Fluid and Electrolyte Balance in Pediatric Surgery

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Questions and Answers

What is the primary reason why managing fluid and electrolyte balance is critical in pediatric surgical patients?

To prevent respiratory distress

To prevent electrolyte imbalance

Due to the small margin between dehydration and fluid overload (correct)

To prevent cardiac failure

Why are infants more prone to fluid overload or dehydration?

Due to their larger total body water

Because of their physiologic day duration

Due to their ability to regulate their fluid balance

Due to their little reserve at baseline, which decreases when they are ill (correct)

What type of surgical diagnoses are characterized by a predisposition to fluid loss?

Congenital diaphragmatic hernia

Respiratory distress

Cardiac failure

Gastroschisis or short-gut syndrome (correct)

What is the duration of an infant's physiologic day?

8 hours Signup and view all the answers

What is a common clinical sign of dehydration in pediatric patients?

Decreased urine output Signup and view all the answers

What is the approximate total body water of a fetus at 12 weeks' gestation?

94 cc/kg Signup and view all the answers

What happens to total body water within the first week of life?

It decreases by 5% Signup and view all the answers

What is the approximate total body water of an adult?

60-65 cc/kg Signup and view all the answers

What is the estimated daily fluid requirement for a newborn infant with gastroschisis?

150 to 180 mL/kg/day Signup and view all the answers

What is the glomerular filtration rate (GFR) of a term newborn?

21 mL/min/1.73 m2 Signup and view all the answers

What is the maximum urine concentration that a preterm infant can achieve?

600 mOsm/kg Signup and view all the answers

What is the sodium requirement for critically ill preterm infants?

5 mEq/kg per day Signup and view all the answers

What is the fluid requirement for a 26-kg child?

66 mL/h Signup and view all the answers

At what age does the glomerular filtration rate (GFR) reach adult levels?

2 years Signup and view all the answers

What is the limitation in the infant's collecting tubules that leads to insensitivity to antidiuretic hormone (ADH)?

Severely limited osmotic water permeability Signup and view all the answers

What is the potassium requirement for infants?

1 to 2 mEq/kg per day Signup and view all the answers

Study Notes

Fluid and Electrolyte Balance in Pediatric Surgical Patients

Critical understanding of fluid and electrolyte balance is essential in pediatric surgical patients, particularly in infants, due to their limited reserve and high risk of dehydration or fluid overload.
Certain surgical diagnoses, such as gastroschisis or short-gut syndrome, are prone to fluid loss, while others, like congenital diaphragmatic hernia, require careful restoration of intravascular volume to prevent cardiac failure.

Infant Physiologic Day and Fluid Balance Assessment

An infant's physiologic day is approximately eight hours in duration, making regular assessment of fluid balance crucial.
Assessment should include fluid intake and output for the previous eight hours to prevent dehydration or fluid overload.

Clinical Signs of Dehydration and Fluid Overload

Clinical signs of dehydration: tachycardia, decreased urine output, reduced skin turgor, depressed fontanelle, absent tears, lethargy, and poor feeding.
Clinical signs of fluid overload: new oxygen requirement, respiratory distress, tachypnea, and tachycardia.

Physical Assessment of Fluid Status

A complete head-to-toe evaluation is necessary to determine whether perturbations in normal physiology are present.

Total Body Water and Extracellular Fluid

At 12 weeks' gestation, the total body water of a fetus is approximately 94 cc/kg, decreasing to around 80 cc/kg at full term.
Total body water drops an additional 5% within the first week of life, reaching adult levels (60-65 cc/kg) by 1 year of life.
Extracellular fluid reduces parallel to the drop in total body water, with accelerated changes in preterm infants.

Daily Maintenance Fluid Requirements

Formula for estimating daily maintenance fluids: 100 mL/kg for the first 10 kg, plus 50 mL/kg for 11-20 kg, plus 25 mL/kg for each additional kilogram of body weight thereafter.
Conversion to IV fluid orders: 4 mL/kg/h up to 10 kg, add 2 mL/kg/h for 11-20 kg, and add 1 mL/kg/h for each additional kilogram body weight thereafter.

Neonatal Fluid Management

Newborn infants with gastroschisis may require fluid requirements of 150-180 cc/kg/day due to evaporative losses from the exposed bowel.
Precise management of a neonate's fluid status requires understanding of changes in glomerular filtration rate (GFR) and tubular function of the kidney.

Glomerular Filtration Rate (GFR) and Tubular Function

Term newborn's GFR is approximately 21 mL/min/1.73 m2, increasing to 60 mL/min/1.73 m2 within the first 2 weeks of life and reaching adult levels by 2 years of age.
Capacity to concentrate urine is limited in preterm and term infants, with a maximum concentration of 600 mOsm/kg compared to 1200 mOsm/kg in adults.

Sodium and Potassium Requirements

Sodium requirements: 2 mEq/kg per day in term infants, up to 5 mEq/kg per day in critically ill preterm infants due to salt wasting.
Potassium requirements: 1-2 mEq/kg per day.

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Description

Understanding fluid and electrolyte balance is crucial in pediatric surgery, especially in infants who have little reserve. Meticulous attention to hydration status is necessary to prevent fluid overload or dehydration.