Hypernatremia

• 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