Infant Apnea

Etiology

The etiology of apnea in infants is broad and varies according to the age of the infant and the pathophysiological mechanism.[3][4][5]

Preterm infants, especially those under 28 weeks gestation are highly prone for apnea due to the poor development of mechanisms of respiratory control and have apnea of prematurity.

Apnea soon after birth can occur due to birth asphyxia, maternal drug use, infections, metabolic causes and congenital anomalies.

Causes of Central apnea include central nervous system (CNS) infections (meningitis, encephalitis), head trauma (birth asphyxia or abusive trauma), toxin exposure, pertussis, infant botulism, inborn errors of metabolism (mitochondrial disease, Pompe disease, Leigh syndrome, and the mucopolysaccharidoses), metabolic derangements (hypoglycemia, hypocalcemia, and acidosis) and congenital anomalies (congenital central hypoventilation, Down syndrome and Arnold-Chiari malformation).

Obstructive apnea can occur due to obstructive sleep apnea, infections (pneumonia, croup), vocal cord paralysis, and congenital upper airway anomalies (e.g., Pierre-Robin sequence)

Mixed apnea occurs predominantly among premature infants but can also be caused by gastroesophageal reflux, pertussis, and bronchiolitis. 

Epidemiology

The true prevalence and incidence of apnea in infants in unknown. Among preterm infants, the incidence of apnea is inversely related to gestational age with almost every infant younger than 28 weeks gestation having an episode and 50% of infants born between 33 weeks and 34 weeks. The incidence of apnea in the full-term infant is one per 1000.[6]

Pathophysiology

The relatively immature respiratory center among infants, particularly the preterm infants, makes them vulnerable to apneic episodes in the face of internal and external stressors. Unlike adults and older children, neonates respond to hypoxia and hypercarbia with a brief increase in respiratory rate followed by respiratory depression and apnea. When feeding, poor coordination of sucking and breathing affects ventilation, further accentuated by exaggerated laryngeal chemical reflexes that depress the respiratory center causing apnea. Infants are very sensitive to stressors such as anemia, hypoglycemia, hypothermia, and toxin exposure that can depress the respiratory center. The very pliable thoracic cage causes a collapse of the chest wall resulting in increased work of breathing and eventual tiring of chest muscles that lead to respiratory failure and apnea.

History and Physical

The initial history should be aimed to differentiate between a true apneic episode and periodic breathing or breath-holding spell. Once deemed as an apneic episode, a thorough review of the antenatal, perinatal, postnatal, and feeding history should be done. History of apneic episodes should be elicited as this indicates a life-threatening underlying cause and a higher probability of recurrence. The family history of seizures, infant deaths, and the presence of serious illnesses in family members should also be ascertained. Social history should ask about potentially toxic exposures, including drugs or medications in the home, tobacco smoke exposure, and potential carbon monoxide exposure. Associated symptoms such as sleep problems, snoring, mouth breathing should be inquired. A physical exam often provides valuable clues and aids to identify congenital anomalies, genetic syndromes or stigmata of inborn errors of metabolism and congenital infections.  Fever or hypothermia can raise the suspicion of sepsis or other infectious processes, tachypnea may indicate a lower respiratory tract infection or metabolic acidosis, and stridor indicates an upper airway obstruction. Unexplained skin bruises should raise a suspicion of child abuse.

Evaluation

The performance of lab and imaging studies should be guided by the history and physical exam findings. In neonates, complete blood count, serum glucose, calcium, and electrolyte measurement can be considered. If the infant is febrile or hypothermic and a serious infection is suspected, appropriate cultures of blood, urine, and possibly cerebrospinal fluid (CSF) should be obtained. An EKG can be done to rule out cardiac dysrhythmias, especially the Long QT syndrome. Neuroimaging, EEG, specialist consults are not routinely recommended unless specifically indicated by the clinical picture. If the patient meets low-risk criteria for a Brief Resolved Unexplained Event (BRUE), no lab studies are indicated.[7][8]

Treatment / Management

The initial step in the management of apnea in infants is to assess the need for immediate resuscitation and/or stabilization of the infant. Subsequent management consists of determining the underlying etiology and instituting targeted specific therapy to the identified cause. For neonates, a period of observation with cardiorespiratory and pulse oximetry monitoring in the neonatal intensive care unit (NICU) is recommended. For infants with apnea of prematurity, interventions are recommended if apneic spells are frequent, prolonged, need frequent stimulation, or are associated with bradycardia and hypoxia. These infants benefit from nasal continuous positive airway pressure (CPAP) and methylxanthine therapy. There is no evidence that methylxanthine therapy is effective in term infants. Speech or occupational therapy may be consulted for infants with feeding-related issues. Management of infants in the low-risk BRUE category consists of parental reassurance and education. [9][10][11]

Differential Diagnosis

• Aspiration syndrome

• Bacteremia

• Botulism

• Bronchiolitis

• Bronchopulmonary dysplasia

• Childhood sleep apnea

• Croup

• Heart failure, congestive

• Influenza

• Laryngomalacia

• Munchausen syndrome by proxy