Acute carbon monoxide poisoning and delayed neurological sequelae: a potential neuroprotection bundle therapy

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.

Correlation between Time to Hyperbaric Oxygen Therapy and Delayed Neurological Sequelae in Acute Carbon Monoxide Poisoning Patients

Carbon monoxide (CO) is one of the most common causes of intoxication. Delayed neurologic sequelae (DNS) have a major impact on prognosis of CO poisoning patients. Hyperbaric oxygen therapy (HBOT) is widely used to treat DNS. However, there is no consensus regarding the optimal timing of HBOT. This prospective study enrolled patients who visited the hospital from November 2019 to October 2022. The cutoff value for the latency to HBOT after CO exposure was determined, and the area under the receiver operating characteristic curve (AUC) was estimated. In total, 167 patients were divided into non-DNS and DNS groups. The initial Glasgow Coma Scale (GCS) score, CO exposure time, latency to HBOT after CO exposure, median length of hospital stay (p < 0.001) and creatine kinase (p = 0.016) showed significant differences. A GCS score ≤ 9 had an odds ratio (OR) of 5.059 (95% confidence interval [CI]: 1.602-15.976, p = 0.006), and latency to HBOT after CO exposure ≥ 200 min had an OR of 18.971 (95% CI: 4.310-83.508, p < 0.001). The AUC was 0.8235 (95% CI: 0.7504-0.8966). A GCS score ≤ 9 and latency to HBOT ≥ 200 min may be significant risk factors for DNS.

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.

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.

Effectiveness of Initial Troponin I and Brain Natriuretic Peptide Levels as Biomarkers for Predicting Delayed Neuropsychiatric Sequelae in Patients with CO Poisoning: A Retrospective Multicenter Observational Study

BACKGROUND

Delayed neuropsychiatric sequelae (DNS) are a severe complication of carbon monoxide (CO) poisoning, and predicting DNS is difficult. This study aimed to investigate whether cardiac markers can be used as biomarkers to predict DNS occurrence following acute CO poisoning.

METHODS

This was a retrospective observational study that included patients with acute CO poisoning who visited two emergency medical centers in Korea from January 2008 to December 2020. The primary outcome was whether the occurrence of DNS was associated with laboratory results.

RESULTS

Of the 1327 patients with CO poisoning, 967 patients were included. Troponin I and BNP were significantly higher in the DNS group. As a result of multivariate logistic regression analysis, it was found that troponin I, mentality, creatine kinase, brain natriuretic peptide, and lactate levels independently influenced DNS occurrence in CO poisoning patients. The adjusted odds ratios for DNS occurrence were 2.12 (95% CI 1.31-3.47, p = 0.002) for troponin I and 2.80 (95% CI 1.81-3.47, p < 0.001) for BNP.

CONCLUSION

Troponin I and BNP might be useful biomarkers for predicting the occurrence of DNS in patients with acute CO poisoning. This finding can help to identify high-risk patients who require close monitoring and early intervention to prevent DNS.

A patient with toxic encephalopathy associated with acute carbon monoxide poisoning–A clinical case

Carbon monoxide (CO) is a colorless, odorless, and lacking in irritative properties gas. It has a higher affinity towards hemoglobin than oxygen and thus the complex carboxyhemoglobin develops. Acute CO poisoning leads to poly-organic insufficiency and the organs that suffer the most are the ones with higher oxygen needs- the brain, the heart and the kidneys. We present a clinical case of 49-year-old woman with a sudden appearance of complaints of dizziness, stiffness throughout the entire body, inability to move. Subsequently she was found by her relatives with disorientated and “foaming around her mouth”. Earlier she had been using a gasoline generator because of a power outage. Her laboratory results came out with higher carboxyhemoglobin (40%), nitrogen waste products and mixed type acidosis. From the conducted brain MRI there were changes, correlating to toxic encephalopathy after acute CO poisoning.

Clinical significance of fractional anisotropy in cerebral white matter regional vulnerability caused by carbon monoxide poisoning: A systematic review and meta-analysis

Carbon monoxide poisoning (COP) can lead to various cerebral white matter (WM) lesions across different disease phases and clinical manifestations, and fractional anisotropy (FA) of diffusion tensor imaging has been widely applied to investigate WM injury in these patients. Here we conduct a systematic review and meta-analysis to investigate the utility of FA in evaluating the regional vulnerability of WM injury caused by COP and explore differences between different disease phases and patient subtypes. We systematically searched PubMed, Medline, Scopus and reference lists of appropriate publications to identify relevant studies. Eight studies with 217 COP patients and 207 healthy controls (HCs) were included. Eight regions of interest were available to investigate regional vulnerability. The results showed the most significant decrease in FA in orbitofrontal subcortical regions. Comparisons of different disease phases revealed lower FA in the centrum semiovale and corpus callosum in the acute phase, while in the chronic phase, only FA in the centrum semiovale remained significantly decreased. Analysis of different patient subtypes showed that the FA values in the splenium of the corpus callosum were significantly decreased in the patients with delayed neurologic sequelae (DNS) but not in the mixed population (with and without DNS). In conclusion, this meta-analysis highlights the frontal-subcortical regional vulnerability in COP. FA changes in the corpus callosum across different disease phases reflect alterations in underlying microstructures. Extended corpus callosum injury involving the splenium could be an imaging biomarker of the occurrence of DNS.

The effect of preconditioning agents on cardiotoxicity and neurotoxicity of carbon monoxide poisoning in animal studies: a systematic review

BACKGROUND

Carbon monoxide (CO) poisoning is a common intoxication and many people die yearly due to CO poisoning and preconditioning agents attenuate brain and cardiac injury caused by intoxication. It is critical to fully understand the efficacy of new methods to directly target the toxic effect of CO, such as conditioning agents, which are currently under development. This study aims to systematically investigate current evidence from animal experiments and the effects of administration preconditions in acute and late phases after CO poisoning on cardiotoxicity and neurotoxicity.

METHODS

Four databases (PubMed, Embase, Scopus, and Web of Science) were systematically searched without language restrictions, and hand searching was conducted until November 2021. We included studies that compare preconditioning agents with the control group after CO poisoning in animals. The SYRCLE RoB tool was used for risk of bias assessments.

RESULTS

Thirty-seven studies were included in the study. Erythropoietin, granulocyte colony-stimulating factor (GCSF), hydrogen-rich saline, and N-butylphthalide (NBP) were found to have positive effects on reducing neurotoxicity and cardiotoxicity. As other preconditions have fewer studies, no valuable results can be deduced. Most of the studies were unclear for sources of bias.

DISCUSSION

Administration of the examined preconditioning agents including NBP, hydrogen-rich saline, and GCSF in acute and late phases could attenuate neurotoxicity and cardiotoxicity of CO poisoned animals. For a better understanding of mechanisms and activities, and finding new and effective preconditioning agents, further preclinical and clinical studies should be performed to analyze the effects of preconditioning agents.

Effect of Carbon Monoxide Poisoning on Epilepsy Development: A Nationwide Population-Based Cohort Study

STUDY OBJECTIVE

Carbon monoxide (CO) poisoning causes central nervous system toxicity resulting in delayed neurologic sequelae. This study aims to evaluate the risk of epilepsy in patients with a history of CO intoxication.

METHODS

We conducted a retrospective population-based cohort study using the Taiwan National Health Insurance Research Database and enrolled patients with and without CO poisoning matched for age, sex, and index year in a 1:5 ratio, between 2000 and 2010. Multivariable survival models were used to assess the risk of epilepsy. The primary outcome was newly developed epilepsy after the index date. All patients were followed until a new diagnosis of epilepsy, death, or December 31, 2013. Stratification analyses by age and sex were also conducted.

RESULTS

This study included 8,264 patients with CO poisoning and 41,320 without. Patients with a history of CO poisoning were strongly associated with subsequent epilepsy (adjusted hazard ratio [HR] 8.40; 95% confidence interval [CI], 6.48 to 10.88). In the age-stratified analysis, intoxicated patients aged 20 to 39 years had the highest HR (adjusted HR 11.06; 95% CI, 7.17 to 17.08). In the sex-stratified analysis, adjusted HRs for male and female patients were 8.00 (95% CI, 5.86 to 10.92) and 9.53 (95% CI, 5.95 to 15.26), respectively.

CONCLUSION

Patients with CO poisoning were associated with an increased risk of developing epilepsy compared with those without CO poisoning. This association was more prominent in the young population.

Dexamethasone therapy prevents delayed neuropsychiatric sequelae after carbon monoxide poisoning: a prospective registry-based study

BACKGROUND

Delayed neuropsychiatric sequelae are major complications of carbon monoxide poisoning; carbon monoxide triggers brain oxidation and inflammation. Corticosteroids such as dexamethasone modulate neurological damage after carbon monoxide poisoning through anti-inflammatory actions and immune response inhibition. However, it is not known whether corticosteroids prevent delayed neuropsychiatric sequelae. We thus studied whether dexamethasone reduced the incidence of delayed neuropsychiatric sequelae.

METHODS

This registry-based study enrolled patients with carbon monoxide poisoning treated in a Korean tertiary care hospital from March 1^st, 2020 to November 30^th, 2021. Data of patients were prospectively collected during the study period, and retrospectively analyzed. One group received intravenous dexamethasone. We performed multivariable logistic regression analysis to identify factors associated with delayed neuropsychiatric sequelae.

RESULTS

A total of 128 patients were enrolled, of which 99 patients received dexamethasone therapy and 29 patients did not. The incidences of delayed neuropsychiatric sequelae in the dexamethasone and non-dexamethasone groups were 16.2% and 37.9%, respectively. Multivariable logistic regression analysis revealed that dexamethasone use (odds ratio = 0.122, 95% confidence interval 0.031-0.489) and a higher Glasgow Coma Scale (odds ratio = 0.818, 95% confidence interval 0.682-0.981) was associated with a lower incidence of delayed neuropsychiatric sequelae.

CONCLUSION

Early dexamethasone treatment was significantly associated with a decreased incidence of delayed neuropsychiatric sequelae. A higher Glasgow Coma Scale at presentation also was associated with a lower incidence of delayed neuropsychiatric sequelae.

Toxin Induced Parkinsonism and Hospitalization Related Adverse Outcome Mitigation for Parkinson's Disease: A Comprehensive Review

Patients with Parkinson's disease admitted to the hospital have unique presentations. This unique subset of patients requires a multidisciplinary approach with a knowledge-based care team that can demonstrate awareness of complications specific to Parkinson's disease to reduce critical care admissions, morbidity, and mortality. Early recognition of toxic exposures, medication withdrawals, or medication-induced symptoms can reduce morbidity and mortality. This review can assist in the critical assessment of new or exacerbating Parkinson's disease symptoms.

Effects of Daily Peat Smoke Exposure on Present and Next Generations

This study aimed to follow the neurotoxic effect of peat smoke on adult outbred rats and its influence on central nervous system (CNS) parameters in first-generation offspring. Under experimental conditions, exposure to peat smoke was carried out on adult male Wistar rats for 24 h. After the end of the exposure, an open field test (OFT), electroencephalography (EEG), and histological analysis of the testes and brains of smoke-exposed males were performed, after which they were mated with intact females to obtain F1 offspring. Stillbirth, neonatal mortality, and body weight at 4, 7, 14, and 21 postnatal days, as well as behavior in the OFT and EEG parameters during puberty (3 months), were assessed. The results of the examination of F0 males showed a significant increase in motor activity and anxiety in the open field test and a violation of EEG parameters. Histopathologically, peat smoke caused a sharp increase in shadow cells (homogeneous cells with pale-stained cytoplasm, in which the cell and nuclear membranes are not visualized) and degeneratively altered neurons in the brain; we found no changes in the testicles. Peat smoke exposure during preconception did not affect neonatal mortality and weight gain in F1 offspring. Adult females born to peat-smoke-exposed males showed an increase in locomotor activity, and the behavior of adult F1 males did not differ from the control. In F1 males, a statistically significant increase in slow-wave activity indices in the delta band was observed.

Multi-Modal Synergistic 99mTc-TRODAT-1 SPECT and MRI for Evaluation of the Efficacy of Hyperbaric Oxygen Therapy in CO-Induced Delayed Parkinsonian and Non-Parkinsonian Syndromes

Background: Delayed neuropsychiatric syndrome (DNS) is characterized by motor dysfunction after acute carbon monoxide (CO) poisoning. We examined the relationship between dopamine transporter (DAT) loss using kit-based Tc-99m-TRODAT-1 (DAT single-photon emission-computed tomography (SPECT) radioligand) and globus pallidus necrosis on MRI, DAT availability before and after hyperbaric oxygen therapy (HBOT), and feasibility of Tc-99m-TRODAT-1 as an index for parkinsonian syndrome in CO poisoning. Methods: Twenty-one CO-intoxicated patients (mean ± SD age, 38.6 ± 11.4; range, 20−68 years) with DNS underwent Tc-99m-TRODAT-1 SPECT and MRI before HBOT and follow-up Tc-99m-TRODAT-1 SPECT to assess DAT recovery. Neurological examinations for Parkinsonism were performed after development of DNS. Results: Over 70% (15/21) of DNS patients showed globus pallidus necrosis on MRI. Significantly lower bilateral striatal DAT availability was associated with globus pallidus necrosis (p < 0.005). Moreover, 68.4% (13/19) of DNS subjects with Parkinsonian syndrome had lower bilateral striatal DAT availability vs. non-parkinsonian subjects pre- or post-HBOT. The SURs for both striata increased by ~11% post-HBOT in the Parkinsonian group; however, the left striatum presented a significantly higher DAT recovery rate than the right (*** p < 0.005). Conclusions: Coupled Tc-99m TRODAT-1 SPECT and MRI could assist evaluation of Parkinsonism risk and indicate DAT availability after HBOT in CO-poisoned patients with DNS.

Case report: Recovery of hallucinations and cognitive impairment after administration of donepezil in a patient with schizophrenia and carbon monoxide poisoning

OBJECTIVES

This report aims to introduce a rare case of a dramatic recovery by donepezil with a patient with schizophrenia who suffered from remaining psychotic symptoms despite proper treatment and had a cognitive impairment by carbon monoxide (CO) poisoning sequelae.

CASE REPORT

A 38-year-old male who developed schizophrenia 2 years ago had attempted suicide via CO inhalation due to his uncontrolled symptoms. He was hospitalized with delayed neurological sequelae (DNS). Though hyperbaric oxygen therapy (HBOT) was applied 10 times, his cognitive impairment did not recover. Surprisingly, with 5-10 mg donepezil, both cognitive function and the psychotic symptoms of the patient remarkably improved.

CONCLUSION

This case showed a good response of donepezil for a patient with schizophrenia and CO-induced DNS after ineffective HBOT. Although the mechanism of the phenomenon is unclear, it can be possible reasons that the neuroprotective effect of donepezil and white matter insult by CO poisoning.

Extracorporeal Hyperoxygenation Therapy (EHT) for Carbon Monoxide Poisoning: In-Vitro Proof of Principle

Carbon monoxide (CO) poisoning is the leading cause of poisoning-related deaths globally. The currently available therapy options are normobaric oxygen (NBO) and hyperbaric oxygen (HBO). While NBO lacks in efficacy, HBO is not available in all areas and countries. We present a novel method, extracorporeal hyperoxygenation therapy (EHT), for the treatment of CO poisoning that eliminates the CO by treating blood extracorporeally at elevated oxygen partial pressure. In this study, we proof the principle of the method in vitro using procine blood: Firstly, we investigated the difference in the CO elimination of a hollow fibre membrane oxygenator and a specifically designed batch oxygenator based on the bubble oxygenator principle at elevated pressures (1, 3 bar). Secondly, the batch oxygenator was redesigned and tested for a broader range of pressures (1, 3, 5, 7 bar) and temperatures (23, 30, 37 °C). So far, the shortest measured carboxyhemoglobin half-life in the blood was 21.32 min. In conclusion, EHT has the potential to provide an easily available and effective method for the treatment of CO poisoning.

Alterations in CNS Functions and DNA Methylation in Rats after 24 h Exposure to Peat Smoke

The use of a developed experimental model of a natural fire made it possible to assess the consequences of 24 h exposure to peat combustion products in albino rats. Peat smoke exposure leads to behavioral disturbances in rats, characterized by an increase in locomotor activity and an increased level of anxiety. Indicators of brain bioelectrical activity of the exposed animals supported the state of anxiety and psychoemotional stress. Epigenetic changes in the blood cells of exposed animals were revealed under 24 h exposure to peat smoke, characterized by a decrease in the level of global DNA methylation.

Prediction of delayed neuropsychiatric sequelae after carbon monoxide poisoning via serial determination of serum neuron-specific enolase levels

BACKGROUND

Neuron-specific enolase (NSE) is released into serum when nerve cells are damaged, and the levels thereof are used to determine neurological prognosis in patients who have suffered cardiac arrest or stroke. Delayed neuropsychiatric sequelae (DNS), a major complication of carbon monoxide poisoning (COP), can be caused by inflammatory response which is a mechanism of neuronal injury in cardiac arrest and stroke. NSE is known as a predictor of neurological prognosis in ischemic brain injury after cardiac arrest, and it is also reported as a predictor of DNS in acute COP. When serum NSE is measured serially in cardiac arrest patients, the best time to predict neurological prognosis is known at 48-72 h, but there are no studies analyzing serial serum NSE in acute COP. Thus, we explored whether serum NSE levels measured three times at 24 h intervals after COP predicted the development of DNS.

METHODS

This prospective observational study was conducted on patients treated for COP from May 2018 to April 2020 in a tertiary care hospital in Korea. Neuron-specific enolase levels were assessed 24, 48, and 72 h after presentation at hospital. We used logistic regression to explore the association between NSE levels and DNS development.

RESULTS

The NSE level was highest at 48 h, and the difference between the DNS group and the non-DNS group was greatest on the same time point. On multivariable logistic regression analysis, the NSE level at 48 h of >20.98 ng/mL (odds ratio [OR], 3.570; 95% confidence interval [CI], 1.412-9.026; P = .007) and the initial Glasgow Coma Scale (GCS) score of <9 (OR, 4.559; 95% CI, 1.658-0.12.540; P = .003) was statistically significant for DNS development.

CONCLUSION

Early identification of those who will experience DNS in acute COP patients is clinically important for deciding treatment. In this study, we revealed that NSE level of >20.98 ng/mL at 48 h time point can be used as an independent predictor of DNS (OR, 3.570; 95% CI, 1.412-9.026; P = .007; AUC, 0.648).

Incidence patterns of nervous system diseases after carbon monoxide poisoning: a retrospective longitudinal study in South Korea from 2012 to 2018

Objective

To analyze the incidence patterns of nervous system diseases in survivors of carbon monoxide (CO) poisoning using nationwide claims data from South Korea.

Methods

A national cohort was abstracted from a database that includes patients diagnosed with CO poisoning between January 2012 and December 2018. For all nervous system diseases, we investigated the frequency, pattern of incidence, effect of intensive care unit admission, and the standardized incidence ratios (SIRs) to estimate the risk of nervous system disease after CO poisoning.

Results

Of 26,778 patients, 18,720 (69.9%) were diagnosed with nervous system diseases after CO poisoning. The most common disease was disorders of sleep initiation and maintenance (n=701, 3.74%), followed by tension-type headache (n=477, 2.55%) and anoxic brain injury (n=406, 2.17%). Over half of the nervous system diseases occurred within the first year after CO poisoning. The cumulative hazard ratio for nervous system diseases in patients admitted to the intensive care unit was 2.25 (95% confidence interval [CI], 2.07–2.44). Among the frequent nervous system diseases after CO poisoning, patients had a higher risk of disorders of initiating and maintaining sleep (SIR, 1.61; 95% CI, 1.52–1.71), tension-type headache (SIR, 2.41; 95% CI, 2.23–2.61), anoxic brain injury (SIR, 58.76; 95% CI, 53.95–63.88), and post-zoster neuralgia (SIR, 1.94; 95% CI, 1.70–2.20).

Conclusion

Patients who experience CO poisoning are at higher risk for several nervous system diseases. Therefore, monitoring for specific nervous system diseases is important after CO poisoning within the first year.

Effects of smoking on delayed neuropsychiatric sequelae in acute carbon monoxide poisoning: A prospective observational study

Smoking is a well-known risk factor for cardio-cerebrovascular disease. However, several studies have reported the "smoker's paradox" whereby smokers have a better prognosis for cardio-cerebrovascular diseases. Similar to cardio-cerebrovascular diseases, hypoxia is one of the major mechanisms of injury in carbon monoxide (CO) poisoning. This study investigated the association between smoking and delayed neuropsychiatric sequelae (DNS) in acute CO poisoning.This study involved patients with CO poisoning treated at a university hospital in Bucheon, Korea between September 2017 and March 2020. The exclusion criteria were age <18 years, discharge against medical advice, loss to follow-up, persistent neurological symptoms at discharge, transfer from another hospital 24 hours after exposure, and transfer from another hospital after hyperbaric oxygen therapy. Logistic regression analysis was performed to find factors associated with DNS.Two hundred sixty three patients visited the hospital due to CO poisoning and of these, 54 were excluded. DNS was evaluated up to 3 months after discharge, and until this time, DNS occurred in 35 (16.8%) patients. And the incidence rate of DNS was lower in smokers than non-smokers (15, 12% vs 20, 23.8%, P = .040). Multivariable logistic regression analysis revealed that CO exposure time (odds ratio [OR] 1.003; confidence interval [CI] 1.001-1.005; P = .003), the Glasgow coma scale (GCS) (OR 0.862; CI 0.778-0.956; P = .005), and pack-years (OR 0.947; CI 0.903-0.993; P = .023) were statistically significant for DNS development.These results indicate that more pack-years smoked were associated with reduced risk of the development of DNS in acute CO poisoning, and that CO exposure time and GCS is a predictive factor for DNS occurrence.

Sensitive quantification of carbon monoxide in vivo reveals a protective role of circulating hemoglobin in CO intoxication

Carbon monoxide (CO) is a gaseous molecule known as the silent killer. It is widely believed that an increase in blood carboxyhemoglobin (CO-Hb) is the best biomarker to define CO intoxication, while the fact that CO accumulation in tissues is the most likely direct cause of mortality is less investigated. There is no reliable method other than gas chromatography to accurately determine CO content in tissues. Here we report the properties and usage of hemoCD1, a synthetic supramolecular compound composed of an iron(II)porphyrin and a cyclodextrin dimer, as an accessible reagent for a simple colorimetric assay to quantify CO in biological samples. The assay was validated in various organ tissues collected from rats under normal conditions and after exposure to CO. The kinetic profile of CO in blood and tissues after CO treatment suggested that CO accumulation in tissues is prevented by circulating Hb, revealing a protective role of Hb in CO intoxication. Furthermore, hemoCD1 was used in vivo as a CO removal agent, showing that it acts as an effective adjuvant to O₂ ventilation to eliminate residual CO accumulated in organs, including the brain. These findings open new therapeutic perspectives to counteract the toxicity associated with CO poisoning.

Mao et al. report highly sensitive quantification of carbon monoxide with a simple colorimetric assay, exploiting a synthetic supramolecular compound, hemoCD1. It can reveal distribution of CO in organs including the brain and can also serve as a CO scavenger for residual CO accumulated in organs. Finally, the authors showed circulating hemoglobin plays a protective role in CO intoxication.

The predictive value of neutrophil-lymphocyte ratio at presentation for delayed neurological sequelae in carbon monoxide poisoning

OBJECTIVE

To explore the predictive value of neutrophil-lymphocyte ratio (NLR) at presentation for delayed neurological sequelae (DNS) in carbon monoxide (CO) poisoning.

METHODS

This single-center retrospective observational study included a total of 253 consecutive patients who visited the emergency department (ED) due to acute CO intoxication between 7 October 2015 and 31 December 2019. The included patients had a history of coma and their blood routine was measured within one hour of ED admission. They were divided into two groups according to the presence of DNS, including those who developed DNS (DNS group) and those who did not (non-DNS group).

RESULTS

A total of 171 patients were included in this research, and 49 (28.7%) developed DNS. The median NLR at ED admission was obviously higher in the DNS group (10.60 [9.69-15.34]) than in the non-DNS group (7.53 [5.86-8.56]) (p < 0.001). Multivariate analysis indicated that a high NLR (adjusted odds ratio (AOR): 1.78, 95% confidence interval (CI): 1.46-2.18) and the occurrence of acute brain lesions (AOR: 7.50, 95%CI: 2.86-19.68) on diffusion-weighted imaging were independent predictors of DNS. The NLR was more than 8.97. The prediction of occurrence of DNS had a sensitivity of 93.88% and a specificity of 84.43%. Kappa value was 0.713. The predicted results showed good authenticity and consistency.

CONCLUSION

The level of NLR at presentation had good predictive value for the development of DNS, showing the superior value for clinical application.

Carbon monoxide-triggered health effects: the important role of the inflammasome and its possible crosstalk with autophagy and exosomes

Carbon monoxide (CO) has long been known as a "silent killer" because of its ability to bind hemoglobin (Hb), leading to reduced oxygen carrying capacity of Hb, which is the main cause of CO poisoning (COP) in humans. Emerging studies suggest that mitochondria is a key target of CO action that can impact key biological processes, including apoptosis, cellular proliferation, inflammation, and autophagy. Despite its toxicity at high concentrations, CO also exhibits cyto- and tissue-protective effects at low concentrations in animal models of organ injury and disease. Specifically, CO modulates the production of pro- or anti-inflammatory cytokines and mediators by regulating the NLRP3 inflammasome. Given that human diseases are strongly associated with inflammation, a deep understanding of the exact mechanism is helpful for treatment. Autophagic factors and inflammasomes interact in various situations, including inflammatory disease, and exosomes might function as the bridge between the inflammasome and autophagy activation. Thus, the interplay among autophagy, mitochondrial dysfunction, exosomes, and the inflammasome may play pivotal roles in the health effects of CO. In this review, we summarize the latest research on the beneficial and toxic effects of CO and their underlying mechanisms, focusing on the important role of the inflammasome and its possible crosstalk with autophagy and exosomes. This knowledge may lead to the development of new therapies for inflammation-related diseases and is essential for the development of new therapeutic strategies and biomarkers of COP.

Effect of ethanol in carbon monoxide poisoning and delayed neurologic sequelae: A prospective observational study

Objectives

Carbon monoxide (CO) is one of the most common poisoning substances, which causes mortality and morbidity worldwide. Delayed neurologic sequelae (DNS) have been reported to occur from several days to months after exposure to CO. Thus, there is a need for prevention, recognition, and treatment of DNS. Patients with CO poisoning as a component of intentional suicide often also consume ethanol, but there is debate regarding its role in DNS. We explored whether ethanol has a neuroprotective effect in CO poisoning.

Methods

This prospective observational study included patients who visited the emergency department from August 2016 to August 2019 due to CO poisoning. After treatment of acute CO poisoning, patients were interviewed by telephone to ascertain whether DNS had occurred within 2 weeks, 1 month, and 3 months from the time of CO exposure.

Results

During the study period, 171 patients were enrolled. 28 patients (16.37%) developed DNS. The initial Glasgow Coma Scale (GCS) scores were 15 (10.5–15) for the non-DNS group and 10 (7–15) for the DNS group (p = 0.002). The ethanol levels were 11.01 ± 17.58 mg/dL and 1.49 ± 2.63 mg/dL for each group (p < 0.001). In multivariate logistic regression analysis, the GCS score had an odds ratio of 0.770 (p < 0.001) and the ethanol level had 0.882 (p < 0.030) for onset of DNS.

Conclusions

Higher ethanol level and higher initial GCS score were associated with lower incidence of DNS. Ethanol could have a neuroprotective effect on the occurrence of DNS in CO poisoning patients.

Hyperbaric Oxygen Therapy Did Not Prevent Delayed Neuropsychiatric Sequelae in a Prospective Observational Study With Propensity Score Matching in 224 Patients With Acute Carbon Monoxide Toxicity

BACKGROUND

It is important to prevent the development of delayed neuropsychiatric sequelae (DNS) in acute carbon monoxide (CO) intoxication, but no effective treatment has been clearly identified. Hyperbaric oxygen (HBO) therapy is one of the treatment options in acute CO poisoning; however, whether it can prevent the development of DNS is controversial.

OBJECTIVES

The purpose of this study is to compare the effectiveness of normobaric oxygen (NBO) and HBO in preventing DNS.

METHODS

This prospective observational study was conducted on all patients with CO poisoning admitted to the emergency department of a tertiary hospital from 2016 to 2019. We followed-up patients to determine whether symptoms of DNS occurred at ≤6 months. We matched the propensity score to an equivalent distribution of potential covariates.

RESULTS

A total of 224 patients with CO poisoning were enrolled in this study. NBO was used for 26 patients and HBO for 198 patients. DNS occurred in 40 patients. There were significant differences between the NBO and HBO groups in terms of carboxyhemoglobin, loss of consciousness, dizziness, chest pain, hospitalization, and length of hospital stay. The incidence of DNS was 19.2% in the HBO group, which was higher than the 7.7% observed in the NBO group, but the difference was not significant (p = 0.18). After propensity score matching, the incidence of DNS did not differ between the NBO and HBO groups (8.3% vs. 10.4%, p > 0.99).

CONCLUSION

There was no difference in the incidence of DNS between groups receiving HBO and NBO in acute CO intoxication.

Stroke Incidence in Survivors of Carbon Monoxide Poisoning in South Korea: A Population-Based Longitudinal Study

Background

Carbon monoxide (CO) poisoning is a suspected risk factor for stroke. However, the association between stroke occurrence and carbon monoxide poisoning remains unclear. This nationwide study in Korea analyzed the incidence of stroke in survivors of CO poisoning.

Material/Methods

In this nationwide, population-based longitudinal study, the database of the Health Insurance Review and Assessment Service was searched to identify patients diagnosed with CO poisoning from 2012 to 2018. Their incidence of ischemic and hemorrhagic strokes, the patterns of stroke incidences, the annual incidence rates in sequential time, the standardized incidence ratio (SIR), and the effects of hyperbaric oxygen therapy (HBOT) were analyzed.

Results

Of the 29 301 patients diagnosed with CO poisoning during the study period, 984 (3.36%) were diagnosed with stroke after CO poisoning, with approximately 50% occurring within 1 year after CO poisoning. The overall SIR for stroke was 19.49 (95% confidence interval [CI], 17.92–21.12) during the first year, decreasing to 5.64 (95% CI, 4.75–6.66) during the second year. Overall stroke hazard ratio (HR) in the patients admitted to the ICU for CO poisoning was 2.28 (95% CI, 1.19–2.27), compared with 2.35 (95% CI, 1.94–2.84) for ischemic stroke and 1.76 (95% CI, 1.11–2.78) for hemorrhagic stroke. Cumulative HRs did not differ between patients who were and were not treated with HBOT for stroke.

Conclusions

CO poisoning is a high-risk factor for the development of stroke, evidenced by high incidences of stroke after CO poisoning. Practical strategies for preventing stroke after CO poisoning are needed, because stroke after CO poisoning affects adults of almost all ages, significantly increasing their socioeconomic burden.

Cerebral White Matter Lesions on Diffusion-Weighted Images and Delayed Neurological Sequelae after Carbon Monoxide Poisoning: A Prospective Observational Study

Introduction: Carbon monoxide (CO) poisoning can result in delayed neurological sequelae (DNS). Factors predicting DNS are still controversial. This study aims to determine whether acute brain lesions observed using diffusion-weighted magnetic resonance imaging (MRI) following acute CO poisoning are related to the subsequent development of DNS. Methods: This prospective study was conducted on patients with CO poisoning treated at a university hospital in Bucheon, Korea. From August 2016 to July 2019, a total of 283 patients visited the hospital because of CO poisoning. Exclusion criteria included age under 18 years, refusing hyperbaric oxygen therapy, refusing MRI, being discharged against medical advice, being lost to follow-up, having persistent neurological symptoms at discharge, and being transferred from another hospital 24 h after exposure. Results: Of the 154 patients included in the final study, acute brain lesions on MRI (ABLM) were observed in 49 patients (31.8%) and DNS occurred in 30 patients (19.5%). In a logistic regression analysis, lower Glasgow coma scale score and higher exposure time were associated with DNS, and the presence of ABLM in white matter was significantly associated with DNS (OR 6.741; 95% CI, 1.843–24.660; p = 0.004). Conclusion: The presence of ABLM in white matter was significantly related to the occurrence of DNS. Early prediction of the risk of developing DNS through MRI may be helpful in treating patients with CO poisoning.

Assessment of serum glucose/potassium ratio as a predictor for delayed neuropsychiatric syndrome of carbon monoxide poisoning

INTRODUCTION

Carbon monoxide (CO) poisoning is a crucial cause of delayed neuropsychiatric syndrome (DNS). However, most biomarkers are not satisfactory for the prediction of DNS caused by CO poisoning. Thus, we evaluated the adequacy of the serum glucose/potassium (GLU/K) ratio, which may be an easy, quick, and readily available parameter that can be used in the emergency department for predicting DNS.

METHODS

We evaluated 281 patients who were admitted to our emergency department between January 2012 and December 2018. The patients were divided into two groups: DNS (+) and DNS (-). The GLU/K was compared for the groups.

RESULTS

Glucose, blood urea nitrogen, carboxyhemoglobin, and GLU/K ratios of patients in the DNS (+) group were statistically significantly higher than those patients in DNS (-) group (140 ± 34 vs. 110 ± 24, p < 0.001; 17.58 ± 6.14 vs. 14.27 ± 5.08, p = 0.003; 29 ± 5.1 vs. 18.9 ± 7.6, p < 0.001; and 38.35 ± 10.11 vs. 28.65 ± 6.53, p < 0.001, respectively). The area under the curve for GLU/K to predict DNS was measured as 0.791, and 35.9 as a cut-off value had 63.6% sensitivity and 89.6% specificity.

CONCLUSIONS

DNS development in CO poisoning is a serious and feared complication. We suggest that the GLU/K ratio has a high potential as a rapid, easy preliminary marker for the exclusion of patients who will not subsequently develop DNS.

Predictive factors for acute brain lesions on magnetic resonance imaging in acute carbon monoxide poisoning

BACKGROUND

Acute brain lesions on diffusion-weighted-magnetic resonance imaging (MRI) after acute carbon monoxide (CO) poisoning were associated with delayed neurological sequelae. This study was conducted to identify the risk factors associated with acute brain lesions on MRI after acute CO poisoning and to help select patients who need acute-phase brain MRI after acute CO poisoning in the emergency department (ED).

METHODS

This retrospective observational study included 103 adult patients who were hospitalized at a tertiary-care hospital between November 2016 and September 2019 and underwent brain MRI because of acute CO poisoning. Multivariable logistic regression analysis was applied to identify predictive factors for acute brain lesions on MRI after acute CO poisoning.

RESULTS

Multivariable logistic regression analysis showed that Glasgow Coma Scale (GCS) score of <9 at ED presentation (odds ratio [OR] 17.749, 95% confidence interval [CI] 3.098-101.690, P = 0.001) and the initial troponin-I level at presentation in the ED (OR 13.657, 95% CI 1.415-131.834, P = 0.024) were predictive factors for acute brain lesions on MRI in acute CO poisoning. The receiver operating characteristics curve for initial troponin-I showed an area under the curve of 0.761 (95% CI 0.638-0.883, P < 0.001) and the optimal cutoff value was 0.105 ng/mL.

CONCLUSIONS

Acute-phase brain MRI in acute CO poisoning can be considered for patients who present at the ED with a GCS score <9 or troponin-I level >0.105 ng/mL.

Cardiac injury after acute carbon monoxide poisoning and its clinical treatment scheme

This study was designed to investigate cardiac injury after acute carbon monoxide poisoning and its clinical treatment scheme. Seventy patients with moderate and severe acute carbon monoxide poisoning (ACOP) admitted from January 2017 to December 2018 into The Affiliated Hospital of Qingdao University were regarded as a research group (RG), and another 30 healthy adults undergoing physical examination in the hospital during the same period were selected as a control group (CG). Thirty-five patients in the RG who received hyperbaric oxygen therapy were considered as group A, and 35 patients who received extracorporeal membrane oxygenation therapy were considered as group B. The effective rates and complications of the two groups after treatment were compared. The concentrations of creatine kinase isoenzyme (CK-MB) and lactate dehydrogenase (LDH) of myocardial enzymes at different time points before and after treatment were detected. Expression of miR-30a in the blood of experimental subjects was detected by time-fluorescence quantitative PCR, and the relationship between miR-30a expression and ACOP patients was analyzed. Patients in groups A and B achieved obvious efficacy, but the effective rate and incidence rate of complications in the extracorporeal membrane oxygenation (ECMO) group were better than those in the hyperbaric oxygen group. The concentrations of CK-MB and LDH in group A and group B were significantly higher than those in control group (P<0.01). The expression level of miR-30a in the RG was significantly higher than that in the control group (P<0.05). Both hyperbaric oxygen therapy and ECMO therapy have obvious efficacy on ACOP patients, but the latter is better than the former. The expression level of miR-30a in blood of ACOP patients increased significantly, which is positively correlated with myocardial injury, and it decreased after treatment. It is believed that miR-30a can provide a reference index for early diagnosis and prediction of disease progression and prognosis in cardiac injury of ACOP.

S-100β in predicting the need of hyperbaric oxygen in CO-induced delayed neurological sequels

BACKGROUND

Delayed neurological sequels (DNS) have been described after carbon monoxide (CO) poisoning. There is a need to find a new prognostic marker to guide the use of hyperbaric oxygen (HBO) therapy.

AIM

To evaluate serum S-100β level in patients presenting with acute CO poisoning as an indicator of poisoning severity and predictor of DNS occurrence and HBO need in those patients.

METHODS

This prospective cohort study included patients with acute CO poisoning. On admission, carboxyhemoglobin (COHb) and S-100β levels were measured. Patients were followed up for 6 months for signs of DNS.

RESULTS

Out of 50 patients, 6 only developed DNS. The mean of S-100β levels was significantly higher in patients with severe poisoning and those with DNS. Receiver operating characteristic curve analysis revealed that S-100β had an area under the curve 0. 871; at a cutoff value ≥ 0.67 µg/L, its sensitivity and specificity were 100% and 77.3%, respectively. The sensitivity of S-100β was significantly higher than that of COHb, while its specificity and overall accuracy were significantly higher than those of HBO criteria.

CONCLUSION

Serum S-100β level on admission could be a marker of poisoning severity and a predictor of CO-induced DNS development that guides the use of HBO therapy.

Demographic characteristics and delayed neurological sequelae risk factors in carbon monoxide poisoning

AIM

Carbon monoxide (CO) is a colorless, odorless gas and tasteless. CO poisoning (COP) is one of the most frequently encountered inhalation poisonings. The most common cause of morbidity in COP is delayed neurological sequelae (DNS). DNS is the occurrence of neuropsychiatric findings within 2-240 days after discharge of patients with COP and there are no definitive diagnostic criteria. The aim of our study is; to determine the risk factors and incidence of DNS.

METHOD

Our study is a retrospective, observational study. Patients with the diagnosis of COP in the emergency department between 2015 and 2016 were included in the study. Patients age, gender, findings in the initial physical examination (PE) and neurological examination (NE), blood carboxyhemoglobin (COHb) level, relation between hyperbaric oxygen (HBO) treatment and DNS were assessed.

RESULTS

Total of 72 patients were included in the study. Mean age was 33.43 ± 20.89. It was determined that pathological findings in the initial NE are a significant predictive factor for DNS (Odds ratio 18.600, p:0.004). Significant relation between NE and HBO treatment was present (p:00.1). There was no statistically significant relationship between initial COHb level and receiving HBO treatment (p:0.9). Median COHb level of patients with DNS was 30 (min:10, max: 43), median COHb level of patients without DNS was 25 (min:10, max:44) and there was no statistically significant relationship between the two groups according to COHb levels (p:0.7).

CONCLUSION

Pathological findings in the initial neurological examination had a predictive value for delayed neurological sequelae in patients with carbon monoxide poisoning.

Acute Brain Lesions on Magnetic Resonance Imaging and Delayed Neurological Sequelae in Carbon Monoxide Poisoning

Importance

Preventing delayed neurological sequelae is a major goal of treating acute carbon monoxide poisoning, but to our knowledge there are no reliable tools for assessing the probability of these sequelae.

Objectives

To determine whether acute brain lesions on diffusion-weighted imaging are related to subsequent development of delayed neurological sequelae after acute carbon monoxide poisoning.

Design, Setting, and Participants

This registry-based observational study was conducted at a university hospital in Seoul, Korea, between April 1, 2011, and December 31, 2015. Of 700 patients (aged ≥18 years) with acute carbon monoxide poisoning, 433 patients (61.9%) who underwent diffusion-weighted imaging at an emergency department were considered for the study. Patients who developed cardiac arrest before diffusion-weighted imaging (n = 3), had persistent neurological symptoms at discharge (n = 8), committed suicide soon after discharge (n = 1), and were lost to follow-up (n = 34) were excluded.

Exposure

The presence of unambiguous, high-signal-intensity, acute brain lesions on diffusion-weighted imaging (b = 1000 s/mm2).

Main Outcomes and Measures

Development of delayed neurological sequelae defined as any neurological symptoms or signs that newly developed within 6 weeks of discharge.

Results

Of the 387 included patients (143 women [37.0%]; median age, 42.0 years [interquartile range, 32.0-56.0 years]), acute brain lesions on diffusion-weighted imaging were observed in 104 patients (26.9%). Among these, 77 patients (19.9%) had globus pallidus lesions, 13 (3.4%) had diffuse lesions, and 57 (14.7%) had focal lesions (37 patients [9.6%] had >1 pattern concurrently). Lesions were supratentorial and infratentorial in 101 and 23 patients, respectively. Delayed neurological sequelae occurred in 101 patients (26.1%). Multivariable logistic regression analysis indicated that the presence of acute brain lesions was independently associated with development of delayed neurological sequelae (adjusted odds ratio, 13.93; 95% CI, 7.16-27.11; P < .001). The sensitivity and specificity of acute brain lesions to assess the probability of delayed neurological sequelae were 75.2% (95% CI, 66.8%-83.7%) and 90.2% (95% CI, 86.8%-93.7%), respectively. In addition, the positive and negative predictive values were 73.1% (95% CI, 64.6%-81.6%) and 91.2% (95% CI, 87.9%-94.5%), respectively.

Conclusions and Relevance

The presence of acute brain lesions was significantly associated with the development of delayed neurological sequelae. Diffusion-weighted imaging during the acute phase of carbon monoxide poisoning may therefore help identify patients at risk of developing these debilitating sequelae.

Carbon Monoxide and Cyanide Poisoning in the Burned Pregnant Patient: An Indication for Hyperbaric Oxygen Therapy

Carbon monoxide (CO) is a small molecule poison released as a product of incomplete combustion. Carbon monoxide binds hemoglobin, reducing oxygen delivery. This effect is exacerbated in the burned pregnant patient by fetal hemoglobin that binds CO 2.5- to 3-fold stronger than maternal hemoglobin. With no signature clinical symptom, diagnosis depends on patient injury history, elevated carboxyhemoglobin levels, and alterations in mental status. The standard of care for treatment of CO intoxication is 100% normobaric oxygen, which decreases the half-life of CO in the bloodstream from 5 hours to 1 hour. Hyperbaric oxygen (HBO2) is a useful adjunct to rapidly reduce the half-life of CO to 20 minutes and the incidence of delayed neurologic sequelae. Because of the slow disassociation of CO from hemoglobin in the fetus, there is a far stronger indication for HBO2 in the burned pregnant patient than in other burn patient populations.Cyanide intoxication is often a comorbid disease with CO in inhalation injury from an enclosed fire, but may be the predominant toxin. It acts synergistically with CO to effectively lower the lethal doses of both cyanide and CO. Diagnosis is best made in the presence of high lactate levels, carboxyhemoglobin concentrations greater than 10%, injury history of smoke inhalation from an enclosed fire, and alterations in consciousness. While treatment with hydroxocobalamin is the standard of care and has the effect of reducing concomitant CO toxicity, data indicate cyanide may also be displaced by HBO2.Carbon monoxide and cyanide poisoning presents potential complications impacting care. This review addresses the mechanism of action, presentation, diagnosis, and treatment of CO and cyanide poisonings in the burned pregnant patient and the use of HBO2 therapy.

The impact of hyperthermia after acute carbon monoxide poisoning on neurological sequelae

This study investigated whether hyperthermia within the first 24 h after presentation was associated with long-term neurological outcomes after acute carbon monoxide (CO) poisoning. This retrospective study included 200 patients with acute severe CO poisoning. Hyperthermia (≥ 37.5°C) developed during the first 24 h after presentation in 55 (27.5%) patients, and poor long-term neurological sequelae assessed at 23 months after acute CO poisoning developed in 19.5% of the patients. The incidence of poor long-term neurological outcomes was significantly higher in the hyperthermia group than in the normothermia group. Patients with poor long-term neurological outcomes had higher maximum temperatures than patients with good outcomes. No significant difference was found in the time of hyperthermia onset within the first day according to the neurological outcomes. Hyperthermia (adjusted odds ratio (aOR) 5.009 (95% confidence interval (CI) 1.556-16.126)) and maximum temperature (aOR 2.581 (95% CI 1.098-6.063)) within the first 24 h after presentation to the emergency department were independently associated with poor long-term neurological outcomes. Body temperature measurements, which are easily and noninvasively recorded at the bedside in any facility, help to predict the risk for poor long-term neurological outcomes. This study carefully emphasizes fastidious control of pyrexia, particularly during the early period after acute CO poisoning.

Serum markers and development of delayed neuropsychological sequelae after acute carbon monoxide poisoning: anion gap, lactate, osmolarity, S100B protein, and interleukin-6

Objective

Reliable biomarkers of delayed neuropsychological sequelae (DNS) after acute carbon monoxide (CO) poisoning are lacking. This study investigated the associations between potential serum markers and the development of DNS after acute CO poisoning.

Methods

Retrospective chart reviews were conducted for patients diagnosed with acute CO poisoning during a 28-month period. The patients were divided into two groups according to the presence or absence of having developed DNS. Multivariate analysis was performed to identify predictors of DNS after CO poisoning.

Results

Of a total of 102 patients, 10 (9.8%) developed DNS. The levels of serum osmolarity, S100B protein, and serum lactate, as well as serum anion gap, were statistically significant in univariate analysis. Multiple logistic regression analysis showed that anion gap (adjusted odds ratio [AOR], 1.36; 95% confidence interval [CI], 1.11 to 1.88), serum lactate level (AOR, 1.74; 95% CI, 1.26 to 2.75), and serum S100B protein level ([AOR, 7.02×10⁵; 95% CI, 4.56×10² to 9.00×10¹⁰] in model 1, [AOR, 3.69×10⁵; 95% CI, 2.49×10² to 2.71×10¹¹] in model 2) were independently associated with DNS development.

Conclusion

Based on our preliminary results, serum lactate level, serum anion gap, and serum S100B protein level in the emergency department could be informative predictors of DNS development in patients with acute CO poisoning. These markers might have the potential to improve early recognition of DNS in patients with acute CO poisoning.

Dynamic changes and clinical significance of serum S100B protein and glial fibrillary acidic protein in patients with delayed encephalopathy after acute carbon monoxide poisoning

Objective:

To study the dynamic changes and clinical significance of serum S100B protein and glial fibrillary acidic protein (GFAP) in patients with delayed encephalopathy after acute carbon monoxide poisoning (DEACMP).

Methods:

This study was conducted among DEACMP patients who were hospitalized from November 2014 to February 2016. Serum levels of S100B and GFAP in 66 DEACMP patients were measured by ELISA. Changes in patient states were examined dynamically using activities of daily living (ADL) scale, information-memory-concentration test (IMCT) and Hasegawa’s dementia scale (HDS), and compared with those of 64 patients without DE after ACMP.

Results:

Serum S100B [(0.59 ± 0.11) ng/ml] and GFAP [(227.67 ± 12.43) ng/ml] levels of DEACMP group in acute phase were significantly higher than those of ACMP group [(0.48 ± 0.10) ng/ml and (178.91 ± 11.47) ng/ml] and DEACMP group in recovery phase [(0.49 ± 0.12) ng/ml and (179.54 ± 12.32) ng/ml] (all P<0.05). Serum S100B and GFAP levels of DEACMP group were significantly correlated in both acute and recovery phases (r=0.432 in acute phase, P=0.007; r=0.378 in recovery phase, P=0.034). ADL, HDS and IMCT scores of DEACMP group in acute phase were (45.12 ± 3.12), (7.98 ± 1.02) and (9.61 ± 1.41) points respectively, which were significantly different from those of recovery phase [(33.25 ± 3.09), (16.13 ± 1.17) and (19.54 ± 1.43) points respectively] (P<0.05).

Conclusions:

DEACMP was accompanied by secondary brain injury, for which glial activation may be important. Serum S100B and GFAP levels may be related to prognosis.

Neuroprotective effect of ethanol in acute carbon monoxide intoxication: A retrospective study

In acute carbon monoxide (CO) intoxication, treatment of neurologic injury and prevention of neurological sequelae are primary concerns. Ethanol is the one of the frequent substances which is co-ingested in intentional CO poisoning. Neuroprotective effect of ethanol was highlighted and demonstrated in isolated brain injury recently. We assessed the neuroprotective effect of ethanol in acute CO intoxication using magnetic resonance imaging (MRI).We retrospectively reviewed medical records for patients who visited an emergency medical center of a university-affiliated hospital during a period of 73 months, from March 2009 to April 2015. Enrolled patients were divided into 2 groups, patients with or without abnormal brain lesion in brain MRI. Multivariate logistic regression analysis was performed to assess the factors associated with brain injury in MRI.A total of 109 patients with acute CO intoxication were evaluated of which 66 (60.55%) tested positive in brain MRI. MRI lesion-positive patients were more likely to have electrocardiogram change, elevation of serum troponin I and s100 protein level and lower serum ethanol level. Serum ethanol positivity was an independent factor for prevalence of brain injury in MRI in acute CO poisoning.This study revealed that ethanol which is co-ingested in acute CO intoxication may work the neuroprotective effect and could consequence more favorable neurological outcome in acute CO intoxication.

'Not quite out of the woods': potential for misdiagnosis of delayed neurologic syndrome of carbon monoxide poisoning as relapse of mental illness

OBJECTIVE

The aim of this paper is to provide an overview of the delayed neurologic syndrome of carbon monoxide poisoning and its clinical importance in psychiatric settings.

METHOD

A brief review of carbon monoxide poisoning is presented with a focus on the delayed neurologic syndrome and a case of deliberate self- poisoning is described.

RESULTS

As in the case described, the delayed manifestations of carbon monoxide poisoning can resemble a relapse of psychiatric illness.

CONCLUSIONS

In cases of carbon monoxide poisoning it is important to consider the delayed neurologic syndrome as misdiagnosis could lead to inappropriate treatment and worsened outcome.

Advanced neuroimaging of carbon monoxide poisoning

Carbon monoxide (CO) inhalation is nowadays the most common cause of fatal poisoning worldwide. CO binds to haemoglobin 230-270 times more avidly than oxygen, thus leading to formation of carboxyhaemoglobin with subsequent reduction of tissue oxygenation. Brain is mainly affected due to its high oxygen requirement. Up to two-thirds of patients who survive the acute phase of this pathology present a delayed leukoencephalopathy, usually in a period ranging from two to 40 days. White matter damage closely relates to long-term prognosis of these patients. On the other hand CO seems to play a fundamental role as a possible neuro-protective agent in ischaemic stroke. Diagnostic imaging, with computed tomography and magnetic resonance imaging, especially magnetic resonance spectroscopy, is very useful to depict the presence and extension of this pathology, in both acute and late phase. Nevertheless, a correlation of imaging studies with clinical history and laboratory data is fundamental to perform the correct diagnosis. The purpose of this article is to highlight the imaging features of brain CO poisoning in acute and late phase, describing a case report of a 56-year-old man found unconscious at home.

Anti-inflammatory signaling: the point of convergence for medical gases in neuroprotection against ischemic stroke

Recent studies suggest that a variety of medical gases confer neuroprotective effects against cerebral ischemia, extending function beyond their regular clinical applications. The mechanisms underlying ischemic neuroprotection afforded by medical gases have been intensively studied over the past two decades. A number of signaling pathways have been proposed, among which anti-inflammatory signaling has been proven to be critical. Pursuit of the role for anti-inflammatory signaling may shed new light on the translational application of medical gas-afforded neuroprotection.

Characteristics of exogenous carbon monoxide deliveries

Carbon monoxide (CO) has long been considered an environmental pollutant and a poison. Exogenous exposure to amounts of CO beyond the physiologic level of the body can result in a protective or adaptive response. However, as a gasotransmitter, endogenous CO is important for multiple physiologic functions. To date, at least seven distinct methods of delivering CO have been utilized in animal and clinical studies. In this mini-review, we summarize the exogenous CO delivery methods and compare their advantages and disadvantages.

Treatment of acute carbon monoxide poisoning with induced hypothermia

Objective

The effect of induced hypothermia on severe acute carbon monoxide (CO) poisoning remains to be addressed further. We investigated the effect of induced hypothermia on severe acute CO poisoning.

Methods

Retrospective chart review was conducted for patients who diagnosed as severe acute CO poisoning in emergency department and underwent induced hypothermia from May 2013 to May 2014. Hospital courses with critical medication and major laboratory results were investigated through the chart review.

Results

Among total 227 patients with acute CO poisoning during the period of study, patients with severe acute CO poisoning were 15. All patients underwent induced hypothermia with a temperature goal 33°C. Initial and follow-up levels of S100B protein after induced hypothermia were 0.47 μg/L (interquartile range, 0.11 to 0.71) and 0.10 μg/L (interquartile range, 0.06 to 0.37), respectively (P = 0.01). The mean Glasgow Coma Scales at emergency department admission was 6.87 ± 3.36. Except 1 patient who expired after cardiopulmonary resuscitation, Glasgow Coma Scales at 30-day of hospital discharge were 15 in 10 patients (71.4%), 14 in 1 patient (7.1%), 13 in 1 patient (7.1%), and 6 in 2 patients (14.2%). Seven patients (46.7%) developed delayed neurologic sequelae. Four patients showed mild types of delayed neurologic sequelae and 3 showed moderate to severe types of delayed neurologic sequelae.

Conclusion

Most of patients underwent induced hypothermia had a good recovery from severe acute CO poisoning. Therefore, induced hypothermia may be considered as a possible treatment in severe acute CO poisoning.