title: Baroreflex Sensitivity Impairment During Hypoglycemia: Implications for Cardiovascular Control.
abstract: Studies have shown associations between exposure to hypoglycemia and increased mortality, raising the possibility that hypoglycemia has adverse cardiovascular effects. In this study, we determined the acute effects of hypoglycemia on cardiovascular autonomic control. Seventeen healthy volunteers were exposed to experimental hypoglycemia (2.8 mmol/L) for 120 min. Cardiac vagal baroreflex function was assessed using the modified Oxford method before the initiation of the hypoglycemic-hyperinsulinemic clamp protocol and during the last 30 min of hypoglycemia. During hypoglycemia, compared with baseline euglycemic conditions, 1) baroreflex sensitivity decreases significantly (19.2 ± 7.5 vs. 32.9 ± 16.6 ms/mmHg, P < 0.005), 2) the systolic blood pressure threshold for baroreflex activation increases significantly (the baroreflex function shifts to the right; 120 ± 14 vs. 112 ± 12 mmHg, P < 0.005), and 3) the maximum R-R interval response (1,088 ± 132 vs. 1,496 ± 194 ms, P < 0.001) and maximal range of the R-R interval response (414 ± 128 vs. 817 ± 183 ms, P < 0.001) decrease significantly. These findings indicate reduced vagal control and impaired cardiovascular homeostasis during hypoglycemia.
authors.affiliation: Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA Section of Endocrinology, Diabetes and Metabolism, Department of Medicine, Temple University School of Medicine, Philadelphia, PA.
authors.forename: Ajay D
authors.initials: AD
authors.lastname: Rao
authors.affiliation: Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA.
authors.forename: Istvan
authors.initials: I
authors.lastname: Bonyhay
authors.affiliation: Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
authors.forename: Joel
authors.initials: J
authors.lastname: Dankwa
authors.affiliation: Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
authors.forename: Maria
authors.initials: M
authors.lastname: Baimas-George
authors.affiliation: Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
authors.forename: Lindsay
authors.initials: L
authors.lastname: Kneen
authors.affiliation: Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA.
authors.forename: Sarah
authors.initials: S
authors.lastname: Ballatori
authors.affiliation: Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA rfreeman@bidmc.harvard.edu.
authors.forename: Roy
authors.initials: R
authors.lastname: Freeman
authors.affiliation: Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
authors.forename: Gail K
authors.initials: GK
authors.lastname: Adler
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000503:physiopathology*; D017704:Baroreflex; D001794:Blood Pressure / Q000502:physiology*; D002319:Cardiovascular System / Q000503:physiopathology*; D005260:Female; D015309:Glucose Clamp Technique; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007003:Hypoglycemia / Q000503:physiopathology*; D008297:Male; D012021:Reflex, Abnormal; D014630:Vagus Nerve / Q000503:physiopathology*; D055815:Young Adult