A brief resolved unexplained event (BRUE) is a common reason for a caregiver to seek medical care for an infant, accounting for up to 0.5%-1% of all pediatric emergency department visits. It is not a specific physiologic diagnosis but a description of a clinical scenario. A BRUE occurs when an infant younger than 1 year experiences a sudden brief and resolved episode that may involve any of the following: apnea or breathing changes, cyanosis or pallor, marked change in muscle tone (hypertonic or hypotonic), and/or an altered level of responsiveness that cannot be explained by another diagnosis based on a thorough physical examination and history. This diagnosis was formerly known as an apparent life-threatening event (ALTE).

Infants who have had a BRUE are considered low risk for recurrence of a BRUE and are unlikely to have a serious life-threatening medical cause for the event if they meet all of the following low-risk criteria:

• The infant is older than 60 days; if premature, the infant was born at 32 weeks gestation or older and corrected gestational age at the time of the event is 45 weeks or older.
• The event was singular and lasted less than 1 minute.
• No cardiopulmonary resuscitation (CPR) was needed based on the assessment of a trained medical provider.
• There are no concerning features based on a thorough medical and social history, including but not limited to recent illness, significant past medical history, family history of sudden death / sudden infant death syndrome (SIDS) or similar event, or history of abuse or neglect.
• The patient has no prior history of a BRUE.
• The patient has a normal physical examination with normal, stable vitals over a period of observation of several hours with continuous pulse oximetry.

If an infant meets all of the above low-risk criteria, a period of brief observation (hours) and monitoring of vital signs are all that is required. Infants who do not meet the above criteria are not considered low risk and require further evaluation for potentially life-threatening causes for the event.