Authors: Sandi Angus, Lisa Kehler / Editor: Lauren Fraser / Reviewer: Sandi Angus / Codes: RC4, SaP2, SLO5 / Published: 12/05/2021 / Reviewed: 29/05/2024


Infants who present with an acute event reported by the caregiver represent a wide range of patients with diverse pathophysiology.

The challenge as physicians is to identify those who are at risk of recurrence or of having a serious underlying disorder.


The term “BRUE” (Brief Resolved Unexplained Event) has replaced the term “ALTE” (Apparent Life-Threatening Event).

ALTE is an old term for events that are characterised by some combination of “apnoea, colour change, change in muscle tone, or choking and gagging and are frightening to the observer”.

This term has been replaced as it described events that ranged from normal physiological events to pathological events and so was not useful in determining diagnosis, treatment or prognosis.

In the majority of patients, ALTEs were often benign, but the name implied that the child’s life was at risk. This reinforced parental anxiety and potentially led to unnecessary investigations.

BRUE is defined as an episode in an infant less than 12 months of age characterised by:

  • <1 minute duration (typically 20-30s)
  • A return to baseline state
  • Not explained by any identifiable medical condition (i.e. medically well)
  • Includes one or more of the following features:
    • Central cyanosis/pallor
    • Absent, decreased or irregular breathing
    • Marked change in tone (hyper- or hypotonia)
    • Altered level of consciousness

Where events do not fit the definition of BRUE, an alternative diagnosis should be sought.

Learning Bite:

By definition, the event has to have had a clear beginning and end, so has “resolved” before presentation to hospital.

Learning Bite:

BRUE is a description of an event; not a disease entity in and of itself. 

The pathophysiology of BRUE is unknown, hence the term “unexplained”.

The presentation described above may occur due to an underlying medical cause, but this would then not be considered a BRUE by definition.

It is a diagnosis of exclusion – other causes should be considered in the history and examination.

Differential Diagnoses

This list is not exhaustive:

Physiological Transient choking/gagging, apnoea of prematurity
Cardiac Congenital heart disease, arrhythmias, prolonged QT
Gastrointestinal Gastro-oesophageal reflux
Respiratory Airway obstruction including inhaled FB, laryngomalacia, obstructive sleep apnoea, central sleep apnoea
Infection Whooping cough, URTI/LRTI, meningitis/encephalitis, UTI, gastroenteritis
CNS Head injury, epilepsy, structural cerebral abnormalities, neuromuscular disorders
NAI Inflicted injury e.g. drug ingestion, factitious illness, suffocation
Surgical Acute gastrointestinal obstruction
Metabolic/toxins Hypoglycaemia, hypocalcaemia, hypokalaemia, inborn errors of metabolism, intentional/non-intentional drug overdose

Clinical history

This should be taken from the parent/carer who witnessed the event.

  • General description of event to include:
    • Choking/gagging/vomiting
    • Awake/asleep (sleep-related breathing disorders include OSA and central sleep apnoea)
    • Position (supine/prone/side)
    • Muscle tone (stiff/floppy/normal)
    • Movement, incl. eyes (purposeful, repetitive)
    • Respiratory effort (incl. distress, SOB, pauses, apnoea)
    • Skin and lip colour (incl. cyanosis, pallor, plethora)
    • Duration and how it stopped (self-resolved/repositioned/stimulated/CPR)
    • Condition after event and whether back to normal
    • Preceding trauma or recent head injury
    • Any objects nearby that could cause suffocation


  • Feeding including when last fed, amount and type of feed and history of any reflux


  • Past medical history to include:
    • Gestational age (infants younger than 44 weeks can have apnoea of prematurity)
    • Perinatal history, including NICU/SCBU
    • Previous unexplained episodes
    • Previous resuscitation
    • Recent illness


  • Family history to include:
    • SUDI
    • BRUE in siblings
    • Cardiac problems including arrhythmias
    • Parental consanguinity


  • Social history


Gastro-oesophageal reflux is one of the commonest causes of symptoms similar to a BRUE presentation, causing symptoms via laryngospasm. It is an important one to exclude as it is a very treatable cause of a presentation similar to a BRUE, and may cause repeated episodes. Features from the history that are suggestive of it are:

  • Episode occurred whilst infant was awake and supine
  • Occurred during feeding or shortly after feeding
  • Regurgitation or vomiting at time of event
  • Obstructive apnoea (infant making respiratory efforts but not breathing successfully)

Learning Bite:

Always consider NAI (e.g. drug ingestion, factitious illness, suffocation), especially if there are multiple or changing versions of the history. Take a detailed social history to include cohabiting family members, whether there is smoking/drug use at home, any mental illness at home and any social work involvement with the family.



  • Full ABCDE assessment – consider differential diagnoses. Remember to test a capillary blood glucose.
  • Fully expose the child to check for bruising, bleeding from nose/mouth, torn frenulum and subconjunctival haemorrhage
  • Plot weight, length and head circumference
  • Note any dysmorphic features that might indicate underlying congenital abnormalities

Learning Bite

Always document examination findings clearly, including important negatives and normal variants such as mongolian blue spots. This documentation can be important as a point of reference if any concerns are raised in the future.

Patients are considered to be LOW risk if there are no worrying features from history or examination AND:

  • >60 days of age
  • Born >32 weeks’ gestation and have a corrected age of >45 weeks (or approximately >2 months)
  • No CPR given by trained practitioner
  • <1 minute duration
  • First event
  • No CPR by healthcare professional

These patients are unlikely to have a severe underlying disorder and the event is unlikely to recur. There is no known association between BRUE with low-risk features and the risk for Sudden Infant Death Syndrome (SIDS).

Any patients outside of this group are considered HIGH risk.

Please see PIER Network flow diagram4:

Learning Bite

“Corrected age” corrects for a baby’s prematurity. This is important to give an accurate assessment of developmental abilities, as a baby born at 28 weeks will not have developed and matured to the same degree as a baby born at term.

It is calculated as follows:

Corrected age = (Chronological i.e. Actual age) – (weeks of prematurity)

E.g. a baby who is 24 weeks at presentation to ED, but was born at 28 weeks’ gestation:
24 weeks – 12 weeks = 12 weeks

No investigations are required for LOW risk patients but some units may prefer to do a capillary blood gas and ECG as standard.

For HIGH risk patients do a capillary blood gas and ECG as a minimum, and keep these patients on a cardiorespiratory monitor. Be guided by your local guidelines regarding further serum blood tests and testing of nasopharyngeal aspirate.

Learning Bite

Those infants identified as low risk require minimal investigating and no prolonged observation.

  • ECG is to assess QT interval
  • Capillary gas is to assess blood glucose, bicarbonate and lactate to evaluate for metabolic disease
  • NPA is to assess for pertussis +/- RSV


LOW risk patients do not routinely need to be admitted but, in practice, often are for a period of cardio-vascular monitoring and to enable education and advice on BRUE for caregivers. This could be undertaken in the Emergency Department if there are adequate monitoring facilities and written discharge advice.

Discharge advice for the parent/caregiver if discharging from the Emergency Department should include the following:

  • Safe sleeping (see Lullaby Trust for printable resources)
  • Eliminating exposure to tobacco smoke
  • Infant BLS
  • Specific advice never to shake the infant in an effort to resuscitate them
  • GP follow up in the next 48 hours

HIGH risk patients need referral to Paediatrics for a 24-hour period of monitoring +/- investigations.

Parents and Caregivers can be signposted to this website for advice on how to perform basic life support.

  • Failure to exclude other differential diagnoses by careful history and examination. Remember, BRUE is a diagnosis of exclusion.
  • The potential to increase parental anxiety by the suggestion of CPR training. You may find that this is inappropriate to offer in some circumstances. Involve parents in the decision-making regarding evaluation, discharge and follow up of these children.
  • Remember to correct for prematurity and make sure the child has a corrected age of >45 weeks (this is approximately >2 months)
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  2. Farquarson S, Foster S. Brief Resolved Unexplained Event or BRUE (ALTE guideline update). NHS Greater Glasgow and Clyde Paediatric Guidelines, 2018. [cited 2024 May 21].
  3. Kondamudi NP, Virji M. Brief Resolved Unexplained Event. [Updated 2023 Aug 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. [cited 2024 May 21].
  4. Brief Resolved Unexplained Event (BRUE) – Paediatric Innovation, Education & Research Network [Internet]. [cited 2024 May 20].
  5. National Institute for Health and Care Excellence (NICE) | Bronchiolitis in children: diagnosis and management | Overview | [NG9] [Internet]. [cited 2024 May 20].