Glucose control in the ICU: is there a time for more ambitious targets again?

Accuracy and Stability of a Subcutaneous Flash Glucose Monitoring System in Critically Ill Patients

BACKGROUND

Flash glucose monitoring (FGM) systems can reduce glycemic variability and facilitate blood glucose management within the target range. However, in critically ill patients, only small (n < 30) studies have examined the accuracy of FGM and none have assessed the stability of FGM accuracy. We evaluated the accuracy and stability of FGM in critically ill patients.

METHOD

This was a single-center, retrospective observational study. We included a total of 116 critically ill patients who underwent FGM for glycemic control. The accuracy of FGM was assessed as follows using blood gas glucose values as a reference: (1) numerical accuracy using the mean absolute relative difference, (2) clinical accuracy using consensus error grid analysis, and (3) stability of accuracy assessing 14-day trends in consensus error grid distribution.

RESULTS

FGM sensors remained in situ for a median of 6 [4, 11] days. We compared 2014 pairs of measurements between the sensor and blood gas analysis. Glucose values from the sensor were consistently lower, with a mean absolute relative difference of 13.8% (±16.0%), than those from blood gas analysis. Consensus error grid analysis demonstrated 99.4% of the readings to be in a clinically acceptable accuracy zone. The accuracy of FGM was stable across the 14 days after device insertion.

CONCLUSIONS

FGM had acceptable reliability and accuracy to arterial blood gas analysis in critically ill patients. In addition, the accuracy of FGM persisted for at least 14 days. Our study promotes the potential usefulness of FGM for glycemic monitoring in critically ill patients.

The Clinical Benefits and Accuracy of Continuous Glucose Monitoring Systems in Critically Ill Patients-A Systematic Scoping Review

Continuous Glucose Monitoring (CGM) systems could improve glycemic control in critically ill patients. We aimed to identify the evidence on the clinical benefits and accuracy of CGM systems in these patients. For this, we performed a systematic search in Ovid MEDLINE, from inception to 26 July 2016. Outcomes were efficacy, accuracy, safety, workload and costs. Our search retrieved 356 articles, of which 37 were included. Randomized controlled trials on efficacy were scarce (n = 5) and show methodological limitations. CGM with automated insulin infusion improved time in target and mean glucose in one trial and two trials showed a decrease in hypoglycemic episodes and time in hypoglycemia. Thirty-two articles assessed accuracy, which was overall moderate to good, the latter mainly with intravascular devices. Accuracy in critically ill children seemed lower than in adults. Adverse events were rare. One study investigated the effect on workload and cost, and showed a significant reduction in both. In conclusion, studies on the efficacy and accuracy were heterogeneous and difficult to compare. There was no consistent clinical benefit in the small number of studies available. Overall accuracy was moderate to good with some intravascular devices. CGM systems seemed however safe, and might positively affect workload and costs.

Evaluation and treatment of hyperglycemia in critically ill patients

The hyperglycemic reaction to stress is part of adaptive metabolic response to critical illness, especially hypoxia, hemorrhage and sepsis. It involves neuro-endocrine and immune pathways leading to the development of insulin resistance and hepatic glucose production by gluconeogenesis and glycogenolysis. Over the last years the concept of stress related hyperglycemia has been replaced by the concept of dysglycemia and its three domains: hyperglycemia, hypoglycemia and glycemic variability. Each of the three domains is independently associated with increased risk of mortality in patients admitted in intensive care unit and non critically ill patients, both medical and surgical. The strongest association with mortality is demonstrated for hypoglycemia, with additive negative effects for hyperglycemia and glycemic variability. The influence of pre-existing diabetes mellitus on the relation of the three domains of dysglycemia with mortality is not clear, suggesting that patients affected by diabetes mellitus may tolerate a larger glucose variability. Advances in continuous glucose monitoring systems and insulin therapy algorithms may reduce the development of glycemic variability and hypoglycemia, but the benefits in clinical practice have not yet been established in clinical trials.