Syringe Drivers

Subcutaneous (s/c) drug infusion by portable syringe driver has had a significant impact on palliative care. It allows the continuous delivery of a range of therapies to aid patient comfort, whilst bypassing problems found in terminal illness such as:

• Dysphagia
• Inability to take medication orally
• Weakness

Pain is experienced by 70-90% of patients with advanced cancer.¹ Severe pain is experienced by 66% of people with cancer at some point in their illness.²

• 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.

Drugs are commonly required in palliative care to control:

• Analgesia - diamorphine injection: dose 5-10 mg or one sixth of current 24 hour diamorphine requirement.
  An alternative is sublingual diamorphine 10 mg or morphine concentrated liquid 20 mg/5 ml sublingual).
• Nausea and vomiting - give cyclizine injection 50 mg.
  Alternative is buccal prochlorperazine 3 mg / rectal prochlorperazine 5 mg.
• Excess secretions - give hyoscine hydrobromide injection 0.4 mg or hyoscine transdermal patch 1 mg/72 hrs (may need 2-3).
• Agitation/restlessness - midazolam injection 10 mg or sublingual lorazepam 1 mg/rectal diazepam 10 mg.

Although GPs provide the majority of palliative care services in the UK, there are often problems with symptom control and communication. Many feel clinical training is inadequate. The Liverpool Care Pathway for the Dying Patient provides a national framework for caring for patients in the terminal phase of their illness.³

Health care professionals may have difficulty in diagnosing dying, but it is prerequisite for providing good care.⁴ It can be recognised by the following common features:

• Day by day deterioration, at a faster rate than previously
• Patient is drowsy or comatose
• Bed bound
• Taking little by mouth
• Altered breathing pattern
• Peripherally shut down
• Patient may declare they are dying

The terminal phase starts approximately 24 hours before death (median value), but may vary from hours to several days.

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

• Diamorphine
• Cyclizine
• Haloperidol
• Metoclopramide
• Levomepromazine
• Hyoscine hydrobromide
• Midazolam

However there can be problems with:

• Cyclizine with diamorphine, once diamorphine dose exceeds 200 mg/24 hours. It causes precipitation with saline and with diamorphine doses exceeding 200 mg/24 hours. This can be solved by using water as diluent. At higher diamorphine doses, either put cyclizine in a second syringe driver or use levomepromazine as a single daily s/c injection instead.
• Hyoscine butyl bromide (Buscopan®) is occasionally incompatible with cyclizine. Levomepromazine could be given as a single daily injection in place of cyclizine.
• Ketorolac has many incompatibilities. The main ones are with haloperidol, midazolam and cyclizine. Using a separate syringe driver is recommended.
• Dexamethasone has common/unpredictable precipitation. It also inactivates glycopyrrolate. This problem may be solved by using hyoscine hydrobromide instead of glycopyrrolate. Alternatively, dexamethasone could be given as a separate once daily injection.

• Mechanical problems
• Reactions at the infusion site can be controlled by considering:⁸
  • Site
    • Daily change of site daily
    • Placing a GTN patch over the site of the infusion
  • Needle
    • Needle should be bevel down
    • Placing the needle I/M, rather than s/c
    • A small teflon cannula may be less irritating than a butterfly needle
  • Contents of infusion
    • Irritant drugs concentration may be too strong.
    • Can irritant drugs be substituted for non-irritant e.g. cyclizine to haloperidol.
    • Irritant drugs could be given by an alternative route e.g. PR or IM (levomepromazine can be given as a single daily injection).
    • Saline can be used for dilution instead of water (except for cyclizine).
    • Hyaluronidase (1500 units) can be added to the infusion.
    • Dexamethasone can be added to the infusion, in a dose appropriate to the patients clinical condition. (To add dexamethasone the diamorphine should be made up with as much water as volume calculation allows. Other additions are then made. Dexamethasone is then drawn slowly into the syringe which is inverted a few times to mix).
  • Difficulties with mixing drugs within the syringe
  • Errors in over infusion
    • Fatalities have occurred.⁹
    • If infusion running too quickly or slowly check rate calculation; if infusion running too slowly check start button, battery, syringe driver is in good working order, cannula for blockages and injection site for inflammation.