Hypernatremia or hypernatraemia that is defined by an elevated sodium level in the blood.
Hypernatremia is generally not caused by an excess of sodium, but rather by a relative
deficit of free water in the body.
For this reason, hypernatremia is often synonymous with the less precise term, dehydration.
Water is lost from the body in a variety of ways, including perspiration, imperceptible
losses from breathing, and in the feces and urine.
If the amount of water ingested consistently falls below the amount of water lost, the
plasma sodium level will begin to rise, leading to hypernatremia.
Rarely, hypernatremia can result from massive salt ingestion, such as may occur from drinking
seawater or excessive amounts of a salty liquid like soy sauce.
Ordinarily, even a small rise in the plasma sodium concentration above the normal range
results in a strong sensation of thirst, an increase in free water intake, and correction
of the abnormality.
Therefore, hypernatremia most often occurs in people such as infants, those with impaired
mental status, or the elderly, who may have an intact thirst mechanism but are unable
to ask for or obtain water.
Signs and symptoms Clinical manifestations of hypernatremia can
be subtle, consisting of lethargy, weakness, irritability, neuromuscular excitability,
and edema.
With more severe elevations of the sodium level, seizures and coma may occur.
Severe symptoms are usually due to acute elevation of the plasma sodium concentration to above
157 mEq/L Values above 180 mEq/L are associated with a high mortality rate, particularly in
adults.
However such high levels of sodium rarely occur without severe coexisting medical conditions.
Cause
Common causes of hypernatremia include: Hypovolemic
Inadequate intake of free water associated with total body sodium depletion.
Typically in elderly or otherwise disabled patients who are unable to take in water as
their thirst dictates and also are sodium depleted.
This is the most common cause of hypernatremia.
Excessive losses of water from the urinary tract, which may be caused by glycosuria,
or other osmotic diuretics - leads to a combination of sodium and free water losses.
Water losses associated with extreme sweating.
Severe watery diarrhea
Euvolemic Excessive excretion of water from the kidneys
caused by diabetes insipidus, which involves either inadequate production of the hormone
vasopressin, from the pituitary gland or impaired responsiveness of the kidneys to vasopressin.
Hypervolemic Intake of a hypertonic fluid with restricted
free water intake.
This is relatively uncommon, though it can occur after a vigorous resuscitation where
a patient receives a large volume of a concentrated sodium bicarbonate solution.
Ingesting seawater also causes hypernatremia because seawater is hypertonic and free water
is not available.
There are several recorded cases of forced ingestion of concentrated salt solution in
exorcism rituals leading to death.
Mineralcorticoid excess due to a disease state such as Conn's syndrome usually does not lead
to hypernatremia unless free water intake is restricted.
Salt poisoning.
Treatment The cornerstone of treatment is administration
of free water to correct the relative water deficit.
Water can be replaced orally or intravenously.
Water alone cannot be administered intravenously, but rather can be given with addition to dextrose
or saline infusion solutions.
However, overly rapid correction of hypernatremia is potentially very dangerous.
The body adapts to the higher sodium concentration.
Rapidly lowering the sodium concentration with free water, once this adaptation has
occurred, causes water to flow into brain cells and causes them to swell.
This can lead to cerebral edema, potentially resulting in seizures, permanent brain damage,
or death.
Therefore, significant hypernatremia should be treated carefully by a physician or other
medical professional with experience in treatment of electrolyte imbalance, specific treatment
like ACE inhibitors in heart failure and corticosteroids in nephropathy also can be used.
References
External links Sodium at Lab Tests Online