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Emergency Medicine > ENDOCRINE AND METABOLIC
Hypokalemia
Article Last Updated: Aug 23, 2007
AUTHOR AND EDITOR INFORMATION
Section 1 of 11  
Author: David Garth, MD, Consulting Staff, Department of Emergency Medicine, Mary Washington Hospital
David Garth is a member of the following medical societies: American Medical Association
Editors: Robin R Hemphill, MD, MPH, Associate Professor, Director, Disaster Preparedness, Department of Emergency Medicine, Vanderbilt University Medical Center; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Howard A Bessen, MD, Professor of Medicine, Department of Emergency Medicine, UCLA School of Medicine; Program Director, Harbor-UCLA Medical Center; John Halamka, MD, Chief Information Officer, CareGroup Healthcare System, Assistant Professor of Medicine, Department of Emergency Medicine, Beth Israel Deaconess Medical Center; Assistant Professor of Medicine, Harvard Medical School; Rick Kulkarni, MD, Medical Director, Assistant Professor of Surgery, Section of Emergency Medicine, Yale-New Haven Hospital
Author and Editor Disclosure
Synonyms and related keywords:
potassium level less than 3.5 mEq/L, potassium homeostasis, palpitations, skeletal muscle weakness, cramping, paralysis, paresthesias, abdominal cramping, ventricular arrhythmias, premature atrial beats, premature ventricular beats, respiratory distress, hypoventilation, respiratory failure, lethargy, fasciculations, tetany, decreased tendon reflexes, cushingoid appearance, hyperaldosteronism, magnesium depletion, ileal loop, diuretics, alkalosis, low potassium, hypokalemia
Background
Potassium is one of the body's major ions. Nearly 98% of the body's potassium is intracellular. The ratio of intracellular to extracellular potassium is important in determining the cellular membrane potential. Small changes in the extracellular potassium level can have profound effects on the function of the cardiovascular and neuromuscular systems.
The kidney determines potassium homeostasis, and excess potassium is excreted in the urine.
The reference range for serum potassium level is 3.5-5 mEq/L, with total body potassium stores of approximately 50 mEq/kg (ie, approximately 3500 mEq in a 70-kg person).
Hypokalemia is defined as a potassium level less than 3.5 mEq/L.
Moderate hypokalemia is a serum level of 2.5-3 mEq/L.
Severe hypokalemia is defined as a level less than 2.5 mEq/L.
Pathophysiology
Hypokalemia may result from conditions as varied as renal or GI losses, inadequate diet, transcellular shift (movement of potassium from serum into cells), and medications.
Frequency
United States
As many as 20% of hospitalized patients are hypokalemic; however, hypokalemia is clinically significant in only about 4-5% of these patients. Severe hypokalemia is relatively uncommon.
Up to 14% of outpatients are mildly hypokalemic, while approximately 80% of patients who are receiving diuretics become hypokalemic.
Sex
Incidence is equal in males and females.
History
The history may be vague. Hypokalemia should be suggested by a constellation of symptoms that involve the GI, renal, musculoskeletal, cardiac, and nervous systems. The patient's medications should be reviewed to ascertain whether any of them could cause hypokalemia. Common symptoms include the following:
- Palpitations
- Skeletal muscle weakness or cramping
- Paralysis, paresthesias
- Constipation
- Nausea or vomiting
- Abdominal cramping
- Polyuria, nocturia, or polydipsia
- Psychosis, delirium, or hallucinations
- Depression
Physical
Findings may include the following:
- Signs of ileus
- Hypotension
- Ventricular arrhythmias
- Cardiac arrest
- Bradycardia or tachycardia
- Premature atrial or ventricular beats
- Hypoventilation, respiratory distress
- Respiratory failure
- Lethargy or other mental status changes
- Decreased muscle strength, fasciculations, or tetany
- Decreased tendon reflexes
- Cushingoid appearance (eg, edema)
Causes
- Renal losses
- Renal tubular acidosis
- Hyperaldosteronism
- Magnesium depletion
- Leukemia (mechanism uncertain)
- GI losses
- Vomiting or nasogastric suctioning
- Diarrhea
- Enemas or laxative use
- Ileal loop
- Medication effects
- Diuretics (most common cause)
- Beta-adrenergic agonists
- Steroids
- Theophylline
- Aminoglycosides
- Transcellular shift
- Malnutrition or decreased dietary intake, parenteral nutrition
Cushing Syndrome
Hypocalcemia
Hypomagnesemia
Other Problems to be Considered
Medication side effect
Renal tubular acidosis
Lab Studies
- Serum potassium level <3.5 mEq/L (3.5 mmol/L)
- BUN and creatinine level
- Glucose, magnesium, calcium, and/or phosphorus level if coexistent electrolyte disturbances are suspected.
- Consider digoxin level if the patient is on a digitalis preparation; hypokalemia can potentiate digitalis-induced arrhythmias.
- Consider arterial blood gas (ABG): Alkalosis can cause potassium to shift from extracellular to intracellular.
Imaging Studies
- CT scan of the adrenal glands is indicated if mineralocorticoid excess is evident (rarely needed emergently).
Other Tests
- Electrocardiography
- T-wave flattening or inverted T waves
- Prominent U wave that appears as QT prolongation (see Media file 1)
- ST-segment depression
- Ventricular arrhythmias (eg, premature ventricular contractions [PVCs], torsade de pointes, ventricular fibrillation)
- Atrial arrhythmias (eg, premature atrial contractions [PACs], atrial fibrillation)
Prehospital Care
- Be attentive to the ABCs.
- If the patient is severely bradycardic or manifesting cardiac arrhythmias, appropriate pharmacologic therapy or cardiac pacing should be considered.
Emergency Department Care
- Patients in whom severe hypokalemia is suspected should be placed on a cardiac monitor; establish intravenous access and assess respiratory status.
- Direct potassium replacement therapy by the symptomatology and the potassium level. Begin therapy after laboratory confirmation of the diagnosis.
- Usually, patients who have mild or moderate hypokalemia (potassium of 2.5-3.5 mEq/L), are asymptomatic, or have only minor symptoms need only oral potassium replacement therapy. If cardiac arrhythmias or significant symptoms are present, then more aggressive therapy is warranted. This treatment is similar to the treatment of severe hypokalemia.
- If the potassium level is less than 2.5 mEq/L, intravenous potassium should be given. Admission or ED observation is indicated; replacement therapy takes more than a few hours.
- Serum potassium level is difficult to replenish if serum magnesium level is also low. Look to replace both.
Consultations
An internist or a nephrologist should be consulted for admission or follow-up care.
Oral is the preferred route for potassium repletion because it is easy to administer, safe, inexpensive, and readily absorbed from the GI tract. For patients with mild hypokalemia and minimal symptoms, oral replacement is sufficient. For patients who have severe hypokalemia and are symptomatic, both intravenous and oral replacement are necessary. While intravenous potassium dosages of up to 40 mEq/h have been advocated, patients should receive no more than 20 mEq/h IV to avoid potential deleterious effects on the cardiac conduction system. Potassium solutions should never be given as an intravenous push and should be administered as a dilute solution. Higher concentrations of intravenous potassium are damaging to the smaller peripheral veins.
Drug Category: Electrolyte supplements
Potassium is essential for transmission of nerve impulses, contraction of cardiac muscle, maintenance of intracellular tonicity, skeletal and smooth muscles, and maintenance of normal renal function. These agents increase the body's potassium level. In general, 1 mEq/L drop in potassium correlates to a loss of 100-200 mEq of total body potassium. Hypokalemia may result from the movement of potassium into cells without loss of potassium from the body.
| Drug Name | Potassium chloride, IV |
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| Description | Potassium depletion sufficient to cause 1 mEq/L drop in serum potassium requires loss of about 100-200 mEq of potassium from total body store.
In the symptomatic patient with severe hypokalemia, administer up to 40 mEq/h of this IV preparation; maintain close follow-up care, provide continuous ECG monitoring, and check serial potassium levels.
Higher dosages may increase risk of cardiac complications. Many institutions have policies that limit maximum amount of potassium that can be given per hour.
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| Adult Dose | 10-20 mEq/h IV via peripheral or central line |
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| Pediatric Dose | 0.5-1 mEq/kg/dose over 1 h; not to exceed adult maximum dose |
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| Contraindications | Hyperkalemia; renal failure; conditions in which potassium is retained; oliguria or azotemia; crush syndrome; severe hemolytic reactions; anuria; adrenocortical insufficiency |
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| Interactions | Concurrent ACE inhibitors may result in elevated serum potassium concentrations; concurrent potassium-sparing diuretics or potassium-containing salt substitutes can produce severe hyperkalemia; in patients taking digoxin, hypokalemia may result in digoxin toxicity—caution if discontinuing potassium administration in patients maintained on digoxin |
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| Pregnancy | A - Fetal risk not revealed in controlled studies in humans
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| Precautions | Do not infuse rapidly; high plasma concentrations of potassium may cause death due to cardiac depression, arrhythmias, or arrest; plasma levels do not necessarily reflect tissue levels; monitor potassium replacement therapy whenever possible by continuous or serial ECGs; when concentration >40 mEq/L infused, local pain and phlebitis may occur |
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| Drug Name | Potassium chloride, oral (Klor-Con, K-Dur) |
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| Description | Potassium depletion sufficient to cause 1 mEq/L drop in serum potassium requires a loss of about 100-200 mEq of potassium from total body store.
Available in liquid, powder, or tablet form. Any form may irritate the stomach and cause vomiting. Should be taken with food or after meals to minimize GI discomfort.
Oral potassium preparations include 8 mEq KCI slow-release tablets, 20 mEq KCI elixir, 20 mEq KCI powder, 25 mEq KCI tablet.
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| Adult Dose | 20-40 mEq PO bid/qid; not to exceed 40 mEq PO/dose |
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| Pediatric Dose | 1-4 mEq/kg/24 h PO divided bid/qid |
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| Contraindications | Hyperkalemia; renal failure; conditions in which potassium is retained; oliguria or azotemia; crush syndrome; severe hemolytic reactions; anuria; adrenocortical insufficiency |
|---|
| Interactions | Concurrent ACE inhibitors may elevate serum potassium concentrations; concurrent potassium-sparing diuretics or potassium-containing salt substitutes can produce severe hyperkalemia; in patients taking digoxin, hypokalemia may result in digoxin toxicity—caution if discontinuing potassium administration in patients maintained on digoxin |
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| Pregnancy | A - Fetal risk not revealed in controlled studies in humans
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| Precautions | Caution in cardiac disease and renal impairment; plasma levels do not necessarily reflect tissue levels |
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Further Inpatient Care
- Continue intravenous replacement of potassium as needed.
- Continue cardiac monitoring in severe hypokalemia.
- Repeat potassium level measurement every 1-3 hours.
- Identify the etiology of the hypokalemia.
Further Outpatient Care
- Repeat potassium level in 2-3 days.
In/Out Patient Meds
- Consider switching to potassium-sparing diuretic if diuretic therapy is needed.
- Take 40 mEq KCI daily for 2-3 days and repeat the potassium level.
Transfer
- Patients should be transferred only after any cardiac arrhythmias have been treated and the condition has been stabilized.
- Depending on the level of hypokalemia, an advanced cardiac life support (ACLS) ambulance should be used to allow continuous cardiac monitoring during transport.
Complications
- Replacing potassium too quickly can cause a rapid rise in the blood potassium level, leading to a relative hyperkalemia with subsequent cardiac complications.
- If hypokalemia is not corrected easily with replacement therapy, search for other coexistent metabolic abnormalities (eg, hypomagnesemia). Hypokalemia may be refractory to treatment until hypomagnesemia is corrected.
- Hypokalemia can potentiate digitalis toxicity in patients who are taking digoxin.
Prognosis
- Hypokalemia usually resolves with appropriate therapy.
Patient Education
- Diet modification is recommended for those patients who are predisposed to hypokalemia. Increase intake of bananas, tomatoes, oranges, and peaches because they are high in potassium.
- For excellent patient education resources, visit eMedicine's Endocrine System Center. Also, see eMedicine's patient education article Low Potassium.
Medical/Legal Pitfalls
- If potassium is replaced too quickly, the rapid rise of the serum potassium level can induce symptomatic hyperkalemia; however, the total body reserves of potassium might still be less than normal.
- Failure to monitor and repeat potassium levels during replacement therapy
- Failure to recognize and correct other coexistent metabolic disorders (eg, hypomagnesemia)
Special Concerns
- Do not overcorrect potassium in patients with periodic hypokalemic paralysis. This condition is a transcellular maldistribution, not a true deficit.
- Diuretic therapy, diarrhea, and chronic laxative abuse are the most common causes of hypokalemia in elderly patients.
- In patients with hypokalemia and diabetic ketoacidosis, part of the serum potassium should be administered as potassium phosphate.
| Media file 1:
Prominent U waves after the T waves in hypokalemia |
 |  View Full Size Image | |
Media type: ECG
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Hypokalemia excerpt Article Last Updated: Aug 23, 2007
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