A quick overview
An insulin pump is a device that delivers a subcutaneous infusion of insulin that imitates the physiological insulin profile. The pump itself is the size of a pager, and contains:
- An insulin cartridge – it contains the insulin, Humalog or Novorapid
- Motor to drive the infusion
- Software to program the pump settings
- Tubing that infuses insulin from the cartridge to the subcutaneous infusion site
- Connectivity to a continuous glucose monitor, if this is used by the patient.
- A cannula that is inserted by the patient subcutaneously for the insulin to be delivered as an infusion
The patient wears the pump 24 hours a day and changes the cannula every 3 – 5 days. To use a pump, your patient has undertaken extensive education in carbohydrate counting, interpreting their glucose levels and pump use. He/she will be an expert on their pump and can be trusted to manage it in hospital if they are well enough.
The insulin in a pump is delivered in two forms:
- A continuous basal insulin,
- This is infused at variable rates programmed into the pump at different times of the day and night.
- Typically, lower rates are programmed overnight
- Rates can be increased or decreased temporarily, depending on the patient’s glucose levels at that time. This flexibility is not available with insulin injections.
- A bolus dose of insulin
- This setting allows the insulin to be infused through the pump at a higher rate when activated by the patient.
- The period of the bolus is set to last 2 – 4 hours, and imitates the dose of rapid-acting insulin
- The patient sets the pump to deliver this dose to match the dietary carbohydrate and to correct higher glucose levels.
When to remove it in hospital
An insulin pump should only be removed in circumstances when the pump has failed or if the patient is unable to use it. These situations include:
- Unconsciousness or delirium
- Diabetic ketoacidosis
- Severe hypoglycaemia
- Major surgery
- Multiorgan failure
- Erratic glucose levels and medical comorbidity eg. acute myocardial infarction, pancreatitis
- Patient preference
How to check the pump
If you suspect the pump has malfunctioned, check it at the points of failure:
- Cannula insertion site
- Cellulitis or collection
- Skin irritation – usually relates to adhesive, not the tape
- Kinks or disconnection from the cannula or pump itself
- Bubbles or residue in the tubing
- Pump itself
- Error in the software
- Battery failure
- Air in the cartridge