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Insulin Adjustment: an Overview
for Insulin Pump Programs
Background Reading for this Article...If you have not done so already, we recommend that you read the following WaltzingTheDragon.ca pages on insulin adjustment for pumps as background for the information that follows:
Insulin pump programs [or Continuous Subcutaneous Insulin Infusion (CSII)] use a basal-bolus approach for blood glucose management. Further, a pump provides both basal and bolus factors via the same (rapid-acting) insulin: the basal insulin is provided automatically throughout the day, based on rates you have programmed into the pump; bolus insulin is provided when needed, by entering the relevant information at meals/snacks and when blood glucose is above range.
The key differences in insulin adjustment between pump therapy and injected-insulin programs are:
- Pumps allow different amounts of insulin to be delivered at different times of the day, according to individual need. This increased flexibility means that you can look beyond a “best fit” basal rate for the day as a whole; instead you can test your child’s basal rates in the morning separately from testing the afternoon, evening, or overnight basal rates, for example.
- Compared to injections, pumps allow much smaller amounts of insulin to be delivered: the smallest dose of insulin that can be delivered via a syringe is .5U, while the smallest bolus of insulin delivered via an insulin pump is .05U. Therefore, what was “close enough” for injections may not be as close as you can get with a pump; greater fine-tuning of insulin doses is possible.
- An insulin pump uses only rapid-acting insulin (here in Canada: Humalog®, NovoRapid® or Apidra®). Therefore, the only relevant insulin action is that of rapid-acting insulin, which has an onset of about 15 minutes, peaks at about 1 hour, and lasts 3-5 hours.
More about the differences between injected insulin programs and pump programs:Insulin Programs
How to Assess Current Pump Settings
In order to see if the current pump settings are most appropriate for your individual child at this time, you can take one of a few different approaches, which differ in terms of intensity of effort.
If your child is having few problems with blood glucose control and/or it is a particularly difficult time* to take on an intensive investigation, a Semi-Structured Record Reviewmay yield all the information you need to make the appropriate insulin adjustments at this time.
On the other hand, if there are significant issues in terms of your child’s blood glucose control, or if a Record Review approach hasn’t revealed clear patterns to adjust, or you just haven’t got the results you would like with less formal methods, you may find it helpful to take a more systematic approach to insulin adjustment. To do so, you could investigate any or all of the following pump settings (in order):
- Basal rates (For information on Testing and Adjusting Pump Basal Rates)
- Insulin:Carb (I:C) ratios (For information on Testing and Adjusting Pump I:C Ratios)
- Insulin Sensitivity Factor (ISF) (For information on Testing and Adjusting Pump ISF Settings)
- Duration of Insulin Action (DIA) (For information on Testing and Adjusting Pump DIA Settings)
Points to Note:
- It is important to start assessment and fine-tuning of the insulin doses programmed into your child’s pump by assessing the basal rates. Basal doses of insulin are the foundation for any basal-bolus program; if your child’s basal rates are too high or too low, then it may be impossible to determine the real cause of a pattern of high or low blood glucose. For example, if your child’s blood glucose is often high after supper, it’s logical to conclude that they are not getting enough insulin for the carbs they eat at supper (I:C ratio is too weak). But what if the basal dose during that time period has not been assessed? Perhaps the I:C ratio is correct, but the basal insulin dose is too low, making it appear that the resulting highs are due to under-dosing for the food eaten at supper. To avoid getting more and more muddled as adjustments bring you farther and farther away from ideal dosing, we recommend assessing and fine-tuning basal rates first before making significant adjustments to I:C ratios or ISF.
- Although we will present these 4 factors of insulin adjustment (basal, I:C, ISF and DIA) in what is theoretically a systematic and linear format, the reality is that once you’ve made adjustments in a few areas, you may need to go back and tweak other factors. For example, once you’ve tested and adjusted basal rates and I:C ratios, you might test and find that the most appropriate Duration of Insulin Action setting is 3.5 hours, not 3 hours as you previously had it set. This will then affect the active insulin calculated by the pump, which, in turn, may affect how well the programmed Insulin:Carb ratios work. Then you may need to go back and re-adjust those Insulin:Carb ratios. Throw in your child’s constant growth, as well as changes in hormones, activity, seasons, etc , and you have a recipe for what seems like a never-ending process! Don’t despair: it doesn’t have to be (and, in fact, won’t ever be) perfect – strive instead for an acceptable balance between the four factors of insulin adjustment which minimizes (not “eliminates” – that would be an unreasonable expectation) blood glucose excursions and unpredictability.
The above information was reviewed for content accuracy by clinical staff of the Alberta Children’s Hospital Diabetes Clinic.
This material has been developed from sources that we believe are accurate, however, as the field of medicine (in particular as it applies to diabetes) is rapidly evolving, the information should not be relied upon, as it is designed for informational purposes only. It should not be used in place of medical advice, instruction and/or treatment. If you have specific questions, please consult your doctor or appropriate health care professional.
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