Introduction to Pediatric Fluid Deficit Therapy

Fluid deficit therapy, also known as dehydration therapy, is a critical aspect of pediatric care. Dehydration in children can occur due to various causes, including gastroenteritis, fever, reduced intake, and increased losses. Understanding the principles of fluid management in pediatric patients is essential for effective treatment and prevention of complications.

Key Points:

• Dehydration is more common and can progress more rapidly in children compared to adults.
• The goal of fluid deficit therapy is to restore intravascular volume, correct electrolyte imbalances, and maintain ongoing fluid requirements.
• Accurate assessment, careful calculation, and close monitoring are crucial for successful management.

Assessment of Dehydration in Pediatric Patients

Accurate assessment of dehydration severity is crucial for determining the appropriate treatment approach.

Clinical Signs and Symptoms:

Mild Dehydration (3-5%)	Moderate Dehydration (6-9%)	Severe Dehydration (≥10%)
Thirst Dry mucous membranes Decreased urine output	Tachycardia Decreased skin turgor Sunken eyes Decreased tears	Altered mental status Weak or absent peripheral pulses Delayed capillary refill (>2 seconds) Cool, mottled extremities

Laboratory Evaluation:

• Serum electrolytes (Na+, K+, Cl-, HCO3-)
• Blood urea nitrogen (BUN) and creatinine
• Serum glucose
• Urinalysis and urine specific gravity

Severity	Mild Dehydration	Moderate Dehydration	Severe Dehydration
Degree	<5% in an infant; <3% in an older child or adult	5–10% in an infant; 3–6% in an older child or adult	>10% in an infant; >6% in an older child or adult
Clinical Signs	Normal or increased pulse Decreased urine output Thirsty Normal physical findings	Tachycardia Little or no urine output Irritable/lethargic Sunken eyes and fontanel Decreased tears Dry mucous membranes Mild delay in elasticity (skin turgor) Delayed capillary refill (>1.5 sec) Cool and pale	Peripheral pulses either rapid and weak or absent Decreased blood pressure No urine output Very sunken eyes and fontanel No tears Parched mucous membranes Delayed elasticity (poor skin turgor) Very delayed capillary refill (>3 sec) Cold and mottled Limp, depressed consciousness

Calculation of Fluid Deficit

Accurate calculation of fluid deficit is essential for appropriate rehydration therapy.

Formula:

Fluid Deficit = Percentage of dehydration × Weight (kg) × 10

For example, a 10 kg child with 5% dehydration has a fluid deficit of:

5% × 10 kg × 10 = 500 mL

Additional Considerations:

• Ongoing losses should be estimated and added to the calculated deficit.
• Maintenance fluids should be provided in addition to deficit replacement.
• The rate of rehydration depends on the severity of dehydration and the clinical status of the patient.

Types of Fluid Therapy

1. Oral Rehydration Therapy (ORT)

Preferred method for mild to moderate dehydration when tolerated.

• Use WHO-recommended Oral Rehydration Solution (ORS)
• Administer small, frequent volumes (e.g., 5 mL every 5 minutes)
• Gradually increase volume as tolerated

2. Intravenous Fluid Therapy

Indicated for severe dehydration or when ORT is not tolerated.

Rapid Fluid Bolus:

• 20 mL/kg of isotonic crystalloid (e.g., 0.9% NaCl) over 15-20 minutes
• Repeat as needed based on clinical response

Deficit Replacement:

• Replace 50% of the deficit in the first 8 hours
• Replace the remaining 50% over the next 16 hours

Maintenance Fluids:

Use the Holliday-Segar method:

• 100 mL/kg for the first 10 kg
• 50 mL/kg for the next 10 kg
• 20 mL/kg for each kg above 20 kg

Monitoring and Adjustment of Fluid Therapy

Close monitoring is essential to ensure effective rehydration and prevent complications.

Clinical Monitoring:

• Vital signs (heart rate, blood pressure, respiratory rate)
• Mental status
• Urine output (goal: >1 mL/kg/hour)
• Skin turgor and mucous membrane moisture
• Body weight (daily or more frequently if needed)

Laboratory Monitoring:

• Serum electrolytes
• Blood glucose
• Acid-base status

Adjustment of Therapy:

• Reassess fluid status every 2-4 hours
• Adjust fluid rate and composition based on clinical and laboratory parameters
• Transition to oral rehydration as soon as clinically appropriate

Complications and Special Considerations

Potential Complications:

• Cerebral edema (rapid correction of hypernatremia)
• Fluid overload
• Electrolyte imbalances (hyponatremia, hypernatremia, hypokalemia)
• Hypoglycemia or hyperglycemia

Special Considerations:

1. Hypernatremic Dehydration:

• Correct sodium at a rate not exceeding 0.5 mEq/L/hour
• Use hypotonic fluids cautiously
• Extend rehydration over 48-72 hours

2. Hyponatremic Dehydration:

• Use isotonic fluids for initial resuscitation
• Monitor for signs of cerebral edema

3. Diabetic Ketoacidosis (DKA):

• Follow specific DKA protocols
• Avoid rapid fluid administration due to risk of cerebral edema

Prevention Strategies:

• Early recognition and treatment of dehydration
• Patient and caregiver education on oral rehydration techniques
• Encourage appropriate fluid intake during illness

Isonatremic Dehydration in Children

Isonatremic dehydration is characterized by proportional loss of water and sodium, resulting in normal serum sodium levels (135-145 mEq/L).

Key Features:

• Most common type of dehydration in children
• Typically caused by gastroenteritis or other acute illnesses
• Serum sodium remains within normal range despite fluid losses

Management Principles:

1. Fluid Choice: Isotonic fluids (e.g., 0.9% NaCl or Ringer's lactate) are appropriate for both initial bolus and ongoing replacement.
2. Rehydration Rate:
   • Mild to moderate dehydration: Replace deficit over 24 hours
   • Severe dehydration: Initial rapid bolus followed by deficit replacement over 24 hours
3. Electrolyte Management: Monitor serum electrolytes and adjust fluid composition as needed
4. Transition to Oral Rehydration: Initiate oral rehydration as soon as the patient can tolerate it

Monitoring:

• Clinical signs of hydration status
• Urine output
• Serum electrolytes and renal function tests
• Body weight

Hypernatremic Dehydration in Children

Hypernatremic dehydration is defined as dehydration with serum sodium > 145 mEq/L. It requires careful management to avoid complications.

Etiology:

• Excessive water loss (e.g., diabetes insipidus, inadequate breast milk intake)
• Excessive sodium intake (e.g., improperly prepared formula)
• Osmotic diarrhea

Management Principles:

1. Gradual Correction: Aim to reduce serum sodium by no more than 0.5 mEq/L/hour or 10-12 mEq/L/day
2. Fluid Choice: Start with isotonic fluids (0.9% NaCl) and adjust based on serum sodium levels
3. Rehydration Duration: Extend rehydration over 48-72 hours to avoid rapid shifts in osmolality
4. Calculation: Use the Adrogué-Madias formula to guide fluid therapy:

   Change in serum [Na+] = (Infusate [Na+] - Serum [Na+]) / (Total body water + 1)

Monitoring:

• Frequent serum electrolyte measurements (every 2-4 hours initially)
• Neurological status for signs of cerebral edema
• Urine output and specific gravity
• Blood glucose levels

Complications to Watch For:

• Cerebral edema from overly rapid correction
• Seizures
• Intracranial hemorrhage

Treatment of Hypernatremic Dehydration

1. Restore Intravascular Volume:

• Normal saline: 20 mL/kg over 20 min (repeat until intravascular volume restored)

2. Determine Correction Time:

• [Na] 145-157 mEq/L: 24 hr
• [Na] 158-170 mEq/L: 48 hr
• [Na] 171-183 mEq/L: 72 hr
• [Na] 184-196 mEq/L: 84 hr

3. Administer Fluid:

• Typical fluid: 5% dextrose + half-normal saline (with 20 mEq/L KCl unless contraindicated)
• Typical rate: 1.25-1.5 times maintenance
• Administer at constant rate over time for correction

4. Monitor and Adjust:

• Follow serum sodium concentration
• Adjust fluid based on clinical status and serum sodium concentration:
• Signs of volume depletion: administer normal saline (20 mL/kg)
• Sodium decreases too rapidly:
  • Increase sodium concentration of IV fluid, or
  • Decrease rate of IV fluid
• Sodium decreases too slowly:
  • Decrease sodium concentration of IV fluid, or
  • Increase rate of IV fluid

5. Ongoing Management:

• Replace ongoing losses as they occur

Hyponatremic Dehydration in Children

Hyponatremic dehydration is characterized by serum sodium < 135 mEq/L. It requires careful management to avoid neurological complications.

Etiology:

• Excessive loss of sodium (e.g., certain types of diarrhea)
• Syndrome of Inappropriate ADH Secretion (SIADH)
• Excessive administration of hypotonic fluids

Management Principles:

1. Initial Stabilization: Use isotonic fluids (0.9% NaCl) for initial volume resuscitation
2. Correction Rate:
   • Asymptomatic: Correct by 6-8 mEq/L/day
   • Symptomatic (e.g., seizures): Rapid partial correction with 3% NaCl bolus (2-5 mL/kg) over 10-15 minutes
3. Ongoing Fluid Therapy: Use isotonic fluids until serum sodium normalizes
4. Electrolyte Management: Monitor and replace other electrolytes as needed (e.g., potassium, calcium)

Monitoring:

• Serum electrolytes every 2-4 hours initially
• Neurological status
• Urine output and electrolytes
• Signs of fluid overload

Complications to Watch For:

• Cerebral edema
• Osmotic demyelination syndrome (from overly rapid correction)
• Seizures

Special Scenarios in Pediatric Fluid Management

1. Burn Injuries:

• Use modified Parkland formula for fluid resuscitation
• Monitor for compartment syndrome and need for escharotomy
• Adjust fluid therapy based on urine output and hemodynamic parameters

2. Diabetic Ketoacidosis (DKA):

• Initial fluid bolus: 10-20 mL/kg of isotonic saline
• Subsequent fluid: 1.5-2 times maintenance rate
• Add potassium early in treatment
• Gradual correction of hyperglycemia to avoid cerebral edema

3. Nephrotic Syndrome:

• Cautious use of diuretics
• Albumin infusion may be necessary
• Monitor for thromboembolic complications

4. Heart Failure:

• Restrict fluid intake to 50-75% of normal maintenance
• Use diuretics judiciously
• Monitor for signs of fluid overload and electrolyte imbalances

5. Traumatic Brain Injury:

• Maintain euvolemia
• Avoid hypotonic fluids
• Monitor for and treat diabetes insipidus or SIADH

6. Post-operative Fluid Management:

• Consider enhanced recovery after surgery (ERAS) protocols
• Early transition to oral intake when appropriate
• Monitor for third-space fluid losses

Fluid Management of Dehydration

1. Restore Intravascular Volume:

• Isotonic fluid (NS or LR): 20 mL/kg over 20 min
• Repeat as needed

2. Calculate 24-hour Fluid Needs:

• Total = Maintenance + Deficit volume

3. Adjust for Already Administered Fluids:

• Subtract isotonic fluid already administered from 24 hr fluid needs

4. Administer Remaining Volume:

• Over 24 hr using 5% dextrose NS + 20 mEq/L KCl

5. Ongoing Management:

• Replace ongoing losses as they occur

Note: LR = Ringer's lactate; NS = normal saline.