Cerebral haemodynamic response to somatosensory stimulation in neonatal lambs

Nakamura, S, Walker, D and Wong, F 2017, 'Cerebral haemodynamic response to somatosensory stimulation in neonatal lambs', Journal of Physiology, vol. 595, no. 17, pp. 6007-6021.

Document type: Journal Article
Collection: Journal Articles

Title Cerebral haemodynamic response to somatosensory stimulation in neonatal lambs
Author(s) Nakamura, S
Walker, D
Wong, F
Year 2017
Journal name Journal of Physiology
Volume number 595
Issue number 17
Start page 6007
End page 6021
Total pages 15
Publisher Wiley-Blackwell Publishing
Abstract The neurovascular coupling response has been defined for the adult brain, but in the neonate non-invasivemeasurement of local cerebral perfusion using near infrared spectroscopy or blood oxygen level-dependent functional magnetic resonance imaging have yielded variable and inconsistent results, including negative responses suggesting decreased perfusion and localized tissue tissue hypoxia. Also, the impact of permissive hypercapnia (PaCO2 > 50 mmHg) in the management of neonates on cerebrovascular responses to somatosensory input is unknown.Using near infrared spectroscopy to measure changes in cerebral oxy- and deoxyhaemoglobin (oxyHb, deoxyHb) in eight anaesthetized newborn lambs, we studied the cerebral haemodynamic functional response to left median nerve stimulation using stimulus trains of 1.8, 4.8 and 7.8 s. Stimulation always produced a somatosensory evoked response, and superficial cortical perfusion measured by laserDoppler flowmetry predominantly increased following median nerve stimulation. However, with 1.8 s stimulation, oxyHb responses in the contralateral hemisphere were either positive (i.e. increased oxyHb), negative, or absent; andwith 4.8 and 7.8 s stimulations, both positive and negative responses were observed. Hypercapnia increased baseline oxyHb and total Hb consistent with cerebral vasodilatation, and six of seven lambs tested showed increased total Hb responses after the 7.8 s stimulation, among which four lambs also showed increased oxyHbresponses. Intwo of three lambs, thenegativeoxyHbresponse became apositivepattern during hypercapnia. These results show that instead of functional hyperaemia, somatosensory stimulation can evoke negative (decreased oxyHb, total Hb) functional responses in the neonatal brain suggestive of decreased local perfusion and vasoconstriction, and that hypercapnia produces both baseline hyperperfusion and increased functional hyperaemia.
Subject Animal Physiology - Biophysics
Keyword(s) cerebral blood flow
functional NIRS
neonatal brain
neurovascular coupling
somatosensory stimulation
DOI - identifier 10.1113/JP274244
Copyright notice © 2017 The Authors
ISSN 0022-3751
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