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Risks
of Sodium Imbalance
Hypernatremia and Hyponatremia: Causes and Risks of Sodium Imbalance
By Cari Nierenberg
Hyponatremia and hypernatremia are primarily disorders of water
metabolism, said Dr. David Mount, a kidney specialist and clinical chief of the
renal division at Brigham and Women's Hospital in Boston.
In hyponatremia, an excess of water in the body can lead to a
low concentration of sodium in the blood, he said.
And in hypernatremia, a deficit of water in the body can lead to
a high concentration of sodium in the blood.
Hyponatremia
Hyponatremia is a low concentration of sodium in the blood
because of an excessive retention of water, Mount said.
In this electrolyte abnormality, there is too much water in the body and this dilutes sodium
levels in the bloodstream, he noted.
Hyponatremia occurs when blood sodium goes below normal levels,
which is 135 milliequivalents/liter (mEq/L).
When sodium levels in the blood are too low, extra water goes
into body cells causing them to swell.
This swelling can be especially dangerous for brain cells, resulting in neurological symptoms
such as headache, confusion, irritability, seizures or even coma.
The symptoms of hyponatremia may be more serious when blood
sodium levels drop very quickly and may be milder when they dip gradually, as
that allows the body more time to adjust to the change.
Other symptoms of the disorder include muscle cramps or
weakness, nausea, vomiting, tiredness and a lack of energy.
Hyponatremia can result from an illness or from taking certain
medications.
According to the National Kidney Foundation, some of the causes may
include:
· Severe vomiting or diarrhea.
· Excessive fluid intake, such as during endurance
activities or from excessive thirst.
· Taking diuretics, medications that help flush excess water and
sodium from the body.
· Kidney failure, a condition in which the kidneys have difficulty
eliminating extra fluid from the body.
· Congestive heart failure, which can lead to a build-up of excess
fluid in the body.
· Burns affecting a large area of the body.
· Small cell lung cancer.
· Taking antidepressants, including some commonly used selective
serotonin reuptake inhibitors, particularly in older adults.
· Syndrome of inappropriate antidiuretic hormone secretion,
a condition in which the body makes too much antidiuretic hormone, causing the
body to retain too much water and diluting levels of sodium.
People can also consume excessive amounts of water during exercise
and develop hyponatremia, Mount told Live Science.
Exercise-associated hyponatremia is more likely to affect endurance athletes, such as
marathoners, triathletes and ultra-distance race competitors.
Hyponatremia is not a permanent condition, although certain
people may be more prone to the disorder than others because of lifestyle
habits or a medical condition.
Treatment for hyponatremia depends on its cause and seriousness.
In moderate cases of hyponatremia that are the result of diet,
taking diuretics or drinking too much water, a person may need to restrict
water intake, consume salty foods — such as bouillon or pretzels
— or adjust diuretic intake to raise blood sodium levels.
A person with severe hyponatremia may be given a very
concentrated saline solution intravenously.
But sodium levels need to be corrected slowly and in a
controlled fashion, to prevent swollen brain tissue, Mount said.
Hypernatremia
In hypernatremia, the body contains too little water relative to
the amount of sodium, Mount said.
This causes sodium levels to become abnormally high in the blood — more than 145 mEq/L
— which causes water to move out of body tissues and into the blood in an
attempt to equalize the concentration between the two.
Water can be lost from brain cells, causing them to shrink,
which can be dangerous.
Too much sodium in the blood is a common problem
in older adults, especially those who have been hospitalized or are in
long-term care facilities, Mount said.
The disorder can also affect much younger people: Infants may
experience hypernatremia if they have severe diarrhea, for example.
Besides thirst, many of the symptoms of hypernatremia, such as
irritability, restlessness and muscle twitching, affect the central nervous
system and stem from a loss of water content from brain cells.
In some cases, hypernatremia can be life-threatening.
Similar to hyponatremia, other symptoms of hypernatremia include
feeling tired or lacking energy, confusion, seizures or coma.
The main cause of hypernatremia usually involves dehydration due
to an impaired thirst mechanism or limited access to water, according to
the Merck Manual.
The disorder can also result from diarrhea or vomiting, taking
diuretics or having a high fever.
People who aren't always able to provide water for themselves
may be more at risk for hypernatremia.
This includes people on tube feedings and those with altered
mental status (stroke or dementia), plus people who are very young or very old
and frail, according to a review in the New England Journal of Medicine.
Older people are more prone to hypernatremia because their thirst
mechanism, kidney function, and hormones regulating salt and water balance may
not work as effectively.
The main treatment for hypernatremia is simply to replenish
fluids. A person with a mild case of hypernatremia can usually just drink fluids
to recover.
But in more severe instances, water and a small amount of sodium
are given intravenously in controlled amounts over a 48-hour period to slowly
reduce sodium levels to a normal range.
Fluid levels are corrected slowly to avoid the risk of cerebral
edema, a dangerous condition in which there is swelling of the brain, Mount said.
Hypernatremia can be fatal, and may cause permanent brain damage
if not treated properly. Some studies suggest the mortality rate may be more
than 50% in hospitalized patients affected by the disorder.
Cari
Nierenberg, Live Science Contributor
Live
Science is part of Future US Inc, an international media group and leading
digital publisher.
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