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Figure 2. Algorithm of hypernatremia’s management [48,51-60] . The treatment of hypernatremia in cancer patients is based on the correction
of the cause. For the differential diagnosis, the evaluation of volume and urinary sodium are fundamental. DI: diabetes insipidus; EVC:
extracellular volume

Extra-renal water loss is often related to gastrointestinal diseases (vomiting, nasogastric drainage, and
diarrhea).

Rarely, hypernatremia can be caused by excessive salt intake. This condition is often iatrogenic and induced
by parenteral administering of hypertonic solutions or chronic nutrition support with hyperosmolar or
[55]
high protein feeds .
Management
Hypernatremia causes neurological symptoms, for which severity is correlated with both grade and onset
speed. In most cases, patients refer non-specific symptoms such as thirst, anorexia, restlessness, nausea,
muscle weakness, and confusion. In the case of rapid onset or severe hypernatremia, patients might present
[56]
lethargy, hyperreflexia, until convulsions, and coma .
Clinical suspicion of hypernatremia should be confirmed by laboratory exam. The correct diagnosis and
the detection of specific causes or predisposing factors are crucial for a correct management [Figure 2].

For a correct differential diagnosis between hyponatremia caused by excess of sodium intake and
hyponatremia caused by loss of free water, the assessment of urine osmolality, urine sodium concentration,
[57]
and urine volume should be obtained . Concentrated urine is usually related to insufficient water intake
or extra-renal losses.

Conversely, hypernatremia is associated to elevated serum osmolality and low urine osmolality renal
[56]
damage with deficient capacity of urinary concentration .
Hypernatremia associated to polyuria (e.g., 24 h urine volume exceeding 2.5 L), low urine osmolality, and
urinary sodium are criteria for central insipidus diabetes diagnosis .
[58]
Once hypernatremia diagnosis is confirmed, the optimal management requires the removal of the cause
and the correction of the electrolyte disorder based on the total ECV, restoring intravascular volume and
free water.