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Description
Cerebral autoregulation can be assessed by several methods in the ICU. Two of the most used methods are the Autoregulation Index (ARI) and mean velocity index (Mxa), but their agreement varies across patient populations. This study aims to evaluate their relationship in critically ill patients.
Transcranial Doppler recordings from 15 patients (46 paired ARI–Mxa measurements; median age 72 years [IQR 61–75], 80% male) were analyzed, and a significant negative correlation between ARI and Mxa was emphasized (r = −0.74, 95% CI [−0.85, −0.57]). A linear regression estimated ARI as Y′ = 5.934 − 4.66 × Mxa, with an Mxa of 0.3 corresponding to an ARI of ~4.5, which is consistent with their respective impaired autoregulation thresholds.
These findings indicate a measurable, albeit variable association between ARI and Mxa, highlighting differences in their responsiveness to cerebral hemodynamic changes.
