Continuous Glucose Monitoring to Reduce Hypoglycemia and Improve Safety After Gastric Surgery

Not Applicable

Completed

Conditions: Hypoglycemia
Hypoglycemia, Reactive

Interventions: Device: Dexcom CGM masked
Device: Dexcom CGM unmasked

Registration Number: NCT03353415

Lead Sponsor: Joslin Diabetes Center

Brief Summary: The purpose of this study is to see if the use of a continuous glucose monitor (CGM) by people who experience low blood sugars (hypoglycemia) after gastric surgery can help reduce the number and severity of low blood sugar episodes.

Detailed Description: The CGM devices used in this study are approved by the Food and Drug Administration (FDA) for monitoring the glucose levels of people with diabetes. The investigators of this study are looking to see if these CGM devices are able to benefit people who have had gastric surgery and experience low blood sugar episodes, which can be asymptomatic and lead to complications, impairing safety. This study involves wearing a CGM sensor/transmitter during first a masked phase (unable to see CGM sensor glucose levels), followed by an unmasked phase (able to see and respond to sensor glucose levels and alarms). Participants are asked to regularly record fingerstick (capillary) blood sugar values and any symptoms experienced, as well as a record of treatments for symptoms and glucose levels.

Participants attend three to five study visits: 5 visits for participants who wore the Dexcom G4, and 3 visits for participants who wore the Dexcom G6. The Dexcom G4 became unavailable during the course of the study when the G6 was introduced. (The Dexcom G4 had a 7 day wear period versus a 10 day wear period for the G6. As the G6 has a longer wear period, the frequency of the study visits was able to be decreased).

This study also involves the use of a fitness tracker, which will be worn for the duration of the study and returned at the end of the study.

Participants wearing the Dexcom G4 device were able to keep the Dexcom G4 CGM receiver and transmitter (this was not possible with the Dexcom G6 system).

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 26

Inclusion Criteria

Males or females diagnosed with ongoing post-bariatric or post-gastric surgery hypoglycemia with prior episodes of neuroglycopenia
Age 18-65 years of age, inclusive, at screening
Willingness to provide informed consent and follow all study procedures, including attending all scheduled visits.

Exclusion Criteria

Documented hypoglycemia occurring in the fasting state (> 12 hours fast);
Chronic kidney disease stage 4 or 5 (including end-stage renal disease);
Hepatic disease, including serum alanine transaminase (ALT) or aspartate aminotransferase (AST) greater than or equal to 3 times the upper limit of normal; hepatic synthetic insufficiency as defined as serum albumin < 3.0 g/dL; or serum bilirubin >2.0;
Congestive heart failure, New York Heart Association (NYHA) class II, Ill or IV;
History of myocardial infarction, unstable angina or revascularization within the past 6 months or 2 or more risk factors for coronary artery disease including diabetes, uncontrolled hypertension, uncontrolled hyperlipidemia, and active tobacco use.
History of syncope (unrelated to hypoglycemia) or diagnosed cardiac arrhythmia
Concurrent administration of beta-blocker therapy;
History of a cerebrovascular accident;
Seizure disorder (other than with suspect or documented hypoglycemia);
Active treatment with any diabetes medications except for acarbose;
Active treatment with octreotide or diazoxide;
Active malignancy, except basal cell or squamous cell skin cancers;
Personal or family history of pheochromocytoma or disorder with increased risk of pheochromocytoma (multiple endocrine neoplasia (MEN) 2, neurofibromatosis, or Von Hippel-Lindau disease);
Known insulinoma;
Major surgical operation within 30 days prior to screening;
Hematocrit< 33%;
Bleeding disorder, treatment with warfarin, or platelet count <50,000;
Blood donation (1 pint of whole blood) within the past 2 months;
Active alcohol abuse or substance abuse;
Current administration of oral or parenteral corticosteroids;
Pregnancy and/ or lactation: For women of childbearing potential: there is a requirement for a negative urine pregnancy test and for agreement to use contraception during the study and for at least 1 month after participating in the study. Acceptable contraception includes birth control pill/patch I vaginal ring, Depo-Provera, Norplant, an intrauterine device (IUD), the double barrier method (the woman uses a diaphragm and spermicide and the man uses a condom), or abstinence.
Use of an investigational drug within 30 days prior to screening.

Study & Design

Study Type: INTERVENTIONAL

Study Design: SEQUENTIAL

Arm && Interventions

Group	Intervention	Description
Masked CGM Wear (Phase 1)	Dexcom CGM masked	Each participant will wear the Dexcom CGM for two sequential phases. During the first phase, participants will not be able to read the sensor glucose levels (masked).
Unmasked CGM Wear (Phase 2)	Dexcom CGM unmasked	In the second phase, participants will be able to read the sensor glucose levels (unmasked). Frequency of hypoglycemia will be compared between the two phases of the study.

Primary Outcome Measures

Name	Time	Method
Percentage of Time Sensor Glucose <70 mg/dL in the Masked Versus the Unmasked Phase.	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.	The primary outcome will be time spent in hypoglycemic glucose range as measured by percent time sensor glucose is \<70 mg/dl, comparing the masked versus the unmasked phases.
Percentage of Time Sensor Glucose <54 mg/dL in the Masked Versus the Unmasked Phase	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.	The primary outcome will be time spent in hypoglycemic glucose range as measured by percent time sensor glucose is \<60 mg/dl, comparing the masked versus the unmasked phases.
Percentage of Time Sensor Glucose <60mg/dL in the Masked Versus the Unmasked Phase	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.	The primary outcome will be time spent in hypoglycemic glucose range as measured by percent time sensor glucose is \<60 mg/dl, comparing the masked versus the unmasked phases.

Secondary Outcome Measures

Name	Time	Method
Glycemic Variability as Measured by the Standard Deviation of Sensor Glucose Level Data During Periods of CGM Wear, Masked Versus Unmasked Phase	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.
1 Hour Continuous Overall Net Glycemic Action (CONGA) for Sensor Glucose Data During Periods of CGM Wear, Masked Versus Unmasked Phase	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.
Total Number of Hypoglycemic Events During the Masked Versus the Unmasked Phases of CGM Wear, as Defined by a Sensor Glucose <70 mg/dL, for at Least 15 Minutes	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.	Hypoglycemic events are defined as having glucose \<70 mg/dL for at least 15 minutes, ending when glucose \> the threshold. Hypoglycemic event values were normalized by dividing the number of events by the number of days of data.
Median Sensor Glucose Level During Masked Versus Unmasked Phases of Wear	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.
Peak Sensor Glucose Level During Masked Versus Unmasked Period of CGM Wear	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.	expressed as median and median standard deviation
Percentage of Time Sensor Glucose Level >250 mg/dL During Periods of CGM Wear, Masked Versus Unmasked Phase	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.
2 Hours, Continuous Overall Net Glycemic Action (CONGA) for Sensor Glucose Data During Periods of CGM Wear, Masked Versus Unmasked Phase	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.
Total Number of Hypoglycemic Events Defined by a Sensor Glucose <54 mg/dL, for at Least 15 Minutes, During the Masked Versus Unmasked CGM Phase	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.	Hypoglycemic events are defined as having glucose \<54 mg/dL for at least 15 minutes, ending when glucose \> the threshold. Hypoglycemic event values were normalized by dividing the number of events by the number of days of data.
Nadir Sensor Glucose Level During Masked Versus Unmasked Period of CGM Wear	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.
Percentage of Time Sensor Glucose Level >180 mg/dL During Period of CGM Wear, Masked Versus Unmasked Phase	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.
Mean Amplitude of Glycemic Excursion (MAGE) of Sensor Glucose Levels During Periods of CGM Wear, Masked Versus Unmasked Phase	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.
4 Hours, Continuous Overall Net Glycemic Action (CONGA) for Sensor Glucose Data During Periods of CGM Wear, Masked Versus Unmasked Phase	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.
Percent of Time Sensor Glucose 70-180 mg/dL During Period of CGM Wear, Masked Versus Unmasked Phase	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.
Mean Sensor Glucose Level During Masked Versus Unmasked Phases of Wear	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.
Sensor Glucose Level Range (Highest Sensor Glucose Minus Lowest Sensor Glucose mg/dL) During Masked Versus Unmasked Period of CGM Wear	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.	The sensor glucose level range is derived from the difference between the highest sensor glucose levels minus the lowest sensor glucose level (mg/dL).
Mean Coefficient of Variation of Sensor Glucose Data During Period of CGM Wear, Masked Versus Unmasked Phase	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.
24 Hour Continuous Overall Net Glycemic Action (CONGA) for Sensor Glucose Data During Periods of CGM Wear, Masked Versus Unmasked Phase	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.	CONGA assesses glucose variability within a predetermined time window - 24 hours in this case. Calculation of this parameter is based on the assessment of the differences between glucose values measured at regular time intervals, then on the standard deviation (SD) of these differences
Total Number of Hypoglycemic Events Defined by a Sensor Glucose <60 mg/dL, for at Lease 15 Minutes, During the Masked Versus Unmasked CGM Phase	28 days for those participants wearing Dexcom G4, and 20 days for participants wearing Dexcom G6.	Hypoglycemic events are defined as having glucose \<60 mg/dL for at least 15 minutes, ending when glucose \> the threshold. Hypoglycemic event values were normalized by dividing the number of events by the number of days of data.