Ventilation and ventilatory pattern during sleep in aborted sudden infant death syndrome

To assess ventilatory control during sleep in infants at risk for the sudden infant death syndrome (SIDS), we made serial measurements of resting tidal volume (Vt), respiratory cycle time (Ttot), and the ventilatory changes resulting from inhalation of 2% CO2 in aborted SIDS infants in rapid eye movement and quiet sleep and compared them to a group of normal infants during the first 4 months of life. Ventilation was measured by the barometric method, and sleep was staged using electroencephalogram, electrooculogram, and electromyogram and behavioral criteria. Although resting instantaneous minute ventilation (Vt/Ttot) was virtually the same in both groups of infants, Vt tended to be smaller (by up to 50% in the first 2 months) and Ttot tended to be shorter in aborted SIDS than in normal infants in both rapid eye movement and quiet sleep. The increase in the mean Vt/Ttot with 2% CO2 is greater by about 5 to 20% in aborted SIDS than in normal infants at 3 and 4 months of age in both sleep states. These findings, together with our previous findings that aborted SIDS infants have an increase in heart rate and a shortening of the QT interval, provide indirect evidence that infants at high risk for SIDS may have increased sympathoadrenal activity.     

Defining the sudden infant death syndrome

Sudden infant death syndrome (SIDS) is a term that was first proposed in 1969 for a distinctive subgroup of unexpected infant deaths that occur during the postneonatal period with relatively consistent clinical, epidemiological, and pathological features. This term played an important role by focusing attention on a major category of postneonatal infant death, providing support to grieving families, and diminishing the guilt and blame characteristic of these deaths. Unfortunately, the application of this term has become increasingly controversial. Some have applied it too liberally, and others not at all. According to the definition proposed in 1969, despite slight changes suggested in 1989, SIDS remains a diagnosis of exclusion. Although this syndrome has several distinctive features, including age distribution and apparent occurrence during sleep, there has been reluctance to include these features in the definition. The problems created by the lack of an adequate definition are discussed. A 2-tiered approach is suggested, with a more general definition intended primarily for case management and death administration, and a more restrictive one intended primarily for research purposes, which distinguishes those deaths closely fitting the classic SIDS profile from those with one or more less typical features.     

Update on sudden infant death syndrome

PURPOSE OF REVIEW: With the introduction of the Back to Sleep campaign by the American Academy of Pediatrics in 1992, the incidence of Sudden infant death syndrome has decreased by almost 50%. Despite this success, SIDS continues to be the most common cause of unexplained infant death in Western countries. This article will briefly review the definition, etiology, and risk factors of SIDS. Attention will then focus on ways to target specific associated risk factors and at risk populations to promote a continued downward trend in the number of SIDS deaths. RECENT FINDINGS: Recent literature in SIDS research has focused on identifying infants at continued risk for SIDS. Children attending child care centers have an increased risk for SIDS, which is of particular concern as the number of infants in child care continues to rise. The reasons for this, along with strategies to decrease this risk, will be reviewed. In addition, the SIDS rate among black infants continues to be more than twice that of white infants. A review of the reasons for this disparity and ways to intervene through targeted campaigns will be discussed. Recent data has also suggested that the prevention of SIDS should not be an indication for use of home cardiorespiratory monitoring. The use of home monitoring may be warranted for some infants and will be reviewed. SUMMARY: Our jobs as pediatricians should be to ensure that the incidence of SIDS continues to decline. This can be done through parent education at each and every well child visit, lobbying to enforce state law to implement SIDS education campaigns for child care centers and within African-American communities, and continued review of the most current literature in SIDS research to keep ourselves current and well informed.     

Near-miss sudden infant death syndrome in eight infants with sleep apnea-related cardiac arrhythmias

Eight full-term infants between 3 and 8 weeks of age, who had had 24 to 48 hours of vague problems involving a congested upper airway and/or irritability, had a life-threatening respiratory episode at home, called a near-miss for sudden infant death syndrome event. Polygraphically monitored mixed apneas occurred in clusters during non-rapid eye movement (NREM) sleep with significant cardiac arrhythmias, predominantly sinus arrest. The cardiorespiratory problems continued during sleep in the following 8 to 12 weeks but did not recur after that time, and there were no long-term sequelae when the children were studied again 4 to 7 years later.     

Five cases of near-miss sudden infant death syndrome and development of obstructive sleep apnea syndrome

Five full-term infants were referred for "near miss" sudden infant death syndrome events, which occurred between 3 and 12 weeks of age. After a complete pediatric evaluation and 24-hour polygraphic monitoring, each infant was monitored at home with a cardiorespiratory monitor. Each was followed regularly (with repeat polygraphic recordings) up to 4 years of age. All five infants developed heavy snoring at night and symptoms of obstructive sleep apnea syndrome. The diagnosis of obstructive sleep apnea syndrome was confirmed by polygraphic recordings; surgery was recommended. Four of the five children underwent adenoidectomies between 3 and 4 years of age, and this significantly improved their condition. These five cases are the first polygraphically documented histories of the development of obstructive sleep apnea syndrome.     

Co-sleeping and sudden infant death syndrome]

Bedsharing has recently become a controversial subject. Some authors, mainly from North America, assign to bedsharing a positive effect on the efficacy and duration of breast-feeding. Moreover, it would protect against sudden infant death syndrome (SIDS). Conversely, other studies consider bedsharing as an additional risk factor for SIDS. From the literature data, there is some evidence for an increased risk of SIDS when bedsharing is associated with maternal smoking and alcohol consumption. Bedsharing cannot be recommended as an absolutely safe practice. Breast-feeding mothers should be aware of these potential hazards.     

Neuronal apoptosis in sudden infant death syndrome

Although evidence shows that victims of sudden infant death syndrome (SIDS) suffer repetitive episodes of hypoxemia, only subtle abnormalities have been found in their brains by light microscopy. The aim of the present study was to determine whether apoptosis, a form of cell death that can be triggered by hypoxemia and that leaves no scarring detectable by light microscopy, would be present in hypoxia-sensitive brain regions of SIDS victims. We looked for the presence of apoptosis with an in situ end-labeling method that detects DNA fragmentation. We studied 29 SIDS victims who were age-matched to nine control cases. We found significant neuronal apoptosis in 79% of the SIDS cases: 55% of the cases positive in the hippocampus and 96% positive in the brainstem. Whereas the distribution of apoptosis in the hippocampus was in hypoxia-sensitive subregions, the distribution in the brainstem was mostly in dorsal nuclei, including those involved with sensation in the face and position of the head (nucleus of the spinal trigeminal tract and vestibular nuclei). The control cases showed no significant apoptosis in the hippocampus and a mild degree in the brainstem in three cases. Our results indicate the occurrence of an acute insult at least several hours before death, an insult from which the infants had apparently recuperated. This suggests that SIDS victims suffered repeated apoptosis resulting in significant neuronal damage and, thus, functional loss in key brain regions. The involvement of specific nuclei in the brainstem may be linked to the fact that prone sleeping is a significant risk factor for SIDS. Enhanced neuronal death by apoptosis may thus have major implications for understanding the sequence of events leading to SIDS.     

Growth and the sudden infant death syndrome

Objective : To compare the growth curves based on measurements of body weight for male and female infants dying of sudden infant death syndrome (SIDS) with those of male and female controls. Methods : The data were drawn from a large case control study of SIDS carried out in New Zealand between 1987 and 1990. Results : The mean birthweight for the cases was 3049 g and for the controls 3526 g. The mean growth curves for the male and female controls were close to the 50th centile of growth charts used in New Zealand. The growth curve for the male cases diverged from that of the controls, being closer to the 25th percentile. The differences between the female cases and controls were less pronounced. The differences in weekly weight increments derived from the curves for the cases and controls for nine 4-week periods were not statistically significant after taking into account race, manner of feeding and maternal smoking for any 4-week period. Conclusions : SIDS cases were lighter at birth, but their growth velocity was normal postnatally.     

Hypothermia and sudden infant death syndrome.

We recently reported an association between recurrent episodes of severe apnoea requiring vigorous resuscitation for which no cause could be found and episodic hypothermia. Two similar cases are now reported that give further evidence of a link between hypothermia and acute life threatening episodes of apnoea.