Know your test : Electrolytes

Nonibala Ningthoujam *

Electrolytes are electrically charged minerals that are found in body tissues and blood in the form of dissolved salts. They help move nutrients into and wastes out of the body’s cells, maintain a healthy water balance, and help stabilise the body’s pH level.

Common electrolytes that are measured by doctors with blood testing include sodium (Na+), potassium (K+) and chloride (Cl-). Sometimes, bicarbonate (HCO3-; sometimes reported as total CO2) is also included as part of a basic electrolyte panel.

A person’s diet provides sodium, potassium, and chloride; the kidneys excrete them. The lungs provide oxygen and regulate CO2 which is in balance with bicarbonate. The balance of these chemicals is an indication of the functional well-being of several basic body functions, including those performed by the kidneys and heart.

SODIUM

Sodium is the major positive ion in fluid outside of cells. When combined with chloride, the resulting substance is the common salt. Excess sodium (such as that obtained from dietary sources) is excreted in the urine. Sodium regulates the total amount of water in the body and the transmission of sodium into and out of individual cells and also plays a role in other critical body functions. Many processes in the body, especially in the brain, nervous system, and muscles, require electrical signals for communication.

The movement of sodium is critical in generation of these electrical signals. Therefore, too much or too little sodium can cause cells to malfunction, and extremes in the blood sodium levels (too much or too little) can be fatal.

o Increased sodium (hypernatremia): This happens when there is excess sodium in relation to water. There are numerous causes of hypernatremia; these include kidney disease, too little water intake, and loss of water due to diarrhoea and/or vomiting.

o A decreased concentration of sodium (hyponatremia): This occurs when there is a relative increase in the amount of body water relative to sodium. This happens with some diseases of the liver and kidney, in patients with congestive heart failure, in burn victims, and in numerous other conditions.

POTASSIUM

Potassium is the major positive ion found inside of cells. The proper level of potassium is essential for normal cell function. Among the many functions of potassium in the body are regulation of the heartbeat and the function of the muscles. A seriously abnormal increase in potassium (hyperkalemia) or decrease in potassium (hypokalemia) can profoundly affect the nervous system and increases the chance of irregular heartbeats (arrhythmias), which, when extreme, can be fatal.

o Increased potassium (hyperkalemia): Potassium is normally excreted by the kidneys, so disorders that decrease the function of the kidneys can result in hyperkalemia. Certain medications may also predispose an individual to hyperkalemia.

o Decreased potassium (hypokalemia): This can arise due to kidney diseases; excessive loss due to heavy sweating, vomiting, or diarrhoea, eating disorders, certain medications, or other causes.

CHLORIDE

Chloride is the major negative ion found in the fluid outside of cells and in the blood. Sea water has almost the same concentration of chloride ion as human body fluids. Chloride also plays a role in helping the body maintain a normal balance of fluids. The balance of chloride ion is closely regulated by the body. Significant increases or decreases in chloride can have serious or even fatal consequences.

o Increase chloride (hyperchloremia): Elevations in chloride may be seen in diarrhoea, certain kidney diseases, and sometimes in overactivity of the parathyroid glands.

o Decreased chloride (hypochloremia): Chloride is normally lost in the urine, sweat, and stomach secretions. Excessive loss can occur from heavy sweating, vomiting, and adrenal gland and kidney disease.

BICARBONATE

The bicarbonate ion acts as a buffer to maintain the normal levels of acidity (pH) in blood and other fluids in the body. Bicarbonate levels are measured to monitor the acidity of the blood and body fluids. The acidity is affected by foods or medications that we ingest and the function of the kidneys and lungs.

The bicarbonate test is usually performed along with tests for other blood electrolytes. Disruptions in the normal bicarbonate level may be due to diseases that interfere with respiratory function, kidney diseases, metabolic conditions, or other causes.

HOW IS THE TEST USED?

The electrolyte panel is usually done as part of a routine test, either by itself or as components of a basic metabolic panel or comprehensive metabolic panel. It is used to identify an electrolyte or acid-base imbalance and to monitor the effect of treatment on a known imbalance that is affecting the bodily organ function. Since electrolyte and acid-base imbalances can be present with a wide variety of acute and chronic illnesses, the electrolyte panel is frequently done for hospitalised patients and those who come to the emergency room.

If a patient has a single electrolyte that is high or low, such as sodium or potassium, the doctor may ask for repeat testing of that individual electrolyte, monitoring the imbalance until it resolves. If a patient has an acid-base imbalance, the doctor may ask for blood gas tests, which measure the pH and oxygen and carbon dioxide in an arterial blood sample, to help evaluate the severity of the imbalance and monitor its response to treatment.

HOW IS THE SAMPLE COLLECTED?

A blood sample is drawn by needle from a vein in the arm.

IS THERE ANY PREPARATION REQUIRED?

No special preparation is required.