Continuous Glucose Monitoring During and After Surgery
Phase: NA
Conditions: Diabetes
Sponsor: University of Washington

 
 
 
 
 
 
 
 
 
 
Continuous Glucose Monitoring During and After Surgery 
 
Protocol Version: March 12, 2020 
 
NCT02572856 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Continuous Glucose Monitoring During and After Surgery 
 
Objectives 
During surgery high blood glucose levels, termed hyperglycemia, are commonly 
encountered due to the physiological stress. Hyperglycemia has been associated with 
complications such as surgical site infections, adverse cardiovascular and pulmonary 
events. Optimal glucose control targeted at preventing hyperglycemia has been shown to 
reduce the risk of complications. However, performing optimal glycemic management during 
and after surgery is a significant challenge because varying effects of surgical stress and 
anesthesia interventions produce rapid changes in glucose levels. The current method of 
manually measuring blood glucose every hour or less is grossly inadequate to track 
changes in glucose levels. Continuous Glucose Monitors (CGMs) have the ability to 
automatically measure blood glucose levels in near continuous fashion. Integrating CGMs 
as part of a glycemic control protocol can lead to better management of glucose levels with 
fewer hyperglycemia episodes and lower glucose level variability resulting in better post-
surgical outcomes. The feasibility of using a CGM system during and after surgery for 
glycemic control has not been well studied. Furthermore, prior studies used older generation 
devices that were limited by longer required time for calibration and interactions with 
commonly used medications. We propose a study that aims to evaluate viability of using a 
current generation CGM in surgery patients. 
Dexcom Gen 6 CGM and data loggers will be used for the proposed study. Dexcom Gen 6 
CGM is FDA approved for non-hospital use. Enhancements over previous model, Dexcom 
Gen 4, include better accuracy of glucose measurement, better protection against 
measurement interference from acetaminophen, fewer calibration requirements and longer 
wear time. Dexcom Gen 6 uses the same sensing mechanism as Gen 4 with the 
measurements made non-invasively through a subcutaneous sensor (under the skin). For 
our proposed study we will be using the CGM monitor “Off-label” in a hospital setting in 
surgery patients. For this study the CGM will be used as a secondary monitor not intended 
for patient care. In the operating room and during the patient’s hospitalization, clinical 
providers will continue to use the existing manual glucose measurements (Point of care 
glucose meters or laboratory measurements) for clinical care. The measurements recorded 
by the Dexcom Gen 6 CGM will be blinded (not displayed) so that providers are not able use 
the measured values to inform treatment decisions.    
The primary goal of this study is to evaluate the feasibility of a Continuous Glucose Monitor 
(CGM) in measuring blood glucose levels and trends in surgery patients. The secondary 
goal is to observe and analyze trends in perioperative blood glucose levels to understand 
the dynamic effects of surgical stress and anesthetic agents on blood glucose levels. This 
information will allow development of better intraoperative glucose management strategies 
and protocols. A third goal is to describe and compare blinded CGM (data not available to 
clinician) measures of blood glucose (percentage of time with hyperglycemia, maximum and 
minimum, amplitude of glycemic excursion) to usual care finger sticks and blood draws in 
the preoperative, perioperative and postoperative periods.  
The specific aims of the study are outlined below: 
1) Compare glucose measurements made by a next generation, investigational 
Continuous Glucose Monitor (Dexcom Gen 6 CGM) against usual care, during the 
preoperative, perioperative and postoperative periods. 

2) Describe measures of blood glucose variability, including  percentage of time with 
hyperglycemia, maximum and minimum glucose levles, amplitude of glycemic excursion. 
 
Study Design 
Prospective, single center, evaluation study of a continuous glucose monitor in adult patients 
undergoing elective surgery. 
 
Background 
Multiple studies have shown the benefit of optimal blood glucose management during and after 
surgery. Optimal glucose control avoiding high glucose level (called hyperglycemia) and very 
low glucose level (called hypoglycemia) have been associated with reduction in complications 
such as infection, adverse cardiac, pulmonary and renal events. However, optimal glucose 
management requires frequent monitoring of glucose levels and titration of insulin doses for the 
diabetic population. This places a significant burden on anesthesiologists and nursing staff in a 
busy and critical environment of operating room and post-surgery recovery areas. A continuous 
glucose monitor (CGM) can automatically and frequently monitor glucose levels and obviates 
the need for frequent manual measurement of glucose levels by providers during and after 
surgery. A CGM can facilitate closer monitoring of glucose levels, better glucose management 
and possibly better patient outcomes. 
 
Current CGMs that are marketed have not been evaluated in surgery patients. This study aims 
to evaluate one such CGM (Dexcom G6) in surgery patients. 
 
Study Procedures 
a. Study design 
 
The study will be conducted in a single phase on adult surgical patients with and without 
diabetes at the University of Washington Medical Center. However, after the first 4 patients 
with diabetes are enrolled, a safety evaluation will be performed. The study will be continued 
only if the CGM is determined to be safe and able to make glucose measurements that are 
comparable to those made by the standard point of care (POC) glucose meter. 
The safety evaluation was performed and completed in December 2018. The conclusion 
was the study is safe to continue. 
 
b. Sequence and timing of study procedures  
 
The following procedures will take place for this study for all subjects enrolled:  
 
  
 

 
1. CGM placement: The Dexcom Gen 6 Professional GCM sensor will be placed on 
the subject’s upper arm 2-4 hours prior to surgery. The sensor placement will 
preferably occur in a private room. Placement of the sensor will take around 1 
minute. It is placed subcutaneously under the skin, on the forearm and will be placed 
by a trained member of the research team.  
 
The CGM monitor will be configured to not display the glucose measurements 
and trends (blinded mode; data not available to subject or clinician).  
 
Lastly, the CGM clock will be synchronized to the hospital computer clock. 
 
During surgery 
 
2. Primary CGM Data Measurements: The CGM monitor will travel with the patient to 
the operating room. The CGM will keep a log of the continuous glucose 
measurements every 5 minutes for retrospective download and review. The CGM 
data measurements add no time to the patient’s surgery.  
 
**The institutional protocol for glucose management will be followed using the POC and lab 
glucose measurements as reference. The study will not interfere with the clinical protocol, 
and no one will be able to see or use the blinded CGM values for clinical care.  
 
After surgery (PACU/ICU/Wards) 
 
 
3. Primary CGM Data Measurements: After surgery, the CGM will continue to collect 
continuous measurements. The study team will recalibrate the CGM at specified 
intervals during its postoperative use. The CGM will remain on the subject and 
collect glucose readings for up to 10 days after surgery or until the patient is 
discharged from the hospital whichever occurs earlier.  
 
4. Secondary EMR data: The study team will retrospectively abstract pertinent clinical 
data, including usual care glucose measurements. 
 
 
5. ** The institutional protocol for glucose management will be continued after surgery 
in the PACU, surgical ICU or surgical wards. The study will not interfere with the 
clinical protocol, and the clinical providers will still be unable to see or use the 
blinded CGM values for clinical care. 
 
6. CGM monitor disconnect & cleaning: The CGM sensor and monitor will be 
removed at the end of the study period by either the research coordinator or the 
bedside nurse. All three parts of the CGM device will be disposed of appropriately. 
Additionally, the CGM measurements will be downloaded from the monitor to a 
computer file using a software program provided by Dexcom Inc.