Open AccessDynamic onset response of the internal carotid artery to hypercapnia is blunted in children compared with adults
Author(s) -
Tallon Christine M.,
Talbot Jack S.,
Smith Kurt J.,
Lewis Nia,
NowakFlück Daniela,
Stembridge Mike,
Ainslie Philip,
McManus Ali M.
Publication year - 2022
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.14814/phy2.15406
Subject(s) - hypercapnia , internal carotid artery , medicine , vasodilation , middle cerebral artery , cardiology , heart rate , anesthesia , cerebral blood flow , hemodynamics , blood flow , blood pressure , ischemia , acidosis
Intracranial blood velocity reactivity to a steady‐state hypercapnic stimulus has been shown to be similar in children and adults, but the onset response to hypercapnia is slower in the child. Given the vasodilatory effect of hypercapnia on the cerebrovasculature, assessment of vessel diameter, and blood flow are vital to fully elucidate whether the temporal hypercapnic response differs in children versus adults. Assessment of internal carotid artery (ICA) vessel diameter (ICAd), blood velocity (ICAv), volumetric blood flow ( Q ICA ), and shear rate (ICA SR ) in response to a 4 min hypercapnic challenge was completed in children ( n = 14, 8 girls; 9.8 ± 0.7 years) and adults ( n = 17, 7 females; 24.7 ± 1.8 years). The dynamic onset responses of partial pressure of end‐tidal CO 2 (P ET CO 2 ), Q ICA , ICAv, and ICA SR to hypercapnia were modeled, and mean response time (MRT) was computed. Following 4 min of hypercapnia, ICA reactivity and ICAd were comparable between the groups. Despite a similar MRT in P ET CO 2 in children and adults, children had slower Q ICA (children 108 ± 60 s vs. adults 66 ± 37 s; p = 0.023), ICAv (children 120 ± 52 s vs. adults 52 ± 31 s; p = 0.001), and ICA SR (children 90 ± 27 s vs. adults 47 ± 36 s; p = 0.001) MRTs compared with adults. This is the first study to show slower hypercapnic hyperemic kinetic responses of the ICA in children. The mechanisms determining these differences and the need to consider the duration of hypercapnic exposure when assessing CVR in children should be considered in future studies.