Key Facts

Syringe drivers are an essential tool in palliative care, enabling symptom management when the oral route is unavailable. Safe prescribing requires knowledge of drug conversions, compatibility, and local protocols.

Epidemiology

• Used in approximately 30-50% of dying patients in the UK
• Most commonly used in the last days of life
• Also used earlier for bowel obstruction, persistent vomiting, or severe dysphagia

Aetiology

Indications for CSCI:

• Patient unable to swallow (dying, dysphagia, drowsy)
• Persistent nausea/vomiting (oral route unreliable)
• Bowel obstruction (oral absorption impaired)
• Need for multiple parenteral medications
• Patient preference (avoids repeated SC injections)

Pathophysiology

• Subcutaneous absorption: continuous, steady-state delivery → avoids peaks and troughs of intermittent injections
• SC bioavailability approaches IV for most palliative drugs
• Insertion sites: upper arm (deltoid area), anterior chest wall, thigh, abdomen
• Change site every 48-72 hours (or sooner if inflammation/hardening)

When to Start a Syringe Driver

• Patient recognised as dying and unable to take oral medications
• Persistent vomiting despite antiemetics
• Bowel obstruction preventing oral absorption
• Dysphagia (progressive neurological disease, head and neck cancer)
• Two or more symptoms requiring regular SC medication

Assessment Before Starting

• Current symptoms and medications
• Total 24-hour opioid requirement (including breakthrough doses used)
• Other medications needed (antiemetic, anxiolytic, antisecretory)
• Renal function (affects opioid choice)
• Allergy status

Red Flags

• Syringe driver NOT started as a "comfort measure" in isolation — must be accompanied by clinical assessment and communication
• Starting a syringe driver should NOT be seen as "giving up" — it is a route change, not a treatment change
• Drug incompatibility causing crystallisation or precipitation (check charts)
• Site reactions (inflammation, erythema — change site)

Bedside

• Review all current medications
• Calculate 24-hour opioid requirement
• Check drug compatibility (local chart)
• Identify insertion site
• Check renal function (from recent bloods)

Bloods

• U&Es (renal function — guides opioid choice)
• Generally not needed to initiate CSCI in dying patient

Imaging

• Not applicable

Special Tests

• Drug compatibility check (essential)
• Calculation check (second clinician verification recommended)

Prescribing a Syringe Driver

1. Calculate 24-hour opioid requirement:
   • Total oral morphine in 24h (MR + IR doses used) → convert to SC
   • Oral morphine ÷ 2 = SC morphine; oral morphine ÷ 3 = SC diamorphine
2. Add other medications as needed:
   • Pain: diamorphine, morphine, or oxycodone (or alfentanil if renal failure)
   • Nausea: haloperidol 1.5-5mg/24h or levomepromazine 6.25-25mg/24h
   • Agitation: midazolam 10-30mg/24h
   • Secretions: hyoscine butylbromide 60-120mg/24h or glycopyrronium 0.6-1.2mg/24h
3. Check compatibility: use local chart; Water for Injection as diluent
4. Prescribe PRN SC breakthrough doses (1/6th of 24h opioid dose)
5. Review daily: adjust doses based on symptom control and PRN use

Common CSCI Combinations

• Pain + nausea: diamorphine + haloperidol (compatible)
• Pain + agitation: diamorphine + midazolam (compatible)
• Pain + agitation + secretions: diamorphine + midazolam + hyoscine butylbromide (compatible)
• Pain + nausea + agitation: diamorphine + haloperidol + midazolam (check concentration)

Practical Points

• Use McKinley T34 syringe driver (rate in mm/hour; 24-hour infusion)
• Site: anterior chest wall, upper arm, abdomen, thigh
• Change site: every 48-72 hours or if inflammation
• Protect from light: if light-sensitive drugs used
• When starting: continue oral medications until CSCI has had 30-60 minutes to reach steady state

Referral Criteria

• Uncertain about drug compatibility or conversion: specialist palliative care pharmacist
• High-dose opioid conversions: specialist input
• Refractory symptoms despite CSCI: specialist palliative care review

• CSCI effectively manages symptoms in the majority of dying patients
• Starting a syringe driver does not hasten death — it changes the route of medication delivery
• Clear communication with families about the purpose of CSCI is essential
• Breakthrough doses should always be available alongside CSCI

Common CSCI Drug Doses

Opioid Conversion for CSCI