CHAPTER 25 Pediatric Anesthesia


Many significant changes occur as a newborn
baby grows and develops into an adolescent and then an adult. All the physiological and psycho­logical changes are unique to children and have a considerable impact while anesthetizing them. This chapter will help anesthetists to acquaint physiological changes in children along with their anesthetic implications.

Definitions: Pediatric age group ranges from neonate to adolescent as shown in Table 25.1.

Table 25.1 Pediatric age group classification

Table 25.1 Pediatric age group classification

Age group



From birth till 44 weeks of postconceptional age


Up to 12 months of age


1–12 years


13–16 years

Postterm infant

An infant born after 42 completed weeks of POG

Term infant

One born after 37 and before 42 completed weeks of POG

Preterm infant

One born before 37 completed weeks of POG

Preterm infant subgroups (based on actual weight)

LBW infant

Weighs < 2,500 g regardless of the POG

VLBW infant

Weighs < 1,500 g

ELBW infant

Weighs < 1,000 g


Infants weighing less than 750 g

Abbreviations: ELBW, extremely low birth weight; LBW, low birth weight; POG, period of gestation; VLBW, very low birth weight.

Normal physiological values according to age are as follows:

  1. Weight (kg) = (age + 4) × 2; accurate till
    10 years of age.

  2. Total body water (TBW): term neonate = 75%; estimated blood volume (EBV) = 85 mL/kg.

  3. Preterm infants = TBW > 80% with >50% as extracellular fluid (ECF) and EBV = 90 to 100 mL/kg.

  4. Respiratory rate = 24 – age/2; tidal volume = 6 to 8 mL/kg.

  5. Cardiac output = 300 to 400 mL/kg/min at birth; 200 mL/kg/min within a few months.

  6. Circulatory parameters (heart rate and systolic blood pressure [SBP]) are listed in Table 25.2.

Table 25.2 Circulatory parameters in pediatrics

Table 25.2 Circulatory parameters in pediatrics

Age (years)

Heart rate (per min)

Systolic BP (mm Hg)






















Anatomical/Physiological Considerations

Children are not a smaller version of adults. There are a host of anatomical and physiological differences.


  • They have a large head and large tongue with a short neck.

  • The tongue is relatively large.

  • Neonates are obligate/preferential nasal breathers (till 5 months of age).

  • The larynx is high (C3–C4) and anterior. The epiglottis is long, floppy, and U-shaped. It tends to fall posteriorly in the supine position. Unlike the “sniffing” position, the head needs to be in a neutral position to improve the glottic view.

  • The airway is funnel-shaped with the narrowest part at the level of the cricoid cartilage.

  • The trachea is short (4–5 cm in the neonate). There is a high chance of endotracheal tube (ETT) dislodgement or endobronchial migration of ETT with head movement.

Respiratory System

  • Limited respiratory reserve, absent “bucket handle” action of ribs, diaphragmatic breath­ing, and low functional residual capacity (FRC) due to highly compliant chest wall.

  • FRC further decreases with apnea and anesthesia, causing lung collapse.

  • The closing volume is larger than the FRC until 6 to 8 years of age. This causes an increased tendency for airway closure at end-expiration. Thus, neonates and infants generally need positive pressure ventilation (PPV) with positive end-expiratory pressure (PEEP) during anesthesia.

  • The diaphragm has a lower percentage of type I muscle fibers and therefore easily subject to fatigue.

  • The development of alveoli occurs over the first 8 years of life.

  • Premature infants are at risk of apneas in the postoperative period.

  • Respiratory distress syndrome (RDS) is frequent at <28 weeks due to reduced surfactant.

Cardiovascular System

  • Patent ductus arteriosus (PDA) more common in premature infants; it closes typically 10 days to 2 weeks after birth but may reopen in the first few weeks after
    birth whenever pulmonary arterial pres­sure rises (hypoxemia, hypercarbia, aci­dosis, etc.), which is known as transitional circulation.

  • The neonatal heart is poorly compliant and has reduced contractile force due to dis­organized intracellular contractile proteins and immature sarcoplasmic reticulum.

  • The cardiac output is rate-dependent in neonates and children with reduced capacity to increase stroke volume by premature heart. Therefore, bradycardia is poorly tolerated, and cardiac compression should be provided in the neonate with a heart rate < 60 bpm.

  • The dominant vagal tone makes neonates and infants prone to bradycardia.

Renal System

  • The glomerular function and tubular fun­ction mature by 2 years and 8 months of life, respectively.

  • Normal urine output ranges between 1 and 2 mL/kg/h.

Hepatic System

  • Liver cytochrome P-450 enzymes achieve maturity at the adult level by 6 months.

  • Premature infants are prone to hypo­glycemia because of hepatic glycogen storage development in the last few weeks of gestation.


  • The hemoglobin is around 18 to 20 g/dL at the time of birth, which decreases to 9 to
    12 g/dL over the next 3 to 6 months.

  • At birth, HbF is the predominant hemo­globin (70–80%), the levels of which drop to around 5% within 3 months.

  • The deficiency of vitamin K-dependent clotting factors and platelets during the first few months of life puts neonates at risk of intracranial bleed. Therefore, vitamin K is given at birth to prevent hemorrhagic disease of the newborn.

Temperature Control

  • Neonates and preterms are more prone to heat loss due to:

    • Relatively larger body surface-to-body weight ratio.

    • Poorly developed subcutaneous tissue.

    • Inability to use shivering thermogenesis.

  • These are partially compensated for by nonshivering thermogenesis via brown fat, which is inhibited by volatile and intravenous anesthetics.

  • Hypothermia leads to cardiovascular stress, delays emergence from anesthesia.

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Dec 11, 2022 | Posted by in ANESTHESIA | Comments Off on CHAPTER 25 Pediatric Anesthesia

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