Etiology of Apneas and Bradycardeas in Prematurity

Apenea and bradycardias are main concern in premature infants.  Apnea is defined as the cessation of breathing for longer than 20 seconds, or a shorter duration in the presence of pallor, cyanosis, or bradycardia (1). In preterm infants less than 1,500 grams at birth, approximately 70% will have at least one clinically observed episode of symptomatic apnea while in the neonatal intensive care unit (NICU), and about 20% of these infants will have a specific medical cause. The other 80% of preterm infants with symptomatic apnea do not have a specific medical cause and by exclusion are then diagnosed as having AOP, the most important and prevalent disorder of respiratory control occurring in preterm infants.

Etiology (2)

• Idiopathic: Apnea of prematurity with immaturity of respiratory centers; modified by sleep state
• Central Nervous System: Intracranial hemorrhage, seizures, depressant drugs, hypoxemia, hypothermia, hyperthermia
• Respiratory: Pneumonia, obstructive airway lesions, Respiratory Distress Syndrome, laryngeal reflex, phrenic or vocal cord paralysis, pneumothorax, hypoxemia, hypercarbia, nasal occlusion caused by phototherapy eye patches, tracheal occlusion caused by neck flexion
• Cardiovascular: Heart failure, hypotension, hypertension, hypovolemia, increased vagal tone
• Gastrointestinal: Gastroesophageal reflux, abdominal distension, peritonitis
• Infection: Pneumonia, sepsis, meningitis
• Metabolic: Acidosis, hypoglycemia, hypocalcemia, hyponatremia, hypernatremia
• Hematological: Anemia

(1) Hunt CE. Apnea and sudden infant death syndrome. In: Kliegman RM, Nieder ML, Super DM, eds. Practical strategies in pediatric diagnosis and therapy. Philadelphia: WB Saunders, 1996: 135-147.
(2) Avery's Neonatology, 6th edition, taple 1-28