Hypokalemia
Hypokalemia | |
---|---|
Other names | Hypokalaemia, hypopotassaemia, hypopotassemia |
hypomagnesemia, not enough intake in the diet[1] | |
Diagnostic method | Blood potassium < 3.5 mmol/L[1][2] |
Treatment | Dietary changes, potassium supplements, based on the underlying cause[3] |
Frequency | 20% of people admitted to hospital[4] |
Hypokalemia is a low level of
Causes of hypokalemia include vomiting,
The speed at which potassium should be replaced depends on whether or not there are symptoms or abnormalities on an electrocardiogram.[1] Potassium levels that are only slightly below the normal range can be managed with changes in the diet.[3] Lower levels of potassium require replacement with supplements either taken by mouth or given intravenously.[3] If given intravenously, potassium is generally replaced at rates of less than 20 mmol/hour.[1] Solutions containing high concentrations of potassium (>40 mmol/L) should generally be given using a central venous catheter.[3] Magnesium replacement may also be required.[1]
Hypokalemia is one of the most common
Signs and symptoms
Mild hypokalemia is often without symptoms, although it may cause
Causes
Hypokalemia can result from one or more of these
Inadequate potassium intake
Not eating a diet with enough potassium-containing foods or fasting can cause the gradual onset of hypokalemia. This is a rare cause and may occur in those with anorexia nervosa or those on a ketogenic diet.[citation needed]
Gastrointestinal or skin loss
A more common cause is excessive loss of potassium, often associated with heavy fluid losses that flush potassium out of the body. Typically, this is a consequence of
Urinary loss
- Certain medications can cause excess potassium loss in the urine. thiazide diuretics (e.g. hydrochlorothiazide) commonly cause hypokalemia. Other medications such as the antifungal amphotericin B or the cancer drug cisplatin can also cause long-term hypokalemia. Diuretic abuse among athletes[11] and people with eating disorders[12]may present with hypokalemia due to urinary potassium loss.
- A special case of potassium loss occurs with β-hydroxybutyrate.
- A low level of magnesium in the blood can also cause hypokalemia. Magnesiumis required for adequate processing of potassium. This may become evident when hypokalemia persists despite potassium supplementation. Other electrolyte abnormalities may also be present.
- cation partner to the bicarbonate.[14]
- Disease states that lead to abnormally high herbal supplements, candies, and chewing tobacco.
- Rare hereditary defects of renal salt transporters, such as Bartter syndrome or Gitelman syndrome, can cause hypokalemia, in a manner similar to that of diuretics. As opposed to disease states of primary excesses of aldosterone, blood pressure is either normal or low in Bartter's or Gitelman's.
Distribution away from extracellular fluid
- In addition to alkalosis, other factors can cause transient shifting of potassium into cells, presumably by stimulation of the Na+/K+ pump.Stimulants (amphetamines, methylphenidate, cocaine) can also cause hypokalemia by stimulating beta-2 receptors.[18][19]
- Rare hereditary defects of muscular ion channels and transporters that cause thyroid hormone, which lead to movement of potassium from the extracellular fluid into the muscle cells.
Other
- A handful of published reports describe individuals with severe hypokalemia related to chronic extreme consumption (4–10 L/day) of cola.[20] The hypokalemia is thought to be from the combination of the diuretic effect of caffeine[21] and copious fluid intake, although it may also be related to diarrhea caused by heavy fructose ingestion.[22][23]
Pseudohypokalemia
- Pseudohypokalemia is a decrease in the amount of potassium that occurs due to excessive uptake of potassium by metabolically active cells in a blood sample after it has been drawn. It is a laboratory artifact that may occur when blood samples remain in warm conditions for several hours before processing.[24]
Pathophysiology
About 98% of the body's potassium is found
Potassium is essential for many body functions, including
In the heart, hypokalemia causes arrhythmias because of less-than-complete recovery from sodium-channel inactivation, making the triggering of an action potential less likely. In addition, the reduced extracellular potassium (paradoxically) inhibits the activity of the IKr potassium current and delays ventricular repolarization. This delayed repolarization may promote
Diagnosis
Blood
Normal potassium levels are between 3.5 and 5.0
Electrocardiogram
Hypokalemia leads to characteristic
The earliest ECG findings, associated with hypokalemia, are decreased T wave height. Then, ST depressions and T inversions appear as serum potassium levels reduce further. Due to prolonged repolarization of ventricular Purkinje fibers, prominent U waves occur (usually seen at V2 and V3 leads), frequently superimposed upon T waves, therefore producing the appearance of prolonged QT intervals, when serum potassium levels fall below 3 mEq/L.[27]
Amount
The amount of potassium deficit can be calculated using the following formula:
Kdeficit (in mmol) = (Knormal lower limit − Kmeasured) × body weight (kg) × 0.4
Meanwhile, the daily body requirement of potassium is calculated by multiplying 1 mmol to body weight in kilograms. Adding potassium deficit and daily potassium requirement would give the total amount of potassium need to be corrected in mmol. Dividing mmol by 13.4 will give the potassium in grams.[28]
Treatment
Treatment includes addressing the cause, such as improving the diet, treating diarrhea, or stopping an offending medication. People without a significant source of potassium loss and who show no symptoms of hypokalemia may not require treatment. Acutely, repletion with 10 mEq of potassium is typically expected to raise serum potassium by 0.1 mEq/L immediately after administration. However, for those with chronic hypokalemia, repletion takes time due to tissue redistribution. For example, correction by 1 mEq/L can take more than 1000 mEq of potassium over many days.[6]
Oral potassium supplementation
Mild hypokalemia (>3.0 mEq/L) may be treated by eating potassium-containing foods or by taking potassium chloride supplements in a tablet or syrup form (by mouth supplements). Foods rich in
Eating potassium-rich foods may not be sufficient for correcting low potassium; potassium supplements may be recommended. Potassium contained in foods is almost entirely coupled with phosphate and is thus ineffective in correcting hypokalemia associated with hypochloremia that may occur due to vomiting, diuretic therapy, or nasogastric drainage. Additionally, replacing potassium solely through diet may be costly and result in weight gain due to potentially large amounts of food needed. An effort should also be made to limit dietary sodium intake due to an inverse relationship with serum potassium. Increasing magnesium intake may also be beneficial for similar physiological reasons.[30]
Potassium chloride supplements by mouth have the advantage of containing precise quantities of potassium, but the disadvantages of a taste which may be unpleasant, and the potential for side-effects including nausea and abdominal discomfort. Potassium bicarbonate is preferred when correcting hypokalemia associated with metabolic acidosis.[30]
Intravenous potassium replacement
Severe hypokalemia (<3.0 mEq/L) may require
Potassium-sparing diuretics
Hypokalemia which is recurrent or resistant to treatment may be amenable to a potassium-sparing diuretic, such as amiloride, triamterene, spironolactone, or eplerenone. Concomitant hypomagnesemia will inhibit potassium replacement, as magnesium is a cofactor for potassium uptake.[30]
Popular culture
The plot of the science fiction novel Destiny's Road by Larry Niven centers around the setting's scarcity of available potassium, and the resulting deficiency and its effects on the world's colonists and their society.[34][35][36][37]
See also
- Bartter syndrome
- Gitelman syndrome
- Hypokalemic acidosis
- Potassium deficiency (plant disorder)
- Superior mesenteric artery syndrome
References
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- ^ ISBN 978-1-4557-4987-4. Archivedfrom the original on 2016-08-15.
- ISBN 978-1-4557-5642-1. Archivedfrom the original on 2016-10-01.
- ^ PMID 2624617.
- PMID 21655176.
- ISBN 978-1-4557-2304-1.
- ^ "Symptoms and Signs of Low Potassium (Hypokalemia)". Retrieved 2021-04-21.
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- ^ HealthGuru (2012-03-01). "Health.yahoo.com". Health.yahoo.com. Archived from the original on 2009-06-12. Retrieved 2012-03-10.
- PMID 19232334.
- ^ S2CID 35971172.
- ^ "Potassium (Unit Conversion)". MediCalc. Archived from the original on 1 October 2016. Retrieved 27 September 2016.
- PMID 22745618.
- doi:10.1056/feature.2015.06.16.43 (inactive 31 January 2024). Retrieved 16 November 2017.)
{{cite journal}}
: CS1 maint: DOI inactive as of January 2024 (link - ^ "Sources of Dietary Potassium" (PDF). University of Massachusetts Medical School. Archived from the original (PDF) on 3 January 2017. Retrieved 3 February 2017.
- ^ PMID 10979053.
- ^ PMID 16085929.
- ^ "How should intravenous (IV) potassium chloride be administered in adults? – SPS - Specialist Pharmacy Service – The first stop for professional medicines advice". www.sps.nhs.uk. Retrieved 2018-10-16.
- ^ "Safety Issues With Adding Lidocaine to IV Potassium Infusions (Excerpt)". Archived from the original on 2008-12-22. Retrieved 2009-05-09.
- Science Fiction Weeklyno. 48, 16 June 1997.
- ^ Di Filippo P (8 June 1997). "Destiny's Road". The Universe of Larry Niven. Archived from the original on 22 November 2019. Retrieved 13 August 2019. Reprints the review from the July 1997 issue of Science Fiction Age.
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- ^ "Review of Destiny's Road by Larry Niven". Ambidexteri (Blog). 26 January 2013. Retrieved 4 August 2019.[unreliable source?]
Further reading
- Firth J (2010). "Disorders of potassium homeostasis". In David A. Warrell, Timothy M. Cox, John D. Firth, Graham S. Ogg (eds.). Oxford Textbook of Medicine. Vol. 1 (5th ed.). Oxford: Oxford University Press. pp. 3831–3845. ISBN 978-0-19-920485-4.
- Greenlee M, Wingo, CS, McDonough, AA, Youn, JH, Kone, BC (May 5, 2009). "Narrative review: evolving concepts in potassium homeostasis and hypokalemia" (PDF). Annals of Internal Medicine. 150 (9): 619–25. PMID 19414841. NIHMSID: NIHMS800438.