47: Apnea and Bradycardia (“A's and B's”)

I. PROBLEM

An infant has just had an apneic episode with bradycardia. Apnea is the absence of breathing for >20 seconds or a shorter pause (>10 seconds) associated with oxygen desaturation or bradycardia (<100 beats/min). Shorter apnea <10 seconds without hypoxemia or bradycardia is due to immaturity and is not clinically important. The incidence of apnea of prematurity (AOP) is inversely correlated with gestational age and birthweight. Apnea occurs in >50% of infants <1500 g and in 90% of infants <1000 g. Types of apnea with approximate incidence are:

1. Central apnea. Complete absence of the brainstem stimulus to breathe, resulting in no respiratory effort (40%).

2. Obstructive apnea. Infant breathes but no airflow is present because of an obstruction by mucus or airway collapse (10%).

3. Mixed apnea. Elements of both central and obstructive apnea. This is the type found in most preterm infants (>50%).

4. Periodic breathing. Three or more respiratory pauses lasting >3 seconds separated by normal respiratory intervals not >20 seconds and not associated with bradycardia. Periodic breathing can occur in 2–6% of healthy term neonates and in up to 25% of preterm infants.

5. Apnea of infancy (AOI). American Academy of Pediatrics (AAP) definition: “an unexplained episode of cessation of breathing for 20 seconds or longer or a shorter respiratory pause associated with bradycardia, cyanosis, pallor, and/or marked hypotonia” in an infant >37 weeks' gestational age.

6. Apnea of prematurity (AOP). Sudden absence of breathing that lasts at least 20 seconds or is associated with bradycardia or cyanosis (oxygen desaturation) in an infant <37 weeks' gestational age. It is most commonly central or mixed apnea. AOP is a developmental disorder usually of physiologic immaturity of respiratory control but other diseases may contribute. AOP may be hereditary. AOP usually presents on days 2–7. If apnea presents in the first 24 hours of life or after day 7, it is very unlikely to be AOP. Note: Apnea of prematurity is a diagnosis of exclusion.

7. Persistent apnea. Apnea persists in a neonate ≥37 weeks postmenstrual age. It usually occurs in infants born at <28 weeks' gestation.

8. Secondary causes of apnea. Apnea that has a specific cause (eg, sepsis, anemia, asphyxia, temperature instability, pneumonia, and others). Remember immaturity can worsen any apnea that is associated with a specific cause.

II. IMMEDIATE QUESTIONS

1. Did you observe the apnea? What was going on when the apnea occurred? Do you know what type of apnea it is? Try to distinguish the type; obstructive apnea is the easiest to detect visually while central and mixed are more difficult. A thorough history of the event may help differentiate the type of apnea. If it occurred during feeding with a naso- or orogastric tube, is the tube in proper position? (Stimulation of laryngeal receptors causes central apnea.) Did it occur with insertion of a naso-/orogastric tube? Think vagal response. (Stimulation of the vagal nerve resulting in central apnea.) Does it just occur with feeding? ...