Cerebral Perfusion Pressure Insults and Associations with Outcome in Adult Traumatic Brain Injury

Lung-Protective Mechanical Ventilation in Patients with Severe Acute Brain Injury: A Multicenter Randomized Clinical Trial (PROLABI)

Rationale: Lung-protective strategies using low Vt and moderate positive end-expiratory pressure (PEEP) are considered best practice in critical care, but interventional trials have never been conducted in patients with acute brain injuries because of concerns about carbon dioxide control and the effect of PEEP on cerebral hemodynamics. Objectives: To test the hypothesis that ventilation with lower VT and higher PEEP compared to conventional ventilation would improve clinical outcomes in patients with acute brain injury. Methods: In this multicenter, open-label, controlled clinical trial, 190 adult patients with acute brain injury were assigned to receive either a lung-protective or a conventional ventilatory strategy. The primary outcome was a composite endpoint of death, ventilator dependency, and acute respiratory distress syndrome (ARDS) at Day 28. Neurological outcome was assessed at ICU discharge by the Oxford Handicap Scale and at 6 months by the Glasgow Outcome Scale. Measurements and Main Results: The two study arms had similar characteristics at baseline. In the lung-protective and conventional strategy groups, using an intention-to-treat approach, the composite outcome at 28 days was 61.5% and 45.3% (relative risk [RR], 1.35; 95% confidence interval [CI], 1.03-1.79; P = 0.025). Mortality was 28.9% and 15.1% (RR, 1.91; 95% CI, 1.06-3.42; P = 0.02), ventilator dependency was 42.3% and 27.9% (RR, 1.52; 95% CI, 1.01-2.28; P = 0.039), and incidence of ARDS was 30.8% and 22.1% (RR, 1.39; 95% CI, 0.85-2.27; P = 0.179), respectively. The trial was stopped after enrolling 190 subjects because of termination of funding. Conclusions: In patients with acute brain injury without ARDS, a lung-protective ventilatory strategy, as compared with a conventional strategy, did not reduce mortality, percentage of patients weaned from mechanical ventilation, or incidence of ARDS and was not beneficial in terms of neurological outcomes. Because of the early termination, these preliminary results require confirmation in larger trials. Clinical trial registered with www.clinicaltrials.gov (NCT01690819).

Heart Rate Variability and Cerebral Autoregulation in Patients with Traumatic Brain Injury with Paroxysmal Sympathetic Hyperactivity Syndrome

BACKGROUND

Severe traumatic brain injury (TBI) can lead to transient changes in autonomic nervous system (ANS) functioning and development of paroxysmal sympathetic hyperactivity (PSH) syndrome. Clinical manifestation of ANS disorders may be obscured by therapeutic interventions in TBI. This study aims to analyze ANS metrics and cerebral autoregulation in patients with PSH syndrome to determine their significance in early prognostication.

METHODS

This single-center retrospective study investigated the relationship between changes in ANS metrics, cerebral autoregulation, and PSH syndrome. Arterial blood pressure and intracranial pressure signals were monitored for 5 days post TBI. ANS metrics included time and frequency domain heart rate variability (HRV) metrics. Cerebral autoregulation was assessed using the pressure reactivity index.

RESULTS

Sixty-six patients with severe TBI (median age 33 [interquartile range 26-50] years) were analyzed, and PSH was confirmed in nine cases. Impairment of cerebral autoregulation was observed in 67% of patients with PSH and 72% without the syndrome. Patients with PSH had higher HRV in the low-frequency range (LF; 253 ± 178 vs. 176 ± 227 ms2; p = 0.035) and lower heart rates (HRs; 70 ± 7 vs. 78 ± 19 bpm; p = 0.027) compared to those without PSH. A receiver operating characteristic curve analysis indicated that HR (area under the curve (AUC) = 0.73, p = 0.006) and HRV in the LF (AUC = 0.70, p = 0.009) are moderate predictors of PSH. In the multiple logistic regression model for PSH, diffuse axonal trauma (odds ratio (OR) = 10.82, 95% confidence interval (CI) = 1.70-68.98, p = 0.012) and HR (OR = 0.91, 95%  CI 0.84-0.98, p = 0.021) were significant factors.

CONCLUSIONS

Elevated HRV in the LF and decreased HR may serve as early predictors of PSH syndrome development, particularly in patients with diffuse axonal trauma. Further research is needed to investigate the utility of the cerebral autoregulation-ANS relationship in PSH prognostication.

How to Define and Meet Blood Pressure Targets After Traumatic Brain Injury: A Narrative Review

BACKGROUND

Traumatic brain injury (TBI) poses a significant challenge to healthcare providers, necessitating meticulous management of hemodynamic parameters to optimize patient outcomes. This article delves into the critical task of defining and meeting continuous arterial blood pressure (ABP) and cerebral perfusion pressure (CPP) targets in the context of severe TBI in neurocritical care settings.

METHODS

We narratively reviewed existing literature, clinical guidelines, and emerging technologies to propose a comprehensive approach that integrates real-time monitoring, individualized cerebral perfusion target setting, and dynamic interventions.

RESULTS

Our findings emphasize the need for personalized hemodynamic management, considering the heterogeneity of patients with TBI and the evolving nature of their condition. We describe the latest advancements in monitoring technologies, such as autoregulation-guided ABP/CPP treatment, which enable a more nuanced understanding of cerebral perfusion dynamics. By incorporating these tools into a proactive monitoring strategy, clinicians can tailor interventions to optimize ABP/CPP and mitigate secondary brain injury.

DISCUSSION

Challenges in this field include the lack of standardized protocols for interpreting multimodal neuromonitoring data, potential variability in clinical decision-making, understanding the role of cardiac output, and the need for specialized expertise and customized software to have individualized ABP/CPP targets regularly available. The patient outcome benefit of monitoring-guided ABP/CPP target definitions still needs to be proven in patients with TBI.

CONCLUSIONS

We recommend that the TBI community take proactive steps to translate the potential benefits of personalized ABP/CPP targets, which have been implemented in certain centers, into a standardized and clinically validated reality through randomized controlled trials.

Cerebral physiologic insult burden in acute traumatic neural injury: a Canadian High Resolution-TBI (CAHR-TBI) descriptive analysis

BACKGROUND

Over the recent decades, continuous multi-modal monitoring of cerebral physiology has gained increasing interest for its potential to help minimize secondary brain injury following moderate-to-severe acute traumatic neural injury (also termed traumatic brain injury; TBI). Despite this heightened interest, there has yet to be a comprehensive evaluation of the effects of derangements in multimodal cerebral physiology on global cerebral physiologic insult burden. In this study, we offer a multi-center descriptive analysis of the associations between deranged cerebral physiology and cerebral physiologic insult burden.

METHODS

Using data from the Canadian High-Resolution TBI (CAHR-TBI) Research Collaborative, a total of 369 complete patient datasets were acquired for the purposes of this study. For various cerebral physiologic metrics, patients were trichotomized into low, intermediate, and high cohorts based on mean values. Jonckheere-Terpstra testing was then used to assess for directional relationships between these cerebral physiologic metrics and various measures of cerebral physiologic insult burden. Contour plots were then created to illustrate the impact of preserved vs impaired cerebrovascular reactivity on these relationships.

RESULTS

It was found that elevated intracranial pressure (ICP) was associated with more time spent with cerebral perfusion pressure (CPP) < 60 mmHg and more time with impaired cerebrovascular reactivity. Low CPP was associated with more time spent with ICP > 20 or 22 mmHg and more time spent with impaired cerebrovascular reactivity. Elevated cerebrovascular reactivity indices were associated with more time spent with CPP < 60 mmHg as well as ICP > 20 or 22 mmHg. Low brain tissue oxygenation (PbtO2) only demonstrated a significant association with more time spent with CPP < 60 mmHg. Low regional oxygen saturation (rSO2) failed to produce a statistically significant association with any particular measure of cerebral physiologic insult burden.

CONCLUSIONS

Mean ICP, CPP and, cerebrovascular reactivity values demonstrate statistically significant associations with global cerebral physiologic insult burden; however, it is uncertain whether measures of oxygen delivery provide any significant insight into such insult burden.

Visualization of Cerebral Pressure Autoregulatory Insults in Traumatic Brain Injury

OBJECTIVES

The first aim was to investigate the combined effect of insult intensity and duration of the pressure reactivity index (PRx) and deviation from the autoregulatory cerebral perfusion pressure target (∆CPPopt = actual CPP - optimal CPP [CPPopt]) on outcome in traumatic brain injury. The second aim was to determine if PRx influenced the association between intracranial pressure (ICP), CPP, and ∆CPPopt with outcome.

DESIGN

Observational cohort study.

SETTING

Neurocritical care unit, Cambridge, United Kingdom.

PATIENTS

Five hundred fifty-three traumatic brain injury patients with ICP and arterial blood pressure monitoring and 6-month outcome data (Glasgow Outcome Scale [GOS]).

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

The insult intensity (mm Hg or PRx coefficient) and duration (minutes) of ICP, PRx, CPP, and ∆CPPopt were correlated with GOS and visualized in heatmaps. In these plots, there was a transition from favorable to unfavorable outcome when PRx remained positive for 30 minutes and this was also the case for shorter durations when the intensity was higher. In a similar plot of ∆CPPopt, there was a gradual transition from favorable to unfavorable outcome when ∆CPPopt went below -5 mm Hg for 30-minute episodes of time and for shorter durations for more negative ∆CPPopt. Furthermore, the percentage of monitoring time with certain combinations of PRx with ICP, CPP, and ∆CPPopt were correlated with GOS and visualized in heatmaps. In the combined PRx/ICP heatmap, ICP above 20 mm Hg together with PRx above 0 correlated with unfavorable outcome. In a PRx/CPP heatmap, CPP below 70 mm Hg together with PRx above 0.2-0.4 correlated with unfavorable outcome. In the PRx-/∆CPPopt heatmap, ∆CPPopt below 0 together with PRx above 0.2-0.4 correlated with unfavorable outcome.

CONCLUSIONS

Higher intensities for longer durations of positive PRx and negative ∆CPPopt correlated with worse outcome. Elevated ICP, low CPP, and negative ∆CPPopt were particularly associated with worse outcomes when the cerebral pressure autoregulation was concurrently impaired.

Autoregulatory Cerebral Perfusion Pressure Insults in Traumatic Brain Injury and Aneurysmal Subarachnoid Hemorrhage: The Role of Insult Intensity and Duration on Clinical Outcome

BACKGROUND

This single-center, retrospective study investigated the outcome effect of the combined intensity and duration of differences between actual cerebral perfusion pressure (CPP) and optimal cerebral perfusion pressure (CPPopt), and also for absolute CPP, in patients with traumatic brain injury (TBI) and aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

A total of 378 TBI and 432 aSAH patients treated in a neurointensive care unit between 2008 and 2018 with at least 24 hours of CPPopt data during the first 10 days following injury, and with 6-month (TBI) or 12-month (aSAH) extended Glasgow Outcome Scale (GOS-E) scores, were included in the study. ∆CPPopt-insults (∆CPPopt=actual CPP-CPPopt) and CPP-insults were visualized as 2-dimensional plots to highlight the combined effect of insult intensity (mm Hg) and duration (min) on patient outcome.

RESULTS

In TBI patients, a zone of ∆CPPopt ± 10 mm Hg was associated with more favorable outcome, with transitions towards unfavorable outcome above and below this zone. CPP in the range of 60 to 80 mm Hg was associated with higher GOS-E, whereas CPP outside this range was associated with lower GOS-E. In aSAH patients, there was no clear transition from higher to lower GOS-E for ∆CPPopt-insults; however, there was a transition from favorable to unfavorable outcome when CPP was <80 mm Hg.

CONCLUSIONS

TBI patients with CPP close to CPPopt exhibited better clinical outcomes, and absolute CPP within the 60 to 80 mm Hg range was also associated with favorable outcome. In aSAH patients, there was no clear transition for ∆CPPopt-insults in relation to outcome, whereas generally high absolute CPP values were associated overall with favorable recovery.

Artificial Intelligence and Machine Learning Applications in Critically Ill Brain Injured Patients

The utilization of Artificial Intelligence (AI) and Machine Learning (ML) is paving the way for significant strides in patient diagnosis, treatment, and prognostication in neurocritical care. These technologies offer the potential to unravel complex patterns within vast datasets ranging from vast clinical data and EEG (electroencephalogram) readings to advanced cerebral imaging facilitating a more nuanced understanding of patient conditions. Despite their promise, the implementation of AI and ML faces substantial hurdles. Historical biases within training data, the challenge of interpreting multifaceted data streams, and the "black box" nature of ML algorithms present barriers to widespread clinical adoption. Moreover, ethical considerations around data privacy and the need for transparent, explainable models remain paramount to ensure trust and efficacy in clinical decision-making.This article reflects on the emergence of AI and ML as integral tools in neurocritical care, discussing their roles from the perspective of both their scientific promise and the associated challenges. We underscore the importance of extensive validation in diverse clinical settings to ensure the generalizability of ML models, particularly considering their potential to inform critical medical decisions such as withdrawal of life-sustaining therapies. Advancement in computational capabilities is essential for implementing ML in clinical settings, allowing for real-time analysis and decision support at the point of care. As AI and ML are poised to become commonplace in clinical practice, it is incumbent upon health care professionals to understand and oversee these technologies, ensuring they adhere to the highest safety standards and contribute to the realization of personalized medicine. This engagement will be pivotal in integrating AI and ML into patient care, optimizing outcomes in neurocritical care through informed and data-driven decision-making.

Cerebral Autoregulation-guided Management of Adult and Pediatric Traumatic Brain Injury

Cerebral autoregulation (CA) plays a vital role in maintaining cerebral blood flow in response to changes in systemic blood pressure. Impairment of CA following traumatic brain injury (TBI) may exacerbate the injury, potentially impacting patient outcomes. This focused review addresses 4 key questions regarding the measurement, natural history of CA after TBI, and potential clinical implications of CA status and CA-guided management in adults and children with TBI. We examine the feasibility and safety of CA assessment, its association with clinical outcomes, and the potential for reversing deranged CA following TBI. Finally, we discuss how the knowledge of CA status may affect TBI management and outcomes.

Brain tissue oxygen monitoring in traumatic brain injury-part II: isolated and combined insults in relation to outcome

BACKGROUND

The primary aim was to explore the concept of isolated and combined threshold-insults for brain tissue oxygenation (pbtO2) in relation to outcome in traumatic brain injury (TBI).

METHODS

A total of 239 TBI patients with data on clinical outcome (GOS) and intracranial pressure (ICP) and pbtO2 monitoring for at least 12 h, who had been treated at the neurocritical care unit, Addenbrooke's Hospital, Cambridge, UK, between 2002 and 2022 were included. Outcome was dichotomised into favourable/unfavourable (GOS 4-5/1-3) and survival/mortality (GOS 2-5/1). PbtO2 was studied over the entire monitoring period. Thresholds were analysed in relation to outcome based on median and mean values, percentage of time and dose per hour below critical values and visualised as the combined insult intensity and duration.

RESULTS

Median pbtO2 was slightly, but not significantly, associated with outcome. A pbtO2 threshold at 25 and 20 mmHg, respectively, yielded the highest x2 when dichotomised for favourable/unfavourable outcome and mortality/survival in chi-square analyses. A higher dose and higher percentage of time spent with pbtO2 below 25 mmHg as well as lower thresholds were associated with unfavourable outcome, but not mortality. In a combined insult intensity and duration analysis, there was a transition from favourable towards unfavourable outcome when pbtO2 went below 25-30 mmHg for 30 min and similar transitions occurred for shorter durations when the intensity was higher. Although these insults were rare, pbtO2 under 15 mmHg was more strongly associated with unfavourable outcome if, concurrently, ICP was above 20 mmHg, cerebral perfusion pressure below 60 mmHg, or pressure reactivity index above 0.30 than if these variables were not deranged. In a multiple logistic regression, a higher percentage of monitoring time with pbtO2 < 15 mmHg was associated with a higher rate of unfavourable outcome.

CONCLUSIONS

Low pbtO2, under 25 mmHg and particularly below 15 mmHg, for longer durations and in combination with disturbances in global cerebral physiological variables were associated with poor outcome and may indicate detrimental ischaemic hypoxia. Prospective trials are needed to determine if pbtO2-directed therapy is beneficial, at what individualised pbtO2 threshold therapies are warranted, and how this may depend on the presence/absence of concurrent cerebral physiological disturbances.

Intracranial pressure for clinicians: it is not just a number

BACKGROUND

Invasive intracranial pressure (ICP) monitoring is a standard practice in severe brain injury cases, where it allows to derive cerebral perfusion pressure (CPP); ICP-tracing can also provide additional information about intracranial dynamics, forecast episodes of intracranial hypertension and set targets for a tailored therapy to prevent secondary brain injury. Nevertheless, controversies about the advantages of an ICP clinical management are still debated.

FINDINGS

This article reviews recent research on ICP to improve the understanding of the topic and uncover the hidden information in this signal that may be useful in clinical practice. Parameters derived from time-domain as well as frequency domain analysis include compensatory reserve, autoregulation estimation, pulse waveform analysis, and behavior of ICP in time. The possibility to predict the outcome and apply a tailored therapy using a personalised perfusion pressure target is also described.

CONCLUSIONS

ICP is a crucial signal to monitor in severely brain injured patients; a bedside computer can empower standard monitoring giving new metrics that may aid in clinical management, establish a personalized therapy, and help to predict the outcome. Continuous collaboration between engineers and clinicians and application of new technologies to healthcare, is vital to improve the accuracy of current metrics and progress towards better care with individualized dynamic targets.

ICP, PRx, CPP, and ∆CPPopt in pediatric traumatic brain injury: the combined effect of insult intensity and duration on outcome

PURPOSE

The aim was to investigate the combined effect of insult intensity and duration, regarding intracranial pressure (ICP), pressure reactivity index (PRx), cerebral perfusion pressure (CPP), and optimal CPP (CPPopt), on clinical outcome in pediatric traumatic brain injury (TBI).

METHOD

This observational study included 61 pediatric patients with severe TBI, treated at the Uppsala University Hospital, between 2007 and 2018, with at least 12 h of ICP data the first 10 days post-injury. ICP, PRx, CPP, and ∆CPPopt (actual CPP-CPPopt) insults were visualized as 2-dimensional plots to illustrate the combined effect of insult intensity and duration on neurological recovery.

RESULTS

This cohort was mostly adolescent pediatric TBI patients with a median age at 15 (interquartile range 12-16) years. For ICP, brief episodes (minutes) above 25 mmHg and slightly longer episodes (20 min) of ICP 20-25 mmHg correlated with unfavorable outcome. For PRx, brief episodes above 0.25 as well as slightly lower values (around 0) for longer periods of time (30 min) were associated with unfavorable outcome. For CPP, there was a transition from favorable to unfavorable outcome for CPP below 50 mmHg. There was no association between high CPP and outcome. For ∆CPPopt, there was a transition from favorable to unfavorable outcome when ∆CPPopt went below -10 mmHg. No association was found for positive ∆CPPopt values and outcome.

CONCLUSIONS

This visualization method illustrated the combined effect of insult intensity and duration in relation to outcome in severe pediatric TBI, supporting previous notions to avoid high ICP and low CPP for longer episodes of time. In addition, higher PRx for longer episodes of time and CPP below CPPopt more than -10 mmHg were associated with worse outcome, indicating a potential role for autoregulatory-oriented management in pediatric TBI.

Regional disparity in continuously measured time-domain cerebrovascular reactivity indices: a scoping review of human literature

Objective: Cerebral blood vessels maintaining relatively constant cerebral blood flow (CBF) over wide range of systemic arterial blood pressure (ABP) is referred to as cerebral autoregulation (CA). Impairments in CA expose the brain to pressure-passive flow states leading to hypoperfusion and hyperperfusion. Cerebrovascular reactivity (CVR) metrics refer to surrogate metrics of pressure-based CA that evaluate the relationship between slow vasogenic fluctuations in cerebral perfusion pressure/ABP and a surrogate for pulsatile CBF/cerebral blood volume.Approach: We performed a systematically conducted scoping review of all available human literature examining the association between continuous CVR between more than one brain region/channel using the same CVR index.Main Results: In all the included 22 articles, only handful of transcranial doppler (TCD) and near-infrared spectroscopy (NIRS) based metrics were calculated for only two brain regions/channels. These metrics found no difference between left and right sides in healthy volunteer, cardiac surgery, and intracranial hemorrhage patient studies. In contrast, significant differences were reported in endarterectomy, and subarachnoid hemorrhage studies, while varying results were found regarding regional disparity in stroke, traumatic brain injury, and multiple population studies.Significance: Further research is required to evaluate regional disparity using NIRS-based indices and to understand if NIRS-based indices provide better regional disparity information than TCD-based indices.

Multimodal and autoregulation monitoring in the neurointensive care unit

Given the complexity of cerebral pathology in patients with acute brain injury, various neuromonitoring strategies have been developed to better appreciate physiologic relationships and potentially harmful derangements. There is ample evidence that bundling several neuromonitoring devices, termed "multimodal monitoring," is more beneficial compared to monitoring individual parameters as each may capture different and complementary aspects of cerebral physiology to provide a comprehensive picture that can help guide management. Furthermore, each modality has specific strengths and limitations that depend largely on spatiotemporal characteristics and complexity of the signal acquired. In this review we focus on the common clinical neuromonitoring techniques including intracranial pressure, brain tissue oxygenation, transcranial doppler and near-infrared spectroscopy with a focus on how each modality can also provide useful information about cerebral autoregulation capacity. Finally, we discuss the current evidence in using these modalities to support clinical decision making as well as potential insights into the future of advanced cerebral homeostatic assessments including neurovascular coupling.

Beyond intracranial pressure: monitoring cerebral perfusion and autoregulation in severe traumatic brain injury

PURPOSE OF REVIEW

Severe traumatic brain injury (TBI) remains the most prevalent neurological condition worldwide. Observational and interventional studies provide evidence to recommend monitoring of intracranial pressure (ICP) in all severe TBI patients. Existing guidelines focus on treating elevated ICP and optimizing cerebral perfusion pressure (CPP), according to fixed universal thresholds. However, both ICP and CPP, their target thresholds, and their interaction, need to be interpreted in a broader picture of cerebral autoregulation, the natural capacity to adjust cerebrovascular resistance to preserve cerebral blood flow in response to external stimuli.

RECENT FINDINGS

Cerebral autoregulation is often impaired in TBI patients, and monitoring cerebral autoregulation might be useful to develop personalized therapy rather than treatment of one size fits all thresholds and guidelines based on unidimensional static relationships.

SUMMARY

Today, there is no gold standard available to estimate cerebral autoregulation. Cerebral autoregulation can be triggered by performing a mean arterial pressure (MAP) challenge, in which MAP is increased by 10% for 20 min. The response of ICP (increase or decrease) will estimate the status of cerebral autoregulation and can steer therapy mainly concerning optimizing patient-specific CPP. The role of cerebral metabolic changes and its relationship to cerebral autoregulation is still unclear and awaits further investigation.

ICP, CPP, and PRx in traumatic brain injury and aneurysmal subarachnoid hemorrhage: association of insult intensity and duration with clinical outcome

OBJECTIVE

The primary aim of this study was to determine the combined effect of insult intensity and duration of intracranial pressure (ICP), cerebral perfusion pressure (CPP), and pressure reactivity index (PRx) on outcome measured with the Glasgow Outcome Scale-Extended (GOS-E) in patients with traumatic brain injury (TBI) or aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

This observational study included all TBI and aSAH patients treated in the neurointensive care unit in Uppsala, Sweden, 2008-2018, with at least 24 hours of ICP monitoring during the first 10 days following injury and available long-term clinical outcome data. ICP, CPP, and PRx insults were visualized as 2D plots to highlight the effects of both insult intensity and duration on patient outcome.

RESULTS

Of 950 included patients, 436 were TBI and 514 aSAH patients. The TBI patients were younger, more often male, and exhibited worse neurological status at admission, but recovered more favorably than the aSAH patients. There was a transition from good to poor outcome with ICP above 15-20 mm Hg in both TBI and aSAH. The two diagnoses had opposite CPP patterns. In TBI patients, CPP episodes at or below 80 mm Hg were generally favorable, whereas CPP episodes above 80 mm Hg were favorable in the aSAH patients. In the TBI patients there was a transition from good to poor outcome when PRx exceeded zero, but no evident transition was found in the aSAH cohort.

CONCLUSIONS

The insult intensity and duration plots formulated in this study illustrate the similarities and differences between TBI and aSAH patients. In particular, aSAH patients may benefit from much higher CPP targets than TBI patients.

High spatial and temporal resolution cerebrovascular reactivity for humans and large mammals: A technological description of integrated fNIRS and niABP mapping system

Introduction: The process of cerebral vessels maintaining cerebral blood flow (CBF) fairly constant over a wide range of arterial blood pressure is referred to as cerebral autoregulation (CA). Cerebrovascular reactivity is the mechanism behind this process, which maintains CBF through constriction and dilation of cerebral vessels. Traditionally CA has been assessed statistically, limited by large, immobile, and costly neuroimaging platforms. However, with recent technology advancement, dynamic autoregulation assessment is able to provide more detailed information on the evolution of CA over long periods of time with continuous assessment. Yet, to date, such continuous assessments have been hampered by low temporal and spatial resolution systems, that are typically reliant on invasive point estimations of pulsatile CBF or cerebral blood volume using commercially available technology. Methods: Using a combination of multi-channel functional near-infrared spectroscopy and non-invasive arterial blood pressure devices, we were able to create a system that visualizes CA metrics by converting them to heat maps drawn on a template of human brain. Results: The custom Python heat map module works in "offline" mode to visually portray the CA index per channel with the use of colourmap. The module was tested on two different mapping grids, 8 channel and 24 channel, using data from two separate recordings and the Python heat map module was able read the CA indices file and represent the data visually at a preselected rate of 10 s. Conclusion: The generation of the heat maps are entirely non-invasive, with high temporal and spatial resolution by leveraging the recent advances in NIRS technology along with niABP. The CA mapping system is in its initial stage and development plans are ready to transform it from "offline" to real-time heat map generation.

Feasibility of non-invasive neuromonitoring in general intensive care patients using a multi-parameter transcranial Doppler approach

PURPOSE

To assess the feasibility of Transcranial Doppler ultrasonography (TCD) neuromonitoring in a general intensive care environment, in the prognosis and outcome prediction of patients who are in coma due to a variety of critical conditions.

METHODS

The prospective trial was performed between March 2017 and March 2019 Addenbrooke's Hospital, Cambridge, UK. Forty adult patients who failed to awake appropriately after resuscitation from cardiac arrest or were in coma due to conditions such as meningitis, seizures, sepsis, metabolic encephalopathies, overdose, multiorgan failure or transplant were eligible for inclusion. Gathered data included admission diagnosis, duration of ventilation, length of stay in the ICU, length of stay in hospital, discharge status using Cerebral Performance Categories (CPC). All patients received intermittent extended TCD monitoring following inclusion in the study. Parameters of interest included TCD-based indices of cerebral autoregulation, non-invasive intracranial pressure, autonomic system parameters (based on heart rate variability), critical closing pressure, the cerebrovascular time constant and indices describing the shape of the TCD pulse waveform.

RESULTS

Thirty-seven patients were included in the final analysis, with 21 patients classified as good outcome (CPC 1-2) and 16 as poor neurological outcomes (CPC 3-5). Three patients were excluded due to inadequacies identified in the TCD acquisition. The results indicated that irrespective of the primary diagnosis, non-survivors had significantly disturbed cerebral autoregulation, a shorter cerebrovascular time constant and a more distorted TCD pulse waveform (all p<0.05).

CONCLUSIONS

Preliminary results from the trial indicate that multi-parameter TCD neuromonitoring increases outcome-predictive power and TCD-based indices can be applied to general intensive care monitoring.

Prediction of Intracranial Hypertension and Brain Tissue Hypoxia Utilizing High-Resolution Data from the BOOST-II Clinical Trial

The current approach to intracranial hypertension and brain tissue hypoxia is reactive, based on fixed thresholds. We used statistical machine learning on high-frequency intracranial pressure (ICP) and partial brain tissue oxygen tension (PbtO₂) data obtained from the BOOST-II trial with the goal of constructing robust quantitative models to predict ICP/PbtO₂ crises. We derived the following machine learning models: logistic regression (LR), elastic net, and random forest. We split the data set into 70–30% for training and testing and utilized a discrete-time survival analysis framework and 5-fold hyperparameter optimization strategy for all models. We compared model performances on discrimination between events and non-events of increased ICP or low PbtO₂ with the area under the receiver operating characteristic (AUROC) curve. We further analyzed clinical utility through a decision curve analysis (DCA). When considering discrimination, the number of features, and interpretability, we identified the RF model that combined the most recent ICP reading, episode number, and longitudinal trends over the preceding 30 min as the best performing for predicting ICP crisis events within the next 30 min (AUC 0.78). For PbtO₂, the LR model utilizing the most recent reading, episode number, and longitudinal trends over the preceding 30 min was the best performing (AUC, 0.84). The DCA showed clinical usefulness for wide risk of thresholds for both ICP and PbtO₂ predictions. Acceptable alerting thresholds could range from 20% to 80% depending on a patient-specific assessment of the benefit-risk ratio of a given intervention in response to the alert.

Achieving good neurological outcome by combining decompressive craniectomy for acute subdural hematoma and transarterial embolization of intraperitoneal injured arteries for multiple severe trauma: a case report

A 22-year-old woman jumped from the 4th floor of her apartment in an attempt to commit suicide. Whole-body computed tomography showed multiple injuries, including right acute subdural hematoma, left hemopneumothorax, several fractures, intraperitoneal hemorrhage, and spleen injury. Her consciousness deteriorated rapidly, and her right pupil was dilated. Furthermore, she had unstable vital signs including blood pressure of approximately 70/40 mmHg, pulse about 150/minute, respiratory rate 25/minute, and percutaneous oxygen saturation of 90% on 10 L oxygen. Intratracheal intubation and insertion of a thoracostomy tube were performed in the emergency room. Due to concomitant brain herniation and hemorrhagic shock, simultaneous decompressive craniectomy for acute subdural hematoma and transarterial embolization of intraperitoneal injured arteries were performed in our hybrid operating room. Despite rapid blood transfusions, the blood pressure did not increase. After starting embolization of the injured arteries of the spleen, the blood pressure increased, thereby making it possible to remove the acute subdural hematoma, and hemostasis was then achieved. Four hours later, the acute subdural hematoma and intracranial pressure increased again, and re-operation was performed in the normal operating room. Cranioplasty and clavicular fracture reduction were performed 14 days later. She recovered enough to talk and walk, and her consciousness stabilized. Interviews with her and her family by a psychiatrist determined that abnormal behaviors had first appeared 2 months earlier. She was diagnosed with acute and transient psychotic disorders, and treatment was started. The patient was discharged home 1 month later with mild disability of her higher-order brain function.

Cerebral Autoregulation Monitoring in Traumatic Brain Injury: An Overview of Recent Advances in Personalized Medicine

Impaired cerebral autoregulation (CA) in moderate/severe traumatic brain injury (TBI) has been identified as a strong associate with poor long-term outcomes, with recent data highlighting its dominance over cerebral physiologic dysfunction seen in the acute phase post injury. With advances in bedside continuous cerebral physiologic signal processing, continuously derived metrics of CA capacity have been described over the past two decades, leading to improvements in cerebral physiologic insult detection and development of novel personalized approaches to TBI care in the intensive care unit (ICU). This narrative review focuses on highlighting the concept of continuous CA monitoring and consequences of impairment in moderate/severe TBI. Further, we provide a comprehensive description and overview of the main personalized cerebral physiologic targets, based on CA monitoring, that are emerging as strong associates with patient outcomes. CA-based personalized targets, such as optimal cerebral perfusion pressure (CPPopt), lower/upper limit of regulation (LLR/ULR), and individualized intra-cranial pressure (iICP) are positioned to change the way we care for TBI patients in the ICU, moving away from the "one treatment fits all" paradigm of current guideline-based therapeutic approaches, towards a true personalized medicine approach tailored to the individual patient. Future perspectives regarding research needs in this field are also discussed.

Multimodal brain monitoring following traumatic brain injury: A primer for intensive care practitioners

Traumatic brain injury (TBI) is common and potentially devastating. Traditional examination-based patient monitoring following TBI may be inadequate for frontline clinicians to reduce secondary brain injury through individualized therapy. Multimodal neurologic monitoring (MMM) offers great potential for detecting early injury and improving outcomes. By assessing cerebral oxygenation, autoregulation and metabolism, clinicians may be able to understand neurophysiology during acute brain injury, and offer therapies better suited to each patient and each stage of injury. Hence, we offer this primer on brain tissue oxygen monitoring, pressure reactivity index monitoring and cerebral microdialysis. This narrative review serves as an introductory guide to the latest clinically-relevant evidence regarding key neuromonitoring techniques.

Individualized cerebral perfusion pressure in acute neurological injury: are we ready for clinical use?

PURPOSE OF REVIEW

Individualizing cerebral perfusion pressure based on cerebrovascular autoregulation assessment is a promising concept for neurological injuries where autoregulation is typically impaired. The purpose of this review is to describe the status quo of autoregulation-guided protocols and discuss steps towards clinical use.

RECENT FINDINGS

Retrospective studies have indicated an association of impaired autoregulation and poor clinical outcome in traumatic brain injury (TBI), hypoxic-ischemic brain injury (HIBI) and aneurysmal subarachnoid hemorrhage (aSAH). The feasibility and safety to target a cerebral perfusion pressure optimal for cerebral autoregulation (CPPopt) after TBI was recently assessed by the COGITATE trial. Similarly, the feasibility to calculate a MAP target (MAPopt) based on near-infrared spectroscopy was demonstrated for HIBI. Failure to meet CPPopt is associated with the occurrence of delayed cerebral ischemia in aSAH but interventional trials in this population are lacking. No level I evidence is available on potential effects of autoregulation-guided protocols on clinical outcomes.

SUMMARY

The effect of autoregulation-guided management on patient outcomes must still be demonstrated in prospective, randomized, controlled trials. Selection of disease-specific protocols and endpoints may serve to evaluate the overall benefit from such approaches.

Perioperative Management of Polytrauma Patients with Severe Traumatic Brain Injury Undergoing Emergency Extracranial Surgery: A Narrative Review

Managing the acute phase after a severe traumatic brain injury (TBI) with polytrauma represents a challenging situation for every trauma team member. A worldwide variability in the management of these complex patients has been reported in recent studies. Moreover, limited evidence regarding this topic is available, mainly due to the lack of well-designed studies. Anesthesiologists, as trauma team members, should be familiar with all the issues related to the management of these patients. In this narrative review, we summarize the available evidence in this setting, focusing on perioperative brain protection, cardiorespiratory optimization, and preservation of the coagulative function. An overview on simultaneous multisystem surgery (SMS) is also presented.

Continuous Time-Domain Cerebrovascular Reactivity Metrics and Discriminate Capacity for the Upper and Lower Limits of Autoregulation: A Scoping Review of the Animal Literature

Over a wide range of systemic arterial pressures, cerebral blood flow (CBF) is regulated fairly constantly by the cerebral vessels in a process termed cerebral autoregulation (CA), which is depicted by the Lassen autoregulatory curve. After traumatic brain injury (TBI), CA can get impaired and these impairments manifest in changes of the Lassen autoregulatory curve. Continuous surrogate metrics of pressure-based CA, termed cerebrovascular reactivity (CVR) metrics, evaluate the relationship between slow vasogenic fluctuations in a driving pressure for cerebral blood flow, and the most commonly studied and utilized measures are based in the time domain and have been increasingly applied in bedside TBI care and have sparked the investigation of individualized cerebral perfusion pressure targets. However, not all CVR metrics have been validated as true measures of autoregulation in the pre-clinical setting. We reviewed all available pre-clinical animal literature that assessed the association between continuous time-domain metrics of CVR and some aspect of the Lassen autoregulatory curve. All 15 articles found associated the evaluated continuous metrics to the lower limit of autoregulation curve whereas none looked at the upper limit. Most of the evaluated metrics showed the ability to discriminate the lower limit of autoregulation with various methods of perturbation. Further work is required to evaluate the utility of such surrogate measures against the upper limit of autoregulation, while also providing validation to the existing literature supporting specific indices and their ability to discriminate the lower limit.

Association of Age and Sex With Multi-Modal Cerebral Physiology in Adult Moderate/Severe Traumatic Brain Injury: A Narrative Overview and Future Avenues for Personalized Approaches

The impact of age and biological sex on outcome in moderate/severe traumatic brain injury (TBI) has been documented in large cohort studies, with advanced age and male sex linked to worse long-term outcomes. However, the association between age/biological sex and high-frequency continuous multi-modal monitoring (MMM) cerebral physiology is unclear, with only sparing reference made in guidelines and major literature in moderate/severe TBI. In this narrative review, we summarize some of the largest studies associating various high-frequency MMM parameters with age and biological sex in moderate/severe TBI. To start, we present this by highlighting the representative available literature on high-frequency data from Intracranial Pressure (ICP), Cerebral Perfusion Pressure (CPP), Extracellular Brain Tissue Oxygenation (PbtO₂), Regional Cerebral Oxygen Saturations (rSO₂), Cerebral Blood Flow (CBF), Cerebral Blood Flow Velocity (CBFV), Cerebrovascular Reactivity (CVR), Cerebral Compensatory Reserve, common Cerebral Microdialysis (CMD) Analytes and their correlation to age and sex in moderate/severe TBI cohorts. Then we present current knowledge gaps in the literature, discuss biological implications of age and sex on cerebrovascular monitoring in TBI and some future avenues for bedside research into the cerebrovascular physiome after TBI.

The utility of physician-staffed helicopters for managing individuals who experience severe isolated head trauma

Objective: The authors retrospectively investigated prognostic factors for severe isolated head trauma in patients evacuated by a physician-staffed helicopter emergency medical service (HEMS) or ground ambulance using data from the Japan Trauma Data Bank (JTDB).

Patients and Methods: This study was a retrospective analysis of data housed in the JTDB database. The study period was from January 2004 to May 2019. Subjects were divided into two groups according to the method of transportation: helicopter (i.e., HEMS), which included patients transported by a physician-staffed helicopter; and ambulance, which included patients transported by ground ambulance.

Results: A total of 41,358 patients were enrolled in the study, including 2,029 in the helicopter group and 39,329 in the ambulance group. The ratio of males, median head Abbreviated Injury Scale and Injury Severity Scale (ISS) scores were significantly greater in the helicopter group than in the ambulance group, while the average age, median Glasgow Coma Scale, average Revised Trauma Score (RTS), and survival rate were significantly lower in the helicopter group than in the ambulance group. Of the variables that demonstrated statistical significance in the univariate analysis and classification of transportation and included in the multivariate analysis, the following were identified as significant predictors of survival outcomes: younger age, lower ISS, female sex, and greater RTS. HEMS was not a significant predictor of survival.

Conclusion: The present study revealed no effect of HEMS transport on the outcomes of patients who experienced severe isolated head trauma compared with ground ambulance transportation. Further prospective studies, including an analysis of the operation time or distance traveled by the HEMS and the functional outcome(s) of patients with severe head injury transported by HEMS, are warranted.

Targeting Autoregulation-Guided Cerebral Perfusion Pressure after Traumatic Brain Injury (COGiTATE): A Feasibility Randomized Controlled Clinical Trial

Managing traumatic brain injury (TBI) patients with a cerebral perfusion pressure (CPP) near to the cerebral autoregulation (CA)-guided "optimal" CPP (CPPopt) value is associated with improved outcome and might be useful to individualize care, but has never been prospectively evaluated. This study evaluated the feasibility and safety of CA-guided CPP management in TBI patients requiring intracranial pressure monitoring and therapy (TBIicp patients). The CPPopt Guided Therapy: Assessment of Target Effectiveness (COGiTATE) parallel two-arm feasibility trial took place in four tertiary centers. TBIicp patients were randomized to either the Brain Trauma Foundation (BTF) guideline CPP target range (control group) or to the individualized CA-guided CPP targets (intervention group). CPP targets were guided by six times daily software-based alerts for up to 5 days. The primary feasibility end-point was the percentage of time with CPP concordant (±5 mm Hg) with the set CPP targets. The main secondary safety end-point was an increase in therapeutic intensity level (TIL) between the control and intervention group. Twenty-eight patients were randomized to the control and 32 patients to the intervention group. CPP in the intervention group was in the target range for 46.5% (interquartile range, 41.2-58) of the monitored time, significantly higher than the feasibility target specified in the published protocol (36%; p < 0.001). There were no significant differences between groups for TIL or for other safety end-points. Conclusively, targeting an individual and dynamic CA-guided CPP is feasible and safe in TBIicp patients. This encourages a prospective trial powered for clinical outcomes.

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

BACKGROUND

Several 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.

AIM

To 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.

METHODS

A 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.

RESULTS

Consensus 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.

CONCLUSION

The 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.

The impact of hypertonic saline on cerebrovascular reactivity and compensatory reserve in traumatic brain injury: an exploratory analysis

Background

Intravenous hypertonic saline is utilized commonly in critical care for treatment of acute or refractory elevations of intracranial pressure (ICP) in traumatic brain injury (TBI) patients. Though there is a clear understanding of the general physiological effects of a hypertonic saline solution over long periods of time, smaller epoch effects of hypertonic saline (HTS) have not been thoroughly analyzed. The aim of this study was to perform a direct evaluation of the high-frequency response of HTS on the cerebrovascular physiological responses in TBI.

Methods

We retrospectively reviewed our prospectively maintained adult TBI database for those with archived high-frequency cerebral physiology and available HTS treatment information. We evaluated different epochs of physiology around HTS bolus dosing, comparing pre- with post-HTS. We assessed for changes in slow fluctuations in ICP, pulse amplitude of ICP (AMP), cerebral perfusion pressure (CPP), mean arterial pressure (MAP), cerebrovascular reactivity (as measured through pressure reactivity index (PRx)), and cerebral compensatory reserve (correlation (R) between AMP (A) and ICP (P)). Comparisons of mean measures and percentage time above clinically relevant thresholds for the physiological parameters were compared pre- and post-HTS using descriptive statistics and Mann-Whitney U testing. We assessed for subgroups of physiological responses using latent profile analysis (LPA).

Results

Fifteen patients underwent 69 distinct bolus infusions of hypertonic saline. Apart from the well-documented decrease in ICP, there was also a reduction in AMP. The analysis of cerebrovascular reactivity response to HTS solution had two main effects. For patients with grossly impaired cerebrovascular reactivity pre-HTS (PRx > + 0.30), HTS bolus led to improved reactivity. However, for those with intact cerebrovascular reactivity pre-HTS (PRx < 0), HTS bolus demonstrated a trend towards more impaired reactivity. This indicates that HTS has different impacts, dependent on pre-bolus cerebrovascular status. There was no significant change in metrics of cerebral compensatory reserve. LPA failed to demonstrate any subgroups of physiological responses to HTS administration.

Conclusions

The direct decrease in ICP and AMP confirms that a bolus dose of a HTS solution is an effective therapeutic agent for intracranial hypertension. However, in patients with intact autoregulation, hypertonic saline may impair cerebral hemodynamics. These findings regarding cerebrovascular reactivity remain preliminary and require further investigation.

Electronic supplementary material

The online version of this article (10.1007/s00701-020-04579-0) contains supplementary material, which is available to authorized users.

Alternative continuous intracranial pressure-derived cerebrovascular reactivity metrics in traumatic brain injury: a scoping overview

BACKGROUND

Pressure reactivity index (PRx) has emerged as a means to continuously monitor cerebrovascular reactivity in traumatic brain injury (TBI). However, other intracranial pressure (ICP)-based continuous metrics exist, and may have advantages over PRx. The goal of this study was to perform a scoping overview of the literature on non-PRx ICP-based continuous cerebrovascular reactivity metrics in adult TBI.

METHODS

We searched MEDLINE, BIOSIS, EMBASE, Global Health, SCOPUS, and Cochrane Library from inception to December 2019. Using a two-stage filtering of title/abstract, and then full manuscript, we identified pertinent articles. Data was abstracted to tables and each technique summarized, including pulse amplitude index (PAx), correlation between pulse amplitude of ICP and cerebral perfusion pressure (RAC), PRx_55-15, and low-resolution metrics LAx and L-PRx.

RESULTS

A total of 23 articles met the inclusion criteria, with the vast majority being retrospective in nature and based out of European centers. Sixteen articles focused on high-resolution metrics PAx, RAC, and PRx_55-15, with 6 articles focusing on LAx and L-PRx. PAx may have a role in low ICP situations, where it appears to perform superior to PRx. RAC displays similar behavior to PRx, with a trend to stronger associations with favorable/unfavorable outcome at 6 months, and stronger parabolic relationship with CPP. PRx_55-15 provides a focused assessment on the vasogenic frequency range associated with cerebral autoregulation, with preliminary data supporting a strong association with outcome in TBI. LAx and L-PRx display varying associations with 6-month outcome in TBI, depending on the window length of calculation, with shorter windows demonstrating stronger correlations with classical PRx.

CONCLUSIONS

Non-PRx continuous ICP-based cerebrovascular reactivity metrics can be split into high-resolution and low-resolution measures. High-resolution indices include PAx, RAC, and PRx_55-15, while low-resolution indices include L-PRx and LAx. The true role for these metrics beyond classic PRx remains unclear. Each displays situations where it may prove superior over PRx, given limitations with this currently widely accepted measure. Much future investigation into each of these alternative metrics is required prior to adoption into the clinical monitoring armamentarium in adult TBI.

Continuous cerebrovascular reactivity monitoring in moderate/severe traumatic brain injury: a narrative review of advances in neurocritical care

Impaired cerebrovascular reactivity in adult moderate and severe traumatic brain injury (TBI) is known to be associated with worse global outcome at 6-12 months. As technology has improved over the past decades, monitoring of cerebrovascular reactivity has shifted from intermittent measures, to experimentally validated continuously updating indices at the bedside. Such advances have led to the exploration of individualised physiologic targets in adult TBI management, such as optimal cerebral perfusion pressure (CPP) values, or CPP limits in which vascular reactivity is relatively intact. These targets have been shown to have a stronger association with outcome compared with existing consensus-based guideline thresholds in severe TBI care. This has sparked ongoing prospective trials of such personalised medicine approaches in adult TBI. In this narrative review paper, we focus on the concept of cerebral autoregulation, proposed mechanisms of control and methods of continuous monitoring used in TBI. We highlight multimodal cranial monitoring approaches for continuous cerebrovascular reactivity assessment, physiologic and neuroimaging correlates, and associations with outcome. Finally, we explore the recent 'state-of-the-art' advances in personalised physiologic targets based on continuous cerebrovascular reactivity monitoring, their benefits, and implications for future avenues of research in TBI.

The CAnadian High-Resolution Traumatic Brain Injury (CAHR-TBI) Research Collaborative

In traumatic brain injury (TBI), future integration of multimodal monitoring of cerebral physiology and high-frequency signal processing techniques, with advanced neuroimaging, proteomic and genomic analysis, provides an opportunity to explore the molecular pathways involved in various aspects of cerebral physiologic dysfunction in vivo. The main issue with early and rapid discovery in this field of personalized medicine is the expertise and complexity of data involved. This brief communication highlights the CAnadian High-Resolution Traumatic Brain Injury (CAHR-TBI) Research Collaborative, which has been formed from centers with specific expertise in the area of high-frequency physiologic monitoring/processing, and outlines its objectives.

A National Trial on Differences in Cerebral Perfusion Pressure Values by Measurement Location

BACKGROUND

Cerebral perfusion pressure (CPP) is a key parameter in management of brain injury with suspected impaired cerebral autoregulation. CPP is calculated by subtracting intracranial pressure (ICP) from mean arterial pressure (MAP). Despite consensus on importance of CPP monitoring, substantial variations exist on anatomical reference points used to measure arterial MAP when calculating CPP. This study aimed to identify differences in CPP values based on measurement location when using phlebostatic axis (PA) or tragus (Tg) as anatomical reference points. The secondary study aim was to determine impact of differences on patient outcomes at discharge.

METHODS

This was a prospective, repeated measures, multi-site national trial. Adult ICU patients with neurological injury necessitating ICP and CPP monitoring were consecutively enrolled from seven sites. Daily MAP/ICP/CPP values were gathered with the arterial transducer at the PA, followed by the Tg as anatomical reference points.

RESULTS

A total of 136 subjects were enrolled, resulting in 324 paired observations. There were significant differences for CPP when comparing values obtained at PA and Tg reference points (p < 0.000). Differences remained significant in repeated measures model when controlling for clinical factors (mean CPP-PA = 80.77, mean CPP-Tg = 70.61, p < 0.000). When categorizing CPP as binary endpoint, 18.8% of values were identified as adequate with PA values, yet inadequate with CPP values measured at the Tg.

CONCLUSION

Findings identify numerical differences for CPP based on anatomical reference location and highlight importance of a standard reference point for both clinical practice and future trials to limit practice variations and heterogeneity of findings.

Intracranial Hypertension and Cerebral Perfusion Pressure Insults in Adult Hypertensive Intraventricular Hemorrhage: Occurrence and Associations With Outcome

OBJECTIVES

Elevated intracranial pressure and inadequate cerebral perfusion pressure may contribute to poor outcomes in hypertensive intraventricular hemorrhage. We characterized the occurrence of elevated intracranial pressure and low cerebral perfusion pressure in obstructive intraventricular hemorrhage requiring extraventricular drainage.

DESIGN

Prospective observational cohort.

SETTING

ICUs of 73 academic hospitals.

PATIENTS

Four hundred ninety-nine patients enrolled in the CLEAR III trial, a multicenter, randomized study to determine if extraventricular drainage plus intraventricular alteplase improved outcome versus extraventricular drainage plus saline.

INTERVENTIONS

Intracranial pressure and cerebral perfusion pressure were recorded every 4 hours, analyzed over a range of thresholds, as single readings or spans (≥ 2) of readings after adjustment for intracerebral hemorrhage severity. Impact on 30- and 180-days modified Rankin Scale scores was assessed, and receiver operating curves were analyzed to identify optimal thresholds.

MEASUREMENTS AND MAIN RESULTS

Of 21,954 intracranial pressure readings, median interquartile range 12 mm Hg (8-16), 9.7% were greater than 20 mm Hg and 1.8% were greater than 30 mm Hg. Proportion of intracranial pressure readings from greater than 18 to greater than 30 mm Hg and combined intracranial pressure greater than 20 plus cerebral perfusion pressure less than 70 mm Hg were associated with day-30 mortality and partially mitigated by intraventricular alteplase. Proportion of cerebral perfusion pressure readings from less than 65 to less than 90 mm Hg and intracranial pressure greater than 20 mm Hg in spans were associated with both 30-day mortality and 180-day mortality. Proportion of cerebral perfusion pressure readings from less than 65 to less than 90 mm Hg and combined intracranial pressure greater than 20 plus cerebral perfusion pressure less than 60 mm Hg were associated with poor day-30 modified Rankin Scale, whereas cerebral perfusion pressure less than 65 and less than 75 mm Hg were associated with poor day-180 modified Rankin Scale.

CONCLUSIONS

Elevated intracranial pressure and inadequate cerebral perfusion pressure are not infrequent during extraventricular drainage for severe intraventricular hemorrhage, and level and duration predict higher short-term mortality and long-term mortality. Burden of low cerebral perfusion pressure was also associated with poor short- and long-term outcomes and may be more significant than intracranial pressure. Adverse consequences of intracranial pressure-time burden and cerebral perfusion pressure-time burden should be tested prospectively as potential thresholds for therapeutic intervention.

Resuscitation Strategies for Traumatic Brain Injury

PURPOSE OF REVIEW

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality; however, little definitive evidence exists about most clinical management strategies. Here, we highlight important differences between two major guidelines, the 2016 Brain Trauma Foundation guidelines and the Lund Concept, along with recent pre-clinical and clinical data.

RECENT FINDINGS

While intracranial pressure (ICP) monitoring has been questioned, the majority of literature demonstrates benefit in severe TBI. The optimal cerebral perfusion pressure (CPP) and ICP are yet unknown, but likely as important is the concept of ICP burden. The evidence for anti-hypertensive therapy is strengthening. Decompressive craniectomy improves mortality, but at the cost of increased morbidity. Plasma-based resuscitation has demonstrated benefit in multiple pre-clinical TBI studies.

SUMMARY

The management of hemodynamics and intravascular volume are crucial in TBI. Based on recent evidence, ICP monitoring, anti-hypertensive therapy, minimal use of vasopressors/inotropes, and plasma resuscitation may improve outcomes.

Translational approach towards determining the role of cerebral autoregulation in outcome after traumatic brain injury

Cerebral autoregulation is impaired after traumatic brain injury (TBI), contributing to poor outcome. In the context of the neurovascular unit, cerebral autoregulation contributes to neuronal cell integrity and clinically Glasgow Coma Scale is correlated to intactness of autoregulation after TBI. Cerebral Perfusion Pressure (CPP) is often normalized by use of vasoactive agents to increase mean arterial pressure (MAP) and thereby limit impairment of cerebral autoregulation and neurological deficits. However, current vasoactive agent choice used to elevate MAP to increase CPP after TBI is variable. Vasoactive agents, such as phenylephrine, dopamine, norepinephrine, and epinephrine, clinically have not sufficiently been compared regarding effect on CPP, autoregulation, and survival after TBI. The cerebral effects of these clinically commonly used vasoactive agents are incompletely understood. This review will describe translational studies using a more human like animal model (the pig) of TBI to identify better therapeutic strategies to improve outcome post injury. These studies also investigated the role of age and sex in outcome and mechanism(s) involved in improvement of outcome in the setting of TBI. Additionally, this review considers use of inhaled nitric oxide as a novel neuroprotective strategy in treatment of TBI.

Preserve encephalus in surgery of trauma: online survey. (P.E.S.T.O)

Background

Traumatic brain injury (TBI) is a global health problem. Extracranial hemorrhagic lesions needing emergency surgery adversely affect the outcome of TBI. We conducted an international survey regarding the acute phase management practices in TBI polytrauma patients.

Methods

A questionnaire was available on the World Society of Emergency Surgery website between December 2017 and February 2018. The main endpoints were the evaluation of (1) intracranial pressure (ICP) monitoring during extracranial emergency surgery (EES), (2) hemodynamic management without ICP monitoring during EES, (3) coagulation management, and (4) utilization of simultaneous multisystem surgery (SMS).

Results

The respondents were 122 representing 105 trauma centers worldwide. ICP monitoring was utilized in 10–30% of patients at risk of intracranial hypertension (IH) undergoing EES from about a third of the respondents [n = 35 (29%)]. The respondents reported that the safest values of systolic blood pressure during EES in patients at risk of IH were 90–100 mmHg [n = 35 (29%)] and 100–110 mmHg [n = 35 (29%)]. The safest values of mean arterial pressure during EES in patients at risk of IH were > 70 mmHg [n = 44 (36%)] and > 80 mmHg [n = 32 (26%)]. Regarding ICP placement, a large percentage of respondents considered a platelet (PLT) count > 50,000/mm³ [n = 57 (47%)] and a prothrombin time (PT)/activated partial thromboplastin time (aPTT) < 1.5 times the normal control [n = 73 (60%)] to be the safest parameters. For craniotomy, the majority of respondents considered PLT count > 100,000/mm³ [n = 67 (55%)] and a PT/aPTT < 1.5 times the normal control [n = 76 (62%)] to be the safest parameters. Almost half of the respondents [n = 53 (43%)], reported that they transfused red blood cells (RBCs)/plasma (P)/PLTs at a ratio of 1/1/1 in TBI polytrauma patients. SMS was performed in 5–19% of patients, requiring both an emergency neurosurgical operation and EES, by almost half of the respondents [n = 49 (40%)].

Conclusions

A great variability in practices during the acute phase management of polytrauma patients with severe TBI was identified. These findings may be helpful for future investigations and educational purposes.

Electronic supplementary material

The online version of this article (10.1186/s13017-019-0229-2) contains supplementary material, which is available to authorized users.

Fluid Management in Acute Brain Injury

PURPOSE OF THE REVIEW

The aims of fluid management in acute brain injury are to preserve or restore physiology and guarantee appropriate tissue perfusion, avoiding potential iatrogenic effects. We reviewed the literature, focusing on the clinical implications of the selected papers. Our purposes were to summarize the principles regulating the distribution of water between the intracellular, interstitial, and plasma compartments in the normal and the injured brain, and to clarify how these principles could guide fluid administration, with special reference to intracranial pressure control.

RECENT FINDINGS

Although a considerable amount of research has been published on this topic and in general on fluid management in acute illness, the quality of the evidence tends to vary. Intravascular volume management should aim for euvolemia. There is evidence of harm with aggressive administration of fluid aimed at achieving hypervolemia in cases of subarachnoid hemorrhage. Isotonic crystalloids should be the preferred agents for volume replacement, while colloids, glucose-containing hypotonic solutions, and other hypotonic solutions or albumin should be avoided. Osmotherapy seems to be effective in intracranial hypertension management; however, there is no clear evidence regarding the superiority of hypertonic saline over mannitol. Fluid therapy plays an important role in the management of acute brain injury patients. However, fluids are a double-edged weapon because of the potential risk of hyper-hydration, hypo- or hyper-osmolar conditions, which may unfavorably affect the clinical course and the outcome.

Effect of the Hybrid Emergency Room System on Functional Outcome in Patients with Severe Traumatic Brain Injury

OBJECTIVE

The timely treatment of severe traumatic brain injury (TBI) is essential for limiting the effects of damage; however, there is no consensus regarding an effective method for early intervention. In August 2011, our hospital launched a novel trauma workflow using the hybrid emergency room (ER), consisting of an interventional radiology-computed tomography (CT) unit installed in the trauma resuscitation room to facilitate early interventions. The aim of this study was to evaluate effects of the hybrid ER system on functional outcomes in patients with severe TBI.

METHODS

We conducted a retrospective historical control study of patients with severe TBI (Glasgow Coma Scale score ≤8) who received conventional treatment (August 2007-July 2011) or treatment in the hybrid ER (August 2011-July 2015). The primary end point was unfavorable outcome at 6 months after injury (death, vegetative state, or lower severe disability) as evaluated by the Glasgow Outcome Scale-Extended. Secondary end points included time from arrival to the start of CT examination and emergency intracranial operation. Potential confounders were adjusted with multivariable logistic regressions.

RESULTS

Among 158 included patients, 88 were in the conventional group and 70 were in the hybrid ER group. After model adjustment, the hybrid ER group was significantly associated with a reduction in unfavorable outcomes. Times to CT examination and intracranial operation were significantly shorter in the hybrid ER group than that in the conventional group.

CONCLUSIONS

The hybrid ER system is useful for realizing immediate CT examination and emergency surgery and improving functional outcomes in patients with severe TBI.

Pressure reactivity index: journey through the past 20 years

Autoregulation after traumatic brain injury can be monitored continuously using simple signal processing of intracranial pressure and arterial blood pressure. The pressure reactivity index (PRx) showed several benefits when it was applied to continuous brain monitoring. Among them, a positive and strong correlation with the outcome and possibility of calculation of 'optimal cerebral perfusion pressure' have been listed. For this methodology, prospective clinical trials are missing-few of them are planned in the near future.