ИСТИНА

Assessment of Cerebral Autoregulation and Optimal Mean Arterial Pressure with Near-Infrared Spectroscopy in Patients with Traumatic Brain Injury. Andrey Oshorova, I. Savina, DE Braginb,c,d a Department of Neurosurgical Intensive Care, Burdenko Neurosurgery Institute, Russia b Lovelace Biomedical Research Institute, USA c Department of Neurology, University of New Mexico School of Medicine, USA d Department of Neurosurgery, University of New Mexico School of Medicine, USA agvan2@gmail.com Background In patients with severe traumatic brain injury (TBI), simultaneous measurement of intracranial and arterial blood pressure (ICP and ABP) allows monitoring cerebral perfusion pressure (CPP) and assessing cerebral autoregulation (CA). CPP, a difference between ICP and ABP, is the net pressure gradient that drives oxygen delivery to cerebral tissue. CA is the ability of the cerebral vasculature to maintain stable blood flow despite changes in CPP and is an important homeostatic mechanism that protects the brain against injury. The pressure reactivity index (PRx), the moving Pearson correlation between the slow waves in ICP and ABP, has been most frequently cited in the literature over the past two decades as a tool for CA evaluation. However, in some clinical situations, ICP monitoring may be unavailable or contraindicated. In such cases, simultaneous mean arterial pressure (MAP) monitoring and Near-Infrared Spectroscopy (NIRS) can be used for CA assessment by the cerebral oximetry index (COx), allowing the calculation of the optimal blood pressure (MAPOPT). The cerebral oximetry index (COx) was calculated as the moving correlation between the slow waves of rSO2 and MAP. The PRx was calculated as a coefficient between slow waves of ICP and MAP. The right and left COx and PRx measurements from the onset of monitoring were binned into 5-mmHg increments of MAP for analysis. Optimal MAP for each side was defined as the MAP with the best autoregulation (i.e., MAP with the lowest COx and PRx). The right and left optimal MAP were averaged to define the individual patient optimal MAP. Aim The purpose of this study was to compare the regional oxygen saturation (rSO2)-based CA (COx) with ICP/ABP-based CA (PRx) in TBI patients and to compare the MAPOPT derived from both technologies. Materials and methods Three TBI patients were monitored at the bedside to measure CA using both PRx and COx. Patients were monitored daily for up to three days from brain injury. Averaged PRx and COx, as well as PRx and COx - based MAPOPT, were compared using Pearson’s correlation. Bias analysis was performed between these same CA metrics. Results Correlation between the averaged values of COx and PRx was R = 0.35, p = 0.15. Correlation between optimal MAP calculated for COx and PRx was R = 0.49, p < 0.038. Bland–Altman analysis showed moderate agreement with a bias of 0.16 ± 0.23 for COx versus PRx and good agreement with a bias of 0,39 ± 7.89 for optimal MAP determined by COx versus PRx. Discussion Non-invasive measurement of CA by NIRS (COx) is not correlated with invasive ICP/ABP-based CA (PRx). However, determination of MAPOPT using COx is correlated with MAPOPT derived from PRx. The obtained results demonstrate that NIRS-derived COx is not an acceptable substitute for ICP/ABP-derived PRx monitoring in TBI patients. But in some TBI cases, NIRS may be useful for optimal MAP determination.