I. How to Use

When to Use

When managing patients with hyponatremia or hypernatremia this calculator estimates the rate by type of intravenous fluid to achieve desired correction.

Pearls / Pitfalls

  • In most cases, sodium correction for severe hyponatremia (typically defined as serum sodium <120 mEq/L) should be done in an inpatient setting, and under the guidance of expert physicians in this field such as those specializing in nephrology and critical care. Hypertonic fluids for severe, symptomatic hyponatremia requires intensive care setting due to need for frequent sodium monitoring and the risk of overcorrection.

  • The proper rate of correction of hyponatremia is important and should be determined through review of current guidelines before using this calculator. Excessively rapid correction can lead to long-term adverse outcomes such as osmotic demyelination syndrome (ODS) with excessively rapid correction of chronic hyponatremia.

  • This calculator does not account for fluid losses such as in urine and through sweat and respiration. It also does not account for intake through other sources (e.g., oral, other IV fluids). Finally, the underlying formula is accurate for 1 liter of volume infused and may have lower accuracy with greater volumes. Thus, it is important to monitor serum sodium level frequently to ensure that it is correcting appropriately

Why to Use

Determining rate of IV fluids for treatment of hyponatremia and hypernatremia is important

II. Next Steps

Advice

  • Correct chronic hyponatremia carefully.

  • Monitor sodium level frequently particularly when correcting severe hypo or hypernatremia to assess impact of therapy

  • Do not forget to correct the hyponatremia level in hyperglycemic patients with the Sodium Correction for Hyperglycemia calculator and use the corrected sodium for determining treatment goals.

  • Typically, hypertonic solutions are reserved for patients who are overtly symptomatic, such as those with seizures and severe neurologic deficits and should be conducted in an ICU setting under the guidance of expert physicians.

Management

  • Administer recommended intravenous fluid rate with careful and frequent monitoring of serum sodium as well as accurate recording of intake and output. Adjust fluid rate depending on response in serum sodium levels. Expert guidance is highly recommended for severe hypo- and hypernatremia.

Critical Actions

  • Determine appropriate rate of correction of hyponatremia based on clinical scenario

  • Chronic hyponatremia should be corrected slowly

  • Rapid correction might be necessary for severe hyponatremia with mental status changes

  • Monitor serum sodium level frequently and adjust therapy accordingly

  • Consider ICU monitoring for severe hyponatremia particularly when prescribing hypertonic fluids

  • This calculator does not account for fluid losses such as in urine and through sweat and respiration. It also does not account for intake through other sources (e.g., Oral or IV drips)

III. Evidence

Evidence Appraisal

This tools provides infusion rate of intravenous fluids of various tonicity when correcting tonicity disorders, specifically hyponatremia and hypernatremia. Serum sodium disorders are one of the most common problems in the hospital. This tool is a starting point in determining what fluids should be administered. However, it should be emphasized that there is no substitute for close monitoring of serum sodium levels when managing severe hypo- or hypernatremia. The rate of correction is under debate, particularly for hyponatremia. However, most expert guidelines suggest correction chronic hyponatremia (i.e., duration>48 hours) no greater than 6-8 mEq/L per 24 hours. In some circumstances such as seizure or altered mental status, a short, rapid correction may be appropriate.

The formula is derived from this manuscript: https://pubmed.ncbi.nlm.nih.gov/10824078/

Adrogué HJ, Madias NE. Hyponatremia. N Engl J Med. 2000;342(21):1581-1589.

The evidence is a review paper that provides a generally accepted rate of fluid infusion based on sex, age, and weight. This is generally acceptable in the field (given averages of total body water by these variables). There has not been empiric testing of the accuracy of this formula – i.e., infusing a certain amount of a certain tonicity fluid changes serum sodium by a certain amount. Moreover, clinical scenarios often change rapidly making frequent monitoring of serum sodium critical. This tool is easy to use, the variables are easily available. The rates are generally well accepted by experts even though these are not empirically tested.

In severe chronic hyponatremia, experts recommend correcting no faster than 6-8 mmol/L/day (0.5mmol/L/hr) to avoid osmotic demyelination syndrome (ODS), previously known as central pontine myelinolysis (CPM). In cases where more rapid correction is indicated (e.g., seizures), use of hypertonic (3%) saline is indicated to rapidly correct serum sodium by 4-6 meq/L to resolve symptoms and then revert to the slower rate of correction.

Literature

https://pubmed.ncbi.nlm.nih.gov/9083234/

Adrogué HJ, Madias NE. Aiding fluid prescription for the dysnatremias. Intensive Care Med. 1997 Mar;23(3):309-16. doi: 10.1007/s001340050333. PMID: 9083234.

https://pubmed.ncbi.nlm.nih.gov/10824078/

Adrogué HJ, Madias NE. Hyponatremia. N Engl J Med. 2000;342(21):1581-1589.

https://pubmed.ncbi.nlm.nih.gov/29295830/

Sterns RH. Treatment of Severe Hyponatremia. Clin J Am Soc Nephrol. 2018 Apr 6;13(4):641-649. doi: 10.2215/CJN.10440917. Epub 2018 Jan 2. PMID: 29295830; PMCID: PMC5968908.

https://pubmed.ncbi.nlm.nih.gov/24074529/

Verbalis JG, Goldsmith SR, Greenberg A, Korzelius C, Schrier RW, Sterns RH, Thompson CJ. Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations. Am J Med. 2013 Oct;126(10 Suppl 1):S1-42. doi: 10.1016/j.amjmed.2013.07.006. PMID: 24074529.

https://pubmed.ncbi.nlm.nih.gov/24569496/

Spasovski G, Vanholder R, Allolio B, Annane D, Ball S, Bichet D, Decaux G, Fenske W, Hoorn EJ, Ichai C, Joannidis M, Soupart A, Zietse R, Haller M, van der Veer S, Van Biesen W, Nagler E; Hyponatraemia Guideline Development Group. Clinical practice guideline on diagnosis and treatment of hyponatraemia. Nephrol Dial Transplant. 2014 Apr;29 Suppl 2:i1-i39. doi: 10.1093/ndt/gfu040. Epub 2014 Feb 25. Erratum in: Nephrol Dial Transplant. 2014 Jun;40(6):924. PMID: 24569496.

https://pmc.ncbi.nlm.nih.gov/articles/PMC8740981/

Chen S, Shieh M, Chiaramonte R, Shey J. Improving on the Adrogué-Madias Formula. Kidney360. 2020 Dec 4;2(2):365-370. doi: 10.34067/KID.0005882020. PMID: 35373033; PMCID: PMC8740981.