Nephrology Book

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Hypokalemia

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  1. Pathophysiology
    1. Approximate Total body potassium = 55 meq/kg
    2. Serum Potassium decreased 1 meq/dl: 350 meq K+ deficit
    3. Serum Potassium less than 2 meq/dl: 1000 meq K+ deficit
  2. Symptoms and Signs (when Serum Potassium < 2.5)
    1. General
      1. Malaise
      2. Fatigue
    2. Neurologic
      1. Weakness
      2. Decreased Deep Tendon Reflexes
      3. Paresthesia
      4. Cramps
      5. Restless legs Syndrome
      6. Rhabdomyolysis
      7. Paralysis
    3. Gastrointestinal
      1. Constipation
      2. Ileus
      3. Exacerbated Hepatic Encephalopathy
    4. Cardiovascular
      1. Orthostatic Hypotension
      2. Hypertension
      3. Arrhythmias (especially with Digoxin use)
    5. Renal
      1. Metabolic Alkalosis
      2. Polyuria, Polydipsia
      3. Decreased GFR
      4. Glucose Intolerance
  3. Labs
    1. Electrocardiogram
      1. T Waves flattened
      2. Prominent U Waves
      3. ST depression
  4. Diagnosis
    1. Exclude Transcellular Potassium Shift
    2. Check 24 hour Urine Potassium and Urine Sodium
      1. Sample should have total Urine Sodium > 100 meq
    3. Interpretation
      1. Urine Potassium <20 meq/day
        1. Extrarenal Potassium Loss
      2. Urine Potassium >20 meq/day
        1. Renal Potassium Loss
  5. Management
    1. See Potassium Replacement

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