Non-invasive Cerebrovascular Autoregulation Assessment Using the Volumetric Reactivity Index: Prospective Study
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This prospective study of an innovative non-invasive ultrasonic cerebrovascular autoregulation (CA) monitoring method is based on real-time measurements of intracranial blood volume (IBV) reactions following changes in arterial blood pressure. In this study, we aimed to determine the clinical applicability of a non-invasive CA monitoring method by performing a prospective comparative clinical study of simultaneous invasive and non-invasive CA monitoring on intensive care patients.
CA was monitored in 61 patients with severe traumatic brain injuries invasively by calculating the pressure reactivity index (PRx) and non-invasively by calculating the volumetric reactivity index (VRx) simultaneously. The PRx was calculated as a moving correlation coefficient between intracranial pressure and arterial blood pressure slow waves. The VRx was calculated as a moving correlation coefficient between arterial blood pressure and non-invasively-measured IBV slow waves.
A linear regression between VRx and PRx averaged per patients’ monitoring session showed a significant correlation (r = 0.843, p < 0.001; 95% confidence interval 0.751 – 0.903). The standard deviation of the difference between VRx and PRx was 0.192; bias was − 0.065.
This prospective clinical study of the non-invasive ultrasonic volumetric reactivity index VRx monitoring, based on ultrasonic time-of-flight measurements of IBV dynamics, showed significant coincidence of non-invasive VRx index with invasive PRx index. The ultrasonic time-of-flight method reflects blood volume changes inside the acoustic path, which crosses both hemispheres of the brain. This method does not reflect locally and invasively-recorded intracranial pressure slow waves, but the autoregulatory reactions of both hemispheres of the brain. Therefore, VRx can be used as a non-invasive cerebrovascular autoregulation index in the same way as PRx and can also provide information about the CA status encompassing all intracranial hemodynamics.
KeywordsCerebrovascular autoregulation Pressure reactivity index Non-invasive monitoring Ultrasonic time-of-flight measurement method Traumatic brain injury patients
Arminas Ragauskas and Vytautas Petkus initiated the research. Aidanas Preiksaitis, Saulius Rocka, Saulius Vosylius, and Erika Zubaviciute gathered the clinical findings of patients and prepared the study protocol and documents to obtain ethical approval. Vytautas Petkus, Romanas Chomskis, Solventa Krakauskaite, and Aidanas Preiksaitis gathered and processed patient monitoring data. Yasin Hamarat and Laimonas Bartusis performed statistical tests. Romanas Chomskis, Vytautas Petkus, Saulius Vosylius, and Aidanas Preiksaitis supervised equipment and software use while collecting monitoring data. Vytautas Petkus, Solventa Krakauskaite, Laimonas Bartusis, and Yasin Hamarat contributed to the writing of the manuscript. Arminas Ragauskas and Saulius Rocka supervised the preparation of study results and contributed to the final manuscript. All authors discussed the study results and approved the final version of manuscript.
Source of support
This research was supported by the Research Council of Lithuania (Grant No. MIP-087/2015) and European Commission FP7-HEALTH (Grant No. 602150).
Compliance with Ethical Standards
Conflict of interest
Arminas Ragauskas have ownership interests in Boston Neurosciences (Lexington, Massachusetts USA) which intend to commercialize the non-invasive cerebrovascular autoregulation monitoring technology. Arminas Ragauskas and Vytautas Petkus are inventors of apparatus and method of non-invasive cerebrovascular autoregulation monitoring. Vytautas Petkus, Romanas Chomskis, Aidanas Preiksaitis, Saulius Rocka and Arminas Ragauskas report grant and personal fees from Research Council of Lithuania (Grant No. MIP-087/2015). Aidanas Preiksaitis, Saulius Rocka and Arminas Ragauskas report grant and personal fees from European Commission FP7-HEALTH (Grant No. 602150).
Ethical approval was obtained from the Vilnius Regional Biomedical Research Ethics Committee (Protocol No. 158200-06-498-145, Protocol No. 2012-06-12, 158200-15-801-323, 2015-10-06 and Protocol No. 158200-16-854-364, 2016-07-12). A written informed consent was obtained from each patient or an appropriate relative.
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