Brief resolved unexplained event

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  • Abbreviation: BRUE
  • BRUE was formerly known as Apparent life-threatening event (ALTE)[1]
  • BRUE definition has a strict age limit unlike ALTE and a BRUE should only be considered if there is not other likely explanation.
  • Peak incidence: 1wk - 2mo
  • BRUE is a symptom and requires evaluation for the actual diagnosis causing the event
  • Only 10% have repeat events
  • BRUE is not related to SIDS


BRUE diagnosis is only made by a clinician based on the features and is not based on the caregiver's perception of what happened. BRUE is an event occurring in an infant <1 year of age when an observer reports a sudden, brief ( <1 minute but typically <20–30 seconds), and now resolved episode of ≥1 of the following:[1]

  • Cyanosis or pallor
  • Absent, decreased, or irregular breathing
  • Marked change in tone (hyper- or hypotonia)
  • Altered level of responsiveness
  • Must have returned to baseline

A BRUE should only be diagnosed when there is no explanation for a the event after full history and physical

ALTE to BRUE Definiton Changes

  • BRUE has a strict age limit < 1yo
  • There must be no other explanation for the event (not something as simple as nasal congestion, choking, viral infection or vomitting)
  • Caregiver's perception of a BRUE does not make an event a BRUE without clinical suspicion
  • Altered responsiveness is a new criteria

Risk Factors

  • RSV infection
  • Prematurity
  • Recent anesthesia
  • GERD
  • Airway/maxillofacial anomalies
  • Age < 10 wks
  • History of apnea
  • Pallor, cyanosis, feeding difficulties

Clinical Features

Episode that is frightening to caregiver and involves combination of:

  • Apnea
  • Color change
  • Muscle tone change
  • Choking or gagging

Pertinent History

The history in an BRUE should focus extensively on the details surrounding the event, need for resuscition, prior events, possible related medical conditions, or historic findings that may indicate prior events.

Past Medical History

  • Prematurity, history of apnea, prior resp/feeding difficulties?
  • Immunization status (particularly pertussis)

Family HIstory

  • History of SIDS, cardiac abnormalities, seizures, or metabolic disease?


  • Duration of the BRUE
  • Was resuscitation with CPR and rescue breaths required?
  • What was the temporal relationship with feeding, sleeping, crying, vomiting, or choking
  • Any episodes concerning for central versus obstructive patterns of apnea
  • Any progressive or episodic changes in mental status

Differential Diagnosis

The differential diagnosis is quite extensive and although a broad workup is often started in the ED including evaluation for sepsis and occult infections and metabolic disorders, a cause is infrequently found[2]


  • Idiopathic (~50%)
  • GERD
  • Seizure
  • Respiratory tract infection
  • Misinterpretation of benign process (e.g. periodic breathing)
  • Vomiting/choking episode

Less Common

  • Pertussis
  • Inflicted injury
  • Poisoning
  • Serious bacterial infection
    • Must consider in all febrile patients with BRUE
  • Electrolyte abnormality (includes glucose)




Individualize testing by history and exam. These are generally not needed for the low risk patients.


Low Risk Criteria

The following criteria place the child at low risk of adverse events[1]

  • Age >60 days
  • Gestational age > 32 weeks
  • First BRUE
  • No CPR by a medical provider
  • No concern for child abuse, family history of sudden unexplained death,or toxic exposures
  • No abnormal physical findings: (bruising, cardiac murmurs, organomegaly).


Low Risk

Low Risk infants can be safely discharged but there should be shared decision making with parents.

  • Also offer the family CPR training resources
  • Consider pertussis swab, ECG, and brief monitored observation in the ED.
  • No other consults, metabolic or hematologic labs or medications are necessary for discharge


Low Risk

Discharged with shared parental decision making and close outpatient follow-up

Not Low Risk

Admission in most cases

Especially for:

  • <30 wks preterm[4]
  • Ill-appearing or abnormal vitals (including pulse ox)[5]
  • Bronchiolitis or pertussis with apnea
  • >1 event in past 24hr or multiple BRUE
  • Abnormalities in past medical history
  • Prolonged central apnea >20 seconds
  • Need for resuscitation
  • Family history of SIDS

Current Research

  • Neither of these decision rules have been validated

Mittal ALTE Decision Rule[6]

  • 300 Infants in a single center with 76% admission rate with 37 (12%) required significant intervention
Predictors for requiring intervention
  • Prematurity
  • Abnormal physical examination
  • Color change to cyanosis,
  • Absence of upper respiratory infection symptoms and the absence of choking
  • Negative predictive value: 96%
  • Specificity of 70.5%
  • 7 out of the 184 (3.8%) were incorrectly discharged

Kaji ALTE Decision Rule[7]

  • 832 patients from 4 different study sites, with a 79.2% admission rate
Predictors for requiring admission
  • Obvious need for admission:
    • Supplemental Oxygen requirement
    • Resuscitation
    • Hemodynamic Instability
    • Positive RSV or Pertussis test
  • Significant past medical history
    • Congenital heart disease
    • Down Syndrome
    • Previous Intubation
  • Chromosomal abnormaility
  • Chronic Lung Disease
  • > 1 BRUE in 24 hours
  • Negative predictive value of 96.5%
  • Sensitivity of 89% , a Specificity of 61.9% , and a calculated
  • 14 (2%) patients were incorrectly discharged

See Also

External Links

Brue - Don't forget the bubbles


  1. 1.0 1.1 1.2 Tieder et al. Brief Resolved Unexplained Events (Formerly Apparent Life-Threatening Events) and Evaluation of Lower-Risk Infants. Pediatrics. May 2016, Vol. 137(5)
  2. McGovern MC. et al. Smith MB. Causes of apparent life threatening events in children: a systemic review. Arch Dis Child. 2004;89(11):1043-1048
  3. Okada K et al. Discharge Diagnoses in infants with apparent life threatening event admissions and gastroesophageal reflux disease. Pediatric Emergency Care. 2012;28(1):17-21
  4. Claudius I, Keens T. Do all infants with apparent life-threatening events need to be admitted? Pediatrics. 2007;119(4):679–683pmid:17403838
  5. Hunt CE et al. Collaborative Home Infant Monitoring Evaluation (CHIME) Study Group. Longitudinal assessment of hemoglobin oxygen saturation in healthy infants during the first 6 months of age. J Pediatr. 1999;135(5):580–586pmid:10547246
  6. Mittal M. et al. A clinical decision rule to identify infants with apparent life-threatening events who can be safely discharged from the emergency department. Pediatric Emergency Care. 2012;28(7): 599-605
  7. Kaji A et al. Apparent life-threatening event: multicenter prospective cohort study to develop a clinical decision rule for admission to the hospital. Ann Emerg Med. 2013;61(4):379-387