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Publication - Dr Jon Brooks

    Cerebral blood flow response to simulated hypovolaemia in essential hypertension

    an MRI study


    Neumann, SBB, Burchell, AE, Rodrigues, JCL, Lawton, CB, Burden, D, Underhill, M, Kobetić, MD, Adams, ZH, Brooks, JCW, Nightingale, AK, Paton, JFR, Hamilton, MC & Hart, ECJ, 2019, ‘Cerebral blood flow response to simulated hypovolaemia in essential hypertension: an MRI study’. Hypertension.


    Hypertension is associated with raised cerebral vascular resistance and cerebrovascular remodelling. It is currently unclear whether the cerebral circulation can maintain blood flow (CBF) during reductions in cardiac output in hypertensive patients thereby avoiding hypoperfusion of the brain. We hypothesised that hypertension would impair the ability to effectively regulate CBF during simulated hypovolaemia.
    In the present study, 39 participants (13 normotensive, 13 controlled and 13 uncontrolled hypertensive, mean age ± standard deviation 55 ±10 years) underwent lower body negative pressure (LBNP) at -20, -40 and -50mmHg to decrease central blood volume. Phase contrast MR angiography was used to measure flow in the basilar and internal carotid arteries, as well as the ascending aorta.
    CBF and cardiac output decreased during LBNP (P<0.0001). Heart rate increased during LBNP, reaching significance at -50mmHg (P<0.0001). There was no change in mean arterial pressure during LBNP (P=0.3). All participants showed similar reductions in CBF (P=0.3, between groups) and cardiac output (P=0.7, between groups) during LBNP. There was no difference in resting CBF between the groups (P=0.36).
    In summary, during reductions in cardiac output induced by hypovolemic stress, mean arterial pressure is maintained but CBF declines indicating that CBF is dependent on cardiac output in middle-aged normotensive and hypertensive volunteers. Hypertension is not associated with impairments in the CBF response to reduced cardiac output.

    Full details in the University publications repository