Apparent Life-Threatening Events and SIDS
Michael J. Corwin
The assessment and management of infants who are described as having had a frightening, perhaps life-threatening, event is a challenging problem for clinicians. The fear that the infant may experience additional episodes, perhaps a fatal one, heightens the anxiety level of both families and medical professionals.
DEFINITION
An apparent life-threatening event (ALTE) was defined in 1986 at a National Institutes of Health (NIH) Consensus Development Conference on Infantile Apnea and Home Monitoring as an “episode that is frightening to the observer and that is characterized by some combination of apnea (central or occasionally obstructive), color change (usually cyanotic or pallid but occasionally erythematous or plethoric), marked change in muscle tone (usually limpness), choking, or gagging.” In addition, it was recommended that previously used terminology such as “aborted crib death” or “near-miss sudden infant death syndrome (SIDS)” be abandoned to avoid implication of a causal association between this type of spell and SIDS.1
Apparent life-threatening events were described in the Consensus Development Conference statement as a “chief complaint that describes a general clinical syndrome.” This general clinical syndrome may be secondary to a specific diagnosis or may remain idiopathic despite a thorough evaluation. The definition of an apparent life-threatening event appears straightforward; however, in practice, the decision regarding whether or not an infant experienced an ALTE can be extraordinarily difficult for clinicians. Although more than 20 years have passed since the adoption of the ALTE definition, the published literature regarding the epidemiology, clinical course, and prognosis of ALTE remains limited, and there is no evidence that these events arise from any single mechanism. Nor is there evidence that the manifestations represent a consistent pattern. Factors that contribute to the difficulty in studying infants who experience ALTE episodes include the following:
• Marked heterogeneity of clinical presentation
• Lack of signs or symptoms during initial assessment by medical professionals
• Parents or other caretakers who have been very frightened and have difficulty accurately describing signs or symptoms2-7
• Possibility that some signs or symptoms are fabricated or inflicted
INCIDENCE
Data regarding incidence of ALTEs are limited. Their incidence is estimated to be 0.05% to 1% in population-based studies.8-11 Some perspective on the occurrence of idiopathic ALTE can be obtained from the Collaborative Home Infant Monitoring Evaluation (CHIME study), which was conducted at five medical centers (located in Cleveland, Toledo, Chicago, Los Angeles, and Honolulu) during the mid-1990s. This study included a systematic review of infants who presented with diagnoses consistent with ALTE and found that a typical urban medical center hospital provides care for about one case of possible ALTE each week and that approximately 20% of such cases will be considered an idiopathic ALTE.12
CLINICAL PRESENTATION
ASYMPTOMATIC INFANTS
Most commonly infants are no longer experiencing respiratory or circulatory dysfunction by the time they are first seen by medical professionals. Even in cases in which an emergency medical team has been called, the signs commonly have resolved by the time emergency medical technicians arrive. In some cases, during a routine well-child visit, a parent may describe an event that was witnessed days or weeks in the past.
Among the most difficult tasks for the clinician is to identify the events that the infant actually experienced. The ability of the caretakers to provide an accurate history is diminished by the fact that they may have been frightened to the point of panic. The situation may be further confounded by circumstances such as a dark room, clothes or covers obscuring the view of the infant, or inexperience evaluating infant behavior.
The first step is to try to establish whether the symptoms were indeed life-threatening or, as is often the case, are consistent with normal behavior or common minor symptoms. To this end, it is important to ascertain the following:
1. Characteristics of the event
• Was the infant making breathing efforts? If so, was there anything observed that might suggest obstruction of the airway? This information helps to identify episodes of airway obstruction and, on further questioning, determine if there is an obvious explanation (eg, foreign body, airway secretions, food), or if further evaluation may be necessary.
• What was the longest period that the infant was not making breathing efforts? Infants normally have irregular breathing patterns. It is not unusual for parents to express a concern because they noticed a 10- to 15-second pause in breathing. Such pauses are not unusual and should not be a cause for concern unless accompanied by other symptoms.
• Were there changes in the infant’s color? Reports of the baby turning blue (ie, cyanosis) are consistent with a genuine life-threatening event. However, it is important to distinguish perioral cyanosis from generalized cyanosis. Infants described as having turned red or who appear pale are unlikely to have experienced a genuine life-threatening event.
• Was the infant asleep or awake? If the child is awake and alert, airway obstruction is more likely to be the cause.
• Was the infant crying or making other noises during the episode? Color changes associated with vigorous crying (ie, turning red or blue in the face) may scare parents but are generally not life-threatening events.
• Were there abnormal body movements or changes in the infant’s muscle tone? Genuine life-threatening events frequently are associated with changes in muscle tone. Loss of tone is most common. However, normal infants who are sleeping may also appear hypotonic. Alternatively, families may describe body movements consistent with seizure activity.
• Was the episode associated with feeding or emesis? This association may suggest gastroesophageal reflux, problems with feeding technique, swallowing dyscoordination, or possible airway obstruction.
• How long did the symptoms persist and what intervention was provided? Symptoms that resolve within 30 to 60 seconds, especially if no or minimal intervention was provided, should generally not be considered life-threatening. In cases in which substantial intervention is provided, it is important to consider that a frightened caretaker may have provided more intervention than required.
2. Current health status of the infant, including acute illnesses (eg, respiratory infections), chronic health problems (eg, neurologic problems, presence of gastroesophageal reflux, congenital abnormalities), and medications
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