Hyperglycemia in Critically Ill Patients

Glucose control in critically ill patients has been debated since the 2000s. It is known that many critically ill patients, both those with and without diabetes, develop hyperglycemia (high blood sugar level). This condition happens because the body becomes resistant to insulin and makes more sugar.

The Risk of Hyperglycemia and Intensive Insulin Therapy in Critically Ill Patients

Hyperglycemia is linked to increased adverse outcomes like death, more health problems, and deep wound infections, especially for patients undergoing cardiac surgery. The Leuven studies showed that tight glycemic control (keeping blood sugar levels low) using intensive insulin therapy (IIT), or giving insulin by injection, could reduce the risk of death or illness in critically ill patients. However, further studies have found that this finding may not be the case. Some studies have shown that IIT can increase the risk of death from hypoglycemia (low blood sugar).

What is a Continuous Glucose Monitoring System and Intravascular Microdialysis?

An accurate real-time continuous glucose monitoring (CGM) system may help manage and treat abnormal glucose levels and fluctuations, particularly in intensive care unit cases. Intravascular microdialysis is a method for continuously measuring blood glucose without blood extractions.

In this study, we aimed to assess the accuracy of this method in patients undergoing cardiac surgery.

The Study on Continuous Glucose Monitoring through Intravascular Microdialysis for Patients Undergoing Cardiac Surgery

The intravenous Eirus™ microdialysis system was used to continuously measure the blood glucose levels of 48 patients undergoing cardiac surgery. It consists of a single lumen catheter (SLC) placed in the heart’s superior vena cava and near the central venous catheter, through which postoperative infusions were administered. The SLC was connected to the Eirus™ sensor and monitor system. The patients were monitored from the time they arrived in the ICU after surgery up to 48 hours or until they were discharged from the ICU. For comparison, arterial blood samples were taken every hour and analyzed in a blood gas analyzer. The resulting blood gas glucose values were used as reference values.

The Results

Using Clarke error grid analysis, 100% of the paired samples were in region AB, and 99% were in region A. This result indicates a high accuracy between the blood glucose levels measured by the microdialysis system compared with those recorded from the blood gas analysis. The mean relative difference between arterial blood gas values and microdialysis values was 0.2%, and the mean absolute relative difference was 5%. Bland-Altman study showed bias ± limits of agreement were 0.02 ± 1.1 millimoles/liter. According to the International Organization for Standardization criteria, 99.2% of the paired samples were correct. No hypoglycemia was seen among the patients. In the hyperglycemic range, there was increased bias, as seen in the Bland-Altman analysis. There were no complications observed caused by the microdialysis catheter. There was no loss of recovery observed as an indicator of blood clotting.

The Conclusion

This study shows that intravascular microdialysis is an accurate, useful, and safe method for continuous measurement of glucose in critically ill patients for up to 48 hours. To what extent this method may improve glucose control with regard to hyperglycemia, hypoglycemia, and glucose variability remains to be further evaluated.

Reference

Evaluation of a Continuous Blood Glucose Monitoring System Using Central Venous Microdialysis