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What are syringe drivers?

Subcutaneous (SC) drug infusion by syringe driver is most frequently used in palliative care, particularly in cancer care. It allows the continuous delivery of a range of drugs over 24 hours to aid comfort in those people who are unable to take medication orally due to:

• Persistent nausea and/or vomiting.

• Disfagia.

• Bowel obstruction or malabsorption.

• Significant tablet burden.

• Reduced level of consciousness.¹

Most syringe drivers are portable but some may be non-ambulatory.

Pain is experienced by most patients with advanced cancer and its prevalence in this group is estimated at over 70%.²

Other common indications for using a syringe driver in palliative care include excessive respiratory secretions, and agitation or restlessness.

• Sublingual administration is not always easy if the mouth is dry, co-ordination is poor or cognitive function is impaired.

• Rectal administration can be a challenge for carers, both physically and emotionally.

• A syringe driver is only an alternative method of administering medication. It does not produce more effective analgesia than the oral route unless the patient cannot use oral medication, or has serious compliance problems. It should not be routinely used as a 'medical last rite' if there is no specific indication for medication. Instead, a holistic assessment should be done, taking into account the range and severity of symptoms, any underlying treatable causes, non-pharmacological options, and the patient's preferences.³

A range of professionals are involved in the delivery of syringe driver therapy in the UK, including GPs, out of hours services, community nurses, pharmacists, and specialist palliative care teams. It is important to ensure good anticipatory care, including appropriate prescribing and communication between providers, patients and their carers or families. See the separate Cuidados Paliativos, Looking after People with Cancer e Cuidados de Fim de Vida artigos.

• A syringe driver takes 3-4 hours to establish a steady state drug level in plasma. If the patient is in pain, vomiting or very agitated, give a stat SC injection of appropriate medication while setting up the syringe driver.

• Only use drugs that are known to be effective via the SC route. Diazepam, chlorpromazine and prochlorperazine are too irritant to be given SC.

• Check drug compatibility before mixing. If you are unable to obtain advice about drug combinations from either the palliative care team or the hospital drug information service, you can find information on the palliative drugs or Medicines Complete websites.^{4 5}

• Prescribe the medication(s) for subcutaneous infusion and prescribe the diluent, calculating the appropriate dose when converting from oral to subcutaneous route.

• Water for injection is most commonly used to dilute the drugs. However, saline is recommended for some drugs and may be used if there are problems with site irritation. Saline should not be used with cyclizine, as it can cause precipitation.

• Calculate the total dose of drug required in 24 hours and then divide volume of solution by 24, to give a rate per hour.

• A new syringe should be prepared every 24 hours.

• Prescribe the correct breakthrough dose, as required, for each medication in the infusion.

• Never use solutions that have precipitated or become discoloured.

• Always consider alternative routes, such as buccal, rectal, sublingual or transdermal. The patient may not want a syringe driver.

Always check drugs and their doses with local palliative care prescribing guidelines. The table below lists some commonly used medications.

Generally there are few compatibility problems with common two and three drug combinations containing:

• Diamorphine.

• Cyclizine.

• Haloperidol.

• Metoclopramide.

• Levomepromazine.

• Hyoscine hydrobromide.

• Midazolam.

Signs that drugs in a syringe driver are incompatible include:

• The solution appears cloudy or there are visible crystals.

• There is a site reaction.

• There is an unexpected worsening of symptoms.

Compatibility issues can occur with drugs that include (but are not limited to) the following:

• Cyclizine with diamorphine, which may precipitate once the relative concentration of diamorphine increases.⁷ It causes precipitation with saline. At higher diamorphine doses, either put cyclizine in a second syringe driver or use levomepromazine as a single daily SC injection instead.

• Hyoscine butylbromide (Buscopan®) can be incompatible with cyclizine and should be used with caution. Levomepromazine could be given as a single daily injection in place of cyclizine.⁸

• Diclofenac is incompatible with most drugs and should be administered in a separate syringe driver.¹

• Dexametasona is not usually added to syringe drivers and can precipitate. It also inactivates glycopyrronium bromide. This problem may be solved by using hyoscine hydrobromide instead of glycopyrronium bromide. Alternatively, dexamethasone could be given as a separate once-daily injection.

• Mechanical problems.

• Human errors.⁹

• Reactions at the infusion site can be controlled by considering:
  

  • Site:
    

    • If there is pain or obvious inflammation, change the site.

  • Needle:
    

    • Needle should be bevel down.

    • A small Teflon® cannula may be less irritating than a butterfly needle.

  • Contents of infusion:
    

    • Irritant drugs concentration may be too strong.

    • Consider whether irritant drugs can be substituted for non-irritant (eg, cyclizine to haloperidol).

    • Irritant drugs could be given by an alternative route - eg, PR or IM or as single SC injections.

    • Saline can be used for dilution instead of water (except for cyclizine).

    • Hyaluronidase can be added to the infusion.¹⁰

    • Dexamethasone can be added to the infusion, in a dose appropriate to the patient's clinical condition.

  • Difficulties with mixing drugs within the syringe.

  • Errors in over-infusion:
    

    • Fatalities have occurred.

    • If the infusion is running too quickly, check the rate calculation and setting; if the infusion is running too slowly, check the start button, battery, that the syringe driver is in good working order, the cannula for blockages and injection site for inflammation.⁷