A Pilot Study of Normobaric Oxygen Therapy in Acute Ischemic Stroke

Associations of arterial oxygen partial pressure with all‑cause mortality in critically ill ischemic stroke patients: a retrospective cohort study from MIMIC IV 2.2

BACKGROUND

As a supportive treatment, the effectiveness of oxygen therapy in ischemic stroke (IS) patients remains unclear. This study aimed to evaluate the relationships between arterial partial pressure of oxygen (PaO2) and both consciousness at discharge and all-cause mortality risk in ICU IS patients.

METHODS

Blood gas measurements for all patients diagnosed with IS were extracted from the MIMIC-IV database. Patients were classified into four groups based on their average PaO2 during the first ICU day: hypoxemia (PaO2 < 80 mmHg), normoxemia (PaO2 80-120 mmHg), mild hyperoxemia (PaO2 121-199 mmHg), and moderate/severe hyperoxemia (PaO2 ≥ 200 mmHg). The primary endpoint was 90-day all-cause mortality. Secondary outcomes included the level of consciousness at discharge, assessed by the Glasgow Coma Scale (GCS), and 30-day all-cause mortality. Multivariate Cox regression and Restricted cubic spline (RCS) analysis were used to investigate the relationship between mean PaO2 and mortality, and to assess the nonlinear association between exposure and outcomes.

RESULTS

This study included a total of 946 IS patients. The cumulative incidence of 30-day and 90-day all-cause mortality increased with decreasing PaO2 levels. RCS analysis revealed a nonlinear relationship between PaO2 and the risk of 30-day all-cause mortality (nonlinear P < 0.0001, overall P < 0.0001), as well as a nonlinear association between PaO2 and 90-day all-cause mortality (nonlinear P < 0.0001, overall P < 0.0001). The results remained consistent after excluding the small subset of patients who received reperfusion therapy. Sensitivity analysis indicated that the favorable impact on survival tends to increase with the extended duration of elevated PaO2.

CONCLUSIONS

For IS patients who do not receive reperfusion therapy or whose recanalization status is unknown, a lower PaO2 early during ICU admission is considered an independent risk factor for short-term and recent mortality. Adjusting respiratory parameters to maintain supraphysiological levels of PaO2 appears to be beneficial for survival, although this finding requires further validation through additional studies.

TRIAL REGISTRATION

Not applicable.

Acute Ischemic Stroke in the Clinic and the Laboratory: Targets for Translational Research

Ischemic stroke research has enabled significant advancements in diagnosis, treatment, and management of this debilitating disease, yet challenges remain standing in the way of better patient prognoses. In this narrative review, a fictional case illustrates challenges and uncertainties that medical professionals still face - penumbra identification, lack of neuroprotective agents, side-effects of tissue plasminogen activator, dearth of molecular biomarkers, incomplete microvascular reperfusion or no-reflow, post-recanalization hyperperfusion, blood pressure management and procedural anesthetic effects. The current state of the field is broadly reviewed per topic, with the aim to introduce a broad audience (scientist and clinician alike) to recent successes in translational stroke research and pending scientific queries that are tractable for preclinical assessment. Opportunities for co-operation between clinical and experimental stroke experts are highlighted to increase the size and frequency of strides the field makes to improve our understanding of this disease and ways of treating it.

New Perspectives in Neuroprotection for Ischemic Stroke

The constant failure of new neuroprotective therapies for ischemic stroke has partially halted the search for new therapies in recent years, mainly because of the high investment risk required to develop a new treatment for a complex pathology, such as stroke, with a narrow intervention window and associated comorbidities. However, owing to recent progress in understanding the stroke pathophysiology, improvement in patient care in stroke units, development of new imaging techniques, search for new biomarkers for early diagnosis, and increasingly widespread use of mechanical recanalization therapies, new opportunities have opened for the study of neuroprotection. This review summarizes the main protective agents currently in use, some of which are already in the clinical evaluation phase. It also includes an analysis of how recanalization therapies, new imaging techniques, and biomarkers have improved their efficacy.

The neuroprotective effects of normobaric oxygen therapy after stroke

BACKGROUND

Stroke, including ischemic and hemorrhagic stroke, is a severe and prevalent acute cerebrovascular disease. The development of hypoxia following stroke can trigger a cascade of pathological events, including mitochondrial dysfunction, energy deficiency, oxidative stress, neuroinflammation, and excitotoxicity, all of which are often associated with unfavorable prognosis. Nonetheless, a noninvasive intervention, referred to as normobaric hyperoxia (NBO), is known to have neuroprotective effects against stroke.

RESULTS

NBO can exert neuroprotective effects through various mechanisms, such as the rescue of hypoxic tissues, preservation of the blood-brain barrier, reduction of brain edema, alleviation of neuroinflammation, improvement of mitochondrial function, mitigation of oxidative stress, reduction of excitotoxicity, and inhibition of apoptosis. These mechanisms may help improve the prognosis of stroke patients.

CONCLUSIONS

This review summarizes the mechanism by which hypoxia causes brain injury and how NBO can act as a neuroprotective therapy to treat stroke. We conclude that NBO has significant potential for treating stroke and may represent a novel therapeutic strategy.

Normobaric Hyperoxia Combined With Endovascular Treatment Based on Temporal Gradient: A Dose-Escalation Study

BACKGROUND

Normobaric hyperoxia (NBO) has neuroprotective effects in acute ischemic stroke. Thus, we aimed to identify the optimal NBO treatment duration combined with endovascular treatment.

METHODS

This is a single-center, randomized controlled, open-label, blinded-end point dose-escalation clinical trial. Patients with acute ischemic stroke who had an indication for endovascular treatment at Tianjin Huanhu Hospital were randomly assigned to 4 groups (1:1 ratio) based on NBO therapy duration: (1) control group (1 L/min oxygen for 4 hours); (2) NBO-2h group (10 L/min for 2 hours); (3) NBO-4h group (10 L/min for 4 hours); and (4) NBO-6h group (10 L/min for 6 hours). The primary outcome was cerebral infarction volume at 72 hours after randomization using an intention-to-treat analysis model. The primary safety outcome was the 90-day mortality rate.

RESULTS

Between June 2022 and September 2023, 100 patients were randomly assigned to the following groups: control group (n=25), NBO-2h group (n=25), NBO-4h group (n=25), and NBO-6h group (n=25). The 72-hour cerebral infarct volumes were 39.4±34.3 mL, 30.6±30.1 mL, 19.7±15.4 mL, and 22.6±22.4 mL, respectively (P=0.013). The NBO-4h and NBO-6h groups both showed statistically significant differences (adjusted P values: 0.011 and 0.027, respectively) compared with the control group. Compared with the control group, both the NBO-4h and NBO-6h groups showed significant differences (P<0.05) in the National Institutes of Health Stroke Scale scores at 24 hours, 72 hours, and 7 days, as well as in the change of the National Institutes of Health Stroke Scale scores from baseline to 24 hours. Additionally, there were no significant differences among the 4 groups in terms of 90-day mortality rate, symptomatic intracranial hemorrhage, early neurological deterioration, or severe adverse events.

CONCLUSIONS

The effectiveness of NBO therapy was associated with oxygen administration duration. Among patients with acute ischemic stroke who underwent endovascular treatment, NBO therapy for 4 and 6 hours was found to be more effective. Larger-scale multicenter studies are needed to validate these findings.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT05404373.

Effect of a helium and oxygen mixture on physiological parameters of rats with cerebral arterial air embolism

Introduction: Cerebral arterial air embolism (CAE) is a serious and potentially dangerous condition that can interrupt the blood supply to the brain and cause stroke. One of the promising gas mixtures for emergency treatment of air embolism is an oxygen-helium mixture. Methods: We modeled CAE in awake rats by injecting air into the common carotid artery. Immediately after CAE, animals were either untreated or underwent hyperbaria, oxygen inhalation, heated air inhalation, or helium-oxygen mixture inhalation. Body temperature, locomotor activity, respiratory and cardiovascular parameters were monitored in the animals before CAE modeling, and 3 and 24 h after CAE modeling. Results: After 3 hours of CAE modeling in awake rats, depression of the nervous, cardiovascular and respiratory systems, as well as decreased body temperature were observed. 24 h after CAE modeling multifocal cerebral ischemia was observed. Normobaric helium-oxygen mixture inhalation, on par with hyperbaric treatment, restored body temperature, locomotor activity, respiratory volume, respiratory rate, and blood pressure 3 hours after CAE, and prevented the formation of ischemic brain damage lesions 24 h after CAE. Discussion: Thus, inhalation of a heated oxygen-helium gas mixture (O2 30% and He 70%) immediately after CAE improves the physiological condition of the animals and prevents the foci of ischemic brain damage formation.

Normobaric hyperoxia therapy in acute ischemic stroke: A literature review

Background

Ischemic stroke is one of the most severe cerebrovascular diseases that leads to disability and death and seriously endangers health and quality of life. Insufficient oxygen supply is a critical factor leading to ischemic brain injury. However, effective therapies for ischemic stroke are lacking. Oxygen therapy has been shown to increase oxygen supply to ischemic tissues and improve prognosis after cerebral ischemia/reperfusion. Normobaric hyperoxia (NBHO) has been shown to have neuroprotective effects during ischemic stroke and is considered an appropriate neuroprotective therapy for ischemic stroke. Evidence indicates that NBHO plays a neuroprotective role through different mechanisms in acute ischemic stroke. Recent studies have also reported that combinations with other drug therapies can enhance the efficacy of NBHO in ischemic stroke. Here, we aimed to provide a summary of the potential mechanisms underlying the use of NBHO in ischemic stroke and an overview of the benefits of NBHO in ischemic stroke.

Methods

We screened 83 articles on PubMed and other websites. A quick review was conducted, including clinical trials, animal trials, and reviews of studies in the field of NBHO treatment published before July 1, 2023. The results were described and synthesized, and the bias risk and evidence quality of all included studies were assessed.

Results

The results were divided into four categories: the mechanism of NBHO, animal and clinical trials of NBHO, the clinical application and prospects of NBHO, and adverse reactions of NBHO.

Conclusion

NBHO is a simple, non-invasive therapy that may be delivered early after stroke onset, with promising potential for the treatment of acute ischemic stroke. However, the optimal therapeutic regimen remains uncertain. Further studies are needed to confirm its efficacy and safety.

Penumbral Rescue by normobaric O = O administration in patients with ischemic stroke and target mismatch proFile (PROOF): Study protocol of a phase IIb trial

RATIONALE

Oxygen is essential for cellular energy metabolism. Neurons are particularly vulnerable to hypoxia. Increasing oxygen supply shortly after stroke onset could preserve the ischemic penumbra until revascularization occurs.

AIMS

PROOF investigates the use of normobaric oxygen (NBO) therapy within 6 h of symptom onset/notice for brain-protective bridging until endovascular revascularization of acute intracranial anterior-circulation occlusion.

METHODS AND DESIGN

Randomized (1:1), standard treatment-controlled, open-label, blinded endpoint, multicenter adaptive phase IIb trial.

STUDY OUTCOMES

Primary outcome is ischemic core growth (mL) from baseline to 24 h (intention-to-treat analysis). Secondary efficacy outcomes include change in NIHSS from baseline to 24 h, mRS at 90 days, cognitive and emotional function, and quality of life. Safety outcomes include mortality, intracranial hemorrhage, and respiratory failure. Exploratory analyses of imaging and blood biomarkers will be conducted.

SAMPLE SIZE

Using an adaptive design with interim analysis at 80 patients per arm, up to 456 participants (228 per arm) would be needed for 80% power (one-sided alpha 0.05) to detect a mean reduction of ischemic core growth by 6.68 mL, assuming 21.4 mL standard deviation.

DISCUSSION

By enrolling endovascular thrombectomy candidates in an early time window, the trial replicates insights from preclinical studies in which NBO showed beneficial effects, namely early initiation of near 100% inspired oxygen during short temporary ischemia. Primary outcome assessment at 24 h on follow-up imaging reduces variability due to withdrawal of care and early clinical confounders such as delayed extubation and aspiration pneumonia.

TRIAL REGISTRATIONS

ClinicalTrials.gov: NCT03500939; EudraCT: 2017-001355-31.

Distinct Alterations in Oxygenation, Ion Composition and Acid-Base Balance in Cerebral Collaterals During Large-Vessel Occlusion Stroke

PURPOSE

Disturbances of blood gas and ion homeostasis including regional hypoxia and massive sodium (Na+)/potassium (K+) shifts are a hallmark of experimental cerebral ischemia but have not been sufficiently investigated for their relevance in stroke patients.

METHODS

We report a prospective observational study on 366 stroke patients who underwent endovascular thrombectomy (EVT) for large-vessel occlusion (LVO) of the anterior circulation (18 December 2018-31 August 2020). Intraprocedural blood gas samples (1 ml) from within cerebral collateral arteries (ischemic) and matched systemic control samples were obtained according to a prespecified protocol in 51 patients.

RESULTS

We observed a significant reduction in cerebral oxygen partial pressure (-4.29%, paO2ischemic = 185.3 mm Hg vs. paO2systemic = 193.6 mm Hg; p = 0.035) and K+ concentrations (-5.49%, K+ischemic = 3.44 mmol/L vs. K+systemic = 3.64 mmol/L; p = 0.0083). The cerebral Na+:K+ ratio was significantly increased and negatively correlated with baseline tissue integrity (r = -0.32, p = 0.031). Correspondingly, cerebral Na+ concentrations were most strongly correlated with infarct progression after recanalization (r = 0.42, p = 0.0033). We found more alkaline cerebral pH values (+0.14%, pHischemic = 7.38 vs. pHsystemic = 7.37; p = 0.0019), with a time-dependent shift towards more acidotic conditions (r = -0.36, p = 0.055).

CONCLUSION

These findings suggest that stroke-induced changes in oxygen supply, ion composition and acid-base balance occur and dynamically progress within penumbral areas during human cerebral ischemia and are related to acute tissue damage.

Normobaric Hyperoxia (NBHO): An Adjunctive Therapy to Cerebrovascular Recanalization in Ischemic Stroke

Acute ischemic stroke (AIS) is a serious neurological disease. Normobaric hyperoxia (NBHO) is both a non-invasive and easy method that seems to be able to improve outcomes after cerebral ischemia/reperfusion. In clinical trials, normal low-flow oxygen has been shown to be ineffective, but NBHO has been shown to have a transient brain-protective effect. Today, NBHO combined with recanalization is the best treatment available. NBHO combined with thrombolysis is considered to improve neurological scores and long-term outcomes. Large randomized controlled trials (RCTs), however, are still needed to determine the role they will have in stroke treatment. RCTs of NBHO combined with thrombectomy have both improved infarct volume at 24 hours and the long-term prognosis. These two mechanisms most likely play key roles in the neuroprotective actions of NBHO after recanalization, including the increase in penumbra oxygen supply and the integrity of the blood-brain barrier (BBB). Considering the mechanism of action of NBHO, oxygen should be given as early as possible to increase the duration of oxygen therapy before recanalization is initiated. NBHO can further prolong the existence time of penumbra, so that more patients may benefit from it. Overall, however, recanalization therapy is still essential.

Higher versus lower fractions of inspired oxygen or targets of arterial oxygenation for adults admitted to the intensive care unit

BACKGROUND

This is an updated review concerning 'Higher versus lower fractions of inspired oxygen or targets of arterial oxygenation for adults admitted to the intensive care unit'. Supplementary oxygen is provided to most patients in intensive care units (ICUs) to prevent global and organ hypoxia (inadequate oxygen levels). Oxygen has been administered liberally, resulting in high proportions of patients with hyperoxemia (exposure of tissues to abnormally high concentrations of oxygen). This has been associated with increased mortality and morbidity in some settings, but not in others. Thus far, only limited data have been available to inform clinical practice guidelines, and the optimum oxygenation target for ICU patients is uncertain. Because of the publication of new trial evidence, we have updated this review.

OBJECTIVES

To update the assessment of benefits and harms of higher versus lower fractions of inspired oxygen (FiO2) or targets of arterial oxygenation for adults admitted to the ICU.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, Science Citation Index Expanded, BIOSIS Previews, and LILACS. We searched for ongoing or unpublished trials in clinical trial registers and scanned the reference lists and citations of included trials. Literature searches for this updated review were conducted in November 2022.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared higher versus lower FiO2 or targets of arterial oxygenation (partial pressure of oxygen (PaO2), peripheral or arterial oxygen saturation (SpO2 or SaO2)) for adults admitted to the ICU. We included trials irrespective of publication type, publication status, and language. We excluded trials randomising participants to hypoxaemia (FiO2 below 0.21, SaO2/SpO2 below 80%, or PaO2 below 6 kPa) or to hyperbaric oxygen, and cross-over trials and quasi-randomised trials.

DATA COLLECTION AND ANALYSIS

Four review authors independently, and in pairs, screened the references identified in the literature searches and extracted the data. Our primary outcomes were all-cause mortality, the proportion of participants with one or more serious adverse events (SAEs), and quality of life. We analysed all outcomes at maximum follow-up. Only three trials reported the proportion of participants with one or more SAEs as a composite outcome. However, most trials reported on events categorised as SAEs according to the International Conference on Harmonisation Good Clinical Practice (ICH-GCP) criteria. We, therefore, conducted two analyses of the effect of higher versus lower oxygenation strategies using 1) the single SAE with the highest reported proportion in each trial, and 2) the cumulated proportion of participants with an SAE in each trial. Two trials reported on quality of life. Secondary outcomes were lung injury, myocardial infarction, stroke, and sepsis. No trial reported on lung injury as a composite outcome, but four trials reported on the occurrence of acute respiratory distress syndrome (ARDS) and five on pneumonia. We, therefore, conducted two analyses of the effect of higher versus lower oxygenation strategies using 1) the single lung injury event with the highest reported proportion in each trial, and 2) the cumulated proportion of participants with ARDS or pneumonia in each trial. We assessed the risk of systematic errors by evaluating the risk of bias in the included trials using the Risk of Bias 2 tool. We used the GRADEpro tool to assess the overall certainty of the evidence. We also evaluated the risk of publication bias for outcomes reported by 10b or more trials.

MAIN RESULTS

We included 19 RCTs (10,385 participants), of which 17 reported relevant outcomes for this review (10,248 participants). For all-cause mortality, 10 trials were judged to be at overall low risk of bias, and six at overall high risk of bias. For the reported SAEs, 10 trials were judged to be at overall low risk of bias, and seven at overall high risk of bias. Two trials reported on quality of life, of which one was judged to be at overall low risk of bias and one at high risk of bias for this outcome. Meta-analysis of all trials, regardless of risk of bias, indicated no significant difference from higher or lower oxygenation strategies at maximum follow-up with regard to mortality (risk ratio (RR) 1.01, 95% confidence interval (C)I 0.96 to 1.06; I2 = 14%; 16 trials; 9408 participants; very low-certainty evidence); occurrence of SAEs: the highest proportion of any specific SAE in each trial RR 1.01 (95% CI 0.96 to 1.06; I2 = 36%; 9466 participants; 17 trials; very low-certainty evidence), or quality of life (mean difference (MD) 0.5 points in participants assigned to higher oxygenation strategies (95% CI -2.75 to 1.75; I2 = 34%, 1649 participants; 2 trials; very low-certainty evidence)). Meta-analysis of the cumulated number of SAEs suggested benefit of a lower oxygenation strategy (RR 1.04 (95% CI 1.02 to 1.07; I2 = 74%; 9489 participants; 17 trials; very low certainty evidence)). However, trial sequential analyses, with correction for sparse data and repetitive testing, could reject a relative risk increase or reduction of 10% for mortality and the highest proportion of SAEs, and 20% for both the cumulated number of SAEs and quality of life. Given the very low-certainty of evidence, it is necessary to interpret these findings with caution. Meta-analysis of all trials indicated no statistically significant evidence of a difference between higher or lower oxygenation strategies on the occurrence of lung injuries at maximum follow-up (the highest reported proportion of lung injury RR 1.08, 95% CI 0.85 to 1.38; I2 = 0%; 2048 participants; 8 trials; very low-certainty evidence). Meta-analysis of all trials indicated harm from higher oxygenation strategies as compared with lower on the occurrence of sepsis at maximum follow-up (RR 1.85, 95% CI 1.17 to 2.93; I2 = 0%; 752 participants; 3 trials; very low-certainty evidence). Meta-analysis indicated no differences regarding the occurrences of myocardial infarction or stroke.

AUTHORS' CONCLUSIONS

In adult ICU patients, it is still not possible to draw clear conclusions about the effects of higher versus lower oxygenation strategies on all-cause mortality, SAEs, quality of life, lung injuries, myocardial infarction, stroke, and sepsis at maximum follow-up. This is due to low or very low-certainty evidence.

Ventilation Targets for Patients Undergoing Mechanical Thrombectomy for Acute Ischemic Stroke: A Systematic Review

Mechanical thrombectomy (MT) has become a standard treatment for acute ischemic stroke (AIS) caused by large vessel occlusion (LVO). Recent evidence suggests that general anesthesia (GA) and mechanical ventilation do not lead to inferior neurologic outcomes if compared to non-GA. However, the guidelines lack specific recommendations for ventilation targets during MT under GA. This systematic review aims to identify ventilation strategies correlating with better neurological outcomes in AIS patients undergoing MT, particularly focusing on oxygenation and carbon dioxide (CO2) targets. A systematic search of multiple databases was conducted to identify human studies reporting the correlation between ventilation strategies and neurological outcomes in MT for AIS. Eligible studies included clinical trials, observational studies, and case-control studies. Out of 157 studies assessed, 11 met the inclusion criteria. Five studies investigated oxygenation targets, while six studies explored CO2 targets. The published studies highlighted the controversial role of supplemental normobaric oxygen therapy and its potential association with worse outcomes. Regarding CO2 targets, the studies identified a potential association between end tidal CO2 levels and functional outcomes, with hypocapnia being unfavorable. This systematic review demonstrates that the current available evidence still lacks strength to suggest specific ventilation targets, but it highlights the potential risks of hyperoxia and hypocapnia in this specific cohort of patients.

Normobaric Hyperoxia Combined with Endovascular Treatment in Patients with Acute Ischemic Stroke (OPENS-2) Trial: Protocol for a Prospective, Multicenter, Randomized Controlled Study

Normobaric hyperoxia (NBO) is a potentially promising stroke treatment strategy that could protect the ischemic penumbra and could be administered as an adjunct before vascular recanalization. However, the efficacy and safety of NBO have not been confirmed by randomized controlled trials. The study aims to assess the efficacy and safety of NBO for ischemic stroke due to large artery occlusion (LVO) of acute anterior circulation among patients who had endovascular treatment (EVT) and were randomized within 6 h from symptom onset. Based on the data of the modified Rankin Scale (mRS) score at 90 days from the normobaric hyperoxia combined with EVT for acute ischemic stroke (OPENS: NCT03620370) trial, 284 patients will be included to achieve a 90% power by using Wilcoxon-Mann-Whitney test and the proportional odds model to calculate the sample size. The study is a prospective, multicenter, blinded, randomized controlled trial. The NBO group is administered with mask oxygen therapy of 10 L/min, while the sham NBO group is with that of 1 L/min. The primary outcome is the mRS score at 90 days. Secondary endpoints include cerebral infarct volume at 24-48 h, functional independence (mRS ≤2) at 90 days, and improvement in neurological function at 24 h. Safety outcomes include 90-day mortality, oxygen-related adverse events, and serious adverse events. This study will indicate whether NBO combined with EVT is superior to EVT alone for acute ischemic stroke caused by LVO in subjects randomized within 6 h from symptom onset and will provide some evidence for NBO intervention as an adjunct to thrombectomy for acute stroke.

Oxygen saturation before and after mechanical thrombectomy and functional outcome in patients with acute ischemic stroke

Background and purpose

Currently, there is a lack of effective neuroprotective strategies to break the ceiling effect of mechanical thrombectomy (MT), and one of the most promising is normobaric oxygen treatment. However, the impact of pre- and post-MT oxygen saturation on clinical outcomes in patients with acute ischemic stroke (AIS) remains unclear. We aimed to determine the influence of preoperative and postoperative oxygen saturation on 3-month poor outcome in patients with AIS.

Methods

A total of 239 consecutive stroke patients with successful recanalization by MT between May 2017 and March 2021 were analyzed. Oxygen saturation was measured non-invasively by pulse oximetry at baseline and continually after MT. Regression analysis was used to assess the association of preoperative and postoperative oxygen saturation with a 3-month poor outcome (modified Rankin Scale score: 3–6).

Results

Decreased preoperative oxygen saturation level was associated with an increased risk of poor outcome (odds ratio, 0.85; 95% CI, 0.73–0.98; P = 0.0293). Postoperative oxygen saturation had the opposite effect on poor outcome (odds ratio, 1.60; 95% CI, 1.13–2.27; P = 0.0088).

Conclusion

Preoperative and postoperative oxygen saturation have different impacts on 3-month poor outcome in patients with AIS with successful recanalization by MT.

Normobaric Hyperoxia Combined With Endovascular Treatment for Patients With Acute Ischemic Stroke: A Randomized Controlled Clinical Trial

BACKGROUND AND OBJECTIVES

To investigate the safety and efficacy of normobaric hyperoxia (NBO) combined with endovascular treatment (EVT) in patients with acute ischemic stroke (AIS).

METHODS

In this single-center, proof-of-concept, assessor-blinded, randomized, controlled pilot study, patients with AIS in the acute anterior circulation with large vessel occlusion who had an indication for EVT were randomly assigned to the EVT group or the NBO + EVT group. The NBO + EVT group was given 100% oxygen through a face mask initiated before vascular recanalization (10L/min for 4 hours), while the EVT group was given room air. The primary endpoint was infarct volume measured by MRI within 24-48 hours after randomization.

RESULTS

A total of 231 patients were screened, and 86 patients were randomized into a ratio of 1:1 (EVT group, n = 43; NBO + EVT group, n = 43). The median infarction volume of the NBO + EVT group at 24-48 hours after randomization was significantly smaller than that of the EVT group (median 20.1 vs 37.7 mL, p < 0.01). The median mRS score at 90 days was 2 for the NBO + EVT group when compared with 3 for the EVT group (adjusted value 1.8, 95% CI 1.3-4.2; p = 0.038). Compared with the EVT group, the NBO + EVT group had a lower incidence of symptomatic intracranial hemorrhagic (7% vs 12%), mortality (9% vs 16%), and adverse events (33% vs 42%); however, such a difference was not statistically significant.

DISCUSSION

NBO in combination with EVT seems to be a safe and feasible treatment strategy that could significantly reduce infarct volume, improve short-term neurobehavioral test score, and enhance clinical outcomes at 90 days when compared with EVT alone in patients with AIS. These observations need to be further confirmed by a large, multicenter, randomized clinical trial.

CLINICAL TRIALS REGISTRATION

NCT03620370.

CLASSIFICATION OF EVIDENCE

This pilot study provides Class I evidence that NBO combined with standard EVT decreases infarction volume in patients with acute anterior circulation stroke.

The application and perspective of hyperbaric oxygen therapy in acute ischemic stroke: From the bench to a starter?

Stroke has become a significant cause of death and disability globally. Along with the transition of the world's aging population, the incidence of acute ischemic stroke is increasing year by year. Even with effective treatment modalities, patients are not guaranteed to have a good prognosis. The treatment model combining intravenous thrombolysis/endovascular therapy and neuroprotection is gradually being recognized. After the clinical translation of pharmacological neuroprotective agents failed, non-pharmacological physical neuroprotective agents have rekindled hope. We performed a literature review using the National Center for Biotechnology Information (NCBI) PubMed database for studies that focused on the application of hyperbaric oxygen therapy in acute ischemic stroke. In this review, we present the history and mechanisms of hyperbaric oxygen therapy, focusing on the current status, outcomes, current challenges, perspective, safety, and complications of the application of hyperbaric oxygen in animal experiments and human clinical trials. Hyperbaric oxygen therapy, a non-pharmacological treatment, can improve the oxygenation level at the ischemic lesions in increased dissolved oxygen and oxygen diffusion radius to achieve salvage of neurological function, giving a new meaning to acute ischemic stroke.

Stroke thrombectomy perioperative anesthetic and hemodynamic management

There is an ongoing debate about the optimal anesthetic and hemodynamic management of acute stoke patients with large vessel occlusion undergoing endovascular mechanical thrombectomy. Several prospective and retrospective analyses, and randomized controlled trials, attempted to address the challenges of using different anesthetic modalities in acute stroke patients requiring mechanical thrombectomy. We review the advantages and disadvantages of monitored anesthesia care, local anesthesia, conscious sedation, and general anesthesia, along with the relevance of hemodynamic management and perioperative oxygenation status in these complex patients.

Novel Oxygen Carrier Slows Infarct Growth in Large Vessel Occlusion Dog Model Based on Magnetic Resonance Imaging Analysis

BACKGROUND

Tissue hypoxia plays a critical role in the events leading to cell death in ischemic stroke. Despite promising results in preclinical and small clinical pilot studies, inhaled oxygen supplementation has not translated to improved outcomes in large clinical trials. Moreover, clinical observations suggest that indiscriminate oxygen supplementation can adversely affect outcome, highlighting the need to develop novel approaches to selectively deliver oxygen to affected regions. This study tested the hypothesis that intravenous delivery of a novel oxygen carrier (Omniox-Ischemic Stroke [OMX-IS]), which selectively releases oxygen into severely ischemic tissue, could delay infarct progression in an established canine thromboembolic large vessel occlusion stroke model that replicates key dynamics of human infarct evolution.

METHODS

After endovascular placement of an autologous clot into the middle cerebral artery, animals received OMX-IS treatment or placebo 45 to 60 minutes after stroke onset. Perfusion-weighted magnetic resonance imaging was performed to define infarct progression dynamics to stratify animals into fast versus slow stroke evolvers. Serial diffusion-weighted magnetic resonance imaging was performed for up to 5 hours to quantify infarct evolution. Histology was performed postmortem to confirm final infarct size.

RESULTS

In fast evolvers, OMX-IS therapy substantially slowed infarct progression (by ≈1 hour, P<0.0001) and reduced the final normalized infarct volume as compared to controls (0.99 versus 0.88, control versus OMX-IS drug, P<0.0001). Among slow evolvers, OMX-IS treatment delayed infarct progression by approximately 45 minutes; however, this did not reach statistical significance (P=0.09). The final normalized infarct volume also did not show a significant difference (0.93 versus 0.95, OMX-IS drug versus control, P=0.34). Postmortem histologically determined infarct volumes showed excellent concordance with the magnetic resonance imaging defined ischemic lesion volume (bias: 1.33% [95% CI, -15% to 18%).

CONCLUSIONS

Intravenous delivery of a novel oxygen carrier is a promising approach to delay infarct progression after ischemic stroke, especially in treating patients with large vessel occlusion stroke who cannot undergo definitive reperfusion therapy within a timely fashion.

Hyperoxia-Induced ΔR1: MRI Biomarker of Histological Infarction in Acute Cerebral Stroke

OBJECTIVE

To evaluate whether hyperoxia-induced ΔR₁ (hyperO₂ΔR₁) can accurately identify histological infarction in an acute cerebral stroke model.

MATERIALS AND METHODS

In 18 rats, MRI parameters, including hyperO₂ΔR₁, apparent diffusion coefficient (ADC), cerebral blood flow and volume, and ¹⁸F-fluorodeoxyglucose uptake on PET were measured 2.5, 4.5, and 6.5 hours after a 60-minutes occlusion of the right middle cerebral artery. Histological examination of the brain was performed immediately following the imaging studies. MRI and PET images were co-registered with digitized histological images. The ipsilateral hemisphere was divided into histological infarct (histological cell death), non-infarct ischemic (no cell death but ADC decrease), and non-ischemic (no cell death or ADC decrease) areas for comparisons of imaging parameters. The levels of hyperO₂ΔR₁ and ADC were measured voxel-wise from the infarct core to the non-ischemic region. The correlation between areas of hyperO₂ΔR₁-derived infarction and histological cell death was evaluated.

RESULTS

HyperO₂ΔR₁ increased only in the infarct area (p ≤ 0.046) compared to the other areas. ADC decreased stepwise from non-ischemic to infarct areas (p = 0.002 at all time points). The other parameters did not show consistent differences among the three areas across the three time points. HyperO₂ΔR₁ sharply declined from the core to the border of the infarct areas, whereas there was no change within the non-infarct areas. A hyperO₂ΔR₁ value of 0.04 s^-1 was considered the criterion to identify histological infarction. ADC increased gradually from the infarct core to the periphery, without a pronounced difference at the border between the infarct and non-infarct areas. Areas of hyperO₂ΔR₁ higher than 0.04 s^-1 on MRI were strongly positively correlated with histological cell death (r = 0.862; p < 0.001).

CONCLUSION

HyperO₂ΔR₁ may be used as an accurate and early (2.5 hours after onset) indicator of histological infarction in acute stroke.

Dangers of hyperoxia

Oxygen (O2) toxicity remains a concern, particularly to the lung. This is mainly related to excessive production of reactive oxygen species (ROS). Supplemental O2, i.e. inspiratory O2 concentrations (FIO2) > 0.21 may cause hyperoxaemia (i.e. arterial (a) PO2 > 100 mmHg) and, subsequently, hyperoxia (increased tissue O2 concentration), thereby enhancing ROS formation. Here, we review the pathophysiology of O2 toxicity and the potential harms of supplemental O2 in various ICU conditions. The current evidence base suggests that PaO2 > 300 mmHg (40 kPa) should be avoided, but it remains uncertain whether there is an "optimal level" which may vary for given clinical conditions. Since even moderately supra-physiological PaO2 may be associated with deleterious side effects, it seems advisable at present to titrate O2 to maintain PaO2 within the normal range, avoiding both hypoxaemia and excess hyperoxaemia.

Infarct Progression in the Early and Late Phases of Acute Ischemic Stroke

PURPOSE OF REVIEW

To explore factors associated with infarct progression in the early and late phase of acute ischemic stroke in patients undergoing endovascular therapy.

RECENT FINDINGS

Following ischemic stroke, brain injury can progress at a variable rate, at the expense of "penumbral tissue," which is the ischemic tissue at risk of infarction. Despite dramatic advances in endovascular stroke therapies with early revascularization in more than 80% of cases, nearly half of patients do not achieve functional independence despite successful recanalization. This is largely attributed to the irreversible damage that is already extensive at the time of revascularization.

SUMMARY

The underlying pathophysiology and determinants of the core infarct progression are complex and multifactorial, depending on a balance between brain energy consumption and collateral perfusion supply. It is crucial to develop creative and individualized theranostics to predict infarct progression and to "freeze" the tissue at risk prior to recanalization.

Oxygen Saturation and Postoperative Mortality in Patients With Acute Ischemic Stroke Treated by Endovascular Thrombectomy

BACKGROUND

Monitored anesthesia care (MAC) and general anesthesia (GA) with endotracheal intubation are the 2 most used techniques for patients with acute ischemic stroke (AIS) undergoing endovascular thrombectomy. We aimed to test the hypothesis that increased arterial oxygen concentration during reperfusion period is a mechanism underlying the association between use of GA (versus MAC) and increased risk of in-hospital mortality.

METHODS

In this retrospective cohort study, data were collected at the Cleveland Clinic between 2013 and 2018. To assess the potential mediation effect of time-weighted average oxygen saturation (Spo2) in first postoperative 48 hours between the association between GA versus MAC and in-hospital mortality, we assessed the association between anesthesia type and post-operative Spo2 tertiles (exposure-mediator relationship) through a cumulative logistic regression model and assessed the association between Spo2 and in-hospital mortality (mediator-outcome relationship) using logistic regression models. Confounding factors were adjusted for using propensity score methods. Both significant exposure-mediator and significant mediator-outcome relationships are needed to suggest potential mediation effect.

RESULTS

Among 358 patients included in the study, 104 (29%) patients received GA and 254 (71%) received MAC, with respective hospital mortality rate of 19% and 5% (unadjusted P value <.001). GA patients were 1.6 (1.2, 2.1) (P < .001) times more likely to have a higher Spo2 tertile as compared to MAC patients. Patients with higher Spo2 tertile had 3.8 (2.1, 6.9) times higher odds of mortality than patients with middle Spo2 tertile, while patients in the lower Spo2 tertile did not have significant higher odds compared to the middle tertile odds ratio (OR) (1.8 [0.9, 3.4]; overall P < .001). The significant exposure-mediator and mediator-outcome relationships suggest that Spo2 may be a mediator of the relationship between anesthetic method and mortality. However, the estimated direct effect of GA versus MAC on mortality (ie, after adjusting for Spo2; OR [95% confidence interval {CI}] of 2.1 [0.9-4.9]) was close to the estimated association ignoring Spo2 (OR [95% CI] of 2.2 [1.0-5.1]), neither statistically significant, suggesting that Spo2 had at most a modest mediator role.

CONCLUSIONS

GA was associated with a higher Spo2 compared to MAC among those treated by endovascular thrombectomy for AIS. Spo2 values that were higher than the middle tertile were associated with higher odds of mortality. However, GA was not significantly associated with higher odds of death. Spo2 at most constituted a modest mediator role in explaining the relationship between GA versus MAC and mortality.

[German S3 Guideline - Oxygen Therapy in the Acute Care of Adult Patients]

BACKGROUND

 Oxygen (O₂) is a drug with specific biochemical and physiologic properties, a range of effective doses and may have side effects. In 2015, 14 % of over 55 000 hospital patients in the UK were using oxygen. 42 % of patients received this supplemental oxygen without a valid prescription. Healthcare professionals are frequently uncertain about the relevance of hypoxemia and have low awareness about the risks of hyperoxemia. Numerous randomized controlled trials about targets of oxygen therapy have been published in recent years. A national guideline is urgently needed.

METHODS

 A S3-guideline was developed and published within the Program for National Disease Management Guidelines (AWMF) with participation of 10 medical associations. Literature search was performed until Feb 1st 2021 to answer 10 key questions. The Oxford Centre for Evidence-Based Medicine (CEBM) System ("The Oxford 2011 Levels of Evidence") was used to classify types of studies in terms of validity. Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used and for assessing the quality of evidence and for grading guideline recommendation and a formal consensus-building process was performed.

RESULTS

 The guideline includes 34 evidence-based recommendations about indications, prescription, monitoring and discontinuation of oxygen therapy in acute care. The main indication for O₂ therapy is hypoxemia. In acute care both hypoxemia and hyperoxemia should be avoided. Hyperoxemia also seems to be associated with increased mortality, especially in patients with hypercapnia. The guideline provides recommended target oxygen saturation for acute medicine without differentiating between diagnoses. Target ranges for oxygen saturation are depending on ventilation status risk for hypercapnia. The guideline provides an overview of available oxygen delivery systems and includes recommendations for their selection based on patient safety and comfort.

CONCLUSION

 This is the first national guideline on the use of oxygen in acute care. It addresses healthcare professionals using oxygen in acute out-of-hospital and in-hospital settings. The guideline will be valid for 3 years until June 30, 2024.

Neuroprotective Effects of Normobaric Hyperoxia and Transplantation of Encapsulated Choroid Plexus Epithelial Cells on The Focal Brain Ischemia

Objective

Choroid plexus epithelial cells (CPECs) have the epithelial characteristic, produce cerebrospinal fluid, contribute to the detoxification process in the central nervous system (CNS), and are responsible for the synthesis and release of many nerve growth factors. On the other hand, studies suggest that normobaric hyperoxia (HO) by induction of ischemic tolerance (IT) can protect against brain damage and neurological diseases. We examined the effect of combination therapy of encapsulated CPECs and HO to protect against ischemic brain injury.

Materials and Methods

In this experimental study, six groups of adult male Wistar rats were randomly organized: sham, room air (RA)+middle cerebral artery occlusion (MCAO), HO+MCAO, RA+MCAO+encapsulated CPECs, HO+MCAO+encapsulated CPECs, RA+MCAO+empty capsules. RA/HO were pretreatment. The CPECs were isolated from the brain of neonatal Wistar rats, cultured, and encapsulated. Then microencapsulated CPECs were transplanted in the neck of the animal immediately after the onset of reperfusion in adult rats that had been exposed to 60 minutes MCAO. After 23 hours of reperfusion, the neurologic deficit score (NDS) was assessed. Next, rats were killed, and brains were isolated for measuring brain infarction volume, blood-brain barrier (BBB) permeability, edema, the activity of superoxide dismutase (SOD), and catalase (CAT) and also, the level of malondialdehyde (MDA).

Results

Our results showed that NDS decreased equally in HO+MCAO, RA+MCAO+encapsulated CPECs, and HO+MCAO+encapsulated CPECs groups. Brain infarction volume decreased up 79%, BBB stability increased, edema decreased, SOD and CAT activities increased, and MDA decreased in the combination group of HO and transplantation of encapsulated CPECs in the ischemic brain as compared with when HO or transplantation of encapsulated CPECs was applied alone.

Conclusion

The combination of HO and transplantation of encapsulated CPECs for stroke in rats was more effective than the other treatments, and it can be taken into account as a promising treatment for ischemic stroke.

Normobaric oxygen may correct chronic cerebral ischemia-mediated EEG anomalies

AIMS

To explore the safety and efficacy of normobaric oxygen (NBO) on correcting chronic cerebral ischemia (CCI) and related EEG anomalies.

METHODS

This prospective randomized trial (NCT03745092) enrolled 50 cases of CCI patients, which were divided into NBO (8 L/min of oxygen supplement) group and control group (room air) randomly, and also enrolled 21 healthy volunteers. Two times of 30-min EEG recordings with the interval of 45min of NBO or room air were analyzed quantitatively.

RESULTS

The CCI-mediated EEG presented with two patterns of electrical activities: high-power oscillations (high-power EEG, n = 26) and paroxysmal slow activities under the normal-power background (normal-power EEG, n = 24). The fronto-central absolute power (AP) of the beta, alpha, theta, and delta in the high-power EEG was higher than that in healthy EEG (p < 0.05). The fronto-central theta/alpha, delta/alpha and (delta + theta)/(alpha + beta) ratios in the normal-power EEG were higher than those in healthy EEG (p < 0.05). The high-power EEG in NBO group had higher fronto-central AP reduction rates than those in control group (p < 0.05). NBO remarkably reduced the fronto-central theta/alpha, delta/alpha, and (delta + theta)/(alpha + beta) ratios in the normal-power EEG (p < 0.05).

CONCLUSIONS

NBO rapidly ameliorates CCI-mediated EEG anomalies, including attenuation of the abnormal high-power oscillations and the paroxysmal slow activities associated with CCI.

Oxygen desaturation and adverse outcomes in acute stroke: Secondary analysis of the HeadPoST study

OBJECTIVE

Uncertainty exists over the prognostic significance of low arterial oxygen saturation (SaO₂) in acute stroke. We aimed to determine the strength of association of SaO₂ and adverse outcomes among participants of the international Head Positioning in acute Stroke Trial (HeadPoST).

METHODS

Post-hoc analyzes of HeadPoST, a pragmatic cluster-crossover randomized trial of lying flat versus sitting up head positioning in 11,093 patients (age ≥18 years) with acute stroke at 114 hospitals in 9 countries during 2015-2016. Associations of the lowest recorded SaO₂ level, as a continuous measure and as a cut-point for desaturation (SaO₂ <93%), in the first 24 h and clinical outcomes of death or dependency (modified Rankin scale [mRS] scores 3-6) and any serious adverse event (SAE) at 90 days, were assessed in generalized linear mixed models adjusted for baseline and in-hospital management confounders.

RESULTS

There was an inverse J-shaped association between SaO₂ and death or dependency, with a nadir for optimal outcome at 96-97%. Patients with SaO₂ desaturation were older, and had greater neurological impairment, premorbid disability and cardiorespiratory disease. Desaturation was not clearly associated with death or dependency (adjusted odds ratio [aOR] 1.19, 95% confidence interval [CI] 0.95-1.48) but was with SAEs (aOR 1.34, 95% CI 1.07-1.68), without heterogeneity by head position, cardiac-respiratory comorbidity, or other pre-specified subgroups.

CONCLUSIONS

Any change in SaO₂ outside of 96-97% is associated with poorer outcome after acute stroke.

CLINICAL TRIAL REGISTRATION

HeadPoST is registered at ClinicalTrials.gov (NCT02162017).

Efficacy and safety of normobaric hyperoxia combined with intravenous thrombolysis on acute ischemic stroke patients

Intravenous thrombolysis elevates the prognostic level of acute ischemic stroke (AIS) patients. Normobaric hyperoxia (NBO) delays the progression of the infarct core and promotes neurological recovery. However, it is uncertain whether NBO can further raise the prognostic level of AIS patients based on intravenous thrombolysis. To explore the efficacy and safety of NBO combined with intravenous thrombolysis on AIS patients. This observational study included anterior circulation stroke patients who received intravenous thrombolysis within 4.5 h after stroke onset. These patients were divided into two groups based on whether or not they received NBO therapy. The baseline data and the prognosis of the two groups were compared. The primary outcome was the proportion of functional independence (modified Rankin Scale 0-2) at 90 days post discharge. A total of 227 patients were included in this study. 125 patients received NBO therapy combined with intravenous thrombolysis, while 102 patients received intravenous thrombolysis only. Overall, the rate of recanalization was 83.3%. Consequently, 101 patients (80.8%) who received NBO combined with intravenous thrombolysis and 63 patients (61.8%) in the control group achieved functional independence (P = 0.002). Multivariable logistic regression analysis showed that NBO combined with intravenous thrombolysis over intravenous thrombolysis alone was associated with 90-day functional independence (OR: 2.318; 95% CI: 1.226-4.381; P = 0.01). This study verified the efficacy and safety of NBO combined with intravenous thrombolysis in AIS patients. Prospective study is needed to further substantiate these findings.

Adjuvant High-Flow Normobaric Oxygen After Mechanical Thrombectomy for Anterior Circulation Stroke: a Randomized Clinical Trial

Adjuvant neuroprotective therapies for acute ischemic stroke (AIS) have demonstrated benefit in animal studies, albeit without human translation. We investigated the safety and efficacy of high-flow normobaric oxygen (NBO) after endovascular recanalization in anterior circulation stroke. This is a prospective randomized controlled study. Eligible patients were randomized to receive high-flow NBO by a Venturi mask (FiO2 50%, flow 15 L/min) or routine low-flow oxygen supplementation by nasal cannula (flow 3 L/min) after vessel recanalization for 6 h. Patient demographics, procedural metrics, complications, functional outcomes, symptomatic intracranial hemorrhage (sICH), and infarct volume were assessed. A total of 91 patients were treated with high-flow NBO. NBO treatment revealed a common odds ratio of 2.2 (95% CI, 1.26 to 3.87) favoring the distribution of global disability scores on the mRS at 90 days. The mortality at 90 days was significantly lower in the NBO group than in the control group, with an absolute difference of 13.86% (rate ratio, 0.35; 95% CI, 0.13-0.93). A significant reduction of infarct volume as determined by MRI was noted in the NBO group. The median infarct volume was 9.4 ml versus 20.5 ml in the control group (beta coefficient, - 20.24; 95% CI, - 35.93 to - 4.55). No significant differences were seen in the rate of sICH, pneumonia, urinary infection, and seizures between the 2 groups. This study suggests that high-flow NBO therapy after endovascular recanalization is safe and effective in improving functional outcomes, decreasing mortality, and reducing infarct volumes in anterior circulation stroke patients within 6 h from stroke onset.

European Resuscitation Council Guidelines 2021: First aid

The European Resuscitation Council has produced these first aid guidelines, which are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. The topics include the first aid management of emergency medicine and trauma. For medical emergencies the following content is covered: recovery position, optimal positioning for shock, bronchodilator administration for asthma, recognition of stroke, early aspirin for chest pain, second dose of adrenaline for anaphylaxis, management of hypoglycaemia, oral rehydration solutions for treating exertion-related dehydration, management of heat stroke by cooling, supplemental oxygen in acute stroke, and presyncope. For trauma related emergencies the following topics are covered: control of life-threatening bleeding, management of open chest wounds, cervical spine motion restriction and stabilisation, recognition of concussion, cooling of thermal burns, dental avulsion, compression wrap for closed extremity joint injuries, straightening an angulated fracture, and eye injury from chemical exposure.

Conservative versus liberal oxygen therapy for acutely ill medical patients: A systematic review and meta-analysis

BACKGROUND

The role of conservative versus liberal oxygen therapy for acutely ill patients remains controversial.

OBJECTIVE

To systematically review the available evidence regarding the efficacy and safety of conservative oxygen therapy compared with liberal oxygen therapy for acutely ill patients.

METHODS

A systematic search of Medline, Embase, and the Cochrane Central Register was conducted from their inception until April 5, 2020. Randomized clinical trials evaluating a high-target (liberal) or a low-target (conservative) oxygenation strategy in adults with an acutely ill condition were eligible for inclusion. A meta-analysis using random-effects models was conducted to calculate the risk ratio with corresponding 95% confidence intervals. Heterogeneity and publication bias were evaluated.

RESULTS

The analyses included 33 randomized clinical trials with a total of 17,780 participants. Compared with conservative oxygen therapy, liberal oxygen therapy was not associated with increased mortality at 30 days (risk ratio 1.09, 95% confidence intervals 0.98-1.22; I²=0%), at 90 days (risk ratio 1.00, 95% confidence intervals 0.88-1.13, I²=37%), or at the longest follow-up (risk ratio 1.04, 95% confidence intervals 0.96-1.12, I²=0%). Good functional outcome was similar between groups. Findings were robust to trial sequential, subgroup, and sensitivity analyses.

CONCLUSIONS

Compared with liberal oxygen therapy, conservative oxygen therapy was not associated with decreased mortality. Tweetable abstract: Compared with liberal oxygen therapy, conservative oxygen therapy was not associated with decreased mortality.

Classification and effectiveness of different oxygenation goals in mechanically ventilated critically ill patients: network meta-analysis of randomised controlled trials

BACKGROUND

The optimal oxygenation in mechanically ventilated critically ill patients remains unclear.

METHODS

Randomised controlled trials investigating different oxygenation goal-directed mechanical ventilation in critically ill adult patients were eligible. The trinary classification classified oxygenation goals into conservative (PaO₂=55-90 mmHg), moderate (PaO₂=90-150 mmHg), and liberal (PaO₂>150 mmHg). The quadruple classification further divided the conservative goal from the trinary classification into far-conservative (PaO₂=55-70 mmHg) and conservative (PaO₂=70-90 mmHg) goals. The primary outcome was 30-day mortality. The secondary outcomes included intensive care unit, hospital, and 90-day mortalities. The effectiveness was estimated by the relative risk (RR) and 95% credible interval (CrI) using network meta-analysis and visualised using SUCRA scores and survival curves.

RESULTS

We identified eight eligible studies involving 2532 patients. There were no differences between conservative and moderate goals (RR, 1.08; 95% CrI, 0.85 to 1.36; moderate quality), between moderate and liberal goals (RR, 0.83; 95% CrI, 0.61 to 1.10, low quality), and between conservative and liberal goals (RR, 0.89; 95% CrI, 0.61 to 1.30, low quality) based on the trinary classification. No differences in secondary outcomes among the different goals. The results were consistent between the trinary and quadruple classifications. The SUCRA scores and survival curves suggested that the moderate goal in the trinary and quadruple classifications and the conservative goal in the quadruple classification may be superior to the liberal and far-conservative goals.

CONCLUSIONS

Different oxygenation goals do not lead to different mortalities in mechanically ventilated critically ill patients. The potential superiority of maintaining PaO₂ in the range of 70-150 mmHg remains to be validated.

Normobaric oxygen therapy attenuates hyperglycolysis in ischemic stroke

Normobaric oxygen therapy has gained attention as a simple and convenient means of achieving neuroprotection against the pathogenic cascade initiated by acute ischemic stroke. The mechanisms underlying the neuroprotective efficacy of normobaric oxygen therapy, however, have not been fully elucidated. It is hypothesized that cerebral hyperglycolysis is involved in the neuroprotection of normobaric oxygen therapy against ischemic stroke. In this study, Sprague-Dawley rats were subjected to either 2-hour middle cerebral artery occlusion followed by 3- or 24-hour reperfusion or to a permanent middle cerebral artery occlusion event. At 2 hours after the onset of ischemia, all rats received either 95% oxygen normobaric oxygen therapy for 3 hours or room air. Compared with room air, normobaric oxygen therapy significantly reduced the infarct volume, neurological deficits, and reactive oxygen species and increased the production of adenosine triphosphate in ischemic rats. These changes were associated with reduced transcriptional and translational levels of the hyperglycolytic enzymes glucose transporter 1 and 3, phosphofructokinase 1, and lactate dehydrogenase. In addition, normobaric oxygen therapy significantly reduced adenosine monophosphate-activated protein kinase mRNA expression and phosphorylated adenosine monophosphate-activated protein kinase protein expression. These findings suggest that normobaric oxygen therapy can reduce hyperglycolysis through modulating the adenosine monophosphate-activated protein kinase signaling pathway and alleviating oxidative injury, thereby exhibiting neuroprotective effects in ischemic stroke. This study was approved by the Institutional Animal Investigation Committee of Capital Medical University (approval No. AEEI-2018-033) on August 13, 2018.

2020 International Consensus on First Aid Science With Treatment Recommendations

This is the summary publication of the International Liaison Committee on Resuscitation's 2020 International Consensus on First Aid Science With Treatment Recommendations. It addresses the most recent published evidence reviewed by the First Aid Task Force science experts. This summary addresses the topics of first aid methods of glucose administration for hypoglycemia; techniques for cooling of exertional hyperthermia and heatstroke; recognition of acute stroke; the use of supplementary oxygen in acute stroke; early or first aid use of aspirin for chest pain; control of life- threatening bleeding through the use of tourniquets, haemostatic dressings, direct pressure, or pressure devices; the use of a compression wrap for closed extremity joint injuries; and temporary storage of an avulsed tooth. Additional summaries of scoping reviews are presented for the use of a recovery position, recognition of a concussion, and 6 other first aid topics. The First Aid Task Force has assessed, discussed, and debated the certainty of evidence on the basis of Grading of Recommendations, Assessment, Development, and Evaluation criteria and present their consensus treatment recommendations with evidence-to-decision highlights and identified priority knowledge gaps for future research. The 2020 International Consensus on Cardiopulmonary Resuscitation (CPR) and Emergency Cardiovascular Care (ECC) Science With Treatment Recommendations (CoSTR) is the fourth in a series of annual summary publications from the International Liaison Committee on Resuscitation (ILCOR). This 2020 CoSTR for first aid includes new topics addressed by systematic reviews performed within the past 12 months. It also includes updates of the first aid treatment recommendations published from 2010 through 2019 that are based on additional evidence evaluations and updates. As a result, this 2020 CoSTR for first aid represents the most comprehensive update since 2010.

2020 International Consensus on First Aid Science With Treatment Recommendations

This is the summary publication of the International Liaison Committee on Resuscitation's 2020 International Consensus on First Aid Science With Treatment Recommendations. It addresses the most recent published evidence reviewed by the First Aid Task Force science experts. This summary addresses the topics of first aid methods of glucose administration for hypoglycemia; techniques for cooling of exertional hyperthermia and heatstroke; recognition of acute stroke; the use of supplementary oxygen in acute stroke; early or first aid use of aspirin for chest pain; control of life-threatening bleeding through the use of tourniquets, hemostatic dressings, direct pressure, or pressure devices; the use of a compression wrap for closed extremity joint injuries; and temporary storage of an avulsed tooth. Additional summaries of scoping reviews are presented for the use of a recovery position, recognition of a concussion, and 6 other first aid topics. The First Aid Task Force has assessed, discussed, and debated the certainty of evidence on the basis of Grading of Recommendations, Assessment, Development, and Evaluation criteria and present their consensus treatment recommendations with evidence-to-decision highlights and identified priority knowledge gaps for future research.

An Extra Breath of Fresh Air: Hyperbaric Oxygenation as a Stroke Therapeutic

Stroke serves as a life-threatening disease and continues to face many challenges in the development of safe and effective therapeutic options. The use of hyperbaric oxygen therapy (HBOT) demonstrates pre-clinical effectiveness for the treatment of acute ischemic stroke and reports reductions in oxidative stress, inflammation, and neural apoptosis. These pathophysiological benefits contribute to improved functional recovery. Current pre-clinical and clinical studies are testing the applications of HBOT for stroke neuroprotection, including its use as a preconditioning regimen. Mild oxidative stress may be able to prime the brain to tolerate full extensive oxidative stress that occurs during a stroke, and HBOT preconditioning has displayed efficacy in establishing such ischemic tolerance. In this review, evidence on the use of HBOT following an ischemic stroke is examined, and the potential for HBOT preconditioning as a neuroprotective strategy. Additionally, HBOT as a stem cell preconditioning is also discussed as a promising strategy, thus maximizing the use of HBOT for ischemic stroke.

The modern concept of neuroprotective therapy in the acute period of ischemic stroke

In recent years, significant successes have been achieved in the treatment of acute ischemic stroke. Given the trend towards an increase in the proportion of patients undergoing intravenous thrombolysis and / or mechanical thrombectomy, the question justifies: is there place for neuroprotective therapy (NT) in the era of active introduction of reperfusion treatment? The review discusses the main mechanisms of brain damage in ischemia / reperfusion and the leading neuroprotective strategies studied in clinical trials. Neuroprotective approaches to suppress excitotoxicity, oxidative and nitrosative stress are presented. The clinical efficacy of magnesium sulfate, uric acid, and edaravone is discussed. Non-pharmacological methods of neuroprotection have been characterized, including remote ischemic conditioning, therapeutic hypothermia and neurostimulation. NT in a situation of impossibility of cerebral reperfusion is discussed. The results of randomized clinical trials and meta-analyzes on citicoline (ceraxon) are analyzed. A clinical case is presented illustrating the management of a patient for whom reperfusion therapy was not feasible due to the course of the disease. In the era of the active development of reperfusion methods for the treatment of ischemic stroke, the goal-setting of NT has changed: it is intended to expand the possibilities of application and increase the effectiveness of intravenous thrombolysis and/or mechanical thrombectome, as well as neutralize their negative reperfusion effects. The main targets for NT remain excitotoxicity, oxidative and nitrosative stress. On the other hand, the real clinical situation associated with the low frequency of reperfusion technology in our country necessitates the use of neuroprotectors effective in this category of patients. In this regard, the administration of ceraxon increases the chances of achieving functional independence. The most effective use of the drug from the first day of the disease at a dose of 2000 mg per day intravenously for at least 4-6 weeks with further long-term oral administration at a dose of 1000 mg per day.

Hyperbaric oxygen therapy in acute stroke: is it time for Justitia to open her eyes?

Hypoxia is a critical component of neuronal death in patients with stroke. Therefore increasing oxygenation of brain tissue seems to be a logical therapy against cerebral ischemia. Oxygen therapy exists in two modalities: normobaric hyperoxia therapy and hyperbaric oxygen therapy (HBO). HBO is a therapeutic procedure in which pure (100%) oxygen is administered at greater than atmospheric pressure in HBO therapy chambers. In this review article, we aimed to summarize the current knowledge regarding the therapeutic use of HBO in acute stroke patients. Literature review and electronic search were performed using PubMed, Medscape, and UpToDate with the keywords stroke, acute stroke, hyperbaric oxygen therapy, and hyperoxia. According to the reviewed literature, the use of HBO as routine stroke therapy cannot be justified in acute stage of stroke. More randomized, controlled studies are needed regarding safety and especially effectives of HBO in stroke patients. Also, standardized definitionof HBO should be proposed and used in all future studies.

Mechanical ventilation in patients with acute ischaemic stroke: from pathophysiology to clinical practice

Most patients with ischaemic stroke are managed on the ward or in specialty stroke units, but a significant number requires higher-acuity care and, consequently, admission to the intensive care unit. Mechanical ventilation is frequently performed in these patients due to swallowing dysfunction and airway or respiratory system compromise. Experimental studies have focused on stroke-induced immunosuppression and brain-lung crosstalk, leading to increased pulmonary damage and inflammation, as well as reduced alveolar macrophage phagocytic capability, which may increase the risk of infection. Pulmonary complications, such as respiratory failure, pneumonia, pleural effusions, acute respiratory distress syndrome, lung oedema, and pulmonary embolism from venous thromboembolism, are common and found to be among the major causes of death in this group of patients. Furthermore, over the past two decades, tracheostomy use has increased among stroke patients, who can have unique indications for this procedure—depending on the location and type of stroke—when compared to the general population. However, the optimal mechanical ventilator strategy remains unclear in this population. Although a high tidal volume (V_T) strategy has been used for many years, the latest evidence suggests that a protective ventilatory strategy (V_T = 6–8 mL/kg predicted body weight, positive end-expiratory pressure and rescue recruitment manoeuvres) may also have a role in brain-damaged patients, including those with stroke. The aim of this narrative review is to explore the pathophysiology of brain-lung interactions after acute ischaemic stroke and the management of mechanical ventilation in these patients.

Higher versus lower fraction of inspired oxygen or targets of arterial oxygenation for adults admitted to the intensive care unit

BACKGROUND

The mainstay treatment for hypoxaemia is oxygen therapy, which is given to the vast majority of adults admitted to the intensive care unit (ICU). The practice of oxygen administration has been liberal, which may result in hyperoxaemia. Some studies have indicated an association between hyperoxaemia and mortality, whilst other studies have not. The ideal target for supplemental oxygen for adults admitted to the ICU is uncertain. Despite a lack of robust evidence of effectiveness, oxygen administration is widely recommended in international clinical practice guidelines. The potential benefit of supplemental oxygen must be weighed against the potentially harmful effects of hyperoxaemia.

OBJECTIVES

To assess the benefits and harms of higher versus lower fraction of inspired oxygen or targets of arterial oxygenation for adults admitted to the ICU.

SEARCH METHODS

We identified trials through electronic searches of CENTRAL, MEDLINE, Embase, Science Citation Index Expanded, BIOSIS Previews, CINAHL, and LILACS. We searched for ongoing or unpublished trials in clinical trials registers. We also scanned the reference lists of included studies. We ran the searches in December 2018.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that compared higher versus lower fraction of inspired oxygen or targets of arterial oxygenation for adults admitted to the ICU. We included trials irrespective of publication type, publication status, and language. We included trials with a difference between the intervention and control groups of a minimum 1 kPa in partial pressure of arterial oxygen (PaO2), minimum 10% in fraction of inspired oxygen (FiO2), or minimum 2% in arterial oxygen saturation of haemoglobin/non-invasive peripheral oxygen saturation (SaO2/SpO2). We excluded trials randomizing participants to hypoxaemia (FiO2 below 0.21, SaO2/SpO2 below 80%, and PaO2 below 6 kPa) and to hyperbaric oxygen.

DATA COLLECTION AND ANALYSIS

Three review authors independently, and in pairs, screened the references retrieved in the literature searches and extracted data. Our primary outcomes were all-cause mortality, the proportion of participants with one or more serious adverse events, and quality of life. None of the trials reported the proportion of participants with one or more serious adverse events according to the International Conference on Harmonisation Good Clinical Practice (ICH-GCP) criteria. Nonetheless, most trials reported several serious adverse events. We therefore included an analysis of the effect of higher versus lower fraction of inspired oxygen, or targets using the highest reported proportion of participants with a serious adverse event in each trial. Our secondary outcomes were lung injury, acute myocardial infarction, stroke, and sepsis. None of the trials reported on lung injury as a composite outcome, however some trials reported on acute respiratory distress syndrome (ARDS) and pneumonia. We included an analysis of the effect of higher versus lower fraction of inspired oxygen or targets using the highest reported proportion of participants with ARDS or pneumonia in each trial. To assess the risk of systematic errors, we evaluated the risk of bias of the included trials. We used GRADE to assess the overall certainty of the evidence.

MAIN RESULTS

We included 10 RCTs (1458 participants), seven of which reported relevant outcomes for this review (1285 participants). All included trials had an overall high risk of bias, whilst two trials had a low risk of bias for all domains except blinding of participants and personnel. Meta-analysis indicated harm from higher fraction of inspired oxygen or targets as compared with lower fraction or targets of arterial oxygenation regarding mortality at the time point closest to three months (risk ratio (RR) 1.18, 95% confidence interval (CI) 1.01 to 1.37; I2 = 0%; 4 trials; 1135 participants; very low-certainty evidence). Meta-analysis indicated harm from higher fraction of inspired oxygen or targets as compared with lower fraction or targets of arterial oxygenation regarding serious adverse events at the time point closest to three months (estimated highest proportion of specific serious adverse events in each trial RR 1.13, 95% CI 1.04 to 1.23; I2 = 0%; 1234 participants; 6 trials; very low-certainty evidence). These findings should be interpreted with caution given that they are based on very low-certainty evidence. None of the included trials reported any data on quality of life at any time point. Meta-analysis indicated no evidence of a difference between higher fraction of inspired oxygen or targets as compared with lower fraction or targets of arterial oxygenation on lung injury at the time point closest to three months (estimated highest reported proportion of lung injury RR 1.03, 95% CI 0.78 to 1.36; I2 = 0%; 1167 participants; 5 trials; very low-certainty evidence). None of the included trials reported any data on acute myocardial infarction or stroke, and only one trial reported data on the effects on sepsis.

AUTHORS' CONCLUSIONS

We are very uncertain about the effects of higher versus lower fraction of inspired oxygen or targets of arterial oxygenation for adults admitted to the ICU on all-cause mortality, serious adverse events, and lung injuries at the time point closest to three months due to very low-certainty evidence. Our results indicate that oxygen supplementation with higher versus lower fractions or oxygenation targets may increase mortality. None of the trials reported the proportion of participants with one or more serious adverse events according to the ICH-GCP criteria, however we found that the trials reported an increase in the number of serious adverse events with higher fractions or oxygenation targets. The effects on quality of life, acute myocardial infarction, stroke, and sepsis are unknown due to insufficient data.

Prehospital supplemental oxygen for acute stroke - A retrospective analysis

OBJECTIVE

Brief early administration of supplemental oxygen (sO₂) to create hyperoxia may increase oxygenation to penumbral tissue and improve stroke outcomes. Hyperoxia may also result in respiratory compromise and vasoconstriction leading to worse outcomes. This study examines the effects of prehospital sO₂ in stroke.

METHODS

This is a retrospective analysis of adult acute stroke patients (aged ≥18 years) presenting via EMS to an academic Comprehensive Stroke Center between January 1, 2013 and December 31, 2017. Demographic and clinical characteristics obtained from Get with the Guidelines-Stroke registry and subjects' medical records were compared across three groups based on prehospital oxygen saturation and sO₂ administration. Chi-square, ANOVA, and multivariate logistic regression were used to determine if sO₂ status was associated with neurological outcomes or respiratory complications.

RESULTS

1352 eligible patients were identified. 62.7% (n = 848) did not receive sO₂ ("controls"), 10.7% (n = 144) received sO₂ due to hypoxia ("hypoxia"), and 26.6% (n = 360) received sO₂ despite normoxia ("hyperoxia"). The groups represented a continuum from more severe deficits (hypoxia) to less severe deficits (controls): mean prehospital GCS (hypoxia -12, hyperoxia - 2, controls - 14 p ≤ 0.001), mean initial NIHSS (hypoxia - 15, hyperoxia - 13, controls - 8 p < 0.001). After controlling for potential confounders, all groups had similar rates of respiratory complications and favorable neurological outcomes.

CONCLUSIONS

Hyperoxic subjects had no significant increase in respiratory complications, nor did they differ in neurologic outcomes at discharge when controlling for confounders. While limited by the retrospective nature, this suggests brief, early sO₂ for stroke may be safe to evaluate prospectively.

Guidelines for the Early Management of Patients With Acute Ischemic Stroke: 2019 Update to the 2018 Guidelines for the Early Management of Acute Ischemic Stroke: A Guideline for Healthcare Professionals From the American Heart Association/American Stroke Association

Background and Purpose- The purpose of these guidelines is to provide an up-to-date comprehensive set of recommendations in a single document for clinicians caring for adult patients with acute arterial ischemic stroke. The intended audiences are prehospital care providers, physicians, allied health professionals, and hospital administrators. These guidelines supersede the 2013 Acute Ischemic Stroke (AIS) Guidelines and are an update of the 2018 AIS Guidelines. Methods- Members of the writing group were appointed by the American Heart Association (AHA) Stroke Council's Scientific Statements Oversight Committee, representing various areas of medical expertise. Members were not allowed to participate in discussions or to vote on topics relevant to their relations with industry. An update of the 2013 AIS Guidelines was originally published in January 2018. This guideline was approved by the AHA Science Advisory and Coordinating Committee and the AHA Executive Committee. In April 2018, a revision to these guidelines, deleting some recommendations, was published online by the AHA. The writing group was asked review the original document and revise if appropriate. In June 2018, the writing group submitted a document with minor changes and with inclusion of important newly published randomized controlled trials with >100 participants and clinical outcomes at least 90 days after AIS. The document was sent to 14 peer reviewers. The writing group evaluated the peer reviewers' comments and revised when appropriate. The current final document was approved by all members of the writing group except when relationships with industry precluded members from voting and by the governing bodies of the AHA. These guidelines use the American College of Cardiology/AHA 2015 Class of Recommendations and Level of Evidence and the new AHA guidelines format. Results- These guidelines detail prehospital care, urgent and emergency evaluation and treatment with intravenous and intra-arterial therapies, and in-hospital management, including secondary prevention measures that are appropriately instituted within the first 2 weeks. The guidelines support the overarching concept of stroke systems of care in both the prehospital and hospital settings. Conclusions- These guidelines provide general recommendations based on the currently available evidence to guide clinicians caring for adult patients with acute arterial ischemic stroke. In many instances, however, only limited data exist demonstrating the urgent need for continued research on treatment of acute ischemic stroke.

Protecting the ischaemic penumbra as an adjunct to thrombectomy for acute stroke

After ischaemic stroke, brain damage can be curtailed by rescuing the 'ischaemic penumbra' - that is, the severely hypoperfused, at-risk but not yet infarcted tissue. Current evidence-based treatments involve restoration of blood flow so as to salvage the penumbra before it evolves into irreversibly damaged tissue, termed the 'core'. Intravenous thrombolysis (IVT) can salvage the penumbra if given within 4.5 h after stroke onset; however, the early recanalization rate is only ~30%. Direct removal of the occluding clot by mechanical thrombectomy considerably improves outcomes over IVT alone, but despite early recanalization in > 80% of cases, ~50% of patients who receive this treatment do not enjoy functional independence, usually because the core is already too large at the time of recanalization. Novel therapies aiming to 'freeze' the penumbra - that is, prevent core growth until recanalization is complete - hold potential as adjuncts to mechanical thrombectomy. This Review focuses on nonpharmacological approaches that aim to restore the physiological balance between oxygen delivery to and oxygen demand of the penumbra. Particular emphasis is placed on normobaric oxygen therapy, hypothermia and sensory stimulation. Preclinical evidence and early pilot clinical trials are critically reviewed, and future directions, including clinical translation and trial design issues, are discussed.