- Author: Lennox H Huang, MD, FAAP; Chief Editor: Timothy E Corden, MD more...
Dehydration describes a state of negative fluid balance that may be caused by numerous disease entities. Diarrheal illnesses are the most common etiologies. Worldwide, dehydration secondary to diarrheal illness is the leading cause of infant and child mortality.
The negative fluid balance that causes dehydration results from decreased intake, increased output (renal, GI, or insensible losses), or fluid shift (ascites, effusions, and capillary leak states such as burns and sepsis). The decrease in total body water causes reductions in both the intracellular and extracellular fluid volumes. Clinical manifestations of dehydration are most closely related to intravascular volume depletion. As dehydration progresses, hypovolemic shock ultimately ensues, resulting in end organ failure and death.
Young children are more susceptible to dehydration due to larger body water content, renal immaturity, and inability to meet their own needs independently. Older children show signs of dehydration sooner than infants due to lower levels of extracellular fluid (ECF).
Dehydration can be categorized according to osmolarity and severity. Serum sodium is a good surrogate marker of osmolarity assuming the patient has a normal serum glucose. Dehydration may be isonatremic (130-150 mEq/L), hyponatremic (< 130 mEq/L), or hypernatremic (>150 mEq/L). Isonatremic dehydration is the most common (80%). Hypernatremic and hyponatremic dehydration each comprise 5-10% of cases. Variations in serum sodium reflect the composition of the fluids lost and have different pathophysiologic effects, as follows:
Isonatremic (isotonic) dehydration occurs when the lost fluid is similar in sodium concentration to the blood. Sodium and water losses are of the same relative magnitude in both the intravascular and extravascular fluid compartments.
Hyponatremic (hypotonic) dehydration occurs when the lost fluid contains more sodium than the blood (loss of hypertonic fluid). Relatively more sodium than water is lost. Because the serum sodium is low, intravascular water shifts to the extravascular space, exaggerating intravascular volume depletion for a given amount of total body water loss. [1, 2]
Hypernatremic (hypertonic) dehydration occurs when the lost fluid contains less sodium than the blood (loss of hypotonic fluid). Relatively less sodium than water is lost. Because the serum sodium is high, extravascular water shifts to the intravascular space, minimizing intravascular volume depletion for a given amount of total body water loss. [2, 3, 4]
Neurologic complications can occur in hyponatremic and hypernatremic states. Severe hyponatremia may lead to intractable seizures, whereas rapid correction of chronic hyponatremia (>2 mEq/L/h) has been associated with central pontine myelinolysis. During hypernatremic dehydration, water is osmotically pulled from cells into the extracellular space. To compensate, cells can generate osmotically active particles (idiogenic osmoles) that pull water back into the cell and maintain cellular fluid volume. During rapid rehydration of hypernatremia, the increased osmotic activity of these cells can result in a large influx of water, causing cellular swelling and rupture; cerebral edema is the most devastating consequence. Slow rehydration over 48 hours generally minimizes this risk.
Determination of the cause of dehydration is essential. Poor fluid intake, excessive fluid output, increased insensible fluid losses, or a combination of the above may cause intravascular volume depletion. Successful treatment requires identification of the underlying disease state.
Common causes of dehydration include the following:
Stomatitis: Pain may severely limit oral intake.
Diabetic ketoacidosis (DKA): Dehydration is caused by osmotic diuresis. Weight loss is caused by both excessive fluid losses and tissue catabolism. Rapid rehydration, especially rapid initial volume resuscitation, may be associated with a poor neurologic outcome. DKA requires very specific and controlled treatment (see Diabetic Ketoacidosis).
Febrile illness: Fever causes increased insensible fluid losses and may affect appetite.
Pharyngitis: This may decrease oral intake.
Life-threatening causes of dehydration include the following:
Diabetic ketoacidosis (DKA)
Burns: Fluid losses may be extreme. Very aggressive fluid management is required (see Burns, Thermal).
GI obstruction: This is often associated with poor intake and emesis. Bowel ischemia can result in extensive capillary leak and shock.
Heat stroke: Hyperpyrexia, dry skin, and mental status changes may occur. 
Cystic fibrosis: This results in excessive sodium and chloride losses in sweat, placing patients at risk for severe hyponatremic hypochloremic dehydration.
Diabetes insipidus: Excessive output of very dilute urine can result in large free water losses and severe hypernatremic dehydration.
Thyrotoxicosis: Weight loss is observed, despite increased appetite. Diarrhea occurs.
United States statistics
Diarrheal illnesses in children causes 3 million physician visits, 220,000 hospitalizations (10% of all children who require hospitalization), and 400 deaths per year. Children younger than 5 years are at the highest risk. On average, North American children younger than 5 years have 2 episodes of gastroenteritis per year.
Diarrheal illnesses with subsequent dehydration account for nearly 4 million deaths per year in infants and children. The overwhelming majority of these deaths occur in developing nations.
The prognosis is excellent if the child is promptly and effectively treated. However, the child with severe dehydration and hypovolemic shock can have significant morbidity and mortality if treatment is delayed.
Mortality and morbidity generally depend on the severity of dehydration and the promptness of oral or intravenous rehydration. If treatment is rapidly and appropriately obtained, morbidity and mortality are low.
Routine use of hypotonic parenteral fluids in hospitalized children has been associated with hyponatremia and subsequent neurologic complications and death. Monitoring the efficacy and complications of parenteral rehydration with accurate fluid balances and serum electrolytes is crucial.
Complications may include irreversible shock, sagittal or other venous sinus thrombosis, intractable seizures, and renal failure.
Bettari L, Fiuzat M, Shaw LK, Wojdyla DM, Metra M, Felker GM, et al. Hyponatremia and long-term outcomes in chronic heart failure--an observational study from the Duke Databank for Cardiovascular Diseases. J Card Fail. 2012 Jan. 18(1):74-81. [Medline].
Guarner J, Hochman J, Kurbatova E, Mullins R. Study of outcomes associated with hyponatremia and hypernatremia in children. Pediatr Dev Pathol. 2011 Mar-Apr. 14(2):117-23. [Medline].
Zaki SA, Mondkar J, Shanbag P, Verma R. Hypernatremic dehydration due to lactation failure in an exclusively breastfed neonate. Saudi J Kidney Dis Transpl. 2012 Jan. 23(1):125-8. [Medline].
Arora SK. Hypernatremic Disorders in the Intensive Care Unit. J Intensive Care Med. 2011 May 16. [Medline].
Colletti JE, Brown KM, Sharieff GQ, Barata IA, Ishimine P. The Management of Children with Gastroenteritis and Dehydration in the Emergency Department. J Emerg Med. 2009 Apr 2. [Medline].
Parkin PC, Macarthur C, Khambalia A, Goldman RD, Friedman JN. Clinical and Laboratory Assessment of Dehydration Severity in Children With Acute Gastroenteritis. Clin Pediatr (Phila). 2009 Jun 1. [Medline].
Koster C, Klingelhöfer D, Groneberg DA, Schwarzer M. Rotavirus - Global research density equalizing mapping and gender analysis. Vaccine. 2016 Jan 2. 34 (1):90-100. [Medline].
Cheuvront SN, Kenefick RW, Montain SJ, Sawka MN. Mechanisms of aerobic performance impairment with heat stress and dehydration. J Appl Physiol. 2010 Dec. 109(6):1989-95. [Medline].
[Guideline] Goldman RD, Friedman JN, Parkin PC. Validation of the clinical dehydration scale for children with acute gastroenteritis. Pediatrics. 2008 Sep. 122(3):545-9. [Medline].
Steiner MJ, DeWalt DA, Byerley JS. Is this child dehydrated?. JAMA. 2004 Jun 9. 291(22):2746-54. [Medline].
Steiner MJ, Nager AL, Wang VJ. Urine specific gravity and other urinary indices: inaccurate tests for dehydration. Pediatr Emerg Care. 2007 May. 23(5):298-303. [Medline].
Brandt KG, de Castro Antunes MM, da Silva GA. Acute diarrhea: evidence-based management. J Pediatr (Rio J). 2015 Nov-Dec. 91 (6 Suppl 1):S36-43. [Medline].
Kumar R, Kumar P, Aneja S, Kumar V, Rehan HS. Safety and efficacy of low-osmolarity ORS vs. modified rehydration solution for malnourished children for treatment of children with severe acute malnutrition and diarrhea: a randomized controlled trial. J Trop Pediatr. 2015 Dec. 61 (6):435-41. [Medline].
Atherly-John YC, Cunningham SJ, Crain EF. A randomized trial of oral vs intravenous rehydration in a pediatric emergency department. Arch Pediatr Adolesc Med. 2002 Dec. 156(12):1240-3. [Medline].
Hartling L, Bellemare S, Wiebe N, Russell K, Klassen TP, Craig W. Oral versus intravenous rehydration for treating dehydration due to gastroenteritis in children. Cochrane Database Syst Rev. 2006 Jul 19. 3:CD004390. [Medline].
Danewa AS, Shah D, Batra P, Bhattacharya SK, Gupta P. Oral ondansetron in management of dehydrating diarrhea with vomiting in children aged 3 months to 5 years: a randomized controlled trial. J Pediatr. 2015 Dec 1. [Medline].
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].
Uhlig U, Pfeil N, Gelbrich G, et al. Dimenhydrinate in children with infectious gastroenteritis: a prospective, RCT. Pediatrics. 2009 Oct. 124(4):e622-32. [Medline].
Shanley L, Mittal V, Flores G. Preventing dehydration-related hospitalizations: a mixed-methods study of parents, inpatient attendings, and primary care physicians. Hosp Pediatr. 2013 Jul. 3(3):204-11. [Medline].
Adrogue HJ, Madias NE. Hypernatremia. N Engl J Med. 2000 May 18. 342(20):1493-9. [Medline].
Bellemare S, Hartling L, Wiebe N, et al. Oral rehydration versus intravenous therapy for treating dehydration due to gastroenteritis in children: a meta-analysis of randomised controlled trials. BMC Med. 2004 Apr 15. 2:11. [Medline]. [Full Text].
Bender BJ, Ozuah PO, Crain EF. Oral rehydration therapy: is anyone drinking?. Pediatr Emerg Care. 2007 Sep. 23(9):624-6. [Medline].
Bhatnagar S, Bahl R, Sharma PK, et al. Zinc with oral rehydration therapy reduces stool output and duration of diarrhea in hospitalized children: a randomized controlled trial. J Pediatr Gastroenterol Nutr. 2004 Jan. 38(1):34-40. [Medline].
Choice Study Group. Multicenter, randomized, double-blind clinical trial to evaluate the efficacy and safety of a reduced osmolarity oral rehydration salts solution in children with acute watery diarrhea. Pediatrics. 2001 Apr. 107(4):613-8. [Medline].
Dale J. Oral rehydration solutions in the management of acute gastroenteritis among children. J Pediatr Health Care. 2004 Jul-Aug. 18(4):211-2. [Medline].
Duggan C, Fontaine O, Pierce NF, et al. Scientific rationale for a change in the composition of oral rehydration solution. JAMA. 2004 Jun 2. 291(21):2628-31. [Medline].
Duggan C, Refat M, Hashem M, et al. How valid are clinical signs of dehydration in infants?. J Pediatr Gastroenterol Nutr. 1996 Jan. 22(1):56-61. [Medline].
Duke T, Molyneux EM. Intravenous fluids for seriously ill children: time to reconsider. Lancet. 2003 Oct 18. 362(9392):1320-3. [Medline].
Fonseca BK, Holdgate A, Craig JC. Enteral vs intravenous rehydration therapy for children with gastroenteritis: a meta-analysis of randomized controlled trials. Arch Pediatr Adolesc Med. 2004 May. 158(5):483-90. [Medline].
Gorelick MH, Shaw, KN, Murphy, KO. Validity and reliability of clinical signs in the diagnosis of dehydration in children. Pediatrics. 1997. May;(5):99:E6. [Medline].
Holliday M. The evolution of therapy for dehydration: should deficit therapy still be taught?. Pediatrics. 1996 Aug. 98(2 Pt 1):171-7. [Medline].
Holliday MA, Friedman AL, Segar WE, et al. Acute hospital-induced hyponatremia in children: a physiologic approach. J Pediatr. 2004 Nov. 145(5):584-7. [Medline].
Holliday MA, Friedman AL, Wassner SJ. Extracellular fluid restoration in dehydration: a critique of rapid versus slow. Pediatr Nephrol. 1999 May. (4):292-7. [Medline].
Hoorn EJ, Geary D, Robb M, et al. Acute hyponatremia related to intravenous fluid administration in hospitalized children: an observational study. Pediatrics. 2004 May. 113(5):1279-84. [Medline].
King CK, Glass R, Bresee JS, et al. Managing acute gastroenteritis among children: oral rehydration, maintenance, and nutritional therapy. MMWR Recomm Rep. 2003 Nov 21. 52(RR-16):1-16. [Medline].
Miyasaka K, Shimizu N, Kojima J. Recent trends in pediatric fluid therapy. Methods Find Exp Clin Pharmacol. 2004 May. 26(4):287-94. [Medline].
Moritz ML, Ayus JC. Preventing neurological complications from dysnatremias in children. Pediatr Nephrol. 2005 Dec. 20(12):1687-700. [Medline].
Moritz ML, Ayus JC. Prevention of hospital-acquired hyponatremia: a case for using isotonic saline. Pediatrics. 2003 Feb. 111(2):227-30. [Medline].
Moritz ML, Manole MD, Bogen DL, Ayus JC. Breastfeeding-associated hypernatremia: are we missing the diagnosis?. Pediatrics. 2005 Sep. 116(3):e343-7. [Medline].
Murphy C, Hahn S, Volmink J. Reduced osmolarity oral rehydration solution for treating cholera. Cochrane Database Syst Rev. 2004. CD003754. [Medline].
Nager AL, Wang VJ. Comparison of nasogastric and intravenous methods of rehydration in pediatric patients with acute dehydration. Pediatrics. 2002 Apr. 109(4):566-72. [Medline].
Nalin DR, Hirschhorn N, Greenough W, et al. Clinical concerns about reduced-osmolarity oral rehydration solution. JAMA. 2004 Jun 2. 291(21):2632-5. [Medline].
Ozuah PO, Avner JR, Stein RE. Oral rehydration, emergency physicians, and practice parameters: a national survey. Pediatrics. 2002 Feb. 109(2):259-61. [Medline].
Phin SJ, McCaskill ME, Browne GJ, Lam LT. Clinical pathway using rapid rehydration for children with gastroenteritis. J Paediatr Child Health. 2003 Jul. 39(5):343-8. [Medline].
Playfor SD. Hypotonic intravenous solutions in children. Expert Opin Drug Saf. 2004 Jan. 3(1):67-73. [Medline].
Reid SR, Bonadio WA. Outpatient rapid intravenous rehydration to correct dehydration and resolve vomiting in children with acute gastroenteritis. Ann Emerg Med. 1996 Sep. 28(3):318-23. [Medline].
Santosham M, Keenan EM, Tulloch J, et al. Oral rehydration therapy for diarrhea: an example of reverse transfer of technology. Pediatrics. 1997 Nov. 100(5):E10. [Medline].
Sarnaik AP, Meert K, Hackbarth R, Fleischmann L. Management of hyponatremic seizures in children with hypertonic saline: a safe and effective strategy. Crit Care Med. 1991. Jun;19(6):758-62. [Medline].
Spandorfer PR, Alessandrini EA, Joffe MD, et al. Oral versus intravenous rehydration of moderately dehydrated children: a randomized, controlled trial. Pediatrics. 2005 Feb. 115(2):295-301. [Medline].
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].
|Symptom/Sign||Mild Dehydration||Moderate Dehydration||Severe Dehydration|
|level of consciousness||Alert||Lethargic||Obtunded|
|Capillary refill*||2 s||2-4 s||>4 s, cool limbs|
|Mucous membranes||Normal||Dry||Parched, cracked|
|Heart rate||Slightly increased||Increased||Very increased|
|Respiratory rate/pattern*||Normal||Increased||Increased and hyperpnea|
|Blood pressure||Normal||Normal, but orthostasis||Decreased|
|Pulse||Normal||Thready||Faint or impalpable|
|* Best indicators of hydration status|
|Severity||Infants (weight < 10 kg)||Children (weight >10 kg)|
|Mild dehydration||5% or 50 mL/kg||3% or 30 mL/kg|
|Moderate dehydration||10% or 100 mL/kg||6% or 60 mL/kg|
|Severe dehydration||15% or 150 mL/kg||9% or 90 mL/kg|
|Solution||Carbohydrate (g/dL)||Sodium (mEq/L)||Potassium (mEq/L)||Base (mEq/L)||Osmolality|