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Autonomic dysfunction at different ambient temperatures in infants at risk of sudden infant death syndrome
1Department of Paediatrics, Rotunda Hospital, Dublin 1, Republic of Ireland.
Insights
Infants experiencing apparent life-threatening events (ALTE) show more autonomic dysfunction than healthy infants. This suggests autonomic function testing could help evaluate infants at risk for sudden unexpected death.
Area of Science:
- Pediatrics
- Autonomic Neuroscience
- Infant Health
Background:
- Sudden Infant Death Syndrome (SIDS) and apparent life-threatening events (ALTE) are significant concerns in infant mortality.
- Autonomic nervous system dysfunction is a potential contributing factor to these events.
- Understanding autonomic responses in high-risk infants is crucial for risk assessment.
Purpose of the Study:
- To assess and compare autonomic function in infants with a history of ALTE, cyanotic attacks, or SIDS-exposed healthy infants versus healthy controls.
- To investigate the relationship between autonomic dysfunction and environmental factors like ambient temperature.
- To determine the clinical utility of autonomic function testing in high-risk infant populations.
Main Methods:
- Heart rate and blood pressure responses to postural changes (horizontal to upright) were measured in four infant groups.
- Testing was conducted at varying ambient temperatures (20°C, 25°C, 30°C).
- Autonomic function was evaluated using heart rate variability (R-R interval max/min ratio) and blood pressure fall percentage.
Main Results:
- Healthy control infants exhibited minimal autonomic dysfunction during postural changes.
- Infants with a history of ALTE demonstrated significantly higher rates of abnormal heart rate responses and blood pressure falls across tested temperatures.
- One infant with ALTE experienced an abnormal autonomic response prior to a fatal SIDS event.
Conclusions:
- Autonomic dysfunction is more prevalent in infants with a history of ALTE.
- Autonomic function testing, particularly heart rate and blood pressure responses to postural changes, may be a valuable clinical tool for identifying infants at increased risk of sudden unexpected death.
- Further research into autonomic regulation in infants is warranted to improve risk stratification and prevention strategies.
Abstract:
Autonomic function was assessed by measuring the heart rate and blood pressure responses to a change from the horizontal to upright posture at various ambient temperatures in four groups of infants aged 8-12 weeks: 30 infants who had suffered a well-defined unexplained apparent life-threatening event (ALTE); 8 infants who had suffered a cyanotic attack; 24 healthy infants with a sibling who had died from sudden infant death syndrome (SIDS); and 17 healthy infants. Autonomic dysfunction was uncommon in the control group; no infant showed an abnormal heart rate response to postural change (R to R interval maximum/minimum ratio less than 1.0) and a postural fall in blood pressure of greater than 10% occurred in only 1 infant. In contrast, in the ALTE group 9 of 26, 9 of 30, and 4 of 22 infants showed an abnormal heart rate response and 20 of 26, 14 of 30, and 10 of 22 a greater than 10% fall in blood pressure on postural change at 20 degrees C, 25 degrees C, and 30 degrees C, respectively. 1 ALTE infant died of SIDS 14 h after showing an RR max/min ratio of 0.8 and a postural fall in blood pressure of 11% and 14% at 20 degrees C and 30 degrees C. Autonomic function testing should become part of the clinical evaluation of infants at high risk of a sudden unexpected death.