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Personalised doses of insulin

February 05, 2003

Diabetes is a widespread illness affecting 5 per cent of the population. In diabetics the metabolism produces an excess of glucose in the blood and, as a result, a number of sufferers need doses of insulin which allows them to regulate their glucose levels.

Currently, the method of administering insulin to diabetic patients making use of emergency services for insulin dosage depends on the experience of the qualified personnel. That is, the same patient can receive different insulin doses, and in different ways, according to the doctor attending her or him.

In order to improve this system of administration, Doctor Tom'¡s Rubio from the Public University of Navarre proposed in his doctoral thesis the development of a mathematical model which would facilitate predicting the exact amount of insulin needed by a patient at any time. The thesis showed that both the absorption constant (the time taken for the insulin to enter the blood and become effective) as well as the elimination constant (the time taken for the insulin to disappear), is different for each patient. Moreover, for any one patient this absorption constant varies with time.

Given this, Doctor Tom'¡s Rubio proposed using a technique based in blood extractions. He concluded that, by taking samples at two different times, the level of glycemia can be measured and the constants of absorption and elimination can be calculated. Knowing these constants, the exact amount of insulin needed by the patient can be calculated. Nevertheless, if the patient suffers another decompensation crisis, it will be necessary to recalculate these constants.

Apart from its use in emergency services, this model has applications for self-medication by the patient at home. For example, it can be used with the insulin perfusion pumps currently used to apply a quantity of insulin, depending on the glucose level. It can also be used with patients undergoing surgery in order to know how much insulin has to be administered during the operation and to control the amount of glucose administered via serum.

Two types of patients

Two types of patients are distinguished in this study. The first corresponds to insulin-dependant diabetic patients, normally young people, who require insulin for their treatment and whose acute condition is usually diabetic ketoacidosis. The second type corresponds to patients who have very high levels of glycemia, usually older and overweight people, who are normally regulated through orally administered antidiabetic medication, although many of these also end up needing insulin. These patients show acute conditions of hyperosmolar coma and symptomatic hyperglycemia.

The research was carried out on patients with the different acute conditions: diabetic ketoacidosis, hyperosmolar coma and symptomatic hyperglycemia. From the analysis of the results it was concluded that, for the construction of the mathematical model, the measuring of glycemia and insulin were necessary.

Elhuyar Fundazioa