Jugular bulb oximetry for prediction of vasospasm following subarachnoid hemorrhage

Could Phosphorous MR Spectroscopy Help Predict the Severity of Vasospasm? A Pilot Study

One of the main causes of the dismal prognosis in patients who survive the initial bleeding after aneurysmal subarachnoidal hemorrhage is the delayed cerebral ischaemia caused by vasospasm. Studies suggest that cerebral magnesium and pH may potentially play a role in the pathophysiology of this adverse event. Using phosphorous magnetic resonance spectrocopy (31P-MRS), we calculated the cerebral magnesium (Mg) and pH levels in 13 patients who suffered from aSAH. The values between the group that developed clinically significant vasospasm (n = 7) and the group that did not (n = 6) were compared. The results of this study show significantly lower cerebral Mg levels (p = 0.019) and higher pH levels (p < 0.001) in the cumulative group (all brain voxels together) in patients who developed clinically significant vasospasm. Further clinical studies on a larger group of carefully selected patients are needed in order to predict clinically significant vasospasm.

Physiological Monitoring in Patients with Acute Brain Injury: A Multimodal Approach

Neurocritical care management of acute brain injury (ABI) is focused on identification, prevention, and management of secondary brain injury (SBI). Physiologic monitoring of the brain and other organ systems has a role to predict patient recovery or deterioration, guide individualized therapeutic interventions, and measure response to treatment, with the goal of improving patient outcomes. In this review, we detail how specific physiologic markers of brain injury and neuromonitoring tools are integrated and used in ABI patients to develop therapeutic approaches to prevent SBI.

Machine Learning and Artificial Intelligence in Neurocritical Care: a Specialty-Wide Disruptive Transformation or a Strategy for Success

PURPOSE OF REVIEW

Neurocritical care combines the complexity of both medical and surgical disease states with the inherent limitations of assessing patients with neurologic injury. Artificial intelligence (AI) has garnered interest in the basic management of these complicated patients as data collection becomes increasingly automated.

RECENT FINDINGS

In this opinion article, we highlight the potential AI has in aiding the clinician in several aspects of neurocritical care, particularly in monitoring and managing intracranial pressure, seizures, hemodynamics, and ventilation. The model-based method and data-driven method are currently the two major AI methods for analyzing critical care data. Both are able to analyze the vast quantities of patient data that are accumulated in the neurocritical care unit. AI has the potential to reduce healthcare costs, minimize delays in patient management, and reduce medical errors. However, these systems are an aid to, not a replacement for, the clinician's judgment.

Artificial intelligence in neurocritical care

BACKGROUND

Neurocritical care combines the management of extremely complex disease states with the inherent limitations of clinically assessing patients with brain injury. As the management of neurocritical care patients can be immensely complicated, the automation of data-collection and basic management by artificial intelligence systems have garnered interest.

METHODS

In this opinion article, we highlight the potential artificial intelligence has in monitoring and managing several aspects of neurocritical care, specifically intracranial pressure, seizure monitoring, blood pressure, and ventilation.

RESULTS

The two major AI methods of analytical technique currently exist for analyzing critical care data: the model-based method and data driven method. Both of these methods have demonstrated an ability to analyze vast quantities of patient data, and we highlight the ways in which these modalities of artificial intelligence might one day play a role in neurocritical care.

CONCLUSIONS

While none of these artificial intelligence systems are meant to replace the clinician's judgment, these systems have the potential to reduce healthcare costs and errors or delays in medical management.

Multimodality Monitoring in Neurocritical Care: Decision-Making Utilizing Direct And Indirect Surrogate Markers

Substantial progress has been made to create innovative technology that can monitor the different physiological characteristics that precede the onset of secondary brain injury, with the ultimate goal of intervening prior to the onset of irreversible neurological damage. One of the goals of neurocritical care is to recognize and preemptively manage secondary neurological injury by analyzing physiologic markers of ischemia and brain injury prior to the development of irreversible damage. This is helpful in a multitude of neurological conditions, whereby secondary neurological injury could present including but not limited to traumatic intracranial hemorrhage and, specifically, subarachnoid hemorrhage, which has the potential of progressing to delayed cerebral ischemia and monitoring postneurosurgical interventions. In this study, we examine the utilization of direct and indirect surrogate physiologic markers of ongoing neurologic injury, including intracranial pressure, cerebral blood flow, and brain metabolism.

Novel minimally invasive multi-modality monitoring modalities in neurocritical care

Elevated intracranial pressure (ICP) following brain injury contributes to poor outcomes for patients, primarily by reducing the caliber of cerebral vasculature, and thereby reducing cerebral blood flow. Careful monitoring of ICP is critical in these patients in order to determine prognosis, implement treatment when ICP becomes elevated, and to judge responsiveness to treatment. Currently, the gold standard for monitoring is invasive pressure transducers, usually an intraventricular monitor, which presents significant risk of infection and hemorrhage. These risks made discovering non-invasive methods for monitoring ICP and cerebral perfusion a priority for researchers. Herein we sought to review recent publications on novel minimally invasive multi-modality monitoring techniques that provide surrogate data on ICP, cerebral oxygenation, metabolism and blood flow. While limitations in various forms preclude them from supplanting the use of invasive monitors, these modalities represent useful screening tools within our armamentarium that may be invaluable when the risks of invasive monitoring outweigh the associated benefits.

Intracranial Multimodality Monitoring for Delayed Cerebral Ischemia

Management of patients with aneurysmal subarachnoid hemorrhage focuses on prevention of rebleeding by early treatment of the aneurysm, as well as detection and management of neurologic and medical complications. Early detection of delayed cerebral ischemia and management of modifiable contributing causes such as vasospasm take a central role, with the goal of preventing irreversible cerebral injury. In efforts to prevent delayed cerebral ischemia, multimodality monitoring has emerged as a promising tool in detecting subclinical physiologic changes before infarction occurs. However, there has been much variability in the utilization of this technology. Recent consensus guidelines discuss the role of multimodality monitoring in acute brain injury. In this review, we evaluate these guidelines and the utility of each modality of multimodality monitoring in aneurysmal subarachnoid hemorrhage.

Multimodal neurologic monitoring

Neurocritical care has two main objectives. Initially, the emphasis is on treatment of patients with acute damage to the central nervous system whether through infection, trauma, or hemorrhagic or ischemic stroke. Thereafter, attention shifts to the identification of secondary processes that may lead to further brain injury, including fever, seizures, and ischemia, among others. Multimodal monitoring is the concept of using various tools and data integration to understand brain physiology and guide therapeutic interventions to prevent secondary brain injury. This chapter will review the use of electroencephalography, intracranial pressure monitoring, brain tissue oxygenation, cerebral microdialysis and neurochemistry, near-infrared spectroscopy, and transcranial Doppler sonography as they relate to neuromonitoring in the critically ill. The concepts and design of each monitor, in addition to the patient population that may most benefit from each modality, will be discussed, along with the various tools that can be used together to guide individualized patient treatment options. Major clinical trials, observational studies, and their effect on clinical outcomes will be reviewed. The future of multimodal monitoring in the field of bioinformatics, clinical research, and device development will conclude the chapter.

Monitoring of brain and systemic oxygenation in neurocritical care patients

Maintenance of adequate oxygenation is a mainstay of intensive care, however, recommendations on the safety, accuracy, and the potential clinical utility of invasive and non-invasive tools to monitor brain and systemic oxygenation in neurocritical care are lacking. A literature search was conducted for English language articles describing bedside brain and systemic oxygen monitoring in neurocritical care patients from 1980 to August 2013. Imaging techniques e.g., PET are not considered. A total of 281 studies were included, the majority described patients with traumatic brain injury (TBI). All tools for oxygen monitoring are safe. Parenchymal brain oxygen (PbtO2) monitoring is accurate to detect brain hypoxia, and it is recommended to titrate individual targets of cerebral perfusion pressure (CPP), ventilator parameters (PaCO2, PaO2), and transfusion, and to manage intracranial hypertension, in combination with ICP monitoring. SjvO2 is less accurate than PbtO2. Given limited data, NIRS is not recommended at present for adult patients who require neurocritical care. Systemic monitoring of oxygen (PaO2, SaO2, SpO2) and CO2 (PaCO2, end-tidal CO2) is recommended in patients who require neurocritical care.

Cerebral vasospasm

Cerebral vasospasm causes delayed ischemic neurologic deficits after aneurysmal subarachnoid hemorrhage. This is a well-established clinical entity with significant associated morbidity and mortality. The underlying patholphysiology is highly complex and poorly understood. Large-vessel vasospasm, autoregulatory dysfunction, inflammation, genetic predispositions, microcirculatory failure, and spreading cortical depolarization are aspects of delayed neurologic deterioration that have been described in the literature. This article presents a perspective on cerebral vasospasm, as guided by the literature to date, specifically examining the mechanism, diagnosis, and treatment of cerebral vasospasm.

Cerebral vasospasm after aneurysmal subarachnoid hemorrhage and traumatic brain injury

OPINION STATEMENT

Cerebral vasospasm (cVSP) consists of the vasoconstriction of large and small intracranial vessels which can lead to cerebral hypoperfusion, and in extreme cases, delayed ischemic deficits with stroke. While most commonly observed after aneurysmal subarachnoid hemorrhage (aSAH), cVSP can also occur after traumatic brain injury (TBI) as we have described in detail in this review. For the past decades, the research attention has focused on cVSP because of its association with delayed cerebral ischemia, which is the largest contributor of morbidity and mortality after aSAH. New discoveries in the cVSP pathophysiology involving multifactorial complex cascades and pathways pose new targets for therapeutic interventions in the prevention and treatment of cVSP. The goal of this review is to demonstrate the commonalities and differences in epidemiology and pathophysiology of both aSAH and TBI-associated cVSP, and highlight the more recently discovered pathways of cVSP. Finally, the latest cVSP surveillance methods and treatment options are illustrated.

Vasospasm after SAH due to aneurysm rupture of the anterior circle of Willis: value of TCD monitoring

OBJECTIVE

The aim of this study was to verify the presence of angiographic vasospasm in patients with transcranial Doppler (TCD) of high velocities after subarachnoid hemorrhage (SAH).

METHODS

Seven hundred and eighty-six cases admitted within 48 hours after SAH due to the rupture of anterior circulation aneurysm, were prospectively studied with TCD. In cases of TCD velocities higher than 120 cm/s (TCD vasospasm), the patient underwent a control angiography. Hunt-Hess and Fisher's grade on admission CT and location of the aneurysm were related to occurrence of TCD vasospasm. The increase in TCD velocities within 24 hours was calculated and related to the presence of cerebral ischemia on discharge CT, considering three groups of patients: Group A with an increase in velocities higher than 60%, Group B with an increase in velocities between 30 and 60%, and Group C with an increase in velocities lower than 30%.

RESULTS

TCD vasospasm was observed in 216 patients (27%). In 97% of patients with TCD vasospasm on middle cerebral artery (MCA) and in 71% with TCD vasospasm on anterior cerebral artery (ACA), control angiography confirmed the vasospasm, with a significant lower diagnostic TCD predictivity of ACA spasm (chi2=28.204, p=0.000). The overall positive predictive value of TCD was 89%. There was no significant correlation of TCD vasospasm with clinical status on admission and location of the aneurysm, but a significant correlation between occurrence of TCD vasospasm and Fisher's grade (chi2=15.470, p=0.002) and between the increase rate in TCD velocities and cerebral ischemia (chi2=56.564, p=0.000).

CONCLUSION

Our study shows a good correlation between TCD and angiography to detect vasospasm on MCA, but the correlation is low for ACA. TCD alone cannot discriminate different hemodynamic pathways after SAH.

Current advances in the diagnosis of vasospasm

Symptomatic vasospasm leading to delayed ischemia and neurological deficits is one of the most serious complications after aneurysmal subarachnoid hemorrhage (SAH). Reliable and early detection of symptomatic vasospasm is one of the major goals in the management of patients with SAH. In awake patients, the close clinical neurological examination still remains the most important diagnostic measure. In comatous or sedated patients, cerebral angiography remains the mainstay of the diagnostic workup for vasospasm. However, angiography does not allow assessing the hemodynamic relevance of vasospasm and is not suited for early identification of cerebral hypoperfusion and ischemia. Therefore, a large panel of new monitoring techniques for the assessment of regional cerebral perfusion has been recently introduced into the clinical management of SAH patients. This article briefly reviews the most relevant methods for monitoring cerebral perfusion and discusses their clinical predictive value for the diagnosis of vasospasm. On the basis of the currently available monitoring technologies, an algorithm for the diagnosis of vasospasm is presented.

Evidence-based cerebral vasospasm surveillance

Subarachnoid hemorrhage related to aneurysmal rupture (aSAH) carries significant morbidity and mortality, and its treatment is focused on preventing secondary injury. The most common—and devastating—complication is delayed cerebral ischemia resulting from vasospasm. In this paper, the authors review the various surveillance technologies available to detect cerebral vasospasm in the days following aSAH. First, evidence related to the most common modalities, including transcranial doppler ultrasonography and computed tomography, are reviewed. Continuous electroencephalography and older instruments such as positron emission tomography, xenon-enhanced CT, and single-photon emission computed tomography are also discussed. Invasive strategies including brain tissue oxygen monitoring, microdialysis, thermal diffusion, and jugular bulb oximetry are examined. Lastly, near-infrared spectroscopy, a recent addition to the field, is briefly reviewed. Each surveillance tool carries its own set of advantages and limitations, and the concomitant use of multiple modalities serves to improve diagnostic sensitivity and specificity.

Invasive and noninvasive multimodal bedside monitoring in subarachnoid hemorrhage: a review of techniques and available data

Delayed-cerebral ischemia is a major cause of morbidity and mortality in the setting of aneurysmal subarachnoid hemorrhage. Despite extensive research efforts and a breadth of collective clinical experience, accurate diagnosis of vasospasm remains difficult, and effective treatment options are limited. Classically, diagnosis has focused on imaging assessment of the cerebral vasculature. Recently, invasive and noninvasive bedside techniques designed to characterize relevant hemodynamic and metabolic alterations have gained substantial attention. Such modalities include microdialysis, brain tissue oxygenation, jugular bulb oximetry, thermal diffusion cerebral blood flow, and near-infrared spectroscopy. This paper reviews these modalities and examines data pertinent to the diagnosis and management of cerebral vasospasm.

Pro/con debate: should PaCO2 be tightly controlled in all patients with acute brain injuries?

You are the attending intensivist in a neurointensive care unit caring for a woman five days post-rupture of a cerebral aneurysm (World Federation of Neurological Surgeons Grade 4 and Fisher Grade 3). She is intubated for airway protection and mild hypoxemia related to an aspiration event at the time of aneurysm rupture, but is breathing spontaneously on the ventilator. Your patient is spontaneously hyperventilating with high tidal volumes despite minimal support and has developed significant hypocapnia. She has not yet developed the acute respiratory distress syndrome. You debate whether to tightly control her partial pressure of arterial carbon dioxide, weighing the known risks of acute hypocapnia in other forms of brain injury against the potential loss of clinical neuromonitoring associated with deep sedation and neuromuscular blockade in this patient who is at high risk of delayed ischemia from vasospasm. You are also aware of the potential implications of tidal volume control if this patient were to develop the acute respiratory distress syndrome and the effect of permissive hypercapnia on her intracranial pressure. In this paper we provide a detailed and balanced examination of the issues pertaining to this clinical scenario, including suggestions for clinical management of ventilation, sedation and neuromonitoring. Until more definitive clinical trial evidence is available to guide practice, clinicians are forced to carefully weigh the potential benefits of tight carbon dioxide control against the potential risks in each individual patient based on the clinical issues at hand.

Distribution of delayed ischemic neurological deficits after aneurysmal subarachnoid hemorrhage and implications for regional neuromonitoring

OBJECTIVES

Many neuromonitoring devices provide data applicable to a limited region of the brain. Risk of DIND is common after aSAH and may occur near or remote from the ruptured aneurysm. The aim of this study is to determine the distribution of DIND after aneurysms rupture as it relates to the potential value of regional monitoring in detection of vasospasm.

PATIENTS AND METHODS

The study enrolled aSAH patients presenting to a tertiary referral center over a three year period who received treatment for an identified ruptured aneurysm and survived >10 days with subsequent DIND. Only those patients receiving routine neuroimaging were included. To account for the anticipated effect on infarct distribution, patients were divided into groups of midline and non-midline aneurysms and assessed for vasospasm and stroke with respect to vascular distribution. Comparisons of clinical characteristics were made to determine factors predisposing to remote infarction.

RESULTS

Twenty-nine patients met criteria with 15 patients harboring non-midline aneurysms. The rarity of isolated remote DIND prohibited adequate assessment of predictive clinical characteristics. For non-midline aneurysms, DIND occurred ipsilateral to the ruptured aneurysm in 93% and within the same vascular territory in 86% of patients. Midline anterior circulation aneurysms frequently resulted in ACA infarction. A neuromonitoring device with 100% sensitivity for ischemia placed in the MCA territory ipsilateral to a non-midline ruptured aneurysm would identify 71% of DIND.

CONCLUSION

Vasospasm related infarction occurs most commonly ipsilateral to or in the same distribution of the ruptured aneurysm. Less anatomical correlation is seen with midline aneurysms. Rupture of posterior circulation aneurysms infrequently results in supratentorial infarction. Decisions regarding placement of regional monitors for the purpose of vasospasm detection should consider this distribution of ischemic risk.

Monitoring of the inflammatory response after aneurysmal subarachnoid haemorrhage in the clinical setting: review of literature and report of preliminary clinical experience

BACKGROUND

Clinical and experimental studies showed a marked inflammatory response in aneurysmal subarachnoid haemorrhage (SAH), and it has been proposed to play a key role in the development of cerebral vasospasm (CVS). Inflammatory response and occurrence of CVS may represent a common pathogenic pathway allowing point of care diagnostics of CVS. Therefore, monitoring of the inflammatory response might be useful in the daily clinical setting of an ICU. The aim of the current report is to give a summary about factors contributing to the complex pathophysiology of inflammatory response in SAH and to discuss possible monitoring modalities.

METHODS

Review and analysis of the existing literature and definition of own study protocols.

RESULTS

In cerebrospinal fluid, interleukin (IL)-6 has been found to be significantly higher in patients with CVS during the peri-vasospasm period. While systemic inflammatory response syndrome, high C-reactive protein levels and leukocyte counts has been linked with the occurrence of CVS, less has been reported about cytokines levels in the jugular bulb of the internal jugular vein and in the peripheral blood. Preliminary evaluation of own data suggests, that IL-6 values in the peripheral blood and the arterio-jugular differences of IL-6 are increased with the inflammatory response after SAH.

CONCLUSION

Monitoring of the inflammatory response, in particular IL-6, might be a useful tool for the daily clinical management of patients with SAH and CVS.

Arteriovenous differences of oxygen and transcranial Doppler sonography in the management of aneurysmatic subarachnoid hemorrhage

After subarachnoid hemorrhage (SAH) the detection of hemodynamically significant vasospasm is frequently difficult, especially in comatose patients. Most clinicians use transcranial Doppler sonography (TCD) to detect increasing mean blood flow velocities in the basal arteries as markers of cerebral vasospasm, without accounting for the effects of sedation and variations in blood pressure or pCO(2). This study was conducted to test the hypothesis that the arteriovenous difference of oxygen (avDO(2); in terms of % volume) could also be useful for the evaluation of vasospasm. A total of 22 SAH patients (M : F = 1 : 1.75, age 58+/-10 years, median Hunt and Hess grade 4) were prospectively enrolled. All patients were sedated with continuous doses of midazolam/fentanyl and/or propofol. TCD studies and avDO(2) measurements were conducted at the same time or in close succession. The blood flow velocity of the middle cerebral artery was recorded. A cranial CT scan was conducted if the avDO(2) increased by at least 0.8%. Overall, 82 measurements were recorded in 22 patients between days 1 and 13 after SAH. TCD mean flow velocities increased as expected. In contrast, avDO(2) decreased until post-hemorrhage day 4 before it increased again. Overall, after SAH, avDO(2) was significantly lower than in normal individuals. Cerebral infarction occurred primarily in patients with a maximal change of avDO(2) of more than 1%. TCD velocities alone are poor indicators of the severity of vasospasm. In contrast, daily avDO(2) seems to be a more robust parameter. However, collection of additional metabolic information is warranted.

Management of cerebral vasospasm

Cerebral vasospasm is delayed narrowing of the large arteries of the circle of Willis occurring 4 to 14 days after aneurysmal subarachnoid hemorrhage (SAH). It is but one cause of delayed deterioration after SAH but, in general, is the most important potentially treatable cause of morbidity and mortality after SAH. Development of vasospasm is best predicted by the volume, location, persistence and density of subarachnoid clot early after SAH. Diagnosis is made by catheter angiography or, with less accuracy, by computed tomographic angiography, transcranial Doppler ultrasound or other methods. Treatment remains problematic because it is expensive, time-consuming, associated with substantial risk and largely ineffective. Treatment includes optimization of factors that affect cerebral blood flow and metabolism, systemic administration of nimodipine, hemodynamic therapy and pharmacologic and mechanical angioplasty.