Erkennung einer schnell einsetzenden Insulin-induzierten Hypoglykämie durch kontinuierliches subkutanes Glucosemonitoring : eine prospektive klinische Studie

We recently have seen the development of continuously glucose monitoring systems (CGM-systems). These systems measure the subcutaneous glucose concentration and are after calibrating able to determine the blood glucose concentration. Beside a pure documentation function CGM-systems can be combined with an insulin pump to form a closed-loop system, which can independently manage the glucose concentration of diabetes patients. So these patients can sustain a normoglycemic blood glucose concentration without increasing the risk of hypoglycemic episodes. Due to the subcutaneous measuring site we hypothesized that rapid changes in blood glucose will result in a temporal latency between the blood glucose and the subcutaneous glucose concentration. To date this phenomenon has not been investigated in a systematical and clinical study. Therefore the goal of this dissertation is to analyze CGM-systems in the setting of a rapid on-set insulin-induced hypoglycemia. We designed an experimental, prospective, clinical study which includes patients who are suspected to suffer from hypopituitarism. As a part of the normal diagnostic procedure a hypoglycemia will be induced in these patients (Insulin Tolerance Test). We recorded the hypoglycemia by venous, capillary and CGM measurements of blood glucose concentration. In addition we included endocrine (ACTH, cortisol, GH, epinephrine) and psychometric parameters (“Edinburgh hypoglycaemia Scale”). We analyzed the data of 40 normoglycemic patients. In comparison to the venous approach the CGM-Systems has a lag-time of 19,66 min to detect a blood glucose concentration of 60 mg/dl. The lag-time between venous measurements and capillary point-of-care-testing is 2,85 min respectively. In a multiple regression analysis we could identify age as a predictor of the lag-time (R2=0,22). In summary this study shows that subcutaneous CGM-Systems can detect a rapid on-set hypoglycemia only with a certain delay. The results of this study are relevant for the further development of algorithms for closed-loop systems.