Published online December 1, 2004
PEDIATRICS Vol. 114 No. 6 December 2004, pp. 1743-1744 (doi:10.1542/10.1542/peds.2004-1241)

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Hospital-Acquired Hyponatremia Is Associated With Excessive Administration of Intravenous Maintenance Fluid

Kenneth B. Roberts, MD
Moses Cone Health System
University of North Carolina School of Medicine
Greensboro, NC 27401

To the Editor.—

In their article about acute hyponatremia in hospitalized children, Hoorn et al¹ propose that hypotonic fluids not be administered to children whose plasma sodium concentrations are <138 mmol/L. In their article, Moritz and Ayus go further and recommend 0.9% sodium chloride to provide for maintenance losses,² an echo of their previous article.³ I believe that these authors (and the staff treating the patients in their report) are misinterpreting "maintenance." Although all children have maintenance needs, those ill enough to be in the hospital generally have water and sodium needs that exceed maintenance from a deficit they have incurred, ongoing losses, or both. Hypotonic fluid, containing 5% dextrose and 0.2% to 0.3% saline, is appropriate for maintenance requirements from basal metabolism but is inappropriate to repair deficits or offset abnormal losses. I would like to call attention to 4 specific issues:

1. Calculation of insensible losses: The authors calculated insensible losses as 14 mL/kg per day, which is considerably less than the 50 mL/420 kJ per day recommended by Holliday and Segar.⁴ The average age of Hoorn et al's patients was 7 years. Assuming a weight of 25 kg, 14 mL/kg per day would result in 350 mL of insensible loss, whereas 50 mL/420 kJ per day would be 800 mL. This is essentially all free water: the difference in the 2 calculations provides an explanation of why hypotonic fluid is more appropriate for maintenance than 0.9% sodium chloride.
   
2. Ignoring the large amount of sodium in 0.9% sodium chloride: For a 25-kg child receiving 1600 mL/day, 0.9% sodium chloride provides 246 mEq or 5667 mg of sodium, a whopping amount considerably greater than maintenance! D₅O·2NS provides a more appropriate 1133 mg of sodium.
   
3. Ignoring the large amount of chloride in 0.9% sodium chloride: The unphysiologic chloride load acts as a fixed acid in children who may already be acidotic from dehydration, illness, or bicarbonate loss (eg, from diarrhea).
   
4. Timing of the hyponatremia: The hyponatremia occurred early in the hospitalization or postoperatively. The early hyponatremia may well represent the practice of providing a "bolus" to bolster the circulation but then inappropriately administering 5% dextrose and 0.2% to 0.3% sodium chloride (maintenance solution) to replace the remaining portion of a deficit or to offset ongoing losses. Maintenance solution is for maintenance; solutions with additional sodium are required when additional sodium has been lost, but this bears no relationship with maintenance needs or maintenance solution.
   

A high rate of hyponatremia represents a failure to teach the difference between maintenance, deficits, and ongoing losses. We would do better to refocus on teaching these basic physiologic principles than to simply throw sodium at the problem.

REFERENCES

1. Hoorn EJ, Geary D, Robb M, Halperin ML, Bohn D. Acute hyponatremia related to intravenous fluid administration in hospitalized children: an observational study. Pediatrics. 2004;113; 1279 –1284[Abstract/Free Full Text]
2. Moritz ML, Ayus JC. Hospital-acquired hyponatremia: why are there still deaths? Pediatrics. 2004;113 :1379 –1396
3. Noritz ML, Ayus JC. Prevention of hospital-acquired hyponatremia: a case for using isotonic saline. Pediatrics. 2003;111 :227 –230[Abstract/Free Full Text]
4. Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19 :823 –832[Abstract/Free Full Text]

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PEDIATRICS (ISSN 1098-4275). ©2004 by the American Academy of Pediatrics

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