Dynamics of blood electrolytes in repeated hyper- and/or hypoglycaemic events in patients with type 1 diabetes.

AIMS/HYPOTHESIS: Electrolyte disturbances are well-known consequences of the diabetic pathology. However, less is known about the cumulative effects of repeated changes in glycaemia, a characteristic of diabetes, on the electrolyte balance. We therefore investigated the ionic profiles of patients with type 1 diabetes during consecutive hyper- and/or hypoglycaemic events using the glucose clamp.
METHODS: In protocol 1, two successive hyperglycaemic excursions to 18 mmol/l were induced; in protocol 2, a hypoglycaemic excursion (2.5 mmol/l) was followed by a hyperglycaemic excursion (12 mmol/l) and another hypoglycaemic episode (3.0 mmol/l).
RESULTS: Blood osmolarity increased during hyperglycaemia and was unaffected by hypoglycaemia. Hyperglycaemia induced decreases in plasma Na(+) Cl(-) and Ca(2+) concentrations and increases in K(+) concentrations. These changes were faithfully reproduced during a second hyperglycaemia. Hypoglycaemia provoked rapid and rapidly reversible increases in Na(+), Cl(-) and Ca(2+). In sharp contrast, K(+) levels displayed a rapid and substantial fall from which they did not fully recover even 2 h after the re-establishment of euglycaemia. A second hypoglycaemia caused an additional fall. CONCLUSIONS/
INTERPRETATION: Repeated hyperglycaemia events do not lead to any cumulative effects on blood electrolytes. However, repeated hypoglycaemias are cumulative with respect to K(+) levels due to a very slow recovery following hypoglycaemia. These results suggest that recurring hypoglycaemic events may lead to progressively lower K(+) levels despite rapid re-establishment of euglycaemia. This warrants close monitoring of plasma K(+) levels combined with continuous glucose monitoring particularly in patients under intensive insulin therapy who are subject to repeated hypoglycaemic episodes. TRIAL REGISTRATION: Clinicaltrial.gov NCT01060917.