Safe practice in syringe pump management

Introduction

Syringe pumps are used as part of palliative care to administer medicines subcutaneously to patients who are unable to manage or tolerate oral medication. Ambulatory syringe pumps are portable battery-operated devices for delivering medication by continuous subcutaneous infusion (CSCI) over a given time period (usually 24 hours). They are useful when small volumes of drugs need to be infused at a slow rate (Dougherty and Lister, 2011), and their compact design enables patients to move around and maintain independence (Costello et al, 2008). The pumps are simple to operate, but training is essential.

Patients, carers and health professionals often wrongly associated syringe pumps with imminent death (Graham and Clarke, 2005), but the devices may be used at any time in the care pathway to control symptoms where drugs cannot be administered orally, such as in patients with intractable nausea and vomiting (Costello, 2008; Dickman et al, 2005) - Box 1 lists indications for their use. It is therefore important when starting a pump to offer patients and their families reassurance and explain the need for the syringe pump (Costello, 2008).

Continuous subcutaneous infusion maintains a constant serum level of medicines (Barnes et al, 2009), which achieves better symptom control than intermittent dosing. It also reduces the need to use less popular routes of administration such as rectal or intravenous (Morgan and Evans, 2004). Box 2 lists the advantages and disadvantages of CSCI.

Selecting syringe pumps

Several models of syringe pump are available. The most commonly used in the UK until recently were the Smiths Medical (formerly Sims Graseby) MS16A and MS26 (Costello et al, 2008). Although the flow rate in both devices is determined by how far the syringe moves in millimetres (mm), there are critical differences between the two. The MS16A is calibrated in mm/hr while the MS26 is calibrated in mm/24hrs, and errors - some fatal - have been reported when confusion has arisen during their use. As a result, the National Patient Safety Agency (2010) published a rapid response report advising all healthcare organisations using ambulatory syringe pumps to change to devices with the following features:

• Rate settings in millilitres (ml) per hour;
• Mechanism to stop infusion if syringe is not properly and securely fitted;
• Alarms that activate if syringe is removed before the infusion is stopped;
• Provision of internal log memory to record pump activity.

Standardisation of a single syringe pump model, centralised purchase and storage of equipment, scheduled regular maintenance and appropriate training in the use of syringe pumps across a locality has been suggested as effective means of error reduction (Dickman et al, 2005; NPSA, 2004). In our locality the CME McKinley T34 syringe pump was procured because it met the requirements listed above and has additional safety features; for example, the infusion rate cannot be altered once the device is infusing, and the device has a syringe size detector (NPSA, 2008).

There are other syringe pumps in use, including Eden Medical’s MP Daily, and Cardinal Health AD. These also offer all the safety features expected from current infusion pumps. However, this article focuses on the McKinley device as it is used widely across the NHS.

Using syringe pumps

All staff must receive training before using a syringe pump, and be familiar with local policies and procedures. It is important to discuss the procedure with the patient and follow local medicines administration policies at all times including checking drugs, compatibility and the patient’s identity.

Preparing the syringe

Manufacturers recommend the size of syringe that should be used with their devices. Pumps are calibrated in ml per hour, and it is important to establish what final volume is required in the syringe, then choose a syringe size. The prescribed medication should be drawn up first and then diluent added to the appropriate volume.

Medications, diluents and compatibility

Drugs in syringe pumps are generally prepared with a diluent - commonly water for injections, or sodium chloride 0.9% (Flowers and McLeod, 2005). This dilutes the medicine to minimise site reactions and enables it to be given over a set period. The diluent used should be compatible with the medicine. Information on suitable diluents can be obtained here, manufacturers’ literature, local clinical information or a pharmacist.

If a patient needs more than one medicine for symptom control, the medicines need to be compatible with the diluent and with each other. If compatibility is an issue, two syringe pumps may be required. Diamorphine can be given by subcutaneous infusion in strengths of up to 250mg/ml. Up to strength of 40mg/ml, both water for injections or sodium chloride 0.9% are suitable diluents, but above this strength only water for injections is used to avoid precipitation (Barnes et al, 2009).

Examples of common medicines that can be mixed with diamorphine or morphine in palliative and end-of-life care include: cyclizine, dexamethasone, haloperidol, hyoscine butylbromide, levomepromazine, metoclopramide, midazolam (British Medical Association and Royal Pharmaceutical Society for Great Britain, 2014). A drug additive label should be completed according to local policy and attached to the syringe to identify:

• The drugs added;
• The diluent;
• Time and date the infusion started;
• Patient’s name;
• Name and signature of the person starting the infusion.

When drugs are drawn up the fluid in the syringe should be inspected for any discoloration or precipitate which may indicate incompatibility (Dougherty and Lister, 2011).

Setting up an infusion

The battery power should be checked before starting the infusion; the average battery life is approximately three to four days, depending on use. If the remaining battery power is less than 40% at the start of the infusion it is advisable to discard the battery and install a new one.

Fine-bore lines with a small priming volume (less than 1ml and preferably less than 0.3ml) are recommended. When a new infusion line is used it should be primed with contents from the syringe until the fluid just shows at the needle tip. If a new line is required part way through an infusion, for example due to due to site irritation, it will require priming, which means that the syringe pump will not run for the full 24 hours. When an infusion line is already in situ and resiting is not required, the line can be disconnected from the previous syringe.

• The used syringe should be removed from the pump with the line attached;
• The new syringe is then loaded into the pump;
• The line can then be disconnected from the old syringe and attached to the number pump;
• The infusion programme should then be set according to manufacturers’ instructions.

To avoid an inadvertent bolus dose, the syringe must be attached to the pump before connecting to the line.

The pump should be started according to the prescription and manufacturers’ instructions, and the infusion monitored regularly to ensure it is running and to detect complications.

Choosing a site

A 23g butterfly needle or Sof-Set needle is normally used for subcutaneous infusions. The insertion site depends on the patient’s needs (Fig 1, attached). For ambulatory patients the chest and abdomen are usually the preferred injection sites; movement of the arm may cause problems such as bruising if it is used as the injection site. For agitated and distressed patients, placement around the scapula reduces the likelihood of accidental removal of the cannula. The thigh may also be used. Sites to be avoided include:

• Oedematous areas
• Bony prominences;
• Irradiated sites;
• Areas where there is tissue damage such as broken skin or cutaneous tumour sites (Twycross and Wilcock, 2007).

It has been suggested that the site should be rotated every three days to minimise the risk of site reactions (Dickman et al, 2005). However, Twycross and Wilcock (2007) suggest that, with non-irritant medicines, the site may remain satisfactory for seven days or more, so local policies should be followed. The infusion needle should be secured with a transparent dressing so that it can be observed for signs of inflammation. Patients should be encouraged to report any redness, pain, swelling or irritation at the site.

Documentation and monitoring

Dougherty and Lister (2011) suggest that at a minimum the patient’s condition should be checked 15 minutes and one hour after the infusion is started and four-hourly thereafter (although local policy should be followed). However, this is not always possible in primary care or community settings, and it may then be beneficial to involve the patient and/or relatives in the monitoring process.

Subcutaneous infusions should be monitored regularly for precipitation and discolouration, and to ensure the infusion is running at the correct rate. Pump functioning is assessed by regular monitoring of the volume to be infused over the time remaining and the battery life; any deviations need to be investigated immediately. Patient monitoring is crucial if symptom control is to be maintained. Regular observation and questioning, such as “do you have any pain?”, ensures any necessary breakthrough doses of medicines can be given and patient comfort maintained. Symptom charts should be completed according to the patient’s condition and local policy.

Any changes that may need to be made to the medication in the syringe pump should be anticipated; for example, if a patient has required regular breakthrough doses of diamorphine to control pain, the quantity of the drug in the syringe pump may need to be increased (Barnes et al, 2009). When the 24-hour dose is changed, the breakthrough dose should also be adjusted accordingly.

Discontinuing a pump

To terminate the pump, press the STOP button and remove the needle/cannula as soon as possible. Although the syringe pump keeps a record of how much it has delivered, the amount of drugs delivered and wasted should be documented on the controlled stock sheet that is part of the nursing documentation. Waste should be disposed of in the sharps bin by a qualified nurse.

Conclusion

Syringe pumps have an important role in symptom management. They are often viewed by patients and families as signalling the end of life, but they offer patients the opportunity to receive effective symptom control. It is vital that nurses using pumps have appropriate training and supervision to avoid errors. Box 3 offers advice on using the pumps.