Point and trend accuracy of continuous glucose monitoring using intravenous microdialysis in critically ill patients

Introduction

Insulin infusion in critically ill patients mandates frequent measurements of the blood glucose level [1]. Microdialysis is a well-established technology that offers the opportunity to sample blood analytes with high accuracy, without the need for drawing blood samples [2, 3]. We aimed to determine point and trend accuracy of microdialysis-based continuous glucose monitoring (CGM) (EIRUS®; Maquet Critical Care AB, Solna, Sweden).

Methods

Patients with an expected stay in the ICU of >48 hours needing an arterial catheter and a central venous catheter (CVC) were eligible. For a maximum of 3 days, during 8 hours per day, 125 μl blood was drawn from the arterial line every 15 minutes. Point accuracy was expressed using Clarke error grids, Bland-Altman plots and glucose prediction error analysis [4, 5]. Trend accuracy was expressed using continuous glucose error grid analysis [6].

Results

Three-hundred and fifty-four paired samples were obtained from seven patients (66 (59 to 79) years old, APACHE II score 23 (20 to 28), 51 (19 to 77) samples per patient). Point accuracy: 91% of paired values were in zone A, with the remaining 9% of the values in zone B in the Clarke error grid. In the Bland-Altman, bias was 5.4 mg/dl with an upper limit of agreement of 32.5 mg/dl and a lower level of agreement of -21.8 mg/dl. Glucose prediction error analysis showed that 91% of the values ≥75 mg/dl within 20% of the values measured by the blood gas analyzer were within range. Trend accuracy: in the rate error grid of the continuous glucose error grid analysis, 96% of the paired values were in zone A, 3.7% were in zone B and 0.3% were in zone C.

Conclusion

Point and trend accuracy of the tested microdialysis-based CGM are good in critically ill patients.

Acknowledgement

Maquet Critical Care AB provided two CGM systems and disposables for the duration of the study, but had no influence on study design or study reporting.