Evidence for Mannitol as an Effective Agent Against Intracranial Hypertension: An Individual Patient Data Meta-analysis

Pharmacotherapy in SAH: Clinical Trial Lessons

Subarachnoid Haemorrhage (SAH) is a medical emergency with potentially devastating outcomes. It is without doubt that over the past decades, there has been a radical change in the approach towards patients with SAH, both in terms of the surgical as well as of the pharmacological treatments offered. The present review aims to outline the principal data regarding the best practice in the pharmacotherapy of SAH, as well as to sum up the emerging evidence from the latest clinical trials. To date, nimodipine is the only evidence-based treatment of vasospasm. However, extensive research is currently underway to identify novel substances with magnesium sulphate, cilostazol, clazosentan and fasudil, demonstrating promising results. Antifibrinolytic therapy could help reduce mortality, and anticoagulants, in spite of their associated hazards, could actually reduce the incidence of delayed cerebral ischemia. The effectiveness of triple-H therapy has been challenged, yet evidence on the optimal regimen is still pending. Statins may benefit some patients by reducing the incidence of vasospasm and delayed ischemic events. As several clinical trials are underway, it is expected that in the years to come, more therapeutic options will be added to the attending physician's armamentarium.

Mannitol Anaphylaxis in the Setting of Septic Emboli-Induced Intracranial Hemorrhage

Neurological complications are a significant problem in bacterial endocarditis. Cerebral embolism is the most frequent concern. Acute embolic disease may trigger focal seizures or mycotic aneurysms. Miliary infection is also common, and lumbar puncture can guide in determining the infective organism. Purulent cerebrospinal fluid (CSF) consists often of Staphylococcus aureus, a virulent organism, whereas non-virulent organisms (i.e., viridans streptococci) have normal CSF formulae. Microscopic abscesses suggest the potential for aneurysm from bacterial endocarditis amplifying the risk of intracranial hemorrhage. Mannitol and hypertonic (3%) saline are intravenous medications used as a rescue treatment for brain hemorrhage. A patient diagnosed with mycoplasma pneumonia and septic shock secondary to tricuspid endocarditis with extensive pulmonary emboli and metastatic infection to his spine was initiated on antibiotics. He developed a massive intracranial bleed from the rupture of mycotic septic emboli and was given mannitol to decrease intracranial pressure, which caused anaphylaxis.

Management of moderate to severe traumatic brain injury: an update for the intensivist

Traumatic brain injury (TBI) remains one of the most fatal and debilitating conditions in the world. Current clinical management in severe TBI patients is mainly concerned with reducing secondary insults and optimizing the balance between substrate delivery and consumption. Over the past decades, multimodality monitoring has become more widely available, and clinical management protocols have been published that recommend potential interventions to correct pathophysiological derangements. Even while evidence from randomized clinical trials is still lacking for many of the recommended interventions, these protocols and algorithms can be useful to define a clear standard of therapy where novel interventions can be added or be compared to. Over the past decade, more attention has been paid to holistic management, in which hemodynamic, respiratory, inflammatory or coagulation disturbances are detected and treated accordingly. Considerable variability with regards to the trajectories of recovery exists. Even while most of the recovery occurs in the first months after TBI, substantial changes may still occur in a later phase. Neuroprognostication is challenging in these patients, where a risk of self-fulfilling prophecies is a matter of concern. The present article provides a comprehensive and practical review of the current best practice in clinical management and long-term outcomes of moderate to severe TBI in adult patients admitted to the intensive care unit.

Incorporating Baseline Outcome Data in Individual Participant Data Meta-Analysis of Non-randomized Studies

Background

In non-randomized studies (NRSs) where a continuous outcome variable (e.g., depressive symptoms) is assessed at baseline and follow-up, it is common to observe imbalance of the baseline values between the treatment/exposure group and control group. This may bias the study and consequently a meta-analysis (MA) estimate. These estimates may differ across statistical methods used to deal with this issue. Analysis of individual participant data (IPD) allows standardization of methods across studies. We aimed to identify methods used in published IPD-MAs of NRSs for continuous outcomes, and to compare different methods to account for baseline values of outcome variables in IPD-MA of NRSs using two empirical examples from the Thyroid Studies Collaboration (TSC).

Methods

For the first aim we systematically searched in MEDLINE, EMBASE, and Cochrane from inception to February 2021 to identify published IPD-MAs of NRSs that adjusted for baseline outcome measures in the analysis of continuous outcomes. For the second aim, we applied analysis of covariance (ANCOVA), change score, propensity score and the naïve approach (ignores the baseline outcome data) in IPD-MA from NRSs on the association between subclinical hyperthyroidism and depressive symptoms and renal function. We estimated the study and meta-analytic mean difference (MD) and relative standard error (SE). We used both fixed- and random-effects MA.

Results

Ten of 18 (56%) of the included studies used the change score method, seven (39%) studies used ANCOVA and one the propensity score (5%). The study estimates were similar across the methods in studies in which groups were balanced at baseline with regard to outcome variables but differed in studies with baseline imbalance. In our empirical examples, ANCOVA and change score showed study results on the same direction, not the propensity score. In our applications, ANCOVA provided more precise estimates, both at study and meta-analytical level, in comparison to other methods. Heterogeneity was higher when change score was used as outcome, moderate for ANCOVA and null with the propensity score.

Conclusion

ANCOVA provided the most precise estimates at both study and meta-analytic level and thus seems preferable in the meta-analysis of IPD from non-randomized studies. For the studies that were well-balanced between groups, change score, and ANCOVA performed similarly.

Utilizing yeasts for the conversion of renewable feedstocks to sugar alcohols - a review

Sugar alcohols are widely marketed compounds. They are useful building block chemicals and of particular value as low- or non-calorigenic sweeteners, serving as sugar substitutes in the food industry. To date most sugar alcohols are produced by chemical routes using pure sugars, but a transition towards the use of renewable, non-edible feedstocks is anticipated. Several yeasts are naturally able to convert renewable feedstocks, such as lignocellulosic substrates, glycerol and molasses, into sugar alcohols. These bioconversions often face difficulties to obtain sufficiently high yields and productivities necessary for industrialization. This review provides insight into the most recent studies on utilizing yeasts for the conversion of renewable feedstocks to diverse sugar alcohols, including xylitol, erythritol, mannitol and arabitol. Moreover, metabolic approaches are highlighted that specifically target shortcomings of sugar alcohol production by yeasts from these renewable substrates.

Danhong injection enhances the therapeutic effect of mannitol on hemispheric ischemic stroke by ameliorating blood-brain barrier disruption

Mannitol, a representative of hyperosmolar therapy, is indispensable for the treatment of malignant cerebral infarction, but its therapeutic effect is limited by its exacerbation of blood-brain barrier (BBB) disruption. This study was to explore whether Danhong injection (DHI), a standardized product extracted from Salvia miltiorrhiza Bunge and Carthamus tinctorius L., inhibits the destructive effect of mannitol on BBB and thus enhancing the treatment of hemispheric ischemic stroke. SD rats were subjected to pMCAO followed by intravenous bolus injections of mannitol with/without DHI intervention. Neurological deficit score, brain edema, infarct volume at 24 h after MCAO and histopathology, microvascular ultrastructure, immunohistochemistry and immunofluorescence staining of endothelial cell junctions, energy metabolism in the ischemic penumbra were assessed. Intravenous mannitol after MCAO resulted in a decrease in 24 h mortality and cerebral edema, whereas no significant benefit on neurological deficits, infarct volume and microvascular ultrastructure. Moreover, mannitol led to the loss of endothelial integrity, manifested by the decreased expression of occludin, junctional adhesion molecule-1 (JAM-1) and zonula occluden-1 (ZO-1) and the discontinuity of occludin staining around the periphery of endothelial cells. Meanwhile, after mannitol treatment, energy-dependent vimentin and F-actin, ATP content, and ATP5D expression were down-regulated, while MMP2 and MMP9 expression increased in the ischemic penumbra. All the insults after mannitol treatment were attenuated by addition of intravenous DHI. The results suggest DHI as a potential remedy to attenuate mannitol-related BBB disruption, and the potential of DHI to upregulate energy metabolism and inhibit the activity of MMPs is likely attributable to its effects observed.

Improved Pressure Equalization Ratio Following Mannitol Administration in Patients With Severe TBI: A Preliminary Study of a Potential Bedside Marker for Response to Therapy

BACKGROUND

Performing a cerebrospinal fluid (CSF) drainage challenge can be used to measure the pressure equalization (PE) ratio, which describes the extent to which CSF drainage can equalize pressure to the height of the external ventricular drain and may serve as a correlate of cerebral edema. We sought to assess whether treatment with mannitol improves PE ratio in patients with severe traumatic brain injury (TBI) with elevated intracranial pressure (ICP).

METHODS

We studied consecutive patients with TBI and brain edema on computed tomography scan and an external ventricular drain (EVD), admitted to the neurointensive care unit. PE ratio, defined as ICP prior to CSF drainage minus ICP after CSF drainage divided by ICP prior to CSF drainage minus EVD height, was measured as previously described. Patients were treated with mannitol for raised ICP based on clinical indication and PE ratio measured before and after mannitol administration.

RESULTS

We studied 20 patients with severe TBI with raised ICP. Mean ICP prior to mannitol treatment was 29 ± 7 mm Hg. PE ratio rose substantially after mannitol treatment (0.62 ± 0.24 vs. 0.29 ± 0.20, p < 0.0001), indicating an improved ability to drain CSF and equalize ICP with the preset height of the EVD. The combination of mannitol and CSF drainage led to an improved reduction in ICP compared with that seen before mannitol therapy (11 ± 2 mm Hg vs. 6 ± 2 mm Hg, p < 0.01), and led to a decrease in ICP below the 20 mm Hg threshold in 77% of cases.

CONCLUSIONS

Treatment with mannitol leads to a substantial improvement in PE ratio that reflects the ability to achieve a greater decrease in ICP when CSF drainage is performed after mannitol administration. This preliminary study raises the possibility that PE ratio may be useful to follow response to therapy in patients with cerebral edema and raised ICP. Further studies to determine whether PE ratio may serve as an easily obtained and clinically useful surrogate marker for the extent of brain edema are warranted.

Traumatic Brain Injury-A Review of Intravenous Fluid Therapy

This manuscript will review intravenous fluid therapy in traumatic brain injury. Both human and animal literature will be included. Basic treatment recommendations will also be discussed.

Equimolar doses of hypertonic agents (saline or mannitol) in the treatment of intracranial hypertension after severe traumatic brain injury

BACKGROUND

Mannitol and hypertonic saline (HTS) are effective in reducing intracranial pressure (ICP) after severe traumatic brain injury (TBI). However, their efficacy on the ICP has not been evaluated rigorously.

OBJECTIVE

To evaluate the efficacy of repeated bolus dosing of HTS and mannitol in similar osmotic burdens to treat intracranial hypertension (ICH) in patients with severe TBI.

METHODS

The authors used an alternating treatment protocol to evaluate the efficacy of HTS with that of mannitol given for ICH episodes in patients treated for severe TBI at their hospital during 2017 to 2019. Doses of similar osmotic burdens (20% mannitol, 2 ml/kg, or 10% HTS, 0.63 ml/kg, administered as a bolus via a central venous catheter, infused over 15 minutes) were given alternately to the individual patient with severe TBI during ICH episodes. The choice of osmotic agents for the treatment of the initial ICH episode was determined on a randomized basis; osmotic agents were alternated for every subsequent ICH episode in each individual patient. intracranial pressure (ICP), mean arterial pressure (MAP), and cerebral perfusion pressure (CPP) were continuously monitored between the beginning of each osmotherapy and the return of ICP to 20 mm Hg. The duration of the effect of ICP reduction (between the beginning of osmotherapy and the return of ICP to 20 mm Hg), the maximum reduction of ICP and its time was recorded after each dose. Serum sodium and plasma osmolality were measured before, 0.5 hours and 3 hours after each dose. Adverse effects such as central pontine myelinolysis (CPM), severe fluctuations of serum sodium and plasma osmolality were assessed to evaluate the safety of repeated dosing of HTS and mannitol.

RESULTS

Eighty three patients with severe TBI were assessed, including 437 ICH episodes, receiving 236 doses of HTS and 221 doses of mannitol totally. There was no significant difference between equimolar HTS and mannitol boluses on the magnitude of ICP reduction, the duration of effect, and the time to lowest ICP achieved (P > .05). The proportion of efficacious boluses was higher for HTS than for mannitol (P = .016), as was the increase in serum sodium (P = .038). The serum osmolality increased immediately after osmotherapy with a significant difference (P = .017). No cases of CPM were detected.

CONCLUSION

Repeat bolus dosing of 10% HTS and 20% mannitol appears to be significantly and similarly effective for treating ICH in patients with severe TBI. The proportion of efficacious doses of HTS on ICP reduction may be higher than mannitol.

Harnessing Adaptive Evolution to Achieve Superior Mannitol Production by Lactococcus lactis Using Its Native Metabolism

Mannitol can be obtained as a by-product of certain heterolactic lactic acid bacteria, when grown on substrates containing fructose. Lactococcus lactis, a homolactic lactic acid bacterium, normally does not form mannitol but can be persuaded into doing so by expressing certain foreign enzyme activities. In this study, we find that L. lactis has an inherent capacity to form mannitol from glucose. By adaptively evolving L. lactis or derivatives blocked in NAD⁺ regenerating pathways, we manage to accelerate growth on mannitol. When cells of the adapted strains are resuspended in buffer containing glucose, 4-58% of the glucose metabolized is converted into mannitol, in contrast to nonadapted strains. The highest conversion was obtained for a strain lacking all major NAD⁺ regenerating pathways. Mannitol had an inhibitory effect on the conversion, which we speculated was due to the mannitol uptake system. After its inactivation, 60% of the glucose was converted into mannitol by cells suspended in glucose buffer. Using a two-stage setup, where biomass first was accumulated by aerated culturing, followed by a nonaerated phase (static conditions), it was possible to obtain 6.1 g/L mannitol, where 60% of the glucose had been converted into mannitol, which is the highest yield reported for L. lactis.

Hyperosmolar therapy for acute brain injury: study protocol for an umbrella review of meta-analyses and an evidence mapping

INTRODUCTION

Acute brain injury is a challenging public health problem worldwide. Elevated intracranial pressure is a common complication after acute brain injury. Hyperosmolar therapy is one of the main therapeutic strategies for the management of intracranial hypertension. This study protocol outlines an umbrella review of meta-analyses which will investigate the benefits and harms of hyperosmolar therapy routinely used for the management of acute brain injury in the intensive care.

METHODS AND ANALYSIS

We will search PubMed/MEDLINE, EMBASE and the Cochrane Database of Systematic Reviews. We will include meta-analyses of primary research studies (eg, randomised controlled trials, observational studies or both) that evaluate one or more hyperosmolar solutions (including hypertonic saline and/or mannitol) for the treatment of adult patients with acute brain injury of any severity. Two researchers will independently screen all citations, full-text articles and abstract data. Potential conflicts will be resolved through discussion with a third researcher. Primary outcomes will be mortality and neurological outcomes at discharge. Secondary outcomes will include control of intracranial pressure, cerebral perfusion pressure, length of stay (in hospital an intensive care unit) and any adverse event. Quality of the included meta-analyses will be assessed using the AMSTAR-2 tool. An overall summary of methods and results will be performed using tabular and graphical approaches and will be supplemented by narrative description. We will analyse whether published meta-analyses present an outline of available evidence (eg, cited, described and discussed any previous meta-analysis). Where objectives from two or more meta-analyses overlap, we will assess the causes of any noted discrepancies between meta-analyses.

ETHICS AND DISSEMINATION

No ethical approval will be required. Findings from this study will be published in a peer-reviewed journal. All data will be deposited in a cross-disciplinary public repository.

PROSPERO REGISTRATION NUMBER

CRD42019148152.