Continuous intra-arterial blood glucose monitoring using quenched fluorescence sensing: a product development study

Continuous glucose monitoring (CGM) has the potential to improve the management of blood glucose (BG) and so improve patient safety and outcomes in intensive care units. The GluCath Intravascular CGM (IV-CGM) System (GluMetrics) uses a novel quenched chemical fluorescence sensing mechanism to measure BG.

We aimed to assess the safety and performance of the GluCath IV-CGM for a 24-hour period in 20 patients admitted to an ICU after cardiac surgery.

Heparin-bonded sensors were deployed via a standard 20-gauge radial arterial catheter inserted for routine care in 21 participants after cardiac surgery. Sensors were inserted shortly after ICU admission and BG was monitored for up to 24 hours. After an in vivo calibration, the system recorded BG every minute. Ultrasound examinations checked for sensor position and the presence of thrombus. Outcome measures were qualitative (ease of use, interference with clinical care, blood pressure monitoring and blood sampling) and quantitative (accuracy in comparison with hourly measurements from a reference analyser). BG was managed according to usual protocols.

Of 21 sensors deployed, one failed and one was malpositioned due to operator error. A total of 488 reference samples were collected, with BG concentrations ranging from 4.7mmol/L to 13.4 mmol/L. Calibration samples, samples from the malpositioned sensor and six samples affected by technical errors were excluded. Of 437 paired sensor and reference measurements used to assess accuracy, 353 (80.8%) met International Organization for Standardization standard 15197: 2003 criteria (within 20% of reference when BG≥4.2mmol/L). The aggregate mean absolute relative difference (MARD) was 13.0%, with the MARD for individual sensors ranging from 4.7% to 33.5%. Preremoval ultrasounds detected clinically insignificant intravascular thrombus in five of 21 patients (23.8%). No sensor interfered with clinical care, haemodynamic monitoring or blood sampling. There were no device related serious adverse events.

In this product development study, use of the GluCath system for 24 hours after cardiac surgery had no adverse effect on haemodynamic monitoring, arterial blood sampling or clinical care. Overall accuracy was acceptable in the context of the first phase of a product development study.