Hypokalemia (from Latin "hypo" meaning "under", "kalium" meaning "potassium", "emia" meaning "condition of the blood", aka hypopotassemia) is low concentration of potassium K+ in blood.

• Potassium <3.5, as normal blood potassium is 3.5-5 mEq/L

• About 98% of the body's potassium is found intracellular, with the remainder in the extracellular fluid, including the blood
• The concentration gradient is maintained principally by the Na+/K+ pump

• Inadequate potassium intake, which although obvious, due to a low-potassium diet or starvation, is rare
• GI or skin loss, associated w/ heavy fluid losses that flush potassium out of the body. This can be caused by:
  • Diarrhea
  • Excessive perspiration
  • Losses associated w/ muscle-crush injury
  • Surgical procedures
  • Vomiting, although not much potassium is lost from the vomitus. Rather, heavy urinary losses of K+ in the setting of postemetic bicarbonaturia force urinary excretion
  • Pancreatic fistulae
  • Presence of adenoma
• Urinary loss, including:
  • Drugs that cause excess potassium loss in urine, including:
    • Anti-HTN, e.g. loop diuretics (e.g. furosemide), and thiazides (e.g. hydrochlorothiazide)
    • Antifungal, amphotericin B
    • Cancer drug, cisplatin
  • Diabetic ketoacidosis, due to urinary losses from polyuria and volume contraction
  • Hypomagnesemia (low magnesium in blood), as magnesium is required for adequately processing potassium. It may become evident when hypokalemia persists despite potassium supplementation
  • Alkalosis (increased blood pH), can cause temporary hypokalemia. An acute rise of blood bicarbonate concentration, causing the alkalosis, will exceed the capacity of the renal proximal tube to reabsorb this anion, and potassium will be excreted as an obligate cation partner to the bicarbonate. Metabolic alkalosis is often present in states of volume depletion, so potassium may also be lost via aldosterone-mediated mechanisms
  • Diseases involving high aldosterone levels, can cause HTN, and excessive urinary losses of potassium. This includes:
    • Renal artery stenosis
    • Tumors, generally nonmalignant, of the adrenal glands, e.g. Conn's syndrome (primary hyperaldosteronism)
    • Cushing's syndrome, can cause hypokalemiau, due to excess cortisol binding the Na/K pump, and acting like aldosterone
• Distirbution away from CCF, where factors can cause transient shifting of potassium into cells, presumably by stimulation of the Na/K pumps, including by the hormones and drugs:
  • Insulin
  • Epinephrine
  • Other beta agonists, e.g. salbutamol or salmeterol
  • Xanthines, e.g. theophylline
• Pseudohypokalemia, a decrease in the amount of potassium that occurs due to excessive uptake of potassium by metabolically active clels in a blood samplea fter it has been drawn. It is a lab artifact that may occur when blood samples remain in warm conditions for several hours before processing

• Address the cause, e.g. improving the diet, Tx diarrhea, stop the offending drug
• May not require Tx, in Pt's w/o significant source of K loss, and who don't show Sx
• Oral potassium chloride supplements (Slow-K, chlorvescent), for mild hypokalemia (>3) may be Tx
• Potassium-containing foods recommended, e..g leafy green vegetables, avocados, tomatoes, coconut water, citrus fruits, oranges, or bananas, as it is often due to poor nutritional intake
• IV supplementation, in severe hypokalemia (<3), w/ 20-40mmol/L (or mEq/L, as it is equivalent 1:1) KCl per liter over 3-4 hours, specifically, limiting it at 0.2mmol/kg/hour in kids. Peripheral lines should only give <10mmol/hour. Continuous ECG monitoring should occur at >10mmol/hour, and is done via a central line. >20mmol/hr is potentially hazardous. Giving IV potassium at faster rates may cause ventricular tachycardias and requires INTENSIVE monitoring  → need to check kidney function, since the kidneys remove excess potassium in urine
• Potassium-sparing diuretics (e.g. amiloride, tiamterene, spironolactone, eplerenone), in difficult or resistant cases of hypokalemia, as concomittant hypomagnesemia will inhibit potassium replacement, as magnesium is a cofactor for potassium uptake

Source: WA Health

• Hyperkalemia (antonym, where the concentraiton of potassium K+ in blood is ELEVATED)