Brief Resolved Unexplained Event

A brief resolved unexplained event is a sudden, brief (under 1 minute) and now resolved episode in an infant under 1 year, in which the observer reports at least one of: cyanosis or pallor; absent, decreased or irregular breathing; a marked change in tone; or an altered level of responsiveness. The term applies only when history and examination give no explanation.

It replaced the older term apparent life threatening event, which was too broad. The true incidence is uncertain because many events are unreported. Most infants are well on assessment, and serious underlying disease is found in only a small proportion.

Causes include gastro oesophageal reflux and swallowing dysfunction, respiratory infection (respiratory syncytial virus, pertussis), seizures, cardiac arrhythmia (long QT syndrome), airway anomalies, anaemia, metabolic disease, abusive head trauma, and periodic breathing or breath holding. No cause is found in many infants.

An infant is at lower risk when all of these apply: age over 60 days; gestation of 32 weeks or more with postconceptional age of 45 weeks or more; first event; duration under 1 minute; no resuscitation by a trained person; and no concerning findings in the history or examination.

Pathophysiology.

Mechanisms differ by cause. Immature control of breathing and swallowing, with reflux or secretions reaching the airway, can cause laryngospasm and apnoea. Seizures, arrhythmia and infection cause events through other routes.

• A frightening episode witnessed by the carer: colour change, limpness, choking, gagging or apnoea, with stimulation or resuscitation by the carer in some.
• By the time of assessment the infant is usually back to baseline, with normal vital signs and examination.
• Associated: feeding, cough, coryza, vomiting, fever or irritability in the preceding days.

Red flags.

• Age under 60 days, prematurity, recurrent events, or an event lasting 1 minute or longer.
• Bruising, bulging fontanelle, retinal signs, inconsistent history, or previous concern about abuse.
• Dysmorphism, hypotonia, abnormal growth, family history of sudden death or arrhythmia, or a previous unexplained infant death.
• Signs of infection, cardiac murmur, abnormal ECG, or focal seizures.

• Detailed history of the event (timing, relation to feeds and sleep, position, appearance, duration, intervention), birth and feeding history, family history, and social history.
• Full examination including growth, head circumference, fontanelle, skin, cardiovascular, respiratory and neurological systems, and fundi where indicated.
• For lower risk infants, no routine tests are needed. Continuous pulse oximetry for 1 to 4 hours, and a 12-lead ECG if available, are reasonable.
• For higher risk infants or any concerning feature: ECG, glucose, blood gas, bicarbonate, full blood count and CRP, respiratory viral and pertussis PCR, and urinalysis. Add toxicology, metabolic tests (ammonia, lactate, acylcarnitines), EEG, echocardiography, and neuroimaging or skeletal survey when specific concern exists.

Differential diagnosis. Gastro oesophageal reflux with aspiration, bronchiolitis, pertussis, seizures, arrhythmia, congenital heart disease, upper airway anomalies, inborn errors of metabolism, sepsis, abusive head trauma, poisoning and normal infant behaviour such as periodic breathing.

Lower risk infants.

• Observe with monitoring for a short period (1 to 4 hours), then discharge if well, after shared decision making with the family.
• Offer resuscitation training for carers, and explain the low likelihood of recurrence and of serious disease.
• Review feeding and sleeping practice, with safe sleep advice. Home apnoea monitors are not advised.

Higher risk infants.

• Admit for monitoring and focused investigation directed by the history. Treat the identified cause: antibiotics for sepsis, anticonvulsants for seizures (phenobarbital 20 mg/kg IV over 20 minutes, or levetiracetam 40 to 60 mg/kg IV), antiarrhythmic care, and treatment of reflux if aspiration is shown.
• Where abuse is suspected: skeletal survey, neuroimaging, ophthalmic examination and child protection referral without delay.

Monitoring. Follow up in a week for lower risk infants, with return advice for any further event.

Referral and escalation. Refer to paediatric cardiology for an abnormal ECG or family history of arrhythmia, to neurology for seizures, and to the child protection team for any concern about abuse.