Potassium ions extracellular/intracellular content

Growth can be assessed by measuring the content of potassium ions in the body on the following basis. Potassium ions occur mainly in intracellular fluids, in which the K concentration is about 142 mM. Extracellular fluids, on the other hand, contain much lower levels of potassium, about 10 mM. Adipose tissue is largely water free and thus contains minimal amounts of fluids and salts. The potassium ion content may be determined in growing humans. How is it possible to measure the total content of K ions in a living person A fi action of the potassium in the... 

The small fraction (2%) of the total body pt)tassium which is in the extracellular compartment is distributed proportionately between the interstitial and plasma spaces. The concentration in serum is around 4.5 mmol/l. Whereas serum potassium concentration does not vary appreciably in response to water loss or retention, factors which cause even a small or sudden shift of intracellular potassium will cause a big change in the ECF potassium content and concentration. Cellular uptake of potassium is stimulated by insulin. Of particular im wrtance is the reciprocal relationship between potassium and hydrogen ions. Many hydrogen ions are buffered inside cells. As the concentration of hydrogen ions increases with the development of acidosis, potassium ions arc displaced from the cell in order to maintain... 

Sodium ions are primarily responsible for maintaining the osmolarity of the extracellular fluid in contrast, potassium ions participate in maintaining the osmolarity of the intracellular fluid. The potassium content of plasma is too low to be able to influence osmoregulation. There are 7-150 mEq of potassium per liter in the intracellular fluid, and only 4.5 mEq/ liter in the plasma fluid. Consequently, 95% of the body potassium is intracellular, and the bulk of the potassium is found in muscle. 

Potassium is primarily an intracellular ion and, consequently, decreases in whole-body potassium may not be detected by plasma measurements (Muylle et al 1984). Although erythrocyte potassium content has been used to estimate whole-body potassium (Muylle et al 1984), its accuracy has not been validated. Moreover, the extracellular potassium concentration (reflected in the plasma) is critical for neuromuscular transmission and is, therefore, more relevant to clinical signs than whole-body potassium stores (Rose 1994). The intervention level for treatment of hypokalemia has not been established. In postoperative colic and proximal enteritis, where the prevention of ileus is a primary goal, it may be prudent to supplement if the plasma potassium concentration falls to <3.5mEq/l. In other situations, especially those being fed enterally, it may not be necessary to treat if the plasma potassium concentration is >3.0mEq/l. 

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