Hypokalemia

Hypokalemia is a low level of

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

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

• 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. Magnesium
  is 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.

• 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.

• 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

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:
K_deficit (in mmol) = (K_{normal lower limit} − K_measured) × 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

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