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Cerebral O2 and CO2 transport in isovolumic haemodilution: compensation of cerebral delivery of O2 and maintenance of cerebrovascular reactivity to CO2

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posted on 2022-10-28, 11:30 authored by Jay M.J.R. Carr, Philip N. Ainslie, David B. MacLeod, Joshua C. Tremblay, Daniela Nowak-Flück, Connor A Howe, Michael StembridgeMichael Stembridge, Alexander Patrician, Geoff B. Coombs, Benjamin S. Stacey, Damian M. Bailey, Daniel J. Green, Ryan L Hoiland

 This study investigated the influence of acute reductions in arterial O2 content (CaO2) via isovolumic haemodilution on global cerebral blood flow (gCBF) and cerebrovascular CO2 reactivity (CVR) in 11 healthy males (age; 28±7 years: body mass index; 23±2 kg/m2). Radial artery and internal jugular vein catheters provided measurement of blood pressure and gases, quantification of cerebral metabolism, cerebral CO2 washout, and trans-cerebral nitrite exchange (ozone based chemiluminescence). Prior and following haemodilution, the partial pressure of arterial CO2 (PaCO2) was elevated with dynamic end-tidal forcing and gCBF measured with duplex ultrasound. CVR was determined as the slope of the gCBF response and PaCO2. Replacement of ~20% of blood volume with an equal volume of 5% human serum albumin (Alburex® 5%) reduced haemoglobin (13.8±0.8 vs. 11.3±0.6 g/dL; P<0.001) and CaO2 (18.9±1.0 vs 15.0±0.8 mL/dL P<0.001), elevated gCBF (+18±11%; P=0.002), preserved cerebral oxygen delivery (P=0.49), and elevated CO2 washout (+11%; P=0.01). The net cerebral uptake of nitrite (11.6±14.0 nmol/min; P=0.027) at baseline was abolished following haemodilution (-3.6±17.9 nmol/min; P=0.54), perhaps underpinning the conservation of CVR (61.7±19.0 vs. 69.0±19.2 mL/min/mmHg; P=0.23). These findings demonstrate that the cerebrovascular responses to acute anaemia in healthy humans are sufficient to support the maintenance of CVR.   


P.N.A. was funded by the Natural Sciences and Engineering Research Council of Canada and a Canada Research Chair. R.L.H. is funded through a Michael Smith Foundation for Health Research Trainee fellowship and a Craig H. Neilsen Foundation Postdoctoral Fellowship.


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Journal of Cerebral Blood Flow and Metabolism




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Carr, J.M., Ainslie, P.N., MacLeod, D.B., Tremblay, J.C., Nowak-Flück, D., Howe, C.A., Stembridge, M., Patrician, A., Coombs, G.B., Stacey, B.S. and Bailey, D.M. (2022) 'Cerebral O2 and CO2 transport in isovolumic haemodilution: Compensation of cerebral delivery of O2 and maintenance of cerebrovascular reactivity to CO2', Journal of Cerebral Blood Flow & Metabolism, p.0271678X221119442.

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  • Cardiff School of Sport and Health Sciences

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Mike Stembridge

Cardiff Met Research Centre/Group

  • Cardiovascular Physiology

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