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

Study Overview
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Brief Summary
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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.

Detailed Description
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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.

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

Conditions
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Critical Illness

Intervention / Treatment
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* Device: Freestyle Navigator


Participation Criteria
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Eligibility Criteria
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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: Patients undergoing craniotomy who are either diabetic or will be given high dose corticosteroids Diabetic patients undergoing open cardiac surgery 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 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. 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.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Freestyle Navigator<br>Continuous monitoring with the Freestyle Navigator for 72 hours or until discharge from the ICU | Device: Freestyle Navigator<br>* Continuous glucose monitoring with the Freestyle Navigator for 72 hours or until discharge from the ICU<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Sensitivity and Specificity of Navigator Threshold Alarms for Hypoglycemia (<60 mg/dl). |  | 72 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Sensitivity and Specificity of Navigator Threshold Alarms for Hyperglycemia (>240 mg/dl). |  | 72 hours | 
| Accuracy of Navigator CGM as Compared to Reference Blood Glucose Values | Mean Absolute Relative Difference (MARD) of Navigator CGM compared with reference blood glucose values | 72 hours | 
| Sensitivity and Specificity of Navigator Projected Low Blood Sugar Alarm Criteria Calculated for Events Defined by a Low Reference BG Value (< 60 mg/dL) |  | 72 hours | 
| Sensitivity and Specificity of Navigator Projected High Blood Sugar Alarm Criteria Calculated for Events Defined by a High Reference BG Value (> 250 mg/dl) |  | 72 hours | 
| Percentage of Readings in Different Blood Sugar Ranges as Shown by Point of Care Testing: | Percentage of readings in different blood sugar ranges as shown by point of care testing: < 60 mg/dl 61-120 mg/dl 121-180 mg/dl 181-240 lmg/dl >240 mg/dl | 72 hours | 
| Navigator CGM Accuracy by Category | Mean Absolute Relative Difference (MARD) between the Navigator CGM and reference blood glucose values by category (1, Neurosurgery; 2, Cardiac Surgery; 3, Hypotensive/Vasopressor; 4, Edema; 5, None of the Above) | 72 hours | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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hyperglycemia, hypoglycemia, insulin, critical illness, intensive insulin therapy, continuous glucose monitoring, CGM, interstitial fluid glucose, intensive care unit, Blood glucose