Hypernatremia

Categories: Nephrology

  • General
    • MCly due to lack of water access or excess insensible losses
      • Hypervolemic Hypernatremia
        • Iatrogenic
        • Exogenous Glucocorticoids/Cushings
        • Primary Hyperaldosteronism
      • Euvolemic Hypernatremia
        • Diabetes Insipidus
          • Nephrogenic vs. Central
      • Hypovolemic Hypernatremia
        • Renal Losses
          • Diuresis
          • Renal failure
        • Extrarenal losses
          • Typically diarrhea
  • Symptoms
    • Progressive as hypernatremia worsens:
      • Restlessness or muscle weakness
      • Insominia
      • Lethargy
      • AMS
      • Coma
  • Management
    • 1) Calculate free-water deficit (MdCalc): ((Na-140)/140) x TBW - Estimate TBW: 50% of body weight in women, 60% men
    • 2) Administer deficit over 48-72h, without decrease in plasma Na+ concentration by >10mM/24h - A fast rate of correction (>10-12 mEq/day) has not been shown to be associated with worse outcomes 30948456
    • 3) Account for Ongoing Water Losses
      • Calculate free-water clearance (FWC):
        • FWC = V x (1 – (UNa + Uk)/PNa) where V is urinary volume, UNa is urinary Na+, Uk is urinary K+, and PNa is plasma Na+
    • 4) Insensible Losses ~10 ml/kg per day; less if ventilated, more if febrile
    • 5) Add above components and correct the water deficit over 48-72h replace daily water loss
  • Treatment
    • Oral water if tolerating PO intake
    • If not tolerating oral intake:
      • Free water flushes via NG tube (400-600ml boluses q4-6hrs)
      • IV Dextrose in water (D2.5W or D5W)
      • If Hypovolemic:
        • 0.9% saline(isotonic) until euvolemic, then 5% dextrose (hypotonic) or 0.45% saline (hypotonic)
    • DI: D5W is used
    • Acidotic (diarrhea): Na+HCO3- is a 5% dextrose solution or may use LR
  • References
    • 30948456 : Chauhan, K., Pattharanitima, P., Patel, N., Duffy, A., Saha, A., Chaudhary, K., Debnath, N., Van Vleck, T., Chan, L., Nadkarni, G. N., & Coca, S. G. (2019). Rate of Correction of Hypernatremia and Health Outcomes in Critically Ill Patients. Clinical journal of the American Society of Nephrology : CJASN, 14(5), 656–663. https://doi.org/10.2215/CJN.10640918

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