External Carotid Blood Flow in Individuals With Post-Bariatric Hypoglycemia

Inclusion Criteria

• Age 18-70 years of age, inclusive at screening.
• Individuals able to provide informed consent and follow all study procedures, including complete daily food, activity, and symptom diaries, and willingness to provide access to medical record review.
• For healthy control group: individuals without a history of upper gastrointestinal surgery and without reported symptoms of hypoglycemia.
• Individuals with access to personal iPhone running operating system 16 (iOS) or later versions (not feasible for Android platform users) and a password-protected home Wi-Fi network.

Exclusion Criteria

• History of coronary artery disease or presence of 2 or more risk factors including diabetes, uncontrolled hypertension, uncontrolled hyperlipidemia, and active tobacco use.
• History of myocardial infarction, unstable angina or revascularization within the past 6 months.
• History of syncope (unrelated to hypoglycemia) or diagnosed cardiac arrhythmia.
• Documented hypoglycemia occurring in the fasting state (> 12 hours fast).
• Concurrent administration of β-blocker therapy.
• Vigorous physical activity within 24 hours prior to assessment.
• Seizure disorder (other than with suspect or documented hypoglycemia).
• Hematocrit \< 33% (women) or \<36% (men) within the past 6 months.
• History of insulinoma.
• Use of central nervous system-active medications, including: antidepressants, anxiolytics, antipsychotics, stimulants, antiepileptics, sedatives and opioids.
• History of severe neurologic vascular disease (e.g. cerebrovascular disease/stroke).
• History of previous diseases associated with dysautonomia (e.g. multiple system atrophy, multiple sclerosis, Parkinson's disease).
• Impaired hepatic function (aspartate amino transaminase and/or alanine amino transaminase >2x upper limit of normal range), as determined within the past 6 months.
• Impaired renal function (serum creatinine >1.5 mg/dL), as determined within the past 6 months.
• Serious psychiatric or substance abuse disorders (e.g. alcohol, opioid, cocaine use disorder), as judged by the study investigator.
• Non-consent or inability to comply with study procedures.
• Current pregnancy and/ or lactation.
• Vulnerable individuals (e.g., fetuses, children, prisoners) and those judged by the investigator to be unsuitable for the study.
• Individuals wearing earrings or other jewelry in the left ear who are unable or unwilling to remove them for the duration of the study.
• Unwillingness to wear study masked CGM for duration of study