Continuous glucose monitoring using the SCGM1 system in postcardiothoracic surgery patients

Background and aims

Tight glycaemic control (TGC) has proven to reduce mortality and morbidity in critically ill patients. However, in many ICUs implementation of TGC in daily practice is still suboptimal due to the risk of hypoglycaemia and the increased work demands for the ICU nursing staff. Continuous glucose monitoring (CGM) in the interstitial fluid (ISF) might be an alternative to improve the adjustment of insulin therapy without causing additional workload. The aim of the study was to investigate CGM in the ISF in ICU patients using a microdialysis-based monitoring system.

Materials and methods

Twenty patients (male/female: 15/5; age 69 ± 7 years, nondiabetics/diabetics: 14/6; BMI 28.2 ± 4.9 kg/m², APACHE II score: 11.0 ± 3.5) with a glucose level higher than 6.7 mmol/l were investigated in ICU after cardiothoracic surgery. A microdialysis catheter (CMA 60), which is part of the SCGM1 system (Roche Diagnostics, Mannheim, Germany), was inserted into the subcutaneous adipose tissue of the abdomen. In all patients, arterial glucose was measured hourly to describe the glucose profile until the end of the ICU stay, but for a maximum period of 48 hours.

Results

The mean duration of glucose monitoring was 36 ± 15 hours. Eighteen out of 20 data could be analysed (two systems were excluded due to technical failure of the system). The mean blood glucose value was 7.2 ± 1.4 mmol/l (130 ± 25 mg/dl). The mean Pearson correlation coefficient between blood and the SCGM1 system reading was rBG-SCGM = 0.808. In addition the correlation for different calibration intervals (6–12–24 hours) of the SCGM1 system was quantified with several evaluation methods (method of residuals, modified error grid analysis [mEGA], predicted error sum of the squares [%PRESS], mean absolute difference [MAD], coefficient of correlation).

Table 1 (abstract P254)

Conclusion

Our data indicate that ISF is a promising site for CGM in critically ill patients. An implementation of this approach is microdialysis in combination with a glucose sensor. However, systems still have to be improved to be suitable for routine care in the ICU.