CGM Can Be Used in the ICU to Monitor Patients With T2D

Continuous glucose monitoring (CGM) can be a useful way to reduce the frequency of blood gas monitoring among patients with type 2 diabetes (T2D) receiving care in the intensive care unit (ICU), according to a new study.

However, a new report published in Acta Anaesthesiologica Scandinavica also found some limitations to the testing method.

The study authors noted that hypoglycemia is a serious risk and a significant cause of excess mortality among people with T2D who are admitted to the ICU. As a result, such patients require vigilant monitoring.

“In contemporary ICUs, insulin therapy is commonly guided by intermittent blood gas glucose analyses, which has a significant impact on staff workload and may counteract timely recognition of hypoglycemia and attenuation of glucose variability,” the authors wrote.

In recent years, CGM has become a common method of day-to-day blood glucose monitoring for patients with T2D, prompting some to wonder whether it might also be useful in a hospital setting. On the positive side, CGM systems allow for instant data about patient glucose levels and may therefore reduce the need for staff testing. However, the authors said, the devices need frequent calibration and have been associated with thrombosis. In addition, it is unclear whether such devices are equally reliable in patients receiving intravenous glucose.

In the new study, the investigators wanted to see how well CGM compared with blood gas testing, which they said is the current gold standard for critically ill patients. They recruited 15 patients with T2D who were hospitalized in the ICU and began monitoring the blood glucose levels of those patients using the FreeStyle Libre CGM device. In addition, they recruited 105 controls who also had T2D and required insulin, but who had had at least 10 blood glucose values. In both groups, the target glucose range was 10 to 14 mmol/L, with patients receiving insulin to stay within those ranges.

The authors calculated the accuracy of CGM by comparing matched samples of CGM readings and blood gas glucose. A total of 483 matched glucose values were analyzed.

Overall, the mean absolute relative difference (MARD) between the matched controls was 11.5% (95% CI, 10.7%-12.3%).However, the investigators found that the difference decreased over time. The MARD was 13.8% during the first 48 hours of CGM initiation, 10.9% between 48 and 96 hours, and 8.9% past 96 hours. They found patients using CGM had 30% fewer blood gas samples.

“CGM use was not associated with glucose variability as determined by glycemic lability index or standard deviation of blood glucose,” they study authors wrote.

They said their findings suggest that CGM deserves more consideration as a possible tool in the ICU setting. However, because there were no cases of hypoglycemia among patients undergoing CGM, they cannot say whether the monitoring could be used to prevent hypoglycemia.

They noted that their study had limitations, including the relatively small sample size and the lack of a randomized control design. They also noted that CGM was less accurate, with glucose levels below 10 mmol/L, in particular in the first 48 hours after CGM use.

“Our findings justify further assessment of the value of CGM in preventing hypoglycemia and attenuating glucose variability in the ICU and whether such potential benefits translate into improved clinical outcomes,” they concluded.

Reference:

Mårtensson J, Cutuli S, Yanase F, et al. Glycemic control and blood gas sampling frequency during continuous glucose monitoring in the intensive care unit: a before-and-after study. Acta Anaesthesiol Scand. Published online October 20, 2022. doi:10.1111/aas.14159