A practical classification schema incorporating consideration of possible asphyxia in cases of sudden unexpected infant death

Abstract

Although the rate of the sudden infant death syndrome (SIDS) has decreased over the last two decades, medical examiners and coroners are increasingly unwilling to use the SIDS diagnosis, particularly when there is an unsafe sleeping environment that might pose a risk for asphyxia. In order to reliably classify the infant deaths studied in a research setting in the mixed ancestory population in Cape Town, South Africa, we tested a classification system devised by us that incorporates the uncertainty of asphyxial risks at an infant death scene. We classified sudden infant deaths as: A) SIDS (where only a trivial potential for an overt asphyxial event existed); B) Unclassified-Possibly Asphyxial-Related (when any potential for an asphyxial death existed); C) Unclassified-Non-Asphyxial-Related (e.g., hyperthermia); D) Unclassified-No autopsy and/or death scene investigation; and E) Known Cause of Death. Ten infant deaths were classified according to the proposed schema as: SIDS, n = 2; Unclassified-Possibly Asphyxial-Related, n = 4; and Known Cause, n = 4. A conventional schema categorized the deaths as 6 cases, SIDS, and 4 cases, Known Cause, indicating that 4/6 (67%) of deaths previously classified as SIDS are considered related importantly to asphyxia and warrant their own subgroup. This new classification schema applies a simpler, more qualitative approach to asphyxial risk in infant deaths. It also allows us to test hypotheses about the role of asphyxia in sudden infant deaths, such as in brainstem defects in a range of asphyxial challenges.

Fig. 1

The cause of death in this infant is classified as Group A, SIDS. The circumstances of mild asphyxia may or may not be present. Here the infant's head is turned to the side. He is on a firm mattress in a crib with no pillow

Fig. 2

The cause of death in this infant is classified as Group B, Unclassified Possibly Asphyxial-Related when any potential for an asphyxial death exists. The infant is sleeping in an adult bed with soft bedding and her head is found-face down in that bedding

Fig. 3

The cause of death is classified as Group E, Known cause of death, due to accidental asphyxiation. The large adult, compromised by alcohol, is completely overlaying the body of the infant

Fig. 4

SIDS is conceptionalized as a disorder of protective asphyxial challenge responses in which the vulnerable infant, due to brainstem pathology in neuronal networks that mediate responses to asphyxia, is compromised and even a mild asphyxial challenge causes death. At the other end of the spectrum, the asphyxial challenge Is so severe, that all infants, with or without underlying brainstem pathology, die