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Hospital-acquired hyponatremia—why are hypotonic parenteral fluids still being used?

Nature Clinical Practice Nephrology volume 3, pages 374–382 (2007)Cite this article

Abstract

Hospital-acquired hyponatremia can be lethal. There have been multiple reports of death or permanent neurological impairment in both children and adults. The main factor contributing to the development of hospital-acquired hyponatremia is routine use of hypotonic fluids in patients in whom the excretion of free water, which is retained in response to excess arginine vasopressin (AVP), might be impaired. The practice of administering hypotonic parental fluids was established over 50 years ago, before recognition of the fact that there are numerous potential stimuli for AVP production in most hospitalized patients. Virtually all neurological morbidity resulting from hospital-acquired hyponatremia has been associated with administration of hypotonic fluids. Multiple prospective studies have shown that 0.9% NaCl is effective prophylaxis against hyponatremia. There is not a single report in the literature of neurological complications resulting from the use of 0.9% NaCl in non-neurosurgical patients. Patients at greatest risk of developing hyponatremic encephalopathy following hypotonic fluid administration are children, premenopausal females, postoperative patients, and those with brain injury or infection, pulmonary disease or hypoxemia. When hyponatremic encephalopathy develops, immediate administration of 3% NaCl is essential. In this Review, we discuss the question of why administering hypotonic fluids is unphysiologic and potentially dangerous, the settings in which isotonic fluids should be administered to prevent hyponatremia, and the appropriate treatment of hyponatremic encephalopathy.

Key Points

  • Hospitalized patients have numerous stimuli for arginine vasopressin production and are at risk of developing hyponatremia

  • Routine administration of hypotonic parenteral fluid to hospitalized patients can result in fatal hyponatremic encephalopathy

  • 0.9% NaCl (154 mmol/l) should be administered as prophylaxis against hyponatremia, except in the setting of a free water deficit or ongoing free water losses

  • Patients at greatest risk of developing neurological complications secondary to hyponatremia are children, premenopausal females, postoperative patients, and those with brain injury, brain infection or hypoxemia

  • 3% NaCl (513 mmol/l) is an essential treatment for hyponatremic encephalopathy

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Figure 1: Treatment algorithm for symptomatic hyponatremia

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Acknowledgements

We thank Karen Branstetter for her editorial assistance. JC Ayus is supported by NIH grant VO1DK0664A1. Désirée Lie, University of California, Irvine, CA, is the author of and is solely responsible for the content of the learning objectives, questions and answers of the Medscape-accredited continuing medical education activity associated with this article.

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Authors and Affiliations

  1. ML Moritz is an Associate Professor in the Division of Nephrology, Department of Pediatrics at the Children's Hospital of Pittsburgh, Pittsburgh, PA,

    Michael L Moritz

  2. JC Ayus is Professor of Medicine at the University of Texas Health Science Center at San Antonio, TX, USA.,

    Juan Carlos Ayus

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Correspondence to Michael L Moritz.

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Moritz, M., Ayus, J. Hospital-acquired hyponatremia—why are hypotonic parenteral fluids still being used?. Nat Rev Nephrol 3, 374–382 (2007). https://doi.org/10.1038/ncpneph0526

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