Surfactant abnormalities in ALTE and SIDS

Abnormalities in the relative concentrations of the components of surfactant have been implicated in prolonged expiratory apnoea (PEA) and sudden infant death syndrome (SIDS). Controversy has, however, surrounded these findings, as they may be secondary to terminal life events. In this study the physical properties of surfactant were measured in children with recurrent apparent life threatening events (ALTEs), PEA, and SIDS. Bronchial lavage samples were obtained from 21 children with recurrent ALTEs, two SIDS victims, and 26 control patients. Lipid components were immediately elutriated from these samples with liquid chloroform. The physical properties of the extracted surfactant were studied on a Langmuir trough in which the area (A) of the monolayer was cycled continuously as the surface tension (gamma) was measured by the Wilhelmy method using a platinum 'flag'. The investigators performing these tests were unaware of the clinical diagnosis. Twenty one of 23 patients displayed abnormal physical properties while seven of 26 controls displayed similar abnormalities. These abnormalities were partially inverted hysteresis (figure of eight) loops and inverted (anticlockwise) loops that also generally exhibited less hysteresis. Of the 26 controls 20 exhibited a wide hysteresis pattern that cycled in a normal (clockwise) direction. These differences were significantly different. It is concluded that children with recurrent ALTEs have definable abnormalities in the physical properties of surfactant and that these findings may provide a sensitive means of identifying those at risk of recurrent ALTEs and SIDS.

[Smoking and sudden infant death]

Sudden Infant Death Syndrome (SIDS) is a death where autopsy and other examinations cannot explain the proper cause of death. Epidemiologic studies have recognized some risk factors, namely prone sleeping position, lack of breast feeding, overheating, and maternal smoking. In Denmark, the official recommendation concerning the prone sleeping position was changed in December 1991, and since then the incidence of SIDS has been diminished by approximately 60-70%. A large number of epidemiologic studies find that there is a possible risk for SIDS in connection with maternal smoking. The odds ratio for a pregnant smoker to lose an infant to SIDS is about 2-4. Thirty to forty percent of Danish women smoke during pregnancy, and about half of all children are exposed to passive smoking in their homes. These data show that about 20% of the SIDS cases are due to maternal smoking. Further information and individual advice to pregnant, smoking women and their partners are needed. The authors suggest that this advice should become part of the existing ante-natal care programme.

[Overheating and sudden infant death. Temperature regulation in relation to the prone position, the possible pathogenesis of sudden infant death]

The incidence of sudden infant death syndrome (SIDS) in Denmark varied in the period 1982-1991 between 1.5 and 1.9 per 1000 livebirths. In December 1991 recommendations concerning infants' sleeping position were published by The Danish National Board of Health in order to reduce the risk of SIDS. Babies were recommended to be placed in the supine or side position when sleeping. Parents have followed the guidelines. Most Danish infants are now sleeping on their back or in the side position. Simultaneously, the number of SIDS dropped from about 110 to 40 per year. The incidence decreased to 1.2 in 1992 and was further reduced in 1993 to 0.6 per 1000 live births. Referring to our knowledge of the infant's temperature regulation we discuss why the prone position is a risk factor for SIDS. The head is the site of up to 85% of heat loss in an infant in bed. Placed in the prone position, the infant is more likely to suffer a rise in body temperature, especially if this is combined with having a cold, being heavily wrapped and sleeping in a heated room. Preceding sudden death many infants are reported to have suffered from minor viral infections. These might per se increase the body temperature. Parents often wrap infants that have an infection too heavily, which in an infant sleeping in the prone position might increase the body temperature to a higher level than if sleeping supine. The body temperature influences the production of toxins from normal intestinal flora and from pathogenic bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)

Adjustment of cardiac repolarization to changing cycle length in healthy infants

This study describes the relation of cardiac repolarization (QT interval) to a changing heart rate (RR interval) in healthy infants, utilizing abbreviated electrocardiographic (ECG) recordings. A total of 105 limb lead ECG recordings were made in 53 infants of postconceptional age 30 to 52 weeks over a 5- to 15-minute period in order to obtain a heart rate variation of at least 20%. The QT and preceding RR intervals were measured during one cycle from each 3 second ECG segment (minimum 40 cycles) and the log QT-log RR relation was examined by linear regression statistics. Average RR was 387 ms (SD 42) and the average log QT/log RR slope 0.39 (SD 0.16). The slope correlated negatively with RR and was unassociated with age or sex. In 7 of the infants a single recording showed a QT-RR regression that failed to meet the 5% level of significance; 6 of these infants had additional tracings with a significant regression. When the log QT-log RR regression was studied in 20 continuous rhythm strips with spontaneous rate variation, the analysis of 9-32 consecutive cycles yielded an average slope of 0.13 (SD 0.07); in more than one-half of these strips the QT-RR association lacked significance at the 5% level. (ABSTRACT TRUNCATED AT 250 WORDS)

Acute fulminant, fatal coxsackie B virus infection: a report of two cases

Within a space of four months, between March to June 1993, medico-legal autopsies on 9 sudden infant deaths from natural causes were conducted at the Department of Forensic Medicine. Of these, 6 were due to unspecified interstitial pneumonitis or myocarditis (consistent with viral aetiologies), while 1 was attributed to adenovirus infection. The remaining 2 were due to fulminant Coxsackie virus (type B1) infection, where the post-mortem findings included leptomeningitis, myocarditis, florid interstitial pneumonitis, pancreatitis and focal hepatic necrosis. Coxsackie B viruses are often implicated in perinatal disease and, together with other viral infections, should be considered in the investigation of all sudden infant deaths.

[Obstructive apnea in premature and young infants]

The occurrence of obstructive apneas in premature and young infants is associated with a higher risk for SIDS. In order to assess the incidence of obstructive apnoeas in infants with different risk for SIDS pneumography was performed including the registration of the nasal air flow in 312 children: 69 preterm infants, 42 children after intensive care, one infant that later died of SIDS, 14 children after ALTE, 84 children after apnoeas observed by their parents, 25 siblings of SIDS-victims and 77 controls. Obstructive apnoeas were found in 24.6% of the preterm infants, in 28.5% of the children after intensive care, in 50% of the children after ALTE and in the one infant that later died of SIDS. Obstructive apnoeas however were registered only in 16.7% in the "apnoea-group", in 12% of the SIDS-siblings and in 11.7% of the controls. We therefore conclude that obstructive apnoeas which were observed more frequently in children with a higher risk for SIDS are of predictive value for the SIDS risk. Pneumography should therefore include the measurement of the nasal air flow. Home monitoring should be performed with devices that are able to assess bradycardias as indirect signs of obstructive apnoeas.

A novel mutation in medium chain acyl-CoA dehydrogenase causes sudden neonatal death

Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is the most common known genetic disorder of fatty acid oxidation. Most (approximately 80%) cases are homozygous for a single mutation: A to G replacement at nucleotide 985 (A985G). MCAD deficiency typically presents in the second year of life as hypoketotic hypoglycemia associated with fasting and may progress to liver failure, coma, and death. Prompt diagnosis and management may prevent long-term sequelae. MCAD deficiency was verified by analysis of urinary acylglycine and serum acylcarnitine species from two neonates referred for diagnosis. Full-length cDNA and MCAD exon 7 and 11 genomic clones were prepared for sequence analysis. Normal and mutant cDNAs were expressed in bacteria, and enzymatic activity was assayed by the ferricenium hexaflurophosphate method. Four compound heterozygote individuals from two unrelated families with A985G on one allele and a novel G to A mutation at nucleotide 583 (G583A) as the second mutant allele presented with MCAD deficiency in the first week of life. The expressed G583A mutant protein lacks enzymatic activity. This novel mutation, G583A, is associated with severe MCAD deficiency causing hypoglycemia or sudden, unexpected neonatal death. This previously unrecognized phenotype of MCAD deficiency may contribute significantly to preventable infant deaths.

Postnatal growth preceding sudden infant death syndrome

OBJECTIVE

To compare postnatal growth preceding the sudden infant death syndrome (SIDS) with that of age matched controls.

DESIGN

Retrospective case-control study. Each SIDS victim was matched with two controls on date of parental interview, postnatal age, and neighborhood. Clinical and demographic data were collected by parental interview and by review of medical records, and interval body weights were obtained from health visitors' records.

STUDY POPULATION

All infants dying of SIDS between 1 May, 1987 and 30 April, 1989 in a geographically defined region consisting of four health districts in Avon and North Somerset in southwest England. Seventy-eight of the 99 SIDS victims and 139 of 156 control infants were included in the final analysis.

RESULTS

There was no significant difference between SIDS victims and the controls in either of the two indices of postnatal growth which were analyzed. The mean growth rates (+/- 1 SEM) between birth and the last live weight (age equivalent weight for control infants) were 27.1 +/- 1.0 g/day for the SIDS cases and 28.3 +/- 1.5 g/day for the control infants. The mean growth rate (+/- 1 SEM) between the last two live weights were 31.5 +/- 2.9 and 24.9 +/- 2.1 g/day for the SIDS and control infants, respectively. Stratification of the infants by sex, gestational age, maternal smoking during pregnancy, breast versus bottle feeding, or age at death, did not result in any significant differences between SIDS and controls in either of the indices of postnatal growth rate. The 20 SIDS cases which were excluded from the final analysis did not differ from 78 whose data was analyzed, with regard to established SIDS risk factors, age at death, or postmortem weight.

CONCLUSIONS

No difference was found between the postnatal growth of SIDS victims and that of age matched control infants.

Ethnic differences in the sudden infant death syndrome: what we can learn from immigrants to the UK

AIMS

To compare the effect of potential maternal and birth factors on rates of sudden infant death syndrome (SIDS) within and between infants born to mothers of different ethnic groups.

METHODS

Routinely collected obstetric, child health data relating to 39,101 residents of three East London Districts born in 1989-1990 were obtained. These were matched with 312 death registration records to validate death and add registered cause of death. Mortality rates were calculated in the usual way, and using life-table methods.

RESULTS

These related to six ethnic groups, the largest of which were Anglo-European and Bangladeshi. Low birth-weight was the only factor associated with a greater risk of SIDS in all ethnic groups. Maternal smoking was uncommon amongst all Asian groups and African mothers, and rates of SIDS were uniformly low amongst non-smokers in all ethnic groups except Pakistanis. Adjustment for maternal age, parity, gestational age and birthweight would widen the differences between risk of SIDS observed between Anglo-Europeans and Bangladeshi infants.

CONCLUSIONS

The study has demonstrated that local data is more timely and of greater detail than that available nationally. Of the risk factors considered, smoking reported during pregnancy is the most commonly encountered and is particularly associated with deaths attributed to SIDS.

Endotoxemia in sudden infant death syndrome

Endotoxemia has been proposed as a significant cause of Sudden Infant Death Syndrome (SIDS). We examined postmortem sera from left and right heart samples of 21 SIDS cases (1989 definition) and 23 controls. The controls were < 1 year of age and had died suddenly and unexpectedly of infection, abuse, suffocation, blunt injury, or fire and smoke inhalation. Endotoxin was measured without knowledge of the clinical status by using a kinetic modification of the chromogenic limulus amoebocyte lysate assay. The SIDS cases had insignificant concentrations of endotoxin in serum, whereas some of the controls who experienced blunt injury, abuse, or severe infection exhibited moderately elevated concentrations. Postmortem interval and postmortem blood culture results did not materially affect endotoxin concentrations. Thus, we conclude that endotoxemia is not a substantial pathophysiologic event in SIDS.

[Sudden infant death syndrome--sudden and unexpected pediatric death]

Sudden infant death syndrome [SIDS] is the most common cause of death between the ages of one month and one year, affecting one to three infants of 1000 life births. SIDS is defined as a sudden death of an infant under one year of age, which remains unexplained even after performance of a complete postmortem examination, examination of the death scene and review of the case history. SIDS is unexpected, so parents have not had the opportunity to prepare for the death. Because SIDS remains unexplained, SIDS parents blame themselves for the death. For most families of SIDS victims, the best resource for help and support is a SIDS parent support group. Finally, risk factors and possible preventive measures are discussed.

Travel and changes in routine do not increase the risk of sudden infant death syndrome

We investigated the relationship between travel and changes in routine and the sudden infant death syndrome (SIDS) among 485 SIDS cases compared with 1800 randomly selected control infants. There was no increased risk of SIDS with travel. Special events, such as christenings, were not associated with an increased risk of SIDS. However, visits to and by friends or relatives were associated with a significantly reduced risk of SIDS after controlling for potential confounders (odds ratios = 0.70; 95% confidence interval = 0.52, 0.96). These findings may indicate less social support in SIDS cases.

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.