Linearity and Non-linearity of Cerebral Autoregulation
Linearity and Non-linearity of Cerebral Autoregulation
Injured brain tissue supplied by a disturbed state of cerebral autoregulation (CA) is at risk
 of secondary ischemia, e.g. in patients with stroke, subarachnoid hemorrhage, intracerebral
 hemorrhage or bacterial Meningitis. Up to now, there is lack of a simple and easy to perform
 bed side test that would allow for to intervene when CA failure is indicated. For this
 purpose, we explore the dynamics of the interplay between blood pressure and cerebral blood
 flow velocity using transcranial Doppler ultrasound (or near infrared spectroscopy derived
 haemoglobin concentration changes) as a measure of CA. To describe these dynamics different
 mathematical models are used, but they all still need validation and proof of concept because
 these dynamics are poorly understood with respect to the factors which influence the
 composition of the mathematical models.

 Objectives: To what amount is CA disturbed in the different stroke subgroups ? Is a disturbed
 CA a risk factor of poorer outcome ?
We investigate which factors determine the dynamics of CA under the assumption that disturbed
 dynamics of the relation blood pressure (BP) - cerebral blood flow velocity CBFv) indicate a
 disturbed CA. Factors to be considered relevant are BP, blood carbon dioxide (CO2)
 concentration (measured as endtidal CO2 concentration), autonomic nervous system function
 such as heart rate, pulse pressure amplitude and baroreflex sensitivity, movement or
 psychological tasks, and in the patients the kind and the severity of the underlying disease.
 Via different mathematical models the effects of these variables on CBFv as the Output
 function is evaluated. The most frequently used approach is the use of Transfer functions.

 In the registry will include the patients with acute strokes hospitalized at our stroke
 center. We will include every stroke patient with any Kind and severity of stroke syndromes
 who gives informed consent and who has a so called temporal ultrasound window to insonate the
 middle cerebral artery. BP will be measure noninvasively by a Finapres device. Items
 registered are Age, gender, cerebrovascular risk factors, temperature, mean BP and ist
 variability on days 1-3, stroke classification using TOAST, Perfusion Computed Tomography and
 MRI, and at the time of the simultaneous recordings of CBFv and BP the endtidal CO2, mean BP,
 mean pulsatility index, and after Transfer function analysis coherence, gain and Phase in
 different frequency ranges
Inclusion Criteria:

 -  every typ of ischemic stroke of any severity

 -  presence of a "temporal bone window"

 Exclusion Criteria:

 -  Age < 18 years,

 -  pregnancy

 -  no informed consent.

 -  absence of a "temporal bone window"