Cerebrovascular Autoregulation Status Research Articles

Prospective Pilot Clinical Study of Noninvasive Cerebrovascular Autoregulation Monitoring in Open-Angle Glaucoma Patients and Healthy Subjects.

PurposeTo analyze the cerebrovascular autoregulation (CA) dynamics in patients with normal-tension glaucoma (NTG) and high-tension glaucoma (HTG) as well as healthy subjects using noninvasive ultrasound technologies for the first time.MethodsThe CA status of 10 patients with NTG, 8 patients with HTG, and 10 healthy subjects was assessed, using an innovative noninvasive ultrasonic technique, based on intracranial blood volume slow-wave measurements. Identified in each participant were intraocular pressure, ocular perfusion pressure, and CA-related parameter volumetric reactivity index (VRx), as well as the duration and doses of the longest cerebral autoregulation impairment (LCAI). In addition, we calculated the associations of these parameters with patients’ diagnoses.ResultsThe VRx value, the LCAI dose, and duration in healthy subjects were significantly lower than in patients with NTG (P < 0.05). However, no significant differences were noted in these parameters between healthy subjects and HTG and between NTG and HTG groups.ConclusionsNTG is associated with the disturbed cerebral blood flow and could be diagnosed by performing noninvasive CA assessments.Translational RelevanceThe VRx monitoring method can be applied to a wider range of patient groups, especially patients with normal-tension glaucoma.

Cerebrovascular Autoregulation Monitoring in the Management of Adult Severe Traumatic Brain Injury: A Delphi Consensus of Clinicians

BackgroundSeveral methods have been proposed to measure cerebrovascular autoregulation (CA) in traumatic brain injury (TBI), but the lack of a gold standard and the absence of prospective clinical data on risks, impact on care and outcomes of implementation of CA-guided management lead to uncertainty.AimTo formulate statements using a Delphi consensus approach employing a group of expert clinicians, that reflect current knowledge of CA, aspects that can be implemented in TBI management and CA research priorities.MethodsA group of 25 international academic experts with clinical expertise in the management of adult severe TBI patients participated in this consensus process. Seventy-seven statements and multiple-choice questions were submitted to the group in two online surveys, followed by a face-to-face meeting and a third online survey. Participants received feedback on average scores and the rationale for resubmission or rephrasing of statements. Consensus on a statement was defined as agreement of more than 75% of participants.ResultsConsensus amongst participants was achieved on the importance of CA status in adult severe TBI pathophysiology, the dynamic non-binary nature of CA impairment, its association with outcome and the inadvisability of employing universal and absolute cerebral perfusion pressure targets. Consensus could not be reached on the accuracy, reliability and validation of any current CA assessment method. There was also no consensus on how to implement CA information in clinical management protocols, reflecting insufficient clinical evidence.ConclusionThe Delphi process resulted in 25 consensus statements addressing the pathophysiology of impaired CA, and its impact on cerebral perfusion pressure targets and outcome. A research agenda was proposed emphasizing the need for better validated CA assessment methods as well as the focused investigation of the application of CA-guided management in clinical care using prospective safety, feasibility and efficacy studies.

Impact of duration and magnitude of raised intracranial pressure on outcome after severe traumatic brain injury: A CENTER-TBI high-resolution group study.

Magnitude of intracranial pressure (ICP) elevations and their duration have been associated with worse outcomes in patients with traumatic brain injuries (TBI), however published thresholds for injury vary and uncertainty about these levels has received relatively little attention. In this study, we have analyzed high-resolution ICP monitoring data in 227 adult patients in the CENTER-TBI dataset. Our aim was to identify thresholds of ICP intensity and duration associated with worse outcome, and to evaluate the uncertainty in any such thresholds. We present ICP intensity and duration plots to visualize the relationship between ICP events and outcome. We also introduced a novel bootstrap technique to evaluate uncertainty of the equipoise line. We found that an intensity threshold of 18 ± 4 mmHg (2 standard deviations) was associated with worse outcomes in this cohort. In contrast, the uncertainty in what duration is associated with harm was larger, and safe durations were found to be population dependent. The pressure and time dose (PTD) was also calculated as area under the curve above thresholds of ICP. A relationship between PTD and mortality could be established, as well as for unfavourable outcome. This relationship remained valid for mortality but not unfavourable outcome after adjusting for IMPACT core variables and maximum therapy intensity level. Importantly, during periods of impaired autoregulation (defined as pressure reactivity index (PRx)>0.3) ICP events were associated with worse outcomes for nearly all durations and ICP levels in this cohort and there was a stronger relationship between outcome and PTD. Whilst caution should be exercised in ascribing causation in observational analyses, these results suggest intracranial hypertension is poorly tolerated in the presence of impaired autoregulation. ICP level guidelines may need to be revised in the future taking into account cerebrovascular autoregulation status considered jointly with ICP levels.

Impaired Cerebrovascular Autoregulation in Large Vessel Occlusive Stroke after Successful Mechanical Thrombectomy: A Prospective Cohort Study

Introduction: Successful thrombectomy improves morbidity and mortality after stroke. The present prospective, observational cohort study investigated a potential correlation between the successful restoration of tissue perfusion by mechanical thrombectomy and intact cerebrovascular autoregulation (CA). Objective: Status of CA in patients with large vessel occlusive stroke after thrombectomy. Methods: After thrombectomy CA was measured using transcranial Doppler ultrasound. For this purpose a moving correlation index (Mxa) based on spontaneous arterial blood pressure fluctuations and corresponding cerebral blood flow velocity changes was calculated. CA impairment was defined by Mxa values more than .3. Results: Twenty patients with an acute occlusion of the middle cerebral artery or distal internal carotid artery were included. A successful recanalization of the occluded vessel via interventional thrombectomy was achieved in 10 of these patients (successful recanalization group), while in 10 patients mechanical recanalization failed or could not be applied (no recanalization group). Mean Mxa at stroke side was .58 ± .21 Table 2a in patients with successful intervention. At the unaffected hemisphere Mxa was .50 ± .20 Table 2a in successful recanalization group and .45 ± .24 Table 2b in no recanalization group without statistically significant differences. Based on the previously defined Mxa cut off more than .3, CA impairment was observable in all successful recanalized patients and in 8 of 10 patients with unsuccessful interventional treatment. Conclusions: These results suggest that brain perfusion may be affected due to impaired CA even after successful mechanical thrombectomy. Therefore, a tight blood pressure management is of great importance in post-thrombectomy stroke treatment to avoid cerebral hypo- and hyperperfusion.

Glaucoma and cerebral blood flow autoregulation: Pilot study

Glaucoma is a leading cause of irreversible blindness worldwide. Although high tension glaucoma (HTG) is associated with increased intraocular pressure, the causes of normal tension glaucoma (NTG) are controversial. We hypothesize that NTG can be related with disturbed cerebral blood flow, therefore, our objective was to explore cerebrovascular autoregulation (CA) status in glaucoma patients. Pilot study of non-invasive CA monitoring included 10NTG patients, 8HTG patients and 10 volunteers in control group. All participants were 63–80 y/o. CA status was monitored by using non-invasive ultrasonic CA monitoring technology based on intracranial blood volume (IBV) slow-wave measurement. Real-time recording of volumetric reactivity index (VRx(t)) was used in order to identify dynamics of CA changes. VRx(t) reflects a time dependence of a phase shift between non-invasively measured IBV(t) and arterial blood pressure ABP(t) slow-waves. Mean values of VRx(t) and SD were as follows: control mVRx = −0.179, SD = 0.22; NTG mVRx = 0.056, SD = 0.168 and HTG mVRx = −0.070, SD = 0.249 (Fig. 1). Statistically significant differences were found in comparing mVRx indexes as well as duration of longest CA impairment events in NTG and control group (Mann-Whitney U tests P = 0.025 and P = 0.007, respectively). However, these differences were not significant in HTG and control group. By using this non-invasive technology, it has been shown for the first time that CA status is deteriorated in NTG patients and that mean VRx(t) values are statistically significantly different comparing NTG and control groups. We didn't find statistically significant difference between HTG and control group.

Patient-specific management of severe TBI depending on age and cerebrovascular autoregulation status

Patient-specific management of severe TBI depending on age and cerebrovascular autoregulation status

Patient-specific management of severe TBI depending on age and cerebrovascular autoregulation status

Determination of proper choice of patient-specific management methodology is crucial for patients with traumatic brain injury (TBI). The treatment outcomes of TBI patients depend on cerebral blood flow autoregulation impairments which can also be affected by patients’ age, brain injury grade or pharmacological influences (anaesthetics, sedation, etc.). The objective of the prospective study was to explore the influence of various factors (dynamics of cerebrovascular autoregulation (CA) status, cerebral perfusion pressure (CPP) declination from optimal CPP value (ΔCPPopt), TBI severity, age, glucose level in blood, etc.) on the TBI patients' outcome. Multimodal ABP, ICP, CPP and CA monitoring of 81 TBI patients has been performed in Republic Vilnius University Hospital (Lithuania). ICM+ software (Cambridge, UK) was used for continuous CA status assessment by calculating Pressure Reactivity Index (PRx) and for identification of patient-specific optimal CPP (optCPP). The post-hoc analysis of associations between the patients' outcome and complex influence monitored parameters was performed by creating multifactorial model of predicting TBI patient's outcome and determining the most important factors affecting outcome. The multifactorial logistic regression model showed that the most significant factors affecting TBI patient's outcome are age, Glasgow Coma Scale (GCS), glucose level in blood serum samples (determined within 24 hours after admission), Helsinki CT (HCT) score and duration of longest CA impairment when PRx(t) > 0.5 within 24 hours after admission. The modelled accuracies for mortality and unfavorable outcome prediction were 82% and 86% respectively. The age > 45 years (P = 0.034, χ2 = 17.48) and HCT > 7 (P = 0.14, χ2 = 15.13) were found statistically significantly associated with unfavorable outcome or mortality. OptCPP-targeted management was found statistically significantly associated with better outcome for younger patients (age 0.36 and duration of LCAI > 100 min (P = 0.043, χ2 = 18.00) were found associated with mortality for younger patients group ( 0.26 (P = 0.005, χ2 = 7.80) and duration of LCAI > 61 min (P = 0.019, χ2 = 5.44) were founded associated with mortality for elderly patients group (> 45 years). The main factors affecting TBI treatment outcomes are patient's age, HCT, GCS, blood glucose level and the CA status during first day after patient admission. The optCPP-targeted patient-specific management is useful for stabilizing CA in severe TBI patients as well as for improving outcome for younger patients with age

Time spent with impaired autoregulation is linked with outcome in severe infant/paediatric traumatic brain injury.

It could be shown in traumatic brain injury (TBI) in adults that the functional status of cerebrovascular autoregulation (AR), determined by the pressure reactivity index (PRx), correlates to and even predicts outcome. We investigated PRx, cerebral perfusion pressure (CPP) and intracranial pressure (ICP) and their correlation to outcome in severe infant and paediatric TBI. Seventeen patients (range, 1day to 14years) with severe TBI (median GCS at presentation, 4) underwent long-term computerised ICP and mean arterial pressure (MAP) monitoring using dedicated software to determine CPP and PRx and optimal CPP (CPP level where PRx shows best autoregulation) continuously. Outcome was determined at discharge and at follow-up using the Glasgow Outcome Scale. Favourable outcome was reached in eight patients, unfavourable outcome in seven patients. Two patients died. Nine patients underwent decompressive craniectomy to control ICP during Intensive Care Unit treatment. When dichotomised to outcome, no significant difference was found for overall ICP, CPP and PRx. The time with severely impaired AR (PRx>0.2) was significantly longer for patients with unfavourable outcome (64h vs 6h, p=0.001). Continuously impaired AR of ≥24h and age<1year was associated to unfavourable outcome. Children with favourable outcome spent the entire monitoring time at or above the optimal CPP. Integrity of AR has a similar role for outcome after TBI in the paediatric population as in adults. The amount of time spent with deranged AR seems to be associated with outcome; a factor especially critical for infant patients. The results of this preliminary study need to be validated in the future.

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

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). 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. 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. 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. 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. 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.

State of Cerebrovascular Autoregulation Correlates with Outcome in Severe Infant/Pediatric Traumatic Brain Injury.

It could be shown in adults with severe traumatic brain injury (TBI) that the functional status of cerebrovascular autoregulation (AR), determined by the pressure reactivity index (PRx), correlates with and even predicts outcome. We investigated PRx and its correlation with outcome in infant and pediatric TBI. Methods Ten patients (median age 2.8 years, range 1 day to 14 years) with severe TBI (Glasgow Coma Scale score <9 at presentation) underwent long-term computerized intracranial pressure (ICP) and mean arterial pressure (MAP) monitoring using dedicated software for continuous determination of cerebral perfusion pressure (CPP) and PRx. Outcome was determined at discharge and at follow-up at 6 months using the Glasgow Outcome Scale (GOS) score. Median monitoring time was 182 h (range 22-355 h). Seven patients underwent decompressive craniectomy to control ICP during treatment in the intensive care unit. Favorable outcome (GOS 4 and 5) was reached in 4 patients, an unfavorable outcome (GOS 1-3) in 6 patients. When dichotomized to outcome, no correlation was found with ICP and CPP, but median PRx correlated well with outcome (r = -0.79, p = 0.006) and tended to be lower for GOS 4 and 5 (-0.04) than for GOS 1-3 (0.32; p = 0.067). The integrity of AR seems to play the same fundamental role after TBI in the pediatric population as in adults and should be determined routinely. It carries an important prognostic value. PRx seems to be an ideal candidate parameter to guide treatment in the sense of optimizing CPP, aiming at improvement of cerebrovascular autoregulation (CPPopt concept).

Association between the outcome of traumatic brain injury patients and cerebrovascular autoregulation, cerebral perfusion pressure, age, and injury grades

Background and objectiveThe aim of this study was to explore the association of cerebrovascular autoregulation (CA) and optimal cerebral perfusion pressure (CPP) managing conditions with the outcome of traumatic brain injury (TBI) patients including additional information about the patients’ age and grade of diffuse axonal injury (DAI). Materials and methodsThe CA monitoring of 28 TBI patients was performed by using ICM+ software (Cambridge, UK). The CA status estimating pressure reactivity indexes (PRx) and CPP data were processed in order to obtain information on the patient-specific treatment conditions by calculating the optimal CPP. ResultsThere was a negative correlation between the Glasgow outcome scale (GOS) score and PRx (r=−0.448 at hospital discharge and r=−0.402 after 6 months). The estimated threshold value PRx of >0.24 was associated with mortality. The correlation coefficients between the GOS score and the difference CPP-optimal CPP were 0.549 at hospital discharge and 0.484 after 6 months. The threshold value of CPP declination from ΔCPPopt per −6mmHg was associated with mortality. Poorer outcome was predicted for elderly TBI patients (aged >47 years) and patients having a DAI grade of 3. ConclusionsThe association of the GOS score with CPP, CA impairment conditions, age and diffuse axonal injury (DAI) grade showed that the outcomes of TBI patients were associated with patient-specific CPP management and better outcomes were obtained for younger patients, for patients having lower DAI grade and for patients whose CPP was kept within the range from the optimal CPP to the optimal CPP+10mmHg.

Novel Method and Device for Fully Non-Invasive Cerebrovascular Autoregulation Monitoring

The novel method and the device for non - invasive cerebrovascular autoregulation (CA) status monitoring without using the arterial blood pressure (ABP) measurement channel are presented. This fully non-invasive CA monitor is based on the ultrasonic time-of-flight measurement of cerebral blood volume pulsations within the brain parenchyma, extraction of informative and reference slow and respiratory volumetric waves and calculation of CA estimating indexes without using any additional ABP measurements.For demonstrating the applicability of the proposed method, the CA status was monitored on 11 traumatic brain injury patients simultaneously by using the novel fully non-invasive monitor and compared to the CA status representing indexes calculated from the invasively measured intracranial pressure (ICP) and ABP slow waves. The total monitoring time was about 22 hrs. The correlation factor between the invasively and non-invasively obtained CA data showed significant agreement (r=0.751) between the two methods.The proposed innovative CA real-time monitoring method gives us new possibilities to perform estimation of the CA status from the intracranial waves only as well as to exclude the ABP line’s errors and artifacts from the measurement results.DOI: http://dx.doi.org/10.5755/j01.eee.20.8.5464

Inverse neurovascular coupling to cortical spreading depolarizations in severe brain trauma.

Cortical spreading depolarization causes a breakdown of electrochemical gradients following acute brain injury, and also elicits dynamic changes in regional cerebral blood flow that range from physiological neurovascular coupling (hyperaemia) to pathological inverse coupling (hypoperfusion). In this study, we determined whether pathological inverse neurovascular coupling occurred as a mechanism of secondary brain injury in 24 patients who underwent craniotomy for severe traumatic brain injury. After surgery, spreading depolarizations were monitored with subdural electrode strips and regional cerebral blood flow was measured with a parenchymal thermal diffusion probe. The status of cerebrovascular autoregulation was monitored as a correlation between blood pressure and regional cerebral blood flow. A total of 876 spreading depolarizations were recorded in 17 of 24 patients, but blood flow measurements were obtained for only 196 events because of technical limitations. Transient haemodynamic responses were observed in time-locked association with 82 of 196 (42%) spreading depolarizations in five patients. Spreading depolarizations induced only hyperaemic responses (794% increase) in one patient with intact cerebrovascular autoregulation; and only inverse responses (-24% decrease) in another patient with impaired autoregulation. In contrast, three patients exhibited dynamic changes in neurovascular coupling to depolarizations throughout the course of recordings. Severity of the pathological inverse response progressively increased (-14%, -29%, -79% decrease, P < 0.05) during progressive worsening of cerebrovascular autoregulation in one patient (Pearson coefficient 0.04, 0.14, 0.28, P < 0.05). A second patient showed transformation from physiological hyperaemic coupling (44% increase) to pathological inverse coupling (-30% decrease) (P < 0.05) coinciding with loss of autoregulation (Pearson coefficient 0.19 → 0.32, P < 0.05). The third patient exhibited a similar transformation in brain tissue oxygenation, a surrogate of blood flow, from physiologic hyperoxic responses (20% increase) to pathological hypoxic responses (-14% decrease, P < 0.05). Pathological inverse coupling was only observed with electrodes placed in or adjacent to evolving lesions. Overall, 31% of the pathological inverse responses occurred during ischaemia (<18 ml/100 g/min) thus exacerbating perfusion deficits. Average perfusion was significantly higher in patients with good 6-month outcomes (46.8 ± 6.5 ml/100 g/min) than those with poor outcomes (32.2 ± 3.7 ml/100 g/min, P < 0.05). These results establish inverse neurovascular coupling to spreading depolarization as a novel mechanism of secondary brain injury and suggest that cortical spreading depolarization, the neurovascular response, cerebrovascular autoregulation, and ischaemia are critical processes to monitor and target therapeutically in the management of acute brain injury.

Abstracts fromThe 32nd AnnualNational Neurotrauma SymposiumJune 29–July 2, 2014San Francisco, California

Abstracts fromThe 32^nd AnnualNational Neurotrauma SymposiumJune 29–July 2, 2014San Francisco, California

Clinical Significance of Impaired Cerebrovascular Autoregulation After Severe Aneurysmal Subarachnoid Hemorrhage

The purpose of this study was to investigate the relationship between cerebrovascular autoregulation and outcome after aneurysmal subarachnoid hemorrhage. In a prospective observational study, 80 patients after severe subarachnoid hemorrhage were continuously monitored for cerebral perfusion pressure and partial pressure of brain tissue oxygen for an average of 7.9 days (range, 1.9-14.9 days). Autoregulation was assessed using the index of brain tissue oxygen pressure reactivity (ORx), a moving correlation coefficient between cerebral perfusion pressure and partial pressure of brain tissue oxygen. High ORx indicates impaired autoregulation; low ORx signifies intact autoregulation. Outcome was determined at 6 months and dichotomized into favorable (Glasgow Outcome Scale 4-5) and unfavorable outcome (Glasgow Outcome Scale 1-3). Twenty-four patients had a favorable and 56 an unfavorable outcome. In a univariate analysis, there were significant differences in autoregulation (ORx 0.19±0.10 versus 0.37±0.11, P<0.001, for favorable versus unfavorable outcome, respectively), age (44.1±11.0 years versus 54.2±12.1 years, P=0.001), occurrence of delayed cerebral infarction (8% versus 46%, P<0.001), use of coiling (25% versus 54%, P=0.02), partial pressure of brain tissue oxygen (24.9±6.6 mm Hg versus 21.8±6.3 mm Hg, P=0.048), and Fisher grade (P=0.03). In a multivariate analysis, ORx (P<0.001) and age (P=0.003) retained an independent predictive value for outcome. ORx correlated with Glasgow Outcome Scale (r=-0.70, P<0.001). The status of cerebrovascular autoregulation might be an important pathophysiological factor in the disease process after subarachnoid hemorrhage, because impaired autoregulation was independently associated with an unfavorable outcome.

Noninvasive Monitoring of Cerebrovascular Autoregulation Response to Resistance Exercises

BACKGROUND AND OBJECTIVE. A novel noninvasive monitor is presented by demonstrating its capabilities to perform the real-time estimation of dynamics in cerebrovascular autoregulation in athletes during their training. The aim was to explore the characteristics of human cerebrovascular autoregulation by performing the monitoring of cerebrovascular autoregulation responses to resistance exercises in healthy volunteer athletes. MATERIAL AND METHODS. Cerebrovascular autoregulation status was monitored in 20 amateur and 20 elite male athletes (weightlifters and bodybuilders) in the supine position at rest during and after the resistance exercises by using a novel noninvasive monitor "Vittamed." Blood pressure and heart rate were also measured noninvasively. During the exercises, the athletes lifted 50 kg and 80% of 1RM (repetition maximum) weights in a dynamic and static manner in separate tests. RESULTS. The cerebrovascular autoregulation reactivity index showed a temporal improvement in the cerebrovascular autoregulation status for almost all sportsmen after the exercises. No disturbances of cerebrovascular autoregulation response occurred in the weightlifters and amateur athletes after the static and dynamic exercises. However, an unstable status of cerebrovascular autoregulation was observed for the elite bodybuilders during the interval of 400 to 600s after the exercises. CONCLUSIONS. The data of this study demonstrated significant differences in cerebrovascular autoregulation response to the resistance exercises between the elite bodybuilders and other subjects (amateurs and weightlifters) - a temporarily unstable status of cerebrovascular autoregulation was observed in the group of elite bodybuilders. This study also demonstrated the applicability of the noninvasive device for exploring the physiology of cerebrovascular autoregulation mechanism in elite athletes and healthy volunteers.

Are Optimal Cerebral Perfusion Pressure and Cerebrovascular Autoregulation Related to Long-term Outcome in Patients With Aneurysmal Subarachnoid Hemorrhage?

Continuous assessment of the cerebrovascular autoregulation (CVA) through use of the pressure reactivity index (PRx), a moving linear correlation coefficient between mean arterial blood pressure and intracranial pressure, has been effective in optimizing cerebral perfusion pressure (CPPopt) in traumatic brain injured (TBI) patients. This study investigates the feasibility of measuring CPPopt in patients with aneurysmal subarachnoid hemorrhage (aSAH) by continuously assessing the CVA. Twenty-nine aSAH patients were enrolled, and data from CVA status, CPPopt, and periods when CPP was below, within, or above CPPopt were computed daily. Outcome was assessed at 6 months with the Glasgow Outcome Scale. Mann-Whitney U test was used to analyze differences in the duration of impaired CVA and duration of CPP below CPPopt in patients with good and poor outcomes. Multivariable logistic regression analysis was used to identify independent predictors of outcome. CVA monitoring data were available for all 29 patients with a total monitoring time of 2757 h. The duration of impaired CVA was 36.5% (interquartile range: 24.6 to 49.8) of the total monitoring time in 15 patients with good outcome and 71.6% of the total monitoring time (51.2 to 80.0) in 14 patients with poor outcome (Mann-Whitney U test 3.295, P=0.0010). PRx-based CPPopt could be identified in 26 patients (89.6%) with a total monitoring time of 2691 h. The duration of CPP below the CPPopt range was 28.0% (interquartile range: 18.0 to 47.0) of the total monitoring time in patients with good outcome and 76.0% (48.5 to 82.5) in patients with poor outcome (Mann-Whitney U test 2.779, P=0.0054). Glasgow Coma Scale score and duration of impaired CVA were independently associated with 6-month outcome (Glasgow Coma Scale score odds ratio: 1.95, 95% confidence interval: 1.01-3.75; duration of impaired CVA odds ratio: 0.88, 95% confidence interval: 0.78-0.99). The assessment of CVA and CPPopt is feasible in aSAH patients and may provide important information regarding long-term outcome. A PRx above the 0.2 threshold and a CPP below the CPPopt range are associated with worse outcome.

Serial Measurement of Static and Dynamic Cerebrovascular Autoregulation After Brain Injury

In patients with neuronal injury, the knowledge of the status of cerebrovascular autoregulation can help to optimize the management of the cerebral perfusion pressure. This study characterizes dynamic and static cerebrovascular autoregulation during the first 7 days after severe traumatic brain injury or intracranial hemorrhage. After approval from the IRB, 16 patients were studied. Cerebral blood flow velocity (CBFV) was measured daily for the assessment of dynamic (10 patients) and static (16 patients) cerebrovascular autoregulation in both the middle cerebral arteries using the transcranial Doppler sonography. Dynamic cerebrovascular autoregulation (dAR) was measured using the cuff-deflation method and was expressed by the index of the dAR. The index of the static cerebrovascular autoregulation (sAR) was calculated from changes in the CBFV in relation to drug-induced alterations of the arterial blood pressure. For statistical analyses, t test and mixed effect model were used. Both dAR and sAR after brain injury were impaired in most of the patients. The chronologic sequence of the dAR at the ipsilateral injured hemisphere showed a significant decrease until day 4 followed by an incomplete recovery (P < 0.002). Changes in sAR were similar, however, they did not gain statistical significance. CBFV was lower at day 1-2 after injury in comparison with day 4 to 7 (P < 0.02). Daily measured dAR and sAR were impaired after brain injury with a nadir on day 4 and consecutive incomplete recovery over time.

Intracranial pressure pulse amplitude during changes in head elevation: a new parameter for determining optimum cerebral perfusion pressure?

During short-term postural changes, the factors determining the amplitude of intracranial pulse pressure (ICPPA) remain constant, except for cerebrovascular resistance (CVR). Therefore, it may be possible to draw conclusions from the ICPPA onto the cerebrovascular resistance (CVR) and thus the relative change in cerebral perfusion pressure (CPP). Age, sex, disease, Glasgow Coma Scale score, placement of ventricular drain, blood gas analysis, and parameters of airway management were prospectively recorded in 40 patients. The changes in intracranial pressure (ICP), CPP, mean arterial pressure (MAP), and ICPPA at head elevations of 0 degrees, 30 degrees, and 60 degrees were measured and analyzed online. Status of cerebrovascular autoregulation was checked using the pressure-reactivity index (PRx). Altogether 36 subjects fulfilled the study conditions. Three patients had positive PRx indicating disturbed autoregulation and were excluded. Thus, 33 were left for analysis (18 females and 15 males). All of them were sedated and mechanically ventilated with Glasgow Coma scores ranging from 3-8. During change in head elevation from 0 degrees to 60 degrees, we found a significant (p < 0.05) improvement of the ICP, an increase of the ICCPA, a reduction of the MAP, and a decrease in the CPP. Increasing ICPPA was linked to decreasing CPP (0 degrees to 60 degrees, r = -0.42, p < 0.05). Head elevation is an important part of the ICP and CPP therapy in neurointensive care. When searching for the patient-specific optimum upper body position, ICPPA may provide additional information. Providing that the cerebral autoregulation is intact, the lowest ICPPA of a patient corresponds to the individual upper body position with the highest CPP.

Continuous assessment of cerebrovascular autoregulation after traumatic brain injury using brain tissue oxygen pressure reactivity*

To evaluate whether two newly developed indexes of brain tissue oxygen pressure reactivity (ORx and bPtio2) provide information on the status of cerebrovascular autoregulation after traumatic brain injury. This was accomplished by analyzing the relationship between these indexes and an index of cerebrovascular pressure reactivity (PRx). PRx is an established parameter for estimation of cerebrovascular autoregulation. Retrospective analysis of prospectively collected data. Neurosurgical intensive care unit of a university hospital. Twenty-seven patients suffering from severe traumatic brain injury. Continuous monitoring of mean arterial blood pressure, intracranial pressure, cerebral perfusion pressure, and partial pressure of brain tissue oxygen (Ptio2) was performed for an average of 6.5 days. ORx was calculated as a moving correlation coefficient between values of cerebral perfusion pressure and Ptio2. The bPtio2 was calculated as a moving value of the slope of the linear regression function between cerebral perfusion pressure and Ptio2. PRx was calculated as a moving correlation coefficient between values for intracranial pressure and mean arterial blood pressure. Outcome was assessed at 6 months after traumatic brain injury (Glasgow Outcome Scale). Both ORx and bPtio2 correlated significantly with PRx (r=.55 for ORx, r=.52 for bPtio2, p<.01). PRx and ORx showed a significantly negative correlation to the monitored Ptio2 values (r=-.42 for PRx, r=-.41 for ORx, p<.05) and outcome (r=-.52 for PRx, r=-.62 for ORx, p<.01), whereas bPtio2 did not. ORx and, to a lesser extent, bPtio2 correlated with the autoregulatory marker PRx and provide additional information about the status of cerebrovascular autoregulation after traumatic brain injury. The data also suggested that patients with impaired autoregulation are at increased risk for secondary cerebral hypoxia.