Epileptic seizure-induced hypoxemia in infants with apparent life-threatening events

OBJECTIVE

To describe the physiologic changes that occur during epileptic seizure (ES)-induced apparent life-threatening events (ALTE) and to provide an explanation for the mechanism whereby the hypoxemia characterizing these events occurred.

PATIENTS AND DESIGN

Six infants were retrospectively selected from a group of 17 because they had ALTE documented on physiologic recordings where the first change in signals was in the electroencephalogram (EEG). The 17 infants had clinical features suggestive of partial seizures (but normal standard EEGs) and were from a sample of 172 infants with recurrent ALTE. All 17 infants underwent continuous recordings of breathing, electrocardiogram (ECG), oxygenation, and EEG, but only in 6 was an ES-induced ALTE recorded and the physiologic changes described.

RESULTS

Twenty-three ALTE were documented in six infants. Events commenced with an abnormality in the EEG, followed by a decrease in SaO2 after a median interval of 27 seconds (range 2 to 147). Despite resuscitation, the median duration of severe hypoxemia (SaO2 < or = 60%) was 40 seconds (range 8 to 74). In 18 events (five infants) there was a median of four apneic pauses (range 1 to 9) preceding the decrease in SaO2 by a median duration of 24 seconds (range 3 to 48). The longest apneic pause per event lasted a median of 19 seconds (range 8 to 47). Breathing movements continued in five events (four infants), and expiratory airflow in one. Sinus tachycardia was found in 19 of the 23 events (six infants), but there were no cardiac arrhythmias.

CONCLUSIONS

ES in infants can manifest as ALTE and be accompanied by potentially life-threatening episodes of severe hypoxemia and apnea, despite a normal EEG between events.

Metabolic disease and sudden, unexpected death in infancy

The prevalence of metabolic disease in infants dying suddenly and unexpectedly is controversial. Most studies have centered on major pediatric institutes with appropriate facilities to study inherited metabolic disease. No studies have been reported from nonacademic centers. We have prospectively studied urine and blood organic and fatty acids from 58 consecutive infant deaths over a 1-year period in nonteaching hospital medical examiners' offices in the state of Illinois for evidence of metabolic disease. One infant was found to have medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, homozygous for the common A985G mutation. One had probable non-A985G MCAD deficiency based on the identification of cis-4-decenoic acid in blood and one had ethylmalonic-adipic aciduria. Thus, we found evidence that inherited metabolic defects are related to unexpected infant death in this population. These disorders are present in a significant minority of infants who probably would have been given the diagnosis of sudden infant death syndrome if they had not undergone metabolic evaluation. We recommend that all infants who have died suddenly and unexpectedly be regarded as high-risk candidates for metabolic disease and that all such deaths be appropriately investigated as part of the routine autopsy procedure.

Sudden infant and child death as a cultural phenomenon: a Tlaxcalan case study

THE Sudden Death of infants and young children (SICD) constitutes a recurring problem in all societies. In contemporary industrialized societies, many factors known to cause these deaths have been clarified and controlled. Yet, as an outcome of such things as unrecognized disease, accidents, so-called crib death, and parental neglect or abuse, the prevalence of SICD remains relatively stable even in contemporary Western societies (Adams et al. 1990; Campbell 1989; Kyle et al. 1990). The pathophysiology of these human tragedies has received much attention. However, the social, cultural, and psychiatric implications have been relatively neglected. In large part this is because in our secular culture these deaths are explained naturalistically; namely, as the result of disease, biological anomalies, or physiological failures, the meaning of which is not attributed to human or other worldly intervention. A result of this is that such deaths are usually deprived of a framework of meaning that has spiritual and existential connection to everyday affairs. An impersonal, natural way of explaining SICD often deprives the mourner of a meaningful cultural rationale that can facilitate emotional release and spiritual significance.

The role of infectious agents in sudden infant death syndrome

Epidemiological factors associated with susceptibility to respiratory infections are similar to those associated with Sudden Infant Death Syndrome. Here we review the evidence that respiratory pathogens might be involved in some cases of Sudden Infant Death Syndrome in the context of factors identified in epidemiological studies of cot deaths: the age range affected; mother' smoking; respiratory viral infections; immunisation status. Both laboratory and epidemiological evidence suggests that vulnerability of infants to infectious agents depends on interactions between genetic, developmental and environmental factors that contribute to colonisation by microorganisms, the inflammatory and specific immune responses and the infants' physiological responses to inflammatory mediators. A model is proposed to explain how microorganisms might trigger a series of events resulting in some of these unexpected deaths and discusses how the the present recommendations regarding child care practices might help reduce the numbers of Sudden Infant Death Syndrome cases associated with infectious agents.

Can superantigens trigger sudden infant death?

A majority of sudden infant death syndrome (SIDS) victims have respiratory or gastrointestinal infections prior to death. This has led to an investigation of the role of pathogenic bacteria and the potentially lethal toxins they produce as triggers for sudden infant death. A small group of bacteria have been consistently identified in SIDS victims as compared to controls, and remarkably, three of these produce superantigenic toxins. Superantigens exert a powerful effect on the immune system, stimulating T-cells, which subsequently induces the formation of large amounts of cytokines. Generation of an overwhelming inflammatory response may lead to death by shock, or other, as yet unrecognized effects of the toxin on the respiratory or cardiac systems. A SIDS/superantigen model is proposed which may explain many of the pathological characteristics of SIDS and establish quantifiable markers for SIDS.

Sudden infant death syndrome: a possible primary cause

The hypothesis that poisoning by phosphines, arsines and stibines might be the primary cause of sudden infant death syndrome (SIDS) was investigated. Most mattress materials contain phosphorus or antimony compounds as fire retardant additives. Mattress materials in areas affected by the warmth and perspiration of the sleeping infant were found to be naturally infected by the fungus Scopulariopsis brevicaulis which is thought to be capable of generating phosphines, arsines and stibines from materials containing phosphorus, arsenic or antimony compounds. These gases may cause anticholinesterase poisoning and cardiac failure in infants, but contributory factors include the prone sleeping position and overwrapping. In England and Wales, the progressive increase in SIDS between 1951 and 1988 seems to be related to increasing use of phosphorus and antimony compounds as fire retardents in cot mattresses.

[Sudden infant death syndrome (SIDS): risk conditions and intervention strategies]

The term SIDS describes the unexpected and unexplained death of an apparently well infant. After congenital anomalies, SIDS is the most common cause of infant death in the industrial countries and it is the leading cause of death among infants older than 1 month. Descriptive epidemiological studies have shown a winter excess of cases and a peak of age distribution at about 3 months of age. Although many theories have been proposed to explain the etiology (i.e. fatal toxaemia, autonomic dysfunction, abnormalities of respiratory or cardiovascular control), an underlying cause for SIDS has not been identified. There are, however, a number of factors consistently associated with an elevated risk, the strongest of which are maternal smoking or exposure to substances of abuse during pregnancy, overheating and overinsulation, artificial feeding and prone sleeping position. A fall in the rate of the SIDS can be reasonably expected from changes in these risk factors, from home monitoring of infants suffering a near-SIDS episode and of siblings of SIDS victims, and from parental education programmes.

Early neonatal sudden death or near death syndrome. An epidemiological study of 29 cases

Early neonatal sudden death syndrome (SIDS) is a rare but well known disease entity. Between January 1975 and December 1991, 29 full-term newborn infants delivered in our maternity unit and, considered healthy at birth, suffered early SIDS (n = 15) or early apparent life threatening events (ALTE) (n = 14). Data from the whole population of live full-term infants born in our hospital during the past five years have been used as a reference (n = 27,841). The general rate of early SIDS was 0.14 per 1000 (15/107,263). Combining early ALTE cases, the overall rate was 0.27 per 1000 (29/107,263). A postmortem examination was performed for all infants who died (20/29): no cause of death could be determined, and we did not observe a single case with evident sequelae. There were 9 deaths (31%) within the first hour after delivery and 12 deaths occurred in the early morning hours (04:00-08:00; RR = 3.76; p = 0.0008). The lowest incidence was in the spring (RR = 0.21; p = 0.03). There was a tendency for an increased incidence during the weekend and the summer. No influence of sex, maternal age, gestational age, infant weight presentation, delivery, anesthesia or presence of meconium-stained fluid was found. In our opinion, SIDS can take place even during the first hour of life and it is not possible to predict when a baby might be affected. Pediatrically trained caregivers, close observation by the mother during the first few days and resuscitation facilities in maternity wards may be the most important preventive measures to reduce the risk of early SIDS and the consequences of ALTE in the early newborn period.

Physical properties of bedding that may increase risk of sudden infant death syndrome in prone-sleeping infants

Soft bedding has been shown in epidemiologic studies to increase the risk for sudden, unexpected death in prone-sleeping infants. We compared the physical properties of conventional bedding to bedding from two sources: 1) bedding that covered the airways of victims of sudden infant death syndrome (SIDS) lying prone and face down at the time of death; and, 2) bedding associated with increased risk for SIDS in case-control studies (i.e. bedding filled with ti tree bark). Using simple mechanical models and the head from an infant mannequin, we measured the resistance to airflow, malleability, and capacity to limit CO2 dispersal of the bedding. We also describe a technique for quantifying bedding softness. The resistance and malleability were similar for the conventional bedding, the ti tree bedding, and the bedding from SIDS deaths (analysis of variance, p = 0.85 and 0.16). The ti tree bedding and the other bedding from SIDS cases differed from conventional bedding in two physical properties. Both groups were softer (p < or = 0.005) and limited CO2 dispersal to a greater degree (p < or = 0.009). The finding that increased capacity to limit CO2 dispersal is a consistent property of the bedding covering the airways of these SIDS victims and of bedding shown to be an epidemiologic risk factor for SIDS supports rebreathing of expired air as a mechanism underlying the association of certain kinds of bedding with SIDS.

Absence of ventilatory responses to alternating breaths of mild hypoxia and air in infants who have had bronchopulmonary dysplasia: implications for the risk of sudden infant death

Infants who have had bronchopulmonary dysplasia (BPD) are at an increased risk of sudden infant death syndrome. Because failure of the cardiorespiratory response to hypoxia is suggested to play a key role in sudden infant death syndrome, we tested the hypothesis that infants who have had BPD have a reduced respiratory chemoreflex response to hypoxia. We examined the reflex respiratory responses to breath-by-breath alternations in fractional inspired oxygen concentration in eight infants who had had BPD (mean gestation = 27 wk, mean postnatal age = 93 d) who were no longer on supplemental oxygen and compared the responses with those of 12 preterm infants who had not required supplemental oxygen or been mechanically ventilated since birth (mean gestation = 30 wk, mean postnatal age = 38 d). For test runs we alternated fractional inspired oxygen concentration through two gas delivery lines between 0.21 and 0.16 on a breath-by-breath basis, and for control runs we alternated the inspirate between the two gas lines with a fractional inspired oxygen concentration of 0.21 in each. Respiration was measured using inductance plethysmography infants with BPD showed no significant differences between test and control responses for any respiratory variable. In contrast, all respiratory variables in the preterm infants showed test responses significantly greater than control. We speculate that the "blunted" chemoreflex respiratory response seen in infants with BPD may predispose them to subsequent respiratory failure, but we do not known which component of the chemoreflex is impaired.

A sudden infant death like syndrome possibly induced by a benzodiazepine in breast-feeding

The cause of the 'sudden infant death syndrome' (SIDS) remains unknown. We describe a case in which a benzodiazepine unadvisedly taken by a mother might have been at least in part responsible for the death of her breast-fed 'at risk' daughter. Moreover, in this case, home monitoring as a preventive measure was not effective.

Melatonin increases cyclic guanosine monophosphate: biochemical effects mediated by porphyrins, calcium and nitric oxide. Relationships to infant colic and the Sudden Infant Death Syndrome

It is hypothesized that melatonin, by its actions on porphyrin and nitric oxide biosynthesis, produces an increase in cyclic guanosine monophosphate.

Neonatal shock

This review discusses the literature on neonatal shock published in 1993. Etiologies for shock including the role of enterotoxins in sudden infant death syndrome and the role of Streptococcus pyogenes in streptococcal toxic shock syndrome are discussed. The monitoring of cardiac function, oxygen consumption, and oxygen delivery in neonates with shock and in children after cardiac surgery are discussed. The physiology of shock including the metabolic and cytokine mediator responses to shock are outlined, and the various new treatment modalities are compared. These include conventional inotropic therapy, extracorporeal membrane oxygenation, and cytokine manipulation.

Population mixing and sudden infant death syndrome in England and Wales

BACKGROUND

Infections may be involved in some cases of sudden infant death syndrome (SIDS). Exposure to such infections is likely to differ considerably between areas depending on rates of population mixing. It is therefore possible that the geography of SIDS will reflect that of population migration.

METHODS

For 403 local authority districts in England and Wales the number of SIDS deaths in the first year of life and the number of livebirths during the period 1979-1983 were abstracted from published sources. Districts were classified by levels of in-migration using data from the 1981 Census and observed and expected numbers of SIDS deaths were compared for areas experiencing different rates of in-migration.

RESULTS

A significant association (P < 0.001) was found between SIDS deaths and rates of long distance migration into districts. In the group with the highest rate of long distance in-migration the ratio of observed to expected SIDS deaths was 62% greater than in the group with the lowest rate of in-migration. This association was strengthened after adjustment for social class and illegitimacy. A weaker, but statistically significant, association was found for shorter distance in-migration.

CONCLUSIONS

It is concluded that geographical variations in SIDS deaths in England and Wales are strongly associated with differences in rates of population mixing as measured by migration. The findings support the hypothesis that population mixing, by its influence on exposure to infections, may be a significant factor in the aetiology of SIDS.

Sudden infant death syndrome and infant mortality in aboriginal and non-aboriginal infants

The aim of this study was to investigate sudden infant death syndrome (SIDS) in the context of total infant mortality for Aboriginal and non-Aboriginal infants. Deaths for infants born in Western Australia from 1980 to 1988 inclusive were ascertained from a total population data base. Infant mortality rates and rates by period and cause of death were calculated for both populations. Aboriginal infants had a mortality rate three times that for non-Aboriginal infants (23.6 cf. 7.9 per 1000 live births) and both populations showed a similar rate of decline in mortality over the study period. There were differences in the proportion of deaths occurring neonatally and postneonatally in the two populations. In terms of SIDS, 21% of the deaths in Aboriginal infants occurred neonatally compared with 7% for non-Aboriginal infants. The overall cause of infant death distribution differed significantly between the two populations (P < 0.001). During the study period, Aboriginal infants showed a significant increase in deaths due to SIDS and a significant decrease in those due to birth defects and low birthweight. These results suggest it would be useful to review the pathology and diagnosis of sudden unexplained death in infancy.

Sudden infant death syndrome in aboriginal and non-aboriginal infants

This study, based on routinely recorded data, was designed to compare the epidemiology of sudden infant death syndrome (SIDS) in Aboriginal and non-Aboriginal infants in Western Australia (WA). All cases of SIDS occurring in infants born in WA from 1980 to 1988 were included in the study. There were 66 Aboriginal (6.1 per 1000 live births) and 337 non-Aboriginal (1.7 per 1000 live births) infants who died from SIDS. It was found that there was a significant linear increase in the Aboriginal SIDS rate over the study period while the non-Aboriginal rate remained relatively constant. For non-Aboriginal infants, there was an elevated risk of SIDS for young maternal age, single marital status and male gender but this was not found for Aboriginal infants. There was a significant difference in the age at death distribution for the two populations. Low birthweight and preterm birth were risk factors for both Aboriginal and non-Aboriginal infants. There may be differences in the aetiology and/or classification of SIDS between the two populations.

Polygraphic evaluation of night-to-night variability in sleep characteristics and apneas in infants

The study was designed to evaluate whether results of a single overnight recording session are sufficient for the study of sleep profiles and detection of apneas in infants, or whether it would be beneficial to extend the recording period. Nineteen infants were recorded during successive nights. Eight of the 19 infants were studied after an idiopathic apparent life-threatening event, whereas the other 11 were healthy. There were 13 boys and six girls, with a median age of 11 weeks (range 5-36 weeks). All infants were recorded polygraphically during 2 nights, and 11 were recorded during 3 successive nights. No significant difference was observed between any of the following variables, regardless of the number of nights for which the recording was performed: total recording time, total sleep time, delay in sleep onset, time awake, percent of rapid eye movement or nonrapid eye movement sleep, mean respiratory rates, density and duration of central, obstructive or mixed apneas. The frequency of obstructed breathing events for each infant did not differ significantly from 1 night to the next. The present study indicates that under adequate study conditions, recordings of a single night can reliably describe the frequency of central and obstructive apneas in infants.