Clinical Evaluation of Alternative-Site Glucose Measurements in Patients After Major Cardiac Surgery

Abstract

OBJECTIVE -Tight glycemic control improves outcome in critically ill patients but requires frequent glucose measurements. Subcutaneous adipose tissue (SAT) has been characterized as promising for glucose monitoring in diabetes, but it remains unknown whether it can also be used as an alternative site in critically ill patients. The present study was performed to clinically evaluate the relation of glucose in SAT compared with arterial blood in patients after major cardiac surgery.RESEARCH DESIGN AND METHODS -Forty critically ill patients were investigated at two clinical centers after major cardiac surgery. Arterial blood and SAT microdialysis samples were taken in hourly intervals for a period of up to 48 h. The glucose concentration in dialysate was calibrated using a two-step approach, first using the ionic reference technique to calculate the SAT glucose concentration (SATg) and second using a one-point calibration procedure to obtain a glucose profile comparable to SAT-derived blood glucose (BgSAT). Clinical validation of the data was performed by introducing data analysis based on an insulin titration algorithm. CONCLUSIONS -The results indicate good correlation between SATg and blood glucose in patients after major cardiac surgery. Clinical evaluation of the data suggests that with minor limitations, glucose from SAT can be used to establish tight glycemic control in this patient group. RESULTS Diabetes Care 29:1275-1281, 2006M aintaining critically ill patients within strict glycemic limits can dramatically reduce mortality, risk of infection, and other complications and also has substantial socioeconomic impact (1-3). Due to administration of varying doses of parenteral and enteral nutrition, intravenous infusion of medications that affect glucose metabolism, and development of acute insulin resistance during sepsis, tight glycemic control can only be granted by frequent blood glucose monitoring. Although most critically ill and hospitalized patients have routinely placed venous or arterial access lines, glycemic control is still inadequate.The unmanageable workload for the nursing staff and the prevalent fear of hypoglycemia among critical care physicians hinders the implementation of glycemic control in the intensive care unit (ICU) (4).For diabetic patients, alternative-site glucose testing to achieve better, continuous, or automated feedback control of glycemia has been sought for a long time (5-7). Thanks to minimal invasiveness and good correlation with blood glucose, subcutaneous adipose tissue (SAT) is probably the most investigated alternative sampling site (8 -13). Glucose monitoring in SAT would provide more frequent information about glycemia (trend information) and would therefore also be of benefit for critically ill patients.Microdialysis of SAT has been well established for the investigation of the interstitial fluid glucose profile in relation to blood glucose in healthy individuals and diabetic patients (9). Due to critical illness of patients in the ICU, the perfusion status of variou...

Accuracy of a Novel Noninvasive Transdermal Continuous Glucose Monitor in Critically Ill Patients

“…24 Ellmerer et al established that subcutaneous adipose tissue monitoring is effective in postoperative cardiac surgery patients and can be used to guide intensive insulin dosing. 29 Holzinger et al showed the incidence of hypoglycemia was lower in their study population when CGM was available to the clinical staff. However, CGM did not affect the degree of hyperglycemia when compared to intermittent BG testing, which could possibly be explained by having already achieved tight glycemic control in the intermittent BG testing group.…”

Glucose Control in the ICU

“…Overall, the data suggest a good correlation in most of the patients but the optimal approach would still be the use of intravenous rather than subcutaneous continuous sensor placement. 43 However, the first commercially available intravascular sensors are only now starting to emerge, and their clinical value still needs to be evaluated.…”

Continuous Measurement of Glucose

“…It should be noted that when the results of the CGM were plotted against a blood gas analyzer on an insulin titration grid (showing the correct action with respect to insulin therapy), Ͼ99.1% of the values were in the clinically acceptable treatment zones. 19,20 Sensor Drift CGM sensors all require calibration, some several times a day, to ensure accuracy to meet the manufacturer's specifications. It would be best to calibrate CGM with a CLD or blood gas analyzer, because many of the POC meters lack FDA-required accuracy standards.…”