Sodium

Electrolytes in the body include sodium, potassium, calcium, magnesium, chloride, phosphate, bicarbonate and sulphate. The main functions of sodium are to clinically maintain osmotic pressure, acid-base balance, and to transmit nerve impulses. Sodium concentration is dependent on state of hydration, body sodium content and water shifts between plasma and other body fluid compartments.

Use of Test:

Assessment and monitoring of fluid and electrolyte status especially in patients with renal or cardiac disease, possible sodium losing states and in those receiving intravenous fluids.

Potassium

Potassium is the principal intracellular electrolyte (cation). It plays an important role in acid-base balance, osmotic pressure, nerve

conduction and muscle function. Decreased blood potassium levels occur with shifting of potassium into cells, potassium loss from

gastrointestinal and biliary tracts, renal potassium excretions and reduced potassium intake. Increased potassium levels are associated

with potassium shifts from cells, with inadequate renal excretion and excessive potassium intake.

Use of Test:

Monitoring potassium status in patients with renal disease, acid-base disturbances, severe fluid and electrolyte loss, on diuretic treatment or intravenous therapy. Investigation of

mineralocorticoid status.

Chloride

Chloride is the most abundant extracellular anion. It exists in the extracellular space as a combination in sodium chloride or hypochloric acid. Chloride maintains cellular integrity through its influence on osmotic pressure and acid-base and water balance. In general, chloride is affected by the same conditions that affect sodium.

Use of Test:

Assessing the possible cause of acid-base disturbances, including calculation of the anionic gap. An increased anionic gap indicates accumulation of an anion other than chloride such as lactate, hydroxybutyrate.

Urea

Urea is produced in the liver and excreted by the kidneys. Along with CO2 it constitutes the final product of protein metabolism. The amount of excreted urea varies directly with the dietary protein intake, with increased excretion in fever, diabetes and increased adrenal gland activity. The test is used as a gross index of glomerular function and the production and excretion of urea. Rapid protein catabolism and impairment of kidney function will result in an elevated level.

Use of Test:

Investigation of renal function.

Creatinine

Creatinine is an end-product of nitrogen metabolism. It is derived from creatine, most of which is present in muscle. Serum creatinine levels are dependent on body muscle mass and creatinine is removed from the  body by the kidneys. A disorder of kidney function reduces excretion of creatinine with resultant elevated blood levels. Levels may be increased by up to 50% in normal individuals after a large meat meal.

Use of Test:

Detection of decreased glomerular filtration.