Sudden Infant Death Syndrome Workup

Updated: May 16, 2022
  • Author: Lynn Barkley Burnett, MD, EdD, JD; Chief Editor: Kirsten A Bechtel, MD  more...
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Approach Considerations

An infant who is discovered lifeless may be transported by the family or by first-response personnel to the nearest hospital emergency department (ED). In a growing number of cases, when signs of death are obvious, the infant's death may be declared at the scene by first responders. Local medical examiner or coroner protocol should be followed in either instance. In many jurisdictions, specific infant death investigation guidelines exist and should be followed by prehospital or ED staff when an infant death has occurred.

A diagnosis of sudden infant death syndrome (SIDS) is established by excluding recognizable causes of sudden unexplained infant death (SUID). The necessary data set includes information obtained from the scene of death, infant and family medical and social history, and autopsy examination. Guidelines for the autopsy examination, including gross and microscopic dissections, and the role of toxicologic, microbiologic, radiographic, and other special procedures, are detailed by Krous and others. [114]

After careful analysis of information obtained from the complete postmortem evaluation, including death scene and historic information, SIDS emerges as the single leading cause of death among unexpected deaths in infancy; however, alternative diagnoses are identified in as many as 15-25% of SUIDs. The principal non-SIDS categories of SUID are as follows:

  • Infectious diseases

  • Metabolic abnormalities

  • Environmental factors

  • Structural (congenital) cardiac, respiratory, and central nervous system (CNS) lesions

If the infant is seen after an apparent life-threatening event (ALTE), workup includes appropriate blood and urine tests, as well as radiography and computed tomography when warranted. A 12-lead electrocardiogram (ECG) should be obtained. Electroencephalography (EEG) should be considered if indicated by findings from the history or physical examination. Patients younger than 2 months and those with significant evidence of infection should have a complete septic workup, including lumbar puncture and empiric antibiotics.


Laboratory Studies

For a living patient, initial laboratory studies include a complete blood count (CBC), electrolyte concentrations, and urinalysis.

A rapid bedside glucose reading should be obtained, followed by serum determination of glucose if indicated. Hypoglycemia, which is common in sepsis, may cause a confusing presentation. Hypocalcemia, hypomagnesemia, and hyperkalemia may cause respiratory dysfunction. Blood urea nitrogen (BUN), creatinine, phosphate, or serum ammonia tests may be helpful. Specific metabolic studies may be indicated if the patient is hypoglycemic, acidotic, or hyperammonemic.

Toxicologic screening can be helpful if exposure to medications (potentially intentional) or drugs of abuse is suspected. In many jurisdictions, toxicologic screening of serum and vitreous electrolyte analysis are routinely performed as part of the postmortem evaluation. If not routinely performed, obtain appropriate specimens and retain them for potential analysis.

A sepsis workup, with blood and urine culture, should be performed, though sepsis is unlikely in the absence of suggestive findings (eg, fever). Pertussis and chlamydial cultures should be obtained when appropriate. Respiratory syncytial virus (RSV) infection should be considered, particularly in very young infants or premature infants with respiratory symptoms. Stool may be sent for clostridial culture and for botulinum toxin testing, particularly if hypotonia is found. Infant botulism is probably a more common possibility than is generally believed.

Arterial blood gas determination may be helpful for infants who are severely ill or who have persistent symptoms on presentation. This may reveal metabolic acidosis that cannot be explained in any other way than by clearance of a large lactic acid load from a clinically significant apparent life-threatening event (ALTE). Metabolic acidosis raises the possibility of sepsis or metabolic deficiencies. Blood and urine toxicology screens and a carbon monoxide level test are appropriate in many cases.


Radiography and Computed Tomography

Whole-body radiographs may be obtained to evaluate for evidence of skeletal trauma. Special coned-down radiographic views may be necessary to further delineate subtle metaphyseal corner fractures of the long bones seen with nonaccidental forms of trauma.

A chest x-ray is indicated in most cases. The presence of fractures in a child younger than a year, irrespective of the site, should prompt a thorough investigation to exclude child abuse. It is extremely difficult to fracture the ribs of an infant during resuscitation; however, fractures do occur with relative ease when an infant’s thorax is grasped abnormally.

Anteroposterior and lateral soft tissue films of the neck should be obtained if upper airway obstruction is suspected. A barium swallow may be ordered if indicated by history or physical examination.

Radiographs and computed tomography (CT) scans of the skull may be indicated if abuse is suspected or if signs of increased intracranial pressure are present.



In a series of 800 consecutive cases of SUID, [115] 6% of the infants had a neuropathologic cause of death. Almost all had clinical histories or gross brain findings at autopsy suggesting the cause of death. In only 2 cases (< 1%) did brain histology alone determine the cause of death in the absence of a "neurologic history" or clearly evident macroscopic abnormalities.

In the absence of macroscopic abnormalities or a suggestive clinical history, formal histologic examination of the brain rarely determines the cause of death in SUID. A significant clinical history or the presence of abnormal gross brain findings should prompt a standardized histologic study of formalin-fixed brain tissue; the yield of histologic abnormalities is increased in these circumstances.