Cerebral arterial constriction after experimental subarachnoid hemorrhage is associated with blood components within the arterial wall

Magnetic resonance analysis of deep cerebral venous vasospasm after subarachnoid hemorrhage in rabbits

Objective

Arterial spasm is proved to be an inducer of cerebral ischemia and cerebral infarction, while when a venous spasm occurs, cerebral edema is seen to be caused by a disturbance in cerebral blood flow. However, it is unclear and unproven whether venous spasm occurs after subarachnoid hemorrhage (SAH). To provide the theoretical basis for treating cerebral vasospasm after SAH, magnetic resonance imaging (MRI) was employed to observe the changes in the diameter of deep cerebral veins in rabbits after SAH.

Methods

Fourteen New Zealand rabbits were randomly divided into the SAH group (n = 10) and the normal saline group (NS group, n = 4). Specifically, the SAH models were established by the ultrasound-guided double injections of blood into cisterna magna. Moreover, the MRI was performed to observe the changes in the diameter of deep cerebral veins (internal cerebral vein, basilar vein, and great cerebral vein) and basilar artery before modeling (0 d) and 1, 3, 5, 7, 9, and 11 d after modeling.

Results

In the SAH group, the diameter of the basilar artery showed no evident change on the 1st d. However, it became narrower obviously on the 3rd d and 5th d, and the stenosis degree was more than 30%. The diameter gradually relieved from 7th to 9th d, and finally returned to normal on the 11th d. Moreover, the diameter of the internal cerebral vein significantly narrowed on the 1st d, the stenosis degree of which was 19%; the stenosis then relieved slightly on the 3rd d (13%), reached the peak (34%) on the 5th d, and gradually relieved from 7th d to 11th d. Moreover, the stenosis degree of the basilar vein was 18% on the 1st d, 24% on the 3rd d, and reached the peak (34%) on the 5th d.

Conclusion

After SAH in rabbits, the cerebral vasospasm was seen to occur in the basilar artery, and likewise, spasmodic changes took place in the deep cerebral vein. Furthermore, the time regularity of spasmodic changes between the cerebral vein and basilar artery was of significant difference, indicating that the venous vasospasm resulted in active contraction.

A Rare Case of Cerebral Vasospasm Secondary to Primary Intraventricular Hemorrhage With an Immediate Improvement in Neurological Status Following Intra-arterial Therapy

Symptomatic vasospasm following aneurysmal subarachnoid hemorrhage (SAH) occurs in roughly 30% of cases. However, vasospasm after primary intraventricular hemorrhage (IVH) is rare and described in only a handful of case reports and small retrospective studies. We present a patient with primary IVH. A conventional cerebral angiogram ruled out vascular anomalies but demonstrated severe diffuse cerebral vasospasm. The patient was treated with intra-arterial vasodilators, resulting in an immediate and profound improvement in the patient’s neurological examination. Several days later, the patient had another decline in neurological status that immediately resolved after treatment with intra-arterial therapy. To our knowledge, this is the first reported case of a profound and immediate improvement in neurological examination following intra-arterial vasodilator administration.

Targeting mast cell as a neuroprotective strategy

Background: Mast cells (MCs) are perivascularly located immune cells of haematopoietic origin. Emerging evidences suggest that the activation of MCs play important roles in the pathogenesis of blood brain barrier disruption, neuroinflammation, and neurodegeneration. Objectives: In this review, we aimed to discuss the detrimental effects of MCs in response to various types of brain injury, as well as the therapeutic potential and neuroprotective effects of targeting the activation and degranulation of MCs, particularly in the management of the acute phase. Methods: An extensive online literature search was conducted through Pubmed/Central on March 2018. Then, we comprehensively summarized the effects of the activation of brain MCs in acute brain injury along with current pharmacological strategies targeting at the activation of MCs. Results: The review of the current literature indicated that the activation and degranulation of brain MCs significantly contribute to the acute pathological process following different types of brain injury including focal and global cerebral ischaemia, intracerebral haemorrhage, subarachnoid haemorrhage, and traumatic brain injury. Conclusions: Brain MCs significantly contribute to the acute pathological processes following brain injury. In that regard, targeting brain MCs may provide a novel strategy for neuroprotection.

Isolated Intraventricular Hemorrhage Associated with Cerebral Vasospasm and Delayed Cerebral Ischemia following Arteriovenous Malformation Rupture

Background

Although it is well characterized in aneurysmal subarachnoid hemorrhage, vasospasm is exceedingly rare following cerebral arteriovenous malformation (AVM) rupture. Subsequently, this complication is poorly characterized with regard to delayed cerebral ischemia (DCI). We review cases of ruptured AVM to assess the frequency and severity of vasospasm on cerebral angiography, and DCI.

Summary

We reviewed our institutional database of acute intracranial hemorrhages between 2005 and 2014. We identified patients with cerebral AVM rupture and evidence of vasospasm, which was confirmed with digital subtraction angiography (DSA). Cerebral angiograms were evaluated by 2 blinded neurointerventionalists for vasospasm. Statistical analyses were conducted on the angiographic results and variables of interest to determine predictors and associations of vasospasm and DCI. Thirty-six patients with acute intracranial hemorrhage due to ruptured cerebral AVM subsequently underwent cerebral angiography. The interrater reliability for vasospasm was 0.81. The incidence of vasospasm was 13.9% and the incidence of subsequent DCI was 11.1%. A significant relationship existed between isolated intraventricular hemorrhage and vasospasm (p = 0.001) and subsequent DCI (p = 0.006). Radiographic vasospasm was associated with DCI in 80% of the patients (p < 0.0001). No statistical significance existed between subarachnoid hemorrhage and the development of vasospasm or DCI (p = 1.000 and p = 0.626, respectively). All differences were significant at a 99% level of significance.

Key Message

In cases of ruptured AVM, isolated intraventricular hemorrhage appears to be an independent risk factor for vasospasm and DCI. Vasospasm must be considered during late neurological deterioration following AVM hemorrhage, especially in the setting of isolated intraventricular hemorrhage.

Ultrastructural Characteristics of Neuronal Death and White Matter Injury in Mouse Brain Tissues After Intracerebral Hemorrhage: Coexistence of Ferroptosis, Autophagy, and Necrosis

Although intracerebral hemorrhage (ICH) is a devastating disease worldwide, the pathologic changes in ultrastructure during the acute and chronic phases of ICH are poorly described. In this study, transmission electron microscopy was used to examine the ultrastructure of ICH-induced pathology. ICH was induced in mice by an intrastriatal injection of collagenase. Pathologic changes were observed in the acute (3 days), subacute (6 days), and chronic (28 days) phases. Compared with sham animals, we observed various types of cell death in the injured striatum during the acute phase of ICH, including necrosis, ferroptosis, and autophagy. Different degrees of axon degeneration in the striatum were seen in the acute phase, and axonal demyelination was observed in the ipsilateral striatum and corpus callosum at late time points. In addition, phagocytes, resident microglia, and infiltrating monocyte-macrophages were present around red blood cells and degenerating neurons and were observed to engulf red blood cells and other debris. Many synapses appeared abnormal or were lost. This systematic analysis of the pathologic changes in ultrastructure after ICH in mice provides information that will be valuable for future ICH pathology studies.

In Premature Newborns Intraventricular Hemorrhage Causes Cerebral Vasospasm and Associated Neurodisability via Heme-Induced Inflammasome-Mediated Interleukin-1 Production and Nitric Oxide Depletion

BACKGROUND

Intraventricular hemorrhage (IVH) occurs in 60-70% of neonates weighing 500-750 g and 10-20% of those weighing 1,000-1,500 g. All forms of IVH have been associated with neurocognitive deficits. Both subarachnoid and IVHs have been associated with delayed vasospasm leading to neurological deficits. Pathways linking hemoglobin release from blood clots to vasospasm include heme-induced activation of inflammasomes releasing interleukin-1 (IL-1) that can cause calcium dependent and independent vasospasm. Free hemoglobin is a potent scavenger of nitric oxide (NO). Depletion of NO, a potent endogenous vasodilator, has been associated with features of vasospasm.

HYPOTHESIS

In premature newborns, IVH causes cerebral vasospasm and associated neurodisability via heme-induced increased inflammasome-mediated IL-1 production and NO depletion.

CONFIRMATION OF HYPOTHESIS AND IMPLICATIONS

This hypothesis could be confirmed in the IVH animal model with visualization of any associated vasospasm by angiography and in newborns with IVH by transcranial Doppler ultrasonography and correlation with cerebrospinal fluid IL-1 and NO metabolite levels. Confirmation of the role of heme in activation of inflammasomes causing IL-1 production and NO binding could be achieved by measuring the effect of heme scavenging interventions on IL-1 levels and levels of NO metabolites. In addition to removal of the accumulated blood of an IVH by drainage, irrigation, and fibrinolytic therapy intrathecal application of vasodilators and heme scavenging agents like haptoglobin and haemopexin and systemic treatment with inhibitors of inflammasomes like telmisartan could be used to prevent and treat cerebral vasospasm, and thus reduce the risk of associated brain injury in premature neonates.

Malondialdehyde, Glutathione Peroxidase, and Superoxide Dismutase in Cerebrospinal Fluid During Cerebral Vasospasm in Monkeys

Cerebral vasospasm may result from lipid peroxidation induced by oxyhemoglobin in the subarachnoid space after subarachnoid hemorrhage. To test this theory, vasospasm was induced in monkeys by intrathecal injections of oxyhemoglobin or supernatant fluid from autologous blood incubated in vitro. Concentration of malondialdehyde (MDA), a product of lipid peroxidation, was elevated in cerebrospinal fluid (CSF) in association with vasospasm caused by oxyhemoglobin and supernatant fluid. Intrathecal injections of methemoglobin or bilirubin did not cause vasospasm or increased CSF MDA. Activity of glutathione peroxidase in CSF increased significantly after injection of oxyhemoglobin and methemoglobin. There were no significant changes in CSF superoxide dismutase activity although there was a trend towards higher activities in animals treated with oxyhemoglobin, methemoglobin, bilirubin, and supernatant fluid. These results show oxyhemoglobin-induced vasospasm is associated with MDA and lipid peroxidation in the subarachnoid space. Furthermore, detection of peroxidation products after injection of oxyhemoglobin in the absence of erythrocyte membranes indicates that oxyhemoglobin may directly damage cerebral arteries and brain by inducing lipid peroxidation in these structures. Depletion of free-radical scavenging enzymes in CSF did not seem necessary for development of vasospasm. In fact, there was a tendency for vasospasm to elevate enzyme activities, as if production of scavengers was induced by excess free radicals in the subarachnoid space.

Double cisterna magna blood injection model of experimental subarachnoid hemorrhage in dogs

Several animal subarachnoid hemorrhage (SAH) models have been proposed to study the etiology and treatment for cerebral vasospasm. We describe the experimental procedures of a canine double-hemorrhage model of SAH and discuss the pathophysiological parameters and occurrence of angiographic delayed cerebral vasospasm using magnetic resonance (MR) imaging and digital subtraction angiography. Autologous blood was injected twice on days 1 and 3 into the cerebellomedullary cistern of 36 female beagles. All animals showed delayed angiographic vasospasm in the vertebrobasilar arteries on day 7. The degree of vasospasm was 29-42 % of the arterial diameter. However, this model showed no symptomatic vasospasm or ischemic changes detected by MR imaging. This animal model can produce reproducible delayed vasospasm without detectable cerebral infarction on MR imaging. This model allows evaluation of the effect of treatment on delayed vasospasm in the same animals. The canine double-hemorrhage model of SAH is suitable for the quantitative and chronological study of delayed angiographic vasospasm, but not for investigating early brain injury and delayed cerebral ischemia.

Biomarkers and acute brain injuries: interest and limits

For patients presenting with acute brain injury (such as traumatic brain injury, subarachnoid haemorrhage and stroke), the diagnosis and identification of intracerebral lesions and evaluation of the severity, prognosis and treatment efficacy can be challenging. The complexity and heterogeneity of lesions after brain injury are most probably responsible for this difficulty. Patients with apparently comparable brain lesions on imaging may have different neurological outcomes or responses to therapy. In recent years, plasmatic and cerebrospinal fluid biomarkers have emerged as possible tools to distinguish between the different pathophysiological processes. This review aims to summarise the plasmatic and cerebrospinal fluid biomarkers evaluated in subarachnoid haemorrhage, traumatic brain injury and stroke, and to clarify their related interests and limits for diagnosis and prognosis. For subarachnoid haemorrhage, particular interest has been focused on the biomarkers used to predict vasospasm and cerebral ischaemia. The efficacy of biomarkers in predicting the severity and outcome of traumatic brain injury has been stressed. The very early diagnostic performance of biomarkers and their ability to discriminate ischaemic from haemorrhagic stroke were studied.

Mesenchymal stem cells improved the ultrastructural morphology of cerebral tissues after subarachnoid hemorrhage in rats

Subarachnoid hemorrhage (SAH) causes widespread disruption in the cerebral architecture.The process of SAH is complicated and many people lose their lives or become disabled after injury. Mesenchymal stem cells (MSCs) are considered as good candidate for repair of cerebral damage. The aim was to assess the ultrastructural changes in the rat cerebral tissue after intravenous transplantation of MSCs. Female Wistar rats (8 per group) weighing 275~300 g were assigned to control (SAH+PBS) and experimental groups (SAH+MSCs).The samples from middle cerebral arterial wall and parietal cerebral tissue were prepared for transmission electron microscopy (TEM) according to standard protocol. Fine architectures of the vessel wall, including the contraction of the inner layer, smooth muscle layer,as well as neural cells were observed after SAH. Cerebral arterial wall and cortex, including neuronal and glial cells were injured post SAH. But, administration of MSCs improved the structural integrity of cerebral tissues. Changes were much more balanced with their relative improvement in some areas. The role of MSCs for repairing the injured cerebral tissues post experimental SAH was approved by electron microscopy.

Pharmacological treatment of delayed cerebral ischemia and vasospasm in subarachnoid hemorrhage

Subarachnoid hemorrhage after the rupture of a cerebral aneurysm is the cause of 6% to 8% of all cerebrovascular accidents involving 10 of 100,000 people each year. Despite effective treatment of the aneurysm, delayed cerebral ischemia (DCI) is observed in 30% of patients, with a peak on the tenth day, resulting in significant infirmity and mortality. Cerebral vasospasm occurs in more than half of all patients and is recognized as the main cause of delayed cerebral ischemia after subarachnoid hemorrhage. Its treatment comprises hemodynamic management and endovascular procedures. To date, the only drug shown to be efficacious on both the incidence of vasospasm and poor outcome is nimodipine. Given its modest effects, new pharmacological treatments are being developed to prevent and treat DCI. We review the different drugs currently being tested.

Nicardipine prolonged-release implants for preventing cerebral vasospasm after subarachnoid hemorrhage: effect and outcome in the first 100 patients

Vasospasm following subarachnoid hemorrhage (SAH) remains difficult to prevent despite extensive investigative efforts. Nicardipine prolonged-release implants (NPRIs) have been used to prevent vasospasm in patients with SAH since October 1999. The present study analyzed the efficacy and safety of NPRIs in 100 patients with SAH and thick subarachnoid clot (mainly Fisher group 3) treated with NPRIs (diameter 2 mm, length 10 mm, containing 4 mg of nicardipine) during surgery after clipping of the aneurysm. The number and location of pellets depended on the amount and site of the subarachnoid clot on preoperative computed tomography and on the type of craniotomy. Two to 12 pellets were implanted in the cisterns of the internal carotid artery, middle cerebral artery, and/or anterior cerebral artery, where thick clots were present and vasospasm related to delayed ischemic neurological deficit (DIND) was highly likely. Only seven patients developed DIND and five patients suffered cerebral infarction. Angiography performed on days 7-12 revealed no vasospasm in any of the arteries close to the site of NPRI placement. NPRI placement can completely prevent vasospasm in arteries within the cisterns containing thick clots, but is less effective in remote locations.

The effect of mexiletine on the level of lipid peroxidation and apoptosis of endothelium following experimental subarachnoid hemorrhage

OBJECTIVE

The role of apoptosis in etiopathogenesis of vasospasm is not clearly understood yet. It is widely accepted that protection of the endothelial cells from the process of apoptosis could have beneficial effects on cerebral vasospasm after subarachnoid hemorrhage (SAH). Mexiletine blocks sodium and calcium channels and activates ATP-sensitive K(+) channels. Moreover, mexiletine is known to have potent antioxidant effects through inhibiting free-radical production.

METHODS

Twenty-one rabbits were allocated into three groups randomly. Group I was sham operated group (n=7). SAH occurred but no medication was given to the Group II rabbits (SAH only group) (n=7). Mexiletine (50 mg/kg, b.i.d., i.p.) was administered just before SAH and continued until 48 hours following SAH to the Group III rabbits (Mexiletine treated group) (n=7). The ApopTag peroxidase in situ apoptosis detection kit (Serologicals Corporation, former Intergen) was used to demonstrate apoptosis in a cross section of basillary arteries. Thiobarbituric acid reactive material was used to determine the lipid peroxidation levels.

RESULTS

There was a statistically significant difference between lipid peroxidation product levels of the control and SAH only groups (p<0.05). The level of lipid peroxidation production in Mexiletine treated group was significantly lower compared with SAH only group (p<0.05) but not significantly higher than the control group (p>0.05).

DISCUSSION

In the present study we investigated the antioxidant action of mexiletine on apoptosis of endothelium following a rabbit SAH model. This experimental study directly suggested that lipid peroxidation is an important step in development of apoptosis in endothelial cells and prevention of structural integrity of endothelial cell should play a beneficial role in attenuation of cerebral vasospasm. Mexiletine treatment prevented the increase in lipid peroxidation and cerebral vasospasm. Examination of endothelial cells by staining specific for apoptosis demonstrated significant protection of cell integrity in the treated group.

Contribution of the remodeling response to cerebral vasospasm

The authors review the remodeling response of blood vessels that occurs after various injuries to arteries. The role of this response in vasospasm after subarachnoid hemorrhage (SAH) is reviewed. There is some evidence that cerebral arteries remodel after SAH in that they are less compliant and contractile than normal. Evidence for other features, such as alteration of smooth muscle phenotype, proliferation of cells and synthesis of extracellular matrix, is conflicting and requires a further study. A remodeling response probably contributes to vasospasm but the magnitude of its importance, in relation to smooth muscle contraction, which also occurs, also needs to be further defined.

Leukocyte-endothelial cell interactions in chronic vasospasm after subarachnoid hemorrhage

Leukocyte-endothelial cell interactions appear to be the root cause of chronic vasospasm after aneurysmal subarachnoid hemorrhage (aSAH). Early clinical observations and indirect experimental evidence suggested an association between inflammation and chronic vasospasm. Early clinical observations in patients with post-hemorrhagic vasospasm included pyrexia, leukocytosis and the presence of circulating immune complexes. Inflammatory infiltrates and increased levels of immunoglobulins and complement fractions within spastic cerebral arteries also provided early evidence for an inflammatory mechanism underlying chronic vasospasm. Early indirect experimental evidence included the ability to reproduce chronic vasospasm with the introduction of inflammatory agents into the subarachnoid space and the inhibition of vasospasm with anti-inflammatory agents. Currently, however, there is an increasing body of direct molecular evidence that demonstrates the pivotal role of leukocyte-endothelial cell interactions in the development of chronic vasospasm. Cell adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1), lymphocyte function-associated antigen-1 (LFA-1), macrophage antigen-1 (Mac-1) and endothelial (E)-selectin mediate interactions between circulating leukocytes and cerebral endothelium. Following aSAH, ICAM-1 is up-regulated in cerebral endothelial cells and along with other cell adhesion molecules, can be detected in the serum and cerebrospinal fluid (CSF) of patients with post-hemorrhagic vasospasm. Monoclonal antibody blocking experiments have demonstrated that the prevention of leukocyte extravasation into the subarachnoid space prevents chronic vasospasm. Similarly, drugs like ibuprofen, which prevent ICAM-1 up-regulation and transendothelial cell migration of leukocytes, prevent vasospasm. In this review, we highlight early observations that suggested an association between inflammation and post-hemorrhagic vasospasm, detail the role of leukocyte-endothelial cell interactions in the development of chronic vasospasm and discuss therapeutic implications of an inflammatory etiology of post-hemorrhagic cerebral vasospasm.

Comparison between one- and two-hemorrhage models of cerebral vasospasm in rabbits

Injection of blood into the cisterna magna is one of the most frequently used methods to produce subarachnoid hemorrhage (SAH) models in animals. Although the two-hemorrhage model of vasospasm is frequently used in canine and rat models, most studies with rabbits only use the one-hemorrhage model. In the present study, we accomplished a side-by-side comparison between one- and two-hemorrhage models in rabbits. A total of 38 rabbits were randomly divided into three groups, i.e. control group (n = 5), one (n = 15)- and two (n = 18)-hemorrhage model groups. The degree of cerebral vasospasm, the time course of cerebral vasospasm, the clinical behavior, and the residual amount of subarachnoid blood clots were measured on days 3, 5 and 7 after the establishment of the models. Compared with one-hemorrhage model, the time course of vasospasm in the two-hemorrhage model was more coincident with that observed in humans, produced more severe vasospasm after SAH, and had an acceptable low mortality. In conclusion, the two-hemorrhage model in rabbits is more appropriate than the one-hemorrhage model for the research on SAH or cerebral vasospasm, and thus can be used for the investigation of the mechanisms of and therapeutic approaches for cerebral vasospasm.

Higher Hemoglobin is Associated with Less Cerebral Infarction, Poor Outcome, and Death after Subarachnoid Hemorrhage

OBJECTIVE:

Higher-goal hemoglobin (hgb) and more packed red blood cell transfusions lead to worse outcomes in general critical care patients. There are few data on hgb, transfusion, and outcomes after aneurysmal subarachnoid hemorrhage (SAH).

METHODS:

We reviewed the daily hgb levels of 103 patients with aneurysmal SAH. Cerebral infarction was diagnosed by computed tomographic scan. We corrected for Hunt and Hess grade, age, and angiographic vasospasm in multivariate models.

RESULTS:

Of 103 patients, the mean age was 55.3 ± 14.5 years, 63% were women, and 29% were Hunt and Hess Grades 4 and 5; hgb values steadily declined from 12.6 ± 1.7 g/dl the day of SAH to 10.4 ± 1.2 g/dl by Day 14. Patients who died had lower hgb than survivors on Days 0, 1, 2, 4, 6, 10, 11, and 12 (P ≤ 0.05). Higher mean hgb was associated with reduced odds of poor outcome (odds ratio, 0.57 per g/dl; 95% confidence interval [CI], 0.38–0.87; P = 0.008) after correcting for Hunt and Hess grade, age, and vasospasm; results for hgb on Days 0 and 1 were similar. Higher Day 0 (odds ratio, 0.7 per g/dl; 95% CI, 0.5–0.99; P = 0.05) and mean hgb (odds ratio, 0.57 per g/dl; 95% CI, 0.38–0.87; P = 0.009) predicted a lower risk of cerebral infarction independent of vasospasm. There were no associations between hgb and other prognostic variables.

CONCLUSION:

We found that SAH patients with higher initial and mean hgb values had improved outcomes. Higher hgb in SAH patients may be beneficial. The efficacy and safety of blood transfusions to increase hgb in patients with SAH may warrant further study.

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.

Cerebral vasospasm associated with intraventricular hemorrhage

BACKGROUND AND PURPOSE

Cerebral vasospasm remains a major complication associated with aneurysmal subarachnoid hemorrhage. Although several case reports have demonstrated that intraventricular hemorrhage (IVH) related to a ruptured arteriovenous malformation can result in vasospasm in the absence of subarachnoid hemorrhage, to our knowledge, this is the first case report of cerebral vasospasm associated with primary IVH.

CASE REPORT

A 44-year-old female was admitted with cerebellar infarction secondary to left posteroinferior cerebellar artery occlusion. Her hospital stay was complicated by primary IVH. Three days after her IVH, she became disoriented and developed a peculiar interest in counting numbers. This behavioral change was associated with an increase in cerebral blood flow velocity in the anterior circulation. Middle cerebral artery M1 velocity almost doubled from 65 to 130 cm/second. Her symptoms resolved with initiation of hypervolemia, hypertension, and hemodilution (triple H) therapy.

CONCLUSIONS

Cerebral vasospasm may contribute to the comorbidities of IVH. Routine transcranial Doppler may be warranted for screening of cerebral vasospasm in IVH patients.

Single or Multiple Small Subarachnoid Hemorrhages by Puncturing a Small Branch of the Rat Basilar Artery Causes Chronic Cerebral Vasospasm

OBJECTIVE

This study looked at the effects of single and multiple small subarachnoid hemorrhage (SAH) caused by puncturing a small branch of the basilar artery in rats.

METHODS

Rats were subjected to single SAH (n = 21), multiple SAH (n = 21), sham operation (n = 21), or no procedures (control group, n = 7). SAH was induced in rats by transclival puncture of a small branch of the basilar artery. In the multiple-SAH hemorrhage groups, three small hemorrhages were produced in the same artery at three different times (initial and 24 and 48 h). In the single-SAH groups, one small hemorrhage was produced. Measurements of local cerebral blood flow (LCBF) were made at the initial SAH procedure and at three different time points. Seven animals from each general grouping were killed on Days 4, 10, and 14 (after LCBF was measured). Three different levels of the basilar artery were examined in each animal. Luminal area and arterial wall thickness were measured, and the findings were compared with control and corresponding sham group findings.

RESULTS

LCBF dropped dramatically (by 40%) immediately after SAH and reached levels near baseline within 15 minutes (n = 42) (P < 0.001). LCBF continued to drop after initial SAH and reached the lowest level on Day 10 (P < 0.001) or Day 14 (P < 0.05). Significant luminal narrowing (P < 0.01) and thickening of the arterial wall (P < 0.01) were observed in both groups.

CONCLUSION

Single or multiple small SAHs produced by puncturing the basilar artery in the rat cause similar acute and chronic cerebral vasospasm.

The effect of EGb-761 on morphologic vasospasm in canine basilar artery after subarachnoid hemorrhage

This study investigated the effects of Ginkgo biloba extract (EGb-76l), an anti-oxidant and platelet-activating factor antagonist, on basilar artery vasospasm in an experimental canine subarachnoid hemorrhage model. Morphometric analyses were performed, and serum and cerebrospinal fluid endothelin-l levels were measured by radioimmunoassay. Comparisons were made between treated and untreated groups. Twenty-four mongrel dogs were randomly assigned to three groups. The animals in group 1 (n = 8) were not subjected to subarachnoid hemorrhage and received no treatment. In this group, serum and cerebrospinal fluid endothelin-l levels were measured daily for 8 days. On day 9, the animals were killed and their basilar arteries were excised for histopathological examination. In group 2 (n = 8), subarachnoid hemorrhage was produced using autologous arterial blood, and daily intravenous boluses of saline were administered for the next 8 days. Assessments of endothelin-l levels and the basilar arteries were performed as described for group 1. In group 3 (n = 8), subarachnoid hemorrhage was produced using autologous arterial blood, and daily intravenous boluses of EGb-761 were administered for 8 days. Endothelin-1 levels and the basilar arteries were assessed as described above. The groups' serum endothelin-1, cerebrospinal fluid endothelin-1, and histopathological findings were compared. In group 1, the serum and cerebrospinal fluid endothelin-1 levels did not change significantly over the 8 days, and histopathological examination of the basilar arteries revealed no abnormalities. In group 2, the serum and cerebrospinal fluid endothelin-1 levels increased abruptly and significantly on day 2, and remained high to the end of the study period (day 8). Histopathological examination revealed marked vasospasm. In group 3, the serum and cerebrospinal fluid endothelin-1 levels followed the same pattern observed in group 2; however, the arteries showed significantly less vasospasm than that observed in group 2. The study findings did not provide information about the mechanism of action of the platelet-activating factor-antagonist EGb-761, but they clearly show that this agent decreases morphologic vasospasm in the dog basilar artery.

The pharmacology of nitric oxide in the peripheral nervous system of blood vessels

Unanticipated, novel hypothesis on nitric oxide (NO) radical, an inorganic, labile, gaseous molecule, as a neurotransmitter first appeared in late 1989 and into the early 1990s, and solid evidences supporting this idea have been accumulated during the last decade of the 20th century. The discovery of nitrergic innervation of vascular smooth muscle has led to a new understanding of the neurogenic control of vascular function. Physiological roles of the nitrergic nerve in vascular smooth muscle include the dominant vasodilator control of cerebral and ocular arteries, the reciprocal regulation with the adrenergic vasoconstrictor nerve in other arteries and veins, and in the initiation and maintenance of penile erection in association with smooth muscle relaxation of the corpus cavernosum. The discovery of autonomic efferent nerves in which NO plays key roles as a neurotransmitter in blood vessels, the physiological roles of this nerve in the control of smooth muscle tone of the artery, vein, and corpus cavernosum, and pharmacological and pathological implications of neurogenic NO have been reviewed. This nerve is a postganglionic parasympathetic nerve. Mechanical responses to stimulation of the nerve, mainly mediated by NO, clearly differ from those to cholinergic nerve stimulation. The naming "nitrergic or nitroxidergic" is therefore proposed to avoid confusion of the term "cholinergic nerve", from which acetylcholine is released as a major neurotransmitter. By establishing functional roles of nitrergic, cholinergic, adrenergic, and other autonomic efferent nerves in the regulation of vascular tone and the interactions of these nerves in vivo, especially in humans, progress in the understanding of cardiovascular dysfunctions and the development of pharmacotherapeutic strategies would be expected in the future.

Experimental subarachnoid haemorrhage models in rats

There is no comprehensive and reliable model available in small animals that are suitable for the study of subarachnoid haemorrhage (SAH). In the study we reviewed the advantages and disadvantages of available SAH models in rats and presented our model. Experimental SAH was induced in a group of 350-450 g Sprague-Dawley rats. A 2 mm-diameter burr hole was drilled and, working under a microscope, haemorrhage was produced by transclival puncture of the basilar artery with a 20 microns thick piece of glass. The rats were assigned to either the experimental group (n: 7) or the control group (n: 7). Local cerebral blood flow (LCBF), intracranial pressure (ICP), and cerebral perfusion pressure (CPP) were measured for 60 min after SAH, after which the rats were decapitated. Microscopic examinations were done on three different segments of the basilar artery. There was a significant and sharp drop in LCBF just after SAH was induced (56.17 +/- 12.80 mlLD/min/100 g and 13.57 +/- 5.85 mlLD/min/100 g for baseline and post-SAH, respectively; p < 0.001), the flow slowly increased by the end of the experiment but never recovered to pre-SAH values (43.63 +/- 7.6 mlLD/min/100 g, p < 0.05). ICP (baseline 7.33 +/- 0.8 mmHg) increased acutely to 70.6 +/- 9.2 mmHg, and also returned to normal levels by 60 min after SAH. CPP (baseline 75.1 +/- 4.9 mmHg) dropped accordingly (to 21.0 +/- 6.3 mmHg) and then increased, reaching 70.1 +/- 4.9 mmHg at 60 min after SAH. Examinations of the arteries revealed decreased inner luminal diameter and distortion of the elastica layer. We present an inexpensive and reliable model of SAH in the rat that allows single and multiple haemorrhages and to study the early and late course of pathological changes.

Comparison of three rat models of cerebral vasospasm

A substantial number of rat models have been used to research subarachnoid hemorrhage-induced cerebral vasospasm; however, controversy exists regarding which method of selection is appropriate for this species. This study was designed to provide extensive information about the three most popular subarachnoid hemorrhage rat models: the endovascular puncture model, the single-hemorrhage model, and the double-hemorrhage model. In this study, the basilar artery and posterior communicating artery were chosen for histopathological examination and morphometric analysis. Both the endovascular puncture model and single-hemorrhage model developed significant degrees of vasospasm, which were less severe when compared with the double-hemorrhage model. The endovascular puncture model and double-hemorrhage model both developed more vasospasms in the posterior communicating artery than in the basilar artery. The endovascular puncture model has a markedly high mortality rate and high variability in bleeding volume. Overall, the present study showed that the double-hemorrhage model in rats is a more suitable tool with which to investigate mechanism and therapeutic approaches because it accurately correlates with the time courses for vasospasm in humans.

Serum von Willebrand factor, matrix metalloproteinase-9, and vascular endothelial growth factor levels predict the onset of cerebral vasospasm after aneurysmal subarachnoid hemorrhage

OBJECTIVE

Endothelial damage and intimal proliferation occur in vasospastic cerebral arteries after subarachnoid hemorrhage (SAH). In the peripheral vasculature, endothelial damage increases intimal matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) levels, causing neointimal proliferation. We hypothesized that serum von Willebrand factor (vWF) (a marker of endothelial cell death), MMP-9, and VEGF levels could serve as prognostic markers in predicting the occurrence of cerebral vasospasm.

METHODS

Venous serum vWF, MMP-9, and VEGF levels were prospectively measured daily, for 12 days or until the onset of vasospasm, for 45 consecutive patients admitted with SAH (n = 38) or admitted for elective aneurysm clipping (control subjects, n = 7). The development of transcranial Doppler flow velocities of more than 180 cm/s and/or new focal neurological deficits with angiographically confirmed vasospasm was considered the onset of vasospasm. To establish whether these markers were specific for vasospasm versus ischemia, blood samples were obtained from a concurrent group of 42 patients within 24 hours after stroke onset unrelated to SAH.

RESULTS

Fifty-seven percent of patients (22 of 38 patients) developed vasospasm, 4 to 11 days after SAH (median, 7 d). Mean peak serum vWF, MMP-9, and VEGF levels were increased in the SAH prevasospasm cohort, compared with the SAH nonvasospasm cohort (vWF, 5526 +/- 929 versus 4934 +/- 599 ng/ml, P = 0.01; MMP-9, 705 +/- 338 versus 438 +/- 154 ng/ml, P = 0.006; VEGF, 0.12 +/- 0.06 versus 0.06 +/- 0.06 ng/ml, P = 0.023). Mean peak vWF, MMP-9, and VEGF levels for the focal ischemia cohort (vWF, 4645 +/- 875 ng/ml, P = 0.01; MMP-9, 250 +/- 308 ng/ml, P = 0.001; VEGF, 0.03 +/- 0.04 ng/ml, P = 0.001) were markedly lower in comparison with the SAH prevasospasm cohort and were unchanged in comparison with the control cohort. vWF levels of more than 5500 ng/ml, VEGF levels of more than 0.12 ng/ml, and MMP levels of more than 700 ng/ml each independently increased the odds of subsequent vasospasm (18-, 20-, and 25-fold, respectively).

CONCLUSION

The development of cerebral vasospasm after SAH was preceded by increases in serum vWF, MMP-9, and VEGF levels. Increased serum vWF, MMP-9, and VEGF levels could accurately predict the onset of cerebral vasospasm after SAH. These factors were not elevated by SAH alone or in a separate cohort of patients with ischemic stroke, suggesting that these factors might play a role in the pathogenesis of human cerebral vasospasm.

Vasospasm in monkeys resolves because of loss of and encasement of subarachnoid blood clot

BACKGROUND AND PURPOSE

We studied in monkeys why vasospasm resolves after subarachnoid hemorrhage (SAH).

METHODS

Monkeys underwent angiography and right (n=17) or bilateral (n=8) SAH. Animals with bilateral SAH underwent angiography 1, 3, 5, and 7 days later. Animals with right SAH underwent angiography 7 days later. The clot was then not removed (n=5), removed and replaced with fresh clot (n=7), or removed and not replaced (n=5). At the same time on day 7, the removed clot (n=12) or fresh clot (n=5) was placed on the left side. Angiography was repeated every 2 days until day 14.

RESULTS

SAH caused significant vasospasm on day 7 that resolved by day 14. Removal of clot on day 7 resulted in more rapid resolution of vasospasm. Placement of fresh clot onto arteries that had already been exposed to clot for 7 days produced vasospasm that persisted without resolving for an additional 7 days. Placement of 7-day-old clot from the right onto previously unexposed left arteries or of clot from blood removed from an animal 7 days after SAH caused significantly more rapid onset of vasospasm compared with de novo vasospasm. Microscopic examination of the clots showed they were surrounded by macrophages 7 days after SAH. Arterial compliance and contractility were reduced in relation to duration of the exposure of arteries to clot.

CONCLUSIONS

Vasospasm resolves because of loss of subarachnoid blood clot. We hypothesize that reduced spasmogen release from the clot contributes to resolution of vasospasm. There was no response in the cerebral arteries that rendered them less responsive to the subarachnoid clot.

Confocal microscopic evidence of decreased alpha-actin expression within rabbit cerebral artery smooth muscle cells after subarachnoid haemorrhage

Our objective was to determine whether subarachnoid haemorrhage modifies cerebral artery smooth muscle cell phenotype and the contractile protein alpha-actin measured 7 days after haemorrhage. We used a rabbit subarachnoid haemorrhage model and immunofluorescence labelling of alpha-smooth muscle actin, vimentin and desmin. The paired comparison between the haemorrhage and sham rabbits was performed using confocal laser-scanning microscopy. We found in the haemorrhage group significantly less intense alpha-actin immunostaining (p = 0.036) and more intense vimentin immunostaining (p = 0.043) but no significant change in the intensity of desmin staining. Our results indicate an absolute decrease after subarachnoid haemorrhage in the amount of functional alpha-actin and in the light of the literature may suggest a certain degree of dedifferentiation of smooth muscle cells in the cerebral artery wall.

Antioxidant therapy against cerebral vasospasm following aneurysmal subarachnoid hemorrhage

1. Approximately one-third of the morbidity and mortality due to aneurysmal subarachnoid hemorrhage (SAH) is caused by delayed ischemic neurological deficit (DIND) due to cerebral vasospasm. 2. Compared to prolonged arterial constriction in other parts of the body, cerebral vasospasm is characterized by its long duration and refractoriness to vasodilators such as calcium antagonists. 3. Whereas oxyhemoglobin (oxyHb) liberated into the CSF from the subarachnoid clot has been deemed the causative agent of vasoconstriction, the biochemical mechanisms whereby oxyHb elicits prolonged constriction of the cerebral arteries has remained elusive. Here, we suggest that oxyHb triggers the generation of reactive oxygen intermediates (ROI) within the CSF. 4. Multiple lines of evidence indicate that the occurrence of vasospasm, namely, prolonged smooth muscle contraction, is due to the following intracellular events. 5. First, hydroxyl radicals (OH*), the most reactive species of ROI, are generated within the cerebral arterial wall via the Fenton and Haber-Weiss reactions catalyzed by oxyHb. Second, subsequent peroxidative membrane damage in the arterial smooth muscle cell enhances the metabolism of phosphatidylcholine and phosphatidylethanolamine, leading to a rise in the intracellular level of diacylglycerol, an endogenous activator of protein kinase C. 6. The prolonged arterial contraction that occurs during vasospasm is attributable primarily to the activation of protein kinase C, not to the Ca2+/calmodulin system. In this article, literature relevant to the above thesis is reviewed, and the rationale for the antioxidant therapy against cerebral vasospasm is discussed.

Effects of intra-arterial papaverine on the chronic period of cerebral arterial vasospasm in rats

OBJECTIVES

The effect of intra-arterial papaverine (IAP) on the basilar artery (BA) and cerebral perfusion pressure (CPP) during the chronic period of the cerebral arterial vasospasm in rats was investigated.

MATERIAL AND METHODS

The study was carried out on male, Swiss-Albino rats, the weight of each varied between 200-340 g. A large volume (0.3 cc) of nonheparinized, autolog blood was utilized in order to cause a subarachnoid haemorrhage. For the measurement of the changes in BA diameter, the angiograms were made prior to the subarachnoid haemorrhage, 48 h after the subarachnoid haemorrhage, and in 1, 15, 30, and 60 min after papaverine infusion into the vertebral artery. The BA vascular index was found separately for each angiogram. At each stage of the procedure mean arterial blood pressure (MAP) and intracranial pressure (ICP) were monitored.

RESULTS

BA diameter measurements were found to be 226+/-32 microm in pre-haemorrhage angiograms and 145+/-44 microm in angiograms 48 h after the subarachnoid haemorrhage. In the angiograms immediately after IAP, it was found that the BA diameter reached about 92% (206+/-41 microm) of control values. But, in the angiograms 15 min after IAP, it was observed that BA underwent a spasm again.

CONCLUSION

The dilatator effect of IAP on BA was temporary. Additionally, in the chronic vasospasm period when cerebral autoregulation mechanisms are impaired and CPP decreased significantly, IAP has adversely affected CPP decreasing MAP.

Reversal of cerebral vasospasm using an intrathecally administered nitric oxide donor

OBJECT

Intrathecal bolus administration of (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)aminio]diazen++ +-1-ium-1,2-diolate (DETA/NO), a long half-life diazeniumdiolate-class nitric oxide (NO) donor, was evaluated for safety and efficacy in the treatment of delayed cerebral vasospasm in a canine model of subarachnoid hemorrhage (SAH).

METHODS

The baseline basilar artery (BA) diameter of 25 dogs was measured with the aid of angiography on Day 0. Vasospasm was then induced by intracisternal injection of autologous arterial blood on Days 0 and 2. Repeated arteriography on Day 7 revealed an average BA diameter of 58% of baseline. Each dog was then randomized to one of four groups: a pathology control group (SAH only, four animals); a treatment control group (SAH plus 2 micromol of the inactive drug carrier DETA, eight animals); a low-dose treatment group (SAH plus 0.2 micromol DETA/NO, six animals); or a high-dose treatment group (SAH plus 2 micromol DETA/NO, six animals). The drugs were administered in a 2-ml intrathecal bolus via the cisterna magna. Arterial caliber was monitored by angiography over the subsequent 4 hours. A 2-micromol dose of the drug was then given and serial arteriography continued for an additional hour to screen for tachyphylaxis. Intracranial pressure and respiratory and hemodynamic parameters were continuously monitored. Histopathological analyses of the animals' brains were performed after the dogs were killed on Day 8. The drug DETA/NO produced reversal of vasospasm in a dose-dependent fashion that roughly followed a double exponential time course. Doses of 2 micromol DETA/NO resulted in restoration of the angiographically monitored BA diameter to the prevasospasm size at 1.5 hours posttreatment, and this was sustained at 88% of baseline at 4 hours (p < 0.01, independent samples t-test). By contrast, the treatment control group remained on average at 54% of baseline diameter. The low-dose treatment group achieved only partial and more transitory relaxation. Histopathological analyses showed findings consistent with chronic SAH but did not demonstrate any toxicity associated with the NO donor. No adverse physiological changes were seen.

CONCLUSIONS

This study indicates that long-acting NO donors are potentially useful as agents to restore circulation in patients suffering from cerebral vasospasm.

Decoy administration of NF-kappaB into the subarachnoid space for cerebral angiopathy

Subarachnoid hemorrhage (SAH), encephalitis, meningitis, and autoimmune diseases sometimes lead to cerebral angiopathy, characterized specifically by narrowing of vessels, morphological changes in the structure of vessel walls, and a concomitant decrease in cerebral blood flow. Many patients also develop delayed ischemic neurological deficits. Thus, preventing vascular reactions is of paramount importance in treating SAH. Although cerebral vasospasm has some relationship with the inflammatory reaction of major cerebral vessels against the autologous blood, and many trials have attempted to prevent angiopathy after SAH, an effective treatment has not yet been established. The purpose of this article is to evaluate the preventive effect of nuclear factor KB (NF-kappaB) decoy oligo-DNA after SAH; since NF-kappaB is closely related to inflammation. In the rabbit angiopathy model after SAH, we evaluated the effectiveness of the decoy oligo-DNA using the angiographic (digital subtraction angiography) and histological (hematoxylin-eosin and Masson's trichrome staining) methods. Moreover, a gel-shift assay for NF-kappaB was also performed in order to evaluate the activity of NF-kappaB. We describe a new concept for treating cerebral angiopathy after SAH and for successfully inhibiting cerebral vasospasm and morphological changes in vessel walls in a rabbit model. In this treatment, we used synthetic double-strand oligo-DNA with a high affinity for transcription factor NF-kappaB, and cationic liposome complex administered through the cerebrospinal fluid.

Balloon angioplasty for the treatment of vasospasm: results of first 50 cases

OBJECTIVE

To report the results of the first 50 consecutive patients with vasospasm secondary to subarachnoid hemorrhage treated with balloon angioplasty after failure of medical management.

METHODS

Retrospective uncontrolled study of 50 consecutive patients treated with balloon angioplasty between February 1988 and July 1992. Forty-six had objective clinical deterioration despite maximal medical therapy, whereas four were treated on the basis of rapidly accelerating transcranial Doppler velocities and decreased regional blood perfusion detected by technetium-99m-exametazime brain single photon emission computed tomography. All patients had evidence of marked vasospasm demonstrated by angiography. Thirty-two (64%) and 46 (92%) patients underwent angioplasty within 12 and 18 hours, respectively.

RESULTS

Of the patients with clinical evidence of vasospasm-induced ischemia, 28 (61%) showed sustained neurological improvement within 72 hours of angioplasty. Three (6%) patients deteriorated within 72 hours after angioplasty, with two (4%) patients dying immediately after angioplasty as a result of vessel rupture and the other patient's Glasgow Coma Scale score decreasing by 2. Two additional patients in poor condition with Hunt and Hess Grade V at the time of angioplasty subsequently died during hospitalization. Two other patients died as a result of unclipped aneurysms that subsequently bled 4 and 12 days after angioplasty, respectively. The improvement demonstrated clinically, angiographically, and by transcranial Doppler after angioplasty was sustained, with only one patient requiring subsequent angioplasty of a previously dilated segment (total, 170 vessel segments dilated). Two patients developed vasospasm in previously undilated segments.

CONCLUSION

Timely balloon angioplasty can reverse delayed ischemic deficit caused by vasospasm in patients for whom medical therapy has failed.

Subarachnoid hemorrhage and the role of potassium channels in relaxations of canine basilar artery to nitrovasodilators

This study was designed to determine the effect of subarachnoid hemorrhage (SAH) on potassium (K+) channels involved in relaxations of cerebral arteries to nitrovasodilators. The effects of K+ channel inhibitors on relaxations to 3-morpholinosydnonimine (SIN-1) and sodium nitroprusside (SNP) were studied in rings of basilar arteries obtained from untreated dogs and dogs exposed to SAH. The levels of cyclic GMP were measured by radioimmunoassay. In rings without endothelium, concentration-dependent relaxations to SIN-1 (10(-9)-10(-4) mol/L) and SNP (10(-9)-10(-4) mol/L) were not affected by SAH, whereas increase in cyclic GMP production stimulated by SIN-1 (10(-6) mol/L) was significantly suppressed after SAH. The relaxations to SIN-1 and SNP were reduced by charybdotoxin (CTX: 10(-7) mol/L), a selective Ca(2+)-activated K+ channel inhibitor, in both normal and SAH arteries; however, the reduction of relaxations by CTX was significantly greater in SAH arteries. By contrast, the relaxations to these nitrovasodilators were not affected by glyburide (10(-5) mol/L), an ATP-sensitive K+ channel inhibitor, in both normal and SAH arteries. These findings suggest that in cerebral arteries exposed to SAH, CA(2+)-activated K+ channels may play a compensatory role in mediation of relaxations to nitric oxide. This may help to explain mechanisms of relaxations to nitrovasodilators in arteries with impaired production of cyclic GMP.

Subarachnoid hemorrhage impairs cerebral blood flow response to nitric oxide but not to cyclic GMP in large cerebral arteries

Nitric oxide (NO) increases 3',5'-cyclic guanosine monophosphate (cGMP) in vascular smooth muscle and increases cerebral blood flow (CBF). In early stages of cerebral ischemia, NO plays a beneficial role in sustaining CBF. Subarachnoid hemorrhage (SAH), one of the main causes of ischemia, may impair vascular reactivity to NO. To test the hypothesis, 48 h after SAH was induced in rats, we examined the CBF response to the NO donor, SIN-1 (3-morpholinosydnonimine). We measured CBF by laser-Doppler flowmetry in association with: (1) intracarotid injection (for 30 min) of SIN-1 (1.5 mg/kg), 8-bromo-cGMP (7.5 mg/kg), papaverin (1.5 mg/kg) or vehicle; (2) cortical superfusion (for 90 min) of SIN-1 (10(-5) M) or vehicle through the cranial window. Hypotension produced by these vasodilators was controlled with phenylephrine. Vehicle alone did not change CBF throughout the measurement. Intracarotid infusion of SIN-1 (n = 6/group) increased CBF up to 128.6 +/- 3.9% and 111.9 +/- 2.9% in the control group and the SAH group, respectively. SAH significantly attenuated the response (P < 0.05, ANOVA). SAH did not affect the CBF increases elicited by intracarotid administration of cGMP or papaverin, or cortical superfusion of SIN-1. We conclude that during chronic vasospasm SAH disturbs the pathway between NO release and cGMP production in large cerebral arteries. The impairment accounts for the fragility of the brain in the face of ischemia following SAH.

Effect of subarachnoid hemorrhage on cerebral vasodilatation in response to activation of ATP-sensitive K+ channels in chronically hypertensive rats

BACKGROUND AND PURPOSE

Cerebral vasodilatation in response to aprikalim, an opener of ATP-sensitive K+ channels, is selectively augmented after subarachnoid hemorrhage (SAH). Vasodilatation in response to activation of ATP-sensitive K+ channels, however, is impaired during chronic hypertension. Hypertension may contribute to a worse outcome after SAH, but the nature of the relationship between hypertension and SAH is uncertain. In the present study we examined responses of the basilar artery to aprikalim after SAH in normotensive Wistar-Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP).

METHODS

In anesthetized WKY and SHRSP, we measured changes in diameter of the basilar artery in response to aprikalim and papaverine using a cranial window 2 days after injection of 0.3 mL saline or autologous blood into the cistema magna.

RESULTS

Under control conditions, aprikalim (0.1 to 1 mumol/L) and papaverine (10 to 100 mumol/L) produced dilatation of the basilar artery. After SAH, responses to aprikalim were not significantly altered in WKY and were markedly increased in SHRSP compared with saline-injected control rats. In contrast, vasodilator responses to papaverine were not changed by SAH in either WKY or SHRSP, suggesting that augmented vasodilatation in response to aprikalim after SAH was selective.

CONCLUSIONS

Responses of the basilar artery to aprikalim were greatly augmented in SHRSP after SAH. Because vasodilator responses to many stimuli are impaired after SAH and cerebral vasodilator responses to several stimuli are impaired by chronic hypertension, augmented responses to activation of K+ channels despite the presence of hypertension are unusual.

Increased levels of plasma cholesteryl ester hydroperoxides in patients with subarachnoid hemorrhage

The pathophysiology of subarachnoid hemorrhage (SAH) may involve free radical production and lipid peroxidation. We examined plasma levels of cholesteryl ester hydroperoxides (CEOOH) and antioxidants in 25 patients with SAH, and 10 neurologic controls with lacunar stroke. Patients with SAH had significantly increased plasma levels of CEOOH, which peaked on day 5 after the ictus. Concentrations of CEOOH were significantly increased, and ascorbic acid concentrations were significantly decreased in patients who developed vasospasm compared with patients without vasospasm. Increased levels of CEOOH were associated with increased mortality and correlated with clinical outcome scales. These results implicate oxidative stress in the pathogenesis of SAH and suggest that measurements of CEOOH in plasma may be useful both prognostically as well as in monitoring therapeutic interventions.

Functional changes in cultured strips of canine cerebral arteries after prolonged exposure to oxyhemoglobin

The present study was undertaken to determine whether oxyhemoglobin (OxyHb) is responsible for the functional alterations in the cerebral arteries observed during chronic vasospasm after subarachnoid hemorrhage. Vascular strips of canine basilar arteries were kept in organ culture for 3 days with or without repetitive exposure to OxyHb (OxyHb-treated and control strips). Contractions elicited by high levels of potassium (80 mM) and uridine 5'-triphosphate (3 x 10(-4) M) were reduced in the OxyHb-treated group in a concentration-dependent manner. The relaxations evoked by nitric oxide and 8-bromo-cyclic guanosine monophosphate (8-bromo-cGMP) were not affected. Relaxations elicited by the calcium channel blocker, diltiazem, were attenuated in the OxyHb-treated rings. When the extracellular calcium concentration ([Ca2+]e) was changed from a concentration in the external solution of 10(-8) M to 10(-3) M, myogenic tension developed. Myogenic tension, expressed as a percentage of the maximum contraction in each segment, was augmented in the OxyHb-treated group at [Ca2+]e of 10(-5) M and 10(-4) M. There were no significant differences in passive compliance of the arterial wall between the two groups. These results demonstrated that prolonged exposure to OxyHb in vitro results in a decrease in contractile capacity and an increase in sensitivity to [Ca2+]e, in agreement with previous findings in spastic arteries. By contrast, impairment of the 8-bromo-cGMP-mediated relaxation pathway and increased stiffness of the arterial wall, which have been reported to occur in spastic arteries, were not induced by prolonged exposure to OxyHb in vitro.

Mechanisms of cerebral vasospasm in subarachnoid haemorrhage

Cerebrovascular spasm is a slowly developing constriction of the cerebral arteries, which frequently follows subarachnoid haemorrhage and is associated with considerable morbidity and mortality. The condition has been studied by use of models of subarachnoid haemorrhage in the whole animal and examination of isolated blood vessels or vascular smooth muscle cells in culture. The condition probably arises from the action of haemoglobin released from erythrocytes trapped in the subarachnoid clots, although the mechanism of action of haemoglobin remains uncertain. Systemic pharmacotherapy to avert or reverse vasospasm is still experimental.

Efficacy of steroid hormone in solution for intracranial irrigation during aneurysmal surgery for prevention of the vasospasm syndrome

A series of 55 patients with ruptured cerebral aneurysms were treated with moderate removal of subarachnoid clot followed by intracranial irrigation with pH 8.0 Hartmann solution containing 1 mg/ml of methylpredonisolone sodium succinate after the aneurysmal clipping during early (before day 3) operation. Six (11%) of the 55 patients suffered vasospasm syndrome postoperatively. The clinical results are significantly better than a series of 68 patients operated on and treated before day 3 by intracranial irrigation with Hartmann solution (pH 8.0) only. The possible preventive effect of direct intracranial administration of steroid hormone is discussed.

Angiotensin-converting enzyme inhibitor cilazapril prevents chronic morphologic vasospasm in rat

It has been shown that a long-acting angiotensin-converting enzyme inhibitor cilazapril prevents morphologic changes in arteries secondary to hypertension and endothelial damage, which are analogous to the changes in cerebral arteries following subarachnoid hemorrhage. In this study, the effect of cilazapril on chronic vasospasm was investigated on the rat femoral artery vasospasm model, and morphometric analyses were performed. Animals were divided into three groups. In group 1, femoral arteries were removed after cardiac perfusion. In groups 2 and 3, right femoral arteries were exposed to 0.1 mL autologous whole blood and wrapped with silastic cuff. Animals in group 3 received cilazapril (10 mg/kg) for 7 consecutive days. After the perfusion-fixation, femoral arteries were examined by light and transmission electron microscopy and processed for morphometric analysis. Vessels from animals in group 2 showed a significant luminal narrowing and morphologic changes throughout the vessel wall, while vessels from animals treated with cilazapril appeared nearly normal. These results suggest that cilazapril may be effective in the prevention of chronic vasospasm.

An experimental model of symptomatic vasospasm induced by oxyhemoglobin in rabbits

BACKGROUND AND PURPOSE

There are many experimental models for studies of cerebral vasospasm. However, no ideal model has been established thus far to comparatively reproduce the ischemic state of the brain that may occur in patients after subarachnoid hemorrhage.

METHODS

In the present study, we attempted to induce severe vasospasm in rabbits by using an oxyhemoglobin-rich blood product prepared from hemolyzed arterial blood and evaluate neurological symptoms, cerebral angiogram, cerebral blood flow, and histology.

RESULTS

Clinically significant neurological symptoms were observed in about half of the rabbits. There was no significant correlation between angiographic results of the vasospastic state of the main artery and the severity of neurological symptoms observed. However, the cerebral blood flow was significantly lower than in the control group and significantly correlated with the severity of neurological symptoms. On histological examination, lesions were found in about half of the rabbits. Development of obvious infarction was found more frequently than in other reported models.

CONCLUSIONS

These results suggest that this model is appropriate as an experimental model of vasospasm occurring after subarachnoid hemorrhage and is especially useful in that it induces vasospasm intense enough to cause obvious infarction.

Combined effect of L-arginine and superoxide dismutase on the spastic basilar artery after subarachnoid hemorrhage in dogs

To investigate the function of nitric oxide (a major endothelium-derived relaxing factor) in cerebral arteries after subarachnoid hemorrhage (SAH) in vivo, several nitric oxide-related substances were administered to dogs that had undergone double SAH. These included L-arginine (a substrate for the formation of nitric oxide), NG-monomethyl-L-arginine (L-NMMA, an analog of L-arginine that inhibits the formation of nitric oxide from L-arginine), and superoxide dismutase (SOD, which protects nitric oxide from oxidation by superoxide anion), which were given via intracisternal injection. The diameter of the basilar artery was assessed angiographically. In intact dogs, intracisternal bolus injections of L-arginine (1, 10, or 100 mumol) produced a dose-dependent increase in the internal diameter of the basilar artery; conversely, L-NMMA reduced the diameter of the basilar artery from baseline in a dose-dependent manner. On Days 4 and 7, after two intracisternal injections of autologous blood, L-arginine produced transient vasodilation of the spastic basilar artery, whereas L-NMMA produced no significant vasoconstriction. The vasodilator effect of L-arginine after SAH was stronger on Day 4 than on Day 7, but less than in intact dogs. Intracisternal injection of SOD, which caused no effect per se, enhanced the duration of the vasodilator effect of L-arginine on the basilar artery on Day 4 and both the magnitude and duration of that effect on Day 7. Thus, the basal release of nitric oxide was impaired after SAH, but the ability to synthesize nitric oxide in the vascular wall was not abolished. The finding that the simultaneous injection of SOD enhanced and prolonged the vasodilation induced by sufficient exogenous L-arginine suggests that the inactivation of nitric oxide by superoxide anion contributes to the development of vasospasm.