Dehydration (hypovolemia) is a decrease in total body water, both intracellular and extracellular.
Dehydration in children worldwide is primarily caused by diarrhea:
- Diarrhea accounts for 1 of 9 deaths in children worldwide.
- 300 children/year die from diarrhea in the United States.
- Most diarrhea is infectious:
- Viral (75%–90%): rotavirus, norovirus, and enteroviruses
- Bacterial (< 20%): Salmonella, Shigella, and Escherichia coli (10% of bacterial)
- Parasitic (< 5%): Giardia and cryptosporidium
- Excessive water loss
- Urinary: excessive urination from hyperosmolar states (e.g., diabetes)
- Increased insensitive loss from evaporation:
- Febrile illnesses
- Increased respiratory loss with respiratory illness (e.g., bronchiolitis)
- Decreased intake
- Anorexia from illness
- Lack of access to clean water
In most cases, a good history and physical exam are sufficient to diagnose dehydration and its etiology. Laboratory testing is reserved for severe cases and to monitor rehydration.
- Fluid balance:
- Number of wet diapers/urination per day
- Increased drinking or asking for water
- Recent illness:
- Diarrheal episodes (quantity and quality of stool loss can be estimated)
- Behavioral changes:
|Weight loss||< 5% in infants, < 3% in older children||5%–10% in infants, 3%–9% in older children||< 10% in infants, < 9% in older children|
|Dry mucosas (first sign)||–||+/-, looks dry||+, looks parched|
|Skin turgor (last sign)||+||+/-||-, tenting|
|Anterior fontanelle depression||–||+||+/++|
|Breathing||Normal||Deep, may be tachypneic||Deep and tachypneic|
|Heart rate||Normal||Increased||Very high|
|Distal perfusion||Normal||Feels cold, 3–4 seconds||Acrocyanotic, > 4 seconds|
- Basic metabolic panel (CHEM-7) in cases of severe dehydration can show:
- ↓ glucose
- ↑ blood urea nitrogen (BUN)
- ↑ sodium and chloride
- ↓ bicarbonate
- ↑ creatinine
- Creatinine kinase (CK):
- When concerned about rhabdomyolysis
- Elevated in severe dehydration
- Stool studies: to identify etiology in cases of prolonged diarrhea
- 1st-line therapy: oral rehydration therapy (ORT)
- Oral rehydration solutions with similar electrolyte contents to fluid lost should be used:
- Pedialyte or enfalyte
- Breastfed infants should continue to nurse.
- Fluids with high sugar content should be avoided as they may worsen diarrhea.
- Goal is to provide 50–100 cc/kg of fluids over 2–4 hours. Route of administration depends on patient age and frailty:
- Syringe or spoon-feeding
- Nasogastric (NG) tube
- +/- ondansetron to prevent vomiting
- Clinical hydration status should be monitored frequently.
- Failure to improve with ORT should prompt intravenous hydration.
Severe dehydration can cause hypoperfusion of the brain and vital organs and is considered a medical emergency to be addressed rapidly.
- Acute resuscitation phase
- Goal: correct or prevent hypovolemic shock
- Rapid volume expansion through fluid boluses:
- 20 cc/kg given over 20 minutes
- Can be repeated up to 3x
- Monitor vital signs between each bolus.
- Choice of replacement fluid:
- Isotonic fluids only
- Lactated Ringer’s or normal saline are appropriate.
- Glucose monitoring:
- Point of care (POC) monitoring for hypoglycemia
- IV glucose should be administered.
- 5–10 ml/kg of D10 NS OR 2-4ml/kg of D25 NS
- Resuscitation phase
- Slower replacement of lost fluids over 24 hours
- Total fluid of resuscitation phase = maintenance fluids + (rehydration – bolus already given)
- Rehydration is divided in 2 phases:
- 50% over the first 8 hours
- 50% over the next 16 hours
- 5% dextrose with 0.2% sodium chloride compensates for maintenance requirement of sodium in most children
- After 24 hours if clinically stable → continue maintenance fluids
- Standard bolus:
- 20 cc/kg/20 min
- Up to 3x
- Monitor vital signs.
- Maintenance calculations:
- 4-2-1 rule:
- 1st 10 kg = 4 cc/kg/hr
- 2nd 10 kg = 2 cc/kg/hr
- Further kg = 1 cc/kg/hr
- Example: a child who weighs 37 kg
- (10 kg x 4 cc/kg/hr) + (10 kg x 2 cc/kg/hr) + (17 kg x 1 cc/kg/hr) = (40 cc/hr) + (20 cc/hr) + (17 cc/hr) = 77 cc/hr
- 4-2-1 rule:
- Rehydration is calculated by weight and severity of dehydration:
- Amount calculated is added to the maintenance amount, spread throughout the day.
- < 10 kg:
- Mild: 50 cc/kg/day
- Moderate: 100 cc/kg/day
- Severe: 150 cc/kg/day
- > 10 kg:
- Mild: 30 cc/kg/day
- Moderate: 60 cc/kg/day
- Severe: 90 cc/kg/day
Complete management example
A child who weighs 25 kg with severe dehydration:
- Acute resuscitation phase:
- 3 x 20 cc/kg boluses = 1,500 cc
- Resuscitation phase:
- Total fluid = maintenance fluids + (rehydration – bolus already given)
- Maintenance: (10 kg x 4 cc/kg/hr) + (10 kg x 2 cc/kg/hr) + (5 kg x 1 cc/kg/hr) = 65 cc/hr → 1,560 cc/day
- Rehydration: 25 kg x 90 cc/kg/day = 2,250 cc/day
- Rehydration – bolus already given: 2,250 cc/day – 1,500 cc = 750 cc/day
- Total fluid replacement: 1,560 cc/day + 750 cc/day = 2,310 cc/day
- Rehydration divided into 2 phases of treatment: 2,310 cc / 2 = 1,155 cc
- Volume for first 8 hours: 1,155 cc/8 hr
- Volume for next 16 hours: 1,155 cc/16 hr
- After 24 hours → continue maintenance fluids
- Urine output: optimal > 1 cc/kg/hr
- Clinical improvement of signs of dehydration:
- Increased skin turgor
- Improved pulse
- Improved capillary refill
- Improved mental status
- Resolution of enophthalmos
Special Populations (Infants)
Daily requirements = maintenance fluids + growth fluids:
- Term infants:
- Day 1 = 80 cc/kg/day (maintenance fluids)
- Daily increase by increment of 20 cc/kg/day (growth fluids) until goal reached
- Preterm infants:
- Day 1 = 70 cc/kg/day
- Daily increase by increment of 10 cc/kg/day (growth fluids)
- Premature babies take longer to reach goal.
- The quantity fed is progressively increased every day until a daily input above 150 cc/kg/day is met.
- Term infants: by days 5–7
- Preterm infants: by days 14–21
- Growth fluids should ensure a daily weight increase of 30–40 g.
- Daily output should be more than input.
- CDC. (2015). Diarrhea: Common Illness, Global Killer. https://www.cdc.gov/healthywater/global/diarrhea-burden.html
- Managing Acute Gastroenteritis Among Children Oral Rehydration, Maintenance, and Nutritional Therapy. Prepared by Caleb K. King, M.D., Roger Glass, M.D., Ph.D., Joseph S. Bresee, M.D., Christopher Duggan, M.D., University of North Carolina, Chapel Hill, North Carolina Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC, Children’s Hospital Bostom, Boston, Massachusetts https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5216a1.htm