Updated: Nov 3, 2009
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.
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.
Diarrheal illnesses in children causes 3 million physician visits, 220,000 hospitalizations (10% of all children who require hospitalization), and 400 deaths per year. 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.
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.
Children younger than 5 years are at the highest risk.
The following should be considered in patients with dehydration:
A complete physical examination may assist in determining the underlying cause of the patient's dehydration and in defining the severity of dehydration. The clinical assessment of severity of dehydration determines the approach to management. In general, physical signs of dehydration have poor precision and accuracy. Rather than attempting to assign an exact percentage of dehydration, one should attempt to place the child in one of 3 broad categories.
The determination of dehydration severity should be based on the overall constellation of symptoms. Patients in a given category need not exhibit all the signs and symptoms listed below. Literature reviews have suggested that delayed capillary refill, delayed skin turgor, and abnormal respiratory pattern are the most reliable clinical signs of dehydration in children. Validated clinical dehydration scales may be a useful adjunct to predict need for intravenous fluid and longer stays in the emergency department.[1 ]
[#table1]
Table 1. Clinical Findings of Dehydration
| 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 |
| Tears | Normal | Decreased | Absent |
| 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 |
| Skin turgor* | Normal | Slow | Tenting |
| Fontanel | Normal | Depressed | Sunken |
| Eyes | Normal | Sunken | Very sunken |
| Urine output | Decreased | Oliguria | Oliguria/anuria |
* Best indicators of hydration status[2 ]
Table 2. Estimated Fluid Deficit
| 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 |
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.
| Acidosis, Metabolic | Hypernatremia |
| Adrenal Insufficiency | Hypochloremic Alkalosis |
| Alkalosis, Metabolic | Hypoglycemia |
| Bowel Obstruction in the Newborn | Hypokalemia |
| Burns, Thermal | Hyponatremia |
| Congenital Adrenal Hyperplasia | Intestinal Malrotation |
| Dehydration | Intestinal Volvulus |
| Diabetes Insipidus | Intussusception |
| Diabetic Ketoacidosis | Neonatal Sepsis |
| Diarrhea | Oliguria |
| Eating Disorder: Anorexia | Pyloric Stenosis, Hypertrophic |
| Enteroviral Infections | Shock |
| Fluid, Electrolyte, and Nutrition Management of
the Newborn | Shock and Hypotension in the Newborn |
| Gastroenteritis | Small-Bowel Obstruction |
| Hyperkalemia |
No definitive laboratory test for dehydration is available. Laboratory data are generally not required if the etiology is apparent and mild-to-moderate dehydration is present.
With severe dehydration, the following laboratory studies are suggested:
Medications such as loperamide, opiates, anticholinergics, bismuth subsalicylate, and adsorbents are not recommended in dehydration because of questionable efficacy and potential adverse effects.
Oral rehydration solutions
During gastroenteritis, the intestinal mucosa retains absorptive capacity. Sodium and glucose in the correct proportions can be passively cotransported with fluid from the gut lumen into the circulation. Rapid oral rehydration with the appropriate solution has been shown to be as effective as intravenous fluid therapy in restoring intravascular volume and correcting acidosis.
Table 3. Composition of Appropriate Oral Rehydration Solutions
| Solution | Carbohydrate (g/dL) | Sodium (mEq/L) | Potassium (mEq/L) | Base (mEq/L) | Osmolality |
|---|---|---|---|---|---|
| Pedialyte | 2.5 | 45 | 20 | 30 | 250 |
| Infalyte | 3 | 50 | 25 | 30 | 200 |
| Rehydralyte | 2.5 | 75 | 20 | 30 | 310 |
| WHO/UNICEF* | 2 | 90 | 20 | 30 | 310 |
* World Health Organization/United Nations Children's Fund
All of the commercially available rehydration fluids are acceptable for oral rehydration therapy (ORT). They contain 2-3 g/dL of glucose, 45-90 mEq/L of sodium, 30 mEq/L of base, and 20-25 mEq/L of potassium. Osmolality is 200-310 mOsm/L.
Table 4. Composition of Inappropriate Oral Rehydration Solutions
| Solution | Carbohydrate (g/dL) | Sodium (mEq/L) | Potassium (mEq/L) | Base (mEq/L) | Osmolality |
|---|---|---|---|---|---|
| Apple juice | 12 | 0.4 | 26 | 0 | 700 |
| Ginger ale | 9 | 3.5 | 0.1 | 3.6 | 565 |
| Milk | 4.9 | 22 | 36 | 30 | 260 |
| Chicken broth | 0 | 2 | 3 | 3 | 330 |
Traditional clear fluids are not appropriate for ORT. Many contain excessive concentrations of CHO and low concentrations of sodium. The inappropriate glucose-to-sodium ratio impairs water absorption, and the large osmotic load creates an osmotic diarrhea, further worsening the degree of dehydration.
In a recent emergency department study, ondansetron was shown to decrease likelihood of vomiting, increase oral intake, and decrease emergency department length of stay.[8 ]
Selective 5-HT3-receptor antagonist that blocks serotonin both peripherally and centrally. Prevents nausea and vomiting associated with emetogenic cancer chemotherapy (eg, high-dose cisplatin), and complete body radiotherapy.
8 mg PO q1-2h for 3 doses
Alternatively, 0.15 mg/kg IV q8h for 3 doses or 32 mg IV once
Orally dissolving tablets:
8-15 kg: 2 mg as a single dose
15-30 kg: 4 mg as a single dose
>30 kg: 8 mg as a single dose
Although there is potential for cytochrome P-450 inducers (eg, barbiturates, rifampin, carbamazepine, phenytoin) to change half-life and clearance of ondansetron, dosage adjustment is not usually required
Documented hypersensitivity
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
May cause headache
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dehydration, negative fluid balance, diarrheal illness, diarrhea, isonatremic dehydration, hypernatremic dehydration, hyponatremic dehydration, end organ failure, cerebral edema, gastroenteritis, cystic fibrosis, diabetes mellitus, treatment, diagnosis
Lennox H Huang, MD, Associate Chair (Clinical), Assistant Professor, Department of Pediatrics, McMaster University School of Medicine; Interim Chief of Pediatrics, McMaster Children's Hospital
Lennox H Huang, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Physician Executives, Canadian Medical Association, Ontario Medical Association, and Society of Critical Care Medicine
Disclosure: Nothing to disclose.
Krishnapriya R Anchala, MD, MS, FAAP, Assistant Professor, Department of Pediatrics, Division of Pediatric Emergency Medicine, McMaster University
Krishnapriya R Anchala, MD, MS, FAAP is a member of the following medical societies: American Academy of Pediatrics, Canadian Medical Association, and Ontario Medical Association
Disclosure: Nothing to disclose.
Dan L Ellsbury, MD, Consulting Staff, Pediatrix Medical Group of Iowa; Consulting Staff, Department of Pediatrics, Neonatology Intensive Care Unit, Mercy Medical Center of Des Moines
Dan L Ellsbury, MD is a member of the following medical societies: American Academy of Pediatrics
Disclosure: Nothing to disclose.
Caroline S George, MD, Associate Professor, Consulting Staff, Department of Pediatrics, Division of Critical Care Medicine, University of Minnesota Medical School
Caroline S George, MD is a member of the following medical societies: American Academy of Pediatrics and Society of Critical Care Medicine
Disclosure: Nothing to disclose.
G Patricia Cantwell, MD, Associate Clinical Professor, Department of Pediatrics, University of Miami; Director of Pediatric Critical Care Medicine, Miller School of Medicine, Jackson Children's Hospital
G Patricia Cantwell, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Emergency Physicians, American Heart Association, American Trauma Society, National Association of EMS Physicians, Society of Critical Care Medicine, and Wilderness Medical Society
Disclosure: Nothing to disclose.
Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner
Barry J Evans, MD, Assistant Professor of Pediatrics, Temple University Medical School; Director of Pediatric Critical Care and Pulmonology, Associate Chair for Pediatric Education, Temple University Children's Medical Center
Barry J Evans, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Chest Physicians, American Thoracic Society, and Society of Critical Care Medicine
Disclosure: Nothing to disclose.
Mary E Cataletto, MD, Associate Director, Division of Pediatric Pulmonology, Winthrop University Hospital; Professor of Clinical Pediatrics, State University of New York at Stony Brook; Director of Children's Sleep Services, Winthrop University Hospital
Mary E Cataletto, MD is a member of the following medical societies: American Academy of Pediatrics and American College of Chest Physicians
Disclosure: Shering Plough Pharmaceuticals Honoraria Consulting
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, and Wisconsin Medical Society
Disclosure: Nothing to disclose.
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