Question of the Week
For July 8, 2014
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A decrease in the serum sodium level and an increase in the serum potassium levelAn increase in the serum sodium and potassium levelsAn increase in the serum sodium level and a decrease in the serum potassium levelNo change in the serum sodium level and an increase in the serum potassium levelA decrease in the serum sodium and potassium levels
Key Learning Point View Case Presentation
After initiation of a continuous intravenous insulin infusion in a patient who is in a hyperosmolar hyperglycemic state, the serum sodium level is expected to increase.
Hyperglycemia increases serum osmolality, causing water to move out of cells, which typically results in hyponatremia. In some cases, however, free-water loss from osmotic diuresis, insensible losses, and other losses (e.g., profuse watery diarrhea) can result in a significant free-water deficit. As blood glucose corrects with the administration of a continuous intravenous insulin infusion, the serum osmolality rapidly drops, and the water that moved out of the cells in response to hyperosmolality now reenters the cells, thereby increasing the serum sodium level. Thus, the serum sodium level is expected to rise with the correction of the serum glucose. If the serum sodium is elevated at presentation, the subsequent rise can be very substantial and should be anticipated so that severe hypernatremia can be mitigated.
Urinary and gastrointestinal losses generally result in a substantial potassium deficit in patients who have a hyperosmolar hyperglycemic state. Insulin deficiency and hyperosmolality results in a shift of potassium out of cells and into the circulation in patients with hyperosmolar hyperglycemia. After insulin is administered, the potassium levels usually drop substantially as insulin drives the potassium into the cells.
Last reviewed Aug 2017. Last modified May 2016.
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Ishikawa S et al. Opposite changes in serum sodium and potassium in patients in diabetic coma. Endocr J 1994 Feb 1; 41:37. > View Abstract