Dynamic cerebral autoregulation in CVR testing Conclusions Weight adjusted infusion of ACZ to test CVR affects dCA parameters, but by no means exhausts dCA. It is therefore doubtful that maximal CVR is achieved this way. Statements about the function of cerebral blood flow control, like maximal reserve or reserve capacity, should always be interpreted in reference to the method that was used. Characterizing dCA based on transfer function analysis of ABP to CBFV changes has the advantage that no provocation is needed and adverse effects are minimal. The poor negative correlation between CVR and phase angle supports the notion that different mechanisms are involved, which interact in some way. DCA seems to depend on the “flow state” i.e. the overall “baseline” diameter of the peripheral cerebrovascular arterioles. Further studies should be directed to uncover the physiological mechanisms contributing to dCA, CVR and their relationships. In particular interaction between CVR and dCA should be studied also in a control group. Acknowledgements The authors thank Prof. R.B. Panerai (University of Leicester, UK) for his valu- able contributions to the manuscript. References 1. Aaslid R, Lindegaard KF, Sorteberg W, and Nornes H. Cerebral auto- regulation dynamics in humans.Stroke20: 45-52, 1989. 2. Bamford J, Sandercock P, Jones L, and Warlow C. The natural history of lacunar infarction: the Oxfordshire Community Stroke Project.Stroke 18: 545-551, 1987. 3. Blaber AP, Bondar RL, Stein F, Dunphy PT, Moradshahi P, Kassam MS, and Freeman R. Transfer function analysis of cerebral autoregulation dynamics in autonomic failure patients.Stroke28: 1686-1692, 1997. 4. Dahl A, Russell D, Rootwelt K, Nyberg-Hansen R, and Kerty E. Cerebral vasoreactivity assessed with transcranial Doppler and regional cerebral blood flow measurements. Dose, serum concentration, and time course of the response to acetazolamide.Stroke26: 2302-2306, 1995. 5. Demolis P, Florence G, Thomas L, Tran Dinh YR, Giudicelli JF, Seylaz J, and Alkayed NJ. Is the acetazolamide test valid for quantitative assess- ment of maximal cerebral autoregulatory vasodilation? An experimental study.Stroke31: 508-515, 2000. 55
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