Intra-alveolar haemorrhage in sudden infant death syndrome: a cause for concern?

Background-The "Back to Sleep" campaign in 1991 resulted in a dramatic decr ease in the incidence of sudden infant death syndrome (SIDS). The proportio n of presumed SIDS deaths being actually suspicious deaths from airway obst ruction is likely to have become relatively greater. There is usually littl e pathological evidence to suggest smothering, but intraalveolar haemorrhag e appears to be more prominent in cases where interference with the airway is suspected. Aim-To attempt to quantify intraalveolar haemorrhage to see whether it coul d be used as a marker to distinguish between smothering/overlying and SIDS. Methods-Intra-alveolar haemorrhage was quantified using digital image analy sis on haematoxylin/eosin stained sections taken from the lungs of 62 conse cutive infants who had died suddenly and unexpectedly. Cases were initially classified according to the original cause of death. After quantitation, t he case histories were critically reviewed. Three pathologists independentl y made microscopic assessments of the degree of intra-alveolar haemorrhage in the first 24 cases to see whether these accurately reflected the quantit ative results. Results-73% of those infants with a history suggesting possible involuntary overlaying and 45% of those with a history suspicious of smothering had si gnificant intra-alveolar haemorrhage (> 5% of total lung surface area asses sed). From the history the cause of death in 11 cases initially classified as SIDS would better have been given as "Unascertained." Simple microscopic assessments underestimated the true extent of the haemorrhage in 33% (8/24 ). Conclusions-If a moderate degree (at least 5%) of pulmonary parenchymal hae morrhage is observed, this may be an indicator of airway obstruction for a significant period, either from overlaying or possibly smothering. The diag nosis of SIDS may be being used inappropriately in such cases.