Clinical Aspects of Continuous Glucose Monitoring
glucose sensor and would compromise the accuracy of the device in detecting hypoglycaemia.
Currently available CGM systems are approved only as an adjunct to standard SMBG and should not be used to make therapeutic decisions without verification by blood glucose measurement.
Limitations Related to the Patient
In contrast to the motivational benefits, realtime CGM may lead to an increased treatment burden and information overload. Some patients may not be able to deal with the additional data and might overcorrect changes in glycaemia. This should be a major focus of education for the patient using realtime CGM.
This observed age effect may be related to substantially lower use of sensors in the children and adolescent group compared with adults.
Poor patient adherence is an important limitation to the use of realtime CGM. The JDRF showed less benefit of CGM among patients who were eight to 14 years of age and no benefit among those 15–24 years of age.32
Imperfect adherence to many aspects of diabetes management has long been recognised as an obstacle to successful intensive treatment in adolescents and young adults. Greater parental involvement could be the reason why children in the CGM group had greater sensor use than the adolescents. At least six days of sensor use per week was the average for 83% of patients 25 years of age or older, but this percentage dropped in young people to 30% of patients 15–24 years of age and 50% of patients eight to 14 years of age.32
It is important to recognise that the participants in the JDRF trial were highly motivated and capable of using CGM technology and had a better than average metabolic control. The results therefore cannot be extrapolated to a random diabetes population.
Target Population
Patients should be well educated in order to safely use and benefit from CGM. They should be very motivated to participate in the management of their diabetes and be technologically adept. By contrast, patients who have poor metabolic control because of reluctance to perform SMBG will not benefit from the use of CGM. Patients should receive proper instructions about the use of their CGM device, calibration issues and therapeutic decision-making.
Patients who may benefit from the use of CGM include:49 •
impending hypoglycaemic events. This allows the patient to take preventative measures.42
Patients with diabetic gastroparesis may benefit from CGM to optimise the timing of their insulin administration in order to avoid glycaemic excursions.38
For pregnant women with diabetes, strict metabolic control is essential to avoid maternal and foetal complications such as macrosomia, foetal malformations, pre-term delivery and Caesarean section. CGM may therefore help to achieve normoglycaemia, optimise insulin treatment, improve metabolic control and reduce the risk of complications.50 trimester of pregnancy.51,52
This is particularly important during the first
Another important and recently highly controversial issue is glycaemic control in critically ill patients. The strict euglycaemic range of 80–110mg/dl, as proposed by the Leuven trials,53,54
was
criticised by more recent studies. Two multicentre studies (VISEP and GLUCONTROL) were stopped prematurely because of safety reasons (more hypoglycaemia) and lack of benefit.55–57
The NICE-SUGAR study
CGM may be beneficial as it enables intensive care unit staff to evaluate the effect of insulin therapy on the patient’s glycaemia in real time. With CGM, strict glycaemic control can be achieved without the fear of undetected hypoglycaemic events.
Conclusion
In order to achieve tight glycaemic control, the patient with diabetes needs to perform frequent SMBG. Hypo- and hyperglycaemic episodes can be missed between glucose measurements. Furthermore, the fear of hypoglycaemia has an important impact on the patient’s quality of life.
CGM systems provide a complete picture of glucose levels throughout the day and can warn against impending glycaemic excursions. In order to use CGM systems, patients and healthcare providers need to be highly motivated, technologically adept and aware of the limitations. Patients with brittle diabetes, hypoglycaemia unawareness or gastroparesis, those who are pregnant and those who are critically ill may particularly benefit from CGM.
patients with brittle diabetes with poor metabolic control and/or high glucose variability;
• patients with hypoglycaemia unawareness and/or fear of hypoglycaemia;
• patients with gastroparesis; •
pregnant women with diabetes; and • critically ill patients.
CGM may be used as a tool to reduce glycaemic variability in patients with brittle diabetes to increase time spent in the normoglycaemic range and improve metabolic control.18,34
In patients with fear of hypoglycaemia and hypoglycaemia unawareness, realtime CGM can be used as a monitor to warn against
EUROPEAN ENDOCRINOLOGY
In the future, the incorporation of CGM in a closed-loop system – the artificial pancreas – will be a major breakthrough in diabetes care. For now, CGM may be an aid to achieve adequate metabolic control with peace of mind. n
Christophe De Block is an Associate Professor and Post-doctoral Research Fellow at the University of Antwerp and a Staff Member in the Department of Endocrinology-Diabetology and Metabolism at the Antwerp University Hospital. His main clinical and research interests are related to prediction and prevention of type 1 diabetes, autoimmune polyendocrine syndromes and the application of continuous glucose monitoring, not only in diabetic patients, but also in intensive care units.
However, correct assessment of the magnitude and duration of hyperglycemia is important, and can only be performed using CGM.59,60
demonstrated increased mortality in the intensive glucose control group (81–108mg/dl) compared with conventionally treated patients (
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