Electrolyte Repletion


  • (always check Mg and replete PRIOR to repleting K. Low Mg can worsen K losses)
  • Goal serum potassium level: ∼ 4.0 mEq/L
  • Expected increase in serum potassium levels: ∼ 0.1 mEq/L after an IV dose of 10 mEq
  • Use caution with repletion in patients with impaired renal function.
  • Oral uptake can be improved by administration with or after a meal.
  • Regular saline is usually preferable to 5% glucose as infusion fluid (to avoid transcellular potassium shift)??
  • Adverse effects of potassium repletion
    • Hyperkalemia
    • Cardiac arrhythmias
    • GI upset (PO administration)
      Extravasation (IV administration)
    • Local irritation (IV administration)



  • Goal serum magnesium level =2
    • In patients with an underlying cardiac disorder and/or at risk of arrhythmias: consider higher goal > 1.7 mg/dL
      1 g of IV magnesium sulfate has about 8 mEq of elemental magnesium.
      Oral repletion is generally preferred when possible
    • Magnesium repletion should be continued 1–2 days after normalization of serum levels.
    • Adverse effects
      • Soft stools, diarrhea
      • Nausea, vomiting
      • Fatigue
      • Muscle weakness, attenuation of muscle reflexes
      • Low blood pressure
      • Impaired respiratory effort, cardiac arrest 
      • Hypermagnesemia


  • Expected increase in serum phosphorus levels: ∼ 0.5 mg/dL with a dose of 0.10 mmol/kg body weight (but this is somewhat unpredictable).
  • Adverse effects of phosphate repletion
    • Hypocalcemia, hypernatremia
    • Osmotic diuresis
    • Renal failure
    • Arrhythmias
    • Confusion, dizziness, seizure, tetany
    • Precipitation with calcium (stones)
    • Hyperkalemia
    • Diarrhea, flatulence, nausea, vomiting
    • Sore throat
    • “Stones (kidney), Bones (n/a – more for PTH which inc bone resorption), Groans (indigestion, n/v, diarrhea, PUD!), Moans (lethargy), Thrones (polyuria or constipation), and Psychiatric Overtones (psych issues)!”


  • Goal serum calcium level: low–normal range (e.g., ∼ 8.5 mg/dL)
  • The ionized calcium level is the best measure of physiologically active calcium.
  • When using serum calcium, make sure to correct for albumin. Ca + Albumin defecit*0.8 = corrected albumin
  • Adverse effects of calcium repletion
    • Local irritation
    • IV extravasation and soft tissue calcifications
    • cardiac slowing… Hypotension, bradycardia, cardiac arrest




From: https://www.vumc.org/trauma-and-scc/sites/vumc.org.trauma-and-scc/files/public_files/Manual/Electrolyte%20Replacement.pdf

and Amboss

Zaloga GP, K.R., Bernards WC, Layons AJ, Fluids and Electrolytes. Critical Care, ed. T.R. Civetta JM, Kirby P.Vol. 1. 1997, Philadelphia: Lippincott-Raven. 23.63. Panello JE, Delloyer RP, Critical Care Medicine 2nd Edition 2002; St. Louis: Mosby, Inc. 1169 Polderman, et al. CCM 2000 June; 28(6) 2022-2025 Polderman et al. J. Neurology 2001 May; 94(5): 697-705

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