CASE Louis C, an 8-year-old boy diagnosed with type 1 diabetes at age 4, was under the care of a pediatric endocrinologist, who used a �pattern� insulin management system to achieve blood glucose control. Louis was maintained on a 4-dose-per-day schedule: Rapid-acting insulin was administered before each meal (with the dosage adjusted based on the pattern of postprandial glucose values over the last 2 or 3 days and by his expected caloric intake and activity level) and a basal insulin given once a day. His HbA1c was 7.2%. He rarely experienced even mild hypoglycemia.
When his family relocated, Louis was taken to another specialist�a pediatric endocrinologist at a medical school affiliated with a children�s hospital. This physician thought that pattern management was out of date, and insisted that sliding scale was the only acceptable approach.
Thus, Louis was put on a regimen of intermediate-acting insulin before breakfast and at bedtime and rapid-acting insulin, given on a sliding scale, at mealtimes. The rapid-acting insulin was withheld if his blood glucose level was ?100 mg/dL; one unit was administered if his level was 101-150 mg/dL, 2 units for a reading of 151-200 mg/dL, and so on. Within 3 months, Louis� HbA1c had risen to 9.8%, and he developed significant hypoglycemia, especially in the afternoon and during the night. Louis� mother reported that he was tired all the time and wondered if it was because his blood glucose levels were �on a roller coaster.�
Adjust�don�t skip�insulin doses
The best medical care aims to reproduce the physiologic state to the extent possible. For patients with insulin-dependent diabetes, that means receiving 24-hour basal insulin coverage, as well as a bolus of insulin with each meal, to mimic normal insulin secretion.16,17
Pharmacodynamically, short-acting insulin lasts 6 to 8 hours. It should be given every 6 hours, in 4 equal doses, without ever skipping a dose. Rapid-acting insulin, too, should never be skipped. Because food or caloric intake requires insulin at the time of ingestion to facilitate glucose transport across the cell membrane, rapid-acting insulin should be administered before each meal (in 3 daily doses if the patient is also taking a long-acting or intermediate-acting insulin, or 6 times a day if used without basal insulin).
Rapid-acting insulin is essentially out of the system by the time of the next preprandial blood glucose test. Therefore, premeal levels mainly measure the action of the basal (long- or intermediate-acting) insulin. The package inserts for rapid-acting insulin state that a 2-hour postprandial blood glucose level should be used to adjust the next dose of rapid-acting insulin.18,19 (See �5 principles of insulin management�)
5 principles of insulin management
These principles can be used in the hospital for professional education and in the outpatient setting for patient education:
- Advise health care professionals (and patients) not to skip insulin doses. To avoid high blood glucose levels caused by low or missed doses, stress the importance of administering short-acting insulin every 6 hours, in 4 equal doses, or rapid-acting insulin before each meal with a long-acting basal insulin.
- Teach providers and patients that on an outpatient basis, routine daily regimens should reflect the pattern of postprandial blood glucose levels over the previous 2 or 3 days.
- Explain that rapid-acting insulin doses should be based primarily on the amount to be eaten, rather than on premeal glucose levels (although abnormally elevated or depressed levels may require a correction).
- Set parameters for glucose levels and instruct patients to call (or to administer a correction dose) if the value falls above or below a predetermined range.
- Consider providing insulin-dependent patients (or their parents, school nurse, or hospital staff) with an algorithm that uses a basal insulin dose and premeal rapid-acting insulin doses, adjusted for caloric or carbohydrate intake. Examples of insulin algorithms, which can help keep problems and telephone calls to a minimum, are available for both type 1 and type 2 diabetes from the Texas Diabetes Council at http://www.tdctoolkit.org/algorithms_and_guidelines.asp.
A closer look at pattern management
Measuring�and recording�both fasting and 1- or 2-hour postprandial blood glucose levels over a 2- to 3-day period is the first step in pattern management. The patient�s insulin intake is determined by the pattern of these values, with adjustments made for anticipated need. Here�s how it works in an outpatient setting:
- In the morning, the patient receives short- or rapid-acting insulin; the number of units is determined by his or her previous after-breakfast blood glucose levels, with adjustments depending on the caloric intake expected at breakfast and any deviation in the patient�s normal activity level to follow.
- At noon, the short- or rapid-acting insulin is adjusted for the size of the lunch and the patient�s recorded blood glucose levels 1 to 2 hours after lunch.
- At suppertime, the amount of insulin depends on the meal and the patient�s previous after-supper blood glucose levels.
- At bedtime, intermediate- or long-acting insulin is administered in an amount adjusted according to the patient�s fasting and/or premeal blood glucose levels. If the values are elevated because of extra eating or decreased activity, a correction dose (See �Calculating a correction dose�) may be needed to restore his or her blood sugar to within an acceptable range.20