Treatment of acute cortical infarct with intravenous glycerol. A double-blind, placebo-controlled randomized trial

Identification of drug side effects with a path-based method

The study of drug side effects is a significant task in drug discovery. Candidate drugs with unaccepted side effects must be eliminated to prevent risks for both patients and pharmaceutical companies. Thus, all side effects for any candidate drug should be determined. However, this task, which is carried out through traditional experiments, is time-consuming and expensive. Building computational methods has been increasingly used for the identification of drug side effects. In the present study, a new path-based method was proposed to determine drug side effects. A heterogeneous network was built to perform such method, which defined drugs and side effects as nodes. For any drug and side effect, the proposed path-based method determined all paths with limited length that connects them and further evaluated the association between them based on these paths. The strong association indicates that the drug has a side effect with a high probability. By using two types of jackknife test, the method yielded good performance and was superior to some other network-based methods. Furthermore, the effects of one parameter in the method and heterogeneous network was analyzed.

Comparative efficacy and safety of glycerol versus mannitol in patients with cerebral oedema and elevated intracranial pressure: A systematic review and meta-analysis

WHAT IS KNOWN AND OBJECTIVE

Glycerol is thought to be superior to mannitol in the treatment of cerebral oedema and elevated intracranial pressure (ICP), particularly with safety concerns. However, the current evidence remains insufficient. Therefore, we aimed to compare the efficacy and safety of glycerol versus mannitol in this meta-analysis.

METHODS

PubMed, EMBASE, Web of Science, CENTRAL, China National Knowledge Infrastructure, Wanfang Database, Chongqing VIP information, ClinicalTrials.gov, and the reference lists of relevant articles were searched for randomized controlled trials comparing glycerol and mannitol in patients with brain oedema and elevated ICP. Two investigators independently identified the articles, assessed the study quality and extracted data. Data analyses were performed using RevMan software.

RESULTS AND DISCUSSION

Thirty trials involving 3144 patients met our inclusion criteria. Pooled data indicated that glycerol and mannitol had comparable effectiveness in controlling cerebral oedema (RR, 1.00; 95% CI, 0.97 to 1.03; p = .97), but the risks of acute kidney injury and electrolyte disturbances were significantly lower with glycerol (RR, 0.21; 95% CI, 0.16 to 0.27 and RR, 0.23; 95% CI, 0.17 to 0.30, respectively) than mannitol. Moreover, there seemed to be a lower probability of rebound ICP after the withdrawal of glycerol. Neither haemolysis nor elevated blood glucose levels were observed in the glycerol group.

WHAT IS NEW AND CONCLUSION

Regarding the balance between efficacy and safety, glycerol could be an effective and more tolerable alternative therapy for cerebral oedema and elevated ICP than mannitol, especially for high-risk populations of renal failure.

Validated ¹H and 13C Nuclear Magnetic Resonance Methods for the Quantitative Determination of Glycerol in Drug Injections

In the current study, we employed high-resolution proton and carbon nuclear magnetic resonance spectroscopy (¹H and ¹³C NMR) for quantitative analysis of glycerol in drug injections without any complex pre-treatment or derivatization on samples. The established methods were validated with good specificity, linearity, accuracy, precision, stability, and repeatability. Our results revealed that the contents of glycerol were convenient to calculate directly via the integration ratios of peak areas with an internal standard in ¹H NMR spectra, while the integration of peak heights were proper for ¹³C NMR in combination with an external calibration of glycerol. The developed methods were both successfully applied in drug injections. Quantitative NMR methods showed an extensive prospect for glycerol determination in various liquid samples.

Osmotic therapies added to antibiotics for acute bacterial meningitis

BACKGROUND

Every day children and adults die from acute community-acquired bacterial meningitis, particularly in low-income countries, and survivors risk deafness, epilepsy and neurological disabilities. Osmotic therapies may attract extra-vascular fluid and reduce cerebral oedema, and thus reduce death and improve neurological outcomes.This is an update of a Cochrane Review first published in 2013.

OBJECTIVES

To evaluate the effects of osmotic therapies added to antibiotics for acute bacterial meningitis in children and adults on mortality, deafness and neurological disability.

SEARCH METHODS

We searched CENTRAL (2017, Issue 1), MEDLINE (1950 to 17 February 2017), Embase (1974 to 17 February 2017), CINAHL (1981 to 17 February 2017), LILACS (1982 to 17 February 2017) and registers of ongoing clinical trials (ClinicalTrials.com, WHO ICTRP) (21 February 2017). We also searched conference abstracts and contacted researchers in the field (up to 12 December 2015).

SELECTION CRITERIA

Randomised controlled trials testing any osmotic therapy in adults or children with acute bacterial meningitis.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the search results and selected trials for inclusion. Results are presented using risk ratios (RR) and 95% confidence intervals (CI) and grouped according to whether the participants received steroids or not. We used the GRADE approach to assess the certainty of the evidence.

MAIN RESULTS

We included five trials with 1451 participants. Four trials evaluated glycerol against placebo, and one evaluated glycerol against 50% dextrose; in addition three trials evaluated dexamethasone and one trial evaluated acetaminophen (paracetamol) in a factorial design. Stratified analysis shows no effect modification with steroids; we present aggregate effect estimates.Compared to placebo, glycerol probably has little or no effect on death in people with bacterial meningitis (RR 1.08, 95% CI 0.90 to 1.30; 5 studies, 1272 participants; moderate-certainty evidence), but may reduce neurological disability (RR 0.73, 95% CI 0.53 to 1.00; 5 studies, 1270 participants; low-certainty evidence).Glycerol may have little or no effect on seizures during treatment for meningitis (RR 1.08, 95% CI 0.90 to 1.30; 4 studies, 1090 participants; low-certainty evidence).Glycerol may reduce the risk of subsequent deafness (RR 0.64, 95% CI 0.44 to 0.93; 5 studies, 922 participants; low to moderate-certainty evidence).Glycerol probably has little or no effect on gastrointestinal bleeding (RR 0.93, 95% CI 0.39 to 2.19; 3 studies, 607 participants; moderate-certainty evidence). The evidence on nausea, vomiting and diarrhoea is uncertain (RR 1.09, 95% CI 0.81 to 1.47; 2 studies, 851 participants; very low-certainty evidence).

AUTHORS' CONCLUSIONS

Glycerol was the only osmotic therapy evaluated, and data from trials to date have not demonstrated an effect on death. Glycerol may reduce neurological deficiency and deafness.

Meta-analysis of studies comparing adjuvant dexamethasone to glycerol to improve clinical outcome of bacterial meningitis

Background:

Neurological complications are a problematic factor in acute bacterial meningitis; hence, its prevention is the key to ensure the success of meningitis treatment. Glycerol and dexamethasone are both applied in this regard. Oral glycerol is an appropriate alternative instead of intravenous dexamethasone because it does not have problems related to intravenous injection, the high cost, and drug complications. The main objective of this study was to compare the efficacy of adjuvant dexamethasone versus glycerol in order to improve the clinical outcome of bacterial meningitis.

Materials and Methods:

We conducted a search on the available resources including PubMed, Ovid, Elsevier, Cochrane, and another search engines such as Google till 2014. All clinical trials that were performed in the field of comparing the effectiveness of the two drugs and met the inclusion criteria were gathered and after extraction the relative risk (RR) values, the pooled RR was calculated. The main outcome was neurological complications. Meta-analysis of the data was performed in Stata version 11.2 using both fixed and random effect models, weighting each study by inverse of variance.

Results:

In 5 comparative studies (1,340 patients), the rate of neurological complications of glycerol compared to that of dexamethasone was 1.02 [95% confidence interval (CI), 0.98 compared to 1.12]. The rate of neurological complications of dexamethasone compared to dexamethasone + glycerol was 1 (95% CI, 0.97 compared to 1.03), dexamethasone compared to placebo was 0.99 (95% CI, 0.97 compared to 1.03), glycerol compared to glycerol + dexamethasone was 0.98 (95% CI, 0.94 compared to 1.02), and glycerol compared to placebo was 0.97 (95% CI, 0.94 compared to 1.01). In these studies, no difference was reported between dexamethasone and glycerol in terms of reducing neurological complications.

Conclusion:

Although there were some weak evidences for the nonstatistical significant effect of glycerol in the prevention of neurologic complication after meningitis, there was no difference between glycerol and dexamethasone.

Osmotic therapies added to antibiotics for acute bacterial meningitis

BACKGROUND

Every day children and adults throughout the world die from acute community-acquired bacterial meningitis, particularly in low-income countries. Survivors are at risk of deafness, epilepsy and neurological disabilities. Osmotic therapies have been proposed as an adjunct to improve mortality and morbidity from bacterial meningitis. The theory is that they will attract extra-vascular fluid by osmosis and thus reduce cerebral oedema by moving excess water from the brain into the blood. The intention is to thus reduce death and improve neurological outcomes.

OBJECTIVES

To evaluate the effects on mortality, deafness and neurological disability of osmotic therapies added to antibiotics for acute bacterial meningitis in children and adults.

SEARCH METHODS

We searched CENTRAL 2012, Issue 11, MEDLINE (1950 to November week 3, 2012), EMBASE (1974 to November 2012), CINAHL (1981 to November 2012), LILACS (1982 to November 2012) and registers of ongoing clinical trials (April 2012). We also searched conference abstracts and contacted researchers in the field.

SELECTION CRITERIA

Randomised controlled trials testing any osmotic therapy in adults or children with acute bacterial meningitis.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the search results and selected trials for inclusion. We collected data from each study for mortality, deafness, seizures and neurological disabilities. Results are presented using risk ratios (RR) and 95% confidence intervals (CI) and grouped according to whether the participants received steroids or not.

MAIN RESULTS

Four trials were included comprising 1091 participants. All compared glycerol (a water-soluble sugar alcohol) with a control; in three trials this was a placebo, and in one a small amount of 50% dextrose. Three trials included comparators of dexamethasone alone or in combination with glycerol. As dexamethasone appeared to have no modifying effect, we aggregated results across arms where both treatment and control groups received corticosteroids and where both treatment and control groups did not.Compared to placebo, glycerol may have little or no effect on death in people with bacterial meningitis (RR 1.09, 95% confidence interval (CI) 0.89 to 1.33, 1091 participants, four trials, low-quality evidence); or on death and neurological disability combined (RR 1.04, 95% CI 0.86 to 1.25).Glycerol may have little or no effect on seizures during treatment for meningitis (RR 1.08, 95% CI 0.90 to 1.30, 909 participants, three trials, low-quality evidence).Glycerol may reduce the risk of subsequent deafness (RR 0.60, 95% CI 0.38 to 0.93, 741 participants, four trials, low-quality evidence).

AUTHORS' CONCLUSIONS

The only osmotic diuretic to have undergone randomised evaluation is glycerol. Data from trials to date have not demonstrated benefit on death, but it may reduce deafness. Osmotic diuretics, including glycerol, should not be given to adults and children with bacterial meningitis unless as part of carefully conducted randomised controlled trial.

Glycerol adjuvant therapy in adults with bacterial meningitis in a high HIV seroprevalence setting in Malawi: a double-blind, randomised controlled trial

BACKGROUND

Southern Africa has a high incidence of bacterial meningitis in adults, often associated with HIV co-infection. Mortality exceeds 50%, even with appropriate antibiotic therapy, and is not improved with corticosteroids. Glycerol adjuvant therapy reduces long-term morbidity in bacterial meningitis in children, and its use is being promoted. We aimed to assess the effectiveness of glycerol as an adjuvant therapy for adults with bacterial meningitis in Africa.

METHODS

The study was done in two phases. First, in an open-label dose-finding study, 45 adult patients with symptoms, signs, and cerebrospinal fluid findings consistent with bacterial meningitis received either 50 mL, 75 mL, or 100 mL of glycerol four times a day for 4 days. We then did a randomised, double-blind, placebo-controlled trial of oral glycerol in adults with bacterial meningitis. Patients with clinical and cerebrospinal fluid findings suggestive of bacterial meningitis were randomly assigned in blocks of 12 by use of a random number list produced by an independent statistician to receive either glycerol or an equivalent volume of sugar solution. Glycerol and placebo were indistinguishable by colour or taste. The primary outcome was mortality at 40 days, with secondary outcomes including disability and mortality restricted to pneumococcal disease. All patients were analysed for the primary outcome excluding those who were lost to follow-up. This trial is registered at controlled-trials.com, number ISRCTN70121840.

FINDINGS

75 mL glycerol four times a day was the highest tolerated dose, and was used for the main study. 265 patients were assigned treatment: 137 glycerol and 128 placebo. The trial was stopped early on the advice of the data and safety monitoring board after a planned interim analysis. By day 40, 61 (49%) of 125 patients in the placebo group and 86 (63%) of 136 in the glycerol group had died (adjusted odds ratio 2.4, 95% CI 1.3-4.2, p=0.003). There was no benefit from glycerol for death and disability by day 40, and glycerol did not improve death and disability by day 40 or death at day 40 in patients with proven bacterial disease or pneumococcal disease. Two serious adverse events occurred that were possibly due to the study drug.

INTERPRETATION

Oral glycerol therapy cannot be recommended as an adjuvant therapy in adults with bacterial meningitis in resource-poor settings with a high HIV prevalence.

FUNDING

Meningitis Research Foundation.

Sterilization of glycerin

PURPOSE

The sterilization of glycerin is described.

SUMMARY

Glycerin is used in a wide variety of pharmaceutical formulations, including oral, otic, ophthalmic, topical, and parenteral preparations. Of the myriad uses for glycerin, some require a sterile solution. Due to the nature of dry heat sterilization with resulting equipment and validation needs, sterile filtration is the preferred sterilization method for glycerin at the Mayo Clinic Pharmacy Services Production Laboratory in Rochester, Minnesota. A practical procedure was attained with the use of a chemically compatible 0.22-microm capsule filter, peristaltic pump, and sterile tubing. The sterile tubing is attached firmly, with a twisting motion, to the hose barb ends of the filter. The peristaltic pump is set at minimum speed, and a sterile syringe is used to capture the sterile glycerin filtrate. After filtration, filter integrity testing using the bubble point test is performed on the filter used to sterilize the solution. Packaging was then completed by placing glycerin aliquots into unit-of-use sterile syringes, placing a sterile tip cap on each syringe, and labeling the syringe. End testing is needed for preparations, such as sterile glycerin, that are made from nonsterile components, regardless of sterilization technique. This quality-control testing includes but is not limited to visual checks, pH checks, and tests for bacterial endotoxins, particulate matter, and sterility. Beyond-use dating is then assigned based on chemical, physical, microbiological, and packaging considerations.

CONCLUSION

A practical method for sterilization of glycerin by compounding pharmacists is attainable through the use of membrane filtration. Sterility assurance is achieved through appropriate validation, and quality-control checks must be completed before release of the injectable preparation.

Prescription of anti-oedema agents and short-term mortality in older patients with acute ischaemic stroke

BACKGROUND AND OBJECTIVE

In Western countries, stroke is the third most common cause of death and one of the main causes of disability in individuals aged over 65 years. Mortality at 1 month after stroke is still high, at around 25-30%. Despite the widespread use of anti-oedema agents in clinical practice, there are only a few studies that have investigated the effect of these drugs on stroke outcome. In this study we evaluated the effect of intravenously administered glycerol or mannitol individually and in combination with corticosteroids, on short-term mortality (30 days). The sample included patients aged over 65 years who were admitted to hospital for acute ischaemic stroke.

STUDY DESIGN

This was a retrospective cohort study. The odds ratio, estimated by means of multivariate logistic regression method, was used to compare short-term mortality risk across treatment groups after adjusting for possible confounders.

METHODS

This study included 442 consecutive patients aged over 65 years with severe ischaemic stroke who were admitted to either the University School of Internal Medicine (Ferrara) or the Geriatric Department (Perugia), Italy, over a 4-year period (1996-2000). All patients underwent a computed tomography (CT) scan of the brain within 72 hours of admission. Stroke type was classified according to the system used by the Oxfordshire Community Stroke Project. The data recorded included: (i) clinical features of stroke; (ii) detailed medical history, including vascular risk factors (arterial hypertension, diabetes mellitus, atrial fibrillation, coronary heart disease, congestive heart failure, alcohol abuse, smoking, previous transient ischaemic attacks or stroke); (iii) 12-lead ECG; and (iv) routine blood analysis and urine tests.

RESULTS

No reduction in short-term mortality risk was observed in patients treated with intravenous (IV) glycerol. However, an increase in short-term mortality risk was observed in the patients who were concurrently treated with IV corticosteroids. Similarly, treatment with mannitol did not reduce the risk of short-term mortality; however, concurrent treatment with IV corticosteroids did not show a significant rise in short-term mortality risk. When treatment with IV glycerol and mannitol was considered together, the treatment did not decrease short-term mortality risk, while concurrent therapy with corticosteroids was associated with an increase in short-term mortality risk.

CONCLUSION

This study does not support the use of IV osmotic agents such as glycerol or mannitol in the prevention of short-term mortality in older patients with acute ischaemic stroke. Furthermore, our data suggest a possible harmful effect of IV corticosteroids on short-term mortality risk.

Glycerol for acute stroke

BACKGROUND

Brain oedema is a major cause of early death after stroke. A 10% solution of glycerol is a hyperosmolar agent that is claimed to reduce brain oedema.

OBJECTIVES

To determine whether intravenous (I.V.) glycerol treatment in acute stroke, either ischaemic or haemorrhagic, influences death rates and functional outcome in the short or long term, and whether the treatment is safe.

SEARCH STRATEGY

The Cochrane Stroke Group trials register was searched (January 2003), and some trialists were personally contacted.

SELECTION CRITERIA

All completed, randomised and quasi-randomised, controlled, published and unpublished comparisons, evaluating clinical outcome in which I.V. glycerol treatment was initiated within the first days after stroke onset.

DATA COLLECTION AND ANALYSIS

Two reviewers independently applied the inclusion criteria, assessed the trial quality and extracted data and this was checked with all co-reviewers. Death from all causes, functional outcome, and adverse effects were analysed.

MAIN RESULTS

Eleven completed, randomised trials comparing I.V. glycerol and control were considered. Analysis of death during the scheduled treatment period for acute ischaemic and/or haemorrhagic stroke was possible in 10 trials where 482 glycerol treated patients were compared with 463 control patients. Glycerol was associated with a non-significant reduction in the odds of death within the scheduled treatment period (Odds Ratio (OR) 0.78, 95% Confidence Intervals (CI) 0.58 to 1.06). Among patients with definite or probable ischaemic stroke, glycerol was associated with a significant reduction in the odds of death during the scheduled treatment period (OR 0.65, 95% CI 0.44 to 0.97). However, at the end of the scheduled follow up period, there was no significant difference in the odds of death (OR 0.98, 95% CI 0.73 to 1.31). Functional outcome was reported in only two studies but there were non-significantly more patients who had a good outcome at the end of scheduled follow up (OR 0.73, 95% CI 0.37 to 1.42). Haemolysis seems to be the only relevant adverse effect of glycerol treatment.

REVIEWERS' CONCLUSIONS

This systematic review suggests a favourable effect of glycerol treatment on short term survival in patients with probable or definite ischaemic stroke but the confidence intervals were wide and the magnitude of the treatment effect may be only minimal. Due to the relatively small number of patients, and that the trials were performed in the pre-CT era, the results must be interpreted cautiously. The lack of evidence of benefit in long term survival does not support the routine or selective use of glycerol treatment in patients with acute stroke.

Effect of glycerol on ischemic cerebral edema assessed by magnetic resonance imaging

The aim of this study is to assess the anticerebral edema effect of glycerol on a large cerebral infarction with magnetic resonance imaging (MRI). Glycerol, which is widely used as an osmotic agent against cerebral edema, could exacerbate brain tissue shift, since it has been suggested that glycerol might shrink a noninfarcted hemisphere and worsen the mass effect after a large hemispheric cerebral infarction. To investigate these issues, changes in a large hemispheric infarction with cerebral edema were studied using MRI before and after glycerol administration. Infarct volumes, normal brain tissue volumes and lateral ventricle volumes, in addition to signal intensities of T(2)-weighted images, were measured in six patients before and after administration of 300 ml of glycerol. Ventricle volumes were significantly increased (p=0.0015) and the T(2) signal intensity of the post-treatment ischemic region decreased after glycerol administration. In contrast, no significant differences in either cerebral volume or T(2) signal intensity were seen in the noninfarcted hemisphere before and after administration. Our data suggest that glycerol does not exacerbate the mass effect on a large hemispheric infarction.

Management of large hemispheric strokes in the neurological intensive care unit

BACKGROUND

Patients with large hemispheric strokes frequently develop neurologic deterioration secondary to cerebral edema. Despite supportive care in the intensive care unit and traditional forms of therapy for cerebral edema, they have a high morbidity and mortality. New forms of therapy are being investigated to improve outcome in these patients.

REVIEW SUMMARY

This article begins with a discussion of the clinical and radiologic features of large hemispheric strokes. The role of increased intracranial pressure in neurologic deterioration and the predictors of outcome in these patients are reviewed. The various therapeutic options for management of cerebral edema in these patients, including the role of osmotic therapy, hypothermia, and hemicraniectomy, are explored.

CONCLUSIONS

Neurologic deterioration in patients with large hemispheric strokes necessitates admission to the intensive care unit for management of the airway, blood pressure, and cerebral edema. New promising therapies, such as hemicraniectomy and hypothermia, need to be further evaluated to define their role in the management of these patients.

Ischaemic brain oedema

Ischaemic brain oedema appears to involve two distinct processes, the relative contribution and time course of which depend on the duration and severity of ischaemia, and the presence of reperfusion. The first process involves an increase in tissue Na+ and water content accompanying increased pinocytosis and Na+, K+ ATPase activity across the endothelium. This is apparent during the early phase of infarction and before any structural damage is evident. This phenomenon is augmented by reperfusion. A second process results from a more indiscriminate and delayed BBB breakdown that is associated with infarction of both the parenchyma and the vasculature itself. Although, tissue Na+ level still seems to be the major osmotic force for oedema formation at this second stage, the extravasation of serum proteases is an additional potentially deleterious factor. The relative importance of protease action is not yet clear, however, degradation of the extracellular matrix conceivably leads to further BBB disruption and softening of the tissue, setting the stage for the most pronounced forms of brain swelling. A number of factors mediate or modulate ischaemic oedema formation, however, most current information comes from experimental models, and clinical data on this microcosmic level is lacking. Clinically significant brain oedema develops in a delayed fashion after large hemispheric strokes and is a cause of substantial mortality. Neurological signs appear to be at least as good as direct ICP measurement and neuroimaging in detecting and gauging the secondary damage produced by stroke oedema. The neuroimaging characteristics of the stroke, specifically the early involvement of greater than half of the MCA territory, are, however, highly predictive of the development of severe oedema over the subsequent hours and days. None of the available medical therapies provide substantial relief from the oedema and raised ICP, or at best, they are temporizing in most cases. Hemicraniectomy appears most promising as a method of avoiding death from brain compression, but the optimum timing and manner of patient selection are currently being investigated. All approaches to massive ischaemic brain swelling are clouded by the potential for survival with poor functional outcome. It is possible to manage blood pressure, serum osmolarity by way of selective fluid administration, and a number of other systemic factors that exaggerate brain oedema. Broad guidelines for treatment of stroke oedema can therefore be given at this time.

[First Brazilian consensus for the management of the acute phase of cerebral vascular accidents]

The cerebrovascular diseases have a high incidence, and they cause an enormous social and economic burden. With the increasing knowledge of the pathophysiology of the ischemic insult, and the possibility of the thrombolysis in the acute phase, the management of the stroke patients is considered an emergency. This consensus is the result of a recent meeting to establish a better approach to these patients. This is the official guideline for the management of patients with acute stroke of the Brazilian Cerebrovascular Disease Society.

Glycerol for acute ischaemic stroke

BACKGROUND

Infarct-related oedema following ischaemic stroke is thought to be a major cause of early death. Intravenous glycerol may reduce the oedema, increase cerebral blood flow and improve cerebral metabolism.

OBJECTIVES

The objective of this review was to assess the effect of glycerol in acute ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group trials register, Medline and Embase.

SELECTION CRITERIA

Randomised trials of intravenous glycerol compared with control in people with definite or presumed ischaemic stroke. Trials were included if treatment was initiated within the first four days of stroke onset.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed trial quality and independently extracted the data.

MAIN RESULTS

Eight trials involving 649 people were included. Based on 454 patients in six trials, glycerol was associated with a decrease in deaths within 14 days of stroke onset (odds ratio of 0.58, 95% confidence interval 0.36 to 0.91). Based on 431 patients in five trials, there was a non-significant decrease in deaths within the first year of stroke onset (odds ratio of 0.82, 95% confidence interval 0.54 to 1.23). The effect of treatment on functional outcome was not clear. Haemolysis appeared to be the only adverse effect.

REVIEWER'S CONCLUSIONS

There is not enough evidence to evaluate glycerol treatment for people with acute ischaemic stroke.

Osmotherapy for elevated intracranial pressure: a critical reappraisal

The administration of osmotic agents is one of the principal strategies to lower elevated intracranial pressure (ICP) and to increase cerebral perfusion pressure. Of the 3 osmotic agents frequently used (mannitol, glycerol and sorbitol), each has characteristic advantages and disadvantages. In addition to renal filtration, sorbitol [elimination half-life (t1/2beta) approximately 1h] and glycerol (t1/2beta 0.2 to 1h) are metabolised, mainly by the liver. The risk of these compounds accumulating in patients with renal insufficiency is low. However, both compounds frequently affect glucose metabolism, leading to an increase in the serum glucose concentration. Mannitol is almost exclusively renally filtered and possesses the slowest elimination from serum (t1/2beta 2 to 4h). The t1/2beta of mannitol is markedly increased in patients with renal insufficiency, but it does not interfere with glucose metabolism. Entry into the cerebrospinal fluid (CSF) is highest with glycerol [CSF: serum ratio of the areas under the concentration-time curves (AUC(CSF): AUCs) approximately 0.25], intermediate with mannitol (AUC(CSF): AUCs approximately 0.15) and lowest with sorbitol (AUC(CSF): AUCs approximately 0.10). The elimination of all osmotic agents from the CSF compartment is substantially slower than from serum. During the elimination phase, the CSF-to-serum osmotic gradient is temporarily reversed. This is one cause of the paradoxical rise of ICP above the pretreatment level sometimes observed with osmotherapeutics. The ability of mannitol, glycerol and sorbitol to lower elevated ICP has been extensively documented. However, whether the use of osmotic agents, particularly with repeated application, improves outcome remains unproven. Therefore, these agents should only be used to treat manifest elevations of ICP, not for prophylaxis of brain oedema.

Assessment of brain tissue viability under clinical circumstances

The growing body of clinical and instrumental information that can be gathered from the earliest phases of stroke has radically modified the way in which neurologists tackle the treatment of stroke patients. It is now theoretically possible to tailor therapeutic choices on the basis of prognostic estimates made within a few hours of stroke onset, that is at a time when numerous options to limit the ischemic insult are still open. However, once many hours or even days have passed, all one can do is witness the effects of a natural course which by then is virtually unmodifiable. This applies not only to stroke patients being treated within the context of pharmacological trials, but also to those in daily clinical management, since some choices, such as when and how to treat brain oedema and give thrombolytics, may now be made earlier and more accurately than in the past. Emergency CT in particular discloses important indices of subsequent clinical evolution and outcome, thus adding to already well-known predictors such as age and severity of neurological status at hospital admission [20]. CT does have the aforementioned limitations regarding inter-observer agreement, which may, however, be minimised by an appropriate training of observers. Moreover it has intrinsic limitations regarding the visualisation of the actual brain tissue damage, since up to one fifth of patients with no or very limited early CT signs may present symptomatic hemorrhagic transformation after thrombolysis [23] and approximately one sixth of early deteriorating patients do not show early CT signs [52]. Other techniques, such as positron and single photon emission tomography and in particular MR imaging, which may shed light on tissue viability and perfusion as well as arterial patency simultaneously, might be able to provide more accurate information [19] Nevertheless, CT is still the most widely used tool in clinical centres which hospitalise stroke patients, and is unlikely to be routinely replaced by the other imaging devices in the foreseeable future. Consequently, there is an urgent need both for a general consensus on the identification criteria of early CT signs and for the widest possible awareness of knowledge regarding CT capabilities among neurologists [47], waiting for the wide applicability of newer technologies.

A mouse model to test the in vivo efficacy of chemical chaperones

In vitro studies in transfected cells have indicated that chemical chaperones including glycerol (0.5-1.2 M) and trimethylamine oxide (TMAO, 50-100 mM) can correct defective trafficking of some proteins, including deltaF508 CFTR in cystic fibrosis and AQP2 mutants in nephrogenic diabetes insipidus. To develop a mouse model to test the efficacy of chemical chaperones in vivo, glycerol and TMAO were administered by intraperitoneal (i.p.), subcutaneous (s.c.), and oral routes. Glycerol and TMAO assays that utilized 1-5 microL of tail vein blood were developed. Administration by the i.p. and s.c. routes gave maximum serum glycerol concentrations of approximately 100 mM, levels that were well below the effective in vitro concentrations. Single i.p. or s.c. doses of TMAO (7 g/kg, 8% solution in water) resulted in serum [TMAO] greater than 50 mM, with a long half-life (t1/2 approximately equal to 18-21 h). Sustained high serum and tissue [TMAO] > 52 mM for 3 days was achieved by s.c. administration of TMAO (7 g/kg) in water every 8 h. Although approximately 50% of the mice died with this multiple-dose regimen, the remaining mice had nearly normal liver, renal, and pancreatic function. A lower dose of TMAO (5 g/kg) given by the s.c. route every 8 h resulted in serum [TMAO] concentration of 22 mM, a level that was well tolerated by all mice for 72 h. These mice also had high [TMAO] in urine, 400 mM. These results demonstrate that potentially therapeutic concentrations of TMAO can be sustained in mice in vivo, permitting the testing of chemical chaperones in transgenic mouse models of diseases caused by defective protein trafficking.