Sudden infant death syndrome and the modulation of neuropeptides released during shock

The role of infection and inflammation in sudden infant death syndrome

Sudden Infant Death Syndrome (SIDS) is the most common cause of post-neonatal mortality in the developed world. The exact cause of SIDS is likely to be multifactorial involving a critical developmental period, a vulnerable infant, and one or more triggers. Many SIDS infants have a history of viral illness preceding death. Prone sleep position, one of the leading risk factors, can increase airway temperature, as well as stimulate bacterial colonization and bacterial toxin production. Markers of infection and inflammation are often found on autopsy along with microbial isolates. Although the causal link between infection and SIDS is not conclusive, there is evidence that an infectious insult could be a likely trigger of SIDS in some infants.

Is shock a key element in the pathology of sudden infant death syndrome (SIDS)?

In developed countries, sudden infant death syndrome (SIDS) is the most common cause of death for infants between 1 month and 1 year of age. The etiology of SIDS is likely to be multifactorial, and current paradigms often describe three overlapping elements of risk. Those elements are a critical developmental period, a vulnerable infant, and one or more exogenous stressors. In the triple-risk model, SIDS infants are described as having an underlying vulnerability in cardiorespiratory control in the central nervous system during a critical period when autonomic control is developing. This vulnerability might affect the response to exogenous stressors, including prone sleeping position, hypoxia, and increased carbon dioxide. In the common bacterial hypothesis and fatal triangle, the focus is on the stressors. In the first, a combination of common respiratory infections can cause SIDS in an infant during a developmentally vulnerable period. This theory also includes 3 factors of vulnerability: a genetic predisposition, a vulnerable developmental age, and infectious stressors. In the fatal triangle theory, infection, inflammation, and genetics each play a role in triggering a SIDS fatality. From our work in an animal model, we have found that rat pups die from a combination of infectious insults during a critical time of development. This is exacerbated by perinatal nicotine exposure, a condition shown to alter the autonomic response in exposed offspring. We are proposing that shock and cardiovascular collapse is a key element that links these theories.

Evidence for infection, inflammation and shock in sudden infant death: parallels between a neonatal rat model of sudden death and infants who died of sudden infant death syndrome

This study compared pathological findings from a neonatal rat model of sudden death with those from 40 sudden infant death syndrome (SIDS) infants collected at autopsy. In the rat model, influenza A virus was administered intranasally on postnatal day 10, and on day 12 a sublethal, intraperitoneal dose of Escherichia coli endotoxin; mortality was 80%. Tissue samples from the animals and infants were fixed in formaldehyde, embedded in paraffin, and sections stained with hematoxylin and eosin. Tissues from the SIDS specimens were additionally cultured for bacteria and viruses; post-mortem blood samples were evaluated for signs of inflammation. All sections were examined by a pediatric forensic pathologist familiar with SIDS pathology. Comparisons between the rat model and the human SIDS cases revealed that both exhibited gross and microscopic pathology related to organ shock, possibly associated with the presence of endotoxin. Uncompensated shock appeared to be a likely factor that caused death in both infants and rat pups. Response to a shock-inducing event might have played an important role in the events leading to death. The similarities between the neonatal rats and the human cases indicate that further research with the model might elucidate additional aspects of SIDS pathology.

Association of sudden infant death syndrome with grossly deranged iron metabolism and nitric oxide overload

Sudden infant death syndrome (SIDS) occurs silently usually during sleep and, though remaining unexplained after autopsy, leaves footprints creating a pattern analogous to that which follows a flood of nitric acid (NO). These footprints in SIDS are associated with serious pathological changes, viz. elevated hepatic iron, bone marrow hyperplasia, hypomyelinated respiratory control centres, elevated lung immunoglobulins, cerebral hypoperfusion resembling lesions induced by chronic hypoxemia, ischemia, congenital heart disease and congenital myopathy. Hypoxia stimulates the immune response and the over-arousal of the immune response triggers a flood of NO. Adenosine triggers sleep. NO and adenosine are additive as dilators of coronary blood vessels. Blood pressure collapses. Selenium increases the activity of the enzyme ferrochelatase during incorporation of heme into cytochrome oxidase. NO binds to cytochrome oxidase, inhibiting respiration. When NO reaches dangerous levels, the cell turns on production of heme oxygenase. Heme is broken down to iron (Fe) carbon monoxide (CO) and bile pigments. NO has a huge affinity for hemoglobin which catalyses NO degradation to nitrate. Furthermore, NO is a product of smoke and SIDS incidence is higher in smoking mothers.