Hyperkalemia: Difference between revisions
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Increased extracellular potassium levels result in [[depolarization]] of the membrane potentials of cells. This depolarization opens some [[sodium channel|voltage-gated sodium channel]]s, but not enough to generate an action potential. After a short while, the open sodium channels inactivate and become [[refractory period|refractory]], increasing the threshold to generate an action potential. This leads to the impairment of neuromuscular, [[cardiac]], and [[gastrointestinal]] organ systems. Of most concern is the impairment of cardiac conduction which can result in [[ventricular fibrillation]] or [[asystole]]. | Increased extracellular potassium levels result in [[depolarization]] of the membrane potentials of cells. This depolarization opens some [[sodium channel|voltage-gated sodium channel]]s, but not enough to generate an action potential. After a short while, the open sodium channels inactivate and become [[refractory period|refractory]], increasing the threshold to generate an action potential. This leads to the impairment of neuromuscular, [[cardiac]], and [[gastrointestinal]] organ systems. Of most concern is the impairment of cardiac conduction which can result in [[ventricular fibrillation]] or [[asystole]]. | ||
Patients with the rare hereditary condition of [[hyperkalemic periodic paralysis]] appear to have a heightened sensitivity of muscular symptoms that are associated with transient elevation of potassium levels. Episodes of muscle weakness and spasms can be precipitated by exercise or fasting in these subjects.==[[Hyperkalemia ==[[causes|Causes]]== | Patients with the rare hereditary condition of [[hyperkalemic periodic paralysis]] appear to have a heightened sensitivity of muscular symptoms that are associated with transient elevation of potassium levels. Episodes of muscle weakness and spasms can be precipitated by exercise or fasting in these subjects.==[[Hyperkalemia | ||
==[[risk factors|Risk factors]] | |||
==Risk Factors== | |||
The kidneys normally remove excess potassium from the body. Most cases of [[hyperkalemia]] are caused by disorders that reduce the kidneys' ability to get rid of potassium. This may result from disorders such as: | |||
* [[Acute kidney failure]] | |||
* [[Chronic kidney failure]] | |||
* [[Glomerulonephritis]] | |||
* Obstructive uropathy | |||
* Rejection of a [[kidney transplant]] | |||
The hormone [[aldosterone]] regulates kidney removal of sodium and potassium. Lack of aldosterone can result in hyperkalemia with an increase in total body potassium.[[Addison's]] disease is one disorder that causes reduced aldosterone production. | |||
Any time potassium is released from the cells, it may build up in the fluid outside the cells and in the bloodstream. Acidosis leads to the movement of potassium from inside the cells to the fluid outside the cells. Tissue injury can cause the cells to release potassium. Such injury includes: | |||
* [[Burns]] | |||
* Disorders that cause blood cells to burst ([[hemolytic conditions]]) | |||
* Gastrointestinal [[bleeding]] | |||
* [[Rhabdomyolysis]] from drugs, alcoholism, coma, or certain infections | |||
* Surgery | |||
* Traumatic injury | |||
* Tumors | |||
If the kidney is working properly, and there is enough aldosterone, tissue trauma alone rarely leads to hyperkalemia. A normally functioning kidney will remove the excess potassium that has been released from the cells. | |||
Increased intake of potassium can cause hyperkalemia if kidney function is poor. Salt substitutes often contain potassium, as do many "low-salt" packaged foods. | |||
Hyperkalemia may be caused by medications, including medications that affect kidney function (potassium sparing diuretics, such as [[spironolactone]], [[amiloride]], or[[triamterene]]) and potassium supplements (especially intravenous potassium). | |||
==[[causes|Causes]]== | |||
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Revision as of 18:00, 25 July 2013
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Resident Survival Guide |
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Hyperkalemia Microchapters |
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Diagnosis |
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Treatment |
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Case Studies |
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Hyperkalemia On the Web |
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American Roentgen Ray Society Images of Hyperkalemia |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [2]; Raviteja Guddeti, M.B.B.S. [3]
Synonyms and keywords: Hyperkalaemia.
Overview
Hyperkalemia (AE) or Hyperkalaemia (BE) is an elevated blood level (above 5.0 mmol/L) of the electrolyte potassium. The prefix hyper- means high (contrast with hypo-, meaning low). The middle kal refers to kalium, which is Latin for potassium. The end portion of the word, -emia, means "in the blood". Extreme degrees of hyperkalemia are considered a medical emergency due to the risk of potentially fatal arrhythmias
Pathophysiology
Potassium is the most abundant intracellular cation. It is critically important for many physiologic processes, including maintenance of cellular membrane potential, homeostasis of cell volume, and transmission of action potentials in nerve cells. Its main dietary sources are vegetables (tomato and potato), fruits (orange and banana) and meat. Elimination is through the gastrointestinal tract and the kidney.
The renal elimination of potassium is passive (through the glomeruli), and resorption is active in the proximal tubule and the ascending limb of the loop of Henle. There is active excretion of potassium in the distal tubule and the collecting duct; both are controlled by aldosterone.
Hyperkalemia develops when there is excessive production (oral intake, tissue breakdown) or ineffective elimination of potassium. Ineffective elimination can be hormonal (inaldosterone deficiency) or due to causes in the renal parenchyma that impair excretion.
Increased extracellular potassium levels result in depolarization of the membrane potentials of cells. This depolarization opens some voltage-gated sodium channels, but not enough to generate an action potential. After a short while, the open sodium channels inactivate and become refractory, increasing the threshold to generate an action potential. This leads to the impairment of neuromuscular, cardiac, and gastrointestinal organ systems. Of most concern is the impairment of cardiac conduction which can result in ventricular fibrillation or asystole.
Patients with the rare hereditary condition of hyperkalemic periodic paralysis appear to have a heightened sensitivity of muscular symptoms that are associated with transient elevation of potassium levels. Episodes of muscle weakness and spasms can be precipitated by exercise or fasting in these subjects.==[[Hyperkalemia ==Risk factors
Risk Factors
The kidneys normally remove excess potassium from the body. Most cases of hyperkalemia are caused by disorders that reduce the kidneys' ability to get rid of potassium. This may result from disorders such as:
- Acute kidney failure
- Chronic kidney failure
- Glomerulonephritis
- Obstructive uropathy
- Rejection of a kidney transplant
The hormone aldosterone regulates kidney removal of sodium and potassium. Lack of aldosterone can result in hyperkalemia with an increase in total body potassium.Addison's disease is one disorder that causes reduced aldosterone production.
Any time potassium is released from the cells, it may build up in the fluid outside the cells and in the bloodstream. Acidosis leads to the movement of potassium from inside the cells to the fluid outside the cells. Tissue injury can cause the cells to release potassium. Such injury includes:
- Burns
- Disorders that cause blood cells to burst (hemolytic conditions)
- Gastrointestinal bleeding
- Rhabdomyolysis from drugs, alcoholism, coma, or certain infections
- Surgery
- Traumatic injury
- Tumors
If the kidney is working properly, and there is enough aldosterone, tissue trauma alone rarely leads to hyperkalemia. A normally functioning kidney will remove the excess potassium that has been released from the cells.
Increased intake of potassium can cause hyperkalemia if kidney function is poor. Salt substitutes often contain potassium, as do many "low-salt" packaged foods.
Hyperkalemia may be caused by medications, including medications that affect kidney function (potassium sparing diuretics, such as spironolactone, amiloride, ortriamterene) and potassium supplements (especially intravenous potassium).
Causes
|
Resident Survival Guide |
|
Hyperkalemia Microchapters |
|
Diagnosis |
|---|
|
Treatment |
|
Case Studies |
|
Hyperkalemia On the Web |
|
American Roentgen Ray Society Images of Hyperkalemia |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [4]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [5]; Raviteja Guddeti, M.B.B.S. [6]
Causes
Common Causes
- ACE inhibitors
- Acidosis
- Addisonian crisis
- Beta blockers
- Blood transfusion and complications
- Cirrhosis
- Diabetic nephropathy
- Increased ingestion of high potassium foods
- Malnutrition
- Renal tubular acidosis
- Renal failure
Causes by Organ System
- ↑ Sevastos N et al. (2006) Pseudohyperkalemia in serum: the phenomenon and its clinical magnitude. J Lab Clin Med, 147(3):139-44; PMID 16503244.
- ↑ Don BR et al. (1990) Pseudohyperkalemia caused by fist clenching during phlebotomy. N Engl J Med, 322(18):1290-2; PMID 2325722.
- ↑ Iolascon A et al. (1999) Familial pseudohyperkalemia maps to the same locus as dehydrated hereditary stomatocytosis. Blood, 93(9):3120-3; PMID 10216110.