Feature Article

A Noninterchangeable Connector for Central Venous Pressure Lines

Posted by Camilla Andersson on September 21, 2011

This article discusses a new type of connector designed to prevent the unintentional administration of drugs.

Errors in the route of administration of irritant and vasoconstrictor drugs continue to cause avoidable patient injury in hospital practice. Total parenteral nutrition is frequently given in the ward environment and must not be connected to anything but a central venous line. Commonly, a patient can have more than 10 luer connections around his or her bedspace, allowing access to many different routes. A typical critically ill patient has a multiple lumen central venous (CV) cannula, a number of peripheral venous cannulae (PC), an arterial line and a spinal or epidural catheter, all with the associated luer connectors. It is essential that lines carrying drugs intended for central line administration should not be able to be connected to any other luer connector, and it is also equally important that standard luer (male) connector infusions and syringes should continue to fit on a CV catheter.

Figure 1:  A conventional male luer.

In this article, we present a unique solution that retains the ability to use conventional luer connectors on the central access, but prevents the unintentional connections of those drugs that must only be administered centrally to peripheral luer connectors.

Because of the nature of general hospital and critical care interventions, lines are frequently disconnected, replaced or swapped. An unfortunate common error is to connect a line containing fluid that can only be given safely through a central vein (e.g. concentrated potassium chloride, TPN or vasoconstrictors) to a peripheral cannula, resulting in phlebitis or necrosis. This is painful and distressing for the patient and often leads to disciplinary action against staff. In certain circumstances it may even be fatal.

 Figure 2: A NICS CV infusion line with a male NICS connector.

The National Health Service (NHS) of the United Kingdom has identified the incorrect administration of concentrated potassium solutions as a “Never Event.”¹ Despite rigorous checking procedures and multiple system solutions, these errors continue to occur² because there is no engineered solution preventing the misconnection of a drug intended for central delivery to a peripheral cannula. The luer connection is ubiquitous to all intravenous devices whatever their route.

In 2006, the Joint Commission on Accreditation of Healthcare Organisations issued an alert highlighting the dangers of tubing misconnections.³  Similar problems have been identified in the NHS and other health services across Europe. Inadvertent connections of infusions intended for the central venous catheter to the peripheral cannula are possible because both carry identical luer connectors.

Unlike other routes (nasogastric and neuraxial), it is not possible to introduce a totally unique connector for central systems, as there is a requirement for the central system to accept standard luer infusion sets and luer syringes. This is necessary to enable the administration of emergency drugs in a timely way and to allow the central administration of those nonirritant drugs that can be given both centrally and peripherally. All drugs that can be delivered peripherally are safe for administration into CVC.

How the noninterchangeable connector system works
We present a risk-free, seamless solution to this problem—the noninterchangeable connector system. Two modifications are required. First, the CV catheter female luer connector would be altered in such a way that it would accept both the conventional luer syringes and infusion lines (see Figure 3) and also a new male noninterchangeable connector system (NICS) on lines that are intended only for central delivery (see Figure 2). The male NICS located on a CV infusion line would not connect to the luer connector on a PC (see Figure 2).

The NICS CVC has a NICS female connector with four projections, each with a circumferential dimension equal to that on the lip of the standard luer connectors. This allows it to connect to both standard luer and NICS infusion lines and syringes. The NICS CV infusion line has a male NICS connector with a corresponding disc that has a key structure, allowing the engagement of the four projections of the NICS CV catheter. This disc would prevent engagement with the standard female luer connector on a peripheral cannula (see Figure 2).

The female NICS connector on the CV catheter still allows access with standard syringes/infusion lines (Figure 4), allowing safe introduction of the NICS system.

Prototype NICS study

 Table 1: This table presents the results of a study measuring the ease of use of the NIC connector. Participants were able to complete all connections except the connection between the male NICS and a female luer, which none of the clinicians were able to connect.

We have carried out a study of the use of the prototype NICS in our hospital, aiming to prove that the NICS would prevent central to peripheral misconnection and that it allows the connection of standard luer infusions and syringes to the CVC. The primary outcome measure was the ability to connect NICS infusion to NIC CVC but not to a PC and the ability to connect standard luer infusion to both PC and NIC CVC.

We used a visual analogue scale (VAS) (a 10-cm line anchored with the statements very easy and very difficult) to measure the ease of use. We also measured the time taken for connection of NIC-NIC versus standard luer-PC.

Clinicians (n=66) were timed making NIC and standard luer connections and were asked to complete a questionnaire with a VAS for ease of use of the standard luer and NICS connectors.

All connections were successfully completed, except the connection between the male NICS and a female luer, which none of the clinicians were able to connect. The connection success results are presented in table 1.

The mean VAS for the luer connector was 0.34 cm of 10 cm compared with 1.13 cm of 10 cm for the NICS. The mean time to connect the luer-lock was 1.22 seconds compared with 1.7 seconds for the NICS. Whilst statistically significant, this time difference is clinically irrelevant.

Safety considerations

Figure 3: A conventional female luer.

It is important that additional risks are not introduced when new systems are placed into a healthcare environment to prevent rare complications. Simple calculations indicate that there are many thousands or millions of luer connector interactions for each episode of significant patient harm associated with CV infusion misconnection. Any system must therefore introduce zero risk to each of these normal connections. Ideally the teaching of staff should be minimal and they would not need any understanding of the system.

A previous study of 52 intensive care nurses surveyed following the introduction of the NIC air connector (a nonindexed NIC) into clinical practice showed that, although routinely using NICS, none were aware of a change and only became aware once they were asked to attempt a misconnection.

Figure 4: A NICS female connector.

There are several market drivers for the introduction of a NIC system. In addition to patient safety benefits, the system would potentially benefit pharmaceutical companies. First, by providing concentrated potassium solutions, TPN and vasoconstrictor agents in an infusion system that ends in the NIC, the pharmaceutical companies would be able to prevent the misadministration of these drugs into peripheral cannulae. This would allow drug manufacturers to distribute their preparation as a safer alternative to other generic drugs. The NHS Never Event would truly become a never event, as it would now be impossible to misconnect the concentrated potassium solution to a peripheral cannula.

There would also be commercial viability for the manufacturers of CVC and peripherally inserted CVC lines. It would be possible to introduce the new safe NIC CVC without any need to retrain clinicians or even letting them know that there had been an alteration.

In conclusion, engineered solutions to infusion misconnection problems are needed. No additional risk should be introduced with any new system. The NICS offers such a solution. Our studies have demonstrated that the system would be effective at preventing these tragic errors.

Conflict of interest: Dr Young holds a patent (pending) for the NIC system.

1.     Never Events Framework 2009/10, NHS, London, UK (2009).
2.     NHS National Patient Safety Agency, Never Events Annual Report 2009/10 (2010).
3.     “Tubing Misconnections−a Persistent and Potentially Deadly Occurrence,” [online] Sentinel Event Alert, (2006), available from Internet: http://www.jointcommission.org/sentinel_event_alert_issue_36_tubing_misc....
4.     J.L. Chen, M. O’Shea, “Extravasation Injury Associated with Low-Dose Dopamine,” The Annals Of Pharmacotherapy, 32, 5, 545-548 (1998).
5.     L.A. Evans, P.J. Young, “Preventing Iatrogenic Air Embolism in the Intensive Care Unit,” Medical Device Technology, 8, 3, 36-37 (2007).


Joseph Carter
is Consultant Anaesthetist,
Dr Ramai Santhirapala
is Critical Care Trainee,
Elizabeth Prince
is Critical Care Research Coordinator and
Dr Peter Young
is Consultant Anaesthetist at the Queen Elizabeth Hospital, King’s Lynn, PE30 4ET, UK
tel: +44 1553 613 613
joseph.carter@qehkl.nhs.uk  |  www.qehkl.nhs.uk
Dr Ajay Arora
is Consultant Anaesthetist
at the Norfolk and Norwich University Hospital, Norwich, UK

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