The effect of subarachnoid sodium nitroprusside on the prevention of vasospasm in subarachnoid haemorrhage

Neuroinflammation and Microvascular Dysfunction After Experimental Subarachnoid Hemorrhage: Emerging Components of Early Brain Injury Related to Outcome

Aneurysmal subarachnoid hemorrhage has a high mortality rate and, for those who survive this devastating injury, can lead to lifelong impairment. Clinical trials have demonstrated that cerebral vasospasm of larger extraparenchymal vessels is not the sole contributor to neurological outcome. Recently, the focus of intense investigation has turned to mechanisms of early brain injury that may play a larger role in outcome, including neuroinflammation and microvascular dysfunction. Extravasated blood after aneurysm rupture results in a robust inflammatory response characterized by activation of microglia, upregulation of cellular adhesion molecules, recruitment of peripheral immune cells, as well as impaired neurovascular coupling, disruption of the blood-brain barrier, and imbalances in endogenous vasodilators and vasoconstrictors. Each of these phenomena is either directly or indirectly associated with neuronal death and brain injury. Here, we review recent studies investigating these various mechanisms in experimental models of subarachnoid hemorrhage with special emphasis on neuroinflammation and its effect on microvascular dysfunction. We discuss the various therapeutic targets that have risen from these mechanistic studies and suggest the utility of a multi-targeted approach to preventing delayed injury and improving outcome after subarachnoid hemorrhage.

Early changes of brain perfusion after subarachnoid hemorrhage - the effect of sodium nitroprusside

Causes of early hypoperfusion after subarachnoid hemorrhage (SAH) include intracranial hypertension as well as vasoconstriction. The aim of the study was to assess the effect of intracerebroventricular (ICV) administration of sodium nitroprusside (SNP) on early hypoperfusion after SAH. Male Wistar rats (220-240 g) were used, SAH group received 250 microl of fresh autologous arterial blood into the prechiasmatic cistern; sham-operated animals received 250 microl of isotonic solution. Therapeutic intervention: ICV administration of 10 microg SNP; 5 microl 5 % glucose (SNP vehicle) and untreated control. Brain perfusion and invasive blood pressure were monitored for 30 min during and after induction of SAH. Despite SNP caused increase of perfusion in sham-operated animals, no response was observed in half of SAH animals. The other half developed hypotension accompanied by brain hypoperfusion. There was no difference between brain perfusion in SNP-treated, glucose-treated and untreated SAH animals during the monitored period. We did not observe expected beneficial effect of ICV administration of SNP after SAH. Moreover, half of the SNP-treated animals developed serious hypotension which led to brain hypoperfusion. This is the important finding showing that this is not the option for early management in patient after SAH.

A Case of Hyperacute Onset of Vasospasm After Aneurysmal Subarachnoid Hemorrhage and Refractory Vasospasm Treated with Intravenous and Intraventricular Nitric Oxide: A Mini Review

BACKGROUND

A case of hyperacute vasospasm, indicating a poor prognosis after aneurysmal subarachnoid hemorrhage (SAH), is reported, and a review is presented of the literature addressing use of nitric oxide (NO) donors in cases of refractory vasospasm and recurrent delayed cortical ischemias (DCI).

CASE DESCRIPTION

A 65-year-old woman was admitted within 1 hour after aneurysmal SAH (Hunt and Hess grade III, Fisher modified by Frontera grade IV). A hyperacute vasospasm had been confirmed arteriographically, the right middle cerebral artery (MCA) aneurysm was immediately coiled and a standard antivasospastic therapy was started. Within 48 hours, the patient developed cerebral vasospasm with DCI. Because the standard therapy failed to control clinical symptoms and to address severe vasospasm, an individualized rescue treatment with NO donors was initiated. A continuous intravenous molsidomine infusion was started and clinical stabilization was achieved for a week (Hunt and Hess grade I; World Federation of Neurological Surgeons grade I; Glasgow Coma Scale score, 15) after which vasospasm and DCI recurred. During a subsequent DCI, we escalated NO donor therapy by adding intraventricular boluses of sodium nitroprusside (SNP). Over the course of the following 22 days, 7 transient DCIs (Glasgow Coma Scale score, 8) were treated with boluses of SNP during continued molsidomine therapy and each time vasospasm and DCI were completely reversed. Despite initial poor prognosis, the clinical outcome was excellent; at 3, 6, and 12 months follow-up the patient's modified National Institutes of Health-Stroke Scale and modified Rankin Scale scores were 0, with no cognitive deficits.

CONCLUSIONS

The review of the literature suggested that combined intravenous molsidomine with intraventricular SNP treatment reversed refractory, recurrent vasospasm and DCIs probably by addressing the hemoglobin NO sink effect, NO depletion, and decreased NO availability after aneurysmal SAH.

Continuous intra-arterial nimodipine infusion in patients with severe refractory cerebral vasospasm after aneurysmal subarachnoid hemorrhage: a feasibility study and outcome results

BACKGROUND

Severe cerebral vasospasm is a major cause of death and disability in patients with aneurysmal subarachnoid hemorrhage. No causative treatment is yet available and hypertensive hypervolemic therapy (HHT) is often insufficient to avoid delayed cerebral ischemia and neurological deficits. We compared patients receiving continuous intra-arterial infusion of the calcium-antagonist nimodipine with a historical group treated with HHT and oral nimodipine alone.

METHODS

Between 0.5 and 1.2 mg/h of nimodipine were continuously administered by intra-arterial infusion via microcatheters either into the internal carotid or vertebral artery or both, depending on the areas of vasospasm. The effect was controlled via multimodal neuromonitoring and transcranial Doppler sonography. Outcome was determined by means of the Glasgow Outcome Scale at discharge and 6 months after the hemorrhage and compared to a historical control group.

RESULTS

Twenty-one patients received 28 intra-arterial nimodipine infusions. Six months after discharge, the occurrence of cerebral infarctions was significantly lower (42.6 %) in the nimodipine group than in the control group (75.0 %). This result was reflected by a significantly higher proportion (76.0 %) of patients with good outcome in the nimodipine-treated group, when compared to 10.0 % good outcome in the control group. Median GOS was 4 in the nimodipine group and 2 in the control group (p = 0.001).

CONCLUSIONS

Continuous intra-arterial nimodipine infusion is an effective treatment for patients with severe cerebral vasospasm who fail to respond to HHT and oral nimodipine alone. Key to the effective administration of continuous intra-arterial nimodipine is multimodal neuromonitoring and the individual adaptation of dosage and time of infusion for each patient.

Nitric oxide in cerebral vasospasm: theories, measurement, and treatment

In recent decades, a large body of research has focused on the role of nitric oxide (NO) in the development of cerebral vasospasm (CV) following subarachnoid hemorrhage (SAH). Literature searches were therefore conducted regarding the role of NO in cerebral vasospasm, specifically focusing on NO donors, reactive nitrogen species, and peroxynitrite in manifestation of vasospasm. Based off the assessment of available evidence, two competing theories are reviewed regarding the role of NO in vasospasm. One school of thought describes a deficiency in NO due to scavenging by hemoglobin in the cisternal space, leading to an NO signaling deficit and vasospastic collapse. A second hypothesis focuses on the dysfunction of nitric oxide synthase, an enzyme that synthesizes NO, and subsequent generation of reactive nitrogen species. Both theories have strong experimental evidence behind them and hold promise for translation into clinical practice. Furthermore, NO donors show definitive promise for preventing vasospasm at the angiographic and clinical level. However, NO augmentation may also cause systemic hypotension and worsen vasospasm due to oxidative distress. Recent evidence indicates that targeting NOS dysfunction, for example, through erythropoietin or statin administration, also shows promise at preventing vasospasm and neurotoxicity. Ultimately, the role of NO in neurovascular disease is complex. Neither of these theories is mutually exclusive, and both should be considered for future research directions and treatment strategies.

Continuous intrathecal glyceryl trinitrate prevents delayed cerebral vasospasm in the single-SAH rabbit model in vivo

BACKGROUND

Delayed cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH) is a major cause of high morbidity and mortality. The reduced availability of nitric oxide (NO) in blood and cerebrospinal fluid (CSF) is well established as a key mechanism of vasospasm. Systemic administration of glyceryl trinitrate (GTN), an NO donor also known as nitroglycerin, has failed to be established in clinical settings to prevent vasospasm because of its adverse effects, particularly hypotension. The purpose of this study was to analyze the effect of intrathecally administered GTN on vasospasm after experimental SAH in the rabbit basilar artery.

METHODS

A single-hemorrhage model of SAH in rabbits was used to induce vasospasm. GTN (0.5 mg/ml) or saline was infused via a subcutaneous implanted osmotic pump with continuous drug release into the cerebellomedullary cistern over 5 days. The degree of vasospasm in the basilar artery was recorded with angiography on day 5 after SAH and was compared to baseline angiography on day 0.

FINDINGS

Significant reduction of basilar artery diameter was observed in the SAH group with saline infusion compared to sham-operated animals. Intrathecally administered GTN had no effect on the vessel diameter in sham-operated animals, whereas it significantly prevented vasospasm in the SAH group. Intrathecal GTN infusion did not affect arterial blood pressure.

CONCLUSIONS

Prophylactic, continuous intrathecal administration of GTN prevents vasospasm of the basilar artery in the rabbit SAH model. No toxic effects could be demonstrated in this study. The clinical safety and feasibility of this strategy need to be further investigated.

Subarachnoid hemorrhage and the distribution of drugs delivered into the cerebrospinal fluid. Laboratory investigation

OBJECT

Investigators in experimental and clinical studies have used the intrathecal route to deliver drugs to prevent or treat vasospasm. However, a clot near an artery or arteries after subarachnoid hemorrhage (SAH) may hamper distribution and limit the effects of intrathecally delivered compounds. In a primate model of right middle cerebral artery (MCA) SAH, the authors examined the distribution of Isovue-M 300 and 3% Evans blue after infusion into the cisterna magna CSF.

METHODS

Ten cynomolgus monkeys were assigned to SAH and sham SAH surgery groups (5 in each group). Monkeys received CSF injections as long as 28 days after SAH and were killed 3 hours after the contrast/Evans blue injection. The authors assessed the distribution of contrast material on serial CT within 2 hours after contrast injection and during autopsy within 3 hours after Evans blue staining.

RESULTS

Computed tomography cisternographies showed no contrast in the vicinity of the right MCA (p < 0.05 compared with left); the distribution of contrast surrounding the entire right cerebral hemisphere was substantially reduced. Postmortem analysis demonstrated much less Evans blue staining of the right hemisphere surface compared with the left. Furthermore, the Evans blue dye did not penetrate into the right sylvian fissure, which occurred surrounding the left MCA. The authors observed the same pattern of changes and differences in contrast distribution between SAH and sham SAH animals and between the right and the left hemispheres on Days 1, 3, 7, 14, 21, and 28 after SAH.

CONCLUSIONS

Intrathecal drug distribution is substantially limited by SAH. Thus, when using intrathecal drug delivery after SAH, vasoactive drugs are unlikely to reach the arteries that are at the highest risk of delayed cerebral vasospasm.

Role of transcranial Doppler in neurocritical care

Transcranial Doppler has several practical applications in neurocritical care. It has its main application in the diagnosis and monitoring of vasospasm in patients with subarachnoid hemorrhage. In addition, it holds promise for the detection of critical elevations of intracranial pressure. Its ability to measure CO2 reactivity and autoregulation may ultimately allow intensivists to optimize cerebral perfusion pressure and ventilatory therapy for the individual patient. Transcranial Doppler findings of brain death are well described and can be useful as a screening tool.