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
- 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