Clinical autonomic research : official journal of the Clinical Autonomic Research Society
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The time preceding brain death is associated with complex dysregulation including autonomic dysfunction that may compromise organ perfusion, thus inducing final organ failure. In this study, we assessed autonomic function in patients prior to brain death. ⋯ The increase in BPs, in sympathetically mediated BP-LF-powers, and in the RRI-LF/HF-ratio suggests prominent sympathetic activity shortly before brain death. Prefinal sympathetic hyperactivity might cause final organ failure with catecholamine-induced tissue damage which impedes post-mortem organ transplantation.
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Baroreflex sensitivity (BRS) is an important prognostic index in cardiovascular diseases, however, its use is complicated by different methods difficult to compare and standardize, often providing conflicting results. We tested whether the simple ratio of RR interval to systolic blood pressure global variabilities (assessed by standard deviations) is a reliable measure of BRS, by measuring the agreement with six established methods. In addition, we tested whether high-pass filtering of data, by removing slow non-baroreflex-mediated fluctuations, could improve the agreement between different BRS methods. ⋯ The new method intercepts the mean information of all other methods better than any other method, hence providing a simple, easy to standardize (no mathematical constraints) and yet robust and reliable BRS estimate. High-pass filtering markedly improves the agreement of all methods, without loss of sensitivity, and could be routinely used in clinical trials, to provide comparable BRS estimates.