Hypernatremia

Background

• High = >150meq/L
• High! = (Osm >350)

Clinical Features

Osm	Symptoms
350-375	Restlessness, irritability
376-400	Tremulousness, ataxia
400-430	Hyperreflexia, twitching, spasticity
>430	Seizure, coma, death

Causes of Hypernatremia

Usually secondary to decreased Total Body Water

Hypernatremia

Water loss:

• Decreased Intake
• Water loss > Na loss
  • Vomiting
  • Diarrhea
  • Sweating
  • Dialysis
  • Osmotic diuresis
• Central DI
  • Head Trauma
  • CVA
  • Tumor
  • Meningitis
• Nephrogenic DI
• Thyrotoxicosis

Sodium gain:

• Increased intake
  • Na intake
  • NaBicarb
  • Incorrect preparation of infant formula
• Renal Na retention (secondary to poor perfusion)

Evaluation

• Elevated sodium on chemistry
• Fractional excretion of sodium can help determine etiology

Management

• Normal saline until perfusion deficits corrected
  • Then switch to 1/2NS until UOP = >0.5 mL/kg/hr
  • Target 0.5 mEq/hr correction

Avoid lowering Na more than 10-15 mEq/L/day (~0.5-1.0 mEq/L/hr initially)

• Central DI → Treat with DDAVP
• Peds: >180meq/L consider peritoneal dialysis

Water Deficit

• Free water deficit = (0.6 x wt in kg) x [(serum Na/140) – 1]
• Each liter H2O Deficit increases Na by 3-5 meq/L

Disposition

• Tailor to underlying cause and severity

Complications

• Seizures
• Brain edema if corrected too quickly
• Brain shrinkage leading to cerebral vessel traction:
  • Venous congestion, thrombosis of venous sinuses
  • Arterial stretching leading to hemorrhage/infarction

See Also

• Electrolyte Abnormalities (Main)
• MDCalc: https://www.mdcalc.com/free-water-deficit-hypernatremia