Romanas Chomskis

Association of Severe Traumatic Brain Injury Patient Outcomes With Duration of Cerebrovascular Autoregulation Impairment Events

BACKGROUND Cerebrovascular autoregulation (CA) is an important hemodynamic mechanism that protects the brain against inappropriate fluctuations in cerebral blood flow in the face of changing cerebral perfusion pressure. Temporal CA failure is associated with worse outcomes in various acute neurological diseases. An integrative approach is presently used according to the existing paradigm for the association of series of temporal CA impairments with the outcomes of patients with traumatic brain injury (TBI). OBJECTIVE To explore the influence of the duration of CA impairment events on severe TBI patient outcomes. Patient age was also included in the analysis of the prospectively collected clinical data. METHODS CA monitoring included 33 prospective severe TBI patients. The pressure reactivity index [PRx(t)] was continuously monitored to collect information on the dynamics of CA status and to analyze associations between the duration of the longest CA impairment event and patient outcomes. RESULTS The Glasgow outcome scale and the duration of the longest CA impairment were negatively correlated. The duration of autoregulation impairment significantly correlated with worse outcomes. Multidimensional representation of Glasgow outcome scale plots showed that better outcomes were obtained for younger patients (age < 47 years) and those whose longest CA impairment event was shorter than 40 minutes if PRx(t) was above 0.7 in the CA impairment event. CONCLUSION Unfavorable outcomes for TBI patients are more significantly associated with the duration of the single longest CA impairment episode at a high PRx(t) value, rather than with averaged PRx(t) values or the average time of all CA impairment episodes. ABBREVIATIONS ABP, arterial blood pressureABP(t), continuous reference arterial blood pressureCA, cerebrovascular autoregulationCBF, cerebral blood flowCPP, cerebral perfusion pressureGOS, Glasgow outcome scaleGOSHD, Glasgow outcome scale after hospital dischargeGOS6M, Glasgow outcome scale at 6 months after dischargeICP, intracranial pressureICP(t), continuously monitored intracranial pressureLCAI, longest CA impairmentoptCPP, optimal cerebral perfusion pressurePRx(t), pressure reactivity indexTBI, traumatic brain injury.

Novel Technology of Non-invasive Cerebrovascular Autoregulation Monitoring

A novel technology for non - invasive cerebrovascular auto regulation (CA) status monitoring is presented. This fully non-invasive CA monitor is based on ultrasonic time-of-flight (TOF) measurement of cerebral blood volume pulsations within the brain parenchyma, processing of volumetric waves, and calculation of CA estimation indexes without using any additional arterial blood pressure (ABP) measurements. The CA status is estimated by extracting informative and reference slow waves from non-invasively measured TOF signals and by calculating Pearsons correlation coefficient between these waves as a CA index. The analysis of the signal extracted from the envelope of non-invasively measured pulse waves showed good agreement between this signal and ABP waves (r=0.68). Consequently, it shows that this signal might be used instead of ABP waves as a reference signal for calculation of the CA estimation indexes. Comparative invasive versus non-invasive CA monitoring study of 11 traumatic brain injury patients showed that correlation between invasively measured CA index and fully non-invasively measured CA index (no arterial line) was r=0.75. The proposed innovative CA real-time monitoring method gives us new possibilities to perform estimation of the CA status from intracranial waves only as well as to exclude the ABP lines errors and artifacts from the measurement results.

Non-invasive Cerebrovascular Autoregulation Assessment Using the Volumetric Reactivity Index: Prospective Study

BackgroundThis 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.MethodsCA 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.ResultsA 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.ConclusionsThis 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.

Innovative Computerized Non-invasive Intracranial Pressure Measurement Technology and Its Clinical Validation

An innovative non-invasive absolute intracranial pressure (aICP) measurement method has been validated by multicenter comparative clinical studies. The method is based on two-depth transcranial Doppler technology and employs intracranial and extra cranial segments of the ophthalmic artery as a pressure sensor. The ophthalmic artery is used as a natural pair of scales which compares aICP with controlled pressure aPe which is externally applied to the orbit. In the case of scales balance, aICP=aPe. A two-depth transcranial Doppler device is used as a pressure balance indicator. The proposed method is the only non-invasive aICP measurement method which does not need patient-specific calibration.