Evidence-Based Management of Potassium Disorders in the Emergency Department (Pharmacology CME)

Table of Contents

 

1. Abstract
2. Case Presentations
3. Introduction
4. Critical Appraisal of the Literature
5. Pathophysiology Of Potassium Regulation
6. Etiologies Of Hypokalemia
   1. Inadequate Intake
   2. Renal Loss
   3. Gastrointestinal Loss
   4. Sweat Loss
7. Etiologies Of Hyperkalemia
   1. Pseudohyperkalemia
   2. Impaired Excretion Of Potassium
   3. Medication-Induced Hyperkalemia
      1. Potassium-Containing Agents
      2. Medications That Affect Aldosterone Secretion
      3. Medications That Cause Tubular Resistance To The Action Of Aldosterone
      4. Medications That Cause Transmembrane Shifting Of Potassium
8. Differential Diagnosis
9. Prehospital Care
10. Emergency Department Evaluation
    1. History
    2. Physical Examination
11. Diagnostic Studies
    1. Electrocardiogram Findings In Hypokalemia
    2. Electrocardiogram Findings In Hyperkalemia
12. Treatment Of Hypokalemia
13. Treatment Of Hyperkalemia
    1. Membrane Stabilization
    2. Transcellular Shift
    3. Removal Of Potassium
       1. Cation Exchange Resins
       2. Dialysis
14. Special Considerations
    1. Rapid Sequence Intubation
    2. Genetic Disorders
    3. Myocardial Infarction
    4. Digoxin Toxicity
    5. Periodic Paralysis
       1. Hypokalemic Periodic Paralysis
       2. Hyperkalemic Periodic Paralysis
       3. Andersen Syndrome
15. Controversies And Cutting Edge
16. Disposition
17. Summary
18. Risk Management Pitfalls For Potassium Emergencies In The Emergency Department
19. Time- And Cost-Effective Strategies
20. Case Conclusions
21. Clinical Pathways
    1. Clinical Pathway For Management Of Hypokalemia In The Emergency Department
    2. Clinical Pathway For Management Of Hyperkalemia In The Emergency Department
22. Tables and Figures
    1. Table 1. Severity Classifications Of Hypokalemia And Hyperkalemia
    2. Table 2. Common Causes Of Hypokalemia
    3. Table 3. Proper Phlebotomy Techniques To Reduce Pseudohyperkalemia
    4. Table 4. Medications That Can Cause Hyperkalemia
    5. Table 5. Typical Causes Of Hypokalemia In Conjunction With Laboratory Testing
    6. Table 6. Interventions Used In The Treatment Of Hyperkalemia
    7. Figure 1. Electrocardiogram With Peaked T Waves And PR Depression In Hyperkalemia
    8. Figure 2. Electrocardiogram With A Widened QRS In Hyperkalemia
    9. Figure 3. Electrocardiogram In Hyperkalemia Depicting A Sine Wave
23. References

Abstract

Hypokalemia and hyperkalemia are the most common electrolyte disorders managed in the emergency department. The diagnosis of these potentially life-threatening disorders is challenging due to the often vague symptomatology a patient may express, and treatment options may be based upon very little data due to the time it may take for laboratory values to return. This review examines the most current evidence with regard to the pathophysiology, diagnosis, and management of potassium disorders. In this review, classic paradigms, such as the use of sodium polystyrene and the routine measurement of serum magnesium, are tested, and an algorithm for the treatment of potassium disorders is discussed.

Case Presentations

An elderly woman presents with 4 days of generalized weakness and fatigue secondary to diarrhea. On examination, she appears dehydrated. During your workup, you find that she is in acute renal failure and is suffering from hyperkalemia, with a serum potassium of 6.5 mEq/L. Her ECG shows mild peaked T waves. During discussion with the admitting physician, you are asked to give the patient sodium polystyrene. You seem to recall some controversy regarding this treatment and wonder if it is really indicated for this patient.

Your next patient is a 24-year-old woman with diarrhea and vomiting. During your workup, you find that she has hypokalemia, with a potassium level of 2.2 mEq/L, an ECG with a prolonged QT interval, and a serum magnesium of 1.9 mEq/L. The patient’s internist recommends treatment with an antiemetic, oral potassium, and discharge home. You wonder if this is the best management plan.

Your third patient is a dialysis-dependent 56-year-old man who presents with shortness of breath and weakness. His serum potassium is 6.9 mEq/L, and there is evidence of fluid overload on the chest radiograph. You contact renal to arrange emergent dialysis and they recommend that you administer a “new” potassium-binding agent and discharge the patient for his regularly scheduled dialysis appointment later in the day. You wonder what these new agents are and whether best practice has recently changed without your being aware of it.

Introduction

Potassium disorders are common and potentially deadly, which makes early recognition and treatment fundamental to quality emergency care. The symptoms that a patient may experience with these disorders are typically vague and difficult to distinguish. The emergency clinician must have a heightened index of suspicion and a low threshold for testing and treating. Recent literature has questioned several age-old practices and has challenged the emergency clinician to assess new practice paradigms, including the routine ordering of serum magnesium levels in patients with hypokalemia, redrawing potassium levels in a hemolyzed sample, proper blood-drawing techniques, and the utility of sodium polystyrene sulfonate and bicarbonate in the treatment of acute hyperkalemia. This issue of Emergency Medicine Practice provides a systematic review of the newest evidence regarding the pathophysiology, diagnosis, and management of potassium-related emergencies.

Critical Appraisal Of The Literature

A MEDLINE^® search for randomized controlled trials since 2010 was conducted using the search terms hyperkalemia and hypokalemia. MEDLINE^® was also queried using the terms hyperkalemia and hypokalemia and therapy or treatment in order to identify studies that have not yet reached the randomized controlled trial phase. A total of 281 articles were identified and reviewed, with 118 being for hyperkalemia and 163 articles for hypokalemia. The literature reviewed had numerous large retrospective studies but very few randomized controlled trials for either hyperkalemia or hypokalemia. Moreover, very few articles reviewed dealt with new management strategies of these disease processes. The National Guideline Clearinghouse (www.guideline.gov) was searched and no recommendations for the treatment of hyper-kalemia or hypokalemia were found. The Cochrane Database of Systematic Reviews was also queried. No reviews have been published for hypokalemia; a review was published in 2009 for hyperkalemia, but it has not been updated.

Risk Management Pitfalls For Potassium Emergencies In The Emergency Department

1. “Sure, the patient had hypokalemia, and I was treating it with intravenous potassium, but I didn’t think she needed a monitor.”
   All patients receiving potassium via the intravenous route should be on a cardiac monitor both during and after infusion to assess for dysrhythmias.
    
2. “That end-stage renal disease patient is always here with moderate hyperkalemia. I gave him a dose of sodium polystyrene sulfate and sent him to dialysis.”
   Emergent dialysis is the treatment of choice for patients who are dialysis-dependent with hyperkalemia. The binding resins have not been proven to rapidly lower potassium levels in the acute setting.
    
3. “Although the patient’s potassium was 7.1 mEq/L, she had a normal ECG.”
   The ECG is unreliable in predicting which patients with hyperkalemia will rapidly decompensate and it should not be the sole factor in initiating treatment.
    
4. “The laboratory results were clearly due to hemolysis, so I didn’t treat the hyperkalemia.”
   Although new data have shown that not all laboratory tests need to be redrawn, particularly in patients with normal renal function and a normal ECG, the clinical picture should guide care. If you suspect renal failure with associated hyperkalemia, then the patient should be treated appropriately and tests redrawn.
    
5. “The patient’s potassium was the low end of normal after his myocardial infarction, and his cardiac arrest was most likely secondary to his underlying heart condition.”
   Hypokalemia has been associated with ventricular fibrillation in myocardial infarction patients and a serum potassium of at least 4.5 mEq/L should be maintained.
    
6. “The patient had moderate hyperkalemia with ECG changes. I gave a dose of calcium and admitted him to the internist. I can’t believe he coded when he got to the floor.”
   Calcium is a membrane stabilizer and is cardioprotective for patients with hyperkalemia. However, it does not lower the total serum potassium, and other interventions must be employed.
    
7. “Sure, the child had some fatigue, but he looked well. I sent him back to his pediatrician for a further workup.”
   Genetic renal disorders of childhood can present with vague complaints and warrant testing in the ED, if suspected.
    
8. “The patient’s potassium was 2.4 mEq/L, but she was asymptomatic. I sent her home with a prescription for oral potassium replacement and a repeat basic metabolic panel in a week.”
   Severe hypokalemia warrants intravenous potassium replacement and admission for further stabilization, due to the risk of arrhythmia.
    
9. “I treated the patient’s hyperkalemia with insulin and dextrose and sent him to the floor. I am not sure why he was unresponsive when he got there.”
   Patients treated with insulin and dextrose for hyperkalemia should be placed on a glucose monitoring protocol for several hours.
    
10. “I gave the patient one of the new potassium-binding resins for her hyperkalemia and sent her home for follow-up with her primary care physician.”
    Both sodium zirconium cyclosilicate and patiromer have not been studied in the acute management of hyperkalemia. The only proven acute management strategy for potassium removal is dialysis.

Tables And Figures

References

Evidence-based medicine requires a critical appraisal of the literature based upon study methodology and number of subjects. Not all references are equally robust. The findings of a large, prospective, randomized, and blinded trial should carry more weight than a case report.

To help the reader judge the strength of each reference, pertinent information about the study is included in bold type following the reference, where available.

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