Brain Multimodality Monitoring: A New Tool in Neurocritical Care of Comatose Patients

Altered levels of transthyretin in human cerebral microdialysate after subarachnoid haemorrhage using proteomics; a descriptive pilot study

BACKGROUND

Subarachnoid haemorrhage (SAH) is one of the most severe forms of stroke in which delayed cerebral ischemia is one of the major complications. Neurointensive care aims at preventing and treating such complications and identification of biomarkers of early signs of ischemia might therefore be helpful.

METHODS

We aimed at describing proteome profile in cerebral microdialysate in four patients with aneurysmal SAH using two dimensional gel electrophoresis in combination with mass spectrometry in search for new biomarkers for delayed cerebral ischemia and to investigate if there were temporal fluctuations in those biomarkers over time after aneurysmal bleed.

RESULTS

The results showed transthyretin in nine different proteoforms (1001, 1102, 2101, 3101, 4101, 4102, 5001, 5101, 6101) in cerebral microdialysate samples from four patients having sustained SAH. Several proteoforms show highly differing levels and pooled analysis of all samples showed varying optical density related to time from aneurysmal bleed, indicating a temporal evolution.

CONCLUSIONS

Transthyretin proteoforms have not earlier been shown in cerebral microdialysate after SAH and we describe differing levels based on proteoform as well as time from subarachnoid bleed. Transthyretin is well known to be synthetized in choroid plexus, whilst intraparenchymal synthesis remains controversial. The results need to be confirmed in larger studies in order to further describe transthyretin.

Invasive Neuromonitoring in the Stroke Patient

With advances in technology, the options to manage patients with neurologic injuries are often complex. Critical care management of neurologic injury has historically focused on the prevention of secondary ischemic injury through aggressive management of intracranial pressure (ICP) and maintenance of adequate cerebral perfusion pressure (CPP). However, ICP monitoring alone does not identify ischemic changes that herald patient deterioration. Advocates of multimodality monitoring cite the value of early detection of changes in brain oxygenation levels and brain metabolism as advantageous in optimizing stroke outcomes. ICP monitoring alone should not be the sole source of information on which therapy is guided but should be incorporated into the arsenal of emerging and promising invasive neuromonitoring devices.

Multimodal monitoring: practical recommendations (dos and don'ts) in challenging situations and uncertainty

With the advancements in modern medicine, new methods are being developed to monitor patients in the intensive care unit. Different modalities evaluate different aspects of the patient's physiology and clinical status. The complexity of these modalities often restricts their use to the realm of clinical research, thereby limiting their use in the real world. Understanding their salient features and their limitations can aid physicians in interpreting the concomitant information provided by multiple modalities to make informed decisions that may affect clinical care and outcomes. Here, we present a review of the commonly used methods in the neurological intensive care unit with practical recommendations for their use.

Cerebral multimodality monitoring in adult neurocritical care patients with acute brain injury: A narrative review

Cerebral multimodality monitoring (MMM) is, even with a general lack of Class I evidence, increasingly recognized as a tool to support clinical decision-making in the neuroscience intensive care unit (NICU). However, literature and guidelines have focused on unimodal signals in a specific form of acute brain injury. Integrating unimodal signals in multiple signal monitoring is the next step for clinical studies and patient care. As such, we aimed to investigate the recent application of MMM in studies of adult patients with traumatic brain injury (TBI), subarachnoid hemorrhage (SAH), intracerebral hemorrhage (ICH), acute ischemic stroke (AIS), and hypoxic ischemic brain injury following cardiac arrest (HIBI). We identified continuous or daily updated monitoring modalities and summarized the monitoring setting, study setting, and clinical characteristics. In addition, we discussed clinical outcome in intervention studies. We identified 112 MMM studies, including 11 modalities, over the last 7 years (2015-2022). Fifty-eight studies (52%) applied only two modalities. Most frequently combined were ICP monitoring (92 studies (82%)) together with PbtO₂ (63 studies (56%). Most studies included patients with TBI (59 studies) or SAH (53 studies). The enrollment period of 34 studies (30%) took more than 5 years, whereas the median sample size was only 36 patients (q1- q3, 20-74). We classified studies as either observational (68 studies) or interventional (44 studies). The interventions were subclassified as systemic (24 studies), cerebral (10 studies), and interventions guided by MMM (11 studies). We identified 20 different systemic or cerebral interventions. Nine (9/11, 82%) of the MMM-guided studies included clinical outcome as an endpoint. In 78% (7/9) of these MMM-guided intervention studies, a significant improvement in outcome was demonstrated in favor of interventions guided by MMM. Clinical outcome may be improved with interventions guided by MMM. This strengthens the belief in this application, but further interdisciplinary collaborations are needed to overcome the heterogeneity, as illustrated in the present review. Future research should focus on increasing sample sizes, improved data collection, refining definitions of secondary injuries, and standardized interventions. Only then can we proceed with complex outcome studies with MMM-guided treatment.

Noninvasive Intracranial Pressure Monitoring in Chronic Stroke Patients with Sedentary Behavior: A Pilot Study

OBJECTIVE

This study aimed to correlate the P2/P1 ratio of intracranial pressure waveforms with sedentary behavior during the chronic stage of stroke.

MATERIALS AND METHODS

Eight patients from São Carlos, Brazil, who had hemiparesis and stroke onset within the previous 6 months, participated in this study. To monitor their intracranial pressure, we used noninvasive Brain4Care^® intracranial pressure monitoring during a postural change maneuver involving 15 min in a supine position and 15 min in an orthostatic position. The patients' sedentary behavior was continually monitored at home using a StepWatch Activity Monitor™ for 1 week. Moreover, the patients completed the International Physical Activity Questionnaire before and after using the StepWatch Activity Monitor™.

RESULTS

In the supine and orthostatic positions, the P2/P1 ratios were 0.84 ± 0.14 and 0.98 ± 0.17, respectively. The percentage of time spent in inactivity was 71 ± 11%, and the number of steps walked per day was 4220 ± 2239. We found a high positive correlation (r = 0.881, p = 0.004) between the P2/P1 ratio and the percentage of time spent in inactivity.

CONCLUSION

This preliminary study showed a correlation between sedentary behavior and cerebral compliance. Thus, monitoring of intracranial pressure during the late stage of a stroke could guide the clinician's treatment to reduce sedentary behavior and the risks of recurrent stroke and cardiovascular diseases.

Machine Learning Applications in the Neuro ICU: A Solution to Big Data Mayhem?

The neurological ICU (neuro ICU) often suffers from significant limitations due to scarce resource availability for their neurocritical care patients. Neuro ICU patients require frequent neurological evaluations, continuous monitoring of various physiological parameters, frequent imaging, and routine lab testing. This amasses large amounts of data specific to each patient. Neuro ICU teams are often overburdened by the resulting complexity of data for each patient. Machine Learning algorithms (ML), are uniquely capable of interpreting high-dimensional datasets that are too difficult for humans to comprehend. Therefore, the application of ML in the neuro ICU could alleviate the burden of analyzing big datasets for each patient. This review serves to (1) briefly summarize ML and compare the different types of MLs, (2) review recent ML applications to improve neuro ICU management and (3) describe the future implications of ML to neuro ICU management.

IRIS: A Modular Platform for Continuous Monitoring and Caretaker Notification in the Intensive Care Unit

OBJECTIVE

New approaches are needed to interpret large amounts of physiologic data continuously recorded in the ICU. We developed and prospectively validated a versatile platform (IRIS) for real-time ICU physiologic monitoring, clinical decision making, and caretaker notification.

METHODS

IRIS was implemented in the neurointensive care unit to stream multimodal time series data, including EEG, intracranial pressure (ICP), and brain tissue oxygenation (PbtO2), from ICU monitors to an analysis server. IRIS was applied for 364 patients undergoing continuous EEG, 26 patients undergoing burst suppression monitoring, and four patients undergoing intracranial pressure and brain tissue oxygen monitoring. Custom algorithms were used to identify periods of elevated ICP, compute burst suppression ratios (BSRs), and detect faulty or disconnected EEG electrodes. Hospital staff were notified of clinically relevant events using our secure API to route alerts through a password-protected smartphone application.

RESULTS

Sustained increases in ICP and concordant decreases in PbtO2 were reliably detected using user-defined thresholds and alert throttling. BSR trends computed by the platform correlated highly with manual neurologist markings (r2 0.633-0.781; p < 0.0001). The platform identified EEG electrodes with poor signal quality with 95% positive predictive value, and reduced latency of technician response by 93%.

CONCLUSION

This study validates a flexible real-time platform for monitoring and interpreting ICU data and notifying caretakers of actionable results, with potential to reduce the manual burden of continuous monitoring services on care providers.

SIGNIFICANCE

This work represents an important step toward facilitating translational medical data analytics to improve patient care and reduce health care costs.

Electrochemical Evaluation of a Multi-Site Clinical Depth Recording Electrode for Monitoring Cerebral Tissue Oxygen

The intracranial measurement of local cerebral tissue oxygen levels—PbtO₂—has become a useful tool for the critical care unit to investigate severe trauma and ischemia injury in patients. Our preliminary work in animal models supports the hypothesis that multi-site depth electrode recording of PbtO₂ may give surgeons and critical care providers needed information about brain viability and the capacity for better recovery. Here, we present a surface morphology characterization and an electrochemical evaluation of the analytical properties toward oxygen detection of an FDA-approved, commercially available, clinical grade depth recording electrode comprising 12 Pt recording contacts. We found that the surface of the recording sites is composed of a thin film of smooth Pt and that the electrochemical behavior evaluated by cyclic voltammetry in acidic and neutral electrolyte is typical of polycrystalline Pt surface. The smoothness of the Pt surface was further corroborated by determination of the electrochemical active surface, confirming a roughness factor of 0.9. At an optimal working potential of −0.6 V vs. Ag/AgCl, the sensor displayed suitable values of sensitivity and limit of detection for in vivo PbtO₂ measurements. Based on the reported catalytical properties of Pt toward the electroreduction reaction of O₂, we propose that these probes could be repurposed for multisite monitoring of PbtO₂ in vivo in the human brain.

An overview of management of intracranial hypertension in the intensive care unit

Intracranial hypertension (IH) is a clinical condition commonly encountered in the intensive care unit, which requires immediate treatment. The maintenance of normal intracranial pressure (ICP) and cerebral perfusion pressure in order to prevent secondary brain injury (SBI) is the central focus of management. SBI can be detected through clinical examination and invasive and non-invasive ICP monitoring. Progress in monitoring and understanding the pathophysiological mechanisms of IH allows the implementation of targeted interventions in order to improve the outcome of these patients. Initially, general prophylactic measures such as patient's head elevation, fever control, adequate analgesia and sedation depth should be applied immediately to all patients with suspected IH. Based on specific indications and conditions, surgical resection of mass lesions and cerebrospinal fluid drainage should be considered as an initial treatment for lowering ICP. Hyperosmolar therapy (mannitol or hypertonic saline) represents the cornerstone of medical treatment of acute IH while hyperventilation should be limited to emergency management of life-threatening raised ICP. Therapeutic hypothermia could have a possible benefit on outcome. To control elevated ICP refractory to maximum standard medical and surgical treatment, at first, high-dose barbiturate administration and then decompressive craniectomy as a last step are recommended with unclear and probable benefit on outcomes, respectively. The therapeutic strategy should be based on a staircase approach and be individualized for each patient. Since most therapeutic interventions have an uncertain effect on neurological outcome and mortality, future research should focus on both studying the long-term benefits of current strategies and developing new ones.

Current Status and Recommendations in Multimodal Neuromonitoring

Every patient in neurocritical care evolves through two phases. Acute pathologies are addressed first. These include trauma, hemorrhagic or ischemic stroke, or neuroinfection. Soon after, the concentration shifts to identifying secondary pathologies like fever, seizures, and ischemia, which may exacerbate the brain injury. Frequent bedside examinations are not sufficient for timely detection and prevention of secondary brain injury (SBI) as per the International Multidisciplinary Consensus Conference on Multimodality Monitoring in Neurocritical Care. Multimodality monitoring (MMM) can help in tailoring treatment decisions to prevent such a brain injury. Multimodal neuromonitoring involves data-guided therapeutic interventions by employing various tools and data integration to understand brain physiology. Monitors provide real-time information on cerebral hemodynamics, oxygenation, metabolism, and electrophysiology. The monitors may be invasive/noninvasive and global/regional. We have reviewed such technologies in this write-up. Novel themes like bioinformatics, clinical research, and device development will also be discussed.

The Impact of Intrahospital Transports on Brain Tissue Metabolism in Patients with Acute Brain Injury

BACKGROUND

Patients with severe acute brain injury (ABI) often require intrahospital transports (IHTs) for repeated computed tomography (CT) scans. IHTs are associated with serious adverse events (AE) that might pose a risk for secondary brain injury. The goal of this study was to assess IHT-related alterations of cerebral metabolism in ABI patients.

METHODS

We included mechanically ventilated patients with ABI who had continuous multimodality neuromonitoring during an 8-h period before and after routine IHT. Intracranial pressure (ICP), cerebral perfusion pressure (CPP), brain tissue oxygenation (PtiO₂) as well as cerebral and subcutaneous microdialysis parameters (lactate, pyruvate, glycerol, and glutamate) were recorded. Values were compared between an 8-h period before (pre-IHT) and after (post-IHT) the IHT.

RESULTS

A total of 23 IHT for head CT scans in 18 patients were analyzed. Traumatic brain injury (n = 7) was the leading cause of ABI, followed by subarachnoid hemorrhage (n = 6) and intracerebral hemorrhage (n = 5). The analyzed microdialysis parameters in the brain tissue as in the subcutaneous tissue did not show significant changes between the pre-IHT and post-IHT period. In addition, we observed no significant increase in ICP or decrease in CPP and PtiO₂ in the 8-h period after IHT.

CONCLUSIONS

While the occurrence of AE during IHT is a known risk factor for ABI patients, our results demonstrate that IHTs do not alter the brain tissue chemistry in a significant manner. This fact may help assess the risk for routine IHT more accurately.

Multimodal Neuromonitoring in Neurocritical Care

Neuromonitoring is important for patients with acute brain injury. The bedside neurologic examination is standard for neurologic monitoring; however, a clinical examination may not reliably detect subtle changes in intracranial physiology. Changes found during neurologic examinations are often late signs. The assessment of multiple physiological variables in real time can provide new clinical insights into treatment decisions. No single monitoring modality is ideal for all patients. Simultaneous assessment of cerebral hemodynamics, oxygenation, and metabolism, such as in multimodal monitoring, allows an innovative approach to individualized patient care.

Laboratory biomarkers of delayed cerebral ischemia after subarachnoid hemorrhage: a systematic review

Delayed cerebral ischemia (DCI) is a severe complication of subarachnoid hemorrhage (SAH). Clinical and radiographic features of SAH may be helpful in identification of individuals prone to DCI. The aim of this systematic review was to analyze the present evidence on predictive value of blood and cerebrospinal fluid (CSF) biomarkers of DCI after SAH. We systematically searched in PubMed, Scopus, Web of Science, and Cochrane Library databases for publications before July 15, 2018, reporting correlations between blood/CSF biomarkers and occurrence of DCI and/or vasospasm in SAH patients. Included studies underwent quality assessment according to QUIPS and STARD guidelines. Level of evidence (I-IV) for each of tested biomarkers was assessed according to GRADE guidelines. Of 2181 unique records identified in four databases, 270 original articles and 5 meta-analyses were included to this review. Of 257 blood and CSF parameters analyzed in 16.914 SAH patients, there was no biomarker with positive association with DCI/vasospasm showing level I evidence. Twenty-one biomarkers achieved level II evidence and could be confirmed as predictive biomarkers. In this review, six single nucleotide polymorphisms (for EET metabolic pathways, COMT, HMGB1, ACE, PAI-1 promoter, and Hp genes) and 15 non-genetic biomarkers (pNF-H, ADAMTS13, NPY, Copeptin, HMGB1, GFAP, periostin, Tau, BNP, NT pro-BNP, hs-TnT, PA-TEGMA, MPV:PLT, NLR, and PLR) were selected as predictive DCI biomarkers. We propose that a panel analysis of the selected genetic and protein biomarker candidates would be needed for further validation in a large SAH cohort.