PCL Group :D: Importance of Sodium, Hyponatremia, Hypernatremia

Sodium

most of the sodium is located in the ECF (Extra-cellular Fluid) which is 55% of body's sodium
40% is located in the bone, 2%-5% in organs and cells
normal level of sodiums in the blood are 136 to 145 milliequivalents per liter (mEq/L) of blood
Sodium is required by all cells in the body to maintain a normal fluid balance
Sodium also plays a key role in normal nerve and muscle function
Sodium Input: Food and Drink
Sodium Output: Sweat and Urine (primarily)
When sodium intake and loss are not in balance, the total amount of sodium in the body is affected.
Changes in the total amount of sodium are closely linked to changes in the volume of water in the blood.
When sodium in the blood decrease, blood volume will decrease in order to maintain the osmolarity of the blood. Thus when blood volume decreases, blood pressure also decreases, heart rate increases, and light-headedness and sometimes shock occur.
The blood volume increases when there is too much sodium in the body,
When excess sodium accumulates in the body, extra fluid accumulates in the space surrounding the cells. As a result, the tissues, especially in the feet and ankles, swell (a condition called edema).
Thus sodium is important in maintaining an effective circulation volume in the body.

Hyponatremia

Sodium in blood is below 135 mEq/L.
Occurs when sodium is overdiluted in the body
Sodium can be overdiluted when people drink enormous amounts of water ( happens in patient with psychiatric disorder) or hospitalized patient who receive large amount of fluid intravenously.
Thus amount of fluid taken in exceeds the kidney's capacity to eliminate the excess fluid.
Intake of smaller amounts of water—sometimes as little as 1 quart a day—can also lead to hyponatremia in people whose kidneys are not functioning normally, such as people with kidney failure.
Patient with SIDAH (Syndrome of inappropriate excretion of Anti-Diuretic Hormone) where excessive ADH is produced. Thus large amount water is conserved in the body and overdilute the sodium in the blood
Hyponatremia also happen in patient with heart failure.
The diagnosis of hyponatremia is made by measuring the sodium level in the blood.

Symptoms

When the sodium level in the blood falls quickly, symptoms tend to develop rapidly and be more severe
lethargy and confusion (The brain is particularly sensitive to changes in the sodium level in the blood.)
Severe hyponatremia may cause osmotic shift of water from the plasma into the brain cells (water intoxication). Brain cell expands and ceases to function
muscle twitching and seizures ( as hyponatremia become more severe)
coma, and death may follow

Hypernatremia

sodium in blood is above 158 mEq/L.
The body contains too little water relative to the amount of sodium. The sodium level in the blood becomes abnormally high when water loss exceeds sodium loss, as occurs with dehydration
In most people, hypernatremia results from dehydration
Hypernatremia occurs in people who drink too little water and in those who have diarrhea, vomiting, fever, excessive sweating (particularly during hot weather), or abnormal kidney function
hypernatremia may occur in diabetes insipidus, in which the kidneys excrete too much water
Hypernatremia is most common among older people, who tend to sense thirst more gradually and less intensely than younger people do
In addition, the kidneys' ability to concentrate urine declines in advanced age, so older people are less able to conserve water.
Diuretic can also cause patient to secrete water excessively.

Symptoms

Sources: http://www.merck.com/mmhe/sec12/ch155/ch155k.html

Contributed by Lawrence Oh

PCL Group :D