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Pediatric Dehydration

  • Author: Alex Koyfman, MD; Chief Editor: Timothy E Corden, MD  more...
 
Updated: Oct 04, 2015
 

Pathophysiology

Dehydration versus volume depletion

The terms dehydration and volume depletion are commonly used interchangeably but they refer to different physiologic conditions resulting from different types of fluid loss.[1] Volume depletion denotes reduction of effective circulating volume in the intravascular space, whereas dehydration denotes loss of free water in greater proportion than the loss of sodium. The distinction is important because volume depletion and dehydration can exist independently or concurrently and the treatment for each is different. However, much of clinical literature does not differentiate between the 2 conditions; this article will therefore follow this convention and use the terms dehydration, hypovolemia, and volume depletion interchangeably to refer to intravascular fluid deficits here.

Body fluid distribution

The body contains 2 major fluid compartments: the intracellular fluid (ICF) and the extracellular fluid (ECF). The ICF comprises of two thirds of the total body water (TBW), while the ECF accounts for the remaining third. The ECF is further divided into the interstitial fluid (75%) and plasma (25%). The TBW comprises approximately 70% of body weight in infants, 65% in children, and 60% in adults.

Infants' and children’s higher body water content, along with their higher metabolic rates and increased body surface area to mass index, contribute to their higher turnover of fluids and solute. Therefore, infants and children require proportionally greater volumes of water than adults to maintain their fluid equilibrium and are more susceptible to volume depletion. Significant fluid losses may occur rapidly, leading to depletion of the intravascular volume.

Sodium

Volume depletion can be concurrent with hyponatremia. This is characterized by plasma volume contraction with free water excess. An example is a child with diarrhea who has been given water to replace diarrheal losses. Free water is replenished, but sodium and other solutes are not.

In hyponatremic volume depletion, the patient may appear more ill clinically than actual fluid losses would otherwise indicate. The degree of volume depletion may be clinically overestimated. Serum sodium levels less than 120 mEq/L may result in seizures—the risk of seizure is much higher in the setting of acute onset of hyponatremia, as opposed to gradual onset. If intravascular free water excess is not corrected during volume replenishment, the shift of free water to the intracellular fluid compartment may cause cerebral edema, especially in children.

In hypernatremic volume depletion, plasma volume contracts with a disproportionately larger loss of free water. An example is the child with diarrhea whose fluid losses have been replenished with hypertonic soup, boiled milk, water and baking soda, or improperly diluted infant formula. Volume has been restored, but free water has not. The degree of volume depletion may be underestimated and the patient may appear less ill clinically than fluid losses indicate. Usually, at least a 10% volume deficit exists with hypernatremic volume depletion.

As in hyponatremia, hypernatremic volume depletion may result in serious central nervous system (CNS) effects as a result of structural changes in central neurons. However, cerebral shrinkage occurs instead of cerebral edema. This may result in intracerebral hemorrhage, seizures, coma, and death. Overly rapid correction of hypernatremia, however, may result in cerebral edema. For this reason, volume restoration should be performed gradually over 24 hours or more. Gradual restoration prevents a rapid shift of fluid across the blood-brain barrier and into the intracellular fluid compartment.

Potassium

Potassium shifts between intracellular and extracellular fluid compartments occur more slowly than free water shifts. Serum potassium levels may not reflect intracellular potassium levels. Although a potassium deficit is present in all patients with volume depletion, it is not usually clinically significant. However, failure to correct for a potassium deficit during volume replacement may result in clinically significant hypokalemia. Potassium should not be added to replacement fluids until adequate urine output is obtained.

Acid and base problems

The most common acid-base derangement that occurs with volume depletion, especially in infants, is metabolic acidosis. Mechanisms include bicarbonate loss in stool, ketone production from starvation, and lactic acid production from decreased tissue perfusion in hypovolemia. Decreased renal perfusion also causes decreased glomerular filtration rate, which, in turn, leads to decreased hydrogen (H+) ion excretion. These factors can combine to produce a metabolic acidosis.

In most patients, acidosis is mild and easily corrected with volume restoration; increased renal perfusion permits excretion of excess H+ ions in the urine. Administration of glucose-containing fluids further decreases ketone production.

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Etiology

The mechanisms of dehydration may be broadly divided into 3 categories: (1) decreased intake due to diseases such as stomatitis, (2) increased output from diarrhea or osmotic diuresis from uncontrolled diabetes mellitus, and (3) increased insensible losses such as with fever.

Pediatric dehydration is frequently the result of increased output from gastroenteritis, characterized by vomiting and diarrhea.[2] However, vomiting and diarrhea may be caused by other processes as summarized below.

CNS causes of vomiting include the following:

  • Infections
  • Increased intracranial pressure
  • Psychogenic vomiting is not seen in infants and is rare in children

GI causes of vomiting include the following:

Endocrine causes of vomiting include the following:

Renal causes of vomiting include the following:

GI causes of diarrhea include the following:

  • Gastroenteritis
  • Malabsorption (eg, milk intolerance, excessive fruit juice)
  • Intussusception
  • Irritable bowel syndrome
  • Inflammatory bowel disease
  • Short gut syndrome

Endocrine causes of diarrhea include the following:

  • Congenital adrenal hypoplasia
  • Addisonian crisis
  • Diabetic enteropathy

Volume depletion from increased output not caused by vomiting or diarrhea may be divided into renal or extrarenal causes. Renal causes of volume depletion include the following:

  • Use of diuretics
  • Renal tubular acidosis
  • Renal failure (eg, renal trauma, urinary tract obstruction, salt-wasting nephritis)
  • Diabetes insipidus, hypothyroidism, and adrenal insufficiency

Extrarenal causes of volume depletion include the following:

  • Third-space extravasation of intravascular fluid (eg, pancreatitis, peritonitis, sepsis, heart failure)
  • Hemorrhage

Other causes of volume depletion as mentioned above include poor oral intake and insensible losses from fever, sweating, burns, or pulmonary processes.

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Overview

Dehydration is a common complication of illness observed in pediatric patients presenting to the emergency department (ED). Early recognition and early intervention are important to reduce risk of progression to hypovolemic shock and end-organ failure.

In most cases, volume depletion in children is caused by fluid losses from vomiting or diarrhea. On physical examination, combinations of findings can be used to determine the degree of dehydration. Laboratory studies are of limited utility in cases of mild dehydration, but they may be considered under certain conditions and are recommended in patients with more severe dehydration.

Mild or moderate volume depletion should be treated with oral rehydration when possible. Intravenous fluid therapy is necessary when oral therapy fails or volume depletion is severe.

For patient education information, see the Children's Health Center, as well as Dehydration in Children.

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Epidemiology

Dehydration, particularly from gastroenteritis, is a common pediatric complaint in the ED. Approximately 30 million children are affected annually, with 1.5 million presenting to outpatient care, 200,000 requiring hospitalizations, and 300 dying in the United States.[4]

Worldwide, according to the Centers for Disease Control and Prevention (CDC), for children younger than 5 years, the annual incidence of diarrheal illness is approximately 1.5 billion, while deaths are estimated between 1.5 and 2.5 million per year. Though these numbers are staggering, they actually represent an improvement from the early 1980s, when the death rate was approximately 5 million per year.[4]

Infants and younger children are more susceptible to volume depletion than older children. In general, however, pediatric patients with volume depletion have an excellent prognosis if they are appropriately treated.

Morbidity varies with the degree of volume depletion and the underlying cause. The severely volume-depleted infant or child is at risk for death from cardiovascular collapse. Hyponatremia resulting from replacement of free water alone may cause seizures. Improper management of volume repletion may cause iatrogenic morbidity or mortality.

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Contributor Information and Disclosures
Author

Alex Koyfman, MD Assistant Professor, Department of Emergency Medicine, University of Texas Southwestern Medical Center, Parkland Memorial Hospital

Alex Koyfman, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Coauthor(s)

Carrie Ng, MD Resident Physician, Department of Pediatrics, Bellevue Hospital Center, New York University School of Medicine

Carrie Ng, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Emergency Physicians, American Institute of Ultrasound in Medicine

Disclosure: Nothing to disclose.

Mark P Foran, MD, MPH Assistant Professor of Emergency Medicine, New York University School of Medicine; Attending Emergency Physician, Bellevue Hospital Center and NYU Langone Medical Center

Mark P Foran, MD, MPH is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Public Health Association, Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Chief Editor

Timothy E Corden, MD Associate Professor of Pediatrics, Co-Director, Policy Core, Injury Research Center, Medical College of Wisconsin; Associate Director, PICU, Children's Hospital of Wisconsin

Timothy E Corden, MD is a member of the following medical societies: American Academy of Pediatrics, Phi Beta Kappa, Society of Critical Care Medicine, Wisconsin Medical Society

Disclosure: Nothing to disclose.

Acknowledgements

Richard G Bachur, MD Associate Professor of Pediatrics, Harvard Medical School; Associate Chief and Fellowship Director, Attending Physician, Division of Emergency Medicine, Children's Hospital of Boston

Richard G Bachur, MD is a member of the following medical societies: American Academy of Pediatrics, Society for Academic Emergency Medicine, and Society for Pediatric Research

Disclosure: Nothing to disclose.

Ann G Egland, MD Consulting Staff, Department of Operational and Emergency Medicine, Walter Reed Army Medical Center

Ann G Egland, MD is a member of the following medical societies: American College of Emergency Physicians, American Medical Association, Association of Military Surgeons of the US, Medical Society of Virginia, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Terrance K Egland, MD Director, Business Planning and Development, Bureau of Medicine and Surgery

Terrance K Egland, MD is a member of the following medical societies: American Academy of Pediatrics

Disclosure: Nothing to disclose.

James Li, MD Former Assistant Professor, Division of Emergency Medicine, Harvard Medical School; Board of Directors, Remote Medicine

Disclosure: Nothing to disclose.

Alison Wiley Lozner, MD Resident Physician, Harvard Affiliated Emergency Medicine Residency, Brigham and Women's Hospital; Clinical Fellow in Emergency Medicine, Harvard Medical School

Alison Wiley Lozner, MD is a member of the following medical societies: American Academy of Emergency Medicine and American College of Emergency Physicians

Disclosure: Nothing to disclose.

James Kimo Takayesu, MD, MSc Assistant Professor in Surgery, Director of Undergraduate Medical Education, Consulting Staff, Massachusetts General Hospital; Associate Residency Director, Harvard Affiliated Emergency Medicine Residency Partners

James Kimo Takayesu, MD, MSc is a member of the following medical societies: Alpha Omega Alpha, American College of Emergency Physicians, Sigma Xi, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Wayne Wolfram, MD, MPH Associate Professor, Department of Emergency Medicine, Mercy St Vincent Medical Center

Wayne Wolfram, MD, MPH is a member of the following medical societies: American Academy of Emergency Medicine, American Academy of Pediatrics, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

References
  1. Mange K, Matsuura D, Cizman B, et al. Language guiding therapy: the case of dehydration versus volume depletion. Ann Intern Med. 1997 Nov 1. 127(9):848-53. [Medline].

  2. Singhi SC, Shah R, Bansal A, Jayashree M. Management of a child with vomiting. Indian J Pediatr. 2013 Apr. 80(4):318-25. [Medline].

  3. Glaser NS, Ghetti S, Casper TC, Dean JM, Kuppermann N. Pediatric diabetic ketoacidosis, fluid therapy, and cerebral injury: the design of a factorial randomized controlled trial. Pediatr Diabetes. 2013 Mar 13. [Medline]. [Full Text].

  4. King CK, Glass R, Bresee JS, Duggan C. Managing acute gastroenteritis among children: oral rehydration, maintenance, and nutritional therapy. MMWR Recomm Rep. 2003 Nov 21. 52:1-16. [Medline].

  5. Steiner MJ, DeWalt DA, Byerley JS. Is this child dehydrated?. JAMA. 2004 Jun 9. 291(22):2746-54. [Medline].

  6. Wathen JE, MacKenzie T, Bothner JP. Usefulness of the serum electrolyte panel in the management of pediatric dehydration treated with intravenously administered fluids. Pediatrics. 2004 Nov. 114(5):1227-34. [Medline].

  7. Lozon MM. Pediatric vascular access and blood sampling techniques. Roberts JR, Hedges JR. Clinical Procedures in Emergency Medicine. 4th ed. Philadelphia: WB Saunders; 2004. 357-8.

  8. Jauregui J, Nelson D, Choo E, Stearns B, Levine AC, Liebmann O, et al. The BUDDY (Bedside Ultrasound to Detect Dehydration in Youth) study. Crit Ultrasound J. 2014. 6 (1):15. [Medline].

  9. Jauregui J, Nelson D, Choo E, Stearns B, Levine AC, Liebmann O, et al. The BUDDY (Bedside Ultrasound to Detect Dehydration in Youth) study. Crit Ultrasound J. 2014. 6(1):15. [Medline]. [Full Text].

  10. Spandorfer PR, Alessandrini EA, Joffe MD, Localio R, Shaw KN. Oral versus intravenous rehydration of moderately dehydrated children: a randomized, controlled trial. Pediatrics. 2005 Feb. 115(2):295-301. [Medline].

  11. Freedman SB, Adler M, Seshadri R, Powell EC. Oral ondansetron for gastroenteritis in a pediatric emergency department. N Engl J Med. 2006 Apr 20. 354(16):1698-705. [Medline].

  12. Kersten H. Oral ondansetron decreases the need for intravenous fluids in children with gastroenteritis. J Pediatr. 2006 Nov. 149(5):726. [Medline].

  13. Alhashimi D, Alhashimi H, Fedorowicz Z. Antiemetics for reducing vomiting related to acute gastroenteritis in children and adolescents. Cochrane Database Syst Rev. 2006 Oct 18. CD005506. [Medline].

  14. American Academy of Pediatrics. Practice parameter: the management of acute gastroenteritis in young children. American Academy of Pediatrics, Provisional Committee on Quality Improvement, Subcommittee on Acute Gastroenteritis. Pediatrics. 1996 Mar. 97(3):424-35. [Medline].

  15. Barkin RM, Ward DG. Infectious diarrheal disease and dehydration. Marx JA. Rosen's Emergency Medicine: Concepts and Clinical Practice. 6th ed. Philadelphia, Pa: Mosby/Elsevier; 2006. Vol 3: 2623-34.

  16. Hom J, Sinert R. Evidence-based emergency medicine/systematic review abstract. Comparison between oral versus intravenous rehydration to treat dehydration in pediatric gastroenteritis. Ann Emerg Med. 2009 Jul. 54(1):117-9. [Medline].

 
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Table. Physical Examination Findings in Pediatric Dehydration
Symptom Degree of Dehydration
Mild (< 3% body weight lost) Moderate (3-9% body weight lost) Severe (>9% body weight lost)
Mental status Normal, alert Restless or fatigued, irritable Apathetic, lethargic, unconscious
Heart rate Normal Normal to increased Tachycardia or bradycardia
Quality of pulse Normal Normal to decreased Weak, thready, impalpable
Breathing Normal Normal to increased Tachypnea and hyperpnea
Eyes Normal Slightly sunken Deeply sunken
Fontanelles Normal Slightly sunken Deeply sunken
Tears Normal Normal to decreased Absent
Mucous membranes Moist Dry Parched
Skin turgor Instant recoil Recoil < 2 seconds Recoil >2 seconds
Capillary refill < 2 seconds Prolonged Minimal
Extremities Warm Cool Mottled, cyanotic
Adapted from King CK, Glass R, Bresee JS, et al. Managing acute gastroenteritis among children: oral rehydration, maintenance, and nutritional therapy. MMWR Recomm Rep. Nov 21 2003;52(RR-16):1-16.[4]
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