Fluid Replacement Therapy in Children

Overview

Definition

Dehydration (hypovolemia) is a decrease in total body water, both intracellular and extracellular.

Epidemiology

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

Etiology

• Excessive water loss
  • Gastrointestinal: 
    • Diarrhea
    • Vomiting
  • Urinary: excessive urination from hyperosmolar states (e.g., diabetes)
  • Increased insensitive loss from evaporation:
    • Febrile illnesses
    • Burns
    • Increased respiratory loss with respiratory illness (e.g., bronchiolitis)
• Decreased intake
  • Anorexia from illness
  • Lack of access to clean water 
  • Neglect

Diagnosis

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.

History

• Fluid balance:
  • Number of wet diapers/urination per day
  • Increased drinking or asking for water 
• Recent illness:
  • Fever
  • Diarrheal episodes (quantity and quality of stool loss can be estimated)
• Behavioral changes:
  • Lethargy 
  • Irritability

Physical exam

Laboratory testing

• 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

Management

Mild-to-moderate dehydration

• 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

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

Volume-replacement calculations

• 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
• 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

Monitor response

• 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.