Vasospasm as the sole cause of cerebral ischemia: how strong is the evidence?

CT perfusion imaging in aneurysmal subarachnoid hemorrhage. State of the art

CT perfusion (CTP) images can be easily and rapidly obtained on all modern CT scanners and have become part of the routine imaging protocol of patients with aneurysmal subarachnoid haemorrhage (aSAH). There is a growing body of evidence supporting the use of CTP imaging in these patients, however, there are significant differences in the software packages and methods of analysing CTP. In. addition, no quantitative threshold values for tissue at risk (TAR) have been validated in this patients' population. Here we discuss the contribution of the technique in the identification of patients at risk of aSAH-related delayed cerebral ischemia (DCI) and in the assessment of the response to endovascular rescue therapy (ERT). We also address the limitations and pitfalls of automated CTP postprocessing that are specific to aSAH patients as compared to acute ischemic stroke (AIS).

Identification of Novel Cerebrospinal Fluid Biomarkers for Cognitive Decline in Aneurysmal Subarachnoid Hemorrhage: A Proteomic Approach

Background

Cognitive impairment commonly occurs in aneurysmal subarachnoid hemorrhage (aSAH) survivors. Cerebrospinal fluid (CSF) biomarkers have been proven useful in several central neurological disorders. No such diagnostic biomarkers are available for predicting cognitive impairment after aSAH to date. Here, we aimed to identify novel CSF biomarkers for cognitive deficits after aSAH using an in-depth proteomic approach.

Methods

We applied mass spectrometry with data independent acquisition (DIA) quantification to identify biomarker candidates in CSF samples from a well-characterized cohort comprising patients with impaired cognition (n = 9) and patients with intact cognition (n = 9). The potential biological processes and signaling pathways associated with differential proteins were analyzed using R software. The candidates were further validated in a larger independent cohort (n = 40) using ELISA. The diagnostic utility of these proteins was investigated by using receiver operating characteristic curve analysis.

Results

In total, we identified 628 proteins. The discovery cohort revealed that 115 proteins were differentially expressed in cognitive impairment patients compared to patients with intact cognition (P < 0.05). Independent cohort replication confirmed NCAM2, NPTXR, NRXN2, RELN, and CNTN2 as sensitive and specific candidate biomarkers for disorders of cognition. Lower CSF levels of all biomarker candidates, except RELN, were associated with more pronounced cognitive decline.

Conclusion

We identified and validated five CSF biomarkers for cognitive impairment in aSAH patients. These particular proteins have important predictive and discriminative potential for cognitive impairment in aSAH and could be potential targets for early disease intervention.

Ultrasound Perfusion Imaging for the Detection of Cerebral Hypoperfusion After Aneurysmal Subarachnoid Hemorrhage

Background

Delayed cerebral ischemia increases mortality and morbidity after aneurysmal subarachnoid hemorrhage (aSAH). Various techniques are applied to detect cerebral vasospasm and hypoperfusion. Contrast-enhanced ultrasound perfusion imaging (UPI) is able to detect cerebral hypoperfusion in acute ischemic stroke. This prospective study aimed to evaluate the use of UPI to enable detection of cerebral hypoperfusion after aSAH.

Methods

We prospectively enrolled patients with aSAH and performed UPI examinations every second day after aneurysm closure. Perfusion of the basal ganglia was outlined to normalize the perfusion records of the anterior and posterior middle cerebral artery territory. We applied various models to characterize longitudinal perfusion alterations in patients with delayed ischemic neurologic deficit (DIND) across the cohort and predict DIND by using a multilayer classification model.

Results

Between August 2013 and December 2015, we included 30 patients into this prospective study. The left–right difference of time to peak (TTP) values showed a significant increase at day 10–12. Patients with DIND demonstrated a significant, 4.86 times increase of the left–right TTP ratio compared with a mean fold change in patients without DIND of 0.9 times (p = 0.032).

Conclusions

UPI is feasible to enable detection of cerebral tissue hypoperfusion after aSAH, and the left–right difference of TTP values is the most indicative result of this finding.

Aspirin versus anticoagulation for stroke prophylaxis in blunt cerebrovascular injury: a propensity-matched retrospective cohort study

OBJECTIVE

The goal of this study was to compare the odds of stroke 24 hours or more after hospital arrival among patients with blunt cerebrovascular injury (BCVI) who were treated with therapeutic anticoagulation versus aspirin.

METHODS

The authors conducted a retrospective cohort study at a regional level I trauma center including all patients with BCVI who were treated over a span of 10 years. Individuals with stroke on arrival or within the first 24 hours were excluded, as were those receiving alternative antithrombotic drugs or procedural treatment. Exact logistic regression was used to examine the association between treatment and stroke, adjusting for injury grade. To account for the possibility of residual confounding, propensity scores for the likelihood of receiving anticoagulation were determined and used to match patients from each treatment group; the difference in the probability of stroke between the two groups was then calculated.

RESULTS

A total of 677 patients with BCVI receiving aspirin or anticoagulation were identified. A total of 3.8% (n = 23) of 600 patients treated with aspirin sustained a stroke, compared to 11.7% (n = 9) of 77 receiving anticoagulation. After adjusting for injury grade with exact regression, anticoagulation was associated with higher likelihood of stroke (OR 3.01, 95% CI 1.00-8.21). In the propensity-matched analysis, patients who received anticoagulation had a 15.0% (95% CI 3.7%-26.3%) higher probability of sustaining a stroke compared to those receiving aspirin.

CONCLUSIONS

Therapeutic anticoagulation may be inferior to aspirin for stroke prevention in BCVI. Prospective research is warranted to definitively compare these treatment strategies.

Cerebral Autoregulation in Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a devastating stroke subtype with a high rate of mortality and morbidity. The poor clinical outcome can be attributed to the biphasic course of the disease: even if the patient survives the initial bleeding emergency, delayed cerebral ischemia (DCI) frequently follows within 2 weeks time and levies additional serious brain injury. Current therapeutic interventions do not specifically target the microvascular dysfunction underlying the ischemic event and as a consequence, provide only modest improvement in clinical outcome. SAH perturbs an extensive number of microvascular processes, including the “automated” control of cerebral perfusion, termed “cerebral autoregulation.” Recent evidence suggests that disrupted cerebral autoregulation is an important aspect of SAH-induced brain injury. This review presents the key clinical aspects of cerebral autoregulation and its disruption in SAH: it provides a mechanistic overview of cerebral autoregulation, describes current clinical methods for measuring autoregulation in SAH patients and reviews current and emerging therapeutic options for SAH patients. Recent advancements should fuel optimism that microvascular dysfunction and cerebral autoregulation can be rectified in SAH patients.

Intravenous milrinone for treatment of delayed cerebral ischaemia following subarachnoid haemorrhage: a pooled systematic review

Small trials have demonstrated promising results utilising intravenous milrinone for the treatment of delayed cerebral ischaemia (DCI) after subarachnoid haemorrhage (SAH). Here we summarise and contextualise the literature and discuss the future directions of intravenous milrinone for DCI. A systematic, pooled analysis of literature was performed in accordance with the PRISMA statement. Methodological rigour was analysed using the MINORS criteria. Extracted data included patient population; treatment protocol; and clinical, radiological, and functional outcome. The primary outcome was clinical resolution of DCI. Eight hundred eighteen patients from 10 single-centre, observational studies were identified. Half (n = 5) of the studies were prospective and all were at high risk of bias. Mean age was 52 years, and females (69%) outnumbered males. There was a similar proportion of low-grade (WFNS 1-2) (49.7%) and high-grade (WFNS 3-5) (50.3%) SAH. Intravenous milrinone was administered to 523/818 (63.9%) participants. Clinical resolution of DCI was achieved in 375/424 (88%), with similar rates demonstrated with intravenous (291/330, 88%) and combined intra-arterial-intravenous (84/94, 89%) therapy. Angiographic response was seen in 165/234 (71%) receiving intravenous milrinone. Hypotension (70/303, 23%) and hypokalaemia (31/287, 11%) were common drug effects. Four cases (0.5%) of drug intolerance occurred. Good functional outcome was achieved in 271/364 (74%) patients. Cerebral infarction attributable to DCI occurred in 47/250 (19%), with lower rates in asymptomatic spasm. Intravenous milrinone is a safe and feasible therapy for DCI. A signal for efficacy is demonstrated in small, low-quality trials. Future research should endeavour to establish the optimal protocol and dose, prior to a phase-3 study.

Transcranial Doppler ultrasonography in neurological surgery and neurocritical care

Transcranial Doppler (TCD) ultrasonography is an inexpensive, noninvasive means of measuring blood flow within the arteries of the brain. In this review, the authors outline the technology underlying TCD ultrasonography and describe its uses in patients with neurosurgical diseases. One of the most common uses of TCD ultrasonography is monitoring for vasospasm following subarachnoid hemorrhage. In this setting, elevated blood flow velocities serve as a proxy for vasospasm and can herald the onset of ischemia. TCD ultrasonography is also useful in the evaluation and management of occlusive cerebrovascular disease. Monitoring for microembolic signals enables stratification of stroke risk due to carotid stenosis and can also be used to clarify stroke etiology. TCD ultrasonography can identify patients with exhausted cerebrovascular reserve, and after extracranial-intracranial bypass procedures it can be used to assess adequacy of flow through the graft. Finally, assessment of cerebral autoregulation can be performed using TCD ultrasonography, providing data important to the management of patients with severe traumatic brain injury. As the clinical applications of TCD ultrasonography have expanded over time, so has their importance in the management of neurosurgical patients. Familiarity with this diagnostic tool is crucial for the modern neurological surgeon.

Cerebral Vasospasm After Spontaneous Subarachnoid Hemorrhage: Angiographic Pattern and Its Impact on the Clinical Course

OBJECTIVE

To analyze angiographic characteristics of cerebral vasospasm (CVS) after spontaneous subarachnoid hemorrhage (sSAH) and their potential impact on secondary infarction and functional outcome.

METHODS

Demographic, clinical, and imaging data of sSAH patients with angiographic CVS admitted over a 6-year period were retrospectively analyzed.

RESULTS

A total of 85 patients were included in the final analysis. A total of 311 arterial territories in 85 angiographies demonstrated angiographic CVS. The anterior cerebral artery (ACA) was the most common site of angiographic CVS (42.1%), followed by the middle cerebral artery (MCA) (26.7%). In 29 angiographies (34%) CVS was found in more than 3 vessels and a bilateral pattern was identified in 53 cases (62%). Older age (OR 3.24 [95% CI 1.30-8.07], P = 0.012) was identified as the only significant risk factor for CVS-related infarction (OR 22.67, P = 0.015). Unfavorable outcome was associated with older age (OR 3.24, P = 0.023) and poor World Federation of Neurosurgical Societies grade (OR 3.64, P = 0.015). Analyses of angiographic characteristics did not reveal any risk factors for unfavorable outcome. We identified distal CVS as a significant risk factor for CVS-related infarction (OR 2.89, P = 0.026).

CONCLUSIONS

Angiographic CVS after sSAH shows a specific distribution pattern in favor of ACA and MCA and in most cases 2-3 affected vessels are affected, often bilaterally. Patients exhibiting distal CVS have a higher risk for CVS-related infarction and should be observed closely. Nonetheless, the majority of angiographic characteristics did not allow conclusions about functional outcome nor the occurrence of CVS-related infarction in sSAH patients.

Continuous infusion of low-dose unfractionated heparin after aneurysmal subarachnoid hemorrhage: a preliminary study of cognitive outcomes

OBJECTIVE

Cognitive dysfunction occurs in up to 70% of aneurysmal subarachnoid hemorrhage (aSAH) survivors. Low-dose intravenous heparin (LDIVH) infusion using the Maryland protocol was recently shown to reduce clinical vasospasm and vasospasm-related infarction. In this study, the Montreal Cognitive Assessment (MoCA) was used to evaluate cognitive changes in aSAH patients treated with the Maryland LDIVH protocol compared with controls.

METHODS

A retrospective analysis of all patients treated for aSAH between July 2009 and April 2014 was conducted. Beginning in 2012, aSAH patients were treated with LDIVH in the postprocedural period. The MoCA was administered to all aSAH survivors prospectively during routine follow-up visits, at least 3 months after aSAH, by trained staff blinded to treatment status. Mean MoCA scores were compared between groups, and regression analyses were performed for relevant factors.

RESULTS

No significant differences in baseline characteristics were observed between groups. The mean MoCA score for the LDIVH group (n = 25) was 26.4 compared with 22.7 in controls (n = 22) (p = 0.013). Serious cognitive impairment (MoCA ≤ 20) was observed in 32% of controls compared with 0% in the LDIVH group (p = 0.008). Linear regression analysis demonstrated that only LDIVH was associated with a positive influence on MoCA scores (β = 3.68, p =0.019), whereas anterior communicating artery aneurysms and fevers were negatively associated with MoCA scores. Multivariable linear regression analysis resulted in all 3 factors maintaining significance. There were no treatment complications.

CONCLUSIONS

This preliminary study suggests that the Maryland LDIVH protocol may improve cognitive outcomes in aSAH patients. A randomized controlled trial is needed to determine the safety and potential benefit of unfractionated heparin in aSAH patients.

Impaired microcirculation after subarachnoid hemorrhage in an in vivo animal model

The influence of aneurysmal subarachnoid hemorrhage (SAH) on brain microcirculation has not yet been systematically investigated. We established an animal model to examine (1) the brain surface microcirculation (2) the influences of cerebrospinal fluid (CSF) from aneurysmal SAH on the brain surface microcirculation. A rat SAH model was induced by injection of autologous arterial blood into the cisterna magnum, and the brain surface microcirculation was evaluated by a capillary videoscope with craniotomy at the fronto-parietal region. CSF from SAH rats and SAH patients was applied on the brain surface of naïve rats to assess the resulting microcirculatory changes. In the SAH rats, diffuse constriction of cortical arterioles within 24 hours of SAH was observed. Similar patterns of microcirculation impairment were induced on normal rat brain surfaces via application of CSF from SAH rats and SAH patients. Furthermore, the proportion of subjects with arteriolar vasoconstriction was significantly higher in the group of SAH patients with delayed ischemic neurological deficits (DIND) than in those without DIND (p < 0.001). This study demonstrated impaired microcirculation on brain surface arterioles in a rat model of SAH. CSF from SAH rats and patients was responsible for impairment of brain surface microcirculation.

The Effects of Red Blood Cell Transfusion on Functional Outcome after Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

The optimal red blood cell transfusion (RBCT) trigger for patients with aneurysmal subarachnoid hemorrhage (SAH) is unknown. In patients with cerebral vasospasm, anemia may increase susceptibility to ischemic injury; conversely, RBCT may worsen outcome given known deleterious effects.

OBJECTIVE

To examine the association between RBCT, delayed cerebral ischemia (DCI), vasospasm, and outcome after SAH.

METHODS

A total of 421 consecutive patients with SAH, admitted to a neurocritical care unit at a university-affiliated hospital and who underwent surgical occlusion of their ruptured aneurysm were retrospectively identified from a prospective observational database. Propensity score methods were used to reduce the bias associated with treatment selection.

RESULTS

Two hundred and sixty-one patients (62.0%) received an RBCT. Angiographic vasospasm (odds ratio [OR] 1.6; 95% confidence interval [CI], 1.1-2.3; P = 0.025) but not severe angiographic spasm, DCI, or delayed infarction was associated with RBCT. A total of 283 patients (67.2%) experienced a favorable outcome, defined as good or moderately disabled on the Glasgow Outcome Scale; 47 (11.2%) were severely disabled or vegetative and 91 patients (21.6%) were dead at 6-month follow-up. Among patients who survived ≥2 days, RBCT was associated with unfavorable outcome (OR, 2.6; 95% CI, 1.6-4.1). Transfusion of ≥3 units of blood was associated with an increased incidence of unfavorable outcome. Propensity analysis to control for the probability of exposure to RBCT conditional on observed covariates measured before RBCT indicates that RBCT is associated with unfavorable outcome in the absence of DCI (OR, 2.17; 95% CI, 1.56-3.01; P < 0.0001) but not when DCI is present (OR, 0.82; 95% CI, 0.35-1.92; P = 0.65).

CONCLUSIONS

Blood transfusions are associated with unfavorable outcome after SAH particularly when DCI is absent. Propensity analysis suggests that RBCT may be associated with poor outcome rather than being a marker of disease severity. However, when DCI is present, RBCT may help improve outcome.

Neutrophil depletion after subarachnoid hemorrhage improves memory via NMDA receptors

Cognitive deficits after aneurysmal subarachnoid hemorrhage (SAH) are common and disabling. Patients who experience delayed deterioration associated with vasospasm are likely to have cognitive deficits, particularly problems with executive function, verbal and spatial memory. Here, we report neurophysiological and pathological mechanisms underlying behavioral deficits in a murine model of SAH. On tests of spatial memory, animals with SAH performed worse than sham animals in the first week and one month after SAH suggesting a prolonged injury. Between three and six days after experimental hemorrhage, mice demonstrated loss of late long-term potentiation (L-LTP) due to dysfunction of the NMDA receptor. Suppression of innate immune cell activation prevents delayed vasospasm after murine SAH. We therefore explored the role of neutrophil-mediated innate inflammation on memory deficits after SAH. Depletion of neutrophils three days after SAH mitigates tissue inflammation, reverses cerebral vasoconstriction in the middle cerebral artery, and rescues L-LTP dysfunction at day 6. Spatial memory deficits in both the short and long-term are improved and associated with a shift of NMDA receptor subunit composition toward a memory sparing phenotype. This work supports further investigating suppression of innate immunity after SAH as a target for preventative therapies in SAH.

Pathophysiologic differences in cerebral autoregulation after subarachnoid hemorrhage

OBJECTIVE

To understand the physiologic basis of impaired cerebral autoregulation in subarachnoid hemorrhage (SAH) and its relationship to neurologic outcomes.

METHODS

The cohort included 121 patients with nontraumatic SAH admitted to a neurointensive critical care unit from March 2010 to May 2015. Vasospasm was ascertained from digital subtraction angiography and delayed cerebral ischemia (DCI) was defined as new cerebral infarction on high-resolution CT. Cerebral blood flow and beat-by-beat pressure were recorded daily on days 2-4 after admission. Autoregulatory capacity was quantified from pressure flow relation via projection pursuit regression. The main outcome was early alterations in autoregulatory mechanisms as they relate to vasospasm and DCI.

RESULTS

Forty-three patients developed only vasospasm, 9 only DCI, and 14 both. Autoregulatory capacity correctly predicted DCI in 86% of training cohort patients, generalizing to 80% of the patients who were not included in the original model. Patients who developed DCI had a distinct autoregulatory profile compared to patients who did not develop secondary complications or those who developed only vasospasm. The rate of decrease in flow was significantly steeper in response to transient reductions in pressure. The rate of increase in flow was markedly lower, suggesting a diminished ability to increase flow despite transient increases in pressure.

CONCLUSIONS

The extent and nature of impairment in autoregulation accurately predicts neurologic complications on an individual patient level, and suggests potentially differential impairments in underlying physiologic mechanisms. A better understanding of these can lead to targeted interventions to mitigate neurologic morbidity.

Towards use of MRI-guided ultrasound for treating cerebral vasospasm

Cerebral vasospasm is a major cause of morbidity and mortality in patients with subarachnoid hemorrhage (SAH), causing delayed neurological deficits in as many as one third of cases. Existing therapy targets induction of cerebral vasodilation through use of various drugs and mechanical means, with a range of observed efficacy. Here, we perform a literature review supporting our hypothesis that transcranially delivered ultrasound may have the ability to induce therapeutic cerebral vasodilation and, thus, may one day be used therapeutically in the context of SAH. Prior studies demonstrate that ultrasound can induce vasodilation in both normal and vasoconstricted blood vessels in peripheral tissues, leading to reduced ischemia and cell damage. Among the proposed mechanisms is alteration of several nitric oxide (NO) pathways, where NO is a known vasodilator. While in vivo studies do not point to a specific physical mechanism, results of in vitro studies favor cavitation induction by ultrasound, where the associated shear stresses likely induce NO production. Two papers discussed the effects of ultrasound on the cerebral vasculature. One study applied clinical transcranial Doppler ultrasound to a rodent complete middle cerebral artery occlusion model and found reduced infarct size. A second involved the application of pulsed ultrasound in vitro to murine brain endothelial cells and showed production of a variety of vasodilatory chemicals, including by-products of arachidonic acid metabolism. In sum, nine reviewed studies demonstrated evidence of either cerebrovascular dilation or elaboration of vasodilatory compounds. Of particular interest, all of the reviewed studies used ultrasound capable of transcranial application: pulsed ultrasound, with carrier frequencies ranging between 0.5 and 2.0 MHz, and intensities not substantially above FDA-approved intensity values. We close by discussing potential specific treatment paradigms of SAH and other cerebral ischemic disorders based on MRI-guided transcranial ultrasound.

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.

Value of transcranial Doppler, perfusion-CT and neurological evaluation to forecast secondary ischemia after aneurysmal SAH

INTRODUCTION

This study was conducted to prospectively evaluate the diagnostic value of detailed neurological evaluation, transcranial Doppler sonography (TCD) and Perfusion-CT (PCT) to predict delayed vasospasm (DV) and delayed cerebral infarction (DCI) within the following 3 days in patients with aneurysmal subarachnoid hemorrhage (SAH).

METHODS

A total of 61 patients with aneurysmal SAH were included in the study. All patients were amenable for neurological evaluation throughout the critical phase to develop secondary ischemia after SAH. The neurological status was assessed three times a day according to a detailed examination protocol. Mean flow velocities (MFV) in intracranial vessel trunks were measured daily by TCD. Native CT and PCT were routinely acquired at 3-day intervals and, in addition, whenever it was thought to be of diagnostic relevance. The predictive values of abnormal PCT and accelerations in TCD (MFV > 140 cm/s) to detect angiographic DV and DCI within the following 2 days were calculated and compared to the predictive value of delayed ischemic neurological deficits (DIND).

RESULTS

The accuracy of TCD and PCT to predict DV or DCI was 0.65 and 0.63, respectively. In comparison, DIND predicted DV or DCI with an accuracy of 0.96. Pathological PCT findings had a higher sensitivity (0.93) and negative predictive value (0.98) than TCD (0.81 and 0.96).

CONCLUSION

Neurological assessment at close intervals is the most accurate parameter to detect DV and DCI in the following 3 days. However, DIND may not be reversible. The routine acquisition of PCT in addition to daily TCD examinations seems reasonable, particularly in patients who are not amenable to a detailed neurological examination since it has a higher sensitivity and negative predictive value than TCD and leaves a lower number of undetected cases of vasospasm and infarction.

Mechanisms, treatment and prevention of cellular injury and death from delayed events after aneurysmal subarachnoid hemorrhage

INTRODUCTION

Subarachnoid hemorrhage (SAH) patients often develop brain injury as a result of a number of delayed complications, resulting in significant morbidity and mortality. Many of these complications arise due to delayed cerebral ischemia, which occurs secondary to the hemorrhage.

AREAS COVERED

The mechanisms of the delayed injury are reviewed, including angiographic vasospasm, cortical spreading ischemia, small arteriolar constriction, microthromboemboli, free radical injury and inflammation. Some current and prospective therapies for SAH are discussed, in the context of these complications. Statins have been particularly promising in experimental studies.

EXPERT OPINION

Multiple mechanisms are involved in the pathogenesis of the delayed insult after SAH. New drugs may need to target multiple pathways to injury. Trials aiming to treat complications after SAH could benefit from taking into account the multifactorial pathogenesis of delayed insults.

Low-dose intravenous heparin infusion in patients with aneurysmal subarachnoid hemorrhage: a preliminary assessment

OBJECT

Aneurysmal subarachnoid hemorrhage (aSAH) predisposes to delayed neurological deficits, including stroke and cognitive and neuropsychological abnormalities. Heparin is a pleiotropic drug that antagonizes many of the pathophysiological mechanisms implicated in secondary brain injury after aSAH.

METHODS

The authors performed a retrospective analysis in 86 consecutive patients with Fisher Grade 3 aSAH due to rupture of a supratentorial aneurysm who presented within 36 hours and were treated by surgical clipping within 48 hours of their ictus. Forty-three patients were managed postoperatively with a low-dose intravenous heparin infusion (Maryland low-dose intravenous heparin infusion protocol: 8 U/kg/hr progressing over 36 hours to 10 U/kg/hr) beginning 12 hours after surgery and continuing until Day 14 after the ictus. Forty-three control patients received conventional subcutaneous heparin twice daily as deep vein thrombosis prophylaxis.

RESULTS

Patients in the 2 groups were balanced in terms of baseline characteristics. In the heparin group, activated partial thromboplastin times were normal to mildly elevated; no clinically significant hemorrhages or instances of heparin-induced thrombocytopenia or deep vein thrombosis were encountered. In the control group, the incidence of clinical vasospasm requiring rescue therapy (induced hypertension, selective intraarterial verapamil, and angioplasty) was 20 (47%) of 43 patients, and 9 (21%) of 43 patients experienced a delayed infarct on CT scanning. In the heparin group, the incidence of clinical vasospasm requiring rescue therapy was 9% (4 of 43, p = 0.0002), and no patient suffered a delayed infarct (p = 0.003).

CONCLUSIONS

In patients with Fisher Grade 3 aSAH whose aneurysm is secured, postprocedure use of a low-dose intravenous heparin infusion may be safe and beneficial.

Metabolic changes in patients with aneurysmal subarachnoid hemorrhage apart from perfusion deficits: neuronal mitochondrial injury?

BACKGROUND AND PURPOSE

Neuronal damage in aSAH apart from perfusion deficits has been widely discussed. We aimed to test if cerebral injury occurs in aSAH independently from visible perfusion deficit by measuring cerebral metabolites in patients with aSAH without infarction or impaired perfusion.

MATERIALS AND METHODS

We performed 3T MR imaging including (1)H-MR spectroscopy, DWI, and MR perfusion in 58 patients with aSAH and 11 age-matched and sex-matched control patients with incidental aneurysm. We compared changes of NAA, Cho, Glx, Lac, and Cr between all patients with aSAH and controls, between patients with and without visible perfusion deficit or infarction and controls, and between patients with and without visible perfusion deficit or infarction by using the Wilcoxon signed-rank test.

RESULTS

We found that NAA significantly (P < .005) decreased in all patients with aSAH. Cho was significantly increased in all patients compared with controls (P < .05). In patients without impaired perfusion or infarction, Glx was significantly decreased compared with both controls (P = .005) and patients with impaired perfusion or infarction (P = .006).

CONCLUSIONS

The significant decrease of NAA and Glx in patients with aSAH but without impaired perfusion or infarction strongly suggests global metabolic changes independent from visible perfusion deficits that might reflect neuronal mitochondrial injury. Further, impaired perfusion in aSAH seems to induce additional metabolic changes from increasing neuronal stress that might, to some extent, mask the global metabolic changes.

Dynamic change in cerebral microcirculation and focal cerebral metabolism in experimental subarachnoid hemorrhage in rabbits

Regional cerebral blood flow (rCBF) in the cerebral metabolism and energy metabolism measurements can be used to assess blood flow of brain cells and to detect cell activity. Changes of rCBF in the cerebral microcirculation and energy metabolism were determined in an experimental model of subarachnoid hemorrhage (SAH) model in 56 large-eared Japanese rabbits about 12 to 16-month old. Laser Doppler flowmetry was used to detect the blood supply to brain cells. Internal carotid artery and vein blood samples were used for duplicate blood gas analysis to assess the energy metabolism of brain cells. Cerebral blood flow (CBF) was detected by single photon emission computed tomography (SPECT) perfusion imaging using Tc-99m ethyl cysteinate dimer (Tc-99m ECD) as an imaging reagent. The percentage of injected dose per gram of brain tissue was calculated and analyzed. There were positive correlations between the percentage of radionuclide injected per gram of brain tissue and rCBF supply and cerebral metabolic rate for oxygen (P < 0.05). However, there was a negative correlation between radioactivity counts per unit volume detected on the SPECT rheoencephalogram and lactic acid concentration in the homolateral internal carotid artery and vein. In summary, this study found abnormal CBF in metabolism and utilization of brain cells after SAH, and also found that deterioration of energy metabolism of brain cells played a significant role in the development of SAH. There are matched reductions in CBF and metabolism. Thus, SPECT imaging could be used as a noninvasive method to detect CBF.

Low-dose lipopolysaccharide injection prior to subarachnoid hemorrhage modulates Delayed Deterioration associated with vasospasm in subarachnoid hemorrhage

There is increasing evidence that inflammation plays a role in the development of Delayed Deterioration associated with vasospasm (DDAV) after subarachnoid hemorrhage (SAH). Lipopolysaccharide (LPS) is an activator of the innate inflammatory system that causes DDAV in animal models. The effect of low-dose LPS has been shown to be protective in stroke models but has not been investigated in SAH. Two treatments were studied: (1) a single intraperitoneal dose of 0.6 mg/kg injected 24 h prior to SAH and (2) four daily doses administered prior to SAH. DDAV was determined by India ink angiography at day 6; behavioral testing was done in a different cohort of animals, and analysis of brain chemokine levels was accomplished by dot blot. Vessel caliber was improved compared to the SAH group in the single-injection group (ldLPS ×1) (p < 0.05). In the multiple-injection group (ldLPS ×4), the vessel caliber was similar to SAH (p < 0.05). ldLPS ×1 improved performance on the Barnes maze test, whereas the ldLPS ×4 was worse (p < 0.001). Brain levels of the inflammatory chemokine KC (keratinocyte-derived chemokine) were decreased in the ldLPS ×1 and increased in the ldLPS ×4 group. Single-injection low-dose LPS preconditioning was protective for delayed deterioration associated with vasospasm (DDAV), whereas the multiple-injection course exacerbated DDAV. This further supports that inflammation plays an important role in the development of DDAV, and that modulating the inflammatory system may be a potential target for future therapies in SAH.

Inflammation in subarachnoid hemorrhage and delayed deterioration associated with vasospasm: a review

Delayed deterioration associated with vasospasm (DDAV) after subarachnoid hemorrhage (SAH), (often called vasospasm) continues to be both a difficult entity to treat and a leading cause of morbidity in patients. Until recently, attention was focused on alleviating the vascular spasm. Recent evidence shows that vascular spasm may not account for all the morbidity of DDAV. There is renewed interest in looking for other potential targets for therapy. Inflammation has become a promising area of research for new treatments. This review explores the evidence that inflammation is a driver of DDAV by asking three questions: (1) If inflammation is important in the pathogenesis of the disease, what part or parts of the inflammatory response are involved? (2) When does inflammation occur in SAH? (3) In what compartment of the skull does the inflammation occur, the cerebrospinal fluid and meninges, the cerebral arteries, or the brain itself?

Value of Perfusion CT, Transcranial Doppler Sonography, and Neurological Examination to Detect Delayed Vasospasm after Aneurysmal Subarachnoid Hemorrhage

Background. If detected in time, delayed cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH) may be treated by balloon angioplasty or chemical vasospasmolysis in order to enhance cerebral blood flow (CBF) and protect the brain from ischemic damage. This study was conceived to compare the diagnostic accuracy of detailed neurological examination, Transcranial Doppler Sonography (TCD), and Perfusion-CT (PCT) to detect angiographic vasospasm. Methods. The sensitivity, specificity, positive and negative predictive values of delayed ischemic neurological deterioration (DIND), pathological findings on PCT-maps, and accelerations of the mean flow velocity (MVF) were calculated. Results. The accuracy of DIND to predict angiographic vasospasm was 0.88. An acceleration of MFV in TCD (>140 cm/s) had an accuracy of 0.64, positive PCT-findings of 0.69 with a higher sensitivity, and negative predictive value than TCD. Interpretation. Neurological assessment at close intervals is the most sensitive and specific parameter for cerebral vasospasm. PCT has a higher accuracy, sensitivity and negative predictive value than TCD. If detailed neurological evaluation is possible, it should be the leading parameter in the management and treatment decisions. If patients are not amenable to detailed neurological examination, PCT at regular intervals is a helpful tool to diagnose secondary vasospasm after aneurysmal SAH.

Inflammation as a predictor for delayed cerebral ischemia after aneurysmal subarachnoid haemorrhage

BACKGROUND

The mechanism of development of delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (SAH) is poorly understood. Inflammatory processes are implicated in the development of ischemic stroke and may also predispose to the development of DCI following SAH. The objective of this study was to test whether concentrations of circulating inflammatory markers (C-reactive protein (CRP), interleukin-6 (IL-6) and interleukin 1 receptor antagonist (IL-1Ra)) were predictive for DCI following SAH. Secondary analyses considered white cell count (WCC) and erythrocyte sedimentation rate (ESR).

METHODS

This was a single-center case-control study nested within a prospective cohort. Plasma inflammatory markers were measured in patients up to 15 days after SAH (initial, peak, average, final and rate of change to final). Cases were defined as those developing DCI. Inflammatory markers were compared between cases and randomly selected matched controls.

RESULTS

Among the 179 participants there were 46 cases of DCI (26%). In primary analyses the rate of change of IL-6 was associated with DCI (OR 2.3 (95% CI 1.1 to 5.0); p=0.03). The final value and rate of change of WCC were associated with DCI (OR 1.2 (95% CI 1.0 to 1.3) and OR 1.3 (95% CI 1.0 to 1.6), respectively). High values of ESR were associated with DCI (OR 2.4 (95% CI 1.3 to 4.6) initial; OR 2.3 (95% CI 1.3 to 4.2) average; OR 2.1 (95% CI 1.1 to 3.9) peak; and OR 2.0 (95% CI 1.2 to 3.3) final value).

CONCLUSIONS

Leucocytosis and change in IL-6 prior to DCI reflect impending cerebral ischemia. The time-independent association of ESR with DCI after SAH may identify this as a risk factor. These data suggest that systemic inflammatory mechanisms may increase the susceptibility to the development of DCI after SAH.

Systemic administration of LPS worsens delayed deterioration associated with vasospasm after subarachnoid hemorrhage through a myeloid cell-dependent mechanism

BACKGROUND

Delayed deterioration associated with vasospasm (DDAV) after aneurismal subarachnoid hemorrhage (SAH) is a major cause of morbidity. We have previously shown that myeloid cell depletion before experimental SAH in a murine model ameliorates DDAV. In this study, we address whether systemic administration of lipopolysaccharide (LPS) worsens DDAV in a myeloid cell-dependent fashion.

METHODS

We challenged mice in our experimental SAH model with LPS before hemorrhage and evaluated the degree of vasospasm on day 6 with India ink angiography; behavioral deficits by rotorod, Y-maze, and Barnes maze testing; microglial activation early after SAH by immunohistochemistry; and the brain levels of the chemokines CCL5 and KC at the time of vasospasm. Another group of animals were given the myeloid cell-depleting antibody against the neutrophil antigen Ly6G/C prior to LPS administration and SAH.

RESULTS

LPS followed by SAH significantly worsens angiographic vasospasm as well as performance on the Barnes maze but not the Y-maze or rotorod tests. There was an increased activation of microglia in animals with LPS before SAH compared to SAH alone. Depletion of myeloid cells before LPS administration inhibited the development of vasospasm, improved the performance on behavioral tests, and reduced microglial activation. The chemokines CCL5 and KC were incrementally elevated in SAH and LPS SAH, but suppressed in animals with myeloid cell depletion.

CONCLUSIONS

LPS administration before SAH worsens DDAV through a myeloid cell-dependent mechanism supporting studies in humans which show that systemic inflammation increases the likelihood of developing DDAV.

Clinical significance of impaired cerebrovascular autoregulation after severe aneurysmal subarachnoid hemorrhage

BACKGROUND AND PURPOSE

The purpose of this study was to investigate the relationship between cerebrovascular autoregulation and outcome after aneurysmal subarachnoid hemorrhage.

METHODS

In a prospective observational study, 80 patients after severe subarachnoid hemorrhage were continuously monitored for cerebral perfusion pressure and partial pressure of brain tissue oxygen for an average of 7.9 days (range, 1.9-14.9 days). Autoregulation was assessed using the index of brain tissue oxygen pressure reactivity (ORx), a moving correlation coefficient between cerebral perfusion pressure and partial pressure of brain tissue oxygen. High ORx indicates impaired autoregulation; low ORx signifies intact autoregulation. Outcome was determined at 6 months and dichotomized into favorable (Glasgow Outcome Scale 4-5) and unfavorable outcome (Glasgow Outcome Scale 1-3).

RESULTS

Twenty-four patients had a favorable and 56 an unfavorable outcome. In a univariate analysis, there were significant differences in autoregulation (ORx 0.19±0.10 versus 0.37±0.11, P<0.001, for favorable versus unfavorable outcome, respectively), age (44.1±11.0 years versus 54.2±12.1 years, P=0.001), occurrence of delayed cerebral infarction (8% versus 46%, P<0.001), use of coiling (25% versus 54%, P=0.02), partial pressure of brain tissue oxygen (24.9±6.6 mm Hg versus 21.8±6.3 mm Hg, P=0.048), and Fisher grade (P=0.03). In a multivariate analysis, ORx (P<0.001) and age (P=0.003) retained an independent predictive value for outcome. ORx correlated with Glasgow Outcome Scale (r=-0.70, P<0.001).

CONCLUSIONS

The status of cerebrovascular autoregulation might be an important pathophysiological factor in the disease process after subarachnoid hemorrhage, because impaired autoregulation was independently associated with an unfavorable outcome.

The importance of early brain injury after subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a medical emergency that accounts for 5% of all stroke cases. Individuals affected are typically in the prime of their lives (mean age 50 years). Approximately 12% of patients die before receiving medical attention, 33% within 48 h and 50% within 30 days of aSAH. Of the survivors 50% suffer from permanent disability with an estimated lifetime cost more than double that of an ischemic stroke. Traditionally, spasm that develops in large cerebral arteries 3-7 days after aneurysm rupture is considered the most important determinant of brain injury and outcome after aSAH. However, recent studies show that prevention of delayed vasospasm does not improve outcome in aSAH patients. This finding has finally brought in focus the influence of early brain injury on outcome of aSAH. A substantial amount of evidence indicates that brain injury begins at the aneurysm rupture, evolves with time and plays an important role in patients' outcome. In this manuscript we review early brain injury after aSAH. Due to the early nature, most of the information on this injury comes from animals and few only from autopsy of patients who died within days after aSAH. Consequently, we began with a review of animal models of early brain injury, next we review the mechanisms of brain injury according to the sequence of their temporal appearance and finally we discuss the failure of clinical translation of therapies successful in animal models of aSAH.

From vasospasm to early brain injury: new frontiers in subarachnoid haemorrhage research

INTRODUCTION

Delayed vasospasm has traditionally been considered the most important determinant of poor outcome after subarachnoid haemorrhage (SAH). Consequently, most of the research and therapies are directed towards reducing the incidence of vasospasm (VSP). To date, however, clinical trials based on this strategy have not delivered a definitive treatment for preventing or reducing brain injury after SAH. This fact has caused a paradigm shift in research, which now focuses on early brain injury (EBI) occurring in the first 72 hours after SAH. It has also changed the idea of VSP's role in brain damage, and suggests the need for re-evaluating the pathophysiological process of SAH.

DEVELOPMENT

This review examines the current state of knowledge on the pathophysiological mechanisms associated with EBI and summarises the diagnostic options currently available.

CONCLUSION

It seems that the research approach needs to be changed so that investigators will focus on prevention of EBI, reduction of secondary brain complications and ultimately, the optimisation neurological outcome.

Elevated BNP is associated with vasospasm-independent cerebral infarction following aneurysmal subarachnoid hemorrhage

BACKGROUND

Elevated levels of B-type natriuretic peptide (BNP) have been associated with cardiac dysfunction and adverse neurological outcomes after subarachnoid hemorrhage (SAH). We sought to determine whether elevated levels of BNP are independently associated with radiographic cerebral infarction after SAH.

METHODS

Plasma BNP levels were measured after admission, a mean of 5.5 ± 3.0 days after SAH onset. Cerebral infarction was determined by retrospective review of computerized tomography (CT) scans. Cerebral vasospasm was confirmed by the presence of vascular narrowing on cerebral angiogram. The association between BNP and cerebral infarction was quantified using multivariable logistic regression and reverse stepwise elimination of clinical covariates. A stratified analysis was performed to quantify the association between BNP levels and infarction in patients with and without angiographic vasospasm.

RESULTS

BNP levels were measured from 119 subjects. The median BNP level was 105 pg/ml (interquartile range 37-275 pg/ml). In our multivariable model, the top quartile of BNP levels (≥ 276 pg/ml) were associated with an increased odds of cerebral infarction (OR 4.2, P = 0.009). The stratified analysis showed that the association between BNP and infarction was strongest in patients without angiographic vasospasm (OR 7.8, P = 0.006).

CONCLUSIONS

Elevated levels of BNP are strongly and independently associated with cerebral infarction, and the association is most pronounced in patients without angiographic vasospasm. These results provide further evidence that other mechanisms can contribute to infarction, and BNP may be a useful biomarker in detecting patients at risk for adverse outcomes without large vessel vasospasm.

Treatment options for cerebral vasospasm in aneurysmal subarachnoid hemorrhage

Cerebral vasospasm occurs frequently after aneurysmal subarachnoid and contributes to delayed cerebral ischemia. In this article we address systematic problems with the literature on vasospasm and then review both established and experimental treatment options.

Microthrombosis after experimental subarachnoid hemorrhage: time course and effect of red blood cell-bound thrombin-activated pro-urokinase and clazosentan

Delayed cerebral ischemia (DCI) is a significant cause of morbidity and mortality for patients surviving the rupture of an intracranial aneurysm. Despite an association between vasospasm and DCI, thrombosis and thromboembolism may also contribute to DCI. In this study we investigate the time course of intravascular microclot formation after experimental subarachnoid hemorrhage (SAH) and assess the effects of the following two drugs on microclot burden: mutant thrombin-activated urokinase-type plasminogen activator (scFv/uPA-T), which is bound to red blood cells for use as a thromboprophylactic agent, and clazosentan, an endothelin antagonist. In the first study, adult male C57BL/6 mice were sacrificed at 24 (n=5), 48 (n=6), 72 (n=8), and 96 (n=3) hours after SAH induced by filament perforation of the anterior cerebral artery. Sham animals (n=5) underwent filament insertion without puncture. In the second study, animals received scFv/uPA-T (n=5) 3 hours after hemorrhage, clazosentan (n=5) by bolus and subcutaneous pump after SAH just prior to skin closure, or a combination of scFv/uPA-T and clazosentan (n=4). Control (n=6) and sham (n=5) animals received saline alone. All animals were sacrificed at 48 hours and underwent intra-cardiac perfusion with 4% paraformaldehyde. The brains were then extracted and sliced coronally on a cryostat and processed for immunohistochemistry. An antibody recognizing thrombin-anti-thrombin complexes was used to detect microclots on coronal slices. Microclot burden was calculated for each animal and compared among groups. Following SAH, positive anti-thrombin staining was detected bilaterally in the following brain regions, in order of decreasing frequency: cortex; hippocampus; hypothalamus; basal ganglia. Few microclots were found in the shams. Microclot burden peaked at 48 hours and then decreased gradually. Animals receiving scFv/uPA-T and scFv/uPA-T+clazosentan had a lower microclot burden than controls, whereas animals receiving clazosentan alone had a higher microclot burden (p<0.005). The overall mortality rate in the time course study was 40%; mortality was highest among control animals in the second study. Intravascular microclots form in a delayed fashion after experimental SAH. Microclots may be safely reduced using a novel form of thromboprophylaxis provided by RBC-targeted scFv/uPA-T and represent a potential target for therapeutic intervention in the treatment of DCI.

Anemia and transfusion after subarachnoid hemorrhage

Delayed cerebral ischemia after subarachnoid hemorrhage (SAH) may be affected by a number of factors, including cerebral blood flow and oxygen delivery. Anemia affects about half of patients with SAH and is associated with worse outcome. Anemia also may contribute to the development of or exacerbate delayed cerebral ischemia. This review was designed to examine the prevalence and impact of anemia in patients with SAH and to evaluate the effects of transfusion. A literature search was made to identify original research on anemia and transfusion in SAH patients. A total of 27 articles were identified that addressed the effects of red blood cell transfusion (RBCT) on brain physiology, anemia in SAH, and clinical management with RBCT or erythropoietin. Most studies provided retrospectively analyzed data of very low-quality according to the GRADE criteria. While RBCT can have beneficial effects on brain physiology, RBCT may be associated with medical complications, infection, vasospasm, and poor outcome after SAH. The effects may vary with disease severity or the presence of vasospasm, but it remains unclear whether RBCTs are a marker of disease severity or a cause of worse outcome. Erythropoietin data are limited. The literature review further suggests that the results of the Transfusion Requirements in Critical Care Trial and subsequent observational studies on RBCT in general critical care do not apply to SAH patients and that randomized trials to address the role of RBCT in SAH are required.

Critical care management of subarachnoid hemorrhage

Successful critical care management of patients with aneurysmal subarachnoid hemorrhage (SAH) requires a thorough understanding of the disease and its complications and a familiarity with modern multimodality neuromonitoring technology. This article reviews the natural history of aneurysmal SAH and strategies for disease management in the acute setting, including available tools for monitoring brain function. Intensive care management of patients with SAH focuses on prevention of further neurologic injury. Aneurysmal rebleeding, hydrocephalus, seizures, and delayed ischemic injury represent major threats. There is increasing awareness of extracerebral complications, including electrolyte disturbances (eg, cerebral salt wasting) and cardiac dysfunction. Prompt recognition and treatment of these disorders maximizes the odds of a good functional outcome. Technologic advances hold the promise of improved detection and treatment of secondary neurologic insults.

[Protective measures against cerebral ischemia following subarachnoid hemorrhage: Part 1]

BACKGROUND AND OBJECTIVES

Cerebral vasospasm following aneurysmal subarachnoid hemorrhage contributes significantly to morbidity and mortality. Many studies on the various treatments aimed at preventing cerebral vasospasm have been carried out, but evidence of efficacy is limited. Our aim was to review the literature on the various therapies for which there is scientific evidence of protection against cerebral vasospasm following aneurysmal subarachnoid hemorrhage.

METHODS

MEDLINE search (1950 to the october 2009) and review of articles found on the prevention of cerebral vasospasm following aneurysmal subarachnoid hemorrhage. The search was restricted to articles in English, French, and Spanish. The keywords were cerebral vasospasm, subarachnoid hemorrhage, therapy, nimodipine, triple H, clazosentan, statins, and magnesium in addition to the word forms derived from them. We also searched manually for references cited in the selected articles. A title was included if it was a randomized controlled trial, meta-analysis, nonrandomized clinical trial, descriptive study, observational study with statistical analysis, opinion article, or expert review.

RESULTS

Part 1 analyzed treatment with calcium antagonists and triple-H therapy (hypertension, hemodilution, and hypervolemia). Part 2 analyzed new therapies such as clazosentan, magnesium, and statins. A total of 597 titles were located; 283 were initially selected. The 61 articles finally selected for review were of the following types: 2 opinion articles, 21 randomized controlled trials, 22 expert review articles, 3 meta-analyses, 4 nonrandomized clinical trials, 1 descriptive study, and 5 observational studies with statistical analysis. Three studies (2 meta-analyses and 1 randomized controlled trial) demonstrated that nimodipine use confers benefits (reduced morbidity and mortality) for patients with aneurysmatic subarachnoid hemorrhage. Statistically significant clinical benefits could not be demonstrated for the other drugs (clazosentan, statins, and magnesium).

CONCLUSIONS

Insufficient evidence is available to support the use of the triple-H therapy, clazosentan, statins, or magnesium sulfate for the prevention of cerebral vasospasm following subarachnoid hemorrhage. Nimodipine is the only preventative treatment that can be recommended.

Detection of Cerebral Compromise With Multimodality Monitoring in Patients With Subarachnoid Hemorrhage

BACKGROUND:

Studies in traumatic brain injury suggest that monitoring techniques such as brain tissue oxygen (Pbto2) and cerebral microdialysis may complement conventional intracranial pressure (ICP) and cerebral perfusion pressure (CPP) measurements.

OBJECTIVE:

In this study of poor-grade (Hunt and Hess grade IV and V) subarachnoid hemorrhage (SAH) patients, we examined the prevalence of brain hypoxia and brain energy dysfunction in the presence of normal and abnormal ICP and CPP.

METHODS:

SAH patients who underwent multimodal neuromonitoring and cerebral microdialysis were studied. We examined the frequency of brain hypoxia and energy dysfunction in different ICP and CPP ranges and the relationship between Pbto2 and the lactate/pyruvate ratio (LPR).

RESULTS:

A total of 2394 samples from 19 patients were analyzed. There were 149 samples with severe brain hypoxia (Pbto2 ≤10 mm Hg) and 347 samples with brain energy dysfunction (LPR &gt;40). The sensitivities of abnormal ICP or CPP for elevated LPR and reduced Pbto2 were poor (21.2% at best), and the LPR or Pbto2 was abnormal in many instances when ICP or CPP was normal. Severe brain hypoxia was often associated with an LPR greater than 40 (86% of samples). In contrast, mild brain hypoxia (≤20 mm Hg) and severe brain hypoxia were observed in only 53% and 36% of samples with brain energy dysfunction, respectively.

CONCLUSION:

Our data demonstrate that ICP and CPP monitoring may not always detect episodes of cerebral compromise in SAH patients. Our data suggest that several complementary monitors may be needed to optimize the care of poor-grade SAH patients.

Unfractionated heparin: multitargeted therapy for delayed neurological deficits induced by subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is associated with numerous "delayed neurological deficits" (DNDs) that have been attributed to multiple pathophysiological mechanisms, including ischemia, microthrombosis, free radical damage, inflammation, and vascular remodeling. To date, effective prophylactic therapy for SAH-induced DNDs has been elusive, due perhaps to the multiplicity of mechanisms involved that render typical, single-agent therapy seemingly futile. We hypothesized that heparin, which has multiple underappreciated salutary effects, might be useful as a multitargeted prophylactic agent against SAH-induced DNDs. We performed a comprehensive review of the literature to evaluate the potential utility of heparin in targeting the multiple pathophysiological mechanisms that have been identified as contributing to SAH-induced DNDs. Our literature review revealed that unfractionated heparin can potentially antagonize essentially all of the pathophysiological mechanisms known to be activated following SAH. Heparin binds >100 proteins, including plasma proteins, proteins released from platelets, cytokines, and chemokines. Also, heparin complexes with oxyhemoglobin, blocks the activity of free radicals including reactive oxygen species, antagonizes endothelin-mediated vasoconstriction, smooth muscle depolarization, and inflammatory, growth and fibrogenic responses. Our review suggests that the use of prophylactic heparin following SAH may warrant formal study.

Spreading depolarization: a possible new culprit in the delayed cerebral ischemia of subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is a devastating disease with a high mortality and morbidity rate. Gradual improvements have been made in the reduction of mortality rates associated with the disease during the last 30 years. However, delayed cerebral ischemia (DCI), the major delayed complication of SAH, remains a significant contributor to mortality and morbidity despite substantial research and clinical efforts. During the last several years, the predominant role of cerebral vasospasm, the long-accepted etiologic factor behind DCI, has been questioned. It is now becoming increasingly clear that the pathophysiology underlying DCI is multifactorial. Cortical spreading depression is emerging as a likely factor in this complex web of pathologic changes after SAH. Understanding its role after SAH and its relationship with the other pathologic processes such as vasospasm, microcirculatory dysfunction, and microemboli will be vital to the development of new therapeutic approaches to reduce DCI and improve the clinical outcome of the disease.

Clinical relevance of cortical spreading depression in neurological disorders: migraine, malignant stroke, subarachnoid and intracranial hemorrhage, and traumatic brain injury

Cortical spreading depression (CSD) and depolarization waves are associated with dramatic failure of brain ion homeostasis, efflux of excitatory amino acids from nerve cells, increased energy metabolism and changes in cerebral blood flow (CBF). There is strong clinical and experimental evidence to suggest that CSD is involved in the mechanism of migraine, stroke, subarachnoid hemorrhage and traumatic brain injury. The implications of these findings are widespread and suggest that intrinsic brain mechanisms have the potential to worsen the outcome of cerebrovascular episodes or brain trauma. The consequences of these intrinsic mechanisms are intimately linked to the composition of the brain extracellular microenvironment and to the level of brain perfusion and in consequence brain energy supply. This paper summarizes the evidence provided by novel invasive techniques, which implicates CSD as a pathophysiological mechanism for this group of acute neurological disorders. The findings have implications for monitoring and treatment of patients with acute brain disorders in the intensive care unit. Drawing on the large body of experimental findings from animal studies of CSD obtained during decades we suggest treatment strategies, which may be used to prevent or attenuate secondary neuronal damage in acutely injured human brain cortex caused by depolarization waves.

A review of delayed ischemic neurologic deficit following aneurysmal subarachnoid hemorrhage: historical overview, current treatment, and pathophysiology

Delayed ischemic neurologic deficit (DIND) is a serious and poorly understood complication of aneurysmal subarachnoid hemorrhage. Although advances in treatment have improved prognosis for these patients, long-term clinical outcomes remain disappointing. Historically, angiographic vasospasm was thought to result in a DIND, although an increasing body of evidence suggests that this is an oversimplification, because interventions that have effectively targeted angiographic vasospasm have not improved outcome. Consequently, the relationship between angiographic vasospasm and neurologic outcome may be associative rather than causative. Although our understanding of the underlying molecular processes and pathophysiology is improving, responsible mediators or pathways have yet to be identified. The aim of this review is to summarize the key historical events that have helped shape our understanding of the pathophysiology of this phenomenon (microcirculation, autoregulation, microthrombosis, inflammation, apoptosis, spreading depolarization, oxidative stress) and to present the evidence underlying current treatment strategies (hemodynamic therapy, oral nimodipine, endovascular therapy, statins, cerebrospinal fluid drainage, thrombolysis, magnesium) and the translational and clinical research investigating DIND.

Neuroprotection in subarachnoid hemorrhage

Despite advances in aneurysm ablation and the initial management of patients presenting with aneurysmal subarachnoid hemorrhage, delayed cerebral ischemia remains a significant source of morbidity. Traditionally, delayed cerebral ischemia was thought to be a result of vasospasm of the proximal intracranial vessels, and clinical trials have relied largely on radiographic evidence of vasospasm as a surrogate for functional outcome. However, a number of trials have demonstrated a dissociation between angiographic vasospasm and outcome, and more recent data suggest that other mechanisms of injury, such as microvascular dysfunction and complex neuronal-glial interactions, may influence the development of delayed ischemic deficit after aneurysmal subarachnoid hemorrhage. Our evolving understanding of the pathophysiology of delayed cerebral ischemia may offer the opportunity to test new therapeutic strategies in this area and improve clinical trial design.

Interaction of neurovascular protection of erythropoietin with age, sepsis, and statin therapy following aneurysmal subarachnoid hemorrhage

Object

In a previous randomized controlled trial, the authors demonstrated that acute erythropoietin (EPO) therapy reduced severe vasospasm and delayed ischemic deficits (DIDs) following aneurysmal subarachnoid hemorrhage. In this study, the authors aimed to investigate the potential interaction of neurovascular protection by EPO with age, sepsis, and concurrent statin therapy.

Methods

The clinical events of 80 adults older than 18 years and with < 72 hours of aneurysmal subarachnoid hemorrhage, who were randomized to receive 30,000 U of intravenous EPO-β or placebo every 48 hours for a total of 3 doses, were analyzed by stratification according to age (< or ≥ 60 years), sepsis, or concomitant statin therapy. End points in the trial included cerebral vasospasm and impaired autoregulation on transcranial Doppler ultrasonography, DIDs, and unfavorable outcome at discharge and at 6 months measured with the modified Rankin Scale and Glasgow Outcome Scale. Analyses were performed using the t-test and/or ANOVA for repeated measurements.

Results

Younger patients (< 60 years old) or those without sepsis obtained benefits from EPO by a reduction in vasospasm, impaired autoregulation, and unfavorable outcome at discharge. Compared with nonseptic patients taking EPO, those with sepsis taking EPO had a lower absolute reticulocyte count (nonsepsis vs sepsis, 143.5 vs. 105.8 × 109/L on Day 6; p = 0.01), suggesting sepsis impaired both hematopoiesis and neurovascular protection by EPO. In the EPO group, none of the statin users suffered DIDs (p = 0.078), implying statins may potentiate neuroprotection by EPO.

Conclusions

Erythropoietin-related neurovascular protection appears to be attenuated by old age and sepsis and enhanced by statins, an important finding for designing Phase III trials.

Genetic determinants of cerebral vasospasm, delayed cerebral ischemia, and outcome after aneurysmal subarachnoid hemorrhage

Despite extensive effort to elucidate the cellular and molecular bases for delayed cerebral injury after aneurysmal subarachnoid hemorrhage (aSAH), the pathophysiology of these events remains poorly understood. Recently, much work has focused on evaluating the genetic underpinnings of various diseases in an effort to delineate the contribution of specific molecular pathways as well as to uncover novel mechanisms. The majority of subarachnoid hemorrhage genetic research has focused on gene expression and linkage studies of these markers as they relate to the development of intracranial aneurysms and their subsequent rupture. Far less work has centered on the genetic determinants of cerebral vasospasm, the predisposition to delayed cerebral injury, and the determinants of ensuing functional outcome after aSAH. The suspected genes are diverse and encompass multiple functional systems including fibrinolysis, inflammation, vascular reactivity, and neuronal repair. To this end, we present a systematic review of 21 studies suggesting a genetic basis for clinical outcome after aSAH, with a special emphasis on the pathogenesis of cerebral vasospasm and delayed cerebral ischemia. In addition, we highlight potential pitfalls in the interpretation of genetic association studies, and call for uniformity of design of larger multicenter studies in the future.