ABSTRACTBackgroundCerebral hypo‐perfusion during hemodialysis (HD) may contribute to cerebral ischemic lesions and atrophy in HD patients. Vascular disease and stiffness can impair cerebrovascular reactivity (CVR) in HD patients, placing them at higher risk for cerebral hypo‐perfusion during the hemodynamic stress of HD. We evaluated the relationship between CVR and change in cerebral perfusion during HD.MethodsIn a cohort of in‐center HD patients, we used hypercapnia to induce a change in cerebral blood flow velocity measured with transcranial Doppler to assess CVR. We used continuous cerebral oximetry during HD to measure a change in cerebral oxygen saturation (ScO2), calculating overall decline and the largest drop as markers of cerebral perfusion. We used multiple linear regression to assess the relationship between CVR and the ScO2‐associated endpoints.FindingsWe measured CVR in 42 HD patients and of those, 41 had the ScO2 measurements completed. The mean age was 58.5 (11.0) years, and most were male (90.5%, N = 38) with diabetes (59.5%, N = 25) and hypertension (87.5%, N = 36). The average CVR was 2.7 (1.6)%/mmHg. The average overall decline in ScO2 during HD was 2.2 (2.5)% and the average largest drop in ScO2 was 5.9 (2.8)%. CVR was negatively associated with both the largest drop in ScO2 (β = −0.67 95% CI [−1.20, −0.15], p = 0.01) and the overall decline in ScO2 (β = −0.62 95% CI [−1.09, −0.15], p = 0.01). Vascular disease was a risk factor for lower CVR (β = −1.21, 95% CI [−2.16, −0.26] p = 0.01).ConclusionsA lower CVR increases the risk for cerebral hypo‐perfusion during HD. Impaired CVR may be an important part of the pathophysiology of ischemic brain injury and cognitive impairment in HD patients.