Background: Evidence suggests that glycemic control provides clinical benefit to critically ill patients. The Extracorporeal Glucose Monitoring System (EGMS), Medtronic Minimed, Northridge, CA) has been developed to measure real-time, continuous blood glucose concentrations in patients on extracorporeal bypass. This pilot study reports the first in vitro and in vivo evaluations of EGMS in an extracorporeal circuit.
Methods: In an in vitro study, three EGMS sensors were inserted in a neonatal extracorporeal circuit. Circuit blood glucose levels were altered by saline dilution and dextrose infusion. EGMS sensors were then inserted into the venous return limb of the extracorporeal circuit in a cohort of six critically ill infants on extracorporeal life support (ECLS). Continuous glucose measurements were compared with laboratory and bedside glucose values at predefined intervals. Linear regression analyses and the Clarke error grid were constructed to analyze device accuracy.
Results: All three in vitro EGMS sensors recorded real-time data without interruption for 48 h. EGMS glucose measurements closely correlated with reference levels (R (2) = 0.93). EGMS glucose values demonstrated an approximate 7-10 min lag while glucose concentrations were rapidly changing. Eight EGMS devices were inserted into six neonates on ECLS on day of life 6 +/- 3. EGMS correlated well with laboratory glucose (R2 = 0.61) and bedside glucose during a hyperinsulinemic euglycemic clamp (R2 = 0.78). On the Clarke error grid, 98% of readings were within zones A and B using laboratory glucose as reference, and 100% were within zones A and B using bedside glucose measurements. Blood glucose range during the in vitro study was 19-295 mg/dL and during the in vivo study was 80-257 mg/dL.
Conclusions: This pilot study suggests that EGMS is a reliable tool for measuring continuous blood glucose in critically ill patients connected to an extracorporeal circuit, although important limitations exist. Potential applications of this technology include intensive glucose monitoring in patients on ECLS, cardiopulmonary bypass, and renal replacement therapy.