From the Guidelines
For a patient with a free water deficit of 2 liters and a sodium level of 152 mmol/L, I recommend using hypotonic fluids, specifically 0.45% sodium chloride (half-normal saline) or 5% dextrose in water (D5W), to correct the sodium at a safe pace of no more than 8-10 mmol/L in 24 hours to avoid osmotic demyelination syndrome. The elevated sodium level of 152 mmol/L indicates hypernatremia with significant free water deficit, suggesting dehydration. Hypotonic fluids will help replace the free water deficit while gradually lowering the sodium concentration. The body needs free water to dilute the excess sodium, and using isotonic fluids like normal saline would not effectively lower the sodium level 1.
Key Considerations
- The initial rate should be calculated to correct the sodium at a safe pace, with regular monitoring of serum sodium levels (every 2-4 hours initially) to ensure appropriate correction rate and adjust the fluid therapy accordingly.
- For a 70 kg adult, this typically translates to an infusion rate of about 100-125 mL/hour.
- Addressing the underlying cause of the hypernatremia is crucial for complete management.
- The aim is to balance losses, plus replacement of the fluid deficit over 48 hours, and to avoid a decrease in serum sodium above 8 mmol/l/day in case of hypertonic dehydration 1.
Fluid Replacement
- The choice of fluid replacement depends on the state of hydration, serum electrolyte levels, and urinary output.
- In general, 0.45% NaCl infused at 4–14 ml kg–1 h–1 is appropriate if the corrected serum sodium is normal or elevated 1.
- Once renal function is assured, the infusion should include 20–30 mEq/l potassium (2/3 KCl and 1/3 KPO4) until the patient is stable and can tolerate oral supplementation 1.
From the Research
Choosing the Fluid
To choose the appropriate fluid, we need to consider the patient's free water deficit and sodium level.
- The patient has a free water deficit of 2 litres and a sodium level of 152, indicating hypernatremia.
- According to the study 2, in unstable patients with hypernatremia, the clinician should administer isotonic intravenous fluid.
- However, the patient's stability is not mentioned, so we must consider the general approach to correcting hypernatremia.
- The study 3 suggests that the management of hypernatremia focuses on resolving the underlying cause, replenishing free water deficit, and preventing further losses while closely monitoring serum sodium concentration.
- Given the patient's free water deficit, replenishing this deficit is crucial, and isotonic intravenous fluid can be used to achieve this goal, as stated in 2.
- It is essential to aim for correction over 24 to 48 hours, with the maximal change in serum sodium between 8 to 12 mEq/L over the first 24 hours, as recommended in 2.