Rudolph's Pediatrics, 22nd Ed.

CHAPTER 119. 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 symptoms^2-7

• 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

3. Previous history of life-threatening events

4. Other previous medical problems including perinatal and neonatal problems (eg, prematurity, chronic lung disease, birth asphyxia)

5. History of life-threatening events or sudden infant death syndrome in other family members

6. Family history of inborn errors of metabolism

Ultimately, a judgment must be made regarding whether or not to categorize the infant as having experienced an ALTE. At one extreme is the judgment that the event was not severe enough to be considered a significant clinical problem (ie, it was not genuinely life threatening) or perhaps was clearly misinterpreted normal behavior. Alternatively, the nature of the described symptoms may be such that it is clear that the event was a genuinely life-threatening episode. In practice, however, in the absence of persistent symptoms or sequelae, it is difficult to be confident that a life-threatening event actually occurred.

SYMPTOMATIC INFANTS

In a relatively small proportion of infants who are evaluated as having experienced a possible life-threatening event, the infant is symptomatic when first seen by medical professionals. In addition to the assessment described above for asymptomatic infants, the opportunity to observe the nature and severity of persistent symptoms permits a greater degree of confidence when determining whether the episode was indeed life threatening. In some instances, the life-threatening nature of the event is clear. These include episodes in which the initial medical responders may need to initiate or continue resuscitative efforts, as well as those where the infant may be stable but still has symptoms such as respiratory distress, cyanosis, or loss of muscle tone. In other cases, the symptoms may be less clearly indicative of a life-threatening event but may point toward an underlying illness that could contribute to such an event, such as a seizure disorder.

EVALUATION

In cases in which an infant has indeed experienced a genuine life-threatening event, a careful investigation should be undertaken to identify a cause. Recognizing that most of the signs potentially relate to disturbed breathing, the initial focus in an evaluation is often directed at assessing respiratory function unless there are other cues in the history. Some of the most common potential causes of an ALTE relate to alterations in the respiratory control or mechanical function of the respiratory system. Examples include: respiratory infection, especially respiratory syncytial virus; seizures; tumors of the central nervous system; gastroesophageal reflux; drug-induced respiratory depression; poisoning; postanesthetic depression; upper airway obstruction; arrhythmias; inborn error of metabolism; and child abuse (Munchausen syndrome).^13-23 Based on the results of the history and physical examination, one should identify those conditions that require further investigation. Table 119-1 lists the tests commonly used in the evaluation of these infants. The most common diagnoses identified include infections, gastroesophageal reflux, and seizures. The relative proportion of each diagnosis may vary widely depending on the manner in which the ALTE criteria are applied or the referral pattern for a particular locale. For example, a given center might not use the ALTE designation in cases of suspected gastroesophageal reflux, or might receive few referrals of such cases. In addition, among infants who were born prematurely, while no specific etiology may be identified, ALTE episodes may be attributable to persistent apnea of prematurity. In some cases, it may be possible to document features that suggest an immature respiratory control based on physiological recordings; however, no prognostic value of these recordings has been demonstrated.^24,25

Table 119-1. Diagnostic Testing for Infants with Apparent Life-Threatening Events (ALTEs)

PROGNOSIS

Data are quite limited regarding the prognosis for infants who experience an ALTE. In rare cases, the ALTE itself results in persistent residual organ damage or neurodevelopmental impairment. Usually, however, infants have no obvious residual problems following the ALTE. Among infants in whom a cause for the ALTE is identified, the prognosis is determined by the particular diagnosis and by the ability to successfully provide treatment. In those cases in which ALTE is associated with prematurity, no further episodes are usually observed beyond the 43 to 44 weeks postconception age.¹² Although premature infants have a higher rate of sudden unexpected death than do term infants, the occurrence of apnea has not been shown to add to this risk.

Among infants with idiopathic apparent life-threatening event (ALTE), there is no convincing evidence that these infants are at increased risk for neurodevelopmental problems. Controlled follow-up studies have reported a slight increase in subtle neurologic abnormalities at 1 to 3 years post-ALTE and an increased frequency of breath-holding spells; however, no differences were observed at 10 years.^26-28 The rate of recurrent ALTE episodes or subsequent death is not well studied but appears to be less than 5%.²⁴ One common problem in understanding the prognosis of recurrent ALTE is the difficulty in disentangling child abuse from other causes. Although, the proportion of ALTE cases that may be attributable to child abuse is unknown, such cases have been well documented. Factors that increase the suspicion of child abuse include recurrent ALTE requiring cardiopulmonary resuscitation, history of sudden infant death syndrome (SIDS) or ALTE in siblings, and episodes that occur only in the presence of a single caretaker. Infants who have ALTE features suggestive of child abuse are at particularly high risk of recurrent episodes or death.

MANAGEMENT

There is considerable variation in the management of infants admitted for apparent life-threatening event–type diagnoses across US hospitals.²⁹ A general strategy for management of infants who have experienced a possible ALTE is provided in Figure 119-1. In the majority of cases, a careful history and physical examination will suggest that the event was either misinterpreted normal behavior or was relatively trivial (eg, minor choking episodes). In these cases, families need reassurance with a clear explanation of why no further intervention is needed and, if appropriate, need advice regarding childcare practices that will decrease the likelihood of recurrence (eg, proper feeding technique to reduce choking). Although there is often reluctance on the part of both families and clinicians to accept simple reassurance and counseling, there is no evidence that these episodes are associated with increased risk of morbidity or mortality. In this setting, undertaking an extensive workup that may be both intrusive and expensive, has little justification and may heighten, rather than reduce, anxiety. Given the lack of proven efficacy for intrusive and expensive management strategies, families and clinicians should be reassured that the vast majority of infants with a possible ALTE appear well within minutes and will have no subsequent significant problems. Alternatively, when findings are suggestive that the event was truly life-threatening, further evaluation, generally in the hospital, is warranted and will dictate subsequent management strategies.

INFANTS WITH IDENTIFIED CAUSE OF ALTE

If a specific cause for the ALTE is identified, then a treatment plan can be developed related to that specific entity. In general, to the extent such therapy is successful, home cardiorespiratory monitoring for recurrent ALTE is not warranted. However, if there is a concern that treatment will not be entirely successful, especially if presenting symptoms were severe, short-term cardiorespiratory monitoring may be useful. In these cases, a home monitor may be prescribed if clinicians feel that early caretaker intervention for events might be beneficial (ie, monitor use as part of a therapeutic approach) or a home monitor with memory may be prescribed to document the frequency of events, to distinguish true events from false alarms, and to document the nature of physiologic changes associated with events (ie, monitor use as a diagnostic strategy). Conversely, the use of a home monitor as a diagnostic or therapeutic tool has considerable limitations owing to constraints in current technology. Transthoracic impedance is used to detect respiratory effort, and there is a high risk of failing to detect obstructive apnea or having an alarm despite the presence of a breath (see Chapter 106).

INFANTS WITH NO IDENTIFIED CAUSE OF ALTE

The 1986 NIH Consensus Development Conference Statement, recommended that home cardiorespiratory monitoring or an alternative therapy is indicated for infants who have experienced one or more ALTEs requiring cardiopulmonary resuscitation or vigorous stimulation.¹ This recommendation was based on limited data available at that time suggesting the possibility of a high risk for death among these infants. Recent data from the Collaborative Home Infant Monitoring Evaluation (CHIME) study suggest that, at least among term infants, the risk of recurrent severe cardiorespiratory events or death may not be sufficiently high to justify a recommendation for home monitoring.¹² Given the heterogeneous nature of this population, a selective approach seems more reasonable. An American Academy of Pediatrics policy statement suggested that home cardiorespiratory monitoring may be warranted for infants who have experienced an ALTE in which the clinical picture suggests that the infant may be at increased risk for recurrent episodes.³⁰ Circumstances that would push one toward the use of a home monitor include persistent symptoms, neurologic impairment, a high level of family anxiety, an infant who was born prematurely, or a history that raises suspicion of child abuse.

FIGURE 119-1. Algorithm for management of an infant reported to have an apparent life-threatening event (ALTE).

MULTIPLE ALTES IN INFANTS

Infants who experience multiple events that meet criteria to be considered an ALTE are at very high risk for substantial morbidity including death.^31,32 In such cases, it is critical to identify the underlying cause, so that appropriate intervention can be initiated. The most common causes of recurrent ALTE include infections, seizures, gastroesophageal reflux, and child abuse. Of these, the most difficult and the most important to diagnose is child abuse. However, an appropriate index of suspicion and a careful look for features consistent with abuse (described earlier) can be lifesaving (see Section 4). In cases of multiple ALTE, where a specific diagnosis cannot be identified, use of a home monitor with memory may be of value in determining whether the events described are in fact genuine and, if they are genuine, to define physiologic changes that occur during the event.