For Maintenance Fluids, Reach for Isotonic Saline

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Are you still reflexively reaching for hypotonic saline for maintenance hydration? Check the research.

It has been a busy night and you are driving the admit team crazy. You have just identified two more kids who should probably be admitted. Bed 1 is a six- month old with bronchiolitis. She is at the peak of her illness and is not taking her formula very well. You are planning to admit her for supportive care, mainly to prevent dehydration. For maintenance fluids, babies are supposed to get D5 0.2 NaCl, right?

Bed 2 is a post-operative tonsillectomy child who has been to the ED twice in the last 24 hours for pain and dehydration. The first time you hydrated him in the ED and sent him home but now he has bounced back and you plan to admit him for pain management and fluids. You bolused him with normal saline and his heart rate has come down nicely. He is five years old. In medical school you gave kids this age D5 0.45 NaCl for maintenance. Is this still the best choice?

Past Practices
Maintenance fluids are given to patients to provide water and electrolyte needs. In 1957 Holliday and Segar (see references) published a paper linking maintenance water needs to energy expenditure. Their method established the standard we still use today to calculate IV fluid rates for pediatric patients. The bulk of their paper was devoted to their proposal for free water infusion, which was based on a thorough review of available evidence. Their proposal for electrolyte needs, however, was thrown into one paragraph just before the paper’s conclusion. This paragraph starts by acknowledging that “With respect to maintenance needs for electrolyte, less precise data are available”. They then compared the electrolyte composition of human and cow’s milk and concluded that electrolyte amounts that “fall between the intakes provided by human milk and cow’s milk should therefore be acceptable as maintenance needs.” This corresponded to about 0.2 NaCl, or quarter-normal saline. It is interesting to note one other paper that was published in 1957. This was WB Schwartz and colleagues’ first description of SIADH.

Most physicians have been taught to use 0.9 NaCl (normal saline) for boluses, and either dextrose 5% with 0.2 NaCl (D5 quarter-normal) or dextrose 5% with 0.45 NaCl (D5 half-normal) for maintenance. Both 0.2 NaCl and 0.45 NaCl are hypotonic fluids, 0.9 NaCl is considered isotonic.

In February 2003, Michael Moritz and Juan Carlos Ayus published a paper in the journal Pediatrics questioning this approach. They noted that hypotonic maintenance fluids lead to a high incidence of hyponatremia in hospitalized children, including more than 50 reported cases of neurologic morbidity with 26 deaths from hyponatremic encephalopathy. They pointed out that states of ADH excess were common in the inpatient setting.

Triggers for ADH Release
Triggers for ADH release included decreased intravascular volume, as would be expected, but also nonhemodynamic triggers such as CNS disturbance from infection, head injury or tumors, lung disease including pneumonia, bronchiolitis and asthma, cancer, certain medications, nausea and vomiting, pain, and stress. The post-operative state was particularly associated with increased ADH secretion and resulting hyponatremia. Some deaths from hyponatremia had occurred in previously healthy children after relatively minor surgeries. Because nonhemodynamic triggers for ADH secretion were so widespread in children admitted to the hospital, they proposed that only isotonic fluids be used for maintenance.

Since 2003 there have been multiple studies including randomized, controlled clinical trials that have compared outcomes of children given hypotonic versus isotonic maintenance IV fluids. These have confirmed that hypotonic fluids are more likely to produce low serum sodium in various populations of hospitalized pediatric patients. No study has shown hypernatremia or fluid overload due to isotonic fluids in these patients. It is important to note, however, that neonates have unique physiologic needs and were not included in these studies. For that reason, the recommendation to use isotonic fluids was not extended to patients in the first two to three months of life until more data are available.

Case Conclusions
So what do we do with our two admissions? Both children should receive D5/0.9 NaCl. Our six month old with bronchiolitis has a well-described nonhemodynamic reason for increased ADH release and should be given D5 0.9 NaCl for maintenance fluids. Our five-year-old post-operative child has multiple risk factors for increased ADH secretion and should also receive D5 0.9 NaCl. In fact, most children who do not have a disease state associated with large free water losses (such as a renal concentrating defect or voluminous secretory diarrhea) should receive isotonic maintenance fluids.

Our Childrens’ Hospital recently convened a committee that determined that isotonic fluids should be the default maintenance fluids for admitted children over the age of three months unless otherwise indicated for their unique disease state. No more knee-jerk hypotonic saline orders.

REFERENCES

  1. Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics 1957;19;823.
  2. Schwartz WB, Bennet W, Curelop S, Bartter FC. A syndrome of renal sodium loss and hyponatremia probably resulting from inappropriate secretion of antidiuretic hormone. Am J Med. 1957;23:529-542.
  3. Moritz ML, Ayus JC. Prevention of hospital-acquired hyponatremia: a case for using isotonic saline. Pediatrics 2003;111:227-230.
  4. Brazel PW, McPhee IB. Inappropriate secretion of antidiuretic hormone in post-operative scoliosis patients. Spine 1996;21(6):724-727.
  5. Kannan L, Lodha R, Vivekananhan S, et al. Intravenous fluid regimen and hyponatraemia among children: a randomized controlled trial. Pediatr Nephrol. 2010;25(11):2303-2309.
  6. Yung M, Keeley S. Randomised controlled trial of intravenous maintenance fluids. J Paedri Health. 2009;45(1-2):9-14.
  7. Neville KA, Sandeman DJ, Rubinstein A, et al. Prevention of hyponatremia during maintenance intravenous fluid administration: a prospective randomized study of fluid type versus fluid rate. J Pediatr. 2010;156(2):313-319.
  8. Choong K, Arora S, Cheng J. et al. Hypotonic versus isotonic maintenance fluids after surgery for children: a randomized controlled trial. Pediatrics 2011;128(5):857-866.
  9. Rey C, Los-Arcos M, Hernandez A, et al. Hypotonic versus isotonic maintenance fluids in critically ill children: a multicenter prospective randomized study. Acta Paediatr. 2011;100(8):1138-1143.
  10. Saba TG, Fairbairn J, Houghton F, et al. A randomized controlled trial of isotonic versus hypotonic maintenance intravenous fluids in hospitalized children. BMC Pediatr. 2011;11:82.
  11. Coulthard MG, Long DA, Ullman AJ, Ware RS. A randomized controlled trial of Hartmann’s solution versus half normal saline in postoperative paediatric spinal instrumentation and craniotomy patients. Arch Dis Child. 21012;97(6):491-496.
  12. Friedman JN, Beck CE, DeGroot J, et al. Comparison of isotonic and hypotonic intravenous maintenance fluids: a randomized clinical trial. JAMA Pediatr. 2015;169(5):445-451.
  13. Wang J, Xu E, Xiao Y. Isotonic versus hypotonic maintenance IV fluids in hospitalized children: a meta-analysis. Pediatrics 2014;133:105-113.
  14. McNab s, Ware RS, Neville KA, et al. Isotonic versus hypotonic solutions for maintenance intravenous fluid administration in children. Cochrane Database Syst Rev. 2014;12:CD009457.
  15. Padua AP, et al. Pediatr Nephrol, 2015 Epub ahead of print.

ABOUT THE AUTHOR

PEDIATRICS SECTION EDITOR
Dr. Levine is a professor of pediatrics in the Division of Pediatric Emergency Medicine at the University of North Carolina.

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