Apparent life-threatening event

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Chapter 5 APPARENT LIFE-THREATENING EVENT

Jonathan M. Wong

General Discussion

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, color change, change in muscle tone, choking, or gagging. These episodes may necessitate stimulation or resuscitation to arouse the child and reinitiate regular breathing.

The true incidence of ALTEs is unknown because epidemiologic data are derived from inpatient admissions and emergency rooms, and not all children who have an ALTE are brought in for evaluation. The reported incidence of ALTE is 0.05% to 6%. Most episodes occur in children younger than 1 year, and some studies have implied a peak incidence between 1 week and 2 months of age, with most occurring within the first 10 weeks of life.

The underlying cause of ALTE varies greatly and should be thought of as a manifestation of other conditions. In one half of patients, the cause is discovered either through careful history and physical examination, diagnostic evaluation (see below), or both so that intervention is possible, perhaps preventing future episodes. By default, a specific cause is not found in the remaining cases, placing them in the idiopathic category.

According to one major study of 243 patients, history and physical examination alone yielded a cause 21% of the time, whereas diagnostic tests alone (when history and physical were not elucidative), yielded a cause 14% of the time. This speaks to the importance of a careful history and physical examination while revealing that a shotgun approach to diagnostic testing is not helpful.

The challenge is to manage the immediate event, discern the underlying cause, educate parents and alleviate their concerns, and determine the need for future monitoring. The outcome depends on the subgroup into which the patient falls. For example, patients for whom the ALTE was a heralding event (seizure disorder or neurologic condition) have a higher mortality rate and less than optimal outcome. Mortality data reveal a rate between 0% and 4% between 1972 and 1989.

No clear association has been made between sudden infant death syndrome (SIDS) and ALTEs. The rate of ALTEs has not decreased with the “back-to-sleep” program; however, patients who have suffered from an ALTE are at greater risk for sudden death. Follow-up studies have shown no long-term neurodevelopmental, cognitive, or gross motor delays in children who have suffered an ALTE compared with controls.

Hospitalization for observation and work-up is recommended for most children with an ALTE. Criteria have been developed to help determine which children should be hospitalized. These criteria include the need for vigorous stimulation or cardiopulmonary resuscitation (CPR) to arouse the child, any abnormalities in the history or physical examination, or an unreliable home situation.

Medications Associated with ALTE

ALTE can be associated with any prescription, over-the-counter, or herbal medicines. It can be associated with accidental ingestion, intentional ingestion, overdose, or underdosing of therapeutic medications. Some common examples include the following:

• Antiepileptics

• Antipsychotics

• Barbiturates

• Ethylene glycol

• Methanol

• Opioids

• Salicylates

• Salt poisoning

Causes of ALTE

Cardiac Causes (~5%)

• Arrhythmia

• Cardiomyopathy

• Congenital heart disease such as double aortic arch

• Long QT syndrome

• Myocarditis

• Wolff-Parkinson-White syndrome

Child Abuse (<5%)

• Munchausen by proxy (suffocation, intentional salt poisoning, medication overdose, physical abuse, head injury)

• Smothering (intentional or accidental)

Gastrointestinal Causes (most common, up to 50% of diagnosed cases)

• Gastric volvulus

• Gastroesophageal reflux disease (GERD)

• Intussusception

• Swallowing abnormalities

Idiopathic, also known as central apnea (up to 50%)

Infectious Causes

• Sepsis

• Urinary tract infection

Metabolic Abnormalities (<5%)

• Electrolyte disorders

• Endocrine disorders

• Inborn errors of metabolism

Neurologic Causes (~30%)

• Brainstem malformations

• Budd-Chiari malformation

• Central nervous system (CNS) bleeding

• CNS infection (meningitis, encephalitis)

• Febrile seizure

• Hydrocephalus

• Infantile spasm

• Malignancy

• Seizure disorder

• Vasovagal reflex

• Ventriculoperitoneal (VP) shunt malformation

Respiratory Causes (~20%)

• Airway obstruction

• Apnea of prematurity/infancy

• Bronchiolitis, especially respiratory syncytial virus (RSV)

• Breath-holding spell

• Central hypoventilation

• Choking

• Croup

• Foreign body aspiration

• Laryngotracheomalacia

• Mycoplasma

• Obstructive sleep apnea

• Periodic breathing

• Pertussis

• Pneumonia

• Vocal cord abnormalities

Other Causes

• Anaphylaxis

• Carbon monoxide poisoning

• Ethanol ingestion

• Food allergy

Key Historical Features

Evaluation of risk factors for ALTE

• Prematurity (even higher for those with RSV infection or who undergo general anesthesia)
• Rapid feeders
• Frequent coughers
• Choking during feedings
• Male gender
• Previous history of ALTE

Description of the event (best obtained from the most direct witness)

• Duration of event (length of time required to reinstate normal breathing and normal behavior/tone OR length of time of resuscitation)
• Condition of child (awake/asleep)
• Position of child (prone/supine/side)
• Location of child (crib/parent’s bed/car seat)
• Surroundings (pillows/bedclothes/blankets)
• Activity at time of event (feeding/coughing/gagging/choking/vomiting)
• Breathing efforts (none/shallow/gasping/increased)
• Color of child and location of any discoloration (pallor/red/purple/blue/peripheral/whole body/circumoral)
• Movement and tone (rigid/tonic-clonic/decreased/floppy)
• Vomiting or sputum production
• Wheeze/stridor/crying
• Interventions (None/gentle stimulation/blowing air in face/vigorous stimulation/mouth-to-mouth/CPR)

Recent symptoms

• Fever
• Poor feeding
• Weight loss
• Rash
• Lethargy
• Sick contacts

Medical history

• Prenatal history (use of drugs/alcohol/tobacco during pregnancy)
• Prematurity or small for gestational age
• Birth history (trauma/hypoxia/presumed sepsis)
• Feeding history (gagging/coughing/poor weight gain)
• Developmental history
• Previous admissions (surgeries, other ALTEs)
• Accidents (being dropped/tossed/trauma)

Medications

Allergies

Family history

• Congenital problems
• Neurologic problems
• Neonatal problems
• Sudden death
• ALTEs
• Cardiac arrhythmias

Social history

• Home situation
• Caregivers
• Smoking in home

Key Physical Findings

Vital signs

Height, weight, and head circumference

General impression of the child’s well-being

Dysmorphic features or obvious malformations

Neurologic examination, especially muscle tone and reflexes

Appropriateness of developmental stage

Signs of trauma/bruising (retinal hemorrhage, battle sign, raccoon eyes)

Thorough cardiopulmonary examination

Abdominal examination

Genitourinary examination

Musculoskeletal examination

Other areas as directed by the history

Suggested Work-up

Laboratory and imaging studies should be performed on the basis of history and physical examination. A few baseline tests are generally recommended as a minimum work-up (most likely to lead to a cause for ALTE):

Complete blood cell count (CBC) with differential To evaluate for infection or anemia
Electrolytes, magnesium, and calcium To evaluate for electrolyte disturbance or metabolic abnormalities
Serum bicarbonate To evaluate for hypoxemia or acidosis
Blood urea nitrogen (BUN) and creatinine To evaluate for dehydration or renal disease
Serum lactate To evaluate for hypoxemia, toxin exposure (salicylates, ethylene glycol, methanol, ethanol), or hereditary enzyme defects (glycogen storage type 1, fatty acid oxidation defects, multiple carboxylase deficiency, methymalonicaciduria)
Serum glucose To evaluate for hypoglycemia or hyperglycemia
Urinalysis and urine culture To evaluate for urinary tract infection
Chest radiographs To evaluate for infection or cardiomegaly
Electrocardiography (ECG) To evaluate for arrhythmia or QT abnormalities

Additional Work-up

The following tests may be indicated based on findings from the history and physical examination:

Blood cultures If infection/sepsis is suspected
Brain imaging (computed tomography [CT], magnetic resonance imaging [MRI]) To evaluate for trauma, neoplasm, or congenital abnormalities
Nasal swab for RSV To evaluate for RSV infection
Pertussis culture/serology To evaluate for pertussis infection
Radioisotope milk scan or esophageal pH To evaluate for gastroesophageal reflux
Nasopharyngeal aspirate To evaluate for upper airway infections
Liver function studies To evaluate for hepatic dysfunction
Lumbar puncture with spinal fluid analysis and cultures If meningitis is suspected
Stool cultures If infection is suspected
Urine toxicology screen If metabolic disorder or accidental/intentional overdose is suspected
Skeletal survey To evaluate for previous or current fractures
Echocardiogram To evaluate for valvular dysfunction or structural abnormalities
Pneumogram To evaluate for breathing problems

References

1. Brand D.A., Altman R.L., Purtill K., Edwards K.S. Yield of diagnostic testing in infants who have had an apparent life-threatening event. Pediatrics. 2005;115:885–893.

2. Farrell P.A., Weiner G.M., Lemons J.A. SIDS, ALTE, apnea, and the use of home monitors. Pediatrics in Review. 2002;23:3–9.

3. Hall K.L., Zalman B. Evaluation and management of apparent life-threatening events in children. American Family Physician. 2005;71:2301–2308.

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