Diminished Function of Maintaining Cerebral Perfusion during Systemic Hypotension in Elderly Humans

Abstract

Abstract Background The study sought to test the hypothesis that the function of maintaining cerebral perfusion is diminished in elderly adults due to compromised cerebral autoregulation (CA) and cardiovascular function with aging. Methods Healthy elderly (n = 13, 68 ± 1 year) and young (n = 13, 26 ± 1 year) adults underwent a systemic-hypotension induced by rapid-deflation of bilateral thigh-cuffs after 3-min supra-systolic occlusion. The responses of heart rate (HR), mean arterial pressure (MAP), and blood flow velocity of the middle cerebral artery (VMCA) were determined. Cerebral vascular conductance (CVC) was estimated from mean VMCA/MAP. Duration and rate of the recovery from the nadir of MAP and VMCA were compared between the groups. Results Thigh-cuff occlusion-deflation elicited a similar hypotension (ΔMAP) and hypoperfusion to the brain (ΔVMCA) in the elderly and young groups. However, the time elapsed from the cuff-deflation to the nadir of MAP and VMCA (TΔ), and the recovery time from the nadir to reaching the respective baseline levels (TR) were significantly longer in the elderly subjects. There were significant differences between the groups in the response rates of HR, MAP and CVC following the cuff-deflation. Overall TR-VMCA was significantly explained by the response rates of the cardiac-factor, vasomotor-factor, and CVC-factor. However, the TR-VMCA/vasomotor-factor slope (-3.0 ± 0.9) was steeper (P = 0.046) than the TR-VMCA/cardiac-factor slope (-1.1 ± 0.4). The TR-VMCA/CVC-factor slope (-2.4 ± 0.6) was greater (P = 0.072) than the TR-VMCA/cardiac-factor slope; but it did not differ from the TR-VMCA/vasomotor-factor slope (P = 0.52). Conclusions Both CA and systemic mechanisms contributed to cerebral perfusion recovery elicited by systemic hypotension; and the vasomotor factor was dominant over the cardiac factor. Recovery from cerebral hypoperfusion is slower in the elderly adults because of the age-diminished rates of the CVC response and cardiovascular reflex regulation. Vasomotor-response mediated perfusion pressure seems more significant in maintaining cerebral perfusion during systemic hypotension.