lhypernatrémie

Hypernatrémie, or l'hypernatrémie in French, is a condition in which the serum sodium concentration exceeds 145 mEq/L. It results from a net water deficit relative to sodium and can occur with water loss, excess sodium administration, or both. Clinically, patients may experience thirst, dry mucous membranes, tachycardia, hypotension, and neurologic symptoms ranging from confusion to seizures or coma if correction is delayed.

Pathophysiology and classification focus on volume status and the underlying cause. Hypernatremia is typically categorized as hypovolemic (reduced extracellular volume with water loss), euvolemic, or hypervolemic (excess total body sodium with water loss or retention). Causes include insensible water loss (fever, excessive sweating), diabetes insipidus (central or nephrogenic), osmotic diuresis from hyperglycemia, diarrhea or vomiting with poor water intake, and, less commonly, administration of hypertonic saline.

Diagnosis involves confirming hypernatremia with serum chemistry and assessing volume status. Urine osmolality and urine sodium help distinguish renal from extrarenal losses; plasma osmolality and glucose support the assessment. Evaluation also focuses on identifying disorders such as diabetes insipidus and determining the patient’s fluid intake and losses.

Treatment aims to restore normal water balance while stabilizing circulation. In hypovolemic hypernatremia, initial resuscitation with isotonic saline is followed by free-water replacement with hypotonic fluids (for example, 0.45% saline or 5% dextrose in water). In euvolemic or hypervolemic hypernatremia, treat the underlying cause and provide appropriate free-water replacement. Correct the sodium gradually, typically at about 0.5 mEq/L per hour and not more than 10–12 mEq/L per 24 hours, to minimize the risk of cerebral edema. In diabetes insipidus, specific therapies such as desmopressin for central DI may be indicated. Prognosis depends on the rapidity of onset, the underlying cause, and the timeliness of treatment.