Studying cerebral hemodynamics and metabolism using simultaneous near‐infrared spectroscopy and transcranial Doppler ultrasound: a hyperventilation and caffeine study

Physiological Reports

Runze Yang⁵  Julien Brugniaux¹  Harinder Dhaliwal³  Andrew E. Beaudin⁴  Misha Eliasziw²  Marc J. Poulin¹ 

[1] Faculty of Medicine, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada;Department of Public Health and Community Medicine, Tufts University School of Medicine, Boston, Massachusetts, USA;Department of Clinical Neurosciences, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada;Department of Physiology and Pharmacology, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada;Department of Radiology, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada

关键词: Brain;    near‐infrared spectroscopy;    transcranial Doppler ultrasound;   

DOI  :  10.14814/phy2.12378

来源: Wiley

【 摘 要 】

Abstract

Caffeine is one of the most widely consumed psycho-stimulants in the world, yet little is known about its effects on brain oxygenation and metabolism. Using a double-blind, placebo-controlled, randomized cross-over study design, we combined transcranial Doppler ultrasound (TCD) and near-infrared spectroscopy (NIRS) to study caffeine's effect on middle cerebral artery peak blood flow velocity (Vp), brain tissue oxygenation (S_tO₂), total hemoglobin (tHb), and cerebral oxygen metabolism (CMRO₂) in five subjects. Hyperventilation-induced hypocapnia served as a control to verify the sensitivity of our measurements. During hypocapnia (~16 mmHg below resting values), Vp decreased by 40.0 ± 2.4% (95% CI, P < 0.001), while S_tO₂ and tHb decreased by 2.9 ± 0.3% and 2.6 ± 0.4%, respectively (P = 0.003 and P = 0.002, respectively). CMRO₂, calculated using the Fick equation, was reduced by 29.3 ± 9% compared to the isocapnic-euoxia baseline (P < 0.001). In the pharmacological experiments, there was a significant decrease in Vp, S_tO₂, and tHb after ingestion of 200 mg of caffeine compared with placebo. There was no significant difference in CMRO₂ between caffeine and placebo. Both showed a CMRO₂ decline compared to baseline showing the importance of a placebo control. In conclusion, this study showed that profound hypocapnia impairs cerebral oxidative metabolism. We provide new insight into the effects of caffeine on cerebral hemodynamics. Moreover, this study showed that multimodal NIRS/TCD is an excellent tool for studying brain hemodynamic responses to pharmacological interventions and physiological challenges.

【 授权许可】

CC BY   
© 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

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