Fluid Management for Hypernatremia with Hyperchloremia
For a 114-pound (52 kg) patient with hypernatremia (sodium 158 mEq/L) and hyperchloremia (chloride 117 mEq/L), administer hypotonic fluids such as 0.45% NaCl or D5W to correct the free water deficit, with a maximum correction rate of 10 mmol/L per 24 hours to prevent cerebral edema.
Initial Assessment and Fluid Deficit Calculation
Calculate the free water deficit using the formula: Water deficit (L) = 0.5 × body weight (kg) × [(current Na/140) - 1] 1. For this 52 kg patient with Na 158:
- Water deficit = 0.5 × 52 × [(158/140) - 1] = 3.3 liters 1
Determine the correction rate: Maximum 0.4 mmol/L/hour or 10 mmol/L per 24 hours to prevent cerebral edema 2. For this patient, aim to reduce sodium by approximately 8-10 mEq/L in the first 24 hours 1, 2.
Fluid Selection and Administration
Primary fluid choice is 0.45% NaCl (half-normal saline) containing 77 mEq/L sodium with osmolarity ~154 mOsm/L, appropriate for moderate hypernatremia correction 3. This provides both free water and some sodium replacement 3.
Alternative option is D5W (5% dextrose in water) as it delivers no renal osmotic load and allows slow, controlled decrease in plasma osmolality 3. D5W is preferred when more aggressive free water replacement is needed 3.
Avoid isotonic saline (0.9% NaCl) as it delivers excessive osmotic load—requiring 3 liters of urine to excrete the osmotic load from just 1 liter of isotonic fluid, which risks worsening hypernatremia 3.
Initial Fluid Administration Rate
For adults, administer 25-30 mL/kg/24 hours as the baseline maintenance rate 3. For this 52 kg patient:
- Maintenance rate = 25-30 mL/kg/24h = 1,300-1,560 mL/24h (approximately 54-65 mL/hour) 3
Replace the calculated water deficit over 48-72 hours to avoid overly rapid correction 2. Distribute the 3.3 L deficit over 48 hours = approximately 69 mL/hour additional fluid 2.
Total initial infusion rate: Approximately 125-135 mL/hour of 0.45% NaCl 3, 2.
Monitoring Protocol
Check serum sodium every 4-6 hours initially during active correction to ensure the rate does not exceed 10 mmol/L per 24 hours 1, 2.
Monitor for signs of cerebral edema if correction is too rapid, including headache, altered mental status, or seizures 2. Hypernatremic dehydration is associated with the highest morbidity and mortality rate, primarily related to CNS dysfunction 2.
Assess volume status continuously by monitoring vital signs, urine output (target >0.5 mL/kg/hour), and clinical signs of hydration 1.
Management of Hyperchloremia
Hyperchloremia (Cl 117 mEq/L) typically resolves with correction of hypernatremia when using balanced hypotonic solutions 3. The elevated chloride reflects the same pathophysiology as the hypernatremia—free water deficit 3.
Use isotonic balanced solutions for maintenance once sodium normalizes to prevent recurrence, as these provide appropriate chloride content 3.
Special Considerations and Pitfalls
Never correct chronic hypernatremia faster than 10 mmol/L per 24 hours—rapid correction can cause cerebral edema due to osmotic shifts 2. Even with careful correction, CNS damage can result either from the hypernatremia itself or from overly rapid lowering 2.
Avoid normal saline in hypernatremic patients as it worsens the hyperosmolar state by delivering excessive sodium load 3, 2.
If the patient has ongoing losses (diarrhea, vomiting, excessive sweating), replace these losses separately in addition to the calculated deficit 3.
For patients with renal concentrating defects (such as diabetes insipidus), ongoing hypotonic fluid administration will be required to match excessive free water losses 3.
Adjust the rate based on clinical response: If sodium corrects too rapidly (>0.5 mmol/L/hour), slow the infusion rate 1, 2. If inadequate response after 6-8 hours, consider increasing the rate slightly while maintaining safe correction limits 1.