Hypernatremia is defined as a plasma sodium concentration more than

Hypernatremia is defined as a plasma Na+ concentration >145 mmol/L. Hypernatremia can develop following the loss of water both renal and nonrenal routes. Insensible losses of water may increase in the setting of fever, exercise, heat exposure, severe burns, or mechanical ventilation. Diarrhea is, in turn, the most common gastrointestinal cause of hypernatremia. Notably, osmotic diarrhea and viral gastroenteritides typically generate stools with Na+ and K+ <100 mM, thus leading to water loss and hypernatremia; in contrast, secretory diarrhea typically results in isotonic stool and thus hypovolemia with or without hypovolemic hyponatremia. Common causes of renal water loss include osmotic diuresis secondary to hyperglycemia, excess urea, postobstructive diuresis, or mannitol;Hypernatremia due to a water diuresis occurs in central or nephrogenic diabetes insipidus (DI). Ref: Harrison 19e pg: 302