Dehydration
Dehydration: Excerpt from The 5-Minute Pediatric Consult
Marc H. Gorelick, MD, MSCE
Dehydration - BASICS
Dehydration - description
- Dehydration is a negative balance of body fluid, usually expressed as a percentage of body weight. Mild, moderate, and severe dehydration correspond to deficits of <5%, 5–10%, and >10%, respectively.
- Dehydration is classified into 3 types based on the serum sodium concentration: Isotonic (Na 130–150 mmol/L), hypotonic (Na <130 mmol/L), and hypertonic (Na >150 mmol/L)
Dehydration - general prevention
Many cases of frank dehydration may be prevented by early institution of adequate oral maintenance fluid therapy in children with gastroenteritis, with particular attention to replacement of ongoing stool losses and slow administration of fluids to children with vomiting. Use of appropriate solutions is essential to prevent electrolyte disturbance and worsening of diarrhea.
Dehydration - incidence
- ~10% of children in the US with acute gastroenteritis develop at least mild dehydration.
- Although it accounts for 10% of all nonsurgical hospital admissions for children under 5 years of age, up to 90% of cases can be managed on an outpatient basis.
Dehydration - pathophysiology
- Dehydration is caused by either excessive fluid losses or inadequate intake of fluids.
- Some conditions leading to dehydration include:
- GI losses: Vomiting, diarrhea (most common cause of dehydration in pediatric patients)
- Renal losses: Diabetes mellitus, diabetes insipidus, diuretic agents
- Insensible losses: Sweating, fever, tachypnea, increased ambient temperature, large burns
- Poor oral intake: Stomatitis, pharyngitis, anorexia, oral trauma, altered mental status
- Note that infants and debilitated patients are at particular risk due to lack of ability to satisfy their thirst freely.
Dehydration - DIAGNOSIS
Dehydration - signs & symptoms
Dehydration - history
- Frequency and duration of emesis and/or diarrhea will give a rough estimate of risk of dehydration.
- If there were large quantities of water taken, be alert for hypotonic dehydration. If excessive electrolyte solution used for hydration, may have hypertonic dehydration
- Frequency and quantity of urination may be difficult to estimate in infants with diarrhea. Decreased urination indicates possibility of dehydration.
- Fever increases insensible water loss.
- Exertion or heat exposure increases insensible water loss.
Dehydration - physical exam
- Acute change in weight is the best indicator of fluid deficit. If the child’s recent preillness weight is not available for comparison, a reasonable estimate of the degree of dehydration may be made from physical findings.
- General appearance: Lethargy, irritability, thirst
- Vital signs: Tachycardia; orthostatic increase in heart rate or hypotension; hyperpnea
- Skin: Prolonged capillary refill at fingertip (<2 sec is normal in warm environment); mottling; poor turgor
- Eyes: Decreased or absent tears; sunken eyes
- Mucous membranes: Dry or parched
- Anterior fontanelle: Sunken
Diagnostic pitfalls:
- Physical signs generally appear when the deficit is at least 2–3%.
- No single finding is pathognomonic of dehydration. A reasonable guideline is that the presence of 3 or more findings indicates at least mild dehydration. The number and severity of physical signs increase with the degree of dehydration.
- Urine output decreases early in the course of dehydration, and a history of decreased urination is a sensitive but nonspecific finding.
- Capillary refill time is a specific but insensitive indicator. It may be falsely prolonged by cool ambient temperature (<20°C [<68°F]). It is not affected by fever.
- Children with a deficit >15% will show signs of cardiovascular instability such as severe tachycardia and hypotension.
- Physical findings may be more significant for a given degree of dehydration in children with hyponatremia, leading to overestimation of the deficit. Conversely, the clinical picture is reported to be somewhat moderated in hypernatremia.
Dehydration - tests
Dehydration - lab
- Diagnosis of dehydration is best made on clinical grounds. The following laboratory tests are sometimes helpful adjuncts.
- Serum sodium:
- Classifies type of dehydration
- Hyponatremia and hypernatremia are uncommon in dehydration due to gastroenteritis (<5% of cases).
- Measure sodium levels in cases of clinically severe disease, or if risk factors are present (e.g., young infant, history of excessive free water intake, children with significant neurologic impairment limiting their ability to regulate their own intake).
- Rapid glucose test or serum glucose: To detect hypoglycemia due to prolonged fasting
- Urine specific gravity: This is elevated early in dehydration, but may not become elevated at all in young infants or in children with sickle cell disease.
- Serum bicarbonate: This is frequently low with diarrheal illness, even in the absence of dehydration. Useful to detect significant acidosis when dehydration is clinically severe
- Blood urea nitrogen (BUN): May rise late in dehydration in children
Dehydration - TREATMENT
Dehydration - general measures
Oral rehydration therapy (ORT):
- Most children can be managed successfully with oral rehydration therapy, either at home or in a health care setting.
- Use rehydration solution containing 2.0–2.5% glucose and 75 mmol/L Na (e.g., WHO solution), or 45–50 mmol/L Na (e.g., Pedialyte [Ross Laboratories, Columbus, OH], Infalyte [Mead Johnson, Evansville, IN]).
- Replace entire deficit in 4–6 hours: For mild dehydration, 50 mL/kg; for moderate to severe dehydration, 80–100 mL/kg. Include ongoing losses, ~5 mL/kg for each diarrheal stool.
- Begin with slow administration, with strict limits when vomiting is present: 5 mL q1–2min. For infants, use a syringe or spoon rather than a bottle. After 1 hour, if the oral liquids have been tolerated, increase the volume and rate.
- Have the child’s caregiver participate in giving the fluids, and provide education regarding fluid replacement and signs of dehydration.
- Monitor weight, intake and output, and clinical signs. Failure of oral rehydration therapy includes intractable vomiting, clinical deterioration, or lack of improvement after 4 hours.
Dehydration - iv fluids
- IV fluids are required when ORT fails or is contraindicated, such as in severe dehydration or shock, poor gag or suck, depressed mental status, preterm infant, severe hypernatremia (Na >160 mmol/L), suspected surgical abdomen.
- Administer IV bolus of normal saline or Ringer lactate, 20 mL/kg, over 10–30 minutes. Repeat as needed to restore cardiovascular stability. Avoid dextrose-containing solutions for boluses except to correct documented hypoglycemia.
- Calculate maintenance fluid requirements: 100 mL/kg for the 1st 10 kg, plus 50 mL/kg for the next 10 kg, plus 20 mL/kg over 20 kg.
- Calculate fluid deficit based on clinical estimate or known weight loss. For isotonic or hypotonic dehydration, give 1/3–1/2 normal saline with 5% dextrose, at a rate to provide maintenance and replace deficit over 24 hours. For hypertonic dehydration, replace deficit over 48 hours, using 1/5–1/4 normal saline with 5% dextrose.
- Monitor weight, intake and output, and clinical signs. With hypernatremia, measure serum sodium q4–6h; do not exceed rate of fall of 1 mmol/L/h.
- For mild to moderate isonatremic dehydration, rapid replacement of deficit over 2–6 hours may be possible. Give normal saline at a rate to replace the estimated deficit at a rate of 25–50 cc/kg/h.
Dehydration - medication
Dehydration - first line
Most children with dehydration do not require specific medication therapy. For children with significant vomiting, several studies suggest that ondansetron 0.15 mg/kg PO decreases vomiting and facilitates oral rehydration.
Dehydration - FOLLOW UP
Dehydration - disposition
Dehydration - admission criteria
- Failure of oral or IV rehydration within 4 hours
- Severe hypernatremia
- Substantial ongoing losses suggesting a high likelihood of recurrence of dehydration
Dehydration - discharge criteria
After initiating ORT, children who are tolerating oral fluids at an acceptable rate to replace their deficit over 4–6 hours may be discharged with a willing and reliable caregiver and complete the ORT at home.
Dehydration - prognosis
Excellent with appropriate rehydration therapy
Dehydration - complications
- Severe dehydration may lead to hypovolemic shock and acute renal failure.
- Hyponatremia is associated with hypotonia, hypothermia, and seizures.
- Overly rapid correction of hypernatremia can produce cerebral edema.
Dehydration - patient monitoring
- After rehydration, children with ongoing losses, as in gastroenteritis, should receive a maintenance solution in addition to regular feedings to maintain a positive fluid balance.
- Recommend 5–10 mL/kg for each diarrheal stool. Avoid clear liquids with excessive glucose, such as fruit juices, punches, and soft drinks, as these can promote osmotic fluid losses in the stool.
- In infants <6 months old, do not give large amounts of plain water, which can lead to hyponatremia.
Dehydration - bibliography
- Armon K, Stephenson T, MacFaul R, et al. An evidence and consensus based guideline for acute diarrhea management. Arch Dis Child. 2001;85(2):132–142.
- Centers for Disease Control and Prevention. Managing acute gastroenteritis among children: Oral rehydration, maintenance, and nutritional therapy. MMWR. 2003;52 (No. RR-16).
Dehydration - CODES
Dehydration - icd9
276.51 Dehydration
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Book Source Details
- Book Title: The 5-Minute Pediatric Consult
- Author(s): M. William Schwartz MD; et al.
- Year of Publication: 2008
- Copyright Details: The 5-Minute Pediatric Consult, Copyright © 2008 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: The 5-Minute Pediatric Consult
Authors: M. William Schwartz MD; et al.
Publisher: Lippincott Williams & Wilkins
Copyright: 2008
ISBN: 0-7817-7577-9
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