Blood pressure variability and cerebral autoregulation in acute ischaemic stroke
thesisposted on 15.12.2014, 10:31 by Suzanne L. Dawson
This thesis examines the haemodynamic changes that occur following acute ischaemic stroke with reference to beat-to-beat blood pressure (BP) levels and variability as well as static and dynamic cerebral autoregulation (CA).;Elevated 24h BP levels following acute stroke are associated with a poor outcome, but whether shorter durations of recording using beat-to-beat measurements or other BP parameters such as variability have the same prognostic significance is unknown. A single 10 minute non-invasive beat-to-beat BP monitoring period following acute cerebral infarction showed that increasing BP levels and beat-to-beat beat variability of mean arterial and diastolic BP were associated with a worse prognosis in terms of post ictal death/disability. These initial prognostic findings for BP variability might be explained if CA responses to rapid changes in systemic BP were impaired post stroke.;The second part of the thesis set out to measure dynamic and static CA using novel non-invasive techniques employing transcranial Doppler ultrasonography to measure cerebral blood flow velocity in response to non-pharmacologically induced pressor and depressor BP stimuli. The initial study found that in normal controls, the reproducibility and actual values obtained for the autoregulatory indices for both static and dynamic tests varied according to the BP stimulus used. As a result of these initial studies thigh cuff release was used as the stimulus for dynamic CA, and isometric hand grip and thigh cuff inflation as the stimuli for static CA. When the CA results for a study group of acute ischaemic stroke patients were compared to an age and sex matched control group dynamic CA was significantly reduced in the patients' affected and non-affected hemispheres, whereas static CA was unimpaired.