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Cardiovascular responses to three simple, provocative tests of autonomic activity in sleeping infants
C Harrington1, T Kirjavainen, A Teng
1David Read Laboratory, University of Sydney, Sydney 2006, New South Wales, Australia. cth@med.usyd.edu.au
Insights
At 3 months, infants demonstrate adult-like cardiovascular autonomic control responses to challenges like head-up tilting. This suggests mature neural regulation is developing, offering insights into infant autonomic development.
Area of Science:
- Physiology
- Developmental Biology
- Autonomic Neuroscience
Background:
- Defective cardiovascular autonomic control is linked to sudden infant death syndrome.
- Understanding normal autonomic development in infants is crucial but limited by noninvasive measurement challenges.
Purpose of the Study:
- To investigate the normal development of cardiovascular autonomic control in infants.
- To characterize infant cardiovascular responses to physiological challenges.
Main Methods:
- Studied 12 infants (13 ± 2 weeks) using noninvasive continuous blood pressure monitoring.
- Assessed cardiovascular responses to 45-degree head-up tilting, cold face test, and loud noise during sleep.
Main Results:
- Infants exhibited rapid biphasic heart rate and blood pressure responses to head-up tilting, similar to adults.
- Responses to cold face and noise were less pronounced.
- Full recovery of cardiovascular parameters occurred within 20 seconds post-stimulus.
Conclusions:
- By 3 months, infants display adult-like cardiovascular autonomic responses to postural challenges.
- The rapid onset of these responses suggests involvement of non-baroreceptor neural inputs.
- This study provides normative data on infant autonomic development.
Abstract:
Whereas defective cardiovascular autonomic control has been implicated in the sudden infant death syndrome, relatively little is known about the normal development of autonomic control, due to the inability to measure blood pressure in infants noninvasively. We studied 12 normal infants [age: 13 +/- 2 (SD) wk] using a noninvasive method of continuous blood pressure recording and examined the cardiovascular responses to 45 degrees head-up tilting, a modified cold face test, and a loud noise. In head-up tilting, in both slow-wave sleep and rapid eye movement sleep, all infants displayed a rapid biphasic heart rate response (mean increase of 16% and mean decrease of 21%) and blood pressure response (mean increase of 16% and mean decrease of 16%), with a return to pretest values within 20 s. Both ice and noise caused a less pronounced biphasic response. In conclusion, at 3 mo, infants show the adult pattern of response to postural challenge. The short latency of the response suggests that neural inputs, apart from baroreceptors, are involved in the initial phase of the response.