Potassium (K), a cation, is the most abundant cation in the body cells. Ninety-seven percent of the body's potassium is found in the intracellular fluid (ICF) and 2-3% is found in the extracellular fluid (ECF), Which comprises of intravascular (in vessels) and interstitial fluids (between tissues). Potassium is also plentiful in the gastrointestinal tract. It is the 2-3% in the ECF that is all important in neuromuscular function. Potassium is constantly moving in and out of cells according to the body's needs, under the influence of the sodium-potassium pump1.
K+ participates in the regulation of such processes as protein and glycogen synthesis2.
The normal serum potassium concentration ranges from 3.5 mEq to 5.5 mEq/liter3; even minor variations are significant. The normal plasma/serum potassium range is narrow; therefore, a serum potassium level outside the normal range may be life threatening. A serum potassium level less than 2.5 mEq/L or greater than 7.0 mEq/L can cause cardiac arrest. Thus, serum potassium values need to be closely monitored.
Normal renal function is necessary for maintenance of potassium balance since 80% of the potassium excreted daily from the body is by way of the kidneys. The other 20% is lost through the bowel and sweat glands. Potassium must be replaced daily; approximately 40 mEq to 60 mEq/day suffice in the adult if there are no abnormal losses occurring. Dietary intake in the average adult is 50 mEq to 100mEq/day. Potassium influences both skeletal and cardiac muscle activity. For example, alterations in its concentration change myocardial irritability and rhythm. Alterations in acid-base balance have a significant effect on potassium distribution. The mechanism involves shifts of K+ between the cells and extracellular fluid. Hypokalemia can cause alkalosis and, vice versa, alkalosis can cause hypokalemia. For example hydrogen ions move out of the cells in alkalotic states to help correct the high pH and potassium ions move in (to maintain electroneutrality). Hyperkalemia can cause acidosis and vice versa, acidosis can cause hyperkalemia. For example, in acidotic states, some of the excess hydrogen ions enter the cells to help correct plasma pH. In so doing, potassium ions are released from the cells in order to maintain electroneutrality. Knowledge of the above facts helps in the detection of abnormal potassium state when pH disturbances are present. In such situations it is possible that the serum potassium levels will appear normal even when total body deficits or excesses are present.
II. SHORT (QA) REGARDING POTASSIUM
1. Why K+ is so important for our body ?
Potassium plays an important role in cell function and in neuromuscular transmission. In the cells, K+ participates in the regulation of such processes as protein and glycogen synthesis.
2. Is oral intake (foods rich with potassium) might fulfill daily potassium requirement ?
Theoretically we could full fill from our daily food. In fact many problems could arise such kind of the food, meals habit, etc which could consider not meet our K+ requirement, especially when we are having some diseases. For examples:
Foods sample that supply 60 mEq of K+ :
Foods Weight (g) Vegetables
a. Potatoes and beans 500
b. Peas 5000
a. Bananas 800
b. Oranges 1200
Beef or chicken 600
3. Banana familiarly known as fruit rich K+. How many mEq of K in Banana and How much of them will be absorbed ?
4. Similarly from the above question no.2 in order to provide 60 mEq of K, we should take 800 g of banana. It is almost 8-10 peaces of banana (depending the kind of banana, example: Pisang Ambon). Most of the K+ ingested is absorbed. But one could not provide his daily requirement of potassium by taking only banana.
- The Barter site: http//:potassium_page.htm.
- Burton David Rose. Clinical Physiology of Acid Base and Electrolyte Disorders, 4th ed. McGraw Hill, 1994. p 763.)
- Halperin, Goldstein. FLUID, ELECTROLYTE AND ACID-BASE PHYSIOLOGY: A Problem-Based Approach, 2nd ed. WB Saunders, 1994. p 358.Reference: Burton David Rose. Clinical Physiology of Acid Base and Electrolyte Disorders, 4th ed. McGraw Hill, 1994. p 763.)