Dose optimization of intravenous magnesium sulfate after acute stroke

Research hotpots and frontier trends of neuroprotective effects of magnesium from 1999 to 2023: A bibliometric analysis

BACKGROUND

The neuroprotective effect of magnesium has been widely discussed, and its effectiveness has been confirmed by animal and clinical trials. However, there are still difficulties in clinical translation in diseases such as cerebral ischemia and subarachnoid hemorrhage. Therefore, it is necessary to analyze the literatures about neuroprotection of magnesium to reveal a more comprehensive knowledge framework, research hotspots and trends in the future.

METHODS

Original articles and reviews related to neuroprotective effects of magnesium from 1999 to 2022 were retrieved from the Web of Science Core Collection (WoSCC). The bibliometrics CiteSpace 6.2.R4 software was used to conduct co-occurrence/co-citation network analysis and plot knowledge visualization maps.

RESULTS

A total of 762 articles from 216 institutions in 64 countries were included in this study. The United States had the largest number of publications, followed by China and Canada. The University of California, UDICE-French Research Universities, and the University of Adelaide were the top three institutions in publication volume. Crowther Caroline A was the most published and cited author. Among the top 10 cited articles, there were seven articles on neuroprotection in preterm infants and three on acute stroke. Keyword cluster analysis obtained 11 clusters, showing that current research hotspots focused on magnesium therapy in neurovascular diseases such as cerebral ischemia, spinal cord injury, subarachnoid hemorrhage, and emerging treatment strategies.

CONCLUSION

The neuroprotective effects of magnesium in preterm infants have been extensively studied and adequately confirmed. The therapeutic effects of magnesium on cerebral ischemia and subarachnoid hemorrhage have been demonstrated in animal models. However, the results of clinical studies were not satisfactory, and exploring new therapeutic strategies may be the solution. Recently, the combination of magnesium and hypothermia had great potential in neuroprotective therapy and may become a development trend and hotspot in the future.

Effects of intravenous administration of magnesium sulfate in propofol-based sedation for ERCP in elderly patients: a randomized, double-blind, placebo-controlled study

BACKGROUND

Propofol-based sedations are widely used in elderly patients for endoscopic retrograde cholangiopancreatography (ERCP) procedure, but respiratory depression and cardiovascular adverse events commonly occur. Magnesium administered intravenously can alleviate pain and decrease propofol requirements during surgery. We hypothesized that intravenous magnesium was used as adjuvant to propofol might be beneficial in elderly patients undergoing ERCP procedures.

METHODS

Eighty patients aged from 65 to 79 years who were scheduled for ERCP were enrolled. All patients were intravenously administered 0.1 µg/kg sufentanil as premedication. The patients were randomized to receive either intravenous magnesium sulfate 40 mg/kg (group M, n = 40) or the same volume of normal saline (group N, n = 40) over 15 min before the start of sedation. Intraoperative sedation was provided by propofol. Total propofol requirement during ERCP was the primary outcome.

RESULTS

The total propofol consumption were reduced by 21.4% in the group M compared with the group N (151.2 ± 53.3 mg vs. 192.3 ± 72.1 mg, P = 0.001). The incidences of respiratory depression episodes and involuntary movement were less in the group M than those in the group N (0/40 vs. 6/40, P = 0.011; 4/40 vs. 11/40, P = 0.045; respectively). In the group M, the patients experienced less pain than those in the group N at 30 min after the procedure (1 [0-1] vs. 2 [1-2], P < 0.001). Correspondingly, the patients' satisfaction was clearly higher in the group M (P = 0.005). There was a tendency towards lower intraoperative heart rate and mean arterial pressure in group M.

CONCLUSIONS

A single bolus of 40 mg/kg of intravenous magnesium can significantly reduce propofol consumption during ERCP, with higher sedation success and lower adverse events.

TRIAL REGISTRATION

ID UMIN000044737. Registered 02/07/2021.

Current status and outlook of potential applications of biodegradable materials in cerebral vascular stents

The treatment of intracranial aneurysms (IAs) has undergone a very significant transformation in recent decades, and endovascular interventions have gradually become one of the most common treatments. As permanent metal stents can cause some degree of long-term damage to patients, biodegradable stent materials are emerging as attractive potential alternatives. By reviewing the current research status and the advantages and disadvantages of existing biodegradable biomaterials, this review expects to provide a valuable reference for subsequent research on biodegradable biomaterials.

Rapid Treatment with Intramuscular Magnesium Sulfate During Cardiopulmonary Resuscitation Does Not Provide Neuroprotection Following Cardiac Arrest

Brain injury is the most common cause of death for patients resuscitated from cardiac arrest. Magnesium is an attractive neuroprotective compound which protects neurons from ischemic injury by reducing neuronal calcium overload via NMDA receptor modulation and preventing calcium-induced mitochondrial permeability transition. Intramuscular (IM) delivery of MgSO₄ during CPR has the potential to target these mechanisms within an early therapeutic window. We hypothesize that IM MgSO₄ administrated during CPR could achieve therapeutic serum magnesium levels within 15 min after ROSC and improve neurologic outcomes in a rat model of asphyxial cardiac arrest. Male Long Evans rats were subjected to 8-min asphyxial cardiac arrest and block randomized to receive placebo, 107 mg/kg, 215 mg/kg, or 430 mg/kg MgSO₄ IM at the onset of CPR. Serum magnesium concentrations increased rapidly with IM delivery during CPR, achieving twofold to fourfold increase by 15 min after ROSC in all magnesium dose groups. Rats subjected to cardiac arrest or sham surgery were block randomized to treatment groups for assessment of neurological outcomes. We found that IM MgSO₄ during CPR had no effect on ROSC rate (p > 0.05). IM MgSO₄ treatment had no statistically significant effect on 10-day survival with good neurologic function or hippocampal CA1 pyramidal neuron survival compared to placebo treatment. In conclusion, a single dose IM MgSO₄ during CPR achieves up to fourfold baseline serum magnesium levels within 15 min after ROSC; however, this treatment strategy did not improve survival, recovery of neurologic function, or neuron survival. Future studies with repeated dosing or in combination with hypothermic targeted temperature management may be indicated.

Current status and outlook of biodegradable metals in neuroscience and their potential applications as cerebral vascular stent materials

Over the past two decades, biodegradable metals (BMs) have emerged as promising materials to fabricate temporary biomedical devices, with the purpose of avoiding potential side effects of permanent implants. In this review, we first surveyed the current status of BMs in neuroscience, and briefly summarized the representative stents for treating vascular stenosis. Then, inspired by the convincing clinical evidence on the in vivo safety of Mg alloys as cardiovascular stents, we analyzed the possibility of producing biodegradable cerebrovascular Mg alloy stents for treating ischemic stroke. For these novel applications, some key factors should also be considered in designing BM brain stents, including the anatomic features of the cerebral vasculature, hemodynamic influences, neuro-cytocompatibility and selection of alloying elements. This work may provide insights into the future design and fabrication of BM neurological devices, especially for brain stents.

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The current status of the application of biodegradable metals (BM) in neuroscience was presented.

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We analyzed the possibility of producing biodegradable cerebrovascular Mg alloy stents for ischemic stroke treatment.

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Key factors in designing BM brain stents were discussed.

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This work may provide insights into the future design and fabrication of BM neurological devices, especially for brain stents.

Collateral Circulation Augmentation and Neuroprotection as Adjuvant to Mechanical Thrombectomy in Acute Ischemic Stroke

PURPOSE OF THE REVIEW

Mechanical thrombectomy (MT)-mediated endovascular recanalization has dramatically transformed treatment and outcomes after acute ischemic stroke caused by a large vessel occlusion (LVO). Current guidelines recommend MT up to 24 hours from stroke onset in carefully selected patients based on favorable clinical and imaging parameters. Despite optimal patient selection and low complication rates with current recanalization technology, approximately 1 in 2 patients with LVO stroke do not achieve functional independence at 3 months. This ceiling effect of MT efficacy may be explained by ischemic core expansion into the ischemic penumbra before recanalization and neuronal loss occurring after recanalization. Factors affecting the efficacy of MT, or the degree of irreversible injury, include time from symptom onset to recanalization, collateral circulation status, and differences in neuronal vulnerability. The purpose of this brief review is to discuss potential targets for neuroprotection, present and future potential pharmacologic and nonpharmacologic agents, and the data available in the literature.

RECENT FINDINGS

In experimental ischemia models, several authors reported that pharmacologic and nonpharmacologic agents are able to slow the progression of ischemic core expansion. However, in the era of unsuccessful recanalization of the occluded artery, several neuroprotective agents that were promising in the preclinical stage failed phase II/III clinical trials.

SUMMARY

Providing neuroprotection before and after recanalization of an LVO may play an important role in improving outcomes in the era of MT. Neuroprotection is classically defined as a process that results in the salvage, recovery, or regeneration of neuronal (and other supporting CNS cell) structure or function. The advent of successful recanalization of acute LVO by MT in the majority of patients may spur the growth of effective neuroprotection.

Neuroprotective effect of magnesium supplementation on cerebral ischemic diseases

Ischemic encephalopathy is associated with a high mortality and rate of disability. The most common type of ischemic encephalopathy, ischemic stroke, is the second leading cause of death in the world. At present, the main treatment for ischemic stroke is to reopen blocked blood vessels. However, despite revascularization, many patients are not able to achieve good functional results. At the same time, the strict time window (<4.5 h) of thrombolytic therapy limits clinical application. Therefore, it is important to explore effective neuroprotective drugs for the treatment of ischemic stroke. Magnesium is a natural calcium antagonist, which exerts neuroprotective effects through various mechanisms. However, while most basic studies have shown that magnesium supplementation can help treat cerebral ischemia, intravenous magnesium supplementation in large clinical trials has failed to improve prognosis of ischemic patients. Therefore, we review the basic and clinical studies of magnesium supplementation for cerebral ischemia. According to the route of administration, treatment can be divided into intraperitoneal magnesium supplementation, intravenous magnesium supplementation, arterial magnesium supplementation and intracranial magnesium supplementation. We also summarized the potential influencing factors of magnesium ion intervention in cerebral ischemia injury. Finally, in combination with influencing factors derived from basic research, this article proposes three future research directions, including magnesium supplementation into the circulatory system combined with magnesium supplementation in the lateral ventricle, magnesium supplementation in the lateral ventricle combined with hypothermia therapy, and lateral ventricle magnesium supplementation combined with intracarotid magnesium supplementation combined with selective hypothermia.

Magnesium and Bladder Discomfort after Transurethral Resection of Bladder Tumor

Background

Catheter-related bladder discomfort occurs because of involuntary contractions of the bladder smooth muscle after urinary catheterization. Magnesium is associated with smooth muscle relaxation. This study hypothesized that among patients having transurethral resection of bladder tumor, magnesium will reduce the incidence of postoperative moderate-to-severe catheter-related bladder discomfort.

Methods

In this double-blind, randomized study, patients were randomly allocated to the magnesium group (n = 60) or the control group (n = 60). In magnesium group, a 50 mg/kg loading dose of intravenous magnesium sulfate was administered for 15 min, followed by an intravenous infusion of 15 mg · kg−1 · h−1 during the intraoperative period. Patients in the control group similarly received normal saline. The primary outcome was the incidence of catheter-related bladder discomfort above a moderate grade at 0 h postoperatively. None, mild, moderate, and severe catheter-related bladder discomfort at 1, 2, and 6 h postoperatively, patient satisfaction, and magnesium-related adverse effects were also assessed.

Results

The incidence of catheter-related bladder discomfort above a moderate grade at 0 h postoperatively was significantly lower in the magnesium group than in the control group (13 [22%] vs. 46 [77%]; P &lt; 0.001; relative risk = 0.283; 95% CI, 0.171 to 0.467; absolute risk reduction = 0.55; number needed to treat = 2); similar results were observed for catheter-related bladder discomfort above a moderate grade at 1 and 2 h postoperatively (5 [8%] vs. 17 [28%]; P = 0.005; relative risk = 0.294; 95% CI, 0.116 to 0.746; and 1 [2%] vs. 14 [23%]; P &lt; 0.001; relative risk = 0.071; 95% CI, 0.010 to 0.526, respectively). Patient satisfaction on a scale from 1 to 7 was significantly higher in the magnesium group than in the control group (5.1 ± 0.8 vs. 3.5 ± 1.0; P &lt; 0.001; 95% CI, 1.281 to 1.919). Magnesium-related adverse effects were not significantly different between groups.

Conclusions

Magnesium reduced the incidence of catheter-related bladder discomfort above a moderate grade and increased patient satisfaction among patients having transurethral resection of bladder tumor.

Editor’s Perspective

What We Already Know about This Topic

What This Article Tells Us That Is New

Treatment Approaches to Lacunar Stroke

Lacunar strokes are appropriately named for their ability to cavitate and form ponds or "little lakes" (Latin: lacune -ae meaning pond or pit is a diminutive form of lacus meaning lake). They account for a substantial proportion of both symptomatic and asymptomatic ischemic strokes. In recent years, there have been several advances in the management of large vessel occlusions. New therapies such as non-vitamin K antagonist oral anticoagulants and left atrial appendage closure have recently been developed to improve stroke prevention in atrial fibrillation; however, the treatment of small vessel disease-related strokes lags frustratingly behind. Since Fisher characterized the lacunar syndromes and associated infarcts in the late 1960s, there have been no therapies specifically targeting lacunar stroke. Unfortunately, many therapeutic agents used for the treatment of ischemic stroke in general offer only a modest benefit in reducing recurrent stroke while adding to the risk of intracerebral hemorrhage and systemic bleeding. Escalation of antithrombotic treatments beyond standard single antiplatelet agents has not been effective in long-term lacunar stroke prevention efforts, unequivocally increasing intracerebral hemorrhage risk without providing a significant benefit. In this review, we critically review the available treatments for lacunar stroke based on evidence from clinical trials. For several of the major drugs, we summarize the adverse effects in the context of this unique patient population. We also discuss the role of neuroprotective therapies and neural repair strategies as they may relate to recovery from lacunar stroke.

Blood Pressure and Penumbral Sustenance in Stroke from Large Vessel Occlusion

The global burden of stroke remains high, and of the various subtypes of stroke, large vessel occlusions (LVOs) account for the largest proportion of stroke-related death and disability. Several randomized controlled trials in 2015 changed the landscape of stroke care worldwide, with endovascular thrombectomy (ET) now the standard of care for all eligible patients. With the proven success of this therapy, there is a renewed focus on penumbral sustenance. In this review, we describe the ischemic penumbra, collateral circulation, autoregulation, and imaging assessment of the penumbra. Blood pressure goals in acute stroke remain controversial, and we review the current data and suggest an approach for induced hypertension in the acute treatment of patients with LVOs. Finally, in addition to reperfusion and enhanced perfusion, efforts focused on developing therapeutic targets that afford neuroprotection and augment neural repair will gain increasing importance. ET has revolutionized stroke care, and future emphasis will be placed on promoting penumbral sustenance, which will increase patient eligibility for this highly effective therapy and reduce overall stroke-related death and disability.

The effects of magnesium sulfate therapy after severe diffuse axonal injury

Purpose

To evaluate the clinical effects of magnesium sulfate in the treatment of diffuse axonal injury (DAI).

Patients and methods

This study was a randomized, double-blind, placebo-controlled trial conducted in the First Affiliated Hospital of Sun Yat-sen University, Guangzhou and Zhuhai People’s Hospital, Zhuhai, two trauma center hospitals. A total of 128 patients suffered from DAI, with initial Glasgow coma scale (GCS) scores of 3–8. They were randomly divided into two groups: magnesium sulfate treatment (MST) group (n=64) and control group (n=64). The MST group received 250 μmol/kg magnesium sulfate intravenously 20 minutes after admission, followed by 750 μmol/kg magnesium sulfate intravenously daily for 5 days. The control group received standard management without MST. GCS scores and serum neuron-specific enolase values were measured and recorded at admission, and on days 3 and 7 after injury. Outcomes were determined by Glasgow outcome scale scores at discharge and at 3 months’ follow-up, respectively.

Results

After the 7-day treatment, patients in the MST group, compared with those in the control group, had a lower serum neuron-specific enolase level (25.40±6.66 vs 29.58±7.32, respectively, P=0.001) and higher GCS score (8.23±2.72 vs 7.05±2.64, respectively, P=0.016). Although the length of stay and mortality did not differ between the groups in the intensive care unit, Glasgow outcome scale score was significantly lower in the MST group at discharge (3.30±1.35 vs 3.90±1.10, P=0.004) and 3 months after discharge (2.95±1.48 vs 3.66±1.44, P=0.009).

Conclusion

Early treatment with magnesium sulfate resulted in a significant improvement in DAI outcome. Further studies are needed to confirm the clinical significance of treatment of DAI patients with magnesium sulfate.

Magnesium: potential roles in neurovascular disease

OBJECTIVE

Magnesium therapy has been studied extensively in pre-clinical and clinical trials in multiple organ systems. Cerebrovascular diseases may benefit from its neuroprotective properties. This review summarizes current studies of magnesium in a wide range of neurovascular diseases.

METHODS

We searched relevant terms in the National Library of Medicine PubMed database and selected research including basic science, translational reports, meta-analyses, and clinical studies.

RESULTS

Studies examining magnesium administration in ischemic stroke have failed to show any benefit in clinical outcome. Data on magnesium for intracerebral hemorrhage (ICH) are limited. Preliminary investigations in subarachnoid hemorrhage (SAH) were promising, but definitive studies did not reveal differences in clinical outcome between magnesium and placebo-treated groups. Studies examining magnesium administration in global ischemia following cardiac arrest suggest a trend toward improved clinical outcome. The strongest evidence for clinically relevant neuroprotection following magnesium administration derives from studies of pre-term infants and patients undergoing cardiac bypass and carotid endarterectomy procedures. Magnesium was found to have an excellent safety profile across all investigations.

CONCLUSION

Magnesium is easy to administer and possesses a favorable safety profile. Its utility as a neuroprotectant in cardiac surgery, carotid endarterectomy, and pre-term infant hypoxia remain promising. Value as a therapeutic agent in ischemic stroke, ICH, and SAH is unclear and appears to be limited by late administration. Ongoing clinical trials assessing magnesium administration in the first hours following symptom onset may help clarify the role of magnesium therapy in these disease processes.

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.

Magnesium treatment for neuroprotection in ischemic diseases of the brain

This article reviews experimental and clinical data on the use of magnesium as a neuroprotective agent in various conditions of cerebral ischemia. Whereas magnesium has shown neuroprotective properties in animal models of global and focal cerebral ischemia, this effect could not be reproduced in a large human stroke trial. These conflicting results may be explained by the timing of treatment. While treatment can be started before or early after ischemia in experimental studies, there is an inevitable delay of treatment in human stroke. Magnesium administration to women at risk for preterm birth has been investigated in several randomized controlled trials and was found to reduce the risk of neurological deficits for the premature infant. Postnatal administration of magnesium to babies after perinatal asphyxia has been studied in a number of controlled clinical trials. The results are promising but the trials have, so far, been underpowered. In aneurysmal subarachnoid hemorrhage (SAH), cerebral ischemia arises with the onset of delayed cerebral vasospasm several days after aneurysm rupture. Similar to perinatal asphyxia in impending preterm delivery, treatment can be started prior to ischemia. The results of clinical trials are conflicting. Several clinical trials did not show an additive effect of magnesium with nimodipine, another calcium antagonist which is routinely administered to SAH patients in many centers. Other trials found a protective effect after magnesium therapy. Thus, it may still be a promising substance in the treatment of secondary cerebral ischemia after aneurysmal SAH. Future prospects of magnesium therapy are discussed.

Role of magnesium sulfate in neuroprotection in acute ischemic stroke

AIMS

To study the effect of intravenous magnesium sulfate infusion on clinical outcome of patients of acute stroke.

MATERIALS AND METHODS

Sixty consecutive cases of acute ischemic stroke hospitalised within 24 h of an episode of stroke were taken as subjects. All subjects underwent a computed tomography head, and those found to have evidence of bleed/space-occupying lesions were excluded from the study. The subjects taken up for the study were divided into two groups of 30 subjects each. Both the groups received the standard protocol management for acute ischemic stroke. Subjects of Group 1 additionally received intravenous magnesium sulfate as initial 4 g bolus dose over 15 min followed by 16 g as slow infusion over the next 24 h. In all the subjects of the two study groups, serum magnesium levels were estimated at the time of admission (Day 0), Day 1 and Day 2 of hospitalization using an atomic absorption spectrometer.

STATISTICAL ANALYSIS USED

Scandinavian stroke scores were calculated on Day 3, day of discharge and Day 28. Paired t-test was employed for comparison of stroke scores on Day 3, day of discharge and Day 28 within the same group and the unpaired t-test was used for the intergroup comparison, i.e. comparison of stroke scores of control group with corresponding stroke scores of magnesium group.

RESULTS

Comparison of stroke scores on Day 3 and day of discharge, on the day of discharge and Day 28 and on Day 3 and Day 28 in the magnesium group produced a t-value of 5.000 and P <0.001, which was highly significant. However, the comparison of the mean stroke scores between the magnesium and the control groups on Day 3, day of discharge and Day 28 yielded a P-value of >0.05, which was not significant.

CONCLUSIONS

The study failed to document a statistical significant stroke recovery in spite of achieving a significant rise in serum magnesium level, more than that necessary for neuroprotection, with an intravenous magnesium sulfate regime.

Evaluation of the intravenous magnesium sulfate effect in clinical improvement of patients with acute ischemic stroke

BACKGROUND

Evidence is mounting that magnesium may play a critical role in the development of strokes and the healing process during and after a stroke. Magnesium is an N-methyl-D-aspartate (NMDA) glutamate receptor antagonist that has been shown to be neuroprotective in many preclinical models of ischemic and excitotoxic brain injury. This study was performed to evaluate the intravenous magnesium sulfate effect in clinical improvement of patients with acute ischemic stroke.

METHODS

One hundred and seven patients with acute ischemic stroke signs and symptoms lasting less than 12 hours were included in the study and were divided into two groups, 55 patients received 4 g of MgSO(4) over 15 minutes and then 16 g over the next 24 hours, and 52 patients were received matching placebo. The study primary end point was stroke related neurologic deficit evaluation by the national institute of stroke scale (NIHSS).

RESULTS

Patients receiving MgSO(4) showed significant recovery compared with the group of patients receiving placebo.

CONCLUSION

This study suggests that magnesium sulfate can be used as a safe and useful neuroprotective agent in acute ischemic stroke and lacunar stroke patients may represent a relevant and practical target population for agents with biological activity in white matter.

Investigational therapies for ischemic stroke: neuroprotection and neurorecovery

Stroke is one of the leading causes of death and disability worldwide. Current treatment strategies for ischemic stroke primarily focus on reducing the size of ischemic damage and rescuing dying cells early after occurrence. To date, intravenous recombinant tissue plasminogen activator is the only United States Food and Drug Administration approved therapy for acute ischemic stroke, but its use is limited by a narrow therapeutic window. The pathophysiology of stroke is complex and it involves excitotoxicity mechanisms, inflammatory pathways, oxidative damage, ionic imbalances, apoptosis, angiogenesis, neuroprotection, and neurorestoration. Regeneration of the brain after damage is still active days and even weeks after a stroke occurs, which might provide a second window for treatment. A huge number of neuroprotective agents have been designed to interrupt the ischemic cascade, but therapeutic trials of these agents have yet to show consistent benefit, despite successful preceding animal studies. Several agents of great promise are currently in the middle to late stages of the clinical trial setting and may emerge in routine practice in the near future. In this review, we highlight select pharmacologic and cell-based therapies that are currently in the clinical trial stage for stroke.

Preclinical drug evaluation for combination therapy in acute stroke using systematic review, meta-analysis, and subsequent experimental testing

There is some evidence that in animal models of acute ischaemic stroke, combinations of neuroprotective agents might be more efficacious than the same agents administered alone. Hence, we developed pragmatic, empirical criteria based on therapeutic target, cost, availability, efficacy, administration, and safety to select drugs for testing in combination in animal models of acute stroke. Magnesium sulphate, melatonin, and minocycline were chosen from a library of neuroprotective agents, and were tested in a more 'realistic' model favoured by the STAIR (Stroke Therapy Academic Industry Roundtable). Outcome was assessed with infarct volume, neurologic score, and two newly developed scales measuring general health and physiologic homeostasis. Owing to the failure to achieve neuroprotection in aged, hypertensive animals with drug delivery at 3 hours, the bar was lowered in successive experiments to determine whether neuroprotection could be achieved under conditions more conducive to recovery. Testing in younger animals showed more favourable homeostasis and general health scores than did testing in older animals, but infarct volume and neurologic scores did not differ with age, and treatment efficacy was again not shown. Testing with shorter occlusions resulted in smaller infarct volumes; nevertheless, treatment efficacy was still not observed. It was concluded that this combination, in these stroke models, was not effective.

Vasoactive drugs for acute stroke

BACKGROUND

It is unclear whether blood pressure (BP) should be altered actively during the acute phase of stroke.

OBJECTIVES

To assess the effect of lowering or elevating BP in people with acute stroke, and the effect of different vasoactive drugs on BP in acute stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched June 2009), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 4, 2009), MEDLINE (1966 to October 2009), EMBASE (1980 to October 2009), and Science Citation Index (1981 to October 2009).

SELECTION CRITERIA

Randomised trials of interventions that would be expected, on pharmacological grounds, to alter BP in patients within one week of the onset of acute stroke.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied the trial inclusion criteria, assessed trial quality, and extracted data.

MAIN RESULTS

We identified 131 trials involving in excess of 18,000 patients; a further 13 trials are ongoing. We obtained data for 43 trials (7649 patients). Among BP-lowering trials, beta receptor antagonists lowered BP (early systolic BP (SBP) mean difference (MD) -6.1 mmHg, 95% CI -11.4 to -0.9; late SBP MD -4.9 mmHg, 95% CI -10.2 to 0.4; late diastolic BP (DBP) MD -4.5 mmHg, 95% CI -7.8 to -1.2). Oral calcium channel blockers (CCB) lowered BP (late SBP MD -3.2 mmHg, 95% CI -5.4 to -1.1; early DBP MD -2.5, 95% CI -5.6 to 0.7; late DBP MD -2.1, 95% CI -3.5 to -0.7). Nitric oxide donors lowered BP (early SBP MD -10.3 mmHg, 95% CI -17.6 to -3.0). Prostacyclin lowered BP (late SBP MD, -7.7 mmHg, 95% CI -15.6 to 0.2; late DBP MD -3.9 mmHg, 95% CI -8.1 to 0.4). Among BP-increasing trials, diaspirin cross-linked haemoglobin (DCLHb) increased BP (early SBP MD 15.3 mmHg, 95% CI 4.0 to 26.6; late SBP MD 15.9 mmHg, 95% CI 1.8 to 30.0). None of the drug classes significantly altered outcome apart from DCLHb which increased combined death or dependency (odds ratio (OR) 5.41, 95% CI 1.87 to 15.64).

AUTHORS' CONCLUSIONS

There is not enough evidence to evaluate reliably the effect of altering BP on outcome after acute stroke. However, treatment with DCLHb was associated with poor clinical outcomes. Beta receptor antagonists, CCBs, nitric oxide, and prostacyclin each lowered BP during the acute phase of stroke. In contrast, DCLHb increased BP.

Therapeutic approaches to cerebral vasospasm complicating ruptured aneurysm

Cerebral vasospasm is a serious complication of ruptured aneurysm. In order to avoid short- and long-term effects of cerebral vasospasm, and as there is no single or optimal treatment modality employed, we have instituted a protocol for the prevention and treatment of vasospasm in patients suffering aneurysmal sub-arachnoid hemorrhage (SAH). We then reviewed the effectiveness of this protocol in reducing the mortality and morbidity rate in our institution. In this study we present a retrospective analysis of 52 cases. Between March 2004 and December 2008 52 patients were admitted to our service with aneurysmal SAH. All patients commenced nimodipine, magnesium sulphate (MgSO₄) and triple H therapy. Patients with significant reduction in conscious level were intubated, ventilated and sedated. Intracranial pressure (ICP) monitoring was used for intubated patients. Sodium thiopental coma was induced for patients with refractory high ICP; angiography was performed for diagnosis and treatment. Balloon angioplasty was performed if considered necessary. Using this protocol, only 13 patients (25%) developed clinical vasospasm. Ten of them were given barbiturates to induce coma. Three patients underwent transluminal balloon angioplasty. Four out of 52 patients (7.7%) died from severe vasospasm, 3 patients (5.8%) became severely disabled, and 39 patients (75%) were discharged in a condition considered as either normal or near to their pre-hemorrhage status. Our results confirm that the aforementioned protocol for treatment of cerebral vasospasm is effective and can be used safely.

Results of the MRI substudy of the intravenous magnesium efficacy in stroke trial

BACKGROUND AND PURPOSE

Although magnesium is neuroprotective in animal stroke models, no clinical benefit was confirmed in the Intravenous Magnesium Efficacy in Stroke (IMAGES) trial of acute stroke patients. The Magnetic Resonance in IMAGES (MR IMAGES) substudy investigated the effects of magnesium on the imaging surrogate outcome of infarct growth.

METHODS

IMAGES trial patients in participating centers were randomized to receive either intravenous magnesium or placebo within 12 hours of stroke onset. Infarct growth was defined as volume difference between baseline diffusion-weighted imaging and day 90 fluid-attenuated inversion recovery image lesions. Patients who died were imputed the largest infarct growth observed.

RESULTS

Among the 90 patients included in the primary analysis, there was no difference in infarct growth (median absolute growth, P=0.639; median percentage growth, P=0.616; proportion with any growth, P=0.212) between the 46 treated with magnesium and 44 with placebo. Infarct growth correlated with NIHSS score change from baseline to day 90. There was a trend showing baseline serum glucose correlated with infarct growth with magnesium treatment, but not in the placebo group. The mismatch frequency was reduced from 73% to 47% by increasing the mismatch threshold from >20% to >100% of core volume.

CONCLUSIONS

Infarct growth, confirmed here as a surrogate for clinical progression, was similar between magnesium and placebo treatment, paralleling the main IMAGES trial clinical outcomes. Glucose was a covariate for infarct growth with magnesium treatment. A more stringent mismatch threshold to define penumbra more appropriately would have excluded half of the patients in this 12-hour time window stroke study.

Magnesium sulphate reduces cell volume in physiological conditions but not in the cytotoxic oedema during global brain ischemia

PRIMARY OBJECTIVE

To establish the effect of MgSO4 on brain cellular volume during physiological and global ischemia using impedanciometric method.

RESEARCH DESIGN

Impedanciometric measure in the brain before and during global brain ischemia, with or without intravenous infusion of MgSO4.

METHODS AND PROCEDURES

Male Sprague-Dawley rats were anaesthetized (thiobarbital, 60 mg kg-1 i.p.). Ringer solution (n=9) or MgSO4 (n=8; 1 mmol Kg-1) where i.v. isovolumetrically administered. Sub-cortical impedance was recorded before and after the infusion of ringer or MgSO4 and during global cerebral ischemia induced by a cardiopulmonary arrest.

MAIN OUTCOMES AND RESULTS

In non-ischemic conditions, MgSO4 infusion induced higher voltage values than those of ringer infusion (Wilcoxon, Z=2.49; p=0.01). During global cerebral ischemia, the MgSO4 infused animals showed a fast drop of voltages (82%) in the first 5 minutes, 4-fold the values of ringer infused animals (p<0.0001). In the following 15 minutes no differences were found between ringer and MgSO4 infused animals.

CONCLUSIONS

The results suggest that MgSO4 significantly reduced brain cell volume in physiological conditions but not in global brain ischemia.

Achieved serum magnesium concentrations and occurrence of delayed cerebral ischaemia and poor outcome in aneurysmal subarachnoid haemorrhage

BACKGROUND

Magnesium therapy probably reduces the frequency of delayed cerebral ischaemia (DCI) in subarachnoid haemorrhage (SAH) but uncertainty remains about the optimal serum magnesium concentration. We assessed the relationship between serum magnesium concentrations achieved with magnesium sulphate therapy 64 mmol/day and the occurrence of DCI and poor outcome in patients with SAH.

METHODS

Differences in magnesium concentrations between patients with and without DCI and with and without poor outcome were calculated. Quartiles of last serum magnesium concentrations before the onset of DCI, or before the median day of DCI in patients without DCI, were related to the occurrence of DCI and poor outcome at 3 months using logistic regression.

RESULTS

Compared with the lowest quartile of serum magnesium concentration (1.10-1.28 mmol/l), the risk of DCI was decreased in each of the higher three quartiles (adjusted odds ratio (OR) in each quartile 0.2; lower 95% CI 0.0 to 0.1; upper limit 0.8 to 0.9). The OR for poor outcome was 1.8 (95% CI 0.5 to 6.9) in the second quartile, 1.0 (95% CI 0.2 to 4.5) in the third quartile and 4.9 (95% CI 1.2 to 19.7) in the highest quartile.

DISCUSSION

Magnesium sulphate 64 mmol/day results in a stable risk reduction of DCI over a broad range of achieved serum magnesium concentrations, and strict titration of the dosage therefore does not seem necessary. However, concentrations < or = 1.28 mmol/l could decrease the effect on DCI while concentrations > or = 1.62 might have a negative effect on clinical outcome.

Progress in shivering control

Hypothermia is a potent neuroprotectant and induced hypothermia holds great promise as a therapy for acute neuronal injury. Thermoregulatory responses, most notably shivering, present major obstacles to therapeutic temperature management. A review of thermoregulatory physiology and strategies aimed at controlling physiologic responses to hypothermia is presented.

Efecto de la hipotermia combinada con magnesio y tirilazad en un modelo experimental de isquemia cerebral difusa

OBJECTIVE

To determine the grade of neuroprotection of combined treatment with moderate hypothermia, tirilazad and magnesium sulfate. Cerebral ischemia is one of the problems of great interest at present, with limited therapeutic measures. Hypothermia, one of the more efficient measures, together with neuroprotector pharmaceuticals, could be a valid alternative.

DESIGN

Experimental study with a control group and two levels of application of therapeutic measures.

CONTEXT

Experimental laboratory of the Medicine Faculty.

PARTICIPANTS AND METHOD

Twenty-eight Wistar rats underwent global cerebral ischemia of 10 minutes duration by the combination of bilateral carotid clamping and controlled hypotension (mean arterial pressure: 45 mmHg). Three groups were used: group I, normothermia maintenance; group II, moderate hypothermia (32-33 degrees C) for 2 hours; group III, hypothermia and administration of tirilazad mesylate and magnesium sulfate during the reperfusion and two hours after ischemia. The animals were sacrificed at 7 days and, after processing the tissue, the neurons preserved in layer CA1 of the hippocampus were counted.

RESULTS

There is a significantly greater neuronal preservation in group III with regard to group I (55.4 +/- 5.1 versus 38.7 +/- 8.8, p < 0.0001). If we compare groups II and III, significant differences are only obtained on the right side and in the hippocampus considered globally, favoring the group with hypothermia and drugs. When groups I and II are compared there are no significant differences.

CONCLUSIONS

Association of moderate hypothermia, magnesium sulfate and tirilazad mesylate in the experimental model of transitory global ischemia used is confirmed as an effective neuroprotector measure, surpassing the degree of neuronal preservation of hypothermia alone.

Magnesium infusion for vasospasm prophylaxis after subarachnoid hemorrhage

Object

Despite the application of current standard therapies, vasospasm continues to result in death or major disability in patients treated for ruptured aneurysms. The authors investigated the effectiveness of continous MgSO4 infusion for vasospasm prophylaxis.

Methods

Seventy-six adults (mean age 54.6 years; 71% women; 92% Caucasian) were included in this comparative matched-cohort study of patients with aneurysmal subarachnoid hemorrhage on the basis of computed tomography (CT) findings. Thirty-eight patients who received continuous MgSO4 infusion were matched for age, race, sex, treatment option, Fisher grade, and Hunt and Hess grade to 38 historical control individuals who did not receive MgSO4 infusion. Twelve grams of MgSO4 in 500 ml normal saline was given intravenously daily for 12 days if the patient presented within 48 hours of aneurysm rupture. Vasospasm was diagnosed on the basis of digital substraction angiography, CT angiography, and transcranial Doppler ultrasonography, and evidence of neurological deterioration.

Symptomatic vasospasm was present at a significantly lower frequency in patients who received MgSO4 infusion (18%) compared with patients who did not receive MgSO4 (42%) (p = 0.025). There was no significant difference in mortality rate at discharge (p = 0.328). A trend toward improved outcome as measured by the modifed Rankin Scale (p = 0.084), but not the Glasgow Outcome Scale (p = 1.0), was seen in the MgSO4-treated group.

Conclusions

Analysis of the results suggests that MgSO4 infusion may have a role in cerebral vasospasm prophylaxis if therapy is initiated within 48 hours of aneurysm rupture.

Intravenous magnesium versus nimodipine in the treatment of patients with aneurysmal subarachnoid hemorrhage: a randomized study

OBJECTIVE

The prophylactic use of nimodipine in patients with aneurysmal subarachnoid hemorrhage reduces the risk of ischemic brain damage. However, its efficacy seems to be rather moderate. The question arises whether other types of calcium antagonists offer better protection. Magnesium, nature's physiological calcium antagonist, is neuroprotective in animal models, promotes dilatation of cerebral arteries, and has an established safety profile. The aim of the current pilot study is to evaluate the efficacy of magnesium versus nimodipine to prevent delayed ischemic deficits after aneurysmal subarachnoid hemorrhage.

METHODS

One hundred and thirteen patients with aneurysmal subarachnoid hemorrhage were enrolled in the study and were randomized to receive either magnesium sulfate (loading 10 mg/kg followed by 30 mg/kg daily) or nimodipine (48 mg/d) intravenously until at least postoperative Day 7. Primary outcome parameters were incidence of clinical vasospasm and infarction. Secondary outcome measures were the incidence of transcranial Doppler/angiographic vasospasm, the neuronal markers (neuron-specific enolase, S-100), and the patients' Glasgow Outcome Scale scores at discharge and after 1 year.

RESULTS

One hundred and four patients met the study requirements. In the magnesium group (n = 53), eight patients (15%) experienced clinical vasospasm and 20 (38%) experienced transcranial Doppler/angiographic vasospasm compared with 14 (27%) and 17 (33%) patients in the nimodipine group (n = 51). If clinical vasospasm occurred, 75% of the magnesium-treated versus 50% of the nimodipine-treated patients experienced cerebral infarction resulting in fatal outcome in 37 and 14%, respectively. Overall, the rate of infarction attributable to vasospasm was virtually the same (19 versus 22%). There was no difference in outcome between groups.

CONCLUSION

The efficacy of magnesium in preventing delayed ischemic neurological deficits in patients with aneurysmal subarachnoid hemorrhage seems to be comparable with that of nimodipine. The difference in their pharmacological properties makes studies on the combined administration of magnesium and nimodipine seem promising.

Magnesium as a neuroprotectant in cardiac surgery: A randomized clinical trial

OBJECTIVE

We sought to evaluate magnesium as a neuroprotectant in patients undergoing cardiac surgery with cardiopulmonary bypass.

METHODS

From February 2002 to September 2003, 350 patients undergoing elective coronary artery bypass grafting, valve surgery, or both were enrolled in a randomized, blinded, placebo-controlled trial to receive either magnesium sulfate to increase plasma levels 1(1/2) to 2 times normal during cardiopulmonary bypass (n = 174) or no intervention (n = 176). Neurologic function, neuropsychologic function, and depression were assessed preoperatively, at 24 and 96 hours after extubation (neurologic) and at 3 months (neuropsychologic, depression). Neurologic scores were analyzed using ordinal longitudinal methods, and neuropsychologic and depression inventory data were summarized by principal component analysis, followed by linear regression analysis using component scores as response variables.

RESULTS

Seven (2%) patients had a postoperative stroke, 2 (1%) in the magnesium and 5 (3%) in the placebo group (P = .4). Neurologic score was worse postoperatively in both groups (P < .0001); however, magnesium group patients performed better than placebo group patients (P = .0001), who had prolonged declines in short-term memory and reemergence of primitive reflexes. Three-month neuropsychologic performance and depression inventory score were generally better than preoperatively, with few differences between groups (P > .6); however, older age (P = .0006), previous stroke (P = .003), and lower education level (P = .0007) were associated with worse performance.

CONCLUSIONS

Magnesium administration is safe and improves short-term postoperative neurologic function after cardiac surgery, particularly in preserving short-term memory and cortical control over brainstem functions. However, by 3 months, other factors and not administration of magnesium influence neuropsychologic and depression inventory performance.

Magnesium sulfate: role as possible attenuating factor in vasospasm morbidity

BACKGROUND

Among the many complications of SAH, one of the most important is vasospasm. Several treatment alternatives have been proposed for this condition, with far-from-ideal results being obtained. Magnesium sulfate recently returned to the scene (with still unproven benefit) as an adjuvant in the treatment of vasospasm.

METHODS

Seventy-two patients diagnosed with SAH by aneurysm rupture were submitted to microsurgery craniotomy and subdivided in 2 groups. Group 1, formed by 48 patients, received prophylactic hypervolemic and hemodilution therapy in addition to nimodipine. Group 2, composed of 24 patients, received the same treatment of group 1 with the addition of magnesium sulfate in continuous infusion from 120 to 150 mg a day, keeping serum magnesium levels close to double normal values.

RESULTS

Age was 49 +/- 12.6 years. Ratio of female to male was 3.16:1. Most patients were admitted in a Hunt-Hess grade 2 (46.4%) and Fisher grade 3 (52.8%). Anterior communicating artery aneurysms were the most common in location (38.8%). Both groups were compared, and there was no statistical difference related to age, sex, and Glasgow, Fisher, or Hunt-Hess admission grades. No statistical difference in vasospasm incidence was found between the two groups. However, in group 1, vasospasm was correlated with a longer hospitalization time (P = .0003), different from group 2, in which patients with vasospasm receiving magnesium sulfate required less hospitalization time.

CONCLUSION

Magnesium did not seem to interfere in vasospasm frequency but apparently acted favorably in decreasing morbidity and length of hospital stay.

Ion channels involved in stroke

Ion channels are membrane proteins that flicker open and shut to regulate the flow of ions down their electrochemical gradient across the membrane and consequently regulate cellular excitability. Every living cell expresses ion channels, as they are critical life-sustaining proteins. Ion channels are generally either activated by voltage or by ligand interaction. For each group of ion channels the channels' molecular biology and biophysics will be introduced and the pharmacology of that group of channels will be reviewed. The in vitro and in vivo literature will be reviewed and, for ion channel groups in which clinical trials have been conducted, the efficacy and therapeutic potential of the neuroprotective compounds will be reviewed. A large part of this article will deal with glutamate receptors, focusing specifically on N-methyl-D-aspartate (NMDA) receptors. Although the outcome of clinical trials for NMDA receptor antagonists as therapeutics for acute stroke is disappointing, the culmination of these failed trials was preceded by a decade of efforts to develop these agents. Sodium and calcium channel antagonists will be reviewed and the newly emerging efforts to develop therapeutics targeting potassium channels will be discussed. The future development of stroke therapeutics targeting ion channels will be discussed in the context of the failures of the last decade in hopes that this decade will yield successful stroke therapeutics.

Treatments for stroke

Stroke is the third leading cause of death and the leading cause of disability in developed countries, yet remains a poorly treated condition. Treatments for stroke can be aimed at acutely improving blood flow or protecting brain tissue against ischaemia, enhancing stroke recovery or reducing the risk of stroke recurrence. This paper reviews each of these approaches, particularly focusing on mechanisms for which there are agents in clinical trials. There are a number of appealing neuroprotective agents in Phase II and III clinical trials. However, the majority of acute treatments are likely to suffer from a narrow therapeutic time window and hence limited patient access. Combinations of acute approaches are likely to offer the greatest benefit, but present challenges in development. Promotion of recovery following stroke offers enormous potential for successful therapeutic intervention. Excitingly, new developments in preclinical research have identified possible ways in which this may be achieved.

Strategies of neuroprotection for intracranial aneurysms

Neuroprotection for patients with intracranial aneurysms encompasses the preservation of brain cells endangered by a limited blood and oxygen supply due to aneurysm rupture, clipping or coiling, as well as vasospasm. A large variety of prophylactic and therapeutic neuroprotective strategies have been proposed, but success in human disease is quite limited. Topics of this chapter are the pathophysiology and treatment options of aneurysms, as well as promising neuroprotective strategies in further developmental stages: both physiologically based (hyperoxygenation, hypothermia, avoidance of hyperthermia and hyperglycaemia, hypertension, haemodilution and hypervolaemia) and pharmacologically based (antifibrinolytic drugs, calcium antagonists, anaesthetics, magnesium, erythropoietin and others). New concepts are ischaemic preconditioning, growth factors, and gene therapy. Each strategy is rated on underlying evidence, and research agendas are mentioned.

Magnesium for acute stroke (Intravenous Magnesium Efficacy in Stroke trial): randomised controlled trial

BACKGROUND

Magnesium is neuroprotective in animal models of stroke, and findings of small clinical pilot trials suggest potential benefit in people. We aimed to test whether intravenous magnesium sulphate, given within 12 h of stroke onset, reduces death or disability at 90 days.

METHODS

2589 patients were randomised within 12h of acute stroke to receive 16 mmol MgSO4 intravenously over 15 min and then 65 mmol over 24 h, or matching placebo. Primary outcome was a global endpoint statistic expressed as the common odds ratio for death or disability at day 90. Secondary outcomes were mortality and death or disability, variously defined as Barthel score less than 95, Barthel score less than 60, and modified Rankin scale more than 1. Predefined subgroup analyses were for the primary endpoint in patients in whom treatment commenced within 6 h versus after 6 h, ischaemic versus non-ischaemic strokes, and cortical stroke syndromes versus non-cortical strokes. Intention-to-treat and efficacy analyses were done.

FINDINGS

The efficacy dataset included 2386 patients. Primary outcome was not improved by magnesium (odds ratio 0.95, 95% CI 0.80-1.13, p=0.59). Mortality was slightly higher in the magnesium-treated group than in the placebo group (hazard ratio 1.18, 95% CI 0.97-1.42, p=0.098). Secondary outcomes did not show any treatment effect. Planned subgroup analyses showed benefit of magnesium in non-cortical strokes (p=0.011) whereas greater benefit had been expected in the cortical group.

INTERPRETATION

Magnesium given within 12 h of acute stroke does not reduce the chances of death or disability significantly, although it may be of benefit in lacunar strokes.

Magnesium and experimental vasospasm

Object. Interest has developed in the use of magnesium (Mg++) as a neuroprotectant and antivasospastic agent. Magnesium may increase cerebral blood flow (CBF) and reduce the contraction of cerebral arteries caused by various stimuli. In this study the authors tested the hypothesis that a continuous intravenous infusion of Mg++ reduces cerebral vasospasm after experimental subarachnoid hemorrhage (SAH).

Methods. A dose-finding study was conducted in five monkeys (Macaca fascicularis) to determine what doses of intravenous MgSO4 elevate the cerebrospinal fluid (CSF) concentrations of Mg++ to vasoactive levels and to determine what effects these doses have on the diameters of cerebral arteries, as shown angiographically. After a standard dose of MgSO4 had been selected it was then administered in a randomized, controlled, blinded study to 10 monkeys (five animals/group) with SAH, beginning on Day 0 and continuing for 7 days, at which time angiography was repeated. A 0.086-g/kg bolus of MgSO4 followed by an infusion of 0.028 g/kg/day MgSO4 significantly elevated serum and CSF levels of Mg++ (five monkeys). Magnesium sulfate significantly elevated the serum level of total Mg++ from a control value of 0.83 ± 0.04 mmol/L to 2.42 ± 1.01 mmol/L on Day 7 and raised the CSF level from 1.3 ± 0.04 mmol/L to 1.76 ± 0.14 mmol/L. There was no angiographic evidence of any effect of MgSO4 on normal cerebral arteries. After SAH, the vasospasm in the middle cerebral artery was not significantly reduced (46 ± 8% in the MgSO4-treated group compared with 35 ± 6% in the placebo [vehicle]-treated group, p > 0.05, unpaired t-test).

Conclusions. Magnesium sulfate did not significantly reduce cerebral vasospasm after SAH in the doses tested. An investigation of SAH is warranted mainly to test whether a benefit can be achieved by neuroprotection or by augmentation of CBF by dilation of small vessels and/or collateral pathways.

Clinical trials for cytoprotection in stroke

To date, many cytoprotective drugs have reached the stage of pivotal phase 3 efficacy trials in acute stroke patients. (Table 1) Unfortunately, throughout the neuroprotective literature, the phrase "failure to demonstrate efficacy" prevails as a common thread among the many neutral or negative trials, despite the largely encouraging results encountered in preclinical studies. The reasons for this discrepancy are multiple, and have been discussed by Dr. Zivin in his review. Many of the recent trials have addressed deficiencies of the previous ones with more rigorous trial design, including more specific patient selection criteria (ensure homogeneity of stroke location and severity), stratified randomization algorithms (time-to-treat), narrowed therapeutic time-window and pharmacokinetic monitoring. Current trials have also incorporated biologic surrogate markers of toxicity and outcome such as drug levels and neuroimaging. Lastly, multi-modal therapies and coupled cytoprotection/reperfusion strategies are being investigated to optimize tissue salvage. This review will focus on individual therapeutic strategies and we will emphasize what we have learned from these trials both in terms of trial design and the biologic effect (or lack thereof) of these agents.

Effects of magnesium sulphate on cerebral haemodynamics in healthy volunteers: a transcranial Doppler study

BACKGROUND

Magnesium is increasingly being considered as a neuroprotective agent. We aimed to study its effects on middle cerebral artery blood flow velocity (V(mca)), cerebral autoregulation and cerebral vascular reactivity to carbon dioxide (CRCO(2)) in healthy volunteers.

METHODS

Fifteen healthy volunteers were recruited. Using transcranial Doppler ultrasonography, V(mca) was recorded continuously. The strength of autoregulation was assessed by the transient hyperaemic response test, and the CRCO(2) was measured by assessing changes in V(mca) to the induced changes in end-tidal carbon dioxide. I.V. infusion of magnesium sulphate was then started (loading dose of 16 mmol followed by an infusion at the rate of 2.7 mmol h(-1)) for 45 min. The cerebral haemodynamic variables were measured again near the end of the infusion of magnesium sulphate.

RESULTS

Total serum magnesium levels were doubled by the infusion regimen. However, there were no significant changes in V(mca), strength of autoregulation, or CRCO(2). Five of the volunteers reported marked nausea and two developed significant hypotension during the loading dose.

CONCLUSIONS

Infusion of magnesium sulphate, in a dose that doubles its concentration in plasma, does not affect V(mca), strength of autoregulation or CRCO(2) in healthy volunteers. However, it can be associated with nausea and hypotension.

Excitatory amino acid antagonists for acute stroke

BACKGROUND

Focal cerebral ischaemia causes release of excitatory amino acid (EAA) neurotransmitters, principally glutamate, with resultant over-stimulation of EAA receptors and downstream pathways. Excess glutamate release is a pivotal event in the evolution of irreversible ischaemic damage in animal models of ischaemia, and drugs that modulate glutamate action either by inhibiting its release, or blocking post-synaptic receptors, are potent neuroprotective agents. Many clinical trials with EAA modulating drugs have been conducted, none individually demonstrating efficacy.

OBJECTIVES

To synthesise all the available data on all different classes of EAA modulators and to evaluate evidence of effects on outcome systematically.

SEARCH STRATEGY

Relevant trials were identified in the Specialised Register of Controlled Trials (last searched May 2001). In addition, MEDLINE and EMBASE online searches for the terms "neuroprotection" (and its variants), "neuroprotective agent", for all individual drugs and drug classes included in the review, hand searches of conference proceedings from European, International, American Heart Association and Princeton conferences on Stroke, American Neurological Association and American Academy of Neurology meetings from 1992-2001, and direct contact with individual investigators and pharmaceutical companies.

SELECTION CRITERIA

Trials were included if they were randomised, controlled studies giving agents with pharmacological properties that included modification of release of EAAs, or blockade of EAA receptors, in stroke within 24h of onset. Efficacy analysis was restricted to trials with a parallel group design: dose escalation studies were excluded. Intention-to-treat analyses were performed on all data. Outcome had to be reported in terms of death or dependence 1-12 months after the acute event.

DATA COLLECTION AND ANALYSIS

Data were available for 36 of 41 relevant trials identified, involving 11,209 subjects. Data were unavailable for 632 participants (517 in trials fulfilling criteria for efficacy analysis). Seven trials did not report disability data, which were available for 29 trials involving 10,802 subjects. Twenty one of these trials, involving 10,342 subjects, were parallel group studies included in the primary efficacy analysis. Efficacy analysis included data derived from 9 trials not primarily designed to assess efficacy (1022 subjects). The primary (efficacy) end-point was the proportion of patients dead or disabled at final follow-up (defined by Barthel Index<60 at 3 months by preference). Mortality was a secondary end-point. Drugs were considered as individual agents, and also grouped principally into categories of ion channel modulators (glutamate release inhibition) and NMDA antagonists.

MAIN RESULTS

There was no significant heterogeneity of outcome amongst individual drugs, or of drug classes either for the primary efficacy analysis (death or dependence) or for mortality at final follow-up. For the primary efficacy analysis, odds of death or dependence were 1.03 [95% confidence interval 0.96-1.12], and for mortality 1.02 [0.92-1.12]. Neither ion channel modulators (death or dependence 1.02 [0.90-1.16]) nor NMDA antagonists (death or dependence 1.05 [0.95-1.16]) differed from the principal analysis including all compounds. Trends for increased mortality with three NMDA antagonists were seen - selfotel (OR 1.19 [0.81-1.74]), aptiganel (OR 1.32 [0.91-1.93]) and gavestinel (OR 1.12 [0.95-1.32]) - but this did not achieve significance for the NMDA antagonists considered as a class (1.09 [0.96-1.23]). Aptiganel was also associated with a trend towards worse functional outcome (OR 1.20 [0.88-1.65]) although this was not the case for either of the other two compounds. No statistically significant detriment of psychotomimetic NMDA antagonists was found, although a trend towards higher mortality in this sub-group was seen (OR 1.25 [0.96-1.64]).

REVIEWER'S CONCLUSIONS

There was no evidence of significant benefit or harm from drugs modulating excitatory amino acid action. Reductio]).

REVIEWER'S CONCLUSIONS

There was no evidence of significant benefit or harm from drugs modulating excitatory amino acid action. Reduction of death or dependence by 8% or more has been excluded for gavestinel and lubeluzole, which contribute most of the data for this review. However, mechanistic understanding of neuroprotection is too poor to extrapolate from these two failed development plans to all glutamate modulators. Further clinical trials of neuroprotective agents remain justified, since confidence limits around estimates of effect remain wide for most agents, and cannot reliably exclude benefit. Although numbers of patients are too small to confirm or refute a trend towards increased mortality with some NMDA antagonists, further commercial development of these agents is exceedingly unlikely.

Magnesium in stroke treatment

Magnesium is involved in multiple physiological processes that may be relevant to cerebral ischaemia, including antagonism of glutamate release, NMDA receptor blockade, calcium channel antagonism, and maintenance of cerebral blood flow. Systemically administered magnesium at doses that double physiological serum concentration significantly reduces infarct volume in animal models of stroke, with a window of up to six hours after onset and favourable dose-response characteristics when compared with previously tested neuroprotective agents. Small clinical trials have reported benefit, but results are not statistically significant in systematic review. A large ongoing trial (IMAGES) will report in 2003-4 and further trials are planned.