The accuracy of transcranial Doppler in excluding intracranial hypertension following acute brain injury: a multicenter prospective pilot study

Noninvasive Intracranial Pressure Monitoring: Are We There Yet?

There is an urgent unmet need for a reliable noninvasive tool to detect elevations in intracranial pressure (ICP) above guideline-recommended thresholds for treatment. Gold standard invasive ICP monitoring is unavailable in many settings, including resource-limited environments, and in situations such as liver failure in which coagulopathy increases the risk of invasive monitoring. Although a large number of noninvasive techniques have been evaluated, this article reviews the potential clinical role, if any, of the techniques that have undergone the most extensive evaluation and are already in clinical use. Elevations in ICP transmitted through the subarachnoid space result in distension of the optic nerve sheath. The optic nerve sheath diameter (ONSD) can be measured with ultrasound, and an ONSD threshold can be used to detect elevated ICP. Although many studies suggest this technique accurately detects elevated ICP, there is concern for risk of bias and variations in ONSD thresholds across studies that preclude routine use of this technique in clinical practice. Multiple transcranial Doppler techniques have been used to assess ICP, but the best studied are the pulsatility index and the Czosnyka method to estimate cerebral perfusion pressure and ICP. Although there is inconsistency in the literature, recent prospective studies, including an international multicenter study, suggest the estimated ICP technique has a high negative predictive value (> 95%) but a poor positive predictive value (≤ 30%). Quantitative pupillometry is a sensitive and objective method to assess pupillary size and reactivity. Proprietary indices have been developed to quantify the pupillary light response. Limited data suggest these quantitative measurements may be useful for the early detection of ICP elevation. No current noninvasive technology can replace invasive ICP monitoring. Where ICP monitoring is unavailable, multimodal noninvasive assessment may be useful. Further innovation and research are required to develop a reliable, continuous technique of noninvasive ICP assessment.

Carbon dioxide induced cerebral vasomotor reactivity in moderate-to-severe cerebral venous thrombosis patients and its impact on prognosis: A transcranial doppler-based prospective exploratory study

Hyperventilation-induced intracranial pressure reduction might be impaired in cerebral venous thrombosis (CVT) patients. Using transcranial Doppler, we assessed carbon dioxide-vasomotor reactivity (CO2-VMR) within 24 hours of admission in CVT patients and studied its correlation with patient outcomes. Adult moderate-severe CVT patients (participants of another large observational study) were included. CO2-VMR was calculated as the percentage change in peak flow velocities during maximal hypercapnia and hypocapnia. Outcome was assessed with the modified Rankin scale (mRS) at one - month post-discharge, dichotomized into favourable (mRS≤2) and unfavourable (mRS>2). Twenty patients' data was analysed. Impaired CO2-VMR (<70 %) was observed in 13 patients in the affected hemisphere; among them, 10 had impairments in both hemispheres. CO2-VMR correlated negatively with mRS (Rho = -0.688, p = 0.001). Odds for unfavourable outcomes were reduced by 92 % in patients with intact VMR on the ipsilateral hemisphere (Odds ratio (OR) 0.08, Confidence interval (CI) 0.006---0.636, p = 0.027) and by 94 % with VMR intact on the contralateral hemisphere (OR 0.063, CI 0.003---0.569, p = 0.03). Thus, impaired CO2-VMR in moderate to severe CVT patients is associated with unfavourable outcomes, and has the potential to prognosticate CVT patients objectively.

Analysis of phase shift between pulse oscillations of macro- and microvascular cerebral blood flow in patients with traumatic brain injury

PURPOSE

After a traumatic brain injury (TBI), monitoring of both macrovascular and microvascular blood circulation can potentially yield a better understanding of pathophysiology of potential secondary brain lesions. We investigated the changes in phase shift (PS) between cardiac-induced oscillations of cerebral blood flow (CBF) measured at macro (ultrasound Doppler) and microvascular (laser Doppler) level. Further we assessed the impact of intracranial pressure (ICP) on PS in TBI patients. A secondary aim was to compare PS to TCD-derived cerebral arterial time constant (τ), a parameter that reflects the circulatory transit time.

METHODS

TCD blood flow velocities (FV) in the middle cerebral artery, laser Doppler blood microcirculation flux (LDF), arterial blood pressure (ABP), and ICP were monitored in 29 consecutive patients with TBI. Eight patients were excluded because of poor-quality signals. For the remaining 21 patients (median age = 23 (Q1: 20-Q3: 33); men:16,) data were retrospectively analysed. PS between the fundamental harmonics of FV and LDF signals was determined using spectral analysis. τ was estimated as a product of cerebrovascular resistance and compliance, based on the mathematical transformation of FV and ABP, ICP pulse waveforms.

RESULTS

PS was negative (median: -26 (Q1: -38-Q3: -15) degrees) indicating that pulse LDF at a heart rate frequency lagged behind TCD pulse. With rising mean ICP, PS became more negative (R = -0.51, p < 0.019) indicating that delay of LDF pulse increases. There was a significant correlation between PS and cerebrovascular time constant (R = -0.47, p = 0.03).

CONCLUSIONS

Pulse divergence between FV and LDF became greater with elevated ICP, likely reflecting prolonged circulatory travel time.

A Narrative Review on Financial Challenges and Health Care Costs Associated with Traumatic Brain Injury in the United States

BACKGROUND

Traumatic brain injury (TBI) is a highly prevalent and potentially severe medical condition. Challenges regarding TBI management are related to accurate diagnostics, defining its severity, and establishing prompt interventions to affect outcomes. Among the health care components in the TBI handling strategy is intracranial pressure (ICP) monitoring, which is fundamental to therapy decisions. However, ICP monitoring is an Achilles tendon, imposing a significant financial burden on health care systems, particularly in middle and low-income communities. This article arises from the understanding from the authors that there is insufficient scientific evidence about the potential economic impacts from the use of noninvasive technologies in the monitoring of TBI. Based on personal experience, as well as from reading other, clinically focused studies, the thesis is that the use of such technologies could greatly affect the health care system and this article seeks to address this lack of literature, show ways in which such systems could be evaluated, and show estimations of possible results from these investigations.

OBJECTIVE

This review primarily investigates the economic burden of TBI and whether new technologies are suitable to reduce its health care costs without compromising the quality of care, according to the levels of evidence available. The objective is to stimulate more research and attention in the area.

METHODS

For this narrative review, a PubMed search was conducted for articles discussing TBI health care costs, as well as monitoring technologies (tomography, magnetic resonance imaging, optic nerve sheath diameter, transcranial Doppler, pupillometry, and noninvasive ICP waveform) and their application in managing TBI. Strategies were first evaluated from a medical noninferiority perspective before calculating the average savings of each selected strategy. All applicable studies were analyzed for quality using the Consolidated Health Economic Evaluation Reporting Standards 2022 Statement117 and this article was written to conform as much as possible with it.

RESULTS

The review included 109 references and showed a consistent potential in noninvasive technologies to reduce costs and maintain or improve the quality of care.

CONCLUSIONS

TBI prevalence has increased with a disproportionate health care burden in the last decades. Noninvasive monitoring techniques seem to be effective in reducing TBI health care costs, with few limitations, especially the need for more supporting scientific evidence. The undeniable clinical and financial potential of these techniques is compelling to further investigate their role in TBI management, as well as the creation of more comprehensive monitoring models to the understanding of complex phenomena occurring in the injured brain.

[Current Aspects of Intensive Medical Care for Traumatic Brain Injury - Part 1 - Primary Treatment Strategies, Haemodynamic Management and Multimodal Monitoring]

This two-part article deals with the intensive medical care of traumatic brain injury. Part 1 addresses the primary treatment strategy, haemodynamic management and multimodal monitoring, Part 2 secondary treatment strategies, long-term outcome, neuroprognostics and chronification. Traumatic brain injury is a complex clinical entity with a high mortality rate. The primary aim is to maintain homeostasis based on physiological targeted values. In addition, further therapy must be geared towards intracranial pressure. In addition to this, there are other monitoring options that appear sensible from a pathophysiological point of view with appropriate therapy adjustment. However, there is still a lack of data on their effectiveness. A further aspect is the inflammation of the cerebrum with the "cross-talk" of the organs, which has a significant influence on further intensive medical care.

Non-Invasive Methods for Intracranial Pressure Monitoring in Traumatic Brain Injury Using Transcranial Doppler: A Scoping Review

Intracranial pressure (ICP) monitoring is necessary for managing patients with traumatic brain injury (TBI). Although gold-standard methods include intraventricular or intraparenchymal transducers, these systems cannot be used in patients with coagulopathies or in those who are at high risk of catheter-related infections, nor can they be used in resource-constrained settings. Therefore, a non-invasive modality that is more widely available, cost effective, and safe would have tremendous impact. Among such non-invasive choices, transcranial Doppler (TCD) provides indirect ICP estimates through waveform analysis of cerebral hemodynamic changes. The objective of this scoping review is to describe the existing evidence for the use of TCD-derived methods in estimating ICP in adult TBI patients as compared with gold-standard invasive methods. This review was conducted in accordance with the Joanna Briggs Institute methodology for scoping reviews, with a main search of PubMed and Embase. The search was limited to studies conducted in adult TBI patients published in any language between 2012 and 2022. Twenty-two studies were included for analysis, with most being prospective studies conducted in high-income countries. TCD-derived non-invasive ICP (nICP) methods are either mathematical or non-mathematical, with the former having slightly better correlation with invasive methods, especially when using time-trending ICP dynamics over one-time estimated values. Nevertheless, mathematical methods are associated with greater cost and complexity in their application. Formula-based methods showed promise in excluding elevated ICP, exhibiting a high negative predictive value. Therefore, TCD-derived methods could be useful in assessing ICP changes instead of absolute ICP values for high-risk patients, especially in low-resource settings.

Estimated Cerebral Perfusion Pressure and Intracranial Pressure in Septic Patients

BACKGROUND

Sepsis-associated brain dysfunction (SABD) is frequent and is associated with poor outcome. Changes in brain hemodynamics remain poorly described in this setting. The aim of this study was to investigate the alterations of cerebral perfusion pressure and intracranial pressure in a cohort of septic patients.

METHODS

We conducted a retrospective analysis of prospectively collected data in septic adults admitted to our intensive care unit (ICU). We included patients in whom transcranial Doppler recording performed within 48 h from diagnosis of sepsis was available. Exclusion criteria were intracranial disease, known vascular stenosis, cardiac arrhythmias, pacemaker, mechanical cardiac support, severe hypotension, and severe hypocapnia or hypercapnia. SABD was clinically diagnosed by the attending physician, anytime during the ICU stay. Estimated cerebral perfusion pressure (eCPP) and estimated intracranial pressure (eICP) were calculated from the blood flow velocity of the middle cerebral artery and invasive arterial pressure using a previously validated formula. Normal eCPP was defined as eCPP ≥ 60 mm Hg, low eCPP was defined as eCPP < 60 mm Hg; normal eICP was defined as eICP ≤ 20 mm Hg, and high eICP was defined as eICP > 20 mm Hg.

RESULTS

A total of 132 patients were included in the final analysis (71% male, median [interquartile range (IQR)] age was 64 [52-71] years, median [IQR] Acute Physiology and Chronic Health Evaluation II score on admission was 21 [15-28]). Sixty-nine (49%) patients developed SABD during the ICU stay, and 38 (29%) were dead at hospital discharge. Transcranial Doppler recording lasted 9 (IQR 7-12) min. Median (IQR) eCPP was 63 (58-71) mm Hg in the cohort; 44 of 132 (33%) patients had low eCPP. Median (IQR) eICP was 8 (4-13) mm Hg; five (4%) patients had high eICP. SABD occurrence and in-hospital mortality did not differ between patients with normal eCPP and patients with low eCPP or between patients with normal eICP and patients with high eICP. Eighty-six (65%) patients had normal eCPP and normal eICP, 41 (31%) patients had low eCPP and normal eICP, three (2%) patients had low eCPP and high eICP, and two (2%) patients had normal eCPP and high eICP; however, SABD occurrence and in-hospital mortality were not significantly different among these subgroups.

CONCLUSIONS

Brain hemodynamics, in particular CPP, were altered in one third of critically ill septic patients at a steady state of monitoring performed early during the course of sepsis. However, these alterations were equally common in patients who developed or did not develop SABD during the ICU stay and in patients with favorable or unfavorable outcome.

Transcranial sonography in the critical patient

Transcranial ultrasonography is a non-invasive, bedside technique that has become a widely implemented tool in the evaluation and management of neurocritically ill patients. It constitutes a technique in continuous growth whose fundamentals (and limitations) must be known by the intensivist. This review provides a practical approach for the intensivist, including the different sonographic windows and planes of insonation and its role in different conditions of the neurocritical patients and in critical care patients of other etiologies.

Feasibility of Prone Positioning for Brain-injured Patients with Severe Acute Respiratory Distress Syndrome: A Systematic Review and Pilot Study (ProBrain)

BACKGROUND

Prone position is a key component to treat hypoxemia in patients with severe acute respiratory distress syndrome. However, most studies evaluating it exclude patients with brain injuries without any medical evidence.

METHODS

This study includes a systematic review to determine whether brain-injured patients were excluded in studies evaluating prone position on acute respiratory distress syndrome; a prospective study including consecutive brain-injured patients needing prone position. The primary endpoint was the evaluation of cerebral blood flow using transcranial Doppler after prone positioning. Secondary outcomes were intracranial pressure, cerebral perfusion pressure, and tissue oxygen pressure.

RESULTS

From 8,183 citations retrieved, 120 studies were included in the systematic review. Among them, 90 studies excluded brain-injured patients (75%) without any justification, 16 included brain-injured patients (4 randomized, 7 nonrandomized studies, 5 retrospective), and 14 did not retrieve brain-injured data. Eleven patients were included in the authors' pilot study. No reduction of cerebral blood flow surrogates was observed during prone positioning, with diastolic speed values (mean ± SD) ranging from 37.7 ± 16.2 cm/s to 45.2 ± 19.3 cm/s for the right side (P = 0.897) and 39.6 ± 18.2 cm/s to 46.5 ± 21.3 cm/s for the left side (P = 0.569), and pulsatility index ranging from 1.14 ± 0.31 to 1.0 ± 0.32 for the right side (P = 0.145) and 1.14 ± 0.31 to 1.02 ± 0.2 for the left side (P = 0.564) before and during prone position.

CONCLUSIONS

Brain-injured patients are largely excluded from studies evaluating prone position in acute respiratory distress syndrome. However, cerebral blood flow seems not to be altered considering increasing of mean arterial pressure during the session. Systematic exclusion of brain-injured patients appears to be unfounded, and prone position, while at risk in brain-injured patients, should be evaluated on these patients to review recommendations, considering close monitoring of neurologic and hemodynamic parameters.

EDITOR’S PERSPECTIVE

A pilot clinical study to estimate intracranial pressure utilising cerebral photoplethysmograms in traumatic brain injury patients

PURPOSE

In this research, a non-invasive intracranial pressure (nICP) optical sensor was developed and evaluated in a clinical pilot study. The technology relied on infrared light to probe brain tissue, using photodetectors to capture backscattered light modulated by vascular pulsations within the brain's vascular tissue. The underlying hypothesis was that changes in extramural arterial pressure could affect the morphology of recorded optical signals (photoplethysmograms, or PPGs), and analysing these signals with a custom algorithm could enable the non-invasive calculation of intracranial pressure (nICP).

METHODS

This pilot study was the first to evaluate the nICP probe alongside invasive ICP monitoring as a gold standard. nICP monitoring occurred in 40 patients undergoing invasive ICP monitoring, with data randomly split for machine learning. Quality PPG signals were extracted and analysed for time-based features. The study employed Bland-Altman analysis and ROC curve calculations to assess nICP accuracy compared to invasive ICP data.

RESULTS

Successful acquisition of cerebral PPG signals from traumatic brain injury (TBI) patients allowed for the development of a bagging tree model to estimate nICP non-invasively. The nICP estimation exhibited 95% limits of agreement of 3.8 mmHg with minimal bias and a correlation of 0.8254 with invasive ICP monitoring. ROC curve analysis showed strong diagnostic capability with 80% sensitivity and 89% specificity.

CONCLUSION

The clinical evaluation of this innovative optical nICP sensor revealed its ability to estimate ICP non-invasively with acceptable and clinically useful accuracy. This breakthrough opens the door to further technological refinement and larger-scale clinical studies in the future.

TRIAL REGISTRATION

NCT05632302, 11th November 2022, retrospectively registered.

Investigating the effects of tilting the postural drainage lithotripsy system on cerebral blood flow, intracranial pressure, heart rate, and blood pressure

PURPOSE

To investigate the effect of the postural drainage lithotripsy system developed by our experimental team on the vital signs of patient with urinary stones during the stone removal process.

METHODS

Four groups of 15 subjects (0°, 10°, 40°, and 70°) were subjected to different angles of head-down tilt to measure middle cerebral artery blood flow velocity (MCAv), cerebrovascular conductance coefficient (CVCi), intracranial pressure (nICP), heart rate (HR), and mean arterial blood pressure (MAP).

RESULTS

As the angle of HDT changed, MCAv values, nICP values, CVCi values, HR values, and MAP values changed significantly (all P ≤ 0.001), and the difference was statistically significant. During 10°HDT, despite a slight increase in nICP, the other measurements remained stable. During 40°HDT, only the MCAv values did not change significantly, whereas the rest of the measures were significantly altered. During 70°HDT, all indicators changed significantly.

CONCLUSIONS

The significant alterations in cerebral blood flow, intracranial pressure, and hemodynamics induced during the treatment of renal residual fragments with postural drainage should be used with caution in individuals with cerebrovascular accidents.

CHINA CLINICAL TRIALS REGISTRY

ChiCTR2300070671; Registration date: 2023-04-18.

Astrocytoma Mimicking Herpetic Meningoencephalitis: The Role of Non-Invasive Multimodal Monitoring in Neurointensivism

Neuromonitoring is a critical tool for emergency rooms and intensive care units to promptly identify and treat brain injuries. The case report of a patient with status epilepticus necessitating orotracheal intubation and intravenous lorazepam administration is presented. A pattern of epileptiform activity was detected in the left temporal region, and intravenous Acyclovir was administered based on the diagnostic hypothesis of herpetic meningoencephalitis. The neurointensivist opted for multimodal non-invasive bedside neuromonitoring due to the complexity of the patient's condition. A Brain4care (B4C) non-invasive intracranial compliance monitor was utilized alongside the assessment of an optic nerve sheath diameter (ONSD) and transcranial Doppler (TCD). Based on the collected data, a diagnosis of intracranial hypertension (ICH) was made and a treatment plan was developed. After the neurosurgery team's evaluation, a stereotaxic biopsy of the temporal lesion revealed a grade 2 diffuse astrocytoma, and an urgent total resection was performed. Research suggests that monitoring patients in a dedicated neurologic intensive care unit (Neuro ICU) can lead to improved outcomes and shorter hospital stays. In addition to being useful for patients with a primary brain injury, neuromonitoring may also be advantageous for those at risk of cerebral hemodynamic impairment. Lastly, it is essential to note that neuromonitoring technologies are non-invasive, less expensive, safe, and bedside-accessible approaches with significant diagnostic and monitoring potential for patients at risk of brain abnormalities. Multimodal neuromonitoring is a vital tool in critical care units for the identification and management of acute brain trauma as well as for patients at risk of cerebral hemodynamic impairment.

Multimodal monitoring intracranial pressure by invasive and noninvasive means

Although the placement of an intraventricular catheter remains the gold standard method for the diagnosis of intracranial hypertension (ICH), the technique has several limitations including but not limited to its invasiveness. Current noninvasive methods, however, still lack robust evidence to support their clinical use. We aimed to estimate, as an exploratory hypothesis generating analysis, the discriminative power of four noninvasive methods to diagnose ICH. We prospectively collected data from adult intensive care unit (ICU) patients with subarachnoid hemorrhage (SAH), intraparenchymal hemorrhage (IPH), and ischemic stroke (IS) in whom invasive intracranial pressure (ICP) monitoring had been placed. Measures were simultaneously collected from the following noninvasive methods: optic nerve sheath diameter (ONSD), pulsatility index (PI) using transcranial Doppler (TCD), a 5-point visual scale designed for brain Computed Tomography (CT), and two parameters (time-to-peak [TTP] and P2/P1 ratio) of a noninvasive ICP wave morphology monitor (Brain4Care[B4c]). ICH was defined as a sustained ICP > 20 mmHg for at least 5 min. We studied 18 patients (SAH = 14; ICH = 3; IS = 1) on 60 occasions with a mean age of 52 ± 14.3 years. All methods were recorded simultaneously, except for the CT, which was performed within 24 h of the other methods. The median ICP was 13 [9.8-16.2] mmHg, and intracranial hypertension was present on 18 occasions (30%). Median values from the noninvasive techniques were ONSD 4.9 [4.40-5.41] mm, PI 1.22 [1.04-1.43], CT scale 3 points [IQR: 3.0], P2/P1 ratio 1.16 [1.09-1.23], and TTP 0.215 [0.193-0.237]. There was a significant statistical correlation between all the noninvasive techniques and invasive ICP (ONSD, r = 0.29; PI, r = 0.62; CT, r = 0.21; P2/P1 ratio, r = 0.35; TTP, r = 0.35, p < 0.001 for all comparisons). The area under the curve (AUC) to estimate intracranial hypertension was 0.69 [CIs = 0.62-0.78] for the ONSD, 0.75 [95% CIs 0.69-0.83] for the PI, 0.64 [95%Cis 0.59-069] for CT, 0.79 [95% CIs 0.72-0.93] for P2/P1 ratio, and 0.69 [95% CIs 0.60-0.74] for TTP. When the various techniques were combined, an AUC of 0.86 [0.76-0.93]) was obtained. The best pair of methods was the TCD and B4cth an AUC of 0.80 (0.72-0.88). Noninvasive technique measurements correlate with ICP and have an acceptable discrimination ability in diagnosing ICH. The multimodal combination of PI (TCD) and wave morphology monitor may improve the ability of the noninvasive methods to diagnose ICH. The observed variability in non-invasive ICP estimations underscores the need for comprehensive investigations to elucidate the optimal method-application alignment across distinct clinical scenarios.

Transcranial Color-Coded Sonography With Angle Correction As a Screening Tool for Raised Intracranial Pressure

OBJECTIVES

Transcranial Doppler (TCD) has been evaluated as a noninvasive intracranial pressure (ICP) assessment tool. Correction for insonation angle, a potential source of error, with transcranial color-coded sonography (TCCS) has not previously been reported while evaluating ICP with TCD. Our objective was to study the accuracy of TCCS for detection of ICP elevation, with and without the use of angle correction.

DESIGN

Prospective study of diagnostic accuracy.

SETTING

Academic neurocritical care unit.

PATIENTS

Consecutive adults with invasive ICP monitors.

INTERVENTIONS

Ultrasound assessment with TCCS.

MEASUREMENTS AND MAIN RESULTS

End-diastolic velocity (EDV), time-averaged peak velocity (TAPV), and pulsatility index (PI) were measured in the bilateral middle cerebral arteries with and without angle correction. Concomitant mean arterial pressure (MAP) and ICP were recorded. Estimated cerebral perfusion pressure (CPP) was calculated as estimated CPP (CPPe) = MAP × (EDV/TAPV) + 14, and estimated ICP (ICPe) = MAP-CPPe. Sixty patients were enrolled and 55 underwent TCCS. Receiver operating characteristic curve analysis of ICPe for detection of invasive ICP greater than 22 mm Hg revealed area under the curve (AUC) 0.51 (0.37-0.64) without angle correction and 0.73 (0.58-0.84) with angle correction. The optimal threshold without angle correction was ICPe greater than 18 mm Hg with sensitivity 71% (29-96%) and specificity 28% (16-43%). With angle correction, the optimal threshold was ICPe greater than 21 mm Hg with sensitivity 100% (54-100%) and specificity 30% (17-46%). The AUC for PI was 0.61 (0.47-0.74) without angle correction and 0.70 (0.55-0.92) with angle correction.

CONCLUSIONS

Angle correction improved the accuracy of TCCS for detection of elevated ICP. Sensitivity was high, as appropriate for a screening tool, but specificity remained low.

The use of noninvasive measurements of intracranial pressure in patients with traumatic brain injury: a narrative review

BACKGROUND

 The most frequent cause of death in neurosurgical patients is due to the increase in intracranial pressure (ICP); consequently, adequate monitoring of this parameter is extremely important.

OBJECTIVES

 In this study, we aimed to analyze the accuracy of noninvasive measurement methods for intracranial hypertension (IH) in patients with traumatic brain injury (TBI).

METHODS

 The data were obtained from the PubMed database, using the following terms: intracranial pressure, noninvasive, monitoring, assessment, and measurement. The selected articles date from 1980 to 2021, all of which were observational studies or clinical trials, in English and specifying ICP measurement in TBI. At the end of the selection, 21 articles were included in this review.

RESULTS

 The optic nerve sheath diameter (ONSD), pupillometry, transcranial doppler (TCD), multimodal combination, brain compliance using ICP waveform (ICPW), HeadSense, and Visual flash evoked pressure (FVEP) were analyzed. Pupillometry was not found to correlate with ICP, while HeadSense monitor and the FVEP method appear to have good correlation, but sensitivity and specificity data are not available. The ONSD and TCD methods showed good-to-moderate accuracy on invasive ICP values and potential to detect IH in most studies. Furthermore, multimodal combination may reduce the error possibility related to each technique. Finally, ICPW showed good accuracy to ICP values, but this analysis included TBI and non-TBI patients in the same sample.

CONCLUSIONS

 Noninvasive ICP monitoring methods may be used in the near future to guide TBI patients' management.

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.

The importance of monitoring cerebral oxygenation in non brain injured patients

Over the past few years, the use of non-invasive neuromonitoring in non-brain injured patients has increased, as a result of the recognition that many of these patients are at risk of brain injury in a wide number of clinical scenarios and therefore may benefit from its application which allows interventions to prevent injury and improve outcome. Among these, are post cardiac arrest syndrome, sepsis, liver failure, acute respiratory failure, and the perioperative settings where in the absence of a primary brain injury, certain groups of patients have high risk of neurological complications. While there are many neuromonitoring modalities utilized in brain injured patients, the majority of those are either invasive such as intracranial pressure monitoring, require special skill such as transcranial Doppler ultrasonography, or intermittent such as pupillometry and therefore unable to provide continuous monitoring. Cerebral oximetry using Near infrared Spectroscopy, is a simple non invasive continuous measure of cerebral oxygenation that has been shown to be useful in preventing cerebral hypoxemia both within the intensive care unit and the perioperative settings. At present, current recommendations for standard monitoring during anesthesia or in the general intensive care concentrate mainly on hemodynamic and respiratory monitoring without specific indications regarding the brain, and in particular, brain oximetry. The aim of this manuscript is to provide an up-to-date overview of the pathophysiology and applications of cerebral oxygenation in non brain injured patients as part of non-invasive multimodal neuromonitoring in the early identification and treatment of neurological complications in this population.

Systemic and Cerebral Effects of Physiotherapy in Mechanically Ventilated Subjects

BACKGROUND

Physiotherapy may result in better functional outcomes, shorter duration of delirium, and more ventilator-free days. The effects of physiotherapy on different subpopulations of mechanically ventilated patients on respiratory and cerebral function are still unclear. We evaluated the effect of physiotherapy on systemic gas exchange and hemodynamics as well as on cerebral oxygenation and hemodynamics in mechanically ventilated subjects with and without COVID-19 pneumonia.

METHODS

This was an observational study in critically ill subjects with and without COVID-19 who underwent protocolized physiotherapy (including respiratory and rehabilitation physiotherapy) and neuromonitoring of cerebral oxygenation and hemodynamics. PaO2 /FIO2 , PaCO2 , hemodynamics (mean arterial pressure [MAP], mm Hg; heart rate, beats/min), and cerebral physiologic parameters (noninvasive intracranial pressure, cerebral perfusion pressure using transcranial Doppler, and cerebral oxygenation using near-infrared spectroscopy) were assessed before (T0) and immediately after physiotherapy (T1).

RESULTS

Thirty-one subjects were included (16 with COVID-19 and 15 without COVID-19). Physiotherapy improved PaO2 /FIO2 in the overall population (T1 = 185 [108-259] mm Hg vs T0 = 160 [97-231] mm Hg, P = .02) and in the subjects with COVID-19 (T1 = 119 [89-161] mm Hg vs T0 = 110 [81-154] mm Hg, P = .02) and decreased the PaCO2 in the COVID-19 group only (T1 = 40 [38-44] mm Hg vs T0 = 43 [38-47] mm Hg, P = .03). Physiotherapy did not affect cerebral hemodynamics, whereas increased the arterial oxygen part of hemoglobin both in the overall population (T1 = 3.1% [-1.3 to 4.9] vs T0 = 1.1% [-1.8 to 2.6], P = .007) and in the non-COVID-19 group (T1 = 3.7% [0.5-6.3] vs T0 = 0% [-2.2 to 2.8], P = .02). Heart rate was higher after physiotherapy in the overall population (T1 = 87 [75-96] beats/min vs T0 = 78 [72-92] beats/min, P = .044) and in the COVID-19 group (T1 = 87 [81-98] beats/min vs T0 = 77 [72-91] beats/min, P = .01), whereas MAP increased in the COVID-19 group only (T1 = 87 [82-83] vs T0 = 83 [76-89], P = .030).

CONCLUSIONS

Protocolized physiotherapy improved gas exchange in subjects with COVID-19, whereas it improved cerebral oxygenation in non-COVID-19 subjects.

Brain monitoring after cardiac arrest

PURPOSE OF REVIEW

To describe the available neuromonitoring tools in patients who are comatose after resuscitation from cardiac arrest because of hypoxic-ischemic brain injury (HIBI).

RECENT FINDINGS

Electroencephalogram (EEG) is useful for detecting seizures and guiding antiepileptic treatment. Moreover, specific EEG patterns accurately identify patients with irreversible HIBI. Cerebral blood flow (CBF) decreases in HIBI, and a greater decrease with no CBF recovery indicates poor outcome. The CBF autoregulation curve is narrowed and right-shifted in some HIBI patients, most of whom have poor outcome. Parameters derived from near-infrared spectroscopy (NIRS), intracranial pressure (ICP) and transcranial Doppler (TCD), together with brain tissue oxygenation, are under investigation as tools to optimize CBF in patients with HIBI and altered autoregulation. Blood levels of brain biomarkers and their trend over time are used to assess the severity of HIBI in both the research and clinical setting, and to predict the outcome of postcardiac arrest coma. Neuron-specific enolase (NSE) is recommended as a prognostic tool for HIBI in the current postresuscitation guidelines, but other potentially more accurate biomarkers, such as neurofilament light chain (NfL) are under investigation.

SUMMARY

Neuromonitoring provides essential information to detect complications, individualize treatment and predict prognosis in patients with HIBI.

POCUS, how can we include the brain? An overview

Point-of-care ultrasound (POCUS) is an essential tool to assess and manage different pathologies in the intensive care unit, and many protocols have been proposed for its application in critical care literature. However, the brain has been overlooked in these protocols.

Brain ultrasonography (BU) is easily available, and it allows a goal-directed approach thanks to its repeatability and immediate interpretation and provides a quick management and real time assessment of patients’ conditions. Based on recent studies, the increasing interest from intensivists, and the undeniable benefits of ultrasound, the main goal of this overview is to describe the main evidence and progresses in the incorporation of BU into the POCUS approach in the daily practice, and thus becoming POCUS-BU. This integration would allow a noninvasive global assessment to entail an integrated analysis of the critical care patients.

Intracranial pressure: current perspectives on physiology and monitoring

Intracranial pressure (ICP) monitoring is now viewed as integral to the clinical care of many life-threatening brain insults, such as severe traumatic brain injury, subarachnoid hemorrhage, and malignant stroke. It serves to warn of expanding intracranial mass lesions, to prevent or treat herniation events as well as pressure elevation which impedes nutrient delivery to the brain. It facilitates the calculation of cerebral perfusion pressure (CPP) and the estimation of cerebrovascular autoregulatory status. Despite advancements in our knowledge emanating from a half century of experience with this technology, important controversies remain related even to fundamental aspects of ICP measurements, including indications for monitoring, ICP treatment thresholds, and management of intracranial hypertension. Here, we review the history of ICP monitoring, the underlying pathophysiology as well as current perspectives on why, when and how ICP monitoring is best used. ICP is typically assessed invasively but a number of emerging, non-invasive technologies with inherently lower risk are showing promise. In selected cases, additional neuromonitoring can be used to assist in the interpretation of ICP monitoring information and adapt directed treatment accordingly. Additional efforts to expand the evidence base relevant to ICP monitoring, related technologies and management remain a high priority in neurosurgery and neurocritical care.

The Next Frontier in Neurocritical Care in Resource-Constrained Settings

Neurocritical care (NCC) is an emerging field within critical care medicine, reflecting the widespread prevalence of neurologic injury in critically ill patients. Morbidity and mortality from neurocritical illness (NCI) have been reduced substantially in resource-rich settings (RRS), owing to the development of advanced technologies, neuro-specific units, and subspecialized medical training. Despite shouldering much of the burden of NCI worldwide, resource-limited settings (RLS) face immense hurdles when implementing guidelines generated in RRS. This review summarizes the current epidemiology, management, and outcomes of the most common NCIs in RLS and offers commentary on future directions in NCC practiced in RLS.

Anatomy imaging and hemodynamics research on the cerebral vein and venous sinus among individuals without cranial sinus and jugular vein diseases

In recent years, imaging technology has allowed the visualization of intracranial and extracranial vascular systems. However, compared with the cerebral arterial system, the relative lack of image information, individual differences in the anatomy of the cerebral veins and venous sinuses, and several unique structures often cause neurologists and radiologists to miss or over-diagnose. This increases the difficulty of the clinical diagnosis and treatment of cerebral venous system diseases. This review focuses on applying different imaging methods to the normal anatomical morphology of the cerebral venous system and special structural and physiological parameters, such as hemodynamics, in people without cranial sinus and jugular vein diseases and explores its clinical significance. We hope this study will reinforce the importance of studying the cerebral venous system anatomy and imaging data and will help diagnose and treat systemic diseases.

Initial neurocritical care of severe traumatic brain injury: New paradigms and old challenges

Background:

Early neurocritical care aims to ameliorate secondary traumatic brain injury (TBI) and improve neural salvage. Increased engagement of neurosurgeons in neurocritical care is warranted as daily briefings between the intensivist and the neurosurgeon are considered a quality indicator for TBI care. Hence, neurosurgeons should be aware of the latest evidence in the neurocritical care of severe TBI (sTBI).

Methods:

We conducted a narrative literature review of bibliographic databases (PubMed and Scopus) to examine recent research of sTBI.

Results:

This review has several take-away messages. The concept of critical neuroworsening and its possible causes is discussed. Static thresholds of intracranial pressure (ICP) and cerebral perfusion pressure may not be optimal for all patients. The use of dynamic cerebrovascular reactivity indices such as the pressure reactivity index can facilitate individualized treatment decisions. The use of ICP monitoring to tailor treatment of intracranial hypertension (IHT) is not routinely feasible. Different guidelines have been formulated for different scenarios. Accordingly, we propose an integrated algorithm for ICP management in sTBI patients in different resource settings. Although hyperosmolar therapy and decompressive craniectomy are standard treatments for IHT, there is a lack high-quality evidence on how to use them. A discussion of the advantages and disadvantages of invasive ICP monitoring is included in the study. Addition of beta-blocker, anti-seizure, and anticoagulant medications to standardized management protocols (SMPs) should be considered with careful patient selection.

Conclusion:

Despite consolidated research efforts in the refinement of SMPs, there are still many unanswered questions and novel research opportunities for sTBI care.

Noninvasive ultrasonic induction of cerebrospinal fluid flow enhances intrathecal drug delivery

Intrathecal drug delivery is routinely used in the treatment and prophylaxis of varied central nervous system conditions, as doing so allows drugs to directly bypass the blood-brain barrier. However, the utility of this route of administration is limited by poor brain and spinal cord parenchymal drug uptake from the cerebrospinal fluid. We demonstrate that a simple noninvasive transcranial ultrasound protocol can significantly increase influx of cerebrospinal fluid into the perivascular spaces of the brain, to enhance the uptake of intrathecally administered drugs. Specifically, we administered small (~1 kDa) and large (~155 kDa) molecule agents into the cisterna magna of rats and then applied low, diagnostic-intensity focused ultrasound in a scanning protocol throughout the brain. Using real-time magnetic resonance imaging and ex vivo histologic analyses, we observed significantly increased uptake of small molecule agents into the brain parenchyma, and of both small and large molecule agents into the perivascular space from the cerebrospinal fluid. Notably, there was no evidence of brain parenchymal damage following this intervention. The low intensity and noninvasive approach of transcranial ultrasound in this protocol underscores the ready path to clinical translation of this technique. In this manner, this protocol can be used to directly bypass the blood-brain barrier for whole-brain delivery of a variety of agents. Additionally, this technique can potentially be used as a means to probe the causal role of the glymphatic system in the variety of disease and physiologic processes to which it has been correlated.

Management of moderate to severe traumatic brain injury: an update for the intensivist

Traumatic brain injury (TBI) remains one of the most fatal and debilitating conditions in the world. Current clinical management in severe TBI patients is mainly concerned with reducing secondary insults and optimizing the balance between substrate delivery and consumption. Over the past decades, multimodality monitoring has become more widely available, and clinical management protocols have been published that recommend potential interventions to correct pathophysiological derangements. Even while evidence from randomized clinical trials is still lacking for many of the recommended interventions, these protocols and algorithms can be useful to define a clear standard of therapy where novel interventions can be added or be compared to. Over the past decade, more attention has been paid to holistic management, in which hemodynamic, respiratory, inflammatory or coagulation disturbances are detected and treated accordingly. Considerable variability with regards to the trajectories of recovery exists. Even while most of the recovery occurs in the first months after TBI, substantial changes may still occur in a later phase. Neuroprognostication is challenging in these patients, where a risk of self-fulfilling prophecies is a matter of concern. The present article provides a comprehensive and practical review of the current best practice in clinical management and long-term outcomes of moderate to severe TBI in adult patients admitted to the intensive care unit.

Transcranial Doppler as a screening test to exclude intracranial hypertension in brain-injured patients: the IMPRESSIT-2 prospective multicenter international study

Background

Alternative noninvasive methods capable of excluding intracranial hypertension through use of transcranial Doppler (ICPtcd) in situations where invasive methods cannot be used or are not available would be useful during the management of acutely brain-injured patients. The objective of this study was to determine whether ICPtcd can be considered a reliable screening test compared to the reference standard method, invasive ICP monitoring (ICPi), in excluding the presence of intracranial hypertension.

Methods

This was a prospective, international, multicenter, unblinded, diagnostic accuracy study comparing the index test (ICPtcd) with a reference standard (ICPi), defined as the best available method for establishing the presence or absence of the condition of interest (i.e., intracranial hypertension). Acute brain-injured patients pertaining to one of four categories: traumatic brain injury (TBI), subarachnoid hemorrhage (SAH), intracerebral hemorrhage (ICH) or ischemic stroke (IS) requiring ICPi monitoring, were enrolled in 16 international intensive care units. ICPi measurements (reference test) were compared to simultaneous ICPtcd measurements (index test) at three different timepoints: before, immediately after and 2 to 3 h following ICPi catheter insertion. Sensitivity, specificity, positive (PPV) and negative predictive values (NPV) were calculated at three different ICPi thresholds (> 20, > 22 and > 25 mmHg) to assess ICPtcd as a bedside real-practice screening method. A receiver operating characteristic (ROC) curve analysis with the area under the curve (AUC) was used to evaluate the discriminative accuracy and predictive capability of ICPtcd.

Results

Two hundred and sixty-two patients were recruited for final analysis. Intracranial hypertension (> 22 mmHg) occurred in 87 patients (33.2%). The total number of paired comparisons between ICPtcd and ICPi was 687. The NPV was elevated (ICP > 20 mmHg = 91.3%, > 22 mmHg = 95.6%, > 25 mmHg = 98.6%), indicating high discriminant accuracy of ICPtcd in excluding intracranial hypertension. Concordance correlation between ICPtcd and ICPi was 33.3% (95% CI 25.6–40.5%), and Bland–Altman showed a mean bias of -3.3 mmHg. The optimal ICPtcd threshold for ruling out intracranial hypertension was 20.5 mmHg, corresponding to a sensitivity of 70% (95% CI 40.7–92.6%) and a specificity of 72% (95% CI 51.9–94.0%) with an AUC of 76% (95% CI 65.6–85.5%).

Conclusions and relevance

ICPtcd has a high NPV in ruling out intracranial hypertension and may be useful to clinicians in situations where invasive methods cannot be used or not available.

Trial registration: NCT02322970.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-03978-2.

Prolonged Automated Robotic TCD Monitoring in Acute Severe TBI: Study Design and Rationale

BACKGROUND

Transcranial Doppler ultrasonography (TCD) is a portable, bedside, noninvasive diagnostic tool used for the real-time assessment of cerebral hemodynamics. Despite the evident utility of TCD and the ability of this technique to function as a stethoscope to the brain, its use has been limited to specialized centers because of the dearth of technical and clinical expertise required to acquire and interpret the cerebrovascular parameters. Additionally, the conventional pragmatic episodic TCD monitoring protocols lack dynamic real-time feedback to guide time-critical clinical interventions. Fortunately, with the recent advent of automated robotic TCD technology in conjunction with the automated software for TCD data processing, we now have the technology to automatically acquire TCD data and obtain clinically relevant information in real-time. By obviating the need for highly trained clinical personnel, this technology shows great promise toward a future of widespread noninvasive monitoring to guide clinical care in patients with acute brain injury.

METHODS

Here, we describe a proposal for a prospective observational multicenter clinical trial to evaluate the safety and feasibility of prolonged automated robotic TCD monitoring in patients with severe acute traumatic brain injury (TBI). We will enroll patients with severe non-penetrating TBI with concomitant invasive multimodal monitoring including, intracranial pressure, brain tissue oxygenation, and brain temperature monitoring as part of standard of care in centers with varying degrees of TCD availability and experience. Additionally, we propose to evaluate the correlation of pertinent TCD-based cerebral autoregulation indices such as the critical closing pressure, and the pressure reactivity index with the brain tissue oxygenation values obtained invasively.

CONCLUSIONS

The overarching goal of this study is to establish safety and feasibility of prolonged automated TCD monitoring for patients with TBI in the intensive care unit and identify clinically meaningful and pragmatic noninvasive targets for future interventions.

Immune effector cell-associated neurotoxicity syndrome: A therapeutic approach in the critically ill

Immunotherapy with chimeric antigen-specific receptor modified T cells, known as CAR-T, is emerging as a promising approach to hematological malignancies. In this regard, CAR-T against human cluster of differentiation (CD) 19 has demonstrated antitumor efficacy in application to B cell neoplasms resistant to conventional therapy. However, activation of the immune system induces severe and specific complications which can prove life-threatening. These include cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome (known as ICANS) - the latter being the subject of the present review. Although the physiopathological mechanisms underlying ICANS are not well known, a number of clinical and biological factors increase the risk of developing neurotoxicity associated to CAR-T therapy. Treatment is based on close monitoring, measures of support, anticonvulsivants, corticosteroids, and early admission to intensive care. The present study offers a comprehensive review of the available literature from a multidisciplinary perspective, including recommendations from intensivists, neurologists and hematologists dedicated to the care of critically ill adults.

The Importance of Neuromonitoring in Non Brain Injured Patients

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2022. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2022. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from https://link.springer.com/bookseries/8901.

A noninvasive and comprehensive method for continuous assessment of cerebral blood flow pulsation based on magnetic induction phase shift

Cerebral blood flow (CBF) monitoring is of great significance for treating and preventing strokes. However, there has not been a fully accepted method targeting continuous assessment in clinical practice. In this work, we built a noninvasive continuous assessment system for cerebral blood flow pulsation (CBFP) that is based on magnetic induction phase shift (MIPS) technology and designed a physical model of the middle cerebral artery (MCA). Physical experiments were carried out through different simulations of CBF states. Four healthy volunteers were enrolled to perform the MIPS and ECG synchronously monitoring trials. Then, the components of MIPS related to the blood supply level and CBFP were investigated by signal analysis in time and frequency domain, wavelet decomposition and band-pass filtering. The results show that the time-domain baseline of MIPS increases with blood supply level. A pulse signal was identified in the spectrum (0.2-2 Hz in 200-2,000 ml/h groups, respectively) of MIPS when the simulated blood flow rate was not zero. The pulsation frequency with different simulated blood flow rates is the same as the squeezing frequency of the feeding pump. Similar to pulse waves, the MIPS signals on four healthy volunteers all had periodic change trends with obvious peaks and valleys. Its frequency is close to that of the ECG signal and there is a certain time delay between them. These results indicate that the CBFP component can effectively be extracted from MIPS, through which different blood supply levels can be distinguished. This method has the potential to become a new solution for non-invasive and comprehensive monitoring of CBFP.

Ten Good Reasons to Practice Neuroultrasound in Critical Care Setting

In the beginning, cerebral ultrasound (US) was not considered feasible because the intact skull was a seemingly impenetrable obstacle. For this reason, obtaining a clear image resolution had been a challenge since the first use of neuroultrasound (NUS) for the assessment of small deep brain structures. However, the improvements in transducer technologies and advances in signal processing have refined the image resolution, and the role of NUS has evolved as an imaging modality for the brain parenchyma within multiple pathologies. This article summarizes ten crucial applications of cerebral ultrasonography for the evaluation and management of neurocritical patients, whose transfer from and to intensive care units poses a real problem to medical care staff. This also encompasses ease of use, low cost, wide acceptance by patients, no radiation risk, and relative independence from movement artifacts. Bedsides, availability and reliability raised the interest of critical care intensivists in using it with increasing frequency. In this mini-review, the usefulness and the advantages of US in the neurocritical care setting are discussed regarding ten aspects to encourage the intensivist physician to practice this important tool.

Effects of positive end-expiratory pressure on lung ultrasound patterns and their correlation with intracranial pressure in mechanically ventilated brain injured patients

Background

The effects of positive end-expiratory pressure (PEEP) on lung ultrasound (LUS) patterns, and their relationship with intracranial pressure (ICP) in brain injured patients have not been completely clarified. The primary aim of this study was to assess the effect of two levels of PEEP (5 and 15 cmH₂O) on global (LUStot) and regional (anterior, lateral, and posterior areas) LUS scores and their correlation with changes of invasive ICP. Secondary aims included: the evaluation of the effect of PEEP on respiratory mechanics, arterial partial pressure of carbon dioxide (PaCO₂) and hemodynamics; the correlation between changes in ICP and LUS as well as respiratory parameters; the identification of factors at baseline as potential predictors of ICP response to higher PEEP.

Methods

Prospective, observational study including adult mechanically ventilated patients with acute brain injury requiring invasive ICP. Total and regional LUS scores, ICP, respiratory mechanics, and arterial blood gases values were analyzed at PEEP 5 and 15 cmH₂O.

Results

Thirty patients were included; 19 of them (63.3%) were male, with median age of 65 years [interquartile range (IQR) = 66.7–76.0]. PEEP from 5 to 15 cmH₂O reduced LUS score in the posterior regions (LUSp, median value from 7 [5–8] to 4.5 [3.7–6], p = 0.002). Changes in ICP were significantly correlated with changes in LUStot (rho = 0.631, p = 0.0002), LUSp (rho = 0.663, p < 0.0001), respiratory system compliance (rho = − 0.599, p < 0.0001), mean arterial pressure (rho = − 0.833, p < 0.0001) and PaCO₂ (rho = 0.819, p < 0.0001). Baseline LUStot score predicted the increase of ICP with PEEP.

Conclusions

LUS-together with the evaluation of respiratory and clinical variables-can assist the clinicians in the bedside assessment and prediction of the effect of PEEP on ICP in patients with acute brain injury.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-03903-7.

Neuromonitoreo no invasivo en unidades de cuidados intensivos en Colombia

El monitoreo electroencefalográfico no invasivo continuo es una técnica indispensable en los pacientes neurológicos críticos, ya que muestra de forma directa e indirecta su actividad cerebral y permite relacionar los hallazgos con su estado clínico. Es muy sensible, aunque su especificidad es menor, por lo que puede demostrar la alteración del estado de conciencia sin aclarar su etiología.

El uso del registro electroencefalográfico continuo en pacientes con alteraciones del estado de conciencia, convulsiones, o estado epiléptico convulsivo y no convulsivo, se ha incrementado en los últimos años porque permite obtener información en tiempo real de la función cerebral y de los cambios en el tiempo; además, facilita la detección de crisis epilépticas subclínicas y electrográficas, estas últimas de gran importancia, ya que no presentan correlación clínica.

Los hallazgos del monitoreo permiten modificar el tratamiento farmacológico y anticonvulsivo, y constituyen una gran ventaja para el médico tratante en la toma de decisiones oportunas que redunden en la mejoría del pronóstico del paciente.

Obesity and its implications on cerebral circulation and intracranial compliance in severe COVID-19

Objective

Multiple factors have been identified as causes of intracranial compliance impairment (ICCI) among patients with obesity. On the other hand, obesity has been linked with worst outcomes in COVID-19. Thus, the hypothesis of severe acute respiratory syndrome (SARS) conducing to cerebral hemodynamic disorders (CHD) able to worsen ICCI and play an additional role on prognosis determination for COVID-19 among obese patients becomes suitable.

Methods

50 cases of SARS by COVID-19 were evaluated, for the presence of ICCI and cerebrovascular circulatory disturbances in correspondence with whether unfavorable outcomes (death or impossibility for mechanical ventilation weaning [MVW]) within 7 days after evaluation. The objective was to observe whether obese patients (BMI ≥ 30) disclosed worse outcomes and tests results compared with lean subjects with same clinical background.

Results

23 (46%) patients among 50 had obesity. ICCI was verified in 18 (78%) obese, whereas in 13 (48%) of 27 non-obese (p = 0,029). CHD were not significantly different between groups, despite being high prevalent in both. 69% unfavorable outcomes were observed among obese and 44% for lean subjects (p = 0,075).

Conclusion

In the present study, intracranial compliance impairment was significantly more observed among obese subjects and may have contributed for SARS COVID-19 worsen prognosis.

Effects of Positive End-Expiratory Pressure on Lung Recruitment, Respiratory Mechanics, and Intracranial Pressure in Mechanically Ventilated Brain-Injured Patients

Background: The pathophysiological effects of positive end-expiratory pressure (PEEP) on respiratory mechanics, lung recruitment, and intracranial pressure (ICP) in acute brain-injured patients have not been completely elucidated. The primary aim of this study was to assess the effects of PEEP augmentation on respiratory mechanics, quantitative computed lung tomography (qCT) findings, and its relationship with ICP modifications. Secondary aims included the assessment of the correlations between different factors (respiratory mechanics and qCT features) with the changes of ICP and how these factors at baseline may predict ICP response after greater PEEP levels.

Methods: A prospective, observational study included mechanically ventilated patients with acute brain injury requiring invasive ICP and who underwent two-PEEP levels lung CT scan. Respiratory system compliance (Crs), arterial partial pressure of carbon dioxide (PaCO₂), mean arterial pressure (MAP), data from qCT and ICP were obtained at PEEP 5 and 15 cmH₂O.

Results: Sixteen examinations (double PEEP lung CT and neuromonitoring) in 15 patients were analyzed. The median age of the patients was 54 years (interquartile range, IQR = 39–65) and 53% were men. The median Glasgow Coma Scale (GCS) at intensive care unit (ICU) admission was 8 (IQR = 3–12). Median alveolar recruitment was 2.5% of total lung weight (−1.5 to 4.7). PEEP from 5 to 15 cmH₂O increased ICP [median values from 14.0 (11.2–17.5) to 23.5 (19.5–26.8) mmHg, p < 0.001, respectively]. The amount of recruited lung tissue on CT was inversely correlated with the change (Δ) in ICP (rho = −0.78; p = 0.0006). Additionally, ΔCrs (rho = −0.77, p = 0.008), ΔPaCO₂ (rho = 0.81, p = 0.0003), and ΔMAP (rho = −0.64, p = 0.009) were correlated with ΔICP. Baseline Crs was not predictive of ICP response to PEEP.

Conclusions: The main factors associated with increased ICP after PEEP augmentation included reduced Crs, lower MAP and lung recruitment, and increased PaCO₂, but none of these factors was able to predict, at baseline, ICP response to PEEP. To assess the potential benefits of increased PEEP in patients with acute brain injury, hemodynamic status, respiratory mechanics, and lung morphology should be taken into account.

An amplitude-based characteristic parameter extraction algorithm for cerebral edema detection based on electromagnetic induction

Background

Cerebral edema is a common condition secondary to any type of neurological injury. The early diagnosis and monitoring of cerebral edema is of great importance to improve the prognosis. In this article, a flexible conformal electromagnetic two-coil sensor was employed as the electromagnetic induction sensor, associated with a vector network analyzer (VNA) for signal generation and receiving. Measurement of amplitude data over the frequency range of 1–100 MHz is conducted to evaluate the changes in cerebral edema. We proposed an Amplitude-based Characteristic Parameter Extraction (Ab-CPE) algorithm for multi-frequency characteristic analysis over the frequency range of 1–100 MHz and investigated its performance in electromagnetic induction-based cerebral edema detection and distinction of its acute/chronic phase. Fourteen rabbits were enrolled to establish cerebral edema model and the 24 h real-time monitoring experiments were carried out for algorithm verification.

Results

The proposed Ab-CPE algorithm was able to detect cerebral edema with a sensitivity of 94.1% and specificity of 95.4%. Also, in the early stage, it can detect cerebral edema with a sensitivity of 85.0% and specificity of 87.5%. Moreover, the Ab-CPE algorithm was able to distinguish between acute and chronic phase of cerebral edema with a sensitivity of 85.0% and specificity of 91.0%.

Conclusion

The proposed Ab-CPE algorithm is suitable for multi-frequency characteristic analysis. Combined with this algorithm, the electromagnetic induction method has an excellent performance on the detection and monitoring of cerebral edema.

Cerebral Hemodynamics and Intracranial Compliance Impairment in Critically Ill COVID-19 Patients: A Pilot Study

Introduction: One of the possible mechanisms by which the new coronavirus (SARS-Cov2) could induce brain damage is the impairment of cerebrovascular hemodynamics (CVH) and intracranial compliance (ICC) due to the elevation of intracranial pressure (ICP). The main objective of this study was to assess the presence of CVH and ICC alterations in patients with COVID-19 and evaluate their association with short-term clinical outcomes. Methods: Fifty consecutive critically ill COVID-19 patients were studied with transcranial Doppler (TCD) and non-invasive monitoring of ICC. Subjects were included upon ICU admission; CVH was evaluated using mean flow velocities in the middle cerebral arteries (mCBFV), pulsatility index (PI), and estimated cerebral perfusion pressure (eCPP), while ICC was assessed by using the P2/P1 ratio of the non-invasive ICP curve. A CVH/ICC score was computed using all these variables. The primary composite outcome was unsuccessful in weaning from respiratory support or death on day 7 (defined as UO). Results: At the first assessment (n = 50), only the P2/P1 ratio (median 1.20 [IQRs 1.00-1.28] vs. 1.00 [0.88-1.16]; p = 0.03) and eICP (14 [11-25] vs. 11 [7-15] mmHg; p = 0.01) were significantly higher among patients with an unfavorable outcome (UO) than others. Patients with UO had a significantly higher CVH/ICC score (9 [8-12] vs. 6 [5-7]; p < 0.001) than those with a favorable outcome; the area under the receiver operating curve (AUROC) for CVH/ICC score to predict UO was 0.86 (95% CIs 0.75-0.97); a score > 8.5 had 63 (46-77)% sensitivity and 87 (62-97)% specificity to predict UO. For those patients undergoing a second assessment (n = 29), after a median of 11 (5-31) days, all measured variables were similar between the two time-points. No differences in the measured variables between ICU non-survivors (n = 30) and survivors were observed. Conclusions: ICC impairment and CVH disturbances are often present in COVID-19 severe illness and could accurately predict an early poor outcome.

Early Effects of Passive Leg-Raising Test, Fluid Challenge, and Norepinephrine on Cerebral Autoregulation and Oxygenation in COVID-19 Critically Ill Patients

Background: Coronavirus disease 2019 (COVID-19) patients are at high risk of neurological complications consequent to several factors including persistent hypotension. There is a paucity of data on the effects of therapeutic interventions designed to optimize systemic hemodynamics on cerebral autoregulation (CA) in this group of patients. Methods: Single-center, observational prospective study conducted at San Martino Policlinico Hospital, Genoa, Italy, from October 1 to December 15, 2020. Mechanically ventilated COVID-19 patients, who had at least one episode of hypotension and received a passive leg raising (PLR) test, were included. They were then treated with fluid challenge (FC) and/or norepinephrine (NE), according to patients' clinical conditions, at different moments. The primary outcome was to assess the early effects of PLR test and of FC and NE [when clinically indicated to maintain adequate mean arterial pressure (MAP)] on CA (CA index) measured by transcranial Doppler (TCD). Secondary outcomes were to evaluate the effects of PLR test, FC, and NE on systemic hemodynamic variables, cerebral oxygenation (rSo₂), and non-invasive intracranial pressure (nICP). Results: Twenty-three patients were included and underwent PLR test. Of these, 22 patients received FC and 14 were treated with NE. The median age was 62 years (interquartile range = 57-68.5 years), and 78% were male. PLR test led to a low CA index [58% (44-76.3%)]. FC and NE administration resulted in a CA index of 90.8% (74.2-100%) and 100% (100-100%), respectively. After PLR test, nICP based on pulsatility index and nICP based on flow velocity diastolic formula was increased [18.6 (17.7-19.6) vs. 19.3 (18.2-19.8) mm Hg, p = 0.009, and 12.9 (8.5-18) vs. 15 (10.5-19.7) mm Hg, p = 0.001, respectively]. PLR test, FC, and NE resulted in a significant increase in MAP and rSo₂. Conclusions: In mechanically ventilated severe COVID-19 patients, PLR test adversely affects CA. An individualized strategy aimed at assessing both the hemodynamic and cerebral needs is warranted in patients at high risk of neurological complications.

Management of intracranial hypertension following traumatic brain injury: a best clinical practice adoption proposal for intracranial pressure monitoring and decompressive craniectomy. Joint statements by the Traumatic Brain Injury Section of the Italian Society of Neurosurgery (SINch) and the Neuroanesthesia and Neurocritical Care Study Group of the Italian Society of Anesthesia, Analgesia, Resuscitation and Intensive Care (SIAARTI)

No robust evidence is provided by literature regarding the management of intracranial hypertension following severe traumatic brain injury (TBI). This is mostly due to the lack of prospective randomized controlled trials (RCTs), the presence of studies containing extreme heterogeneously collected populations and controversial considerations about chosen outcome. A scientific society should provide guidelines for care management and scientific support for those areas for which evidence-based medicine has not been identified. However, RCTs in severe TBI have failed to establish intervention effectiveness, arising the need to make greater use of tools such as Consensus Conferences between experts, which have the advantage of providing recommendations based on experience, on the analysis of updated literature data and on the direct comparison of different logistic realities. The Italian scientific societies should provide guidelines following the national laws ruling the best medical practice. However, many limitations do not allow the collection of data supporting high levels of evidence for intracranial pressure (ICP) monitoring and decompressive craniectomy (DC) in patients with severe TBI. This intersociety document proposes best practice guidelines for this subsetting of patients to be adopted on a national Italian level, along with joint statements from "TBI Section" of the Italian Society of Neurosurgery (SINch) endorsed by the Neuroanesthesia and Neurocritical Care Study Group of the Italian Society of Anesthesia, Analgesia, Resuscitation and Intensive Care (SIAARTI). Presented here is a recap of recommendations on management of ICP and DC supported a high level of available evidence and rate of agreement expressed by the assemblies during the more recent consensus conferences, where members of both groups have had a role of active participants and supporters. The listed recommendations have been sent to a panel of experts consisting of the 107 members of the "TBI Section" of the SINch and the 111 members of the Neuroanesthesia and Neurocritical Care Study Group of the SIAARTI. The aim of the survey was to test a preliminary evaluation of the grade of predictable future adherence of the recommendations following this intersociety proposal. The following recommendations are suggested as representing best clinical practice, nevertheless, adoption of local multidisciplinary protocols regarding thresholds of ICP values, drug therapies, hemostasis management and perioperative care of decompressed patients is strongly recommended to improve treatment efficiency, to increase the quality of data collection and to provide more powerful evidence with future studies. Thus, for this future perspective a rapid overview of the role of the multimodal neuromonitoring in the optimal severe TBI management is also provided in this document. It is reasonable to assume that the recommendations reported in this paper will in future be updated by new observations arising from future trials. They are not binding, and this document should be offered as a guidance for clinical practice through an intersociety agreement, taking in consideration the low level of evidence.

Transcranial sonographic assessment of the third ventricle in neuro-ICU patients to detect hydrocephalus: a diagnostic reliability pilot study

Background

Transcranial sonography is a point-of-care tool recommended in intensive care units (ICU) to monitor brain injured patients. Objectives of the study was to assess feasibility and reliability of the third ventricle (V3) diameter measurement using transcranial sonography (TCS) compared to brain computed-tomography (CT), the gold standard measurement, and to measure the TCS learning curve. Design: prospective study, in a 16-bed neurological ICU in an academic hospital. Every consecutive brain injured adult patient, who required a brain CT and TCS monitoring were included. The V3 diameter was blindly measured by TCS and CT. Intraclass correlation coefficient (ICC) and Bland–Altman plot were used to assess the reliability and agreement between TCS and CT V3 measurements. Diagnosis performance of the V3 diameter using TCS to detect hydrocephalus was measured. Absolute difference between V3 measurement by residents and experts was measured consecutively to assess the learning curve.

Results

Among the 100 patients included in the study, V3 diameter could be assessed in 87 patients (87%) from at least one side of the skull. Both temporal windows were available in 70 patients (70%). The ICC between V3 diameter measured by TCS and CT was 0.90 [95% CI 0.84–0.93] on the right side, and 0.92 [0.88–0.95] on the left side. In Bland–Altman analysis, mean difference, standard deviation, 95% limits of agreement were 0.36, 1.52, − 2.7 to 3.3 mm, respectively, on the right side; 0.25, 1.47, − 2.7 to 3.1 mm, respectively, on the left side. Among the 35 patients with hydrocephalus, V3 diameters could be measured by TCS in 31 patients (89%) from at least one side. Hydrocephalus was, respectively, excluded, confirmed, or inconclusive using TCS in 35 (40%), 25 (29%) and 27 (31%) of the 87 assessable patients. After 5 measurements, every resident reached a satisfactory measurement compared to the expert operator.

Conclusion

TCS allows rapid, simple and reliable V3 diameter measurement compared with the gold standard in neuro-ICU patients. Aside from sparing irradiating procedures and transfers to the radiology department, it may especially increase close patient monitoring to detect clinically occult hydrocephalus earlier. Further studies are needed to measure the potential clinical benefit of this method.

Trial registration: ClinicalTrials.gov ID: NCT02830269.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00857-x.

Blunt and Penetrating Severe Traumatic Brain Injury

Severe traumatic brain injury is a common problem. Current practices focus on the importance of early resuscitation, transfer to high-volume centers, and provider expertise across multiple specialties. In the emergency department, patients should receive urgent intracranial imaging and consideration for tranexamic acid. Close observation in the intensive care unit environment helps identify problems, such as seizure, intracranial pressure crisis, and injury progression. In addition to traditional neurologic examination, patients benefit from use of intracranial monitors. Monitors gather physiologic data on intracranial and cerebral perfusion pressures to help guide therapy. Brain tissue oxygenation monitoring and cerebromicrodialysis show promise in studies.

Early effects of ventilatory rescue therapies on systemic and cerebral oxygenation in mechanically ventilated COVID-19 patients with acute respiratory distress syndrome: a prospective observational study

BACKGROUND

In COVID-19 patients with acute respiratory distress syndrome (ARDS), the effectiveness of ventilatory rescue strategies remains uncertain, with controversial efficacy on systemic oxygenation and no data available regarding cerebral oxygenation and hemodynamics.

METHODS

This is a prospective observational study conducted at San Martino Policlinico Hospital, Genoa, Italy. We included adult COVID-19 patients who underwent at least one of the following rescue therapies: recruitment maneuvers (RMs), prone positioning (PP), inhaled nitric oxide (iNO), and extracorporeal carbon dioxide (CO2) removal (ECCO2R). Arterial blood gas values (oxygen saturation [SpO2], partial pressure of oxygen [PaO2] and of carbon dioxide [PaCO2]) and cerebral oxygenation (rSO2) were analyzed before (T0) and after (T1) the use of any of the aforementioned rescue therapies. The primary aim was to assess the early effects of different ventilatory rescue therapies on systemic and cerebral oxygenation. The secondary aim was to evaluate the correlation between systemic and cerebral oxygenation in COVID-19 patients.

RESULTS

Forty-five rescue therapies were performed in 22 patients. The median [interquartile range] age of the population was 62 [57-69] years, and 18/22 [82%] were male. After RMs, no significant changes were observed in systemic PaO2 and PaCO2 values, but cerebral oxygenation decreased significantly (52 [51-54]% vs. 49 [47-50]%, p < 0.001). After PP, a significant increase was observed in PaO2 (from 62 [56-71] to 82 [76-87] mmHg, p = 0.005) and rSO2 (from 53 [52-54]% to 60 [59-64]%, p = 0.005). The use of iNO increased PaO2 (from 65 [67-73] to 72 [67-73] mmHg, p = 0.015) and rSO2 (from 53 [51-56]% to 57 [55-59]%, p = 0.007). The use of ECCO2R decreased PaO2 (from 75 [75-79] to 64 [60-70] mmHg, p = 0.009), with reduction of rSO2 values (59 [56-65]% vs. 56 [53-62]%, p = 0.002). In the whole population, a significant relationship was found between SpO2 and rSO2 (R = 0.62, p < 0.001) and between PaO2 and rSO2 (R0 0.54, p < 0.001).

CONCLUSIONS

Rescue therapies exert specific pathophysiological mechanisms, resulting in different effects on systemic and cerebral oxygenation in critically ill COVID-19 patients with ARDS. Cerebral and systemic oxygenation are correlated. The choice of rescue strategy to be adopted should take into account both lung and brain needs. Registration The study protocol was approved by the ethics review board (Comitato Etico Regione Liguria, protocol n. CER Liguria: 23/2020).

Brain Ultrasonography Consensus on Skill Recommendations and Competence Levels Within the Critical Care Setting

BACKGROUND

To report a consensus on the different competency levels for the elaboration of skill recommendations in performing brain ultrasonography within the neurocritical care setting.

METHODS

Four brain ultrasound experts, supported by a methodologist, performed a preselection of indicators and skills based on the current literature and clinical expertise. An international panel of experts was recruited and subjected to web-based questionnaires according to a Delphi method presented in three separate rounds. A pre-defined threshold of agreement was established on expert subjective opinions, > 84% of votes was set to support a strong recommendation and > 68% for a weak recommendation. Below these thresholds, no recommendation reached.

RESULTS

We defined four different skill levels (basic, basic-plus, pre-advanced, advanced). Twenty-five experts participated to the full process. After four rounds of questions, two items received a strong recommendation in the basic skill category, three in the advanced, twelve in the basic-plus, and seven in the pre-advanced. Two items in the pre-advanced category received a weak recommendation and three could not be collocated and were excluded from the list.

CONCLUSIONS

Results from this consensus permitted stratification of the different ultrasound examination skills in four levels with progressively increasing competences. This consensus can be useful as a guide for beginners in brain ultrasonography and for the development of specific training programs within this field.

Estimation of intracranial pressure by ultrasound of the optic nerve sheath in an animal model of intracranial hypertension

BACKGROUND

Ultrasound of the optic nerve sheath diameter (ONSD) has been used as a non-invasive and cost-effective bedside alternative to invasive intracranial pressure (ICP) monitoring. However, ONSD time-lapse behavior in intracranial hypertension (ICH) and its relief by means of either saline infusion or surgery are still unknown. The objective of this study was to correlate intracranial pressure (ICP) and ultrasonography of the optic nerve sheath (ONS) in an experimental animal model of ICH and determine the interval needed for ONSD to return to baseline levels.

METHODS

An experimental study was conducted on 30 pigs. ONSD was evaluated by ultrasound at different ICPs generated by intracranial balloon inflation, saline infusion, and balloon deflation, and measured using an intraventricular catheter.

RESULTS

All variables obtained by ONS ultrasonography such as left, right, and average ONSD (AON) were statistically significant to estimate the ICP value. ONSD changed immediately after balloon inflation and returned to baseline after an average delay of 30 min after balloon deflation (p = 0.016). No statistical significance was observed in the ICP and ONSD values with hypertonic saline infusion. In this swine model, ICP and ONSD showed linear correlation and ICP could be estimated using the formula: -80.5 + 238.2 × AON.

CONCLUSION

In the present study, ultrasound to measure ONSD showed a linear correlation with ICP, although a short delay in returning to baseline levels was observed in the case of sudden ICH relief.

Correlation Between Invasive and Noninvasive Technique of Intracranial Pressure Measurement in Children With Traumatic Brain Injury: An Observational Study

BACKGROUND

Direct measurement of intracranial pressure (ICP) is an invasive technique with potential complications, which has prompted the development of alternative, noninvasive, methods of ICP assessment. The aim of this study was to determine the relationship between noninvasive ultrasound-based measurement of optic nerve sheath diameter (ONSD), transcranial Doppler-derived pulsatility index (PI), and invasive ICP measurements in children with traumatic brain injury (TBI).

METHODS

Children aged 1 to 18 years undergoing invasive ICP monitoring following TBI were included in the study. Noninvasive ONSD and PI measurements were compared with simultaneous invasive ICP.

RESULTS

In all, 406 measurements of ONSD and PI were obtained in 18 patients. ONSD and PI correlated with ICP (r=0.76 and 0.79, respectively), combining ONSD and PI resulted in an even stronger correlation with ICP (r=0.99). Formulas were derived from mixed-effect models that best fitted the data for noninvasive ICP estimation. A combination of ONSD and PI had the highest ability to detect ICP >20 mm Hg (area under the receiver operating characteristic curve=0.99, 95% confidence interval: 0.99-1.00). Optimal cutoff values for the prediction of intracranial hypertension were 5.95 mm for ONSD (sensitivity, 92%; specificity, 76%) and 1.065 for PI (sensitivity, 92%; specificity, 87%).

CONCLUSIONS

In children with TBI, a combination of ONSD and PI strongly correlates with invasive ICP and has potential to screen for intracranial hypertension noninvasively. ONSD and PI may be useful tools for assessing ICP where invasive monitoring is unavailable or contraindicated.

Neurological Complications and Noninvasive Multimodal Neuromonitoring in Critically Ill Mechanically Ventilated COVID-19 Patients

Purpose: The incidence and the clinical presentation of neurological manifestations of coronavirus disease-2019 (COVID-19) remain unclear. No data regarding the use of neuromonitoring tools in this group of patients are available. Methods: This is a retrospective study of prospectively collected data. The primary aim was to assess the incidence and the type of neurological complications in critically ill COVID-19 patients and their effect on survival as well as on hospital and intensive care unit (ICU) length of stay. The secondary aim was to describe cerebral hemodynamic changes detected by noninvasive neuromonitoring modalities such as transcranial Doppler, optic nerve sheath diameter (ONSD), and automated pupillometry. Results: Ninety-four patients with COVID-19 admitted to an ICU from February 28 to June 30, 2020, were included in this study. Fifty-three patients underwent noninvasive neuromonitoring. Neurological complications were detected in 50% of patients, with delirium as the most common manifestation. Patients with neurological complications, compared to those without, had longer hospital (36.8 ± 25.1 vs. 19.4 ± 16.9 days, p < 0.001) and ICU (31.5 ± 22.6 vs. 11.5±10.1 days, p < 0.001) stay. The duration of mechanical ventilation was independently associated with the risk of developing neurological complications (odds ratio 1.100, 95% CI 1.046-1.175, p = 0.001). Patients with increased intracranial pressure measured by ONSD (19% of the overall population) had longer ICU stay. Conclusions: Neurological complications are common in critically ill patients with COVID-19 receiving invasive mechanical ventilation and are associated with prolonged ICU length of stay. Multimodal noninvasive neuromonitoring systems are useful tools for the early detection of variations in cerebrovascular parameters in COVID-19.

Prehospital Detection of Life-Threatening Intracranial Pathology: An Unmet Need for Severe TBI in Austere, Rural, and Remote Areas

Severe traumatic brain injury (TBI) is a leading cause of death and disability worldwide, especially in low- and middle-income countries, and in austere, rural, and remote settings. The purpose of this Perspective is to challenge the notion that accurate and actionable diagnosis of the most severe brain injuries should be limited to physicians and other highly-trained specialists located at hospitals. Further, we aim to demonstrate that the great opportunity to improve severe TBI care is in the prehospital setting. Here, we discuss potential applications of prehospital diagnostics, including ultrasound and near-infrared spectroscopy (NIRS) for detection of life-threatening subdural and epidural hemorrhage, as well as monitoring of cerebral hemodynamics following severe TBI. Ultrasound-based methods for assessment of cerebrovascular hemodynamics, vasospasm, and intracranial pressure have substantial promise, but have been mainly used in hospital settings; substantial development will be required for prehospital optimization. Compared to ultrasound, NIRS is better suited to assess certain aspects of intracranial pathology and has a smaller form factor. Thus, NIRS is potentially closer to becoming a reliable method for non-invasive intracranial assessment and cerebral monitoring in the prehospital setting. While one current continuous wave NIRS-based device has been FDA-approved for detection of subdural and epidural hemorrhage, NIRS methods using frequency domain technology have greater potential to improve diagnosis and monitoring in the prehospital setting. In addition to better technology, advances in large animal models, provider training, and implementation science represent opportunities to accelerate progress in prehospital care for severe TBI in austere, rural, and remote areas.