Svilar, David

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Washington University School of MedicineDigital Commons@BeckerAll Kidneycentric2014Water, water everywhere and not a drop to drink:Choosing maintenance IV fluid tonicityDavid SvilarWashington University School of Medicine in St. LouisFollow this and additional works at: http://digitalcommons.wustl.edu/kidneycentric_allThis Article is brought to you for free and open access by the Kidneycentric at Digital Commons@Becker. It has been accepted for inclusion in All byan authorized administrator of Digital Commons@Becker. For more information, please contact engeszer@wustl.edu.Recommended CitationSvilar, David, "Water, water everywhere and not a drop to drink: Choosing maintenance IV fluid tonicity" (2014). All. Paper 5.http://digitalcommons.wustl.edu/kidneycentric_all/5Water, water everywhere and not a drop to drink1: Choosing maintenance IV fluid tonicity David Svilar, M.D., Ph.D.  DEFINITION/EPIDEMIOLOGY The use of salt solutions to expand the vascular volume has been utilized for almost one hundred years2.  During this time the methods, techniques and indications for expanding vascular volume has increased.  The original method of infusing salt water into the peritoneal space was eventually supplanted by intraveneous fluid administration.2  Hypotonic fluid administration for pediatric patients has been advocated for the past 50 years.2-4  The rationale for hypotonic fluid resuscitation is rooted in the idea that the ideal fluid is human breast or cow’s milk.4,5  It was thought that because people had evolved to digest this fluid, it would contain the correct calorie to electrolyte ratio, even though milk is given enterally and metabolized through digestion.4,5  This assumption was central to determining the amount of maintenance electrolytes required for parenteral therapy.4  Since Holiday and Segar’s landmark paper, which focused on water requirements, clinicians have widely followed their maintenance fluid suggestions, partly due to the new ease in calculating fluid requirements of variously sized children compared to previous calorie dependent methods.2  However, there is an evolving concern that using hypotonic fluids, for maintenance fluid, can cause hyponatremia.  Therefore, some clinicians now advocate that isotonic fluids, are safer and should be the standard of care, for both acute resuscitation and maintenance fluid therapy.2,5-12    PHYSIOLOGY  The central argument for transitioning to isotonic fluids is the concern for iatrogenic induced hyponatremia from excess free water administration with hypotonic solutions.5,13  Vasopressin (antidiuretic hormone, ADH) helps regulate osmolality of body fluids by manipulating water excretion.14  Although vasopressin is thought to be primarily regulated by osmolality other factors can stimulate secretion from the posterior pituitary including, a decrease in circulating blood volume and blood pressure, stress, pain, hypoglycemia, temperature increase, and angiotensin II.14  There is a greater appreciation of the many physiologic situations that induce vasopressin release in the normal, euvolemic patient independent of osmolality, particularly patients under stress or in pain.2  This increase in vasopressin release independent of osmolality or intravascular volume depletion plays an important role in iatrogenic induced hyponatremia because vasopressin limits/inhibits free water excretion.14    CLINICAL QUESTION The incidence of iatrogenic induced hyponatremia has been reported to occur in 9%-24% of hospitalized children on IV fluids.5 Studies show that iatrogenic induced hyponatremia can cause significant morbidity and even death.7  This prompted some clinicians to advocate for normal saline use as maintenance fluids.7  However, there was concern that children could not excrete the increased sodium load in isotonic saline and therefore use of normal saline may cause hypernatremia and edema.  These concerns (hyponatremia from hypotonic fluids versus hypernatremia from isotonic fluids) spawned a debate and increased interest in collecting data to support the selection of a preferred maintenance fluid3,8.  Numerous centers from around the world, with various patient populations have performed retrospective13, prospective10,11,15 and randomized controlled trials9 to determine the risk of hyponatremia when treated with hypotonic saline versus isotonic saline.  Some of the essential risk factors associated with iatrogenic hyponatremia include the tonicity of the fluid and the amount of maintenance fluid given.6,10,11,13,15-17  Both are important variables, since the argument is that reducing free water administration can be remedied by either increasing tonicity or by lowering the total amount of hypotonic solution given.10,11,15  TREATMENT Multiple studies find an increased risk of hyponatremia in children treated with hypotonic fluids for maintenance therapy when compared to isotonic maintenance fluids.9-11,13,15  Changing the rate of hypotonic fluid did not appear to have an effect as predicted on hyponatremia.  In two separate studies changing the rate of hypotonic fluids did not impact incidence of hyponatremia.10,18  Instead, the most important predictor of hyponatremia was the fluid tonicity, with hypotonic fluids more likely to cause hyponatremia.18  Two meta-analysis of several fluid trials show a decreased risk of hyponatremia if isotonic saline is used as maintenance therapy16,17.  The meta-analysis by Foster et al. reported that the relative risk of hyponatremia (sodium < 135mmol/L) was 2.37 (95% CI, 1.72-3.26) when comparing hypotonic versus isotonic saline.17  In a population at low risk for hyponatremia, this corresponds to a number needed to harm of 15 (95% CI, 9-28), while in a high risk population for hyponatremia the number needed to harm is only 4 (95% CI, 3-7).17  This is concerning due to the large number of children placed on maintenance IV fluid therapy.   Many clinicians espouse that changing to isotonic maintenance fluids would be just as dangerous as using hypotonic fluids because of the risk of hypernatremia from the increased sodium load.2,3  However, the meta-analysis by Foster et al. of 10 randomized controlled trials (n = 893) did not show an increased risk of hypernatremia as previously feared.   The relative risk of hypernatremia when using isotonic versus hypotonic saline was 0.81 (95% CI, 0.32-2.04).17  Furthermore, there was no difference in frequency of edema or hypertension between the patients receiving isotonic versus hypotonic saline.17  Subgroup analysis also favored treatment with isotonic fluids when compared to hypotonic fluids for maintenance therapy in the ICU and surgical settings.17  CONCLUSION In summary, there is a risk of iatrogenic induced hyponatremia in children treated with hypotonic IV fluids, particularly if they are in a stressed state that promotes vasopressin release.  Clinicians can reduce the rate of iatrogenic hyponatremia by using isotonic fluids.  Reducing the rate of administration when using hypotonic fluids does not have a risk reduction effect compared to treatment with isotonic fluids.10,17,18  Increasing tonicity of maintenance fluids does not increase the risk for hypernatremia, edema or swelling.17  These studies were performed in children outside of the neonatal period and should not be extrapolated to neonates or very young patients.  The clinician still must use their judgment in deciding how to best treat each patient and tailor their plan and management accordingly, but numerous studies show that isotonic saline should be the default fluid prescribed rather than the exception in the management of the hospitalized child in need of maintenance fluids.    This work is intended for review only.   It is not intended for citation, quotation, or other use in any form.    REFERENCES: 1. Coleridge ST. The Rime of the Ancient Mariner. 03/11/2006. 2. Holliday MA, Ray PE, Friedman AL. Fluid therapy for children: facts, fashions and questions. Archives of disease in childhood 2007;92:546-50. 3. Hatherill M. Rubbing salt in the wound. Archives of disease in childhood 2004;89:414-8. 4. Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics 1957;19:823-32. 5. Friedman JN, Canadian Paediatric Society ACC. Risk of acute hyponatremia in hospitalized children and youth receiving maintenance intravenous fluids. Paediatrics & child health 2013;18:102-7. 6. Au A, Bell MJ. Prevention of hospital-acquired hyponatremia in children: Are hypotonic solutions safe? Pediatric critical care medicine : a journal of the Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies 2010;11:528-9. 7. Moritz ML, Ayus JC. Prevention of hospital-acquired hyponatremia: a case for using isotonic saline. Pediatrics 2003;111:227-30. 8. Taylor D, Durward A. Pouring salt on troubled waters. Archives of disease in childhood 2004;89:411-4. 9. Choong K, Arora S, Cheng J, et al. Hypotonic Versus Isotonic Maintenance Fluids After Surgery for Children: A Randomized Controlled Trial. Pediatrics 2011;128:857-66. 10. Neville KA, Sandeman DJ, Rubinstein A, Henry GM, McGlynn M, Walker JL. Prevention of Hyponatremia during Maintenance Intravenous Fluid Administration: A Prospective Randomized Study of Fluid Type versus Fluid Rate. The Journal of pediatrics 2010;156:313-9.e2. 11. Neville KA, Verge CF, Rosenberg AR, O’Meara MW, Walker JL. Isotonic is better than hypotonic saline for intravenous rehydration of children with gastroenteritis: a prospective randomised study. Archives of disease in childhood 2006;91:226-32. 12. Moritz ML, Ayus JC. Prevention of hospital-acquired hyponatremia: do we have the answers? Pediatrics 2011;128:980-3. 13. Halberthal M, Halperin ML, Bohn D. Lesson of the week: Acute hyponatraemia in children admitted to hospital: retrospective analysis of factors contributing to its development and resolution. Bmj 2001;322:780-2. 14. Berne RM. Physiology. 5th ed. St. Louis: Mosby; 2004. 15. Eulmesekian PG, Perez A, Minces PG, Bohn D. Hospital-acquired hyponatremia in postoperative pediatric patients: prospective observational study. Pediatric critical care medicine : a journal of the Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies 2010;11:479-83. 16. Wang J, Xu E, Xiao Y. Isotonic versus hypotonic maintenance IV fluids in hospitalized children: a meta-analysis. Pediatrics 2014;133:105-13. 17. Foster BA, Tom D, Hill V. Hypotonic versus Isotonic Fluids in Hospitalized Children: A Systematic Review and Meta-Analysis. The Journal of pediatrics 2014;165:163-9 e2. 18. Yung M, Keeley S. Randomised controlled trial of intravenous maintenance fluids. Journal of paediatrics and child health 2009;45:9-14.   

Water, water everywhere and not a drop to drink:  Choosing maintenance IV fluid tonicity

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Water, water everywhere and not a drop to drink: Choosing maintenance IV fluid tonicity

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