Ian Poxon, RGN.
Clinical Procurement Specialist, Supplies Department, Queen’s Medical Centre, Nottingham, University Hospitals NHS Trust
Volumetric infusion pumps (VIPs) are generally used to deliver large volumes of fluid at medium to high flow rates, but can also ‘deliver fluids at slower more precise rates than manually operated gravity flow controllers’ (Beaumont, 1995; Cowan, 1997).
These devices have been used for many years but, as with the use of many other types of medical equipment, ‘there has been an emphasis shift, whereby many device functions have moved away from being one of supporting clinical practice to that of being an integral requirement in treatment delivery’ (Quinn, 1998).
VIP devices generally fall into two categories: peristaltic and cassette mechanisms.
Peristaltic mechanisms - These can be linear or rotary. Both types consist of fingers, rollers or cams that rotate or move, thereby pinching off a section of a giving set and propelling the volume of fluid forward towards the patient.
The linear mechanism is the most common. With both types, the volume delivered is governed by the size of the fingers, rollers or cams, the giving set used and the speed with which the mechanism moves.
Cassette mechanisms - These are dedicated giving sets that contain a cassette unit. Housed within this is a small cylinder, piston and valve assembly. The speed with which the motor drives the piston governs how much fluid is propelled towards the patient.
The complex nature of VIPs meant that initially they were used predominantly ‘for the delivery of drugs such as dopamine in critically ill patients’ (Lorenz, 1990).
In the past 10 years, the use of VIPs has increased, and these devices are now used in all areas of health care to deliver maintenance fluids, as well as blood transfusions and total parenteral nutrition (TPN).
As the technology has improved, so the range of VIP models available commercially has increased. Devices have become smaller and lighter, while including an ever-increasing number of technical features. A National Patient Safety Agency (NPSA) pilot study into improving infusion device safety found that trusts had ’a wider range of infusion device types than they need and too many with a higher specification than is necessary (NPSA, 2004).
Hospitals/trusts must consider a number of issues when deciding which devices to purchase. The Department of Health controls assurance standards for medical device management highlight the need to have in place systems that minimise the risks associated with using medical devices (DH, 2003).
Rationalisation of the makes and models of VIPs within each trust is essential, so it is crucial that they consider the following when making a decision on which device(s) to purchase:
- The areas where the devices will be used. Specialist areas such as neonatal care will require devices with different specifications to those used in adults areas
- The people who are to use the device: if it is to be used in a patient’s home, it will be necessary to address the question of who will provide support to the patient
- The optimum range of devices likely to be needed, both in terms of makes and models. Specification of VIPs can be guided by the therapy categories and performance parameters such as those set out by the Medical and Healthcare Products Agency (MHRA) (2003) (Table 1)
- The supplier/manufacturer of the device. If a single supplier/manufacturer is chosen, what are the potential risks of putting all your eggs in one basket?
- The cost implications. Not only is the cost of a VIP substantial, but the disposable giving sets required for the equipment can also be costly, as these are specific to particular manufacturers’ devices
- What are the supply route implications of using these dedicated sets? Can stock levels be controlled and maintained to cover peaks and troughs in usage?
- The training requirements: not only will training be necessary for clinical staff, but also for carers in the community and staff in the electro-bio-medical engineering (EBME) departments that may be charged with servicing or maintaining these devices
- Ongoing training and assessment
- Where the VIP devices are to be stored
- The trust’s future requirements for using VIPs will also need to be be considered. Will changes in clinical practice affect usage?
Fifteen million infusions are performed every year in the NHS, with 700 unsafe incidents reported, of which 19% are attributed to user error (NPSA, 2004). In addition, about 60-65% of infusion devices are idle for the majority of the time (Quinn, 1998; NPSA, 2004).
To ensure the optimal and safe use of VIP devices, several NHS trusts have therefore set up medical equipment libraries. These are dedicated not only to controlling the purchasing, storage and maintenance of equipment, but also to training staff in the correct use of VIPs.
The concept of equipment libraries is consequently seen by the Department of Health, MHRA and NPSA as a vital necessity, along with the formation of broad-based medical devices groups and the appointment or designation of a medical devices co-ordinator to oversee and report all issues relating to medical devices (MHRA, 2003).
The NPSA (2004) has developed a toolkit to assist trusts in reviewing their device management systems, as well as to help them assess the potential for significant cost benefits and improved patient safety.
The toolkit can be found on the NHS Purchasing and Supply Agency website, at www.pasa.nhs.uk/infusiondevices.
What do volumetric pumps offer?
VIPs are versatile and sophisticated pieces of equipment that can be mains and/or battery operated. They have a high degree of accuracy, with most pumps guaranteed to be accurate to within 10%, which is adequate in the majority of situations. However, in neonatal or critical care areas accuracy must be within 5% (Lorenz, 1990; Cowan, 1997).
VIPs can generally deliver flow rates of 1.0-999.0ml/hour; some pumps can be configured to deliver 0.1-99.9ml/hour for use with neonatal patients.
The display of VIP data - for example, on whether the pump is working, the flow rate, the volume to be delivered, the volume delivered and the time remaining for the infusion - is generally displayed numerically, but this can sometimes be displayed graphically. Other technical data stored in a device’s memory log can be obtained via a computer interface, to enable incident analysis for example, with some devices able to record the settings and alarms for two days, or a thousand data points (MHRA, 2003).
It is advantageous to use VIPs that have tamper-resistant controls or lockout mechanisms, to increase safety and security. Some devices also contain pre-programmed drug delivery regimens and calculators, which use body surface area to calculate the correct dosage/rate.
Most devices will automatically trigger an alarm and shut down when one of the following occurs:
- Air is detected in the giving set
- An occlusion is detected
- The fluid container is empty.
All VIPs use positive pressure to deliver fluid, so should an occlusion occur, the fluids or drugs will stop being infused. An increase in pressure may lead to extravasation occurring in the tissue around the cannula and the risk of administration of a large bolus. To prevent this happening, VIPs have preset occlusion pressure settings, which specify the maximum upward adjustment a device can make to overcome the resistance to flow before the alarm is triggered (Cowan, 1997).
Most devices have a ‘keep vein open’ facility, to maintain the patency of the vascular-access device once the infusion is complete, and some provide automatic priming of the giving set.
The majority of VIPs require dedicated giving sets - this is essential for the accurate delivery of fluids to the patient and the optimal operation of the devices sensors.
The incorrect use of sets can cause:
- Underinfusion if the set diameter is too small
- Free flow - if the set is too large
- Rupture of the set - if the materials cannot withstand the wear and tear of the pump.
The use of the wrong type of set can result in the inactivation of air-in-line detectors and occlusion pressure sensors.
The health-care professional responsible for monitoring the patient should be accountable for the use of electronic flow-control infusion devices (RCN, 2003).
The user should demonstrate knowledge and competency in the use of a particular infusion device. A user’s assessment of competence should include the indications for use, ability to programme the device in order to deliver a prescribed therapy, mechanical operation, the use of lock-out safety devices, trouble shooting, knowledge of its pounds per square inch (PSI) rating, the recommended height for setting up the device and its safe use and monitoring (RCN, 2003; MDA, 2000; Quinn, 2000; MHRA, 2003).
Some trusts employ dedicated trainers in their equipment libraries. Many take the need to train staff further by making information about training and devices available on EBME websites and via trust magazines as a product of the month. This provides easy-to-find and easy-to-use information, which supports staff in their use of the equipment.
An example of the seriousness that NHS trusts accord staff training and support in using VIP devices can be seen at the Medical Equipment Service Unit at Queen’s Medical Centre, Nottingham (this is available at: www.qmc.nhs.uk/divisions/diagnostics/mesu).
It is vital for trusts to ensure that any VIP devices they purchase are appropriate for the needs of the patient groups they serve. It also important to train staff in the correct use, storage and maintenance of such devices, and to offer regular ongoing assessment.
Cost is also an important issue, and trusts that set up equipment libraries are better able to not only manage the use of the devices but also to equip staff with the skills necessary to ensure that VIPs are used appropriately and safely, thus minimising the risks to both staff and patients.
Author contact details
Ian Poxon, Clinical Procurement Specialist, Supplies Department, Curie Court, Queens Medical Centre Nottingham, Clifton Boulevard, Nottingham N57 2UH; email: email@example.com
KEY POINTS FOR CONSIDERATION
In the clinical area
Is a pump necessary?
- What types of fluids are to be given? - Will a gravity infusion suffice?
Is a pump available? - Are sufficient devices available?
Do the staff/carers understand the device?
- Has competency-based training been undertaken?
Are the right disposables available?
- Many VIPs need dedicated giving sets
At trust level
Where will the device be used?
- Hospital or community setting?
Where are these pumps kept?
- A cupboard in individual area or medical equipment library? Are the devices adequately maintained?
- In-house or by the supplier?
Who controls the purchasing?
- Can areas purchase any product they require
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