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

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.

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).

Eligibility Criteria:
Inclusion Criteria:

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

Exclusion Criteria:

1. Documented hypoglycemia occurring in the fasting state (\> 12 hours fast);
2. Chronic kidney disease stage 4 or 5 (including end-stage renal disease);
3. 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;
4. Congestive heart failure, New York Heart Association (NYHA) class II, Ill or IV;
5. 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.
6. History of syncope (unrelated to hypoglycemia) or diagnosed cardiac arrhythmia
7. Concurrent administration of beta-blocker therapy;
8. History of a cerebrovascular accident;
9. Seizure disorder (other than with suspect or documented hypoglycemia);
10. Active treatment with any diabetes medications except for acarbose;
11. Active treatment with octreotide or diazoxide;
12. Active malignancy, except basal cell or squamous cell skin cancers;
13. Personal or family history of pheochromocytoma or disorder with increased risk of pheochromocytoma (multiple endocrine neoplasia (MEN) 2, neurofibromatosis, or Von Hippel-Lindau disease);
14. Known insulinoma;
15. Major surgical operation within 30 days prior to screening;
16. Hematocrit\< 33%;
17. Bleeding disorder, treatment with warfarin, or platelet count \<50,000;
18. Blood donation (1 pint of whole blood) within the past 2 months;
19. Active alcohol abuse or substance abuse;
20. Current administration of oral or parenteral corticosteroids;
21. 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.
22. Use of an investigational drug within 30 days prior to screening.