Apparent Life-Threatening Events 

According to the National Institutes of Health:^[1]

An apparent life-threatening event (ALTE) is defined as an episode that is frightening to the observer and is characterized by some combination of apnea (central or obstructive), color change (cyanotic, pallid, erythematous or plethoric) change in muscle tone (usually diminished), and choking or gagging. In some cases, the observer fears that the infant has died. Previously used terminology such as near-miss sudden infant death syndrome (SIDS) or aborted crib death should be abandoned because their use implies a possibly misleading close association between this type of spell and SIDS.

This description was established by expert consensus in 1986 and remains the standard clinical definition.

• Because of marked variability in the clinical presentations of apparent life-threatening events (ALTEs), the true frequency is unknown.
• The estimated frequency of apparent life-threatening events among healthy term infants widely varies (0.5–6% of all newborns), reflecting figures derived from older retrospective reviews of hospital records.^[2]
• A systematic review reported that apparent life-threatening events accounted for 0.6-0.8% of all emergency department visits among children younger than 1 year, was noted in 2.27% of hospitalized children, and had an incidence of 0.6 cases per 1,000 live-born infants.^[3]
• A prospective population-based study of apparent life-threatening events conducted in Austria reported an incidence of 2.46 cases per 1,000 live births.^[4]
• Esani et al (2008) compared the epidemiologic features of apparent life-threatening events and sudden infant death syndrome (SIDS).^[5]

  • Infants who experienced an apparent life-threatening event were younger at the time of clinical presentation.
  • In this study, 74% of patients who experienced an apparent life-threatening event presented when younger than 2 months. By contrast, approximately 25% of SIDS victims are younger than 2 months at the time of death, according to several epidemiologic studies of SIDS.
  • The apparent life-threatening event cohort also included more female infants and fewer infants who were small for gestational age and who had low birth weight when compared with infants who experienced SIDS in other studies. The risk of subsequent death in the apparent life-threatening event group was 0.6%.

The cause of apparent life-threatening events (ALTEs) in infants reflects a differential diagnosis that includes an array of congenital or acquired disorders. As many as 50% of apparent life-threatening events may remain unexplained following a thorough evaluation.

• From retrospective studies, apparent life-threatening events have been associated with gastroesophageal reflux disease; viral lower respiratory tract infection; pertussis; sepsis and/or meningitis; seizures; metabolic disorders; cardiac dysrhythmia (eg, long QT syndrome, supraventricular tachycardia); anemia; nonaccidental trauma; or structural CNS, cardiac (ductal-dependent lesion), or airway anomaly.
• Davies and Gupta (2002) conducted a prospective study of infants who presented to an emergency department with an apparent life-threatening event over a 1-year period.^[6] The results of this prospective study suggest that a standardized approach to evaluation identifies a specific cause in most presentations. Each infant was subject to a standardized evaluation protocol upon admission; only 23% of patients had no diagnosis after evaluation. The apparent life-threatening events were associated with the following:

  • Gastroesophageal reflux disease - 26%
  • Pertussis - 9%
  • Lower respiratory tract infection - 9%
  • Seizure - 9%
  • Urinary tract infection - 8%
  • Factitious illness - 3%
  • Miscellaneous - 11%
• Parker and Pitetti (2011) reviewed the children presenting to an emergency department of a large children’s hospital with a diagnosis of ALTE, looking at follow up mortality. They found a mortality rate of 0.5%; however, in those children who were victims of nonaccidental trauma, the subsequent mortality rate was 9%.^[7]

The evaluation and disposition of an infant following an apparent life-threatening event (ALTE) is directed by a thorough history of the event and a careful physical examination. In most cases, the infant is free of symptoms by the time medical evaluation occurs, allowing for a systematic approach to history-taking and physical examination.

History

Key questions related to the history of the episode include the following:

• Who observed the event? Recognize that second-hand accounts may vary from the history provided by direct observers who were present at the time.
• What was the description of the event? A caregiver’s description of the infants’ color, respiration, and muscle tone is key. Care must be taken to distinguish central cyanosis (lips and oral mucous membranes) from acrocyanosis (hands and feet). Infants who are coughing, choking, or gagging may exhibit a ruddy or plethoric facial color that may be interpreted as “turning blue.” Determine whether apnea was present, and, if so, whether it appeared to be central (lack of respiratory effort) or obstructive (respiratory effort with inadequate airflow). Distinguish apnea that lasted more than 15-20 seconds from periodic breathing, in which respiratory rate and tidal volumes fluctuate and are accompanied by brief pauses in breathing that typically last less than 5-10 seconds.
• Was the infant limp, or was muscle tone increased during or after the event?
• Were any seizurelike movements observed?
• Was any resuscitation required, or did the event spontaneously resolve? Recall that caregivers may provide mouth-to-mouth resuscitation to spontaneously breathing infants with intact perfusion, fearing that the infant’s life is threatened.
• Was the infant born at term, or was the infant premature?
• Were any pregnancy or labor and delivery complications reported?
• Are any factors that predispose to neonatal sepsis noted?
• Has the infant previously exhibited symptoms of gastroesophageal reflux or aspiration of thin liquids? These symptoms may include coughing, choking, or gagging during or after feeding; frequent or excessive spitting-up; persistent nasal stuffiness; or frequent hiccups. Acid reflux disease is suggested by excessive irritability, arching, and straining behaviors displayed during or following a feeding.
• Are the newborn metabolic screening findings normal?
• Does the family have a history of seizures, metabolic disorders, previous sudden infant death syndrome (SIDS), or unexplained death in infancy or childhood?

Physical examination

A complete physical examination begins by obtaining a full set of vital signs, including pulse oximetry.

• A full head-to-toe examination of the skin should be performed to look for skin lesions or signs of trauma.
• The head and neck examination should note the characteristics of the anterior fontanelle (ie, normal, bulging, or sunken). Nondilated funduscopic examination should be performed. If retinal hemorrhages are suspected, a formal dilated indirect examination may be necessary for further characterization.^[8] The nose and mouth should be examined for the presence of blood or formula.
• The respiratory examination should include the respiratory rate, pattern of breathing, and adequacy of air exchange. The presence of stridor, wheezes, or crackles should be noted.
• The cardiovascular examination should reveal whether murmurs are present and the adequacy and symmetry of pulses. In young infants, suspicion for ductal-dependent cardiovascular lesions may be heralded by a differential in blood pressure findings, oximetry findings, or both in the right upper extremity compared with measurements obtained from the lower extremities.
• Abdominal distension or tenderness may indicate acute intestinal obstruction. Inguinoscrotal examination should evaluate for incarcerated inguinal hernia or testicular torsion.
• Neurologic assessment begins with assessment of the infants’ responsiveness. Determine whether lethargy is persistent or resolved and whether the muscle tone and reflexes are appropriate for age. Also, determine if any focal or lateralizing findings are present.
• The skin should be carefully examined for bruises. The bones should be carefully palpated for signs of trauma.

• The laboratory evaluation of an infant following an apparent life-threatening event (ALTE) is directed by a thorough history of the event and careful physical examination.
• Altman et al (2007) noted that signs or symptoms indicative of acute infection are typically present among infants with apparent life-threatening events who are subsequently shown to have bacterial infection.^[9] However, in this study, some infants with urinary tract infection or pneumonia lacked conventional signs or symptoms, suggesting the need to consider these types of infections in infants with apparent life threatening events.
• Zuckerbraun et al (2009) determined that serious bacterial infections (SBIs) occurred in 2.7% of afebrile, well-appearing infants younger than 60 days who experienced an apparent life-threatening event.^[10] Infants with a history of prematurity were more likely to have an SBI than infants born at term (6.7% vs 0.8%; P = 0.04), suggesting the need for added vigilance in screening premature infants for SBI following an apparent life-threatening event.
• Diagnostic evaluation may include the following:

  • A CBC count to screen for the presence of systemic viral or bacterial infection or anemia^[11]
  • Serum chemistry levels to assess for hypoglycemia, hyponatremia, hyperkalemia, acidemia, hypocalcemia, or elevation of serum lactate
  • ABG to assess for acidosis or retention of carbon dioxide
  • Serum or urine toxicology studies for suspected ingestions
  • Specific bacterial or viral cultures to assess for respiratory syncytial virus (RSV), pertussis, bacteremia, or urinary tract infection
  • ECG to assess for long QT syndrome and preexcitation that suggests supraventricular tachycardia or other dysrhythmia
  • EEG to assess for epileptiform activity
  • Upper GI contrast studies to assess for swallowing dysfunction, thin liquid aspiration, or upper-intestinal anatomic malformations
  • Impedance pH monitoring to assess for gastroesophageal reflux disease
  • Neuroimaging to assess for hemorrhage or structural CNS abnormality
  • Polysomnography to assess for sleep-based disturbances in cardiorespiratory control

• In-hospital observation has been suggested for most infants following an apparent life-threatening event (ALTE). The initial evaluation of some infants reveals active ongoing symptoms and clearly suggests the need for hospitalization for further evaluation and treatment (eg, sepsis). However, apparent life-threatening events that are the result of self-resolving episodes of choking or gagging associated with feedings in well-appearing infants may be observed in an outpatient setting.
• Claudius and Keens (2007) noted that infants who were younger than 1 month at the time of presentation or who had a history of recurrent apparent life-threatening events were at high risk for eventual diagnoses that required further in-hospital evaluation.^[12] This study suggests that well-appearing infants older than 30 days who have experienced a single apparent life-threatening event and who have normal initial screening findings may be safely discharged from the hospital with proper outpatient follow-up.
• Documenting cardiorespiratory monitors may be considered for preterm infants who are at high risk for recurrent apnea or bradycardia and for infants who depend on technology due to specific disorders of cardiorespiratory control.^[13]