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Isotonic Maintenance Fluid is Associated With a Lower Incidence of Hyponatremia in PICU Patients than Hypotonic Maintenance Fluids


  • Does the use of hypotonic saline as maintenance fluid increase the risk of hyponatremia in critically ill pediatric patients? And if so, does the use of isotonic fluids mitigate that risk?

Clinical Bottom Lines

  1. Emerging evidence suggests that hypotonic saline as maintenance IVF may increase the risk of iatrogenic hyponatremia in hospitalized children, particularly those who are critically ill.1
  2. Current standard of care for maintenance IVF includes (and perhaps emphasizes) the use of hypotonic fluids based on a weight-based method (Holliday-Segar) method to determine rate and sodium content.2 This RCT demonstrates that PICU patients prescribed isotonic maintenance IVF have a lower incidence of hyponatremia.
  3. It also shows that there is no increase in the development of hypernatremia or hypertension.

Summary of Key Evidence

  1. 122 patients admitted to the Peds ICU were randomized to receive either hypotonic saline or isotonic saline as maintenance fluids.1
  2. Serum sodium was measured at admission, at +6hrs, and at +24hrs.
  3. Inclusion criteria: all PICU patients who were clinically euvolemic and eunatremic between the ages of 29d and 18yrs.
  4. Exclusion criteria: CKD, clinical risk of cerebral edema, admission Na >150 or <130
  5. Table 1 shows that the randomization was appropriate with no statistically significant differences in the two groups prior to the intervention.
  6. At 6hrs: no difference in serum sodium or adverse outcomes between the two groups
  7. At 24rhs: patients receiving hypotonic saline had significantly lower serum sodium than patients receiving isotonic saline.
  8. At 24hrs: The number of patients with Na <135 was significantly higher among patients receiving hypotonic saline (20.6%) than those receiving isotonic saline (5.1%). Translates to NNT (harm) of 7.
  9. At 24hrs: No difference in incidence of hypernatremia or hypertension.

Additional Comments

  • This study was performed in Spain where there is more heterogeneity in IVF than in our hospital so a direct comparison is difficult.
  • The dropout rate in the study was very high (~50%).
  • While the 1° outcome (hyponatremia) was different between the groups at 24hrs, it is unclear how that trend would change over time. Both 1° and 2° endpoints beyond 24hrs would enhance the generalizability of the results.


  1. Montanana, et al. The use of isotonic fluid as maintenance therapy prevents iatrogenic hyponatremia in pediatrics: a randomized, controlled open study. Pediatr Crit Care Med. 2008;9:589-97.
  2. Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19:823-32.

CAT Author: Brian K. Jordan, MD, PhD

CAT Appraisers: Amanda Dempsey, MD

Date appraised: March 11, 2009

Last updated June 9, 2009
Department of Pediatrics and Communicable Diseases
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