
Question: From Orlando, Florida, USA:
Please answer these questions about children on insulin pumps:
 How you explain to a child with insulin pump how to calculate a bolus?
 How are the ratios are calculated for the child?
 How does the child calculate the bolus?
Answer:
 This depends on the age of the child. For very young children, the parent needs to calculate and deliver/supervise the bolus. As children get older, set "rules" for boluses can be given (a written out sliding scale for corrective doses, fixed carb snacks with instructions on how much insulin to give for each snack eaten) with the parent/teacher troubleshooting as necessary. Eventually, the child can learn the math necessary to do their own "carbinsulin" ratios and "corrective doses." The exact age of the child capable of learning each of these stages varies from individual to individual. Even teenagers may need help.
 Carbohydrateinsulin ratios are calculated by looking at the amount of insulin necessary to cover a certain amount of grams of carbohydrate. Generally, an estimation can be done when one starts on ratios by the "450 or 500" rule. This involves taking the number 500 (or 450) and dividing it by the total number of units of insulin given throughout a day. This will give a ballpark amount of how much insulin is needed to cover a fixed number of grams of carbohydrate. Diet records are also essential in evaluating how much insulin is needed per gram of carbohydrate. The ratios often vary by time of day (e.g., young children need more insulin per gram of carbohydrate in the morning than in the evening, on average).
Once an insulin/carbohydrate ratio is developed, the dose of insulin per gram of carbohydrate is calculated like this: If the ratio is 1 unit/15 grams carbohydrate and the child eats 38 grams of carbohydrate  the dose of insulin to cover that food is 38/15 or 2.5 units.
Corrective doses are based upon insulin sensitivity. Generally, an estimation can be done when one starts on ratios by the "1500" rule. This involves taking the number 1500 and dividing it by the total number of units of insulin given throughout a day. This will give an approximate amount of how much insulin is needed to bring the blood sugar down a certain number of mg/dl. Insulin sensitivity, like carbinsulin ratios, may also vary by time of day. A target blood sugar for the child is also necessary (generally around 120 mg/dl [6.7 mmol/L] for a schoolaged child).
Once a corrective dose is developed, the dose of insulin needed to lower the blood sugar is calculated like this: If the corrective dose is 1 unit / 100 mg/dl glucose with a target blood sugar of 120 mg/dl [6.7 mmol/L], then if the child's blood sugar is 383 mg/dl [21.3 mmol/L], the dose of insulin needed to bring the blood sugar to target is (383120)/ 100 or 2.6 units.
 The bolus is calculated by adding the carbohydrateinsulin ratio amount to the amount of insulin needed to bring the blood sugar down into range. See comments above about how/when children can calculate their own doses.
DTQONCEMMS20011106
Original posting 25 Nov 2001
Posted to Insulin Pumps
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Last Updated: Tuesday April 06, 2010 15:09:28
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