SLOW RECOVERY OF CEREBRAL PERFUSION DURING HYPOTENSION IN ELDERLY HUMANS
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Purpose: Aging affects the cardiovascular function. This study tested the hypothesis that aging diminishes cerebral perfusion during hypotension challenge. Methods: Healthy elderly (n=13) and young (n=13) adults signed a consent form that was approved by IRB at UNTHSC. Heart rate (HR), mean arterial pressure (MAP), and cerebral blood flow velocity of the middle cerebral artery (VMCA) were continuously measured during systemic hypotension, which was induced by rapid-deflation of bilateral thigh-cuffs after 3-min supra-systolic occlusion. This hypotension elicited a transient-decrease in VMCA (ΔVMCA) and a reflexive-increase in HR (ΔHR). Time duration reaching the nadir of MAP and VMCA (T0) and the rate of the recovery response (TR) were compared between the groups. Results: Cuff deflation after occlusion to the legs significantly decreased MAP (ΔMAP) which elicited significant hypoperfusion to the brain in both groups. Although ΔMAP and ΔVMCA were not statistically different between the groups, both T0 and TR for MAP and VMCA were significantly longer in the elderly group. T0 and TR were shorter for ΔVMCA than ΔMAP, suggesting the presence of cerebral autoregulation, which evoked an early recovery of ΔVMCA from its nadir, and also explained an early completion of VMCA recovery before MAP restoration. In addition, the rates of ΔMAP and ΔHR during recovery were diminished with aging, which explained a prolonged recovery of cerebral perfusion. Conclusion: We conclude that aging diminishes the function of maintaining cerebral perfusion during hypotension, which is associated with age-impaired cerebral intrinsic factor and systemic function.