Electrolyte Repletion

Potassium

• (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)

Magnesium

• 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

Phosphorus

• 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)!”

#Calcium

• 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