TABLE 1128 Differential Diagnosis of Acute Life Threatening Episodes

ALTE is not a diagnosis. It is simply a description of a characteristic clinical presentation. The usual age of occurrence is 2 to 3 months, but ALTE can occur at any age. Approximately 1 to 3 percent of infants in the general population are reported to experience ALTEs. The incidence is increased among infants who die of sudden infant death syndrome (SIDS) to about 5 to 6 percent. It can be reassuring to families that only about 1 of 20 SIDS cases occurs in the population who experience ALTE and, except for the most severe ALTE episodes, fewer than 1 to 2 percent of these infants succumb to SIDS. Most infants presenting with the history of ALTE have had relatively mild events and probably are not at increased risk of subsequent infant death compared with general population. Data do indicate a high risk of subsequent infant death following more severe ALTE presentations. The risk of subsequent infant death among all infants who experience an ALTE probably is 1 to 2 percent, but the risk increases to 8 to 10 percent for the relatively rare subgroup of infants who present with ALTE occurring during sleep and who are perceived to require some form of cardiopulmonary resuscitation. Those who experienced more than one such severe episode requiring either cardiopulmonary resuscitation or vigorous stimulation were reported in one study to have a 28 percent subsequent mortality rate despite the prescription of home monitors.

An ALTE may be caused by anything that could give the impression that the infant is extremely ill and in danger of dying. The most common general categories of the causation for ALTEs and their prevalence among ALTE infants are infection (5 to 40 percent, depending on the season), gastroesophageal reflux (GER) and other causes of laryngeal chemoreceptor stimulation (20 percent), seizures and other neurologic disorders (15 to 20 percent), and idiopathic (40 to 60 percent). Because most infants who have significant GER do not experience ALTEs, establishing the diagnosis of GER does not prove that it is the cause of ALTE. An unusually strong laryngeal chemoreceptor reflex can significantly increase an infant's susceptibility to ALTE due to GER, even with only minor reflux. This reflex is stimulated by acid or nonisotonic fluids, and the reflex response is apnea, bradycardia, and central pooling of blood.

Another type of ALTE, infantile breath-holding response, is also known as prolonged expiratory apnea or infantile syncope. Normal infants, both premature and full term, often perform a Valsalva maneuver in response to pain or fright, during vigorous activity, and during crying, coughing, and defecation. This maneuver normally decreases minute ventilation but is usually without consequence. However, some infants perform prolonged Valsalva maneuvers that persist until cyanosis, unconsciousness, and even seizures develop. These spells are presumed to be a more severe version of the simple breath-holding spells in which a crying child holds his or her breath until cyanosis develops but resumes breathing. Severe breath-holding spells have been estimated to occur in up to 5 percent of normal children at some time before 6 years of age.

There is no routine evaluation for ALTE. In general, after obtaining vital signs and history and performing a physical examination, further diagnostic testing should be individualized, depending on initial findings and clinical suspicions. If the infant appears to have cardiovascular and respiratory symptoms at the time of presentation, a very careful history should be taken and physical examination performed. If at all possible, a detailed description of the infant at the time of discovery, the specific stimulation and resuscitation measures used, and the infant's response should be obtained directly from those present at the time. Great care must be taken to ensure that the terms used by lay observers to describe the event are interpreted appropriately by the physician. It is useful to determine whether the infant has been chronically ill or essentially well. A report of several days of poor feeding, temperature instability, or respiratory or gastrointestinal symptoms suggests an infectious process.

Reports of "struggling to breathe" or "trying to breathe" imply airway obstruction. Association of the episode with the feeding implies uncoordinated swallowing, GER, or airway obstruction. Episodes that typically follow crying may be related to breath holding. Association of the episode with sleeping may also suggest GER or apnea of infancy. Attempts should be made to determine the duration of episode, but this is often difficult. The physician should also search for past medical problems and any family history of such problems. In addition to a normal, careful physical examination, particular focus should be directed toward the neurologic examination, observation of breathing during sleep and feeding, and evidence on cardiac examination of pulmonary hypertension or structural cardiac abnormalities.

Most infants who present acutely after an ALTE should be hospitalized for monitoring and further evaluation. Some episodes occur in clusters; if they occur in the hospital, observation by medically trained observers may help clarify the severity and cause of the episodes, and availability of trained medical personnel may be necessary for resuscitative efforts. In addition, the family and caretaker may be extremely anxious about the vulnerability of their infant and may benefit from reassurance, assessment, and counseling.3 ,5 ^M9,6. ,6 and 62

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