I had often been puzzled by statements, made by some of my patients who use insulin infusion pumps, such as, “I notice elevated blood glucose levels after I insert a new infusion set.” This never made sense to me as a source for hyperglycemia unless of course the set was inserted improperly….
It was especially puzzling that this should occur after every change. I began to do a careful review of their insulin infusion pump databases and noticed that many of these patients were waiting until they got a “NO Delivery” alarm to refill their pump, indicating that their reservoir was in fact empty. Since noticing this phenomenon I have paid particular attention to the alarm history and glucose reports when downloading insulin pump data for review.
The NO Delivery alarm may show up some time after the reservoir has become empty since sufficient pressure must build up in the system to indicate that the push rod has met resistance. On the Medtronic 5xx series Paradigm pumps the status screen will indicate “–.–” units left sometimes hours before the NO Delivery alarm comes on (depending on the rate of basal delivery). Due to the pharmacologic action of rapid analog insulin, the hyperglycemic effect of this non-delivery of basal is often most pronounced 2-3 hours later.
I have addressed this in several ways in my practice:
1) When providing insulin pump training I help the individual to determine how much insulin to put in the reservoir for a 2-3 day supply based on average daily usage plus 10-20 units for priming. Many patients are averse to “wasting” insulin and will leave the site and reservoir in beyond the recommended 48-72 hours to avoid throwing insulin away.
2) I look at the pump alarm history for NO Delivery alarms as well as looking at the prime history. Patients have been receptive to this information when I demonstrate the pattern of hyperglycemia in the hours following an empty reservoir alarm.
3) I remind my patients using insulin infusion pumps that it is best to review the units left in the reservoir at the beginning of the day so the “empty reservoir” alarm does not become a “Diabetes Emergency” at an inopportune moment. Thus they can plan for their site change time and avoid delay when the reservoir is empty. I recommend setting the Low Reservoir warning on the Medtronic pumps for an amount that will allow them time to plan for the reservoir/site change.
Kathleen C Jones RN MSN CDE
Diabetes Clinical Educator
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