Carbon Monoxide Poisoning: Pathogenesis, Management, and Future Directions of Therapy

Recent advances in carbon monoxide-releasing nanomaterials

As an endogenous signaling molecule, carbon monoxide (CO) has emerged as an increasingly promising option regarding as gas therapy due to its positive pharmacological effects in various diseases. Owing to the gaseous nature and potential toxicity, it is particularly important to modulate the CO release dosages and targeted locations to elucidate the biological mechanisms of CO and facilitate its clinical applications. Based on these, diverse CO-releasing molecules (CORMs) have been developed for controlled release of CO in biological systems. However, practical applications of these CORMs are limited by several disadvantages including low stability, poor solubility, weak releasing controllability, random diffusion, and potential toxicity. In light of rapid developments and diverse advantages of nanomedicine, abundant nanomaterials releasing CO in controlled ways have been developed for therapeutic purposes across various diseases. Due to their nanoscale sizes, diversified compositions and modified surfaces, vast CO-releasing nanomaterials (CORNMs) have been constructed and exhibited controlled CO release in specific locations under various stimuli with better pharmacokinetics and pharmacodynamics. In this review, we present the recent progress in CORNMs according to their compositions. Following a concise introduction to CO therapy, CORMs and CORNMs, the representative research progress of CORNMs constructed from organic nanostructures, hybrid nanomaterials, inorganic nanomaterials, and nanocomposites is elaborated. The basic properties of these CORNMs, such as active components, CO releasing mechanisms, detection methods, and therapeutic applications, are discussed in detail and listed in a table. Finally, we explore and discuss the prospects and challenges associated with utilizing nanomaterials for biological CO release.

Carbon Monoxide as a Potential Therapeutic Agent: A Molecular Analysis of Its Safety Profiles

Carbon monoxide (CO) is endogenously produced in mammals, with blood concentrations in the high micromolar range in the hemoglobin-bound form. Further, CO has shown therapeutic effects in various animal models. Despite its reputation as a poisonous gas at high concentrations, we show that CO should have a wide enough safety margin for therapeutic applications. The analysis considers a large number of factors including levels of endogenous CO, its safety margin in comparison to commonly encountered biomolecules or drugs, anticipated enhanced safety profiles when delivered via a noninhalation mode, and the large amount of safety data from human clinical trials. It should be emphasized that having a wide enough safety margin for therapeutic use does not mean that it is benign or safe to the general public, even at low doses. We defer the latter to public health experts. Importantly, this Perspective is written for drug discovery professionals and not the general public.

Postmortem concentrations for total blood carbon monoxide (TBCO) as a novel biomarker for carbon monoxide (CO) poisonings

Total blood carbon monoxide (TBCO) showed promising results in improving accuracy of CO determinations in blood and presenting better stability to different storage conditions. Therefore, it was proposed as an alternative biomarker to carboxyhemoglobin (COHb) for CO poisoning diagnosis. However, given that current interpretation reference values exist for COHb only, it is difficult to implement TBCO analysis in routine. Therefore, we aimed at determining TBCO reference values for postmortem CO poisoning cases. A previously validated method for TBCO analysis via gas chromatography-mass spectrometry was applied to cardiac, peripheral, cranial and spleen blood samples collected from 92 autopsies. Autopsy cases included 21 non-CO-related and 71 CO-related cases with varying postmortem intervals (PMIs). Statistical analyses were performed using statistical software R Studio. When comparing lower to higher PMIs for non-CO-related cases, no significant differences were found, which suggests that CO formation or degradation at low PMIs does not occur. Spleen blood showed potential as an alternative matrix to CO determinations in cases with sample availability issues but needs to be evaluated for CO-positive cases. Results for cardiac blood in CO-related autopsies showed a positive correlation between COHb and TBCO values (R = 0.78). This value is lower than what is found in the literature, suggesting that even though COHb and TBCO are correlated, a potential underestimation of the true CO exposure might occur if only COHb values are taken into consideration. Samples were divided into CO exposure groups based on COHb concentrations, and with the data obtained, classification into the following TBCO concentration groups is proposed: no significant CO exposure case <6 µmol/mL, medium CO exposure case 6-20 µmol/mL and high CO exposure case >20 µmol/mL. Even if a higher number of samples in each group would enable to increase the confidence, these results are very promising and highlight the importance of TBCO measurement.

Carboxyhemoglobin half-life toxicokinetic profiles during and after normobaric oxygen therapy: On a swine model

Investigations on acute carbon monoxide (CO) poisoning struggle to highlight a relevant discriminant criterion related to CO poisoning severity for predicting complications, such as delayed neurological syndromes. In this context, it remains difficult to demonstrate the superiority of one method of oxygen (O2) administration over others or to identify the optimal duration of normobaric 100% oxygen (NBO) treatment. Myoglobin, as hemoglobin, are a potential binding site for CO, which could be a source of extravascular CO storage that impacts the severity of CO poisoning. It is not possible in routine clinical practice to estimate this potential extravascular CO storage. Indirect means of doing so that are available in the first few hours of poisoning could include, for example, the carboxyhemoglobin half-life (COHbt1/2), which seems to be influenced itself by the level and duration of CO exposure affecting this store of CO within the body. However, before the elimination of CO can be assessed, the COHbt1/2 toxicokinetic model must be confirmed: research still debates whether this model mono- or bi-compartmental. The second indirect mean could be the assessment of a potential COHb rebound after COHb has returned to 5% and NBO treatment has stopped. Moreover, a COHb rebound could be considered to justify the duration of NBO treatment. On an experimental swine model exposed to moderate CO poisoning (940 ppm for ±118 min until COHb reached 30%), we first confirm that the COHb half-life follows a bi-compartmental model. Secondly, we observe for the first time a slight COHb rebound when COHb returns to 5% and oxygen therapy is stopped. On the basis of these two toxicokinetic characteristics in favor of extravascular CO storage, we recommend that COHbt1/2 is considered using the bi-compartmental model in future clinical studies that compare treatment effectiveness as a potential severity criterion to homogenize cohorts of the same severity. Moreover, from a general toxicokinetic point of view, we confirm that a treatment lasting less than 6 hours appears to be insufficient for treating moderate CO poisoning.

Pathological alterations and COHb evaluations as tools for investigating fire-related deaths in veterinary forensic pathology

Fire-related deaths are usually a consequence of carbon monoxide (CO) poisoning or shock from thermal injuries. In humans, high levels of carboxyhemoglobin (COHb) concentrations in the blood can support a diagnosis of CO poisoning. In veterinary medicine, few studies investigated the pathological changes and blood COHb% in fire victims, and no data are available on post-mortem changes in blood gas composition due to fire. This study aims to investigate the pathological changes and COHb levels in both animal victims of fire and cadavers experimentally exposed to fire. For this purpose, dogs were selected and subdivided into three groups. Group A comprised 9 adult dogs, and Group B comprised 7 puppies that died under fire-related conditions. Group C was represented by 4 dog cadavers experimentally exposed to heat and smoke. A complete macroscopic, histological, and COHb evaluation were performed on each animal. Animals in Groups A and B showed cherry-red discoloration, thermal-injuries and soot deposits along the respiratory tract. Animals in Group C showed thermal injuries and soot deposits limited to the upper respiratory tract. The mean COHb% values in cadavers in Group C were lower than those observed in the other groups but higher compared to the values detected before the heat and smoke treatment. These findings suggest that both pathological changes and COHb analysis are valid tools for investigating fire-related deaths in dogs. However, the increase of COHb levels in cadavers exposed post-mortem to heat and smoke highlights how the COHb analysis should always be evaluated together with macroscopical and microscopical findings to avoid significant misjudgments in investigating fire-related fatalities in veterinary forensic practice.

Carbon monoxide as a cellular protective agent in a swine model of cardiac arrest protocol

Out-of-hospital cardiac arrest (OHCA) affects over 360,000 adults in the United States each year with a 50-80% mortality prior to reaching medical care. Despite aggressive supportive care and targeted temperature management (TTM), half of adults do not live to hospital discharge and nearly one-third of survivors have significant neurologic injury. The current treatment approach following cardiac arrest resuscitation consists primarily of supportive care and possible TTM. While these current treatments are commonly used, mortality remains high, and survivors often develop lasting neurologic and cardiac sequela well after resuscitation. Hence, there is a critical need for further therapeutic development of adjunctive therapies. While select therapeutics have been experimentally investigated, one promising agent that has shown benefit is CO. While CO has traditionally been thought of as a cellular poison, there is both experimental and clinical evidence that demonstrate benefit and safety in ischemia with lower doses related to improved cardiac/neurologic outcomes. While CO is well known for its poisonous effects, CO is a generated physiologically in cells through the breakdown of heme oxygenase (HO) enzymes and has potent antioxidant and anti-inflammatory activities. While CO has been studied in myocardial infarction itself, the role of CO in cardiac arrest and post-arrest care as a therapeutic is less defined. Currently, the standard of care for post-arrest patients consists primarily of supportive care and TTM. Despite current standard of care, the neurological prognosis following cardiac arrest and return of spontaneous circulation (ROSC) remains poor with patients often left with severe disability due to brain injury primarily affecting the cortex and hippocampus. Thus, investigations of novel therapies to mitigate post-arrest injury are clearly warranted. The primary objective of this proposed study is to combine our expertise in swine models of CO and cardiac arrest for future investigations on the cellular protective effects of low dose CO. We will combine our innovative multi-modal diagnostic platform to assess cerebral metabolism and changes in mitochondrial function in swine that undergo cardiac arrest with therapeutic application of CO.

Vacancy-Rich Bismuth-Based Nanosheets for Mitochondrial Destruction via CO Poisoning, Ca2+ Dyshomeostasis, and Oxidative Damage

Mitochondria are core regulators of tumor cell homeostasis, and their damage has become an arresting therapeutic modality against cancer. Despite the development of many mitochondrial-targeted pharmaceutical agents, the exploration of more powerful and multifunctional medications is still underway. Herein, oxygen vacancy-rich BiO2-x wrapped with CaCO3 (named BiO2-x@CaCO3/PEG, BCP) is developed for full-fledged attack on mitochondrial function. After endocytosis of BCP by tumor cells, the CaCO3 shell can be decomposed in the acidic lysosomal compartment, leading to immediate Ca2+ release and CO2 production in the cytoplasm. Near-infrared irradiation enhances the adsorption of CO2 onto BiO2-x defects, which enables highly efficient photocatalysis of CO2-to-CO. Meanwhile, such BiO2-x nanosheets possess catalase-, peroxidase- and oxidase-like catalytic activities under acidic pH conditions, allowing hypoxia relief and the accumulation of diverse reactive oxygen species (ROS) in the tumor microenvironment. Ca2+ overload-induced ion dyshomeostasis, CO-mediated respiratory chain poisoning, ROS-triggered oxidative stress aggravation, and cytosolic hyperoxia can cause severe mitochondrial disorders, which further lead to type I cell death in carcinoma. Not only does BCP cause irreversible apoptosis, but immunogenic cell death is simultaneously triggered to activate antitumor immunity for metastasis inhibition. Collectively, this platform promises high benefits in malignant tumor therapy and may expand the medical applications of bismuth-based nanoagents.

How to Personalize General Anesthesia-A Prospective Theoretical Approach to Conformational Changes of Halogenated Anesthetics in Fire Smoke Poisoning

Smoke intoxication is a central event in mass burn incidents, and toxic smoke acts at different levels of the body, blocking breathing and oxygenation. The majority of these patients require early induction of anesthesia to preserve vital functions. We studied the influence of hemoglobin (HMG) and myoglobin (MGB) blockade by hydrochloric acid (HCl) in an interaction model with gaseous anesthetics using molecular docking techniques. In the next part of the study, molecular dynamics (MD) simulations were performed on the top-scoring ligand-receptor complexes to investigate the stability of the ligand-receptor complexes and the interactions between ligands and receptors in more detail. Through docking analysis, we observed that hemoglobin creates more stable complexes with anesthetic gases than myoglobin. Intoxication with gaseous hydrochloric acid produces conformational and binding energy changes of anesthetic gases to the substrate (both the pathway and the binding site), the most significant being recorded in the case of desflurane and sevoflurane, while for halothane and isoflurane, they remain unchanged. According to our theoretical model, the selection of anesthetic agents for patients affected by fire smoke containing hydrochloric acid is critical to ensure optimal anesthetic effects. In this regard, our model suggests that halothane and isoflurane are the most suitable choices for predicting the anesthetic effects in such patients when compared to sevoflurane and desflurane.

Elucidating the Molecular Pathways and Therapeutic Interventions of Gaseous Mediators in the Context of Fibrosis

Fibrosis, a pathological alteration of the repair response, involves continuous organ damage, scar formation, and eventual functional failure in various chronic inflammatory disorders. Unfortunately, clinical practice offers limited treatment strategies, leading to high mortality rates in chronic diseases. As part of investigations into gaseous mediators, or gasotransmitters, including nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), numerous studies have confirmed their beneficial roles in attenuating fibrosis. Their therapeutic mechanisms, which involve inhibiting oxidative stress, inflammation, apoptosis, and proliferation, have been increasingly elucidated. Additionally, novel gasotransmitters like hydrogen (H2) and sulfur dioxide (SO2) have emerged as promising options for fibrosis treatment. In this review, we primarily demonstrate and summarize the protective and therapeutic effects of gaseous mediators in the process of fibrosis, with a focus on elucidating the underlying molecular mechanisms involved in combating fibrosis.

Carboxyhemoglobin predicts oxygenator performance and imminent oxygenator change in extracorporeal membrane oxygenation

BACKGROUND

The continuous exposure of blood to a non-biological surface during extracorporeal membrane oxygenation (ECMO) may lead to progressive thrombus formation in the oxygenator, hemolysis and consequently impaired gas exchange. In most centers oxygenator performance is monitored only on a once daily basis. Carboxyhemoglobin (COHb) is generated upon red cell lysis and is routinely measured with any co-oximetry performed to surveille gas exchange and acid-base homeostasis every couple of hours. This retrospective cohort study aims to evaluate COHb in the arterial blood gas as a novel marker of oxygenator dysfunction and its predictive value for imminent oxygenator change.

RESULTS

Out of the 484 screened patients on ECMO 89, cumulatively requiring 116 oxygenator changes within 1833 patient days, including 19,692 arterial COHb measurements were analyzed. Higher COHb levels were associated with lower post-oxygenator pO2 (estimate for log(COHb): - 2.176 [95% CI - 2.927, - 1.427], p < 0.0001) and with a shorter time to oxygenator change (estimate for log(COHb): - 67.895 [95% CI - 74.209, - 61.542] hours, p < 0.0001). COHb was predictive of oxygenator change within 6 h (estimate for log(COHb): 5.027 [95% CI 1.670, 15.126], p = 0.004).

CONCLUSION

COHb correlates with oxygenator performance and can be predictive of imminent oxygenator change. Therefore, longitudinal measurements of COHb in clinical routine might be a cheap and more granular candidate for ECMO surveillance that should be further analyzed in a controlled prospective trial design.

Cascade Reactions Catalyzed by Gold Hybrid Nanoparticles Generate CO Gas Against Periodontitis in Diabetes

The treatment of diabetic periodontitis poses a significant challenge due to the presence of local inflammation characterized by excessive glucose concentration, bacterial infection, and high oxidative stress. Herein, mesoporous silica nanoparticles (MSN) are embellished with gold nanoparticles (Au NPs) and loaded with manganese carbonyl to prepare a carbon monoxide (CO) enhanced multienzyme cooperative hybrid nanoplatform (MSN-Au@CO). The Glucose-like oxidase activity of Au NPs catalyzes the oxidation of glucose to hydrogen peroxide (H2O2) and gluconic acid，and then converts H2O2 to hydroxyl radicals (•OH) by peroxidase-like activity to destroy bacteria. Moreover, CO production in response to H2O2, together with Au NPs exhibited a synergistic anti-inflammatory effect in macrophages challenged by lipopolysaccharides. The underlying mechanism can be the induction of nuclear factor erythroid 2-related factor 2 to reduce reactive oxygen species, and inhibition of nuclear factor kappa-B signaling to diminish inflammatory response. Importantly, the antibacterial and anti-inflammation effects of MSN-Au@CO are validated in diabetic rats with ligature-induced periodontitis by showing decreased periodontal bone loss with good biocompatibility. To summarize, MSN-Au@CO is fabricate to utilize glucose-activated cascade reaction to eliminate bacteria, and synergize with gas therapy to regulate the immune microenvironment, offering a potential direction for the treatment of diabetic periodontitis.

Delayed encephalopathy after acute carbon monoxide poisoning: a case study

Delayed encephalopathy after acute carbon monoxide poisoning (DEACMP) is a relatively rare inflammatory-associated neurometabolic complication. In this article, we present a case report of a 50-year-old male patient with a history of carbon monoxide poisoning. This acute poisoning, although successfully controlled during a stay in the intensive care unit of a local hospital, later led to persistent neurological symptoms. The patient was then treated in the inpatient unit of the rehabilitation clinic, where cognitive deterioration began to develop 20 days after admission. Subsequent examination using EEG and magnetic resonance imaging confirmed severe encephalopathy later complicated by SARS-CoV-2 infection with fatal consequences due to bronchopneumonia. Because currently there are no approved guidelines for the management of DEACMP, we briefly discuss the existing challenges for future studies, especially the application of rational immunosuppressive therapy already in the acute treatment phase of CO poisoning, which could prevent the development of a severe form of DEACMP.

Gray matter atrophy and white matter lesions burden in delayed cognitive decline following carbon monoxide poisoning

Gray matter (GM) atrophy and white matter (WM) lesions may contribute to cognitive decline in patients with delayed neurological sequelae (DNS) after carbon monoxide (CO) poisoning. However, there is currently a lack of evidence supporting this relationship. This study aimed to investigate the volume of GM, cortical thickness, and burden of WM lesions in 33 DNS patients with dementia, 24 DNS patients with mild cognitive impairment, and 51 healthy controls. Various methods, including voxel-based, deformation-based, surface-based, and atlas-based analyses, were used to examine GM structures. Furthermore, we explored the connection between GM volume changes, WM lesions burden, and cognitive decline. Compared to the healthy controls, both patient groups exhibited widespread GM atrophy in the cerebral cortices (for volume and cortical thickness), subcortical nuclei (for volume), and cerebellum (for volume) (p < .05 corrected for false discovery rate [FDR]). The total volume of GM atrophy in 31 subregions, which included the default mode network (DMN), visual network (VN), and cerebellar network (CN) (p < .05, FDR-corrected), independently contributed to the severity of cognitive impairment (p < .05). Additionally, WM lesions impacted cognitive decline through both direct and indirect effects, with the latter mediated by volume reduction in 16 subregions of cognitive networks (p < .05). These preliminary findings suggested that both GM atrophy and WM lesions were involved in cognitive decline in DNS patients following CO poisoning. Moreover, the reduction in the volume of DMN, VN, and posterior CN nodes mediated the WM lesions-induced cognitive decline.

Increased Long-Term Risk of Dementia in Patients With Carbon Monoxide Poisoning: A Systematic Review and Meta-Analysis of Cohort Studies

OBJECTIVE

To assess whether carbon monoxide (CO) poisoning increases the incidence of dementia.

METHODS

We searched the Cochrane Library, PubMed, and EMBASE from inception to 14 August 2022. Two authors independently selected studies, assessed the quality of included studies, and extracted data. Any disagreement was resolved by discussion with a third author. Only cohort study with an enough follow-up period was included for systematic reviews and meta-analysis.

RESULTS

Thirty-three full texts were initially searched, but only three studies met our inclusion criteria, and they were comprised of 134,563 participants who were initially free of dementia. The follow-up period ranged from 9 to 12 years. We found that CO poisoning increased the risk of dementia incidence (adjusted hazard ratio 2.61, 95% confidence interval 1.56 to 4.36, p=0.0003). Subgroup analysis showed that the increased dementia risk was significant in males but not in females, and the highest risk was in young age group, followed by in middle age group, but not in the old one.

CONCLUSION

Overall the evidence from prospective cohort studies supported a link between CO exposure and an increased dementia risk, although all the included studies were limited to Taiwanese population.

Comparing high-flow nasal oxygen therapy and normobaric oxygen therapy on the treatment of carbon monoxide poisoning

AIM

We aimed to investigate whether there is a difference in the rate of decrease in carboxyhemoglobin (COHB) values between high-flow nasal oxygen (HFNO) and normobaric oxygen (NBO) therapy.

MATERIAL AND METHOD

This retrospective observational study included patients with carbon monoxide poisoning who were treated with HFNO or NBO (control group). All patients were started on NBO therapy with a non-rebreather face mask at a rate of 15 L/min. In the NBO group, NBO treatment was continued until the COHB value fell below 10%. In the HFNO group, as soon as the preparation of the HFNO device was completed, NBO treatment was terminated and HFNO treatment was started and continued until the COHB value fell below 10%. The primary outcome of the study was the difference between HFNO and NBO in terms of COHB half-life rates.

RESULTS

A total of 81 patients were included in the study, 44 in the HFNO group and 37 in the NBO group. The median of COHB t1/2 values between HFNO and the NBO treatment groups were 47.3 (IQR: 25-75%: 31.5-65.4) and 46 (IQR: 25-75%: 32.3-56.2), respectively, but this difference was not statistically significant (p = 0.81).

CONCLUSION

The results of this study suggest that HFNO treatment does not have a significant advantage over NBO treatment in the carbon monoxide elimination rate within the first 60 min of treatment.

Divergent synthesis of carbamates and N-methyl carbamates from dimethyl carbonate and nitroarenes with Mo(CO)6 as a multiple promoter

Dialkyl carbonates are green and versatile reagents that can be used in alkylation and alkoxycarbonylation reactions. Herein, we disclosed a reductive methoxycarbonylation of aromatic nitro compounds with dimethyl carbonate for the construction of diverse carbamates and N-methyl carbamates. Using Mo(CO)6 as a multiple promoter, different nitroarenes were smoothly transformed into the corresponding carbamates in yields between 27 and 94% using DMC as both solvent and reagent. It is worth noting that the choice of different bases allowed the desired products to be controlled: K3PO4 favoured the formation of carbamates as the primary product, whereas DBU facilitated the formation of N-methyl carbamates as the main product.

Carbon monoxide affects early cardiac development in an avian model

INTRODUCTION

Carbon monoxide (CO) is a toxic gas that can be lethal in large doses and may also cause physiological damage in lower doses. Epidemiological studies suggest that CO in lower doses over time may impact on embryo development, in particular cardiac development, however other studies have not observed this association.

METHODS

Here, we exposed chick embryos in ovo to CO at three different concentrations (3, 9, 18 ppm) plus air control (4 protocols in total) for the first 9 days of development, at which point we assessed egg and embryo weight, ankle length, developmental stage, heart weight, ventricular wall thickness, ventricular-septal thickness and atrial wall thickness.

RESULTS

We found that heart weight was reduced for the low and moderate exposures compared to air, that atrial wall and ventricular wall thickness was increased for the moderate and high exposures compared to air and that ventricular septal thickness was increased for low, moderate and high exposures compared to air. Ventricular wall thickness was also significantly positively correlated with absolute CO exposures across all protocols.

CONCLUSIONS

This intervention study thus suggests that CO even at very low levels may have a significant impact on cardiac development.

Demographics and clinical characteristics of carbon monoxide poisoning for patients attending in the emergency department at a tertiary hospital in Riyadh, Saudi Arabia

BACKGROUND

Carbon Monoxide (CO) is one of the most common environmental causes of acute intoxication globally. It can lead to the development of Delayed Neuropsychiatric Sequelae (DNS) which may develop in 2-40 days after remission of acute CO poisoning. DNS is defined by recurrent-transient neurological, cognitive, or psychological manifestations. This study was intended to describe the demographics and characteristics of CO poisoning patients attending at the Emergency Department (ED) and assess the association between CO intoxication and the development of DNS in a tertiary hospital, Riyadh, Saudi Arabia.

METHODS

A retrospective descriptive cross-sectional study was conducted in subjects who were diagnosed with CO poisoning and attended to the ED at King Abdulaziz Medical City (KAMC) and King Abdullah Specialist Children's Hospital (KASCH) in Riyadh during the period from January 2016 to December 2021. Patient demographics, vitals, diagnostic tests, and oxygen therapy at initial presentation were documented. Patient medical records were reviewed at 2-40 days following CO poisoning for development of DNS. Ethical approval was obtained from King Abdullah International Medical Research Center (KAIMRC).

RESULTS

A total of 85 patients were diagnosed with CO poisoning and met the study inclusion criteria. Of those, 76% were adults with an average age of 32.36 (SD ± 15.20) and 51% were male adults. Five (6%) of the 85 patients developed DNS. Common symptoms included dizziness, nausea, and decreased visual acuity in 40% of the cases. The development of DNS manifestations was most likely (80%) to occur at 2 to 10 days after the initial incident. Inferential statistics showed that BMI (p-value = 0.021) and age group (p-value = 0.029) were significantly associated with COHb level, which was not the case for gender and the presence of clinical manifestation. Furthermore, Gender was significantly associated with the development of DNS (20% male vs. 80% female, p = 0.050).

CONCLUSIONS

The findings of this study are consistent with previous published studies showing low proportions of patients who were exposed to CO poisoning at risk of developing DNS. Further larger-scale multicenter studies are needed to assess the factors associated with the development of DNS for patients with CO poisoning.

Practical Recommendations for the Evaluation and Management of Cardiac Injury Due to Carbon Monoxide Poisoning

Carbon monoxide (CO) is a relatively frequent cause of poisoning evaluated in emergency departments. The risk of neurologic injuries, such as cognitive, psychological, vestibular, and motor deficits, is 25% to 50%. However, the risk of cardiac injuries should also be considered. Among patients with CO poisoning, the mortality in patients with myocardial injury is approximately 3 times greater than that in patients without myocardial injury. In large-scale studies, up to 69.2% of patients with acute CO poisoning exhibiting elevated troponin I levels and no underlying cardiovascular illnesses had late gadolinium enhancement on cardiac magnetic resonance, suggesting covert CO-induced myocardial fibrosis. Myocardial damage can be evaluated using electrocardiography, echocardiography, computed tomography, and cardiac magnetic resonance. This paper offers recommendations for cardiac evaluations based on our collective experience of managing >2,000 cases of acute CO poisoning with supporting information taken from peer-reviewed published reports on CO poisoning.

Clinical factors for delayed neuropsychiatric sequelae from acute carbon monoxide poisoning: a retrospective study

Background

Delayed neuropsychiatric sequelae (DNS), which seriously affect the daily lives of patients, are the most common complications of carbon monoxide (CO) poisoning. No uniform screening tool is available for identifying high-risk groups. Therefore, in this study, we aimed to explore whether conventional laboratory indicators and imaging data from primary hospitals could predict the occurrence of DNS.

Methods

This retrospective observational study was conducted in a single-center primary hospital from January 1, 2021 to May 31, 2023. Participants included patients aged >18 years with acute CO poisoning. Patients with complete recovery in the acute phase were followed up by telephone and outpatient visits, and the presence of DNS was determined according to the occurrence of new neurological symptoms within 6 weeks after discharge. We obtained demographic, laboratory, and imaging data from the medical records and performed a univariate analysis. A multivariate logistic regression model was used to identify independent clinical predictors of DNS.

Results

A total of 73 patients were included in the study, of whom 25 (34.2%) developed DNS. Multivariate logistic regression analysis revealed that a longer duration of CO exposure (adjusted odds ratio (AOR): 1.262, 95% confidence interval (CI): 1.069-1.490) and the presence of acute brain lesions on diffusion-weighted imaging (DWI) (AOR: 5.117, 95% CI: 1.430-18.315) were independent risk factors for DNS. Receiver operating characteristic analyses of the duration of CO exposure were performed (area under the curve (AUC): 0.825; 95% CI: 0.731-0.918) with a cut-off value of 5.5 h, and DNS was predicted with a sensitivity of 96% and a specificity of 66.7%.

Conclusion

High cranial DWI signal within 24 h and duration of poisoning longer than 5.5 h are independent predictors of DNS. The predictive effects of conventional laboratory indicators require further standardized and large-sample studies.

Targeting Ferroptosis Promotes Functional Recovery by Mitigating White Matter Injury Following Acute Carbon Monoxide Poisoning

Survivors experiencing acute carbon monoxide poisoning (ACMP) tend to develop white matter injury (WMI). The mechanism of ACMP-induced WMI remains unclear. Considering the role of ferroptosis in initiating oligodendrocyte damage to deteriorate WMI, exploring therapeutic options to attenuate ferroptosis is a feasible approach to alleviating WMI. Our results indicated that ACMP induced accumulation of iron and reactive oxygen species (ROS) eventually leading to WMI and motor impairment after ACMP. Furthermore, ferrostatin-1 reduced iron and ROS deposition to alleviate ferroptosis, thereafter reducing WMI to promote the recovery of motor function. The nuclear factor erythroid-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway was found to be involved in alleviating ferroptosis as seen with the administration of ferrostatin-1. The present study rationalizes that targeting ferroptosis to alleviate WMI is a feasible therapeutic strategy for managing ACMP.

Optic nerve sheath diameter measurements to predict delayed neurological sequelae after carbon monoxide poisoning

OBJECTIVES

Delayed neurological sequelae are a major complication of carbon monoxide poisoning. However, today there is still no objective screening tool for predicting delayed neurological sequelae in patients with carbon monoxide poisoning. The present study aimed to assess the usefulness of optic nerve sheath diameter measurements in predicting delayed neurological sequelae after carbon monoxide poisoning.

METHODS

In this retrospective study, patients with a diagnosis of carbon monoxide poisoning in the emergency department from 2010 to 2021 were included in the study. Right and left optic nerve sheath diameters were calculated based on cranial computed tomography scans, and the presence of delayed neurological sequelae was evaluated.

RESULTS

The mean (± standard deviation) optic nerve sheath diameter in patients who developed delayed neurological sequelae was statistically significantly greater on both the right and left compared to patients who did not develop delayed neurological sequelae (right; 5.02 ± 0.06 mm versus 4.89 ± 0.07 mm, P < 0.001; left; 5.03 ± 0.09 mm versus 4.85 ± 0.10 mm, P < 0.001). A multivariate linear regression analysis revealed that carboxyhemoglobin and both right and left optic nerve sheath diameter were the factors associated with the delayed neurological sequelae.

DISCUSSION

The present study revealed that optic nerve sheath diameter measurements may be a useful screening tool to predict delayed neurological sequelae after carbon monoxide poisoning. The ability to predict a poor neurological prognosis in carbon monoxide poisoning is important for initiating early rehabilitation interventions and make help future trials. Limitations of this study include that normal optic nerve sheath diameters are not well established, and that not every patient underwent computed tomography.

CONCLUSIONS

Optic nerve sheath diameters measurements may be a helpful screening tool for predicting delayed neurological sequelae after carbon monoxide poisoning.

Carbon monoxide poisoning: A problem uniquely suited to a medicinal inorganic chemistry solution

Carbon monoxide poisoning is one of the most common forms of poisoning in the world. Although the primary mode of treatment, oxygen therapy, is highly effective in many cases, there are instances in which it is inadequate or inappropriate. Whereas oxygen therapy relies on high levels of a low-affinity ligand (O2) to displace a high-affinity ligand (CO) from metalloproteins, an antidote strategy relies on introducing a molecule with a higher affinity for CO than native proteins (Kantidote,CO > Kprotein,CO). Based on the fundamental chemistry of CO, such an antidote is most likely required to be an inorganic compound featuring an electron-rich transition metal. A review is provided of the protein-, supramolecular complex-, and small molecule-based CO poisoning antidote platforms that are currently under investigation.

Correlation between Carboxyhemoglobin Levels Measured by Blood Gas Analysis and by Multiwave Pulse Oximetry

Carbon monoxide (CO) poisoning is difficult to diagnose owing to its nonspecific symptoms. Multiwave pulse oximetry can be used to quickly screen patients for CO poisoning. However, few studies have analyzed patients with CO poisoning who presented to the emergency department (ED). The primary aim of our study was to determine the correlation between COHb levels measured in blood gas analysis and COHb levels measured in multiwave pulse oximetry. Secondary aims were the sensitivity and specificity of the COHb level cutoff value using multiwave pulse oximetry to predict a 25% COHb level in blood gas analysis. This single-center retrospective observational study included patients with CO poisoning who visited the ED of a university-affiliated hospital in Seoul, Korea between July 2021 and June 2023. COHb poisoning was determined using blood gas analysis and multiwave pulse oximetry. The correlation of COHb levels between the two tests was evaluated using correlation analysis. The area under the receiver operating characteristic curve (AUC) of multiwave pulse oximetry was calculated to predict COHb levels from the blood gas analysis. The optimal cutoff values, sensitivity, and specificity of COHb were determined. A total of 224 patients who had COHb levels measured using both multiwave pulse oximetry and blood gas analysis were included in the analysis. In the correlation analysis, COHb showed a high positive correlation with COHb measured using blood gas analysis (Spearman correlation coefficient = 0.86, p < 0.001). The AUC of COHb measured by multiwave pulse oximetry to predict 25% of the COHb level (which can be an indication of hyperbaric oxygen treatment) measured by blood gas analysis was 0.916. When the COHb levels measured with multiwave pulse oximetry were 20% the sensitivity was 81% and the specificity was 83%, and when the COHb levels were 25% the sensitivity was 50% and the specificity was 95%. The COHb value measured using multiwave pulse oximetry blood gas analysis showed a high correlation. However, additional research using large-scale studies is required for validation.

Long-term air pollution and adverse meteorological factors might elevate the osteoporosis risk among adult Chinese

Objective

This study aims to investigate the relationship between exposure to air pollution and adverse meteorological factors, and the risk of osteoporosis.

Methods

We diagnosed osteoporosis by assessing bone mineral density through Dual-Energy X-ray absorptiometry in 2,361 participants from Jiangsu, China. Additionally, we conducted physical examinations, blood tests, and questionnaires. We evaluated pollution exposure levels using grid data, considering various lag periods (ranging from one to five years) based on participants' addresses. We utilized logistic regression analysis, adjusted for temperature, humidity, and individual factors, to examine the connections between osteoporosis and seven air pollutants: PM₁, PM₂.₅, PM₁₀, SO₂, NO₂, CO, and O₃. We assessed the robustness of our study through two-pollutant models and distributed lag non-linear models (DLNM) and explored susceptibility using stratified analyses.

Results

In Jiangsu, China, the prevalence of osteoporosis among individuals aged 40 and above was found to be 15.1%. A consistent association was observed between osteoporosis and the five-year average exposure to most pollutants, including PM₂.₅, PM₁₀, CO, and O₃. The effects of PM₁₀ and CO remained stable even after adjusting for the presence of a second pollutant. However, the levels of PM₁ and PM₂.₅ were significantly influenced by O₃ levels. Individuals aged 60 and above, those with a BMI of 25 or higher, and males were found to be more susceptible to the effects of air pollution. Interestingly, males showed a significantly higher susceptibility to PM₁ and PM₂.₅ compared to females. This study provides valuable insights into the long-term effects of air pollution on osteoporosis risk among the adult population in China.

Conclusion

This study indicates a potential association between air pollutants and osteoporosis, particularly with long-term exposure. The risk of osteoporosis induced by air pollution is found to be higher in individuals aged 60 and above, those with a BMI greater than 25, and males. These findings underscore the need for further research and public health interventions to mitigate the impact of air pollution on bone health.

Carbon Monoxide Poisoning: From Microbes to Therapeutics

Carbon monoxide (CO) poisoning leads to 50,000-100,000 emergency room visits and 1,500-2,000 deaths each year in the United States alone. Even with treatment, survivors often suffer from long-term cardiac and neurocognitive deficits, highlighting a clear unmet medical need for novel therapeutic strategies that reduce morbidity and mortality associated with CO poisoning. This review examines the prevalence and impact of CO poisoning and pathophysiology in humans and highlights recent advances in therapeutic strategies that accelerate CO clearance and mitigate toxicity. We focus on recent developments of high-affinity molecules that take advantage of the uniquely strong interaction between CO and heme to selectively bind and sequester CO in preclinical models. These scavengers, which employ heme-binding scaffolds ranging from organic small molecules to hemoproteins derived from humans and potentially even microorganisms, show promise as field-deployable antidotes that may rapidly accelerate CO clearance and improve outcomes for survivors of acute CO poisoning.

Current trends in gas-synergized phototherapy for improved antitumor theranostics

Phototherapy, such as photothermal therapy (PTT) and photodynamic therapy (PDT), has been considered an elegant solution to eradicate tumors due to its minimal invasiveness and low systemic toxicity. Nevertheless, it is still challenging for phototherapy to achieve ideal outcomes and clinical translation due to its inherent drawbacks. Owing to the unique biological functions, diverse gases have attracted growing attention in combining with phototherapy to achieve super-additive therapeutic effects. Specifically, gases such as nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S) have been proven to kill tumor cells by inducing mitochondrial damage in synergy with phototherapy. Additionally, several gases not only enhance the thermal damage in PTT and the reactive oxygen species (ROS) production in PDT but also improve the tumor accumulation of photoactive agents. The inflammatory responses triggered by hyperthermia in PTT are also suppressed by the combination of gases. Herein, we comprehensively review the latest studies on gas-synergized phototherapy for cancer therapy, including (1) synergistic mechanisms of combining gases with phototherapy; (2) design of nanoplatforms for gas-synergized phototherapy; (3) multimodal therapy based on gas-synergized phototherapy; (4) imaging-guided gas-synergized phototherapy. Finally, the current challenges and future opportunities of gas-synergized phototherapy for tumor treatment are discussed. STATEMENT OF SIGNIFICANCE: 1. The novelty and significance of the work with respect to the existing literature. (1) Strategies to design nanoplatforms for gas-synergized anti-tumor phototherapy have been summarized for the first time. Meanwhile, the integration of various imaging technologies and therapy modalities which endow these nanoplatforms with advanced theranostic capabilities has been summarized. (2) The mechanisms by which gases synergize with phototherapy to eradicate tumors are innovatively and comprehensively summarized. 2. The scientific impact and interest. This review elaborates current trends in gas-synergized anti-tumor phototherapy, with special emphases on synergistic anti-tumor mechanisms and rational design of therapeutic nanoplatforms to achieve this synergistic therapy. It aims to provide valuable guidance for researchers in this field.

Prognostic value of systemic immune-inflammation index and monocyte-to-HDL-cholesterol ratio in early cardio-cerebral complications in elderly patients with acute severe carbon monoxide poisoning

To investigate how effectively systemic immune-inflammation index (SII) and Monocyte-to-HDL-cholesterol ratio (MHR) predict the development of early cardio-cerebral complications in elderly patients who have experienced acute severe carbon monoxide poisoning (ASCMP). A retrospective analysis was conducted on 77 elderly patients with ASCMP admitted to the emergency department of Harrison International Peace Hospital from November 2020 to March 2022. The prevalence of early-onset complications among the 77 individuals was 38.96%. Binary Logistics regression analysis showed that SII and MHR were independent influencing factors of early cardio-cerebral complications in elderly patients with ASCMP. The complication group had a longer length of stay, a greater mortality rate, and a higher incidence of delayed encephalopathy after acute carbon monoxide poisoning (p < .05) than the non-complication group. The area under the curve (AUC) of SII and MHR in predicting early cardio-cerebral complications in elderly patients with ASCMP were 0.724 and 0.796, respectively, with 80.0% and 63.3% sensitivity, and 61.7% and 87.2% specificity. The incidence of early cardio-cerebral complications in elderly patients who had ASCMP is high and the prognosis is poor. SII and MHR can be utilized as independent predictors of early cardio-cerebral complications in elderly patients with ASCMP, allowing doctors to diagnose and treat cardio-cerebral complications earlier and improve prognosis.

Neurological Sequelae After Acute Carbon Monoxide Poisoning

Carbon monoxide poisoning (COP) is a common cause of death due to poisoning. After COP, a significant number of patients may develop a distinct type of neurological dysfunction called delayed neurological sequel (DNS). Recently, we came across a disaster of COP cases after a fire in a shared accommodation. The hostel was overcrowded and had a faulty air-conditioning/exhaust system. A total of five patients with loss of consciousness and shock were brought to us. They were diagnosed with acute COP based on their history of exposure to carbon monoxide (CO) and elevated carboxyhemoglobin levels in blood gas measurements. All patients were intubated and mechanically ventilated. Standard intensive care management was given to them, which included oxygenation, sedation, fluid resuscitation, and vasopressors. Their carboxyhemoglobin was rapidly reversed with normobaric oxygen therapy (NBO2). Three patients showed good response and neurological recovery after NBO2. Unfortunately, two patients developed DNS. DNS is a neuropsychological condition that may have cognitive, psychiatric, vestibulocochlear, motor, sensory, or diffuse demyelinating effects after COP. DNS is diagnosed in patients with a typical history of exposure to CO and a constellation of signs and symptoms. Neuroimaging, specifically magnetic resonance imaging of the brain with gadolinium contrast, is the method of choice for diagnosis. Treatment of DNS after COP begins with anticipation. All patients should receive appropriate oxygen therapy to bring down carboxyhemoglobin as soon as possible. Hyperbaric oxygen therapy (HBO2) for the treatment of COP and prevention of DNS is still debatable. In the available medical literature, there are conflicting recommendations regarding the use of HBO2 in COP/DNS. Moreover, apart from a lack of consensus, there is also a lack of clarity about optimum timing, duration, atmospheric pressure, and number of sessions of HBO2 in preventing DNS after COP. The development of DNS after COP is not directly responsible for mortality, but recovery sometimes takes a long time, which can contribute to increased morbidity and costs of treatment.

Investigation of Cerebral Mitochondrial Injury in a Porcine Survivor Model of Carbon Monoxide Poisoning

INTRODUCTION

Carbon monoxide (CO) is a colorless and odorless gas that is a leading cause of environmental poisoning in the USA with substantial mortality and morbidity. The mechanism of CO poisoning is complex and includes hypoxia, inflammation, and leukocyte sequestration in brain microvessel segments leading to increased reactive oxygen species. Another important pathway is the effects of CO on the mitochondria, specifically at cytochrome c oxidase, also known as Complex IV (CIV). One of the glaring gaps is the lack of rigorous experimental models that may recapitulate survivors of acute CO poisoning in the early phase. The primary objective of this preliminary study is to use our advanced swine platform of acute CO poisoning to develop a clinically relevant survivor model to perform behavioral assessment and MRI imaging that will allow future development of biomarkers and therapeutics.

METHODS

Four swine (10 kg) were divided into two groups: control (n = 2) and CO (n = 2). The CO group received CO at 2000 ppm for over 120 min followed by 30 min of re-oxygenation at room air for one swine and 150 min followed by 30 min of re-oxygenation for another swine. The two swine in the sham group received room air for 150 min. Cerebral microdialysis was performed to obtain semi real-time measurements of cerebral metabolic status. Following exposures, all surviving animals were observed for a 24-h period with neurobehavioral assessment and imaging. At the end of the 24-h period, fresh brain tissue (cortical and hippocampal) was immediately harvested to measure mitochondrial respiration.

RESULTS

While a preliminary ongoing study, animals in the CO group showed alterations in cerebral metabolism and cellular function in the acute exposure phase with possible sustained mitochondrial changes 24 h after the CO exposure ended.

CONCLUSIONS

This preliminary research further establishes a large animal swine model investigating survivors of CO poisoning to measure translational metrics relevant to clinical medicine that includes a basic neurobehavioral assessment and post exposure cellular measures.

Carbon monoxide and prognosis in smokers hospitalised with acute cardiac events: a multicentre, prospective cohort study

Background

Smoking cigarettes produces carbon monoxide (CO), which can reduce the oxygen-carrying capacity of the blood. We aimed to determine whether elevated expiratory CO levels would be associated with a worse prognosis in smokers presenting with acute cardiac events.

Methods

From 7 to 22 April 2021, expiratory CO levels were measured in a prospective registry including all consecutive patients admitted for acute cardiac event in 39 centres throughout France. The primary outcome was 1-year all-cause death. Initial in-hospital major adverse cardiac events (MAE; death, resuscitated cardiac arrest and cardiogenic shock) were also analysed. The study was registered at ClinicalTrials.gov (NCT05063097).

Findings

Among 1379 patients (63 ± 15 years, 70% men), 368 (27%) were active smokers. Expiratory CO levels were significantly raised in active smokers compared to non-smokers. A CO level >11 parts per million (ppm) found in 94 (25.5%) smokers was associated with a significant increase in death (14.9% for CO > 11 ppm vs. 2.9% for CO ≤ 11 ppm; p < 0.001). Similar results were found after adjustment for comorbidities (hazard ratio [HR] [95% confidence interval (CI)]): 5.92 [2.43-14.38]) or parameters of in-hospital severity (HR 6.09, 95% CI [2.51-14.80]) and propensity score matching (HR 7.46, 95% CI [1.70-32.8]). CO > 11 ppm was associated with a significant increase in MAE in smokers during initial hospitalisation after adjustment for comorbidities (odds ratio [OR] 15.75, 95% CI [5.56-44.60]) or parameters of in-hospital severity (OR 10.67, 95% CI [4.06-28.04]). In the overall population, CO > 11 ppm but not smoking was associated with an increased rate of all-cause death (HR 4.03, 95% CI [2.33-6.98] and 1.66 [0.96-2.85] respectively).

Interpretation

Elevated CO level is independently associated with a 6-fold increase in 1-year death and 10-fold in-hospital MAE in smokers hospitalized for acute cardiac events.

Funding

Grant from Fondation Coeur & Recherche.

Pollutant-meteorological factors and cardio-respiratory mortality in Portugal: Seasonal variability and associations

Seasonal variations in cardiorespiratory diseases may be influenced by air pollution and meteorological factors. This work aims to highlight the relevance of a complete seasonal characterization of the pollutant-meteorological factors and cardio-respiratory mortality in Portugal and the relationships between health outcomes and environmental risk factors. To this end, air pollution and meteorological variables along with health outcomes were analyzed at national level and on a monthly basis for the period of 2011-2020. It was found that cardiorespiratory mortality rates during winter were 44% higher than during the summer. Furthermore, particulate matter with aerodynamic diameters of 10 and 2.5 μm (μm) or smaller (PM10 and PM2.5), carbon monoxide (CO) and nitrogen dioxide (NO2) showed a seasonal variability with the highest concentrations during winter while ozone (O3) presented higher concentrations during spring and summer. PM10, PM2.5 and NO2, showed a positive correlation between seasons, indicating similar patterns of behavior. Canonical correlation analysis (CCA) applied to pollutant-meteorological and cardiorespiratory mortality data indicates a strong linear correlation between pollutant-meteorological factors and health outcomes. The first canonical correlation was 0.889, and the second was 0.545, both statistically significant (p-value < 0.001). The CCA results suggest that there is a strong association between near-surface temperature, relative humidity, PM10, PM2.5, CO and NO2 and health outcomes. The results of this study provide important information of the seasonal variability of air pollutants and meteorological factors in Portugal and their associations with cardiorespiratory mortality.

The diagnostic accuracy of carbon monoxide pulse oximetry in adults with suspected acute carbon monoxide poisoning: a systematic review and meta-analysis

Introduction

Acute carbon monoxide poisoning (COP) is one of the leading causes of intoxication among patients presenting to the emergency department (ED). COP symptoms are not always specific and may vary from mild to critical. In the last few years, COHb pulse oximeters have been developed and applied to the setting of suspected COP. The aim of this systematic review is to assess the diagnostic accuracy of CO pulse oximetry (SpCO) with carboxyhemoglobin (COHb) levels measured by blood gas analysis, used as a reference standard, in patients with suspected COP.

Methods

We developed our search strategy according to the PICOS framework, population, index/intervention, comparison, outcome, and study, considering the diagnostic accuracy of SpCO compared to COHb levels measured by blood gas analysis, used as a reference standard, in patients with suspected COP enrolled in cross-sectional studies in English. The search was performed on MEDLINE/PubMed and EMBASE in February 2022. Quality assessment was performed using the QUADAS-2 methodology. A COHb cutoff of 10% was chosen to test the sensitivity and specificity of the index test. A bivariate model was used to perform the meta-analysis. The protocol was registered on PROSPERO (CRD42022359144).

Results

A total of six studies (1734 patients) were included. The pooled sensitivity of the test was 0.65 (95% CI 0.44-0.81), and the pooled specificity was 0.93 (95% CI 0.83-0.98). The pooled LR+ was 9.4 (95% CI 4.4 to 20.1), and the pooled LR- was 0.38 (95% CI 0.24 to 0.62).

Conclusion

Our results show that SpCO cannot be used as a screening tool for COP in the ED due to its low sensitivity. Because of its high LR+, it would be interesting to evaluate, if SpCO could have a role in the prehospital setting as a tool to quickly identify COP patients and prioritize their transport to specialized hospitals on larger samples with a prospective design.

Clinical and Echocardiographic Predictors for the Presence of Late Gadolinium Enhancement on Cardiac Magnetic Resonance Imaging in Patients with Carbon Monoxide Poisoning

Late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging (CMRI) reflects the burden of myocardial damage in carbon monoxide (CO) poisoning. This study aimed to identify the clinical and echocardiographic parameters that can predict myocardial LGE on CMRI in CO poisoning. This prospective observational study included patients who presented with acute CO poisoning and elevated troponin I and underwent echocardiography and CMRI to identify myocardial damage at a tertiary university hospital between August 2017 and May 2019 and August 2020 and July 2022. Based on the CMRI findings, participants were categorized into LGE and non-LGE groups. The median age of the 155 patients was 51.0 years, and 98 (63.2%) were males. Median times from emergency department arrival to either CMRI or echocardiography were 3.0 days each. The LGE group included 99 (63.9%) patients with LGE positivity on CMRIs. Time from rescue to hyperbaric oxygen therapy >4 h (odds ratio (OR): 3.31, 95% confidence interval (CI): 1.28-8.56, p = 0.01); serum lactate levels >2 mmol/L (OR: 2.62, 95% CI: 1.20-5.73, p = 0.02); and left ventricular global longitudinal strain >-16% (OR: 2.95, 95% CI: 1.35-6.47, p = 0.007) were significant predictors of LGE positivity. The area under the curve of these predictors was 0.711. Our prediction model, which combines the clinical parameters with left ventricular global longitudinal strain, may be helpful in the early detection of LGE positivity.

Predicting acute brain lesions on magnetic resonance imaging in acute carbon monoxide poisoning: a multicenter prospective observational study

An acute brain lesion (ABL) identified by brain magnetic resonance imaging (MRI) after acute carbon monoxide (CO) poisoning is a strong prognostic factor for the development of delayed neuropsychiatric syndrome (DNS). This study aimed to identify predictors of ABLs on MRI in patients with acute CO poisoning. This was a multicenter prospective registry-based observational study conducted at two tertiary hospitals. A total of 1,034 patients were included. Multivariable logistic regression analysis showed that loss of consciousness (LOC) (adjusted odds ratio [aOR] 2.68, 95% Confidence Interval [CI]: 1.49-5.06), Glasgow Coma Scale (GCS) score < 9 (aOR 2.41, 95% CI: 1.49-3.91), troponin-I (TnI) (aOR 1.22, 95% CI: 1.08-1.41), CO exposure duration (aOR 1.09, 95% CI: 1.05-1.13), and white blood cell (WBC) (aOR 1.05, 95% CI: 1.01-1.09) were independent predictors of ABLs on MRI. LOC, GCS score, TnI, CO exposure duration, and WBC count can be useful predictors of ABLs on MRI in patients with acute CO poisoning, helping clinicians decide the need for an MRI scan or transfer the patient to an appropriate institution for MRI or hyperbaric oxygen therapy.

Acute Carbon Monoxide Poisoning in a Filipino Household: A Case Report

There are multiple reports already regarding acute carbon monoxide (CO) poisoning in the Philippines secondary to the misuse of portable generators, especially during times of typhoons. We present a case of unintentional carbon monoxide poisoning in a Filipino household wherein our index patient is among the five members who were unconscious before they were rushed to the hospital. Three of the household members, on the other hand, were found dead. The index patient had an increased serum fraction percentage of carboxyhemoglobin level and presented with rhabdomyolysis during admission. Neuroimaging confirmed a hypoxic-ischemic encephalopathy secondary to carbon monoxide intoxication. Even without hyperbaric oxygen therapy, the patient improved with adequate hydration, early rehabilitation, and trauma-focused psychotherapy.

From Carbon Monoxide Poisoning to Myocardial Infarction

Myocardial injury is a known complication following acute carbon monoxide (CO) poisoning, yet there is little literature on this subject. Here, we present the case of a 56-year-old man admitted to the emergency room with severe CO poisoning. The electrocardiogram (ECG) at admission revealed an ST-segment elevation in leads II, III, and aVF, with an elevated troponin-T level. The patient was initially treated with hyperbaric oxygen, with improvement of symptoms and ECG normalization. He was later admitted for coronary angiography, which revealed an occlusion of the right coronary artery. This case aims to highlight an often-overlooked complication of CO intoxication and the need for more studies to better guide the treatment of these patients.

Hyperbaric oxygen treatment in carbon monoxide poisoning - Does it really matter?

Carbon monoxide (CO) is an odorless and colorless gas that can lead to fulminant and life-threatening intoxications. Besides an early diagnosis, an appropriate treatment of the intoxication is important. In this context the reduction of CO concentration in blood and tissues is crucial revealing hyperbaric oxygen treatment (HBO) as a highly promising tool. However, the benefit of HBO in CO intoxications is still considered controversial. In this review, we discuss the evidence of the role of HBO treatment in isolated CO intoxication.

Comparison of exhaled carbon monoxide levels and its association with nicotine dependence between electronic and tobacco cigarettes: A cross-sectional study among teenage smokers

Carbon monoxide (CO), resulting from incomplete combustion such as tobacco smoking, serves as an indicator of nicotine addiction. The aim of this study was to compare the levels of exhaled CO levels between electronic cigarette (e-cigarette) and tobacco smokers and to determine the association between nicotine dependence and exhaled CO levels in e-cigarette and tobacco smokers. A cross-sectional study was conducted using purposive sampling on active smokers, with 70 smokers in each group. The nicotine dependence was measured using the Penn State Nicotine Dependence Index (PSNDI) questionnaire for the e-cigarette group and the Fagerstrom questionnaire for the tobacco smoking group. The CO level was measured using the smokerlyzer piCO. To compare the mean exhaled CO levels between e-cigarettes and tobacco smoker groups, the Mann-Whitney test was used. The Mann-Whitney test and Kruskal-Wallis test were used to assess the associations between nicotine dependence and mean exhaled CO levels in the e-cigarette smoker group and in the tobacco smoker group, respectively. The majority of e-cigarette smokers were 17 years old (65.7%) and male (75.7%). Among tobacco smokers, the majority were also 17 years old (44.3%), and mostly male (91.4%). The mean exhaled CO levels in the tobacco smoker group were significantly higher than the e-cigarette smoker group, 6.86 ppm vs 1.61 ppm with p<0.001. There was a significant association between nicotine dependence and exhaled CO levels among tobacco smokers (p<0.001). Nicotine dependence was not associated with exhaled CO levels among e-cigarette smokers. This study highlights that the smokerlyzer piCO devise could be used to screen nicotine addiction in tobacco smokers.

Hourly Air Pollution Exposure and Emergency Hospital Admissions for Stroke: A Multicenter Case-Crossover Study

BACKGROUND

Daily exposure to ambient air pollution is associated with stroke morbidity and mortality; however, the association between hourly exposure to air pollutants and risk of emergency hospital admissions for stroke and its subtypes remains relatively unexplored.

METHODS

We obtained hourly concentrations of fine particulate matter (PM2.5), respirable particulate matter (PM10), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and carbon monoxide (CO) from the China National Environmental Monitoring Center. We conducted a time-stratified case-crossover study among 86 635 emergency hospital admissions for stroke across 10 hospitals in 3 cities (Jinhua, Hangzhou, and Zhoushan) in Zhejiang province, China, between January 1, 2016 and December 31, 2021. Using a conditional logistic regression combined with a distributed lag linear model, we estimated the association between hourly exposure to multiple air pollutants and risk of emergency hospital admissions for total stroke, ischemic stroke, hemorrhagic stroke, and undetermined type.

RESULTS

Hourly exposure to PM2.5, PM10, NO2, and SO2 was associated with an increased risk of hospital admissions for total stroke and ischemic stroke. The associations were most pronounced during the concurrent hour of exposure and lasted for ≈2 hours. We found that the risk was more pronounced among male patients or those aged <65 years old.

CONCLUSIONS

Our findings suggest that exposure to PM2.5, PM10, NO2, and SO2, but not CO and O3, is associated with emergency hospital admissions for total stroke or ischemic stroke shortly after exposure. Implementing targeted pollution emission reduction measures may have significant public health implications in controlling and reducing the burden of stroke.

Effect of hyperbaric oxygen on symptoms of dementia in patients with delayed encephalopathy after acute carbon monoxide poisoning

OBJECTIVES

Delayed encephalopathy after acute carbon monoxide poisoning (DEACMP) is the most severe complication of carbon monoxide poisoning, which seriously endangers patients' quality of life. This study aims to investigate the efficacy of hyperbaric oxygen (HBO2) on improving dementia symptoms in patients with DEACMP.

METHODS

A retrospective analysis was performed on DEACMP patients, who visited Xiangya Hospital, Central South University from June 2014 to June 2020. Among them, patients who received conventional drug treatment combined with HBO2 treatment were included in an HBO2 group, while those who only received conventional drug treatment were included in a control group. HBO2 was administered once daily. Patients in the HBO2 group received 6 courses of treatment, with each course consisting of 10 sessions. The Hasegawa Dementia Scale (HDS) was used to diagnose dementia, and the Clinical Dementia Rating (CDR) was used to grade the severity of dementia for DEACMP. The Alzheimer's Disease Assessment Scale-Cognitive Section (ADAS-Cog), the Functional Activities Questionnaire (FAQ), the Neuropsychiatric Inventory (NPI), and the Clinician's Interview-Based Impression of Change-Plus Caregiver Input (CIBIC-Plus) were performed to assess cognitive function, ability to perform activities of daily living (ADL), behavioral and psychological symptoms, and overall function. The study further analyzed the results of objective examinations related to patients' dementia symptoms, including magnetic resonance imaging detection of white matter lesions and abnormal electroencephalogram (EEG). The changes of the above indicators before and after treatment, as well as the differences between the 2 groups after treatment were compared.

RESULTS

There was no significant difference in the HDS score and CDR grading between the 2 groups before treatment (both P>0.05). After treatment, the score of ADAS-Cog, FAQ, NPI, and CIBIC Plus grading of the 2 groups were significantly improved, and the improvement of the above indicators in the HBO2 group was greater than that in the control group (all P<0.05). The effective rate of the HBO2 group in treating DEACMP was significantly higher than that of the control group (89.47% vs 65.87%, P<0.05). The objective examination results (white matter lesions and abnormal EEG) showed that the recovery of patients in the HBO2 group was better than that in the control group.

CONCLUSIONS

Hyperbaric oxygen can significantly relieve the symptoms of dementia in patients with DEACMP.

The neutrophil-to-lymphocyte ratio is associated with the frequency of delayed neurologic sequelae in patients with carbon monoxide poisoning

Delayed neurologic sequelae (DNS) is a common complication in patients with carbon monoxide poisoning (COP). We aimed to investigate the association of the neutrophil-to-lymphocyte ratio (NLR) with the frequency of DNS in COP patients. A total of 371 COP patients were investigated in retrospective and prospective studies. A receiver operator curve (ROC) test was performed to evaluate the ability of the NLR to predict DNS in COP patients. The retrospective study included 288 COP patients, of whom 84 (29.2%) were confirmed to have DNS, and 1 (0.3%) died within 28 days. The NLR in the DNS group was significantly higher than that in the non-DNS group (6.84 [4.22-12.43] vs. 3.23 [1.91-5.60] × 109/L). NLR was a significant predictor of the frequency of DNS [odds ratio (OR): 1.130, 95% confidence interval (CI): 1.030, 1.240] in COP patients. The area under the ROC curve of NLR for predicting DNS was 0.766 (95% CI 0.701, 0.832), and the cut-off value was 3.745 (sensitivity, 83.3%; specificity, 58.8%). The prospective study included 83 COP patients, of whom 19 (22.9%) were confirmed to have DNS, and all patients survived. Moreover, the frequency of DNS in the patients with an NLR ≥ 3.745 was notably higher than that in the patients with an NLR < 3.745 [41.4% (12/29) vs. 13.0 (7/54)]. In conclusion, the NLR was a significant, independent predictor of the frequency of DNS in COP patients.

Carbon monoxide intoxication with a CO-Hb of 30% while smoking waterpipe: a case report

Carbon monoxide (CO) poisoning is a significant public health issue and a considerable economic burden in developed countries. While the majority of non-fire-related CO poisonings are attributed to gas heating, there are several other less recognized sources that should be considered in the initial differential diagnosis.The patient in this case was a 21-year-old who experienced a brief episode of loss of consciousness and was subsequently admitted to the Emergency department. Upon evaluation, the patient was diagnosed with CO poisoning, which necessitated hyperbaric oxygen therapy to mitigate the effects of this toxic exposure.Despite exhibiting harmful symptoms initially, the patient stated in a phone interview two and a half years post-incident that they have not experienced any enduring effects such as cardiac arrhythmia or concentration deficits. While their understanding of the risks associated with waterpipe smoking has increased, it has not influenced any major changes in their waterpipe smoking habits.

A Graph Theory Study of Resting-State Functional MRI Connectivity in Children With Carbon Monoxide Poisoning

BACKGROUND

The effect of carbon monoxide (CO) poisoning on the topology of brain functional networks is unclear, especially in children whose brains are still developing.

PURPOSE

To investigate the topological alterations of the whole-brain functional connectome in children with CO poisoning and characterize its relationship with disease severity.

STUDY TYPE

Cross-sectional and prospective study.

SUBJECTS

A total of 26 patients with CO poisoning and 26 healthy controls.

FIELD STRENGTH/SEQUENCE

A 3.0 T MRI system/echo planar imaging (EPI) and 3D brain volume imaging (BRAVO) sequences.

ASSESSMENT

We used the network-based statistics (NBS) method to explore between-group differences in functional connectivity strength and a graph-theoretical-based analytic method to explore the topology of brain networks.

STATISTICAL TESTS

Student's t-test, chi-square test, NBS, Pearson correlation coefficient, and false discovery rate correction. The statistical significance threshold was set at P < 0.05.

RESULTS

The case group's brain functional network topology was impaired in comparison to the control group (reduced global efficiency and small-worldness, increased characteristic path length). According to node and edge analyses, the case group showed topologically damaged regions in the frontal lobe and basal ganglia, as well as neuronal circuits with weaker connections. Also, there was a significant correlation between the patients' coma time and the degree (r = -0.4564), efficiency (r = -0.4625), and characteristic path length (r = 0.4383) of the nodes in the left orbital inferior frontal gyrus. Carbon monoxide hemoglobin content (COHb) concentration and right rolandic operculum node characteristic path length (r = -0.3894) were significantly correlated. The node efficiency and node degree of the right middle frontal gyrus (r = 0.4447 and 0.4539) and right pallidum (r = 0.4136 and 0.4501) significantly correlated with the MMSE score.

DATA CONCLUSION

The brain network topology of CO poisoned children is damaged, which is manifested by reduced network integration and may lead to a series of clinical symptoms in patients.

EVIDENCE LEVEL

2.

TECHNICAL EFFICACY

Stage 2.

The Associations Between Workplace Noise, Ototoxic Chemicals, and Tinnitus

OBJECTIVE

To investigate the occupational risk factors associated with tinnitus in the Australian working population.

DESIGN

The research was conducted using data collected from the Australian Workplace Exposure Survey-Hearing, a national cross-sectional study of 4970 workers conducted in 2016 to 2017. Workers were asked if they experienced tinnitus and if they answered affirmatively, they were asked about the frequency and length of the presentations. Based on their answers, each worker was categorized as having no tinnitus or any tinnitus, with an additional group of workers with any tinnitus subcategorized as having constant tinnitus. Exposure assessment was conducted using an automated expert assessment method. Exposures included daily noise (L Aeq,8h ), hand-arm vibration (A(8)), impulse noise, smoking status, styrene, trichloroethylene, toluene, n-hexane, p-xylene, ethylbenzene, lead, and carbon monoxide. Univariate and multivariate logistic regression models were used to examine the associations between workplace exposures and tinnitus.

RESULTS

Workers with an estimated noise exposure above the workplace limit (L Aeq,8h > 85 dBA) had 1.73 (95% confidence interval [CI]: 1.42 to 2.11) increased odds of any tinnitus and 2.15 (95% CI: 1.60 to 2.89) odds of constant tinnitus. The odds of workers having any tinnitus increased with increasing noise exposure levels in a dose-response relationship that strengthened when considering only those with constant tinnitus. In the fully adjusted model, statistically significant associations were seen for lead exposure with both any and constant tinnitus, toluene exposure with constant tinnitus, and carbon monoxide exposure with any tinnitus.

CONCLUSIONS

These results suggest that, in addition to workplace noise, occupational exposures to lead, toluene, and carbon monoxide are associated with tinnitus.

Metabolic Acid-Base Disorders

Metabolic acid-base disturbances are frequently encountered in the emergency department, and many of these patients are critically ill. In the evaluation of patients with these maladies, it is important for the emergency clinician to determine the cause, which can usually be elicited from a thorough history and physical examination. There are several mnemonics that can be used to form an appropriate list of potential causes. Most of the time, the management of these patients requires no specific treatment of the acid-base status but, rather, requires treatment of the underlying disorder that is causing the acid-base disturbance.

Global, regional, and national mortality due to unintentional carbon monoxide poisoning, 2000-2021: results from the Global Burden of Disease Study 2021

BACKGROUND

Unintentional carbon monoxide poisoning is a largely preventable cause of death that has received insufficient attention. We aimed to conduct a comprehensive global analysis of the demographic, temporal, and geographical patterns of fatal unintentional carbon monoxide poisoning from 2000 to 2021.

METHODS

As part of the latest Global Burden of Diseases, Injuries, and Risk Factors Study (GBD), unintentional carbon monoxide poisoning mortality was quantified using the GBD cause of death ensemble modelling strategy. Vital registration data and covariates with an epidemiological link to unintentional carbon monoxide poisoning informed the estimates of death counts and mortality rates for all locations, sexes, ages, and years included in the GBD. Years of life lost (YLLs) were estimated by multiplying deaths by remaining standard life expectancy at age of death. Population attributable fractions (PAFs) for unintentional carbon monoxide poisoning deaths due to occupational injuries and high alcohol use were estimated.

FINDINGS

In 2021, the global mortality rate due to unintentional carbon monoxide poisoning was 0·366 per 100 000 (95% uncertainty interval 0·276-0·415), with 28 900 deaths (21 700-32 800) and 1·18 million YLLs (0·886-1·35) across all ages. Nearly 70% of deaths occurred in males (20 100 [15 800-24 000]), and the 50-54-year age group had the largest number of deaths (2210 [1660-2590]). The highest mortality rate was in those aged 85 years or older with 1·96 deaths (1·38-2·32) per 100 000. Eastern Europe had the highest age-standardised mortality rate at 2·12 deaths (1·98-2·30) per 100 000. Globally, there was a 53·5% (46·2-63·7) decrease in the age-standardised mortality rate from 2000 to 2021, although this decline was not uniform across regions. The overall PAFs for occupational injuries and high alcohol use were 13·6% (11·9-16·0) and 3·5% (1·4-6·2), respectively.

INTERPRETATION

Improvements in unintentional carbon monoxide poisoning mortality rates have been inconsistent across regions and over time since 2000. Given that unintentional carbon monoxide poisoning is almost entirely preventable, policy-level interventions that lower the risk of carbon monoxide poisoning events should be prioritised, such as those that increase access to improved heating and cooking devices, reduce carbon monoxide emissions from generators, and mandate use of carbon monoxide alarms.

FUNDING

Bill & Melinda Gates Foundation.

Direct synthesis of phthalimides via palladium-catalysed double carbonylation of o-dihaloarenes with nitroarenes

The direct carbonylation of readily available nitro compounds is more attractive and straightforward than the use of traditional amines as nucleophiles. Herein, a practical palladium-catalysed double carbonylation of nitroarenes with o-dihaloarenes has been developed for the construction of various N-aryl phthalimides. Key to the success of this transformation is the use of Mo(CO)6, which acts as both a reducing agent and a solid carbonyl source. A wide range of nitroarenes and o-dihaloarenes as well as o-iodobenzoic acids reacted smoothly to give phthalimides in 27-94% yields.

The effect of full blood count and cardiac biomarkers on prognosis in carbon monoxide poisoning in children

AIMS

In this study, cardiac biomarkers, blood parameters, electrocardiography (ECG), and echocardiography were investigated in children with carbon monoxide (CO) poisoning, and the diagnostic value of these parameters was investigated.

METHODS

The demographical, clinical, and laboratory data of children aged 0-18 years who were admitted to the pediatric emergency department due to CO poisoning between January 2019 and January 2022 were retrospectively scanned from medical records. The patients were divided into two groups as troponin-I positive and troponin-I negative.

RESULTS

There were 107 children aged 0-18 years (average age, 10.46 ± 5.77 years; 51% female) with CO poisoning. There were 13 patients with troponin-I positive myocardial injury. Troponin-I was positive in 3 patients whose carboxyhemoglobin (COHb) level was below 2% at the time of admission. In one patient, troponin-I, which was normal at admission, increased by the 24th hour of hospitalization. Hyperbaric oxygen therapy was given due to headache in one patient, although the COHb level of that patient was below 25%. An NT-proBNP level of ≥ 219.5 ng/L predicted the development of troponin-I positivity with a sensitivity of 70% and a specificity of 86.7% (AUC, 0.967 (0.58-0.994); p = 0.017). White blood cell (WBC), neutrophil, neutrophil-to-lymphocyte ratio (NLR), immature granulocyte (IG), and IG% levels were found to be significantly higher in the troponin-positive patient group. DISCUSSION AND CONCLUSION: NT-proBNP has been shown to be an early diagnostic marker for myocardial dysfunction. Additionally, when cardiac markers are not available, full blood parameters may assist clinicians for patient treatment and referral.