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eMedicine Journal
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Emergency Medicine
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Endocrine And Metabolic
Hypokalemia Synonyms, Key Words, and Related Terms: 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 |
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Author Information | Introduction | Clinical | Differentials | Workup | Treatment | Medication | Follow-up | Miscellaneous | Test Questions | Pictures | Bibliography
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 | AUTHOR INFORMATION | Section 1 of 12    |
Authored by David Garth, MD, Consulting Staff, Department of Emergency Medicine, Mary Washington Hospital
David Garth, MD, is a member of the following medical societies: American Academy of Emergency Medicine
Edited by 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, UCLA School of Medicine; Program Director, Department of Emergency Medicine, 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; and Rick Kulkarni, MD, Medical Director, Assistant Professor of Surgery, Section of Emergency Medicine, Yale-New Haven Hospital
| Author's Email: | David Garth, MD |  |
|---|---|---|
| Editor's Email: | Robin R Hemphill, MD, MPH |
eMedicine Journal, September 20 2005, VOLUME 6,
Number 9
| INTRODUCTION | Section 2 of 12  |
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:
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.
| CLINICAL | Section 3 of 12 |
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:
Physical: Findings may include the following:
Causes:
| DIFFERENTIALS | Section 4 of 12 |
Cushing Syndrome
Hypocalcemia
Hypomagnesemia
Other Problems to be Considered:
Medication side effect
Renal tubular acidosis
| WORKUP | Section 5 of 12 |
Lab Studies:
Imaging Studies:
Other Tests:
| TREATMENT | Section 6 of 12 |
Prehospital Care: Be attentive to the ABCs.
Emergency Department Care:
Consultations: An internist or a nephrologist should be consulted for admission or follow-up care.
| MEDICATION | Section 7 of 12 |
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 IV and oral replacement are necessary. While IV 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 IV push and should be administered as a dilute solution. Higher concentrations of IV 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 -- 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 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. |
|---|---|
| Adult Dose | 10-20 mEq/h IV via peripheral or central line |
| Pediatric Dose | 0.5-1 mEq/kg/dose over 1 h; not to exceed adult maximum dose |
| 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 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 |
| Pregnancy | A - Safe in pregnancy |
| 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 |
| Drug Name | Potassium chloride, oral (Klor-Con, K-Dur) -- 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. |
|---|---|
| Adult Dose | 20-40 mEq PO bid/qid; not to exceed 40 mEq PO/dose |
| Pediatric Dose | 1-4 mEq/kg/24 h PO divided bid/qid |
| 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 |
| Pregnancy | A - Safe in pregnancy |
| Precautions | Caution in cardiac disease and renal impairment; plasma levels do not necessarily reflect tissue levels |
| FOLLOW-UP | Section 8 of 12 |
Further Inpatient Care:
Further Outpatient Care:
In/Out Patient Meds:
Transfer:
Complications:
Prognosis:
Patient Education:
| MISCELLANEOUS | Section 9 of 12 |
Medical/Legal Pitfalls:
Special Concerns:
| TEST QUESTIONS | Section 10 of 12 |
CME Question 1: Which of the following electrocardiographic findings is not seen with hypokalemia?
A: T-wave flattening
B: U waves
C: Inverted T waves
D: Peaked T waves
E: ST segment depression
The correct answer is D: All of the above ECG findings, except for peaked T waves, are seen in hypokalemia. Peaked T waves are seen in hyperkalemia.
CME Question 2: Which electrolyte abnormality makes correction of hypokalemia more difficult?
A: Hyponatremia
B: Hypochloremia
C: Hypomagnesemia
D: Hypophosphatemia
E: None of the above
The correct answer is C: Normalization of potassium may not be possible unless coexistent hypomagnesemia is corrected. Magnesium is a cofactor for the sodium-potassium–ATP pump. In severe hypomagnesemia, this pump does not function well and prevents potassium from correcting appropriately.
Pearl Question 1 (T/F): The use of non–potassium-sparing diuretics is the most common cause of hypokalemia.
The correct answer is True: Diuretics cause loss of potassium in the urine.
Pearl Question 2 (T/F): 40 mEq is the recommended maximum amount of potassium that can be safely administered per hour in the adult patient.
The correct answer is True: Administration of intravenous potassium supplements at concentrations higher than 40 mEq per hour may cause cardiac conduction complications.
Pearl Question 3 (T/F): The preferred route for potassium replacement is oral.
The correct answer is True: Oral potassium replacements are easy to administer, safe, inexpensive, and readily absorbed, with minimal cardiac conduction system effects in comparison to the IV route.
Pearl Question 4 (T/F): Acidosis causes potassium to shift from intracellular to extracellular space, while alkalosis causes the reverse.
The correct answer is True: Acidosis causes potassium to shift from intracellular to extracellular space, while alkalosis causes the reverse.
| PICTURES | Section 11 of 12 |
| Caption: Picture 1. Prominent U waves after the T waves in hypokalemia | |
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| Picture Type: ECG | |
| BIBLIOGRAPHY | Section 12 of 12 |
| NOTE: |
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| Medicine is a constantly changing science and not all therapies are clearly established. New research changes drug and treatment therapies daily. The authors, editors, and publisher of this journal have used their best efforts to provide information that is up-to-date and accurate and is generally accepted within medical standards at the time of publication. However, as medical science is constantly changing and human error is always possible, the authors, editors, and publisher or any other party involved with the publication of this article do not warrant the information in this article is accurate or complete, nor are they responsible for omissions or errors in the article or for the results of using this information. The reader should confirm the information in this article from other sources prior to use. In particular, all drug doses, indications, and contraindications should be confirmed in the package insert. FULL DISCLAIMER |
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Author Information | Introduction | Clinical | Differentials | Workup | Treatment | Medication | Follow-up | Miscellaneous | Test Questions | Pictures | Bibliography
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