Pediatric Surgical Anatomy and Physiology
Core concepts
Anatomy and physiology underpin safe pediatric perioperative care. Key differences from adults include a proportionally larger head and tongue, a narrowest airway at the cricoid ring in younger children, a short trachea, and a compliant, easily compressed chest. Infants are obligate nasal breathers early in life and have a high metabolic rate with high oxygen consumption, so desaturation occurs quickly during apnea. The liver and kidneys are immature, altering drug metabolism and clearance; neonates have lower albumin and reduced protein binding, increasing free drug levels. Thermoregulation is immature: infants lose heat rapidly because of a large surface-area-to-body-mass ratio and limited shivering, so hypothermia, acidosis, and coagulopathy can follow. Fluid compartments differ: a higher proportion of body water is extracellular, so insensible losses are greater. Understanding surgical anatomy also matters, such as recognizing that a pyloric stenosis involves the pylorus and presents with projectile vomiting and hypochloremic hypokalemic metabolic alkalosis.
Traps in questions
A frequent trap applies adult airway anatomy to children, or assumes the narrowest point is the glottis at all ages. Another trap ignores that neonates have immature hepatic and renal function. Do not assume a child can shiver to maintain temperature.
Rule of thumb
When a question describes rapid desaturation during induction, suspect reduced functional residual capacity plus high oxygen consumption; preoxygenation and prompt airway management are the reasoning anchors.