Electrolytes: Sodium, Potassium, Chloride

 Electrolytes 

Serum sodium 

• A major cation of extracellular fluid. 
• Maintains osmotic pressure and acid-base balance, and assist in the transmission of nerve impulse. 
• Is absorbed from the small intestine and excreted in the urine in amounts dependent on dietary intake. 
• Minimum daily requirements of sodium is approximately 15 mEq

Nursing consideration: Drawing blood samples soon after an intravenous (IV) infusion of sodium chloride will increase the level, producing an inaccurate result. 

Serum potassium 

• A major intracellular cation; it regulates cellular water balance, electrical conduction in muscle cells, and acid-base balance. 
• The body obtains potassium through dietary ingestion and the kidneys preserve or excrete potassium, depending on cellular needs. 
• Potassium levels are used to evaluate cardiac function, gastrointestinal function and the need for IV replacement therapy.

Nursing considerations

• Prolonged use of tourniquet and clenching and unclenching the hand before venous sampling can increase the level, producing an inaccurate result. 
• Do not draw the blood from a site where an IV infusion exists. 
• If the client is receiving a potassium supplement, note this on the laboratory forum. 
• Client with elevated white blood cell counts and platelet count may have falsely elevated potassium levels. 

Serum chloride 

• A hydrochloric acid salt is the most abundant body anion in the extracellular fluid. 
• Functions to counterbalance cations, such as sodium, and acts as a buffer during oxygen and carbon dioxide exchange in red blood cells. 
• Acid indigestion and maintaining osmotic pressure and water balance. 

Nursing consideration

• Draw blood from an extremity that does not have normal saline infusing into it. 
• Do not allow the client to clench and unclench his or her hand before drawing blood. 
• Any condition accompanied by prolonged vomiting, diarrhoea, will alter chloride levels.