Potassium

Potassium

  • Major ICF cation necessary for
    • Transmission and conduction of nerve and muscle impulses
    • Cellular growth
    • Maintenance of cardiac rhythms
    • Acid-base balance
  • Sources
    • Fruits and vegetables (bananas and oranges)
    • Salt substitutes
    • Potassium medications (PO, IV)
  • Regulated by kidneys
  • Hyperkalemia
    • High serum potassium caused by
      • Impaired renal excretion
      • Shift from ICF to ECF
      • Massive intake
    • Most common in renal failure
    • Manifestations
      • Cardiac dysrhythmias
      • Cramping leg pain
      • Weak or paralyzed skeletal muscles
      • Abdominal cramping or diarrhea
    • ECG effects of Hyperkalemia
  • Decreased R wave amplitude
  • Widened QRS
  • Wide, flat P wave
  • Depressed ST segment
  • Prolonged PR interval
  • Tall, peaked T wave
      • The most clinically significant manifestations of hyperkalemia are the disturbances in cardiac conduction.
      • Cardiac depolarization is decreased, leading to flattening of the P wave and widening of the QRS complex.
      • Repolarization occurs more rapidly, resulting in shortening of the QT interval and causing the T wave to be narrower and more peaked.
      • Ventricular fibrillation or cardiac standstill may occur.
    • Nursing diagnosis
      • Risk for electrolyte imbalance related to excessive retention or cellular release of potassium
      • Risk for activity intolerance related to muscle weakness
      • Risk for injury related to muscle weakness and seizures
      • Potential complication: dysrhythmias
    • Nursing implementation
      • Eliminate oral and parenteral K intake
      • Increase elimination of K (diuretics, dialysis, Kayexalate)
      • Force K from ECF to ICF by IV insulin and a b-adrenergic agonist or sodium bicarbonate
      • Reverse membrane effects of elevated ECF potassium by administering calcium gluconate IV
  • Hypokalemia
    • Low serum potassium caused by
      • Increased loss of K+ via the kidneys or gastrointestinal tract
      • Increased shift of K+ from ECF to ICF
      • Dietary K+ deficiency (rare)
    • Manifestations
      • Cardiac most serious
      • Skeletal muscle weakness (legs)
      • Weakness of respiratory muscles
      • Decreased GI motility
      • Hyperglycemia
    • ECG effects of Hypokalemia
  • Slightly peaked P wave
  • Shallow T wave
  • Slightly prolonged PR interval
  • Prominent U wave
  • ST depression