Severe hypoglycaemia unawareness is associated with an early decrease in vigilance during hypoglycaemia

• Published in: Psychoneuroendocrinology 1996-04, Vol.21 (3), p.295-312
• Main Authors: Howorka, Kinga, Heger, Georg, Schabmann, Alfred, Anderer, Peter, Tribl, Gotthard, Zeitlhofer, Josef
• Format: Article
• Language: English
• Subjects: Adult; Arousal - physiology; Biological and medical sciences; Blood Glucose - metabolism; Cognitive function; Diabetes Mellitus, Type 1 - physiopathology; Diabetes Mellitus, Type 1 - psychology; Diabetes. Impaired glucose tolerance; Electroencephalography; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; Female; Humans; Hypoglycaemia unawareness; Hypoglycemia - physiopathology; Insulin - blood; Insulin-dependent diabetes mellitus; Male; Management. Various non-drug treatments. Langerhans islet grafts; Medical sciences; Perception; Psychomotor Performance - physiology; Symptoms; Vigilance; Wechsler Scales
• ISSN: 0306-4530; 1873-3360
• DOI: 10.1016/0306-4530(95)00034-8

To elucidate neurophysiological characteristics in hypoglycaemia unawareness, we investigated the relationship between electroencephalography (EEG) parameters of vigilance and awareness of various symptom categories early in response to hypoglycaemia in intensively treated diabetic patients with different degrees of hypoglycaemia unawareness. Hypoglycaemia (venous plasma glucose below 2.2 mmol/1) was induced with an intravenous insulin bolus in seven patients with insulin-dependent diabetes mellitus (IDDM) with a history of hypoglycaemia unawareness and repeated severe hypoglycaemia, as well as in a group of seven IDDM patients with good awareness of hypoglycaemia. Both groups were comparable in age, treatment strategy, glycaemic control and level of late complications. Basic cognitive performance and other symptom categories were estimated serially during a period of 2 h following the insulin bolus. A vigilance-controlled EEG was recorded continuously; its automatic analysis included the evaluation of vigilance indices. In the baseline prehypoglycaemic state, hypoglycaemia unaware patients showed higher initial vigilance ( p = .05) than the aware group. Unaware patients reported fewer neurogenic ( p = .002, mainly cholinergic, p = .009) hypoglycaemia symptoms during hypoglycaemia, and developed an impairment in cognitive performance over time ( p = .002). EEG analysis indicated a more rapid decrease in vigilance after the hypoglycaemic stimulus for unaware patients than for aware patients. The lowering of plasma glucose to 3.06–3.89 mmol/1 already induced a significant increase in delta and theta, as well as a decrease in alpha relative power only in the unaware group. Differences between groups with regards to the degree of deceleration were most pronounced early, during only slight hypoglycaemia, and topographically spread over central and parietal brain regions. Further lowering of plasma glucose induced an even more pronounced, abrupt increase in slow waves in unaware patients at higher plasma glucose levels than in hypoglycaemia aware subjects (for delta waves at 2.41 ± 0.16 vs. 1.96±0.1 mmol/1, p=.04). This preceded the worsening of cognitive performance during hypoglycaemia in unaware patients by 19 ± 3 min. Hypoglycaemia unawareness associated with previous unconsciousness is associated with—and may be the result of—an early hypoglycaemiainduced reduction in vigilance and an early EEG deceleration, which seems to be a teleologically effective meas