Hypernatremia: diagnosis and treatment of intensive care

2021-07-31 09:40 PM

Although hypernatremia is most often caused by dehydration, it can also be caused by eating salt, without water, or using hypertonic sodium solutions

The term “effective osmosis” refers to the action of solutes across the cell membrane that are not readily available (effective osmosis) and thus determines the water distribution of the cell. Because sodium and its anions account for most of the effective osmolarity in the extracellular fluid, high plasma sodium concentrations (hypernatremia) indicate hyperosmolarity and hypovolemia. In most cases, hypernatremia is caused by dehydration. This develops when dehydration is not replaced because of the lack of water, when the desire to drink is reduced, or because the patient is unable to find water on their own. Severe irreplaceable dehydration (eg, due to diabetes insipidus) leads to the rapid onset of hypernatremia. However, even with severe dehydration, hypernatremia will not develop if thirst and water are readily available.

Although hypernatremia is most often caused by dehydration, it can also be caused by eating salt without water or using hypertonic sodium solutions.

Hypernatremia due to lack of water is called dehydration. This is different from hypokalemia, in which both salt and water are lost.

Hypernatremia is usually caused by an imbalance between the amount of water taken in and the amount of water excreted from the body.

Hypernatremia is accompanied by increased osmotic pressure.

Symptoms in the elderly are often subtle.

Definite diagnosis


Blood sodium > 145 mmo/l.

Suggestive clinical signs

Body as a whole: thirst, malaise fever.

Neurological: muscle weakness, confusion, delirium, convulsions, coma, spasticity, hyperreflexia.

Gastrointestinal: nausea and vomiting.

Signs of changes in extracellular fluid volume.

+ Hypernatremia due to volume depletion (weight loss, dry mucosal skin, collapsed jugular vein, decreased central venous pressure, tachycardia, ...).

+ Hypernatremia due to increased volume (weight gain, no signs of extracellular fluid deficiency, peripheral edema, distended neck veins, increased central venous pressure).

Common causes

Hypovolemic hypernatremia (water deficit > sodium deficit)

Decreased water intake: lack of water intake or impaired thirst mechanism (central nervous system damage).

Renal water loss:

+ Diuretics (loop diuretics, thiazides, potassium-sparing diuretics, infiltrative diuretics).

+ Hyperglycemia in coma increases osmotic pressure.

After urinary tract obstruction.

+ Frequent urination during the recovery period of acute renal failure.

+ Central diabetes insipidus and nephrogenic diabetes insipidus.

Extrarenal water loss:

+ Gastrointestinal loss: vomiting, gastric drainage, diarrhea, bile drainage, fluid loss through the fistula.

+ Loss through the skin: due to sweat, burns, minor wounds.

Volumetric hypernatremia (salt intake > water intake)

Hypertonic salt infusion.

Infusion of sodium bicarbonate.

Drink the wrong salt.

Excess water-salt-metabolizing corticosteroids (Cushing's syndrome, Conn's syndrome).

Hypernatremia with normal blood volume

Extrarenal loss.


Formula to calculate the amount of water deficiency of the body (used when there is hypernatremia with hypovolemia)

Lack of water = Body water x (Na blood/140-1)

In there:

+ Body water = Bodyweight x 0.6 (male).

+ Body water = Bodyweight x 0, (male).

Sodium Adjustment Formula

N= (Na of infusion - Na of blood)/(Body water+1)

In there:

N is the number of mmol of sodium in the blood that changes in 1 liter of fluid.


Treatment of hypovolemic hypernatremia: 0.9% saline solution should be selected to restore water deficit.

Treatment of isotonic hypernatremia: 0.45% sodium chloride is recommended. If the glomerular filtration rate is reduced, diuretics can be used to increase urinary sodium excretion.

Hypervolemic hypernatremia: 5% glucose should be used to reduce blood osmolality. Loop diuretics can increase renal sodium excretion.

In cases of severe hypernatremia and severe renal failure, intermittent dialysis should be indicated to correct serum sodium.

Sodium-compensated central diabetes insipidus combined with desmopressin acetate (Minirin).

Monitor electrolytes every 6 hours, blood osmolality and urine once a day until sodium is normal.

Rate of correction for hyponatremia < 0.5mmol/l per hour and not more than 12mmol/l in 24 hours.

Estimated osmolality = 2 sodium + glucose.

Control blood sugar if blood sugar is high.

Closely monitor the patient's fluid in and out.

Sodium concentrations in some fluids.

+ 0.45% sodium chloride has a sodium concentration of 77mmol/l.

+ 0.9% sodium chloride has a sodium concentration of 154mmol/l.

Heart and treat the cause


Elderly people are prone to hypernatremia due to loss of thirst. It is necessary to advise family members and patients to be wary of cases of thirst, heat, heat, dehydration.