Gems from the Guidelines: Treating hypernatremia

• Use hypotonic intravenous fluids to correct.
• Can undergo rapid sodium concentration correction without the risk of cerebral edema.
• Calculate the free water deficit and administer at an appropriate rate (see #3 below).
• Monitor sodium concentrations every 4-6 hours.

• It takes 24–48 hours for the brain to compensate for hypernatremia.
• Correct chronic hypernatremia slowly to prevent cerebral edema.
• Decrease serum sodium concentration by no more than 0.5 mEq/L/hr for a maximum total correction of 10–12 mEq/L/day (see #3 below).

• Perform fluid resuscitation with a buffered isotonic solution capable of expanding the intravascular space.
• Maintenance or hypotonic fluids (0.45% NaCl, 5% dextrose in water) have low sodium concentrations and are not indicated to treat hypovolemia.
• Fluids listed in Table 12c are suitable options to treat hypovolemia (5-10 mL/kg [cat] and 15-20 mL/kg [dog] given over 15–30 minutes and repeated as needed) until perfusion parameters are restored.

Free Water Deficit (FWD) in Liters (L) = [(Patient Na/Desired Na) -1] × (0.6 × Weight [kg])

FWD replacement time (hr) for acute hypernatremia = Patient Na − Target Na¹

FWD replacement time (hr) for chronic hypernatremia = (Patient Na − Target Na) × 2¹

In general, replace the free water deficit by administering 5% dextrose in water.

• Simultaneously treat by administering a buffered isotonic crystalloid (Table 12c).
• Correct dehydration over 12–24 hours to minimize shifts in sodium.¹
• Recheck sodium concentrations every 4–6 hours to prevent dramatic changes.
• Limit drinking water until the patient’s sodium is close to the target concentration.