Hypokalemia
| Hypokalemia | |
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| Potassium | |
| ICD-10 | E87.6 |
| ICD-9 | 276.8 |
| DiseasesDB | 6445 |
| MedlinePlus | 000479 |
| MeSH | D007008 |
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Hypokalemia Microchapters |
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Diagnosis |
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Treatment |
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Case Studies |
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Hypokalemia On the Web |
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American Roentgen Ray Society Images of Hypokalemia |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]; Assistant Editor(s)-In-Chief: Jack Khouri
Overview
Pathophysiology
Causes
Differential Diagnosis
| Cardiovascular | Congestive Heart Failure |
| Chemical / poisoning | Barium or toluene ingestion, Chloroquine overdose |
| Drug Side Effect | Licorice, digitalis, chronic laxative abuse, beta agonists, Amphotericin B, diuretics, corticosteroids |
| Endocrine | Adrenogenital Syndrome, Bilateral Adrenal Hyperplasia, Chewing tobacco, Cushing's Syndrome, Diabetes Insipidus, Diabetes with glucosuria, Diabetic Ketoacidosis, Hereditary pseudohyperaldosteronism, Hyperaldosteronism, Renin-secreting tumor, Steroid therapy, Stress |
| Gastroenterologic | Vomiting, diarrhea, villous adenoma of the rectum, acute pancreatitis, alcoholism with reduced intestinal absorption of potassium, chronic inflammatory bowel disease, GI fistula, "Fad" diets, pyloric stenosis, starvation, ileus |
| Genetic | hypokalemic periodic paralysis |
| Iatrogenic | total parenteral nutrition, ureterosigmoidostomy, nasogastric suction |
| Nutritional / Metabolic | malnutrition |
| Oncologic | tumors with rapid cell turnover (leukemias) |
| Psychiatric | Clay ingestion, acute hyperventilation, anorexia Nervosa, bulimia |
| Renal / Electrolyte | Alkalosis, Bartter's Syndrome, chronic glomerulonephritis, hypomagnesemia, hypovolemia, Liddle's Syndrome, malignant hypertension, metabolic acidosis, polyuric phase after acute renal failure, pseudohypokalemia, Renal Artery Stenosis, Renal Tubular Acidosis |
Diagnosis
Symptoms
The severity of symptoms depends on the degree of hypokalemia, but keep in mind that there is marked individual variability.
Constitutional
- Fatigue
- Weakness
- Vomiting
- Constipation
- Muscle cramps and paralysis (the lower extremity muscles are most commonly involved) which may involve the intestine and cause ileus
- Respiratory muscle weakness leading to respiratory failure
Cardiac
- Hypertension
- Arrhythmias including premature atrial and ventricular complexes, paroxysmal atrial or junctional tachycardia and even ventricular tachycardia or fibrillation
- Heart block
- Digoxin therapy, CAD and left ventricular hypertrophy potentiate hypokalemia effects on the heart
Renal
- Nephrogenic diabetes insipidus due to decreased concentrating ability. As a consequence, the patient presents with polyuria and polydipsia
- Increased bicarbonate reabsorption
- Increased ammonia formation which may precipitate hepatic encephalopathy in cirrhotic patients
- Decreased sodium reabsorption resulting in hyponatremia
Other
- Rhabdomyolysis
- Hyperglycemia
History
A detailed history can help depict the cause of hypokalemia.
Dietary history
Malnutrition: lack of meat and fruit intake
Medication history
- Diuretics (loop and thiazides)
- Beta agonists
- Chloroquine
- Theophylline
- Insulin
- Corticosteroids
- Licorice
- Nephrotoxic drugs (platinum-based chemotherapy, aminoglycosides)
- Laxatives
Past medical history
- Uncontrolled diabetes
- Hyperthyroidism
- Pernicious anemia
- COPD (treated with Beta agonists and theophylline)
- Cushing’s disease
- Periodic paralysis
- Ileostomy/short bowel
- Primary hyperaldosteronism
- Liddle syndrome
- Bartter and Gitelman syndrome
- Prolonged starvation
- Cancer
- Renal tubular acidosis type I and type II
Laboratory Findings
- Complete blood count (CBC)
- Blood urea nitrogen (BUN)/creatinine
- Calcium
- Magnesium
- Glucose
- Arterial blood gases
- Aldosterone level
- Renin levels
- Urinary sodium
- Urine potassium
- Levels <25 meq/day (or <15 meq/L on urine spot) rule out a renal cause of hypokalemia and suggest extrarenal potassium loss or transcellular shift
- Higher potassium excretion suggest renal losses.
- Transtubular potassium gradient (TTKG)
- TTKG= (Urine K x Plasma osmolarity)/(Plasma K x Urine osmolarity)
- A TTKG less than 2-3 indicates renal potassium conservation in a hypokalemic patient
- A urine osmolality less than plasma osmolality or urine sodium <20 mEq/L, the formula is not applicable
- Urine chloride
- <25 meq/L: vomiting or remote diuretic use
- >40 meq/L: diuretics, Bartter's, Gitelman's and mineralocorticoid excess
Electrocardiography
Overview
- Caused mainly by delayed ventricular repolarization
- Seen at potassium levels <3 meq/L (90% of patients with potassium levels <2.7 meq/L have abnormal ECG findings)
- Rapidly reversible with potassium repletion
ECG changes
- ST segment depression, decreased T wave amplitude, prominent U waves
- seen in 78% of patients with a K < 2.7 meq
- seen in 35% of patients with a K > 2.7 and < 3.0
- seen in 10% of patients with a K > 3.0 and < 3.5
- U waves are also prominent in bradycardia and LVH
- Prolongation of the QRS duration
- uncommon except in severe hyperkalemia
- Increase in the amplitude and duration of the P-wave
- Cardiac arrhythmias and AV block
- Contrary to popular belief there is not prolongation of the QTc, this is artifactually prolonged due to the U wave. In some cases there is fusion of the T and the U wave making interpretation impossible.
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Long QT interval, ST segment depression, low T waves amplitude and TU wave fusion in a hypokalemic patient. -
Consecutive ECGs of a patient with hypokalemia. ECG1
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Consecutive ECGs of a patient with hypokalemia. ECG2 -
Consecutive ECGs of a patient with hypokalemia. After correction of potassium levels. -
Hypokalemia with LVH. Image courtesy of Dr Jose Ganseman
Treatment
The most important step in severe hypokalemia is removing the cause, such as treating diarrhea or stopping offending medication.
- Patients treated with loop or thiazide diuretics can be offered medications that counteract their kaliuretic effect such as aldosterone antagonists (spironolactone and eplerenone) or distal sodium channel blockers (eg, amiloride).
- The combination of thiazide and loop diuretics should be avoided.
- Oral potassium administration is safer than the IV route.
- An oral dose should not exceed 20-40 mEq.
- IV potassium infusion should be reserved for symptomatic patients with severe hyperkalemia and patients who can't take oral supplements.
Mild hypokalemia
- Potassium levels in the range 3.0-3.5 mEq/L.
- Represent potassium deficit of 200-400 mEq.
- May be treated with oral potassium salt supplements: potassium chloride KCl (Sando-K®, Slow-K®) or potassium bicarbonate KHCO3 (which can be generated from the metabolism of many organic salts eg, potassium citrate, potassium gluconate, etc).
- Potassium-containing foods may be recommended, such as tomatoes, oranges or bananas, but they are less effective than oral supplements.
- Both dietary and pharmaceutical supplements are used for people taking diuretic medications (see Causes, above).
- KCl is the most effective replacement for metabolic alkalosis-associated hypokalemia.
- KHCO3 and the organic "alkalinizing" salts K-citrate and K-gluconate are recommended for hypokalemia associated with metabolic acidosis (chronic diarrhea, renal tubular acidosis,etc).
Severe hypokalemia
- Potassium levels below 3.0 mEq/L
- Potassium levels between 2.0 and 3.0 correspond to 400-800 mEq deficit.
- It may require intravenous supplementation. Typically, saline is used, with 20-40 mEq KCl per liter over 3-4 hours (ie, at an infusion rate of 10 mEq/L/h)
- Giving IV potassium at faster rates may predispose to ventricular tachycardias and requires intensive ECG monitoring.
- Giving IV KCl at doses >60 mEq/L are painful and can cause venous necrosis.
- Difficult or resistant cases of hypokalemia may be amenable to amiloride, a potassium-sparing diuretic, or spironolactone.
- When replacing potassium intravenously, infusion via central line is encouraged to avoid the frequent occurrence of a burning sensation at the site of a peripheral IV and the aforementioned venous necrosis. When peripheral infusions are necessary, the burning can be reduced by diluting the potassium in larger amounts of IV fluid, or mixing 3 ml of 1% lidocaine to each 10 meq of kcl per 50 ml of IV fluid. The practice of adding lidocaine, however, raises the likelihood of serious medical errors [3].
- Potassium infusions via a central line can reach 200 mEq/L (20 mEq in 100 mL of isotonic saline (see below)) but the administration rate should not be greater than 10–20 mEq per hour.
- Saline solutions are preferred to prevent potassium transcellular shifting that is triggered by dextrose-induced insulin release!