How do insulin pumps work?

Insulin pump: a game-changer in the management of type I diabetes, allowing for more natural insulin administration, tighter control and patient empowerment; a cause of dread for residents who have never had to manage one before.

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Parts of a pump: the pump itself, the infusion set (the tubing), the cannula (the needle that goes into the skin). While many people do the traditional “check your fingerstick four times a day” thing, some also use continuous glucose monitoring (CGM) with their pumps. 


It’s worth noting that hospital policy (at the hospital I work at, at least) is that patients should be allowed to manage their own insulin pump as long as they have capacity. There are tales passed down about patients who refuse to give up their insulin pump and send themselves into repeated episodes of hypoglycemia…but there is more going on there than just diabetes.

The pump requires a lot of education, and are costly. But they are also pretty cool. Every patient has basal infusions of insulin pre-programmed into their pump.ONLY rapid-acting insulin is used (U100) but it is infusing 24 hours a day.The program is usually reviewed every few months with their endocrinologist based on their sugar logs and adjusted if the blood glucoses are too high or low.

Patients still have to count their carbs, do four times a day fingersticks, and use a correction factor, but they can calculate their own mealtime bolus and adjust accordingly. Here is a general page about diabetes management for patients on the Joslin Center website that includes information about insulin pumps.

Calculating a bolus: 

There’s a patient-version handy guide from Medtronic, which has this example:

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  • hypoglycemia: has the patient been exercising more than usual? Are they drinking alcohol and not eating as much as they should? Is their correction factor too aggressive?
  • hyperglycemia: is the infusion site properly connected? Is the pump itself malfunctioning, and do they need new supplies? Is the infusion site scarred over and not absorbing insulin as well? Is it not calculating the right amount of correction insulin?




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