Summary

A Syringe Driver, clinically known as a Continuous Subcutaneous Infusion (CSCI), is a portable battery-operated pump that delivers medication slowly under the skin over 24 hours. The standard device in the UK is the McKinley T34. It is the mainstay of symptom control in the terminal phase when the oral route is no longer viable. It provides constant plasma levels of drugs, avoiding peaks and troughs. Common drugs administered include analgesics (Morphine/Diamorphine), antiemetics (Levomepromazine/Haloperidol), sedatives (Midazolam), and antisecretory agents (Hyoscine). [1,2]

Key Indicators for Use

• Dysphagia: Unable to swallow oral meds.
• Nausea/Vomiting: Persistent vomiting or bowel obstruction.
• Malabsorption.
• Weakness/Coma: Patient in last days of life.

Clinical Pearls

The "Just in Case" (Anticipatory) Meds: A syringe driver takes ~4 hours to reach steady state. It is for maintenance. Always prescribe "PRN" (as required) SC bolus doses for breakthrough symptoms (usually 1/6th of the 24h dose).

Water vs Saline: Water for Injection is the standard diluent for most drugs (Morphine, Diamorphine, Midazolam). Saline (0.9% NaCl) is preferred for some irritating drugs like Cyclizine or Levomepromazine, or Octreotide. Check the Palliative Care Formulary.

Diamorphine vs Morphine: Diamorphine is highly soluble. You can fit 1000mg in 1ml of water. Morphine is less soluble, requiring larger volumes. This is why Diamorphine is preferred in drivers (smaller volume = less site irritation).

Indications

• Terminal agitation.
• Pain control in dying patient.
• Intractable vomiting.

Contraindications / Cautions

• Severe thrombocytopenia (bleeding at site).
• Generalised oedema (anasarca) - poor absorption.

Site Checks (Every 4 Hours)

• Redness/Pain: Inflammation?
• Swelling: Drug not absorbing?
• Leakage: Line disconnected?
• Pump: Is the battery light flashing? Is the rate correct?

Management Algorithm

           DECISION TO START CSCI
           (Oral route lost)
                    ↓
          CALCULATE DOSES (24h)
          (Sum of regular + PRNs used)
                    ↓
          CONVERT TO SC ROUTE
                    ↓
          CHECK COMPATIBILITY
          (Are drugs safe to mix?)
                    ↓
          SET UP DRIVER
          (Site: Chest/Arm/Thigh)
          (Rate: Over 24 hours)
                    ↓
          MONITOR (4 hourly)

1. Dose Conversions (Critical Safety)

Always verify with local guidelines/BNF.

• Oral Morphine to SC Morphine: Divide by 2.
  • Example: Patient on Zomorph 30mg BD (Total 60mg). Syringe Driver = 30mg SC Morphine.
• Oral Morphine to SC Diamorphine: Divide by 3.
  • Example: Total 60mg Oral Morphine. Syringe Driver = 20mg Diamorphine.
• Oral Oxycodone to SC Oxycodone: Divide by 2.

2. Mixing and Compatibility

• Usually max 3 drugs in one syringe.
• Cyclizine: The "Crystal Maker". Incompatible with almost everything (especially Hyoscine and high dose Morphine). If needed, use a separate driver.
• Dexamethasone: High doses can precipitate.

3. Setting Up

• T34 Pump: Auto-calculates rate based on syringe size to deliver over 24 hours.
• Siting: Use a butterfly needle. Secure with transparent dressing (Tegaderm) to inspect site.
• Priming: Prime the line with the drug solution (Volume ~0.5ml).

• Effective symptom control achieved in >90% of cases.
• Does not hasten death; ensures comfort.

Key Guidelines

Landmark Knowledge

1. The "Death Rattle"

• Caused by pooled secretions in the pharynx that the patient is too weak to cough up.
• Hyoscine (Butylbromide/Hydrobromide) dries up secretions. It works best if started early (before secretions build up). It cannot remove secretions that are already there.

What is this machine?

This is a small, quiet battery pump. It trickles the pain medicine constantly under the skin through a tiny plastic tube.

Why do we need it?

Your relative is too weak to swallow pills now, or they might feel sick. If we stop the medicines, the pain might come back. This pump ensures they get the medicine they need without us having to annoy them with injections every few hours.

Will it make them pass away sooner?

No. The dose is exactly the same as (or even slightly less than) what they were taking by mouth. It is purely for comfort.

Common Exam Questions

1. Prescribing: "Convert 60mg BD MST (Oral Morphine) to Syringe Driver Diamorphine."
   • Answer: Total Oral = 120mg. Divide by 3 = 40mg SC Diamorphine.
2. Palliative Care: "Drug for secretions that causes sedation?"
   • Answer: Hyoscine Hydrobromide (Crosses BBB). Butylbromide does not sedate.
3. Pharmacy: "Incompatibility with Cyclizine?"
   • Answer: Precipitates with Hyoscine/Morphine. (Crystallisation).
4. Nursing: "Site is red and hard. Action?"
   • Answer: Stop driver. Re-site in new area. Check solution for precipitation.

Viva Points

• Alfentanil: When to use? In severe Renal Failure. Morphine/Diamorphine metabolites accumulate in renal failure (causing twitching/seizures). Alfentanil is liver metabolised.
• Levomepromazine: Broad spectrum antiemetic acting on D2, 5HT2, H1, Ach receptors. Good for unknown cause of nausea.

Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.