SUBCUTANEOUS INFUSIONS

The portable syringe pump was invented by Wright in 1979 to deliver desferrioxamine to patients with thalassemia. In the same year Russell suggested its use for infusions in terminal malignant disease.

The continuous subcutaneous infusion of drugs by a small portable pump (sometimes called a “syringe driver”) is a major advance in terminal care, particularly for symptom control in the home. It has a number of advantages over intravenous therapy. It is safer (much less risk of infection and no risk of air embolus). The patient can remain fully ambulant. Tolerance does not develop to subcutaneous morphine as it does occasionally to IV morphine. (see Morphine)

The main indications for continuous subcutaneous infusions are vomiting, dysphagia, severe weakness or unconsciousness. They can be particularly useful for patients at home, either to control nausea and vomiting, or during the last days of life if the patient is no longer managing oral medication.

A continuous subcutaneous infusion of drugs is particularly useful in the management of malignant intestinal obstruction. (see Intestinal Obstruction)

«  Continuous subcutaneous infusions are rarely needed for pain control alone.

«  Each drug in an infusion must be individually titrated to the patient’s needs. Do not use “fixed cocktails” of drugs.

The following drugs can be used in continuous subcutaneous infusions and mixed together in any combination:

Drug 

Usual Starting Dose per 24 hours

Morphine 1/2 the 24 hour oral dose
Cyclizine 100mg to 150mg
Haloperidol  5mg to 10mg
Methotrimeprazine 50mg to 100mg
Scopolamine 0.8mg

Do not use chlorpromazine, prochlorperazine or thiethylperazine in continuous subcutaneous infusions, because these cause skin irritation. Cyclizine above a concentration of 10mg/ml may precipitate with morphine or hydromorphone.

When a patient needs regular injections of anti-emetics, it is usual to start a continuous subcutaneous infusion with cyclizine 100mg to 150mg per day. Haloperidol 5mg to 10mg per day can be added if necessary. In nausea resistant to these drugs, methotrimeprazine 50mg to 100mg per day is usually adequate, although very sedating. (If the patient is warned of this, he or she will usually prefer sedation to nausea.) Very often, once nausea is controlled, the dose can gradually be reduced over a period of days without the nausea returning.

The following drugs can also be used in continuous subcutaneous infusions, but experience with them is more limited: 

Drug 

Usual Starting Dose per 24 hours

Hydromorphone 1/2 the 24 hour oral dose
Metoclopramide 30mg to 60mg
Dexamethasone 2mg to 12mg
Atropine  1.2mg
Midazolam 10mg to 30mg
Phenobarbital
(water-soluble)
200mg
Hyaluronidase 1ml

Midazolam, a short-acting water soluble benzodiazepine, can be useful for terminal agitation.

Phenobarbital must be in water-soluble form, and cannot be mixed with other drugs. A second (separate) continuous subcutaneous infusion can be started when phenobarbital is used to control seizures.

Hyaluronidase can reduce any swelling at the infusion site, but is contraindicated if there is a history of asthma or allergy.

«  The only contraindication to continuous subcutaneous infusions is severe thrombocytopenia.

When the subcutaneous route is chosen, the pump must be small, portable and battery-operated. The use of larger and more complicated pumps merely adds to expense, and reduces mobility in the conscious patient. 

Obsolete information removed

Explanation – The patient and family must be prepared before a continuous subcutaneous infusion is set up. Most patients willingly accept it, and quickly adapt to it, provided the pump is small, easy to use, and unobtrusive. (One patient attended a very elegant formal reception with the pump hidden in her evening bag.) Some people dislike the thought of being “hooked to a machine”, and explanation about the size and portability of the pump is important. Most patients soon forget it is there. Patients can still take showers and baths, but should avoid dropping the pump in the bathwater.

Technique – A small (25g) butterfly with a long (100cm) cannula attached is inserted subcutaneously in the abdomen, chest, thigh or upper arm, and is covered with a small piece of transparent membrane (Opsite) which holds it firmly and allows the site to be inspected for swelling or redness. This site normally has to be changed every 2 or 3 days.


The author and publisher have taken precautions to ensure that the information in this book is error-free. However, readers must be guided by their own personal and professional standards of good practice in evaluating and applying recommendations made herein. The contents of this book represent the views and experience of the author, and not necessarily those of the publisher.


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