Pathophysiology of brain injuries in acute carbon monoxide poisoning: A novel hypothesis

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.

Hyperbaric oxygen therapy in carbon monoxide poisoning in Moroccan patients

Describe the epidemiological, clinical characteristics of acute carbon monoxide poisoning (COP), and the therapeutic effect of hyperbaric oxygen therapy on patient's clinical outcome. This is the first study in this field in Morocco. It studies retrospectively 309 victims of acute COP with major neurological signs. All patients have been treated with hyperbaric oxygen therapy, and have been admitted by the emergency department of the Mohammed V military training hospital in Rabat, between January 2015 and December 2018. All poisonings were accidental and occurred especially in winter (50%), with a predominance in urban areas (93%). The poisoning was often caused by a non-compliant water heater (91%), multi-causality was in half of the cases, and affected adults and women (mean age: 21 ± 17 years, gender (male:female) 1:1.5. The average admission time to the hyperbaric chamber lasted 9 h 04 min (± 12 h 32 min). Clinical signs were mainly unconsciousness (151 cases), headache (85 cases), vomiting (63 cases), nausea (53 cases), and dizziness (51 cases). All the patients benefitted from hyperbaric oxygen therapy sessions. The clinical outcome was positive in the majority of cases, but 23% of the cases presented minor or major sequelae. Patients with sequelae had a longer length of admission than those who had not. COP is a major public health problem in Morocco. Through this study, we suggest the interest of hyperbaric oxygen therapy, especially when it is administered timely without delay.

Association between Early Phase Serum Lactate Levels and Occurrence of Delayed Neuropsychiatric Sequelae in Adult Patients with Acute Carbon Monoxide Poisoning: A Systematic Review and Meta-Analysis

The primary goal of treating carbon monoxide (CO) poisoning is preventing or minimizing the development of delayed neuropsychiatric sequelae (DNS). Therefore, screening patients with a high probability for the occurrence of DNS at the earliest is essential. However, prognostic tools for predicting DNS are insufficient, and the usefulness of the lactate level as a predictor is unclear. This systematic review and meta-analysis investigated the association between early phase serum lactate levels and the occurrence of DNS in adult patients with acute CO poisoning. Observational studies that included adult patients with CO poisoning and reported initial lactate concentrations were retrieved from the Embase, MEDLINE, Google Scholar and six domestic databases (KoreaMED, KMBASE, KISS, NDSL, KISTi and RISS) in January 2022. Lactate values were collected as continuous variables and analyzed using standardized mean differences (SMD) using a random-effect model. The risk of bias was evaluated using the Quality in Prognosis Studies (QUIPS) tool, and subgroup, sensitivity and meta regression analyses were performed. Eight studies involving a total of 1350 patients were included. The early phase serum lactate concentration was significantly higher in the DNS group than in the non-DNS group in adult patients with acute CO poisoning (8 studies; SMD, 0.31; 95% CI, 0.11−0.50; I2 = 44%; p = 0.002). The heterogeneity decreased to I2 = 8% in sensitivity analysis (omitting Han2021; 7 studies; SMD, 0.38; 95% CI, 0.23−0.53; I2 = 8%; p < 0.001). The risk of bias was assessed as high in five studies. The DNS group was associated with significantly higher lactate concentration than that in the non-DNS group.

Abnormal Brain Functional Network Dynamics in Acute CO Poisoning

Aims: Carbon monoxide poisoning is a common condition that can cause severe neurological sequelae. Previous studies have revealed that functional connectivity in carbon monoxide poisoning is abnormal under the assumption that it is resting during scanning and have focused on studying delayed encephalopathy in carbon monoxide poisoning. However, studies of functional connectivity dynamics in the acute phase of carbon monoxide poisoning may provide a more insightful perspective for understanding the neural mechanisms underlying carbon monoxide poisoning. To our knowledge, this is the first study that explores abnormal brain network dynamics in the acute phase of carbon monoxide poisoning.

Methods: Combining the sliding window method and k-means algorithm, we identified four recurrent dynamic functional cognitive impairment states from resting-state functional magnetic resonance imaging data from 29 patients in the acute phase of carbon monoxide poisoning and 29 healthy controls. We calculated between-group differences in the temporal properties and intensity of dFC states, and we also performed subgroup analyses to separately explore the brain network dynamics characteristics of adult vs. child carbon monoxide poisoning groups. Finally, these differences were correlated with patients’ cognitive performance in the acute phase of carbon monoxide poisoning and coma duration.

Results: We identified four morphological patterns of brain functional network connectivity. During the acute phase of carbon monoxide poisoning, patients spent more time in State 2, which is characterized by positive correlation between SMN and CEN, and negative correlation between DMN and SMN. In addition, the fractional window and mean dwell time of State 2 were positively correlated with coma duration. The subgroup analysis results demonstrated that the acute phase of childhood carbon monoxide poisoning had greater dFNC time variability than adult carbon monoxide poisoning.

Conclusion: Our findings reveal that patients in the acute phase of carbon monoxide poisoning exhibit dynamic functional abnormalities. Furthermore, children have greater dFNC instability following carbon monoxide poisoning than adults. This advances our understanding of the pathophysiological mechanisms underlying acute carbon monoxide poisoning.

Right Hemiplegia Following Acute Carbon Monoxide Poisoning

Acute carbon monoxide (CO) poisoning remains a common cause of poison-related death and influences neurological function. An 83-year-old female was transferred to our emergency unit due to hypertension with dizziness, headache, and right hemiplegia. There was no radiographic evidence of ischemic stroke. The family members reported that the patient may have been exposed to CO by briquettes burned inside a closed room. High flow oxygen therapy was given for suspected CO intoxication and her symptoms quickly improved. Although we do not have clear evidence, we presume that hemiplegia in our patient was caused by CO intoxication, based on rapid recovery with oxygen therapy, carboxyhemoglobin (COHb) level elevation (3.0%), polycythemia, and neuroimaging. Despite the hematogenous effects of CO, paralysis appeared to be more severe on her right side than on her left side. MRI and blood tests helped to support CO as the suspected cause of her hemiplegia. This case reconfirms the importance of medical interviewing by medical practitioners, even in an emergency setting.

Effects of noise and low-concentration carbon monoxide exposure on rat immunity

OBJECTIVE

To evaluate the immunotoxicity and effects of noise and/or low-concentration carbon monoxide (CO) exposure on immune organs and immune functions in rats.

METHODS

Male Wistar rats exposed to 98 dB(A) white noise and/or 100 ppm CO 4 h/d for 30 d were used to determine the pathological changes in the thymus and spleen, and variations in leukocyte counts, inflammatory factors, and immunoglobulin (Ig) concentrations.

RESULTS

The boundaries of the cortex and medulla of the thymus were unclear following noise and combined exposure. The pathological changes in spleen after CO and combined exposure included blurred boundaries of red-pulp and white-pulp, disappearance of normal splenic nodules and neutrophil infiltration. After exposure to noise and in combination, leukocyte and lymphocyte counts decreased significantly. After exposure to low-concentration CO and in combination, serum IgM and IgG levels decreased significantly, but the levels of tumor necrosis factor-α and interferon-γ levels increased significantly. Eosinophils and IgA levels decreased significantly following exposure to noise and/or low concentration of CO, while the level of interleukin-1 increased significantly. Monocytes increased significantly only under noise or CO exposure, but not under combined exposure.

CONCLUSIONS

Noise and/or low-concentration CO exposure may suppress innate and adaptive immune functions and induce inflammatory responses. Noise exposure mainly affected the innate immune function of rats, whereas low-concentration CO exposure mainly affected adaptive immune functions. Combined exposure presented higher immunotoxicity than noise or CO alone, suggesting that exposure to noise and low-concentration CO in the living and working environments can affect the immune system.

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.

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.

Cox regression model of prognostic factors for delayed neuropsychiatric sequelae in patients with acute carbon monoxide poisoning: A prospective observational study

OBJECTIVE

A major challenge for physicians is to identify patients with acute carbon monoxide (CO) poisoning who are likely to develop delayed neuropsychiatric sequelae (DNS). DNS is defined as neuropsychological sequelae that develops after 2-40 days of lucid interval after CO intoxication. Currently, there is no consensus on factors that predict the prognosis of CO poisoning. Thus, the purpose of this study was to identify factors predicting the development of DNS using a Cox regression model.

METHODS

This prospective observational study included 310 CO-poisoned patients admitted to an emergency department in South Korea from July 2017 to February 2020. Demographic, clinical, and laboratory data were analyzed. Kaplan-Meier curves were constructed to estimate the cumulative incidence of DNS. A multivariate Cox regression model was used to identify the main predictors of the development of DNS.

RESULTS

The incidence of DNS was 18.8 %, and the median onset time was 23.7 days (interquartile range, 14-30 days). The Kaplan-Meier survival curve showed that a serum creatine kinase (CK) level > 175.5 U/L and initial Glasgow Coma Scale (GCS) score ≤ 9 were associated with a higher cumulative incidence of DNS (log-rank test; p < 0.01 and p = 0.02, respectively). Cox regression analysis showed that a serum CK level > 175.5 U/L (hazard ratio [HR]: 2.862, 95 % confidence interval [CI]: 1.491-5.496; p < 0.01) and an initial GCS ≤ 9 (HR: 2.081, 95 % CI: 1.048-4.131; p = 0.04) were significant prognostic factors.

CONCLUSION

In acute CO poisoning, an initial GCS score ≤ 9 and serum CK level > 175.5 U/L are significant predictors of DNS development.

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.

Abnormal degree centrality in delayed encephalopathy after carbon monoxide poisoning: a resting-state fMRI study

Purpose

To explore neuropathologic mechanisms in functional brain regions in patients with delayed encephalopathy after carbon monoxide poisoning (DEACMP) from the perspective of the brain network nodes by resting-state functional magnetic resonance imaging (rs-fMRI).

Methods

The fMRI and cognitive assessments were performed in 25 patients with DEACMP and 25 age-, sex- and education-matched healthy controls (HCs). Data analysis was performed via the degree centrality (DC) method. Then, the associations between the cognitive assessments and DC in the identified abnormal brain regions were assessed by using a correlation analysis.

Results

Compared with the HCs, the DEACMP patients displayed significantly decreased DC values in the right superior frontal gyrus, right precentral gyrus, right angular gyrus, right marginal gyrus, right hippocampus, and left thalamus but increased DC values in the right inferior frontal gyrus, right cingulate gyrus, left superior temporal gyrus, left medial temporal gyrus, right lingual gyrus, and right posterior cerebellar lobe, pons, and midbrain (GRF correction, voxel P value < 0.001, cluster P value < 0.01). The correlation analysis in the DEACMP group revealed that there was a negative correlation between the DC values in the right hippocampus and MMSE scores, whereas a positive correlation was observed in the right cingulate gyrus.

Conclusions

Patients with DEACMP exhibited abnormal degree centrality in the brain network. This finding may provide a new approach for examining the neuropathologic mechanisms underlying DEACMP.

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.

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.

Thiamine deficiency in childhood with attention to genetic causes: Survival and outcome predictors

Primary and secondary conditions leading to thiamine deficiency have overlapping features in children, presenting with acute episodes of encephalopathy, bilateral symmetric brain lesions, and high excretion of organic acids that are specific of thiamine-dependent mitochondrial enzymes, mainly lactate, alpha-ketoglutarate, and branched chain keto-acids. Undiagnosed and untreated thiamine deficiencies are often fatal or lead to severe sequelae. Herein, we describe the clinical and genetic characterization of 79 patients with inherited thiamine defects causing encephalopathy in childhood, identifying outcome predictors in patients with pathogenic SLC19A3 variants, the most common genetic etiology. We propose diagnostic criteria that will aid clinicians to establish a faster and accurate diagnosis so that early vitamin supplementation is considered. Ann Neurol 2017;82:317-330.

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.

Neuro-Protective Effects of Resveratrol on Carbon Monoxide-Induced Toxicity in Male Rats

Acute carbon monoxide (CO) poisoning causes neurotoxicity through induction of necrosis, apoptosis, lipid peroxidation and oxidative stress. Resveratrol (RES) is a natural polyphenolic phytoalexin that exhibits neuroprotective effects in ischemia/reperfusion due to its anti-apoptotic, anti-necrotic and strong anti-oxidant properties as well as its ability to activate pro-survival pathways. In this study, rats were exposed to CO 3000 ppm for 1 h. Immediately after poisoning and on the next four consecutive days, RES (1, 5 and 10 mg/kg) was administered intraperitoneally. On the fifth day, animals' brains were excised, and necrosis, lipid peroxidation level and the level of Akt, BAX and BCL2 expression were evaluated. The results showed that RES 10 mg/kg significantly reduced lipid peroxidation, but RES 1 and 5 mg/kg had no significant effect on this parameter. Furthermore, RES 5 and 10 mg/kg significantly increased Akt expression level, while BAX/BCL2 ratio was reduced by RES 1, 5 and 10 mg/kg. Moreover, RES reduced necrotic foci in the brain, but the best results were seen following treatment with RES 10 mg/kg. In summary, RES showed neuroprotective effect in CO-poisoned rats as it decreased necrosis and BAX/BCL2 ratio and increased Akt expression levels. Copyright © 2017 John Wiley & Sons, Ltd.

Neuroprotective effects of methane-rich saline on experimental acute carbon monoxide toxicity

BACKGROUND

Methane has been reported to play a protective role in ischemia-reperfusion injury via anti-oxidation, anti-inflammatory and anti-apoptotic activities. This study was designed to determine the protective effects of methane-rich saline (MRS) on acute carbon monoxide (CO) poisoning.

METHODS

A total of 36 male Sprague-Dawley rats were randomly divided into 3 groups: sham group, CO group and MRS group. Acute CO poisoning was induced by exposing rats to 1000ppm CO in air for 40min and then to 3000ppm CO for an additional 20min until they lost consciousness. MRS at 10ml/kg was intraperitoneally administered at 0h, 8h and 16h after CO exposure. Rats were sacrificed 24h after CO exposure. Brains were collected for Nissl staining. The cortex and hippocampus were separated for the detections of malondialdehyde (MDA), 3-nitrotyrosine (3-NT), 8-hydroxydeoxyguanosine (8-OHdG), tumor necrosis factor-α (TNF-α), interleukin1-β (IL-1β), interleukin-6 (IL-6) and superoxide dismutase (SOD) activities.

RESULTS

The results showed that MRS treatment improved neuronal injury, reduced MDA, 3-NT and 8-OHdG, and increased SOD activity of the hippocampus and cortex compared with normal saline-treated rats. In addition, MRS reduced the expression of TNF-α and IL-1β in the brain but had no effect on IL-6 expression.

CONCLUSION

These findings suggest that MRS may protect the brain against acute CO poisoning-induced injury via its anti-oxidative and anti-inflammatory activities.

Hyperbaric oxygen preserves neurotrophic activity of carbon monoxide-exposed astrocytes

In astrocytes, carbon monoxide (CO) poisoning causes oxidative stress and mitochondrial dysfunction accompanied by caspase and calpain activation. Impairment in astrocyte function can be time-dependently reduced by hyperbaric (3bar) oxygen (HBO). Due to the central role of astrocytes in maintaining neuronal function by offering neurotrophic support we investigated the hypothesis that HBO therapy may exert beneficial effect on acute CO poisoning-induced impairment in intrinsic neurotrophic activity. Exposure to 3000ppm CO in air followed by 24-72h of normoxia caused a progressive decline of gene expression, synthesis and secretion of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) to different extent. 1h treatment with 100% oxygen disclosed a pressure- and time-dependent efficacy in preserving astrocytic neurotrophic support. The beneficial effect was most evident when the astrocytes were exposed to HBO 1-5h after exposure to CO. The results further support an active role of hyperbaric, not normobaric, oxygenation in reducing dysfunction of astrocytes after acute CO poisoning. By preserving endogenous neurotrophic activity HBO therapy might promote neuronal protection and thus prevent the occurrence of late neuropsychological sequelae.

Possible role of antioxidants and nitric oxide inhibitors against carbon monoxide poisoning: Having a clear conscience because of their potential benefits

Carbon monoxide poisoning is one of the important emergency situations manifested by primarily acute and chronic anoxic central nervous system (CNS) injuries and other organ damages. Current descriptions and therapeutic approaches have been focused on the anoxic pathophysiology. However, this point of view incompletely explains some of the outcomes and needs to be investigated extensively. Considering this, we propose that reactive oxygen species (ROS) including especially nitric oxide (NO) are likely to be a key concept to understand the emergency related to CO poisoning and to discover new therapeutic modalities in CO toxicity. If we consider the hypothesis that ROS is involved greatly in acute and chronic toxic effects of CO on CNS and some other vital organs such as heart, it follows that the antioxidant and anti-NO therapies might give the clinicians more opportunities to prevent deep CNS injury. In support of this, we review the subject in essence and summarize clinical and experimental studies that support a key role of ROS in the explanation of pathophysiology of CO toxicity as well as new treatment modalities after CO poisoning.

Carbon monoxide intoxication

Carbon monoxide (CO) is a colorless, odorless, nonirritant gas that accounts for numerous cases of CO poisoning every year from a variety of sources of incomplete combustion of hydrocarbons. These include poorly functioning heating systems, indoor propane-powered forklifts, indoor burning of charcoal burning briquettes, riding in the back of pick-up trucks, ice skating rinks using propane-powered resurfacing machines, and gasoline-powered generators that are not in correct locations. Once CO is inhaled it binds with hemoglobin to form carboxyhemoglobin (COHb) with an affinity 200 times greater than oxygen that leads to decreased oxygen-carrying capacity and decreased release of oxygen to tissues leading to tissue hypoxia. Ischemia occurs with CO poisoning when there is loss of consciousness that is accompanied by hypotension and ischemia in the arterial border zones of the brain. Besides binding to many heme-containing proteins, CO disrupts oxidative metabolism leading to the formation of free radicals. Once hypotension and unconsciousness occur with CO poisoning, lipid peroxidation and apoptosis follow. Because COHb has a short half-life, examination of other biomarkers of CO neurotoxicity that reflect inflammation or neuronal damage has not demonstrated consistent results. The initial symptoms with CO exposure when COHb is 15-30% are nonspecific, namely, headache, dizziness, nausea, fatigue, and impaired manual dexterity. However individuals with ischemic heart disease may experience chest pain and decreased exercise duration at COHb levels between 1% and 9%. COHb levels between 30% and 70% lead to loss of consciousness and eventually death. Following resolution of acute symptoms there may be a lucid interval of 2-40 days before the development of delayed neurologic sequelae (DNS), with diffuse demyelination in the brain accompanied by lethargy, behavior changes, forgetfulness, memory loss, and parkinsonian features. Seventy-five percent of patients with DNS recover within 1 year. Neuropsychologic abnormalities with chronic CO exposure are found even when magnetic resonance imaging (MRI) and magnetic resonance spectroscopy are normal. White-matter damage in the centrum semiovale and periventricular area and abnormalities in the globus pallidus are most commonly seen on MRI following CO exposure. Though not as common, toxic or ischemic peripheral neuropathies are associated with CO exposure in humans and animals. The cornerstone for treatment for CO poisoning is 100% oxygen using a tight-fitting mask for greater than 6 hours. The indications for treatment with hyperbaric oxygen to decrease the half-life of COHb remain controversial.