Cerebrovascular carbon dioxide reactivity is intact in chronic kidney disease

Chronic kidney disease (CKD) is characterized by an elevated risk for cerebrovascular disease including stroke. One mechanism that may contribute to this heightened risk is an impairment in cerebrovascular carbon dioxide reactivity (CVR). We compared CVR between CKD patients stages III-IV and controls (CON) without CKD but matched for hypertension and diabetes status. CVR was measured via 5% CO2 inhalation followed by voluntary hyperventilation in 14 CKD and 11 CON participants while mean arterial pressure, end-tidal carbon dioxide, and middle cerebral artery blood velocity (MCAv) were measured continuously. CVR was quantified as the linear relationship between etCO2 and MCAv. We observed no difference in CVR between groups. Hypercapnic CVR: CKD = 1.2 +/- 0.9 cm/s/mm Hg, CON = 1.3 +/- 0.8 cm/s/mm Hg, hypocapnic CVR: CKD = 1.3 +/- 0.9 cm/s/mm Hg, CON = 1.5 +/- 0.7 cm/s/mm Hg, integrated CVR: CKD = 1.5 +/- 1.1 cm/s/mm Hg, CON = 1.7 +/- 0.8 cm/s/mm Hg, p >= 0.48. Unexpectedly, CVR was inversely related to estimated glomerular filtration rate in CKD (R2 = 0.37, p = 0.02). We report that CVR remains intact in CKD and is inversely related to eGFR. These findings suggest that other mechanisms beyond CVR contribute to the elevated stroke risk observed in CKD.