Medical management of cerebral vasospasm: present and future

The trilateral link between anaesthesia, perioperative visual loss and Flammer syndrome

Background

A variety of factors have been linked to perioperative visual loss during or directly after nonocular and ocular surgeries. Prolonged immobilization, biochemical factors and hemodynamic instability have been discussed as factors in the pathogenesis of this devastating complication. Perioperative visual loss in four consecutive patients, all featuring Flammer syndrome, is reported herein. To our knowledge, we present the first case series, which associates perioperative visual loss with Flammer syndrome. We assume that a low perfusion pressure, disturbed autoregulation of the ocular blood flow and altered drug sensitivity in such subjects, play significant role in the pathogenesis of this dreaded complication.

Cases presentation

We analysed the medical records of four consecutive patients with permanent perioperative visual loss and complemented our findings with additional history taking and clinical examinations. A variety of tests was performed, including colour Doppler ultrasonography of the retroocular vessels, static and dynamic retinal vessel analysis. The visual loss was unilateral in three patients and bilateral in one. An extensive review of published perioperative vision loss cases was conducted.

All four patients were male Caucasians, and exhibited prominent signs and symptoms of Flammer syndrome. The visual loss originated from a propensity for unstable ocular blood flow, combined with hyperreactivity toward pharmacological stimuli, leading together to disturbed autoregulation of the blood supply, and subsequently - to ocular hypoxia. An identified intrinsic hypoperfusion diathesis was a crucial pathophysiologic link in all of the patients. Other, yet unknown systemic or local factors may also be involved in this process.

Conclusions

A review of numerous publications of perioperative visual loss and our data, support our hypothesis for a novel pathophysiologic model and incorporate Flammer syndrome as a distinct risk factor for paradoxical visual loss, during nonocular and ocular surgeries, or invasive procedures. To prevent the complications produced by disturbed blood flow autoregulation in such patients, guidelines for screening and tailored preoperative approach are given.

Transcranial Doppler Ultrasound: Physical Principles and Principal Applications in Neurocritical Care Unit

Transcranial Doppler (TCD) ultrasonography is a noninvasive ultrasound study, which has been extensively applied on both outpatient and inpatient settings. It involves the use of a low-frequency (≤2 MHz) transducer, placed on the scalp, to insonate the basal cerebral arteries through relatively thin bone windows and to measure the cerebral blood flow velocity and its alteration in many different conditions. In neurointensive care setting, TCD is useful for both adults and children for day-to-day bedside assessment of critical conditions including vasospasm in subarachnoid hemorrhage, traumatic brain injury, acute ischemic stroke, and brain stem death. It also allows to investigate the cerebrovascular autoregulation in setting of carotid disease and syncope. In this review, we will describe physical principles underlying TCD, flow indices most frequently used in clinical practice and critical care applications in Neurocritical Unit care.

The functional and structural changes in the basilar artery due to overpressure blast injury

Overpressure blast-wave induced brain injury (OBI) leads to progressive pathophysiologic changes resulting in a reduction in brain blood flow, blood brain barrier breakdown, edema, and cerebral ischemia. The aim of this study was to evaluate cerebral vascular function after single and repeated OBI. Male Sprague-Dawley rats were divided into three groups: Control (Naive), single OBI (30 psi peak pressure, 1 to 2 msec duration), and repeated (days 1, 4, and 7) OBI (r-OBI). Rats were killed 24 hours after injury and the basilar artery was isolated, cannulated, and pressurized (90 cm H2O). Vascular responses to potassium chloride (KCl) (30 to 100 mmol/L), endothelin-1 (10(-12) to 10(-7) mol/L), acetylcholine (ACh) (10(-10) to 10(-4) mol/L) and diethylamine-NONO-ate (DEA-NONO-ate) (10(-10) to 10(-4) mol/L) were evaluated. The OBI resulted in an increase in the contractile responses to endothelin and a decrease in the relaxant responses to ACh in both single and r-OBI groups. However, impaired DEA-NONO-ate-induced vasodilation and increased wall thickness to lumen ratio were observed only in the r-OBI group. The endothelin-1 type A (ET(A)) receptor and endothelial nitric oxide synthase (eNOS) immunoreactivity were significantly enhanced by OBI. These findings indicate that both single and r-OBI impairs cerebral vascular endothelium-dependent dilation, potentially a consequence of endothelial dysfunction and/or vascular remodelling in basilar arteries after OBI.

A Review of the Effectiveness of Neuroimaging Modalities for the Detection of Traumatic Brain Injury

The incidence of traumatic brain injury (TBI) in the United States was 3.5 million cases in 2009, according to the Centers for Disease Control and Prevention. It is a contributing factor in 30.5% of injury-related deaths among civilians. Additionally, since 2000, more than 260,000 service members were diagnosed with TBI, with the vast majority classified as mild or concussive (76%). The objective assessment of TBI via imaging is a critical research gap, both in the military and civilian communities. In 2011, the Department of Defense (DoD) prepared a congressional report summarizing the effectiveness of seven neuroimaging modalities (computed tomography [CT], magnetic resonance imaging [MRI], transcranial Doppler [TCD], positron emission tomography, single photon emission computed tomography, electrophysiologic techniques [magnetoencephalography and electroencephalography], and functional near-infrared spectroscopy) to assess the spectrum of TBI from concussion to coma. For this report, neuroimaging experts identified the most relevant peer-reviewed publications and assessed the quality of the literature for each of these imaging technique in the clinical and research settings. Although CT, MRI, and TCD were determined to be the most useful modalities in the clinical setting, no single imaging modality proved sufficient for all patients due to the heterogeneity of TBI. All imaging modalities reviewed demonstrated the potential to emerge as part of future clinical care. This paper describes and updates the results of the DoD report and also expands on the use of angiography in patients with TBI.

Plasma Estrogen Levels Are Associated With Severity of Injury and Outcomes After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Biochemical mediators alter cerebral perfusion and have been implicated in delayed cerebral ischemia (DCI) and poor outcomes after aneurysmal subarachnoid hemorrhage (aSAH). Estrogens (estrone [E1] and estradiol [E2]) are mediators with neuroprotective properties that could play a role in DCI. This study explored associations between plasma estrogen levels and outcomes following aSAH.

METHODS

Plasma samples from 1-4, 4-6, and 7-10 days after hemorrhage from 99 adult aSAH patients were analyzed for estrogen levels using liquid chromatography tandem mass spectrometry. DCI was operationalized as radiographic/ultrasonic evidence of impaired cerebral blood flow accompanied by neurological deterioration. Outcomes were assessed using the Modified Rankin Scale at 3 and 12 months after hemorrhage. Statistical analysis included correlation, regression, and group-based trajectory.

RESULTS

Higher E1 and E2 levels were associated with higher Hunt and Hess grade (E1, p = .01; E2, p = .03), the presence of DCI (E1, p = .02; E2, p = .02), and poor 3-month outcomes (E1, p = .002; E2, p = .002). Trajectory analysis identified distinct populations over time for E1 (61% E1 high) and E2 (68% E2 high). Patients in higher trajectory groups had higher Fisher grades (E1, p = .008; E2, p = .01), more frequent DCI (E1, p = .04; E2, p = .08), and worse 3-month outcomes (E1, p = .01; E2, p = .004) than low groups.

CONCLUSIONS

These results provide the first clinical evidence that plasma E1 and E2 concentrations are associated with severity of injury and outcomes after aSAH.

Hyperbaric oxygen for cerebral vasospasm and brain injury following subarachnoid hemorrhage

The impact of acute brain injury and delayed neurological deficits due to cerebral vasospasm (CVS) are major determinants of outcomes after subarachnoid hemorrhage (SAH). Although hyperbaric oxygen (HBO) had been used to treat patients with SAH, the supporting evidence and underlying mechanisms have not been systematically reviewed. In the present paper, the overview of studies of HBO for cerebral vasospasm is followed by a discussion of HBO molecular mechanisms involved in the protection against SAH-induced brain injury and even, as hypothesized, in attenuating vascular spasm alone. Faced with the paucity of information as to what degree HBO is capable of antagonizing vasospasm after SAH, the authors postulate that the major beneficial effects of HBO in SAH include a reduction of acute brain injury and combating brain damage caused by CVS. Consequently, authors reviewed the effects of HBO on SAH-induced hypoxic signaling and other mechanisms of neurovascular injury. Moreover, authors hypothesize that HBO administered after SAH may "precondition" the brain against the detrimental sequelae of vasospasm. In conclusion, the existing evidence speaks in favor of administering HBO in both acute and delayed phase after SAH; however, further studies are needed to understand the underlying mechanisms and to establish the optimal regimen of treatment.

Magnesium sulfate treatment improves outcome in patients with subarachnoid hemorrhage: a meta-analysis study

OBJECTIVE

To elucidate the role of magnesium sulfate in patients with subarachnoid hemorrhagic (SAH) brain injury

METHOD

Studies for the meta-analysis were identified from PubMed (1966 to 2009), Embase (1980 to 2009), and two Chinese journals (1989 to 2009). Paper selection was based on randomized controlled trials comparing magnesium sulfate to placebo treatment in patients with SAH. Two independent review authors extracted the data and assessed trial quality. Meta-analysis was performed using the Cochrane Review Manger software.

RESULTS

Five trials involving 482 patients were included in the review. Magnesium sulfate reduced the risk of poor outcome and reduced the occurrence of delayed cerebral ischemia. In the treatment groups, relative risk for poor outcome was 0.73 (CI 0.57-0.93) and 0.66 (CI 0.47-0.92) for delayed cerebral ischemia. Case fatality assessment at three to six months did not show statistically significant data (RR 0.88; CI 0.61-1.29).

CONCLUSION

Magnesium sulfate appears to be an effective treatment option in the management of SAH. Further clinical trials are needed before magnesium sulfate can become a routine treatment for SAH.

Current controversies in the prediction, diagnosis, and management of cerebral vasospasm: where do we stand?

Aneurysmal subarachnoid hemorrhage occurs in approximately 30,000 persons in the United States each year. Around 30 percent of patients with aneurysmal subarachnoid hemorrhage suffer from cerebral ischemia and infarction due to cerebral vasospasm, a leading cause of treatable death and disability following aneurysmal subarachnoid hemorrhage. Methods used to predict, diagnose, and manage vasospasm are the topic of recent active research. This paper utilizes a comprehensive review of the recent literature to address controversies surrounding these topics. Evidence regarding the effect of age, smoking, and cocaine use on the incidence and outcome of vasospasm is reviewed. The abilities of different computed tomography grading schemes to predict vasospasm in the aftermath of subarachnoid hemorrhage are presented. Additionally, the utility of different diagnostic methods for the detection and visualization of vasospasm, including transcranial Doppler ultrasonography, CT angiography, digital subtraction angiography, and CT perfusion imaging is discussed. Finally, the recent literature regarding interventions for the prophylaxis and treatment of vasospasm, including hyperdynamic therapy, albumin, calcium channel agonists, statins, magnesium sulfate, and endothelin antagonists is summarized. Recent studies regarding each topic were reviewed for consensus recommendations from the literature, which were then presented.

Intravenous infusion of magnesium chloride improves epicenter blood flow during the acute stage of contusive spinal cord injury in rats

Vasospasm, hemorrhage, and loss of microvessels at the site of contusive or compressive spinal cord injury lead to infarction and initiate secondary degeneration. Here, we used intravenous injection of endothelial-binding lectin followed by histology to show that the number of perfused microvessels at the injury site is decreased by 80-90% as early as 20 min following a moderate T9 contusion in adult female rats. Hemorrhage within the spinal cord also was maximal at 20 min, consistent with its vasoconstrictive actions in the central nervous system (CNS). Microvascular blood flow recovered to up to 50% of normal volume in the injury penumbra by 6 h, but not at the epicenter. A comparison with an endothelial cell marker suggested that many microvessels fail to be reperfused up to 48 h post-injury. The ischemia was probably caused by vasospasm of vessels penetrating the parenchyma, because repeated Doppler measurements over the spinal cord showed a doubling of total blood flow over the first 12 h. Moreover, intravenous infusion of magnesium chloride, used clinically to treat CNS vasospasm, greatly improved the number of perfused microvessels at 24 and 48 h. The magnesium treatment seemed safe as it did not increase hemorrhage, despite the improved parenchymal blood flow. However, the treatment did not reduce acute microvessel, motor neuron or oligodendrocyte loss, and when infused for 7 days did not affect functional recovery or spared epicenter white matter over a 4 week period. These data suggest that microvascular blood flow can be restored with a clinically relevant treatment following spinal cord injury.

Use of Transcranial Doppler (TCD) ultrasound in the Neurocritical Care Unit

Transcranial Doppler (TCD) is a portable device that uses a handheld 2-MHz transducer. It is most commonly used in subarachnoid hemorrhage where cerebral blood flow velocities in major intracranial blood vessels are measured to detect vasospasm in the first 2 to 3 weeks. TCD is used to detect vasospasm in traumatic brain injury and post-tumor resection, measurement of cerebral autoregulation and cerebrovascular reactivity, diagnosis of acute arterial occlusions in stroke, screening for patent foramen ovale and monitoring of emboli. It can be used to detect abnormally high intracranial pressure and for confirmation of total cerebral circulatory arrest in brain death.

Cerebrospinal fluid 20-HETE is associated with delayed cerebral ischemia and poor outcomes after aneurysmal subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Delayed cerebral ischemia (DCI) is a major complication after aneurysmal subarachnoid hemorrhage (aSAH); it is manifested by changes in cerebral blood flow accompanied by neurological decline, and it results in long-term functional and neuropsychological impairment. Preclinical evidence has demonstrated that the arachidonic acid metabolite, 20-hydroxyeicosatetraenoic acid (20-HETE), affects cerebral microvascular tone and cerebral blood flow after aSAH. The purpose of this study was to determine whether cerebrospinal fluid 20-HETE levels were associated with DCI and long-term neuropsychological outcomes in aSAH patients.

METHODS

Cerebrospinal fluid samples were collected twice daily through 14 days after hemorrhage on 108 acute, adult, aSAH patients. Samples were analyzed for 20-HETE via HPLC MSQ single quadrupole mass spectrometry. DCI was defined as the presence of impaired cerebral blood flow (angiographic vasospasm, elevated transcranial Dopplers, abnormal computed tomography or magnetic resonance perfusion scans) accompanied by neurological deterioration. Outcomes, including death and neuropsychological testing, were completed at 3 months after hemorrhage.

RESULTS

Detectable 20-HETE levels were observed in 31% of patient samples and were associated with severity of hemorrhage (Hunt & Hess [HH], P=0.04; Fisher, P=0.05). Detection of 20-HETE was not associated with angiographic vasospasm (P=0.34); however, detectable 20-HETE was significantly associated with DCI (P=0.016). Our data also suggest that detectable 20-HETE was associated with decreased performance in 5 neuropsychological domains.

CONCLUSIONS

These results provide the first clinical evidence that cerebrospinal fluid 20-HETE concentrations are associated with DCI and poor outcomes, and this provides impetus for future studies to elucidate the clinical utility of inhibiting 20-HETE formation as a novel therapeutic intervention in patients with aSAH.

The anti-inflammatory and neuroprotective effects of ghrelin in subarachnoid hemorrhage-induced oxidative brain damage in rats

To elucidate the putative neuroprotective effects of ghrelin in subarachnoid hemorrhage (SAH)-induced brain injury, Wistar albino rats (n = 54) were divided into sham-operated control, saline-treated SAH, and ghrelin-treated (10 microg/kg/d IP) SAH groups. The rats were injected with blood (0.3 mL) into the cisterna magna to induce SAH, and were sacrificed 48 h after the neurological examination scores were recorded. In plasma samples, neuron-specific enolase (NSE), S-100beta protein, TNF-alpha, and IL-1beta levels were evaluated, while forebrain tissue samples were taken for the measurement of malondialdehyde (MDA), glutathione (GSH), reactive oxygen species levels, myeloperoxidase (MPO), Na(+)-K(+)-ATPase activity, and DNA fragmentation ratio. Brain tissue samples containing the basilar arteries were obtained for histological examination, while cerebrum and cerebellum were removed for the measurement of blood-brain barrier (BBB) permeability and brain water content. The neurological scores were impaired at 48 h after SAH induction, and SAH caused significant decreases in brain GSH content and Na(+)-K(+)-ATPase activity, and increases in chemiluminescence, MDA levels, and MPO activity. Compared with the control group, the protein levels of NSE, S-100beta, TNF-alpha, and IL-1beta in plasma were also increased, while ghrelin treatment prevented all SAH-induced alterations observed both biochemically and histopathologically. The results demonstrate that ghrelin alleviates SAH-induced oxidative brain damage, and exerts neuroprotection by maintaining a balance in oxidant-antioxidant status, by inhibiting proinflammatory mediators, and preventing the depletion of endogenous antioxidants evoked by SAH.

Validation of a new reference standard for the diagnosis of vasospasm

RATIONALE AND OBJECTIVES

The purpose of our study is to perform an internal validation of a new reference standard for vasospasm diagnosis in aneurysmal subarachnoid hemorrhage (A-SAH) patients.

MATERIALS AND METHODS

A retrospective study was performed on A-SAH patients between January 2002 and May 2009. All patients were applied to this new reference standard using a multistage hierarchical approach incorporating clinical and imaging criteria. An internal validation method was performed in two phases to compare the new reference standard with digital subtraction angiography (DSA) and to assess accuracy. In Phase I, the diagnostic outcomes from DSA at the primary level were compared with the secondary/tertiary levels in the reference standard. In Phase II, the new reference standard was compared with chart diagnosis. Accuracy test characteristics, agreement rates, kappa values, and bias indices were calculated.

RESULTS

In Phase I (n = 85), there was 87% agreement rate, 0.674 kappa, and 0.12 bias index. However, there was 100% agreement in patients diagnosed with vasospasm by DSA. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 100%, 61%, 83%, and 100% respectively. In Phase II (n = 137), there was 91% agreement rate, 0.824 kappa, and 0.04 bias index. Sensitivity, specificity, PPV, and NPV were 88%, 95%, 96%, and 87%, respectively.

CONCLUSION

Performing validation methods for a new reference standard is an evolving and ongoing process because limitations and bias in the reference standard are identified. Based on the results of this internal validation, a modification in the new reference standard is made at the primary level, resulting in improvement in its accuracy and classification of A-SAH patients.

The role of transcranial Doppler ultrasonography in the diagnosis and management of vasospasm after aneurysmal subarachnoid hemorrhage

Transcranial Doppler ultrasonography (TCD) is a tool employed by the neurosurgeon and neurointensivist in the management of vasospasm in the intensive care unit after aneurysmal subarachnoid hemorrhage. A review of the current indications, monitoring parameters, indices, and relevance of modern TCD technology is provided, as well as algorithms for the use of TCD ultrasonography in the management of patients with subarachnoid hemorrhage. Other current uses of TCD ultrasonography are also discussed in the setting of neurocritical care.

Noninvasive imaging techniques in the diagnosis and management of aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a devastating condition, requiring prompt diagnosis and therapeutic intervention as well as close monitoring for the development of complications including vasospasm (VS). Although digital subtraction angiography is still considered the gold standard for the diagnosis of aSAH (and vasospasm), new and less invasive modalities are emerging including ultrasound, CT, CT angiography and CT perfusion, and MR imaging. The current evidence for the use of these newer modalities is described for the diagnosis of aSAH and the management of its sequelae including VS.

Evaluation of CT perfusion in the setting of cerebral ischemia: patterns and pitfalls

CTP has a growing role in evaluating stroke. It can be performed immediately following NCCT and has advantages of accessibility and speed. Differentiation of salvageable ischemic penumbra from unsalvageable core infarct may help identify patients most likely to benefit from thrombectomy or thrombolysis. Still, CTP interpretation can be complex. We review normal and ischemic perfusion patterns followed by an illustrative series of technical/diagnostic challenges of CTP interpretation in the setting of acute stroke syndromes.