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Published on 1 May 2007

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The use of prefilled syringes in CT contrast administration

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Frank Ellwood
DCR(R) DMU
CT Superintendent Radiographer
X-Ray Department
Derriford Hospital
Plymouth
UK
E: Frank.Ellwood@phnt.swest.nhs.uk

Computed tomography (CT) has seen rapid advances in scanner hardware and software in the last ten years. As scanning times have been reduced to a few seconds the ability to scan with intravenous (IV) contrast media at specific vascular phases has become routine. Power injectors give consistent control of bolus timing and flow rate. For CT scans of the neck, thorax, abdomen and pelvis, over 90% of the protocols include administration of IV contrast media using a power injector.

The traditional method of preparing the injector for use involves the use of empty syringes which are filled from a bottle immediately prior to use. In the UK, one manufacturer, Tyco Healthcare, Mallinckrodt, produces prefilled syringes of varying concentrations and volumes of contrast media.

At Derriford Hospital in Plymouth we have three multidetector CT scanners. During a normal working day we will use 50-60 prefilled syringes. The radiographers operating the scanners are dedicated CT radiographers, spending at least 80% of their working time in CT, and are responsible for the safe and efficient administration of IV contrast media.

As a group radiographers have been strongly supportive of the use of prefilled syringes because of the many advantages that these syringes provide. Our views closely mirror a survey, carried out in the USA in 2001, of the views of radiological technologists on the value of prefilled syringes.(1) In this study the major perceived benefits of using prefilled syringes were listed, in order of importance, as:
1) Quicker use (efficiency).
2) Cost-effectivenes.
3) Quality of patient care.
4) Safety.
5) Sterility.

Efficiency
The perceived increase in efficiency manifested itself in two ways. First prefilled syringes are quicker to use and reduce the turnaround time between patients. As a department we are under pressure to increase patient throughput – usually with no corresponding increase in staff. Secondly, the time saved by not having to set up the injector can be spent with the patient prior to the scan. If we understand the fears and worries of patients we can reassure them and explain clearly what will happen during the scan.

A time and motion study of contrast-loading, CT exam set-up, scan and clean-up times was undertaken in 2002 in four North American hospitals.(2) Prefilled syringes were compared with bottle-filled syringes, and the survey demonstrated that the use of the former resulted in an average improvement of 10% in set-up efficiency. Set-up is defined as the time taken from the moment the patient enters the room to the initiation of the scan. When the time taken for contrast loading of the injector was taken into consideration, time saving was 33% for this part of the procedure. It was noted in this survey that the participating centres had only recently started using prefilled syringes and that, in time, these figures would be even more impressive.

Cost
It is difficult to be specific when comparing costs of one system with another, as most companies producing contrast media will provide discounts, depending on the volume used. One pitfall in comparing the systems is to look simply at the cost per volume of contrast medium itself and not allowing for the separate purchase of a syringe in the bottlefilling system. The syringes used are specific, as they need to withstand the pressure generated by the injector, and will typically cost £6-8 each. Syringes that have been bottle-filled and are not used because, for example, the patient failed to attend, will be discarded at the end of the session.

One argument against prefilled syringes is that the volume in the syringe is predetermined and cannot be altered to suit individual exams, as is the case with bottle-filled syringes. However, with 50, 75, 100 and 125 ml syringes available, there is a reasonable amount of choice to suit most applications.

Quality of patient care
This is an area that is difficult to quantify. The views of the radiographers at Derriford Hospital echo the findings of the US survey,(1) which indicated that 61% of respondents felt that patient care had improved with the use of prefilled syringes, while 39% felt that the quality of care had not changed. The perception of better quality of patient care appears to stem from an amalgamation of positive outcomes including efficiency, sterility and safety. In our centre the added bonus is that the morale of the radiographers has increased, as they became confident that they are using best practice with this method of contrast administration.

Safety
There have been several recorded instances in which intravascular air emboli have occurred with the use of automatic contrast media injectors. The use of prefilled syringes has a positive impact on reducing the risk of such incidents, as the syringe introduced into the injector is already full of contrast media. With the bottle-filled system it is possible to fill an empty syringe with air and subsequently inject this into the patient. Additionally there is a risk of generating air bubbles in the syringe as a consequence of rapid aspiration of contrast from a bottle into the syringe. With both systems the risk of air emboli is reduced by purging the air through the connecting line prior to injection.

Sterility
There are many steps involved in the filling of a syringe from a bottle and the risk of contamination at each of these stages is one that should be taken into consideration. With a prefilled syringe the syringe is removed from the pack, placed on the injector, the plastic cap is removed and the connecting line is placed on the syringe. Thus, there are far fewer chances of contamination and spillage on the operator or the surrounding area.

Conclusion
There are several significant advantages to the use of prefilled syringes for administration of CT contrast media, both for patients and for radiographers.

Recently a well-known manufacturer of power injectors has commissioned a survey asking for respondent’s views on prefilled syringes. The results seem to indicate that in the future prefilled syringes will have a bigger share of the market.

References

  1. Femano PA. The use of prefilled syringes in CT contrast administration: a research report. Albuquerque, NM, USA: American Society of Radiologic Technologists; 2001.
  2. Enterline DS. A multicenter time efficiency trial: examining prefilled syringes versus bottle filled cartridges for contrast enhanced CT examinations. Decisions in Imaging Economics 2003.


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