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SOURCE

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Source: Brophy DF, Flurie RW. Disorders of potassium and magnesium homeostasis. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic Approach. 10th ed. New York, NY: McGraw-Hill; 2017. http://accesspharmacy.mhmedical.com/content.aspx?bookid=1861&sectionid=134127639. Accessed March 31, 2017

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DEFINITION

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  • Serum potassium <3.5 mEq/L (<3.5 mmol/L)

    • Mild: serum potassium 3.1–3.5 mEq/L (3.1–3.5 mmol/L)

    • Moderate: serum potassium 2.5–3.0 mEq/L (2.5–3.0 mmol/L)

    • Severe: serum potassium <2.5 mEq/L (<2.5 mmol/L)

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ETIOLOGY

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  • Drug-induced (Table 1)

    • Thiazide and loop diuretics most common cause.

  • Prolonged diarrhea and/or vomiting.

  • Hypomagnesemia.

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Table Graphic Jump Location
TABLE 1.Mechanism of Drug-Induced Hypokalemia
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PATHOPHYSIOLOGY

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  • Results from total body potassium deficit or shifting of serum potassium into intracellular compartment.

  • Thiazide and loop diuretics inhibit renal sodium reabsorption, resulting in increased sodium at distal tubule, causing the distal tubule to selectively reabsorb sodium as potassium is excreted.

    • Volume contraction with diuretics stimulates secretion of aldosterone that promotes renal excretion of potassium.

  • Diarrhea and/or vomiting promote excessive loss of potassium-rich gastrointestinal (GI) fluid.

  • Hypomagnesemia reduces intracellular potassium concentration and promotes renal wasting, contributing to development of hypokalemia.

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EPIDEMIOLOGY

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  • Commonly encountered electrolyte abnormality in clinical practice.

  • Nonexistent in healthy adults.

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PREVENTION

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  • Eat potassium-rich diet:

    • Fresh fruits.

    • Vegetables.

    • Fruit juices.

    • Meats.

  • Patients on thiazide or loop diuretics should consider oral potassium supplementation.

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RISK FACTORS

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  • Age: more common in elderly patients with chronic disease.

  • Nasogastric suctioning.

  • Use of thiazide or loop diuretics.

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CLINICAL PRESENTATION

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  • Signs and symptoms are nonspecific and variable, and depend on degree of hypokalemia and rapidity of onset.

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SIGNS AND SYMPTOMS
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  • Mild hypokalemia (serum potassium 3.1–3.5 mEq/L [3.1–3.5 mmol/L])

    • Often asymptomatic.

  • Moderate hypokalemia (serum potassium 2.5–3.0 mEq/L [2.5–3.0 mmol/L])

    • Muscle cramps.

    • Muscle weakness.

    • Malaise.

    • Myalgias.

  • Severe hypokalemia (serum potassium <2.5 mEq/L [<2.5 mmol/L])

    • Cardiovascular.

      • Electrocardiogram (ECG) changes include:

        • ST-segment depression or flattening.

        • T-wave inversion.

        • U-wave elevation.

      • Clinical arrhythmias.

        • Heart block.

        • Atrial flutter.

        • Paroxysmal atrial tachycardia.

        • Ventricular fibrillation.

        • Digitalis-induced arrhythmias.

    • Musculoskeletal.

      • Cramping and impaired muscle contraction.

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DIAGNOSIS

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MEANS OF CONFIRMATION AND DIAGNOSIS
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  • Serum potassium ...

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