Laboratory Studies
Studies indicated in patients with suspected hypernatremia are listed below.
Serum tests
Obtain levels of sodium, osmolality, BUN, and creatinine.
Other laboratory measurements include aldosterone, cortisol, antidiuretic hormone (ADH), and corticotropin (ACTH) levels
Urine sodium concentration and osmolality
In cases of hypovolemic hypernatremia, extrarenal losses show urine sodium levels of less than 20 mEq/L, and in cases of renal losses, urine sodium values are more than 20 mEq/L.
In euvolemic hypernatremia, urine sodium data vary.
In hypervolemic hypernatremia, the urine sodium level is more than 20 mEq/L.
Imaging Studies
Imaging studies of the head should be considered in alert patients with severe hypernatremia to rule out a hypothalamic lesion affecting the thirst center.
CT scans may help in diagnosing intracranial tumors, granulomatous diseases (eg, sarcoid, tuberculosis, histiocytosis), and other intracranial pathologies.
MRI further delineates the pathology.
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Pediatric Hypernatremia. Figure A: Normal cell. Figure B: Cell initially responds to extracellular hypertonicity through passive osmosis of water extracellularly, resulting in cell shrinkage. Figure C: Cell actively responds to extracellular hypertonicity and cell shrinkage in order to limit water loss through transport of organic osmolytes across the cell membrane, as well as through intracellular production of these osmolytes. Figure D: Rapid correction of extracellular hypertonicity results in passive movement of water molecules into the relatively hypertonic intracellular space, causing cellular swelling, damage, and ultimately death.
