Prostacyclin treatment normalises the MCA flow velocity in nimodipine-resistant cerebral vasospasm after aneurysmal subarachnoid haemorrhage: a pilot study

The Updated Role of the Blood Brain Barrier in Subarachnoid Hemorrhage: From Basic and Clinical Studies

Subarachnoid hemorrhage (SAH) is a type of hemorrhagic stroke associated with high mortality and morbidity. The blood-brain-barrier (BBB) is a structure consisting primarily of cerebral microvascular endothelial cells, end feet of astrocytes, extracellular matrix, and pericytes. Post-SAH pathophysiology included early brain injury and delayed cerebral ischemia. BBB disruption was a critical mechanism of early brain injury and was associated with other pathophysiological events. These pathophysiological events may propel the development of secondary brain injury, known as delayed cerebral ischemia. Imaging advancements to measure BBB after SAH primarily focused on exploring innovative methods to predict clinical outcome, delayed cerebral ischemia, and delayed infarction related to delayed cerebral ischemia in acute periods. These predictions are based on detecting abnormal changes in BBB permeability. The parameters of BBB permeability are described by changes in computed tomography (CT) perfusion and magnetic resonance imaging (MRI). K_ep seems to be a stable and sensitive indicator in CT perfusion, whereas K^trans is a reliable parameter for dynamic contrast-enhanced MRI. Future prediction models that utilize both the volume of BBB disruption and stable parameters of BBB may be a promising direction to develop practical clinical tools. These tools could provide greater accuracy in predicting clinical outcome and risk of deterioration. Therapeutic interventional exploration targeting BBB disruption is also promising, considering the extended duration of post-SAH BBB disruption.

Prostacyclin Affects the Relation Between Brain Interstitial Glycerol and Cerebrovascular Pressure Reactivity in Severe Traumatic Brain Injury

Background

Cerebral injury may alter the autoregulation of cerebral blood flow. One index for describing cerebrovascular state is the pressure reactivity (PR). Little is known of whether PR is associated with measures of brain metabolism and indicators of ischemia and cell damage. The aim of this investigation was to explore whether increased interstitial levels of glycerol, a marker of cell membrane damage, are associated with PR, and if prostacyclin, a membrane stabilizer and regulator of the microcirculation, may affect this association in a beneficial way.

Materials and Methods

Patients suffering severe traumatic brain injury (sTBI) were treated according to an intracranial pressure (ICP)-targeted therapy based on the Lund concept and randomized to an add-on treatment with prostacyclin or placebo. Inclusion criteria were verified blunt head trauma, Glasgow Coma Score ≤ 8, age 15–70 years, and a first measured cerebral perfusion pressure of ≥ 10 mmHg. Multimodal monitoring was applied. A brain microdialysis catheter was placed on the worst affected side, close to the penumbra zone. Mean (glycerol_mean) and maximal glycerol (glycerol_max) during the 96-h sampling period were calculated. The mean PR was calculated as the ICP/mean arterial pressure (MAP) regression coefficient based on hourly mean ICP and MAP during the first 96 h.

Results

Of the 48 included patients, 45 had valid glycerol and PR measurements available. PR was higher in the placebo group as compared to the prostacyclin group (p = 0.0164). There was a positive correlation between PR and the glycerol_mean (ρ = 0.503, p = 0.01) and glycerol_max (ρ = 0.490, p = 0.015) levels in the placebo group only.

Conclusions

PR is correlated to the glycerol level in patients suffering from sTBI, a relationship that is not seen in the group treated with prostacyclin. Glycerol has been associated with membrane degradation and may support glycerol as a biomarker for vascular endothelial breakdown. Such a breakdown may impair the regulation of cerebrovascular PR.

Cerebral vasospasm: current understanding

PURPOSE OF REVIEW

With recent research trying to explore the pathophysiologic mechanisms behind vasospasm, newer pharmacological and nonpharmacological treatments are being targeted at various pathways involved. This review is aimed at understanding the mechanisms and current and future therapies available to treat vasospasm.

RECENT FINDINGS

Computed tomography perfusion is a useful alternative tool to digital subtraction angiography to diagnose vasospasm. Various biomarkers have been tried to predict the onset of vasospasm but none seems to be helpful. Transcranial Doppler still remains a useful tool at the bedside to screen and follow up patients with vasospasm. Hypertension rather than hypervolemia and hemodilution in 'Triple-H' therapy has been found to be helpful in reversing the vasospasm. Hyperdynamic therapy in addition to hypertension has shown promising effects. Endovascular approaches with balloon angioplasty and intra-arterial nimodipine, nicardipine, and milrinone have shown consistent benefits. Endothelin receptor antagonists though relieved vasospasm, did not show any benefit on functional outcome.

SUMMARY

Endovascular therapy has shown consistent benefit in relieving vasospasm. An aggressive combination therapy through various routes seems to be the most useful approach to reduce the complications of vasospasm.

Vasomodulatory effects of the angiotensin II type 1 receptor antagonist losartan on experimentally induced cerebral vasospasm after subarachnoid haemorrhage

BACKGROUND

Cerebral vasospasm following subarachnoid haemorrhage (SAH) remains one of the major factors contributing to poor overall patient outcome. Prostaglandin F2-alpha (PGF2a) induces vasoconstriction. After SAH, PGF2a leads to cerebral inflammation and enhanced vasoconstriction, resulting in cerebral vasospasm. Losartan is already known to have beneficial effects in stroke models and also on several cerebral inflammatory processes. Therefore, the aim of the study was to analyse the effect of losartan on PGF2a-enhanced vasoconstriction after SAH.

METHODS

To investigate the effect of losartan on PGF2a-enhanced vasoconstriction after SAH, cerebral vasospasm was induced by a double-haemorrhage model. Rats were killed on day 3 and 5 after SAH followed by measurement of the isometric force of basilar artery ring segments in an organ bath.

RESULTS

PGF2a induced a dose-dependent contraction. After pre-incubation with losartan, the maximum contraction (E_max) for sham-operated animals was significantly lowered [E_max 6% in losartan 3 × 10^-4 molar (M) vs. 56% without losartan]. Also, after induced SAH, PGF2a induced no vasoconstriction in pre-incubated vessels with losartan 3 × 10^-4 M on day 3 (d3) as well as on day 5 (d5). For the vasorelaxative investigations, vessel segments were pre-incubated with PFG2a. Cumulative application of losartan completely resolved the pre-contraction in sham-operated animals (non SAH: 95% relaxation). After SAH, losartan not only resolved the pre-contraction (d5: 103%), but also exceeded the pre-contraction (d3: 119%). Therefore, a statistically significantly increased and earlier relaxation was calculated for all losartan concentrations [E_max (d3/d5) and pD₂ (d3/d5)] compared with the solvent control group.

CONCLUSION

In a physiological and pathophysiological setup, losartan reduces a PGF2-induced vasoconstriction and reverses a PGF2a-precontraction completely. This fact can be integrated in pushing forward further concepts trying to antagonise/prevent cerebral vasospasm after SAH.

Effect of delayed onset prostacyclin on markers of endothelial function and damage after subarachnoid hemorrhage

BACKGROUND

Subarachnoid hemorrhage (SAH) is a neurological emergency. Delayed ischemic neurological deficit is one of the main causes of poor outcome after SAH and is probably caused, at least in part, by cerebral vasospasm. The pathophysiology of this is multifaceted, but endothelial damage and activation as well as glycocalyx damage have been implicated. Prostacyclin has been shown to protect damaged and activated endothelium and to facilitate glycocalyx repair. We investigated biomarkers of endothelial activation and damage in patients with SAH randomized to 5 days prostacyclin infusion or placebo.

METHODS

Patients with aneurysmal SAH managed by coiling or surgery, and a World Federation of Neurological Surgeons score between 1 and 4, and Fisher grade 3 or 4, were treated with a continuous low-dose intravenous prostacyclin infusion or placebo initiated on day 5 and discontinued on day 10 after SAH. Blood samples were drawn from the patients before, during and after prostacyclin/placebo infusion. Soluble biomarkers of endothelial cell activation (sE-selectin, sVE-cadherin) and damage (sTM), glycocalyx damage (syndecan-1) and sympathoadrenal activation (adrenaline, noradrenaline), were measured by ELISA.

RESULTS

Ninety patients were randomized. Prostacyclin infusion influenced neither biomarkers of sympathoadrenal activation, endothelial activation and damage nor biomarkers of endothelial glycocalyx breakdown.

CONCLUSIONS

We did not find any effects on markers of sympathoadrenal activation, endothelial damage and activation, or glycocalyx degradation of delayed onset prostacyclin infusion compared to placebo. Further trials investigating early onset endothelial repair using prostacyclin are warranted.

Levosimendan, a new therapeutic approach to prevent delayed cerebral vasospasm after subarachnoid hemorrhage?

BACKGROUND

Under physiological cerebral conditions, levosimendan, a calcium-channel sensitizer, has a dose-dependent antagonistic effect on prostaglandin F2alpha (PGF)-induced vasoconstriction. This circumstance could be used in antagonizing delayed cerebral vasospasm (dCVS), one of the main complications after subarachnoid hemorrhage (SAH), leading to delayed cerebral ischemia and ischemic neurological deficits. Data already exist that identified neuroprotective effects of levosimendan in a traumatic brain injury model and additionally, it has been proven that this compound prevents narrowing of the basilar artery (BA) luminal area after SAH in an in vitro rabbit model. Takotsubo cardiomyopathy, a severe ventricular dysfunction, is also a well-known complication after SAH, associated with pulmonary edema and prolonged intubation.

METHODS

The polypeptide endothelin-1 (ET-1) plays a key role in the development of dCVS after SAH. Therefore, the aim of the present investigation was to detect functional interactions between the calcium-sensitizing and the ET-1-dependent vasoconstriction after experimental-induced SAH; interactions between levosimendan and a substrate-specific vasorelaxation in the BA were also examined. It was reviewed whether levosimendan has a beneficial influence on endothelin(A) and/or endothelin(B₁) receptors (ET-(A) and ET-(B₁) receptors) in cerebral vessels after SAH. We also examined whether this drug could have antagonistic effects on a PGF-induced vasoconstriction.

RESULTS

Under treatment with levosimendan after SAH, the endothelin system seems to be affected. The ET-1-induced contraction is decreased, not significantly. In addition, we detected changes in the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway. Preincubation with levosimendan causes a modulatory effect on the ET-(B₁) receptor-dependent vasorelaxation. It induces an upregulation of the NO-cGMP pathway with a significantly increased relaxation. Even after PGF-induced precontraction a dose-dependent relaxation was registered, which was significantly higher (E_max) and earlier (pD₂) compared to the concentration-effect curve without levosimendan.

CONCLUSIONS

After experimental-induced dCVS, levosimendan seems to restore the well-known impaired function of the vasorelaxant ET-(B₁) receptor. Levosimendan also reversed the PGF-induced contraction dose-dependently. Both of these mechanisms could be used for antagonizing dCVS in patients suffering SAH. Levosimendan could even be used additionally in treating patients developing takotsubo cardiomyopathy.

Prostacyclin influences the pressure reactivity in patients with severe traumatic brain injury treated with an ICP-targeted therapy

BACKGROUND

This prospective consecutive double-blinded randomized study investigated the effect of prostacyclin on pressure reactivity (PR) in severe traumatic brain injured patients. Other aims were to describe PR over time and its relation to outcome.

METHODS

Blunt head trauma patients, Glasgow coma scale ≤8, age 15-70 years were included and randomized to prostacyclin treatment (n = 23) or placebo (n = 25). Outcome was assessed using the extended Glasgow outcome scale (GOSE) at 3 months. PR was calculated as the regression coefficient between the hourly mean values of ICP versus MAP. Pressure active/stable was defined as PR ≤0.

RESULTS

Mean PR over 96 h (PRtot) was 0.077 ± 0.168, in the prostacyclin group 0.030 ± 0.153 and in the placebo group 0.120 ± 0.173 (p < 0.02). There was a larger portion of pressure-active/stable patients in the prostacyclin group than in the placebo group (p < 0.05). Intra-individual changes over time were common. PRtot correlated negatively with GOSE score (p < 0.04). PRtot was 0.117 ± 0.182 in the unfavorable (GOSE 1-4) and 0.029 ± 0.140 in the favorable outcome group (GOSE 5-8). Area under the curve for prediction of death (ROC) was 0.742 and for favorable outcome 0.628.

CONCLUSIONS

Prostacyclin influenced the PR in a direction of increased pressure stability and a lower PRtot was associated with improved outcome. The individual PR varied substantially over time. The predictive value of PRtot for outcome was not solid enough to be used in the clinical situation.

Endothelin-1-mediated vasoconstriction alters cerebral gene expression in iron homeostasis and eicosanoid metabolism

Endothelins are potent vasoconstrictors and signaling molecules. Their effects are broad, impacting processes ranging from neurovascular and cardiovascular health to cell migration and survival. In stroke, traumatic brain injury or subarachnoid hemorrhage, endothelin-1 (ET-1) is induced resulting in cerebral vasospasm, ischemia, reperfusion and the activation of various pathways. Given the central role that ET-1 plays in these patients and to identify the downstream molecular events specific to transient vasoconstriction, we studied the consequences of ET-1-mediated vasoconstriction of the middle cerebral artery in a rat model. Our observations demonstrate that ET-1 can lead to increases in gene expression, including genes associated with the inflammatory response (Ifnb, Il6, Tnf) and oxidative stress (Hif1a, Myc, Sod2). We also observed inductions (>2 fold) of genes involved in eicosanoid biosynthesis (Pla2g4a, Pla2g4b, Ptgs2, Ptgis, Alox12, Alox15), heme metabolism (Hpx, Hmox1, Prdx1) and iron homeostasis (Hamp, Tf). Our findings demonstrate that mRNA levels for the hormone hepcidin (Hamp) are induced in the brain in response to ET-1, providing a novel target in the treatment of multiple conditions. These changes on the ipsilateral side were also accompanied by corresponding changes in a subset of genes in the contralateral hemisphere. Understanding ET-1-mediated events at the molecular level may lead to better treatments for neurological diseases and provide significant impact on neurological function, morbidity and mortality.

Cerebral hemodynamics: concepts of clinical importance

Cerebral hemodynamics and metabolism are frequently impaired in a wide range of neurological diseases, including traumatic brain injury and stroke, with several pathophysiological mechanisms of injury. The resultant uncoupling of cerebral blood flow and metabolism can trigger secondary brain lesions, particularly in early phases, consequently worsening the patient's outcome. Cerebral blood flow regulation is influenced by blood gas content, blood viscosity, body temperature, cardiac output, altitude, cerebrovascular autoregulation, and neurovascular coupling, mediated by chemical agents such as nitric oxide (NO), carbon monoxide (CO), eicosanoid products, oxygen-derived free radicals, endothelins, K+, H+, and adenosine. A better understanding of these factors is valuable for the management of neurocritical care patients. The assessment of both cerebral hemodynamics and metabolism in the acute phase of neurocritical care conditions may contribute to a more effective planning of therapeutic strategies for reducing secondary brain lesions. In this review, the authors have discussed concepts of cerebral hemodynamics, considering aspects of clinical importance.

The effects of continuous prostacyclin infusion on regional blood flow and cerebral vasospasm following subarachnoid haemorrhage: study protocol for a randomised controlled trial

BACKGROUND

One of the main causes of mortality and morbidity following subarachnoid haemorrhage (SAH) is the development of cerebral vasospasm, a frequent complication arising in the weeks after the initial bleeding. Despite extensive research, to date no effective treatment of vasospasm exists. Prostacyclin is a potent vasodilator and inhibitor of platelet aggregation. In vitro models have shown a relaxing effect of prostacyclin after induced contraction in cerebral arteries, and a recent pilot trial showed a positive effect on cerebral vasospasm in a clinical setting. No randomised, clinical trials have been conducted, investigating the possible pharmacodynamic effects of prostacyclin on the human brain following SAH.

METHODS

This trial is a single-centre, randomised, placebo-controlled, parallel group, blinded, clinical, pilot trial. A total of 90 patients with SAH will be randomised to one of three intervention arms: epoprostenol 1 ng/kg/min, epoprostenol 2 ng/kg/min or placebo in addition to standard treatment. Trial medication will start day 5 after SAH and continue to day 10. The primary outcome measure is changes in regional cerebral blood flow from baseline in the arterial territories of the anterior cerebral artery, medial cerebral artery and the posterior cerebral artery, measured by CT perfusion scan. The secondary outcomes will be vasospasm measured by CT angiography, ischaemic parameters measured by brain microdialysis, flow velocities in the medial cerebral artery, clinical parameters and outcome (Glasgow Outcome Scale) at 3 months.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01447095.

Advances in treatment of cerebral vasospasm: an update

An update of published clinical advances in the treatment of cerebral vasospasm after subarachnoid haemorrhage was provided. Searching MEDLINE using the search terms "cerebral vasospasm" and "clinical trials" 46 papers were identified that had been published since the International Conference on Cerebral Vasospasm in Istanbul, Turkey in 2006. Of these 26 were either safety studies or case reports leaving 20 papers for consideration. The major topics covered were calcium antagonists, magnesium sulphate, statins, and fasudil hydrochloride. The studies published did not reach an impact justified recommended routine use, but certainly as options. Results of the CONSCIOUS trials on endothelin receptor antagonists are awaited.