Impaired cerebral CO2 vasoreactivity: association with endothelial dysfunction
- 1 October 2006
- journal article
- research article
- Published by American Physiological Society in American Journal of Physiology-Heart and Circulatory Physiology
- Vol. 291 (4), H1856-H1861
- https://doi.org/10.1152/ajpheart.00014.2006
Abstract
Conflicting data exist on the role of nitric oxide (NO) in cerebral blood flow (CBF) autoregulation. Previous studies involving human and animal subjects seem to indicate that NO involvement is limited to the CO2-dependent mechanism (chemoregulation) and not to the pressure-dependent autoregulation (mechanoregulation). We tested this hypothesis in patients with impaired endothelial function compared with healthy controls. Blood pressure, heart rate, end-tidal Pco2, CBF velocities (CBFV), forearm blood flow, and reactive hyperemia were assessed in 16 patients with diabetes mellitus and/or hypertension and compared with 12 age- and sex-matched healthy controls. Pressure-dependent autoregulation was determined by escalating doses of phenylephrine. CO2 vasoreactivity index was extrapolated from individual slopes of mean CBFV during normocapnia, hyperventilation, and CO2 inhalation. Measurements were repeated after sodium nitroprusside infusion. Indexes of endothelial function, maximal and area under the curve (AUC) of forearm blood flow (FBF) changes, were significantly impaired in patients (maximal flow: 488 ± 75 vs. 297 ± 31%; P = 0.01, AUC ΔFBF: 173 ± 17 vs. 127 ± 11; P = 0.03). Patients and controls showed similar changes in cerebrovascular resistance during blood pressure challenges (identical slopes). CO2 vasoreactivity was impaired in patients compared with controls: 1.19 ± 0.1 vs. 1.54 ± 0.1 cm·s−1·mmHg−1; P = 0.04. NO donor (sodium nitroprusside) offsets this disparity. These results suggest that patients with endothelial dysfunction have impaired CO2 vasoreactivity and preserved pressure-dependent autoregulation. This supports our hypothesis that NO is involved in CO2-dependent CBF regulation alone. CBFV chemoregulation could therefore be a surrogate of local cerebral endothelial function.This publication has 45 references indexed in Scilit:
- Sympathetic activation restrains endothelium-mediated muscle vasodilatation in heart failure patientsAmerican Journal of Physiology-Heart and Circulatory Physiology, 2005
- Regional Impairment of Cerebrovascular Reactivity and BOLD Signal in Adults After StrokeStroke, 2005
- Inhibition of nitric oxide synthase does not alter dynamic cerebral autoregulation in humansAmerican Journal of Physiology-Heart and Circulatory Physiology, 2004
- l -Arginine Improves Diminished Cerebral CO 2 Reactivity in PatientsStroke, 2003
- Carbonic Anhydrase I Inhibition By Nitric Oxide: Implications For Mediation Of The Hypercapnia‐Induced Vasodilator ResponseClinical and Experimental Pharmacology and Physiology, 2000
- Weakness of Sympathetic Neural Control of Human Pial Compared With Superficial Temporal Arteries Reflects Low Innervation Density and Poor Sympathetic ResponsivenessStroke, 1998
- Autoregulation of Cerebral Blood Flow in Orthostatic HypotensionStroke, 1998
- High Glucose Concentrations Dilate Cerebral Arteries and Diminish Myogenic Tone Through an Endothelial MechanismStroke, 1997
- Spontaneous Cardiac Baroreflex in HumansHypertension, 1995
- Upper limit of cerebral autoregulation during development of hypertension in spontaneously hypertensive rats--effect of sympathetic denervation.Stroke, 1985