Elsevier

The Journal of Pediatrics

Volume 145, Issue 5, November 2004, Pages 584-587
The Journal of Pediatrics

Invited Commentary
Acute hospital-induced hyponatremia in children: A physiologic approach

https://doi.org/10.1016/j.jpeds.2004.06.077Get rights and content

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Maintenance therapy

Standard intravenous maintenance therapy7 is designed to replace ongoing physiological water losses when oral intake is suspended. These are net insensible (∼35 mL) and urinary (∼65 mL) water losses; they are indexed to metabolic rate expressed in 100 kcal/day increments. Consequently, the average allowance for water as maintenance therapy is 100 mL/100 kcal/dayb

Hypovolemia

Hypovolemia is defined as impaired circulation in which organ and tissue perfusion are reduced. Hypovolemia develops with: (1) a contraction of ECF as occurs from net loss of body fluid, including diarrhea and vomiting, renal or cerebral salt wasting, (2) extravasation of plasma into tissues as occurs with infection, burns, or trauma (“third space loss”), or (3) dislocation of blood volume into capacitance vessels as occurs with septic shock or loss of muscle tone. These conditions, acting

Brain injury

Brain injury because of hyponatremia is described as water intoxication. It results when retention of free water rapidly decreases serum sodium; brain volume increases because water rapidly equilibrates across cell membranes and solutes do so only slowly. Solutes of both cell and ECF are diluted; both cell and ECF volumes increase. Given the unique anatomic and physiologic features of the brain, these increases in brain volume cause intracranial pressure to rise. If swelling is sufficient,

Severe hypovolemia without hyponatremia

An extreme example of hypovolemia results in patients with severe burns from extensive extravisation of plasma into interstitial fluid, compromising circulation and perfusion. Plasma ADH and other vasoactive agents dramatically rise; urine flow decreases. For example, a 40% skin surface burn results in huge transfers of plasma fluid and albumin into both the burn site and normal interstitium. Current treatment is to give 80 mL/kg (2 mL/% skin surface burn) of isotonic saline or Ringer's

Gravity and hypovolemia

Gravity contributes to dislocation of blood volume. Normal young men standing upright with muscles fully relaxed develop syncope and hypotension within 15 minutes. Blood is sequestered in the lower limbs; plasma ADH increases dramatically. When the men lie down, eliminating the gravity effect, these signs abate.26 Children lying supine for extended periods lose muscle tone; this has a comparable effect, pooling blood dorsally. Anesthesia and sedation exaggerate this effect. Rapid ECF expansion

Protocol for avoiding hypovolemia

The first priority in planning fluid therapy for acutely ill children is to determine if hypovolemia is likely. If so, rapid rehydration/restoration therapy is indicated. If hypovolemia is marginal to moderate, 20 to 40 mL/kg of isotonic saline or Ringer's solution, given in 2-4 hours, should suffice. If hypovolemia is more severe, 40 to 80 mL/kg may be needed. Therapy is indexed to body weight, not to metabolic rate, because blood and ECF vary with body weight.

Surgical patients are subject to

Risks of using isotonic saline for maintenance therapy

The two proposals5., 6. to use isotonic saline as maintenance therapy, in some cases for extended periods, was recommended without describing any clinical experience. This, we believe, incurs unwarranted risks.27., 28. It is comparable to the use of hypotonic saline as initial or replacement therapy without clinical trials. Several potential problems can be anticipated. Giving isotonic saline at maintenance rates to hypovolemic patients unnecessarily delays the correcting of hypovolemia;

Summary

Children admitted with acute disease or for surgery incur a significant risk of hyponatremia if even subtle hypovolemia is present and is not corrected before they are given hypotonic saline as maintenance therapy. The risk is exaggerated if maintenance therapy is given in excess of recommendations. This risk is greatly reduced (1) by initially giving children with even subtle hypovolemia, 20 to 40 mL/kg of isotonic saline in 2-4 hours and (2) by correctly calculating maintenance therapy,

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References (29)

  • M.L. Moritz et al.

    Prevention of hospital acquired hyponatremia: a case for using isotonic saline in maintenance fluid therapy

    Pediatrics

    (2003)
  • A.L. Friedman

    Fluid and electrolyte therapy

  • M.A. Holliday et al.

    The maintenance need for water in parenteral fluid therapy

    Pediatrics

    (1957)
  • M.A. Holliday

    Extracellular fluid and its proteins: dehydration, shock, and recovery

    Pediatr Nephrol

    (1999)
  • Cited by (0)

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