, they identified a combination that eliminated the air entrainment. This report raises questions about the consistency of manufacturing these connectors and the potential for misfit despite adherence to the basic standard. Whether their experience is due to variations in manufacturing the actual device, a weakness in the standard, or extreme conditions of negative pressure outside of the specification for testing for air leaks, it is impossible to know for certain. It is interesting to note that the two connectors that were associated with air entrainment were “fixed-skirt” luer connectors whereas the tight connection was obtained with a “swivel-skirt.” More on the details of these two types of luer-lock connectors is in the article by Bruce Hansel, PhD. Fixed-skirt connectors have the potential to engage and cause a twisting force (torque) on the tubing attached to each component, whereas swivel-skirt connectors can be engaged without exerting torque on the connection.

The original standard for the Luer connection, ISO-594, consists of two parts, Part One: General Requirements and Part Two: Lock Fittings. The general requirements describe the tolerances for all of the dimensions of the basic Luer fitting along with procedures for gauging (sizing) the components, and testing for leak of air and fluids, separation force, and stress cracking.6,7 Manufacturers have their components tested to ensure that they comply with the standards’ requirements so that interconnection between all devices adherent to the standard is possible. The new standard for intravascular connectors, ISO 80369-7, essentially follows the original standard with some new limitations on the material properties and more stringent requirements for the precision of the dimensions intended to foster more secure connections. Connectors compliant with ISO 80369-7 should be backwards compatible with connectors compliant with ISO 594, but not necessarily vice versa.

To best understand how to use Luer connectors safely, we are fortunate to have commentary from Bruce C. Hansel, PhD, CCE, Principal & Chief Scientist, Accident and Forensic Investigation for ECRI Institute, with a focus on vascular connectors. Bruce Hansel has investigated patient injuries related to Luer connectors and provides an educational commentary on the Luer design as well as use strategies to mitigate the potential for patient harm. While we do not have enough information to identify what differences, if any, exist between different manufacturers of Luer designs that can contribute to a less than secure connection, Hansel provides valuable insights into how the Luer connection can be used to greatest effect.

The Luer connector is so simple to use, it is easy to be “lured” into thinking that it does not matter how we make the connection. While we are likely to see slow but progressive adoption of the new standard for preventing misconnection between incompatible applications, the basic use of a tapered connector will continue, especially for vascular access. Proper use can help to minimize leaks and disconnects that can lead to patient injury.


Jeffrey M. Feldman, MD, MSE, is chair or the APSF Committee on Technology, professor of Clinical Anesthesiology, Children’s Hospital of Philadelphia, Perelman School of Medicine– University of Pennsylvania.

Jeffrey Feldman is a consultant for Micropore Inc. and Becton Dickinson.


  1. Brown J. The life and death of the luer. Accessed July 11, 2021.
  2. Sentinel Event Alert. Managing risk during transition to new ISO tubing connector standards. 2014;53:1–6. Accessed Aug 29 2021.
  3. ISO 80369-1:2018 Small-bore connectors for liquids and gases in healthcare applications—Part 1: General requirement. Accessed July 11, 2021.
  4. Logan M, Hancock T. Improving patient safety: collaboration, innovation, connection: organization provides information on new connector ISO standards. APSF Newsletter. 2014;29:15–16. Accessed August 11, 2021.
  5. Sentinel Event Alert 53: Managing risk during transition to new ISO tubing connector. Accessed July 11, 2021.
  6. Conical fittings with a 6% (Luer) taper for syringes, needles and certain other medical equipment—Part 1: General Requirements. ISO 594/1–1986.
  7. Conical fittings with a 6% (Luer) taper for syringes, needles and certain other medical equipment—Part 2: Lock Fittings. ISO 594/1-1986.

The information provided is for safety-related educational purposes only, and does not constitute medical or legal advice. Individual or group responses are only commentary, provided for purposes of education or discussion, and are neither statements of advice nor the opinions of APSF. It is not the intention of APSF to provide specific medical or legal advice or to endorse any specific views or recommendations in response to the inquiries posted. In no event shall APSF be responsible or liable, directly or indirectly, for any damage or loss caused or alleged to be caused by or in connection with the reliance on any such information.

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