POTASSIUM
Oct 15, 2009 5:51:39 GMT 10
Post by Tom Meulman on Oct 15, 2009 5:51:39 GMT 10
POTASSIUM
Of the potassium in the body, almost 98% is located within the cells; the remaining 2% is in the extra cellular fluid. This situation is opposite to that which exists for sodium.
Maintaining high levels within the cell (intracellular) and low potassium levels outside the cell (extra cellular) is critical.
This is accomplished with the sodium/potassium pumps located in the cell membrane.
Low potassium within the cell may cause abnormalities in many biologic processes; including the cell volume, acid-base balance, production of RNA and Glycogen, and dramatically reduces the ability of the cells to support muscle contractions.
Potassium intake and excretion determine the total body potassium content. Equally important is the distribution of potassium between extra cellular and intracellular fluid. If potassium intake were not matched by excretion, high serum potassium would soon result.
Under normal circumstances salivary and gastrointestinal potassium losses are minor, therefore excretion of potassium by the kidneys is vital.
On the other hand, the fluid that is filtered by the kidneys contains much more potassium than is present in the extra cellular fluid. Therefore re-absorption of potassium by the kidneys is also vital to normal potassium balance.
In health, and without the interference of well meaning trainers, the kidneys efficiently maintain potassium within a narrow range. However, in contrast to the kidneys ability to completely re-absorb sodium, small amounts of potassium continue to be lost even when potassium levels are low. It is therefore important that potassium levels are maintained by the appropriate diet, or by supplementation where required.
Internal Potassium Balance
This refers to the distribution of potassium within the cell (intracellular) and the potassium in the extra cellular fluid.
When potassium intake temporarily exceeds the ability of the kidneys to excrete it, the cells then take up more potassium to prevent the accumulation of excess potassium in the extra cellular fluid.
However, when kidney and gastrointestinal losses exceed potassium intake, transfer of potassium from the cells into extra cellular fluid occurs. While this delays the onset of low serum potassium level it can have a detrimental effect on the ability of the muscle cells to support efficient muscle contractions.
Factors known to affect the handling of potassium by the kidneys are:
(1) The amount of potassium in the diet
(2) The amount of sodium and fluid being re-absorbed by the kidneys.
(3) Bicarbonate accompanying sodium through the kidneys, (bicarbonate increases the excretion of potassium).
(4) Aldosterone, this is a mineralocorticoid produced by the Adrenal gland, not only in response to dehydration, but also in response to an increased extra cellular concentration of potassium.
Aldosterone stimulates sodium re-absorption and potassium excretion by the kidneys, and therefore increases the likelihood of a low body potassium level in dehydration.
With chronic diarrhoea, loss of large quantities of potassium in faeces can occur.
Finally with vomiting, even though potassium losses in gastric juice may be minor, it is the loss of gastric juice Hydrochloric Acid and resulting dehydration, which may cause Metabolic Alkalosis and trigger a loss of large amounts of potassium in the urine and cause low serum potassium.
Hypokalemia (Low Serum Potassium)
This may occur because of decreased potassium intake, redistribution of potassium from outside the cell (extra cellular fluid) to inside the cell (intra cellular fluid), because of loss of potassium from the body, and in Metabolic and Respiratory Alkalosis.
Hyperkalemia (High Serum Potassium)
This may occur due to increased potassium intake, an inability of the kidneys to excrete potassium, and in Metabolic and Respiratory Acidosis.
In metabolic acidosis accumulation of Hydrogen Ions in the extra cellular fluid causes the transfer of hydrogen ions to the intracellular fluid, potassium ions then shift from intra cellular to extra cellular fluid.
Acidosis also influences the kidneys to retain more potassium due to the lower availability of Bicarbonate.
In Respiratory Acidosis, it is Hydrochloric and Carbonic Acids that displace potassium ions from the cells.
Potassium Levels
Since 98% of body potassium is located within the cell and not available for measurement, determining whether or not potassium deficit is present, is an indirect process.
Normal Potassium Serum levels in a greyhound with Acidosis may still indicate low cellular Potassium levels, while low Potassium level in a greyhound suffering Alkalosis may indicate a redistribution of Potassium from extra cellular fluid to intracellular fluid.
Therefore any determination of potassium levels in a blood test, must take into consideration both the hydration state of the Greyhound and the possible existence of either acidosis or alkalosis.
Severe tissue trauma, such as torn muscles with obvious oedema, or severe bruising may cause significant cellular release of potassium.
Good kidney function generally prevents Hyperkalemia. However, greyhounds that are already suffering from some stress and dehydration may become affected.
Both high (hyper), and low potassium levels (hypo) cause muscle weakness.
Life threatening Hypokalemia (low)is rare, and treatment consists of giving a Potassium Chloride supplement.
Severe Hyperkalemia (high) is potentially fatal due to heart damage, and treatment should not be delayed.
Treatment is generally aimed at reducing the effect of potassium on the heart by giving Calcium and reducing extra cellular potassium with intravenous Sodium Bicarbonate or lactated Ringer's solution.
Of the potassium in the body, almost 98% is located within the cells; the remaining 2% is in the extra cellular fluid. This situation is opposite to that which exists for sodium.
Maintaining high levels within the cell (intracellular) and low potassium levels outside the cell (extra cellular) is critical.
This is accomplished with the sodium/potassium pumps located in the cell membrane.
Low potassium within the cell may cause abnormalities in many biologic processes; including the cell volume, acid-base balance, production of RNA and Glycogen, and dramatically reduces the ability of the cells to support muscle contractions.
Potassium intake and excretion determine the total body potassium content. Equally important is the distribution of potassium between extra cellular and intracellular fluid. If potassium intake were not matched by excretion, high serum potassium would soon result.
Under normal circumstances salivary and gastrointestinal potassium losses are minor, therefore excretion of potassium by the kidneys is vital.
On the other hand, the fluid that is filtered by the kidneys contains much more potassium than is present in the extra cellular fluid. Therefore re-absorption of potassium by the kidneys is also vital to normal potassium balance.
In health, and without the interference of well meaning trainers, the kidneys efficiently maintain potassium within a narrow range. However, in contrast to the kidneys ability to completely re-absorb sodium, small amounts of potassium continue to be lost even when potassium levels are low. It is therefore important that potassium levels are maintained by the appropriate diet, or by supplementation where required.
Internal Potassium Balance
This refers to the distribution of potassium within the cell (intracellular) and the potassium in the extra cellular fluid.
When potassium intake temporarily exceeds the ability of the kidneys to excrete it, the cells then take up more potassium to prevent the accumulation of excess potassium in the extra cellular fluid.
However, when kidney and gastrointestinal losses exceed potassium intake, transfer of potassium from the cells into extra cellular fluid occurs. While this delays the onset of low serum potassium level it can have a detrimental effect on the ability of the muscle cells to support efficient muscle contractions.
Factors known to affect the handling of potassium by the kidneys are:
(1) The amount of potassium in the diet
(2) The amount of sodium and fluid being re-absorbed by the kidneys.
(3) Bicarbonate accompanying sodium through the kidneys, (bicarbonate increases the excretion of potassium).
(4) Aldosterone, this is a mineralocorticoid produced by the Adrenal gland, not only in response to dehydration, but also in response to an increased extra cellular concentration of potassium.
Aldosterone stimulates sodium re-absorption and potassium excretion by the kidneys, and therefore increases the likelihood of a low body potassium level in dehydration.
With chronic diarrhoea, loss of large quantities of potassium in faeces can occur.
Finally with vomiting, even though potassium losses in gastric juice may be minor, it is the loss of gastric juice Hydrochloric Acid and resulting dehydration, which may cause Metabolic Alkalosis and trigger a loss of large amounts of potassium in the urine and cause low serum potassium.
Hypokalemia (Low Serum Potassium)
This may occur because of decreased potassium intake, redistribution of potassium from outside the cell (extra cellular fluid) to inside the cell (intra cellular fluid), because of loss of potassium from the body, and in Metabolic and Respiratory Alkalosis.
Hyperkalemia (High Serum Potassium)
This may occur due to increased potassium intake, an inability of the kidneys to excrete potassium, and in Metabolic and Respiratory Acidosis.
In metabolic acidosis accumulation of Hydrogen Ions in the extra cellular fluid causes the transfer of hydrogen ions to the intracellular fluid, potassium ions then shift from intra cellular to extra cellular fluid.
Acidosis also influences the kidneys to retain more potassium due to the lower availability of Bicarbonate.
In Respiratory Acidosis, it is Hydrochloric and Carbonic Acids that displace potassium ions from the cells.
Potassium Levels
Since 98% of body potassium is located within the cell and not available for measurement, determining whether or not potassium deficit is present, is an indirect process.
Normal Potassium Serum levels in a greyhound with Acidosis may still indicate low cellular Potassium levels, while low Potassium level in a greyhound suffering Alkalosis may indicate a redistribution of Potassium from extra cellular fluid to intracellular fluid.
Therefore any determination of potassium levels in a blood test, must take into consideration both the hydration state of the Greyhound and the possible existence of either acidosis or alkalosis.
Severe tissue trauma, such as torn muscles with obvious oedema, or severe bruising may cause significant cellular release of potassium.
Good kidney function generally prevents Hyperkalemia. However, greyhounds that are already suffering from some stress and dehydration may become affected.
Both high (hyper), and low potassium levels (hypo) cause muscle weakness.
Life threatening Hypokalemia (low)is rare, and treatment consists of giving a Potassium Chloride supplement.
Severe Hyperkalemia (high) is potentially fatal due to heart damage, and treatment should not be delayed.
Treatment is generally aimed at reducing the effect of potassium on the heart by giving Calcium and reducing extra cellular potassium with intravenous Sodium Bicarbonate or lactated Ringer's solution.