Continuous Glucose Monitoring With a Subcutaneous Sensor During Critical Illness and Surgery

Continuous Glucose Monitoring With a Subcutaneous Sensor During Critical Illness and Surgery

We hypothesize that measurements of interstitial fluid (ISF) glucose by the FreeStyle Navigator (Abbot Diabetes Care), a continuous glucose monitoring system, will correlate with blood glucose (BG) values in surgical and ICU patients with a clinically useful degree of accuracy.

Critically ill patients treated with intensive insulin therapy will be monitored for up to 72 hours with the Freestyle Navigator continuous glucose monitor. The device display will be disabled so that continuous glucose monitoring results will not be available to care givers, although low (<60 mg/dL) and high (>250 mg/dL) threshold audio alarms will be enabled. Blood glucose monitoring will be performed according to the usual practice for patients treated with intensive insulin therapy in each intensive care unit, except that additional blood glucose measurements will be performed in response to Freestyle Navigator threshold alarm. All blood glucose management decisions will be made according to intensive insulin therapy protocol in each unit. Freestyle Navigator data will be downloaded from the device after each subject has completed the monitoring period. Blood glucose values obtained in the course of usual care, or in response to Freestyle Navigator threshold alarms, will be compared with time-matched Freestyle Navigator values to assess device accuracy and alarm sensitivity and specificity.

Inclusion Criteria:

• Patients admitted to the general surgical ICU (SICU), medical ICU (MICU), cardiac surgery intensive care unit (CSICU), or neurological intensive care unit (NeuroICU), are being treated with IIT, and have an arterial line in place
• Patients scheduled for open cardiac surgery or craniotomy that have diabetes mellitus or will be given high dose glucocorticoids. All of these patient will have an arterial line placed at the time of surgery as a part of their usual care

Exclusion Criteria:

• Age less than 18 years
• Enrollment in another clinical trial that modifies their glucose management (e.g. trial of modified IIT algorithm or modified glucose monitoring regimen)

In order to obtain adequate representation of patients with physiological alterations that might decrease correspondence between blood and ISF glucose, we will recruit 50 subjects in each of five groups:

1. Patients undergoing craniotomy who are either diabetic or will be given high dose corticosteroids
2. Diabetic patients undergoing open cardiac surgery
3. Patients admitted to one of the participating ICUs with an arterial line in place and receiving IIT who are vasopressor dependent, defined by continuous infusion of at least 60 mg/min phenylephrine, 5 mg/min norepinephrine, or 10 mg/kg/min of dopamine, or any combination of two agents for at least 90 continuous minutes in the last 8 hours
4. Patients admitted to one of the participating ICUs with an arterial line in place and receiving IIT with pitting peripheral or dependent edema, defined by the persistence of pitting to at least 5 mm depth for 5 seconds after pressure is applied to a dependent area of the trunk or two limbs.
5. Critically ill patients admitted to one of the participating ICUs with an arterial line in place and receiving IIT who do not fall into groups 1-4.