Pediatric and Neonatal Anesthesia Flashcards

A 4-week-old ex-premature infant, born at 32 weeks gestation and now 36 weeks post-conceptional age, is scheduled for an inguinal hernia repair under general anesthesia. Which of the following represents the most significant postoperative risk for this specific patient?

Answer: Postoperative apnea

Ex-premature infants, particularly those less than 60 weeks post-conceptional age, have an immature central respiratory control system. This makes them highly susceptible to postoperative apnea and bradycardia, which may occur hours after an apparently uneventful recovery. This risk necessitates admission and cardiorespiratory monitoring for at least 12-24 hours post-surgery. While hypothermia and hypoglycemia are risks for all neonates, the risk of central apnea is the most pronounced and specific life-threatening concern for this demographic.

Compared to a healthy adult, which of the following physiological characteristics is typical of a neonate?

Answer: Higher volume of distribution for water-soluble drugs.

Neonates have a significantly higher percentage of their body weight as total body water (approximately 75-80%) compared to adults (approximately 60%). This results in a larger volume of distribution (Vd) for hydrophilic (water-soluble) drugs, such as succinylcholine or non-depolarizing muscle relaxants, which may necessitate a higher initial dose on a mg/kg basis to achieve the desired effect.

A 5-week-old infant is scheduled for pyloromyotomy due to persistent, non-bilious projectile vomiting. Preoperative correction of fluid and electrolyte status is crucial. What is the classic acid-base and electrolyte abnormality found in this condition?

Answer: Hypochloremic, hypokalemic metabolic alkalosis

Persistent vomiting of gastric contents in pyloric stenosis leads to a significant loss of hydrogen (H+) and chloride (Cl-) ions. This loss of acid results in a hypochloremic metabolic alkalosis. To compensate for dehydration, the renin-angiotensin-aldosterone system is activated, leading to sodium and water retention at the expense of potassium excretion in the kidneys, causing or worsening hypokalemia.

Which of the following statements most accurately describes a key anatomical difference of the pediatric airway compared to the adult airway?

Answer: The narrowest functional part of the airway in an infant is the cricoid cartilage.

In children under approximately 8-10 years of age, the airway is functionally narrowest at the level of the cricoid cartilage, which is a complete, non-distensible cartilaginous ring. In adults, the narrowest portion is the glottic opening (the vocal cords). This anatomical feature is why subglottic edema (croup) can cause significant airway obstruction in children and is the rationale behind the historical use of uncuffed endotracheal tubes to avoid pressure injury to this area.

The Minimum Alveolar Concentration (MAC) of sevoflurane, a measure of anesthetic potency, varies significantly with age. In which of the following age groups is the MAC of sevoflurane highest?

Answer: Infants (1-6 months)

The MAC of volatile anesthetics is not static throughout life. It is lower in neonates, rises to a peak in infancy (approximately 1-6 months of age), and then gradually declines. For sevoflurane, the MAC in a 1-6 month old infant is approximately 3.2%, which is significantly higher than in neonates (around 3.3% but often considered slightly lower than the peak) and much higher than in older children or adults (approx. 2.0-2.5%).

A 2-year-old, 12 kg child is undergoing an orchidopexy. A single-shot caudal block is planned for postoperative analgesia using bupivacaine 0.25%. What is the maximum recommended volume to administer without exceeding the safe dose limit?

Answer: 12 mL

The maximum recommended safe dose for a single-shot bupivacaine block in pediatrics is generally accepted as 2.5 mg/kg. For a 12 kg child, the maximum dose is 12 kg * 2.5 mg/kg = 30 mg. The concentration of the solution is 0.25%, which is equivalent to 2.5 mg/mL. To find the maximum volume, divide the total dose by the concentration: 30 mg / 2.5 mg/mL = 12 mL.