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By Dr Y.L.M
Q. MY husband has high blood pressure. He is on an antihypertensive drug. For the past six months he has been feeling fatigued and he has had headaches. When the doctor did a blood test, it was found that some of his electrolytes were low. What are electrolytes and what do they do?
A. Electrolytes are salts like sodium, potassium, calcium, magnesium, bicarbonate and chloride that conduct electricity. They are present in our bodies and are found in our blood, tissues and other fluids.
Sodium (Na+) is the major positive ion in fluid outside our cells (called extracellular fluid). You get sodium from the foods that you eat, especially salty foods like French fries. Sodium is very important for determining the amount of water in your body as it regulates the movement of water in and out of your cells. Many body functions, especially in your brain, nerves and muscles, require electrical signals transmitted by sodium for communication.
Potassium (K+) is the main positive ion in the fluid inside our cells (called intracellular fluid). Potassium is essential for normal cell function, such as your muscle movement and tone as well as the regulation of your heartbeat.
Chloride (Cl-) is the main negative ion in extracellular fluid. The concentration of chloride in your body is almost the same as seawater. Chloride, together with sodium, maintains the normal fluid balance in your body.
Bicarbonate (HCO3-) is necessary to maintain the normal pH level (or acidity) of your body fluids. Carbon dioxide dissolves into the blood stream to be carried as bicarbonate.
Your kidneys regulate fluid and electrolyte absorption and excretion. Excess electrolytes are excreted through your urine or faeces.
Q. Then what causes there to be more or less electrolytes in our body? Will eating too much of a certain kind of food cause this?
It depends on the type of electrolyte imbalance you have. Too much sodium in your blood is called hypernatremia. Its causes are excessive fluid loss from your body (dehydration), such as from diarrhoea, vomiting, taking too many diuretic medications, diabetes insipidus, heavy exercise or exertion, too much sweating and severe burns.
It can also be caused by too much salt in your diet. It causes fatigue, weakness, irritability, muscle twitching and headache. If not treated, it can lead to fits, delirium, coma and death.
Too little sodium in your blood is called hyponatremia. It is caused by too much water being retained and kidney failure. If you are dehydrated and you drink too much water too quickly, it can lead to hyponatremia.
People who also lose too much salt when they have diarrhoea or vomiting or if they are taking thiazide diuretics can also have this condition.
It is interesting to note that hyponatremia shares a lot of the same causes as hypernatremia - it all depends on which you are losing in proportion to the other: water or salt. Other causes include liver cirrhosis, heart disease, hypothyroidism and nephrotic syndrome.
The symptoms are, as with hypernatremia, fatigue, weakness and headache progressing to fits, coma and death.
Q. What about potassium? My husband's doctor asked him to take more bananas to restore his depleted potassium.
A depletion of potassium in your blood is called hypokalemia. Its most common cause is potassium depletion through usage of diuretics which makes you urinate more. Once again, the usual channels of diarrhoea, excessive vomiting and sweating can also deplete your potassium levels.
If you don't take enough foods containing potassium, such as bananas and certain fruits, you also might not have enough to replenish your potassium should you be on certain medications.
The symptoms of hypokalemia can include abnormal rhythms of the heart (arrhythmia), muscle pain, irritability, and weakness which can progress to paralysis.
Too much potassium in your blood is called hyperkalemia. It can be caused by burns, having chemotherapy if you have cancer (causing too much tumour cells to break up and release potassium), too much red blood cell destruction through any means, too much skeletal muscle destruction, and rarely, strenuous exercise.
A very common cause is also kidney failure. Medications which impair potassium excretion (such as potassium-sparing diuretics) can also lead to hyperkalemia.
Hyperkalemia's most serious consequences have all got to do with the heart. It can cause irregular conduction patterns in your heart, which can lead to ventricular fibrillation (where your heart chambers are beating abnormally and ineffectively), which can lead to a cardiac arrest and death.
In addition, it can also cause tingling in your hands and feet, weakness and numbness.
How do you treat electrolyte imbalance? Is it by taking salt water and bananas for low sodium and potassium respectively?
Hyponatremia must be corrected slowly because a sudden change can cause your brain cells to shrink. Treatment is usually through fluid restriction, IV 3% saline infusion and salt tablets. Your doctor might also ask you to increase salt in your diet.
Hypernatremia is treated by slowly replenishing water loss through drinking or infusion.
Hypokalemia can be treated slowly via potassium supplements (Slow K). You are also encouraged to eat foods rich in potassium like bananas, oranges and spinach. Hyperkalemia is treated via diuretics to flush out the excess potassium and insulin to force the excess potassium into cells.
Dr YLM graduated as a medical doctor, and has been writing for many years on various subjects such as medicine, health advice, computers and entertainment.
The information contained in this column is for general educational purposes only. Neither The Star nor the author nor AsiaOne gives any warranty on accuracy, completeness, functionality, usefulness or other assurances as to such information.
The Star, the author and AsiaOne disclaim all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.
This story was first published in The Star on Sept 28, 2008.
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