Clinical practice. Carbon monoxide poisoning

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

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

Carbon monoxide poisoning with hippocampi lesions on MRI: cases report and literature review

BACKGROUND

Carbon monoxide (CO) poisoning is now one of the leading causes of poisoning-related mortality worldwide. The central nervous system is the most vulnerable structure in acute CO poisoning. MRI is of great significance in the diagnosis and prognosis of CO toxic encephalopathy. The imaging features of CO poisoning are diverse. We report atypical hippocampal lesions observed on MRI in four patients after acute CO exposure.

CASE PRESENTATIONS

We report four patients who presented to the emergency department with loss of consciousness. The diagnosis of CO poisoning was confirmed on the basis of their detailed history, physical examination and laboratory tests. Brain MRI in all of these patients revealed abnormal signal intensity in hippocampi bilaterally. They all received hyperbaric oxygen therapy. The prognosis of all four patients was poor.

CONCLUSION

Hippocampi, as a relatively rare lesion on MRI of CO poisoning, is of important significance both in the early and delayed stages of acute CO poisoning. In this article, we summarize the case reports of hippocampal lesions on MRI in patients with CO poisoning in recent years, in order to provide reference for the diagnosis and prognosis of CO poisoning.

Fire deaths in Cape Town, South Africa: A retrospective review of medico-legal and toxicological findings (2006 - 2018)

BACKGROUND

In South Africa, fire-related deaths are common, particularly within dense informal housing settlements. Published data on deaths from fire incidents in Cape Town is sparse. Additionally, little emphasis has been placed on the role of toxicological investigations in these deaths, despite the known risk of alcohol and drug impairment to burn injury.

METHODS

A retrospective, descriptive analysis of post-mortem case reports from Salt River Mortuary was conducted to investigate all deaths in which fires were involved in the west metropole of Cape Town, between 2006 to 2018. Demographic, circumstantial, and toxicological data were analyzed using R software.

RESULTS

In total 1370 fire deaths occurred over 13 years, with a mean of 106 (SD ± 18) cases per annum (≈3% of the annual caseload and a mortality rate of 5.5 per 100,000). Males (70.4%), adults (mean=30.7 years), and toddlers (1-4 years old) were notably at risk. Deaths typically occurred in the early morning (00h00 - 06h00) (45.7%), during winter (32.1%), and in lower socioeconomic areas with highly dense informal settlements (65.6%), with 29% of deaths occurring in multi-fatality incidents. Ethanol was detected (≥0.01 g/100 mL) in 55.1% of cases submitted for analysis (71.5%), with a mean of 0.18 g/100 mL, and with 93.8% of positive cases > 0.05 g/100 mL. Carboxyhaemoglobin (COHb) analysis was requested in 76.4% of cases, with 57% of cases having a %COHb of ≥ 20%. Toxicology results (for drugs other than ethanol) from the national laboratory were outstanding in 34.4% of the cases at the conclusion of the study. BAC and %COHb were significantly higher in deaths from burns and smoke inhalation (usually accidents) than deaths from combined trauma and burns (typically homicides). Fire deaths with high COHb levels were more likely to display cherry-red discoloration (OR=3.1) and soot in the airways (OR=2.7) at autopsy.

CONCLUSION

This article provides an updated description of fire deaths in the west metropole of Cape Town. The importance of BAC and COHb testing in these cases was noted, and the authors call for an investigation of the role of drug impairment (specifically frequently misused drugs methamphetamine and methaqualone) as a risk factor in these deaths. Areas of high-density informal settlements, where open flames are used to heat, light, and cook, were noted as high risk.

Carbon Monoxide Poisoning: From Occupational Health to Emergency Medicine

Carbon monoxide poisoning remains a leading cause of accidental poisoning worldwide (both at home and at work), and it is also a cause of suicidal poisoning. Such poisoning can arise following prolonged exposure to low levels of CO or following brief exposure to high concentrations of the gas. In fact, despite exposure limits, high safety standards, and the availability of CO alarms, nearly 50,000 people in the United States visit the emergency department each year due to poisoning. Additionally, CO poisoning in the United States causes up to 500 deaths each year. Despite the widespread nature of this form of poisoning, known about for centuries and whose damage mechanisms have been recognized (or rather hypothesized about) since the 1800s, early recognition, especially of late complications, and treatment remain a medical challenge. A well-designed therapeutic diagnostic process is necessary so that indication for hyperbaric or normobaric therapy is correctly made and so that patients are followed up even after acute exposure to diagnose late complications early. Furthermore, it is necessary to consider that in the setting of emergency medicine, CO poisoning can be part of a differential diagnosis along with other more frequent conditions, making its recognition difficult. The last thirty years have been marked by a significant increase in knowledge regarding the toxicity of CO, as well as its functioning and its importance at physiological concentrations in mammalian systems. This review, taking into account the significant progress made in recent years, aims to reconsider the pathogenicity of CO, which is not trivially just poisonous to tissues. A revision of the paradigm, especially as regards treatment and sequelae, appears necessary, and new studies should focus on this new point of view.

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

Background

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

Methods

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

Results

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

Conclusion

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

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

OBJECTIVES

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

METHODS

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

RESULTS

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

DISCUSSION

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

CONCLUSIONS

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

Carbon Monoxide Poisoning: From Microbes to Therapeutics

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

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.

The role of carbon monoxide in aerotoxic syndrome

Chronic low-level exposure to toxic compounds in airplane cabin air may result in Aerotoxic Syndrome (AS). Aetiologic agents are organophosphates and numerous volatile organic hydrocarbons originating from leaks of engine oil and hydraulic fluids. Despite a documented history spanning decades, the role of carbon monoxide remains controversial. What evidence exists that carbon monoxide (CO), present in the cocktail of toxic compounds in bleed air, contributes to the AS? We selected 22 publications encompassing 888 flights with 18 different aircraft types. In one study of 100 flights, fume events were confirmed in 38. Four studies were initialized after air quality incidents. The cabin CO concentrations could be categorized in three levels, 1) low (<5 ppm), without health implications, 2) moderate (5-10 ppm) with probably health implications in case of chronic exposure, and 3) high > 10 ppm, with health effects in case of acute and chronic exposure. These levels were recorded in 12, 6 and 4 studies respectively. In the six studies in category 2, max CO concentrations ranged from 5.8-9.4 ppm. The four studies with CO > 10 ppm comprised 376 of the 888 flights (42%) with six aircraft types. Toxic CO levels ranging between 13-60 ppm were identified in at least 129 of 888 (14.5%) flights. In one study with high CO levels four flight attendants were diagnosed with CO poisoning with elevated HbCO levels. Max CO levels in aviation are either the same or higher than current occupational exposure limits (OEL) for ground-based workplace exposures or levels for urban street transport environments. Specific aspects of aviation should be taken into consideration: the effect of low(er) air pressure at high altitudes increasing the toxicity of CO, and the binding of CO to CYP enzymes, leading to impaired organophosphate detoxification. We conclude that CO must be considered an important factor in the lubrication derived cocktail of airborne toxic compounds causing AS. In line with the WHO advice, a reduction of the OEL to 5 ppm over 8 hr time weighted average (TWA) for aircrew is strongly recommended. And we advocate continuous monitoring during all phases of flight and installation of CO detectors in the air supply ducts to the aircraft cabin.

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.

Carbon Monoxide Alleviates Post-ischemia-reperfusion Skeletal Muscle Injury and Systemic Inflammation

Restoration of blood flow in skeletal muscle after a prolonged period of ischemia induces muscular ischemia-reperfusion injury, leading to local injury/dysfunction in muscles followed by systemic inflammatory responses. However, preventive/curative agents for skeletal muscle ischemia injury are unavailable in clinics to date. Increasing evidence has validated that carbon monoxide (CO) prevents the progression of ischemia-reperfusion injury in various organs owing to its versatile bioactivity. Previously, we developed a bioinspired CO donor, CO-bound red blood cells (CO-RBC), which mimics the dynamics of RBC-associated CO in the body. In the present study, we have tested the therapeutic potential of CO-RBC in muscular injury/dysfunction and secondary systemic inflammation induced by skeletal muscle ischemia-reperfusion. The results indicate that CO-RBC rather than RBC alone suppressed elevation of plasma creatine phosphokinase, a marker of muscular injury, in rats subjected to both hind limbs ischemia-reperfusion. In addition, the results of the treadmill walking test revealed a significantly decreased muscular motor function in RBC-treated rats subjected to both hind limbs ischemia-reperfusion than that in healthy rats, however, CO-RBC treatment facilitated sustained muscular motor functions after hind limbs ischemia-reperfusion. Furthermore, CO-RBC rather than RBC suppressed the production of tumour necrosis factor (TNF)-α and interleukin (IL)-6, which were upregulated by muscular ischemia-reperfusion. Interestingly, CO-RBC treatment induced higher levels of IL-10 compared to saline or RBC treatments. Based on these findings, we suggest that CO-RBC exhibits a suppressive effect against skeletal muscle injury/dysfunction and systemic inflammatory responses after skeletal muscle ischemia-reperfusion.

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

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

Neonatal hypoxic-ischemic encephalopathy after acute carbon monoxide intoxication during pregnancy. A case report and brief review of the literature

Carbon monoxide (CO) poisoning during pregnancy is a rare occurrence, associated with high maternal and fetal mortality rates. As CO can cross the placenta, leading to intrauterine hypoxia, CO intoxication can result in neurological sequelae and neurologic complications in fetuses who survive. We report a case of a preterm newborn acutely exposed to CO in-utero and delivered by emergent cesarean section at the 31st week of gestation due to the severe burns suffered by the mother following an indoor boiler explosion. As CO has serious adverse effects both on the mother and fetus, it is important to recognize and treat poisoning in a timely manner. Despite maternal blood CO levels, CO intoxication at critical stage of central nervous system development can lead to hypoxic-ischemic lesions, thus interdisciplinary care and follow up for these patients are mandatory.

Effect of the Timing of Hyperbaric Oxygen Therapy on the Prognosis of Patients with Idiopathic Sudden Sensorineural Hearing Loss

This study aimed to evaluate the effects of hyperbaric oxygen therapy (HBOT) on the hearing recovery of patients with idiopathic sudden sensorineural hearing loss (ISSNHL). The clinical data of 79 patients diagnosed with ISSNHL and treated with HBOT between January 2017 and December 2019 were retrospectively reviewed. The pure tone audiometry (PTA) scores before and after HBOT were recorded. The associations of HBOT efficacy with demographic and clinical characteristics and the duration from disease onset to HBOT administration were determined. The average PTA score was 80.06 ± 25.94 dB before and 60.75 ± 21.26 dB after HBOT; the difference was significant. HBOT improved the hearing of 55.7% of the patients with ISSNHL (defined as an average PTA ≥ 11dB or a final average PTA score below 29 dB). There was a significant inverse relationship between the duration from symptom onset to HBOT administration and PTA score reduction after HBOT, which was adjusted for factors including age, sex, laterality of hearing loss, initial PTA score, reception of intratympanic steroid injections, tinnitus, dizziness, vertigo, diabetes, hypertension, and coronary artery disease. Commencing HBOT at an earlier stage is closely linked to greater improvements in hearing for patients with ISSNHL.

Hydranencephaly following carbon monoxide poisoning during pregnancy: An uncommon and potentially fatal complication in infant

BACKGROUND

Hydranencephaly is a rare malformation of the brain system with an incidence of 0.5 per 1000 births. Its principal etiologies are bilateral occlusion of the internal carotid arteries and congenital infections.

CASE

We reported an uncommon case of hydranencephaly diagnosed in 50-day old infant and attributable to carbon monoxide (CO) poisoning during the first trimester of pregnancy.

CONCLUSIONS

We recommend a prompt diagnosis and management of CO poisoning in pregnant women since it can dramatically affect both the fetus and mother.

The emergence and advancement of Tsuji-Trost reaction triggered carbon monoxide recognition and bioimaging

Considering that carbon monoxide is both a vital gasotransmitter and an obnoxious gas, tremendous efforts have been dedicated toward its recognition through various methods. However, the fluorescent light-up approach through the exploration of optical markers remains one of the most convenient methods owing to its several advantages. Amongst the different approaches towards the development of CO responsive optically active molecular markers, the Tsuji-Trost reaction-based CO recognition strategy has remained one of the most significant areas of interest across researchers working in this field. However, there have been no attempts to exclusively summarize the commendable work done in this area yet. The current review, therefore, attempts to summarize the developments of various optical probes following this reaction strategy until the year 2022. This review provides detailed mechanistic insights into the Tsuji-Trost mediated CO detection strategy. Besides, discussions on the strategic development and employment of probes based on various allyl derivatives - allyl carbamate/carbonate/ethers - will provide a thorough understanding of the detection method. The significant advancements of the Tsuji-Trost reaction as an interesting strategy that is accepted and extensively explored for monitoring CO in various media including air, aqueous solutions and living systems have been elaborately discussed. Various potential applications and utilization of these developed fluorogenic probes for tracing CO in different living systems have been examined systematically. Moreover, monitoring of exogenous/endogenous CO levels, modulation of intracellular CO concentration under various induced conditions and bioimaging of CO in in vivo models have also been detailed here. Briefly, this review summarizes the current prospects of this detection method and the future directions in related fields.

Atrial Fibrillation and Silent Coronary Spasm Complicating Severe Carbon Monoxide Poisoning

Carbon monoxide (CO) poisoning is a toxicological emergency and may be responsible for more than half of all fatal poisonings worldwide. Serious effects of CO are frequently seen in the brain and heart as well as other organs that are particularly sensitive to hypoxia. Cardiac manifestations include dysrhythmias, myocardial infarction, and even cardiac arrest. Even in mild cases of CO poisoning with absent chest pain, the emergency physician should evaluate features of myocardial injury, as this can serve as a predictor of mortality and morbidity. A case of a young, healthy man with severe CO poisoning presented with atrial fibrillation (AF) and vasospastic angina, and he was managed successfully with high-flow oxygen.

Prevalence of Carbon Monoxide Poisoning and Hyperbaric Oxygen Therapy in Korea: Analysis of National Claims Data in 2010-2019

This study aimed to investigate the prevalence of carbon monoxide (CO) poisoning and the provision of hyperbaric oxygen therapy (HBOT) in South Korea. We used data from the Korea Health Insurance Review and Assessment service. In total, 44,361 patients with CO poisoning were identified across 10 years (2010-2019). The prevalence of CO poisoning was found to be 8.64/10,000 people, with a gradual annual increment. The highest prevalence was 11.01/10,000 individuals, among those aged 30-39 years. In 2010, HBOT was claimed from 15 hospitals, and increased to 30 hospitals in 2019. A total of 4,473 patients received HBOT in 10 years and 2,684 (60%) were treated for more than 2 hours. This study suggested that the prevalence of both CO poisoning and HBOT in Korea gradually increased over the past 10 years, and disparities in prevalence were observed by region.

Clinical and Laboratory Characteristics Predicting the Severity of Carbon Monoxide Poisoning in Children: A Single-Center Retrospective Study

OBJECTIVES

Carbon monoxide poisoning (COP) is extremely common throughout the world. The purpose of this study was to assess the demographic, clinical, and laboratory characteristics predicting the severity COP in children.

METHODS

The study included 380 children diagnosed with COP between January 2017 and January 2021 and 380 healthy controls. Carbon monoxide poisoning was diagnosed based on the medical history and a carboxyhemoglobin (COHb) level of more than 5%. The patients were classified as mild (COHb 10%), moderate (COHb 10%-25%), or severely (COHb > 25%) poisoned.

RESULTS

The mean age of the severe group was 8.60 ± 6.30, for the moderate group was 9.50 ± 5.81, for the mild group was 8.79 ± 5.94, and for the control group was 8.95 ± 5.98. The most common place of exposure was at home and all cases were affected accidentally. The coal stove was the most common source of exposure, followed by natural gas. The most common symptoms were nausea/vomiting, vertigo, and headache. Neurologic symptoms such as syncope, confusion, dyspnea, and seizures were more common in the severe group. A total of 91.3% of the children had hyperbaric oxygen therapy, 3.8% were intubated, and 3.8% were transferred to intensive care in the severe group, whereas no death or sequela was observed. Mean platelet volume and red cell distribution width had the highest area under the curve in the receiver operating characteristic analysis (0.659; 0.379). A positive and low statistically significant relationship was found between COHb levels and troponin and lactate levels in the severe group ( P < 0.05).

CONCLUSIONS

Carbon monoxide poisoning progressed more severely in children presented with neurological symptoms and have elevated red cell distribution width and mean platelet volume. Even in severe COP cases, satisfactory results have been obtained with early and appropriate treatment.

Unexpected carboxyhemoglobin half-life during cardiopulmonary resuscitation: a case report

BACKGROUND

Cardiac arrest (CA) following CO poisoning (CO-induced CA) exposes patients to an extremely high risk of mortality and remains challenging to treat effectively. Terminal carboxyhemoglobin elimination half-life (COHbt_1/2) is critically affected by ventilation, oxygen therapy, and cardiac output, which are severely affected conditions in cases of CA.

CASE PRESENTATION

Asystole occurred in an 18-year-old woman after unintentional exposure to CO in her bathroom. Cardiopulmonary resuscitation (CPR) was started immediately, including mechanical ventilation with a fraction of inspired oxygen (FiO₂) of 1.0 and external chest compressions with a LUCAS® device. CPR was stopped after 101 min, as it was unsuccessful. During this period, we calculated a COHbt_1/2 of 40.3 min using a single compartmental model.

CONCLUSIONS

This result suggests that prolongation of CPR time needed to back COHb at 10%, a level more compatible with successful return of spontaneous circulation (ROSC), could be compatible with a realistic CPR time. Calculating COHbt_1/2 during CPR may help with decision-making regarding the optimal duration of resuscitation efforts and further with HBO₂ or ECLS. Further evidence-based data are needed to confirm this result.

Imaging of glutamate in acute carbon monoxide poisoning using chemical exchange saturation transfer

Aims

This study adopted the Glutamate Chemical Exchange Saturation Transfer (GluCEST) imaging technique to quantitatively analyze cranial glutamate and discussed the effectiveness of GluCEST values in identifying the pathogenesis of encephalopathy after CO poisoning.

Methods

The routine MRI and functional MRI scans of two cohorts of subjects (CO group, n = 29; Control group, n = 21) were performed. Between-group comparisons were conducted for GluCEST% in regions of interest (ROI), including the basal ganglia, the thalamus, the frontal lobe, the occipital lobe, the genu of corpus callosum, the cingulate gyrus, and the cuneus. Moreover, an age-stratified subgroup analysis was devised, and a correlational analysis was performed for GluCEST% in each ROI, including the time in coma, Simple Mini-Mental State Examination Scale (MMSE) score, Hamilton Anxiety Scale score, and blood COHb%.

Results

As compared to the healthy control, the CO group led to significantly increasing GluCEST% in the basal ganglia, the occipital lobe, the genu of the corpus callosum, the cingulate gyrus, and the cuneus (p < 0.05). In the subgroup analysis for age, adult patients had higher GluCEST% in the basal ganglia, the thalamus, the occipital lobe, the cingulate gyrus, and the cuneus compared to healthy adults (p < 0.05). In addition, the correlational analysis of CO-poisoned patients revealed a statistical association between the GluCEST% and the MMSE in the thalamus and the genu of the corpus callosum.

Conclusion

The GluCEST technique is superior to routine MRI in that it can identify the cerebral biochemical changes sooner after acute CO poisoning, which is significant for our understanding of the role of neurotransmitters in the pathological basis of this disease. Brain injury caused by CO poisoning may be different in adults and children.

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.

A pilot study of neuroprotective effect of granulocyte colony-stimulating factor (G-CSF) in patients with carbon monoxide poisoning: a double-blind, randomized, placebo-controlled trial

Although neuroprotective effects of granulocyte colony-stimulating factor (G-CSF) have been shown in rats exposed to carbon monoxide (CO), this pilot clinical trial was performed to assess the feasibility of treatment with G-CSF in patients with acute CO poisoning. A double-blind, randomized, placebo-controlled pilot clinical trial was conducted on twenty-six patients with acute CO poisoning. G-CSF (90 μg/kg) was administered intravenously for 72 h. Demographic data, routine laboratory tests, differential blood counts, venous blood gas, and adverse reactions were recorded. The primary endpoint was brain ischemia improvement based on CT findings and the secondary endpoints examined improvements in the modified Rankin Scale (mRS), National Institutes of Health Stroke Scale (NIHSS), and Barthel Index as well as S-100β concentrations. Fourteen patients received G-CSF, and 12 received a placebo. Twenty-six were followed for 30 days and no one in both groups died during follow-up. Neurological complications, brain ischemic changes, Barthel, and mRS were compared between the two groups on determined days after the onset of therapeutic intervention, and no significant differences were observed between the two groups. Favorable results were achieved for treated patients by different measures; NIHSS was decreased 72 h after treatment (p = 0.046), and S-100β levels were significantly higher in the G-CSF group than in the control group, 12 h and 72 h after the treatment. G-CSF appears to have potential effects on several clinical parameters in patients with acute CO poisoning. The trial was registered at the Iranian Registry of Clinical Trials with the ID: (IRCT201607232083N7).

An artificial intelligence algorithm for analyzing globus pallidus necrosis after carbon monoxide intoxication

Globus pallidus necrosis (GPN) is one of typical neurological imaging features in patients with carbon monoxide (CO) poisoning. Current clinical guideline recommends neurological imaging examination for CO-intoxicated patients with conscious disturbance rather than routine screening, which may lead to undiagnosed GPN. We aimed to develop an artificial intelligence algorithm for predicting GPN in CO intoxication patients. We included CO intoxication patients with neurological images between 2000 and 2019 in Chang Gung Memorial Hospital. We collected 41 clinical and laboratory parameters on the first day of admission for algorithm development. We used fivefold cross validation and applied several machine learning algorithms. Random forest classifier (RFC) provided the best predictive performance in our cohort. Among the 261 patients with CO intoxication, 52 patients presented with GPN. The artificial intelligence algorithm using the RFC-based AI model achieved an accuracy = 79.2 ± 2.6%, sensitivity = 77.7%, precision score = 81.9 ± 3.4%, and F1 score = 73.2 ± 1.8%. The area under receiver operating characteristic was approximately 0.64. Top five weighted variables were Platelet count, carboxyhemoglobin, Glasgow Coma scale, creatinine, and hemoglobin. Our RFC-based algorithm is the first to predict GPN in patients with CO intoxication and provides fair predictive ability. Further studies are needed to validate our findings.

A Review for In Vitro and In Vivo Detection and Imaging of Gaseous Signal Molecule Carbon Monoxide by Fluorescent Probes

Carbon monoxide (CO) is a vital endogenous gaseous transmitter molecule involved in the regulation of various physiological and pathological processes in living biosystems. In order to investigate the biological function of CO, many technologies have been developed to monitor the level of endogenous CO in biosystems. Among them, the fluorescence detection technology based on the fluorescent probe has the advantages of high sensitivity, excellent selectivity, simple operation, especially non-invasive damage to biological samples, and the possibility of real-time in situ detection, etc., which is considered to be one of the most effective and applicable detection techniques. Therefore, in the last few years, a lot of work has been carried out on the design, synthesis and in vivo fluorescence imaging studies of CO fluorescent probes. Furthermore, using fluorescent probes to detect the changes in CO concentrations in living cells and tissues as well as in organisms has been one of the hot research topics in recent years. However, it is still a challenge to rationally design CO fluorescent probe with excellent optical performance, structural stability, low background interference, good biocompatibility, and excellent water solubility. Therefore, this review focuses on the research progress of CO fluorescent probes in the detection mechanism and biological applications in recent years. However, this popular and leading topic has rarely been summarized comprehensively to date. Thus, the research progress of CO fluorescent probes in recent years is reviewed in terms of their design concept, detection mechanism, and their biological applications. In addition, the relationship between the structure and performance of the probes was also discussed. More significantly, we hope that more excellent optical properties fluorescent probes for gaseous transmitter molecule CO detection and imaging will overcome the current problems of high biotoxicity and limited water solubility in future.

Cell-free and alkylated hemoproteins improve survival in mouse models of carbon monoxide poisoning

I.v. administration of a high-affinity carbon monoxide-binding (CO-binding) molecule, recombinant neuroglobin, can improve survival in CO poisoning mouse models. The current study aims to discover how biochemical variables of the scavenger determine the CO removal from the RBCs by evaluating 3 readily available hemoproteins, 2,3-diphosphoglycerate stripped human hemoglobin (StHb); N-ethylmaleimide modified hemoglobin (NEMHb); and equine myoglobin (Mb). These molecules efficiently sequester CO from hemoglobin in erythrocytes in vitro. A kinetic model was developed to predict the CO binding efficacy for hemoproteins, based on their measured in vitro oxygen and CO binding affinities, suggesting that the therapeutic efficacy of hemoproteins for CO poisoning relates to a high M value, which is the binding affinity for CO relative to oxygen (KA,CO/KA,O2). In a lethal CO poisoning mouse model, StHb, NEMHb, and Mb improved survival by 100%, 100%, and 60%, respectively, compared with saline controls and were well tolerated in 48-hour toxicology assessments. In conclusion, both StHb and NEMHb have high CO binding affinities and M values, and they scavenge CO efficiently in vitro and in vivo, highlighting their therapeutic potential for point-of-care antidotal therapy of CO poisoning.

Risks of Developing Diabetes and Hyperglycemic Crisis Following Carbon Monoxide Poisoning: A Study Incorporating Epidemiologic Analysis and Animal Experiment

Purpose

Carbon monoxide (CO) poisoning may damage the pancreas, but the effects of CO poisoning on the development of diabetes and on existing diabetes remain unclear. We conducted a study incorporating data from epidemiologic analyses and animal experiments to clarify these issues.

Methods

Using the National Health Insurance Database of Taiwan, we identified CO poisoning patients diagnosed between 2002 and 2016 (CO poisoning cohort) together with references without CO poisoning who were matched by age, sex, and index date at a 1:3 ratio. We followed participants until 2017 and compared the risks of diabetes and hyperglycemic crisis between two cohorts using Cox proportional hazards regressions. In addition, a rat model was used to assess glucose and insulin levels in blood as well as pathological changes in the pancreas and hypothalamus following CO poisoning.

Results

Among participants without diabetes history, 29,141 in the CO poisoning cohort had a higher risk for developing diabetes than the 87,423 in the comparison cohort after adjusting for potential confounders (adjusted hazard ratio [AHR]=1.23; 95% confidence interval [CI]: 1.18–1.28). Among participants with diabetes history, 2302 in the CO poisoning cohort had a higher risk for developing hyperglycemic crisis than the 6906 in participants without CO poisoning (AHR = 2.12; 95% CI: 1.52–2.96). In the rat model, CO poisoning led to increased glucose and decreased insulin in blood and damages to pancreas and hypothalamus.

Conclusion

Our epidemiological study revealed that CO poisoning increased the risks of diabetes and hyperglycemic crisis, which might be attributable to damages in the pancreas and hypothalamus as shown in the animal experiments.

[Carbon monoxide intoxication-New aspects and current guideline-based recommendations]

Carbon monoxide poisoning is a common and potentially life-threatening intoxication, showing an interindividual variety of unspecific symptoms as well as late neurological and other sequelae. Two new German guidelines (S2k guidelines diagnosis and treatment of carbon monoxide poisoning as well as S3 guidelines oxygen therapy in the acute care of adult patients) focus on current evidence-based information on diagnostics as well as therapeutic options with considerable uncertainty remaining. This review summarizes current information and presents a flow scheme for daily practical use.

Association between carbon monoxide poisoning and adrenal insufficiency: a nationwide cohort study

Carbon monoxide poisoning may damage the brain and adrenal glands, but it is unclear whether it is associated with adrenal insufficiency. We identified all COP patients diagnosed between 1999 and 2012 in Taiwan using the Nationwide Poisoning Database and selected a reference cohort (participants without COP) from the same database by exact matching of age and index date at a 1:2 ratio. Participants with a history of adrenal insufficiency or steroid use of more than 14 days were excluded. We followed up participants until 2013 and compared the risk of developing adrenal insufficiency between the two cohorts. The 21,842 COP patients had a higher risk for adrenal insufficiency than the 43,684 reference participants (adjusted hazard ratio [AHR] = 2.5; 95% confidence interval [CI]: 1.8–3.5) after adjustment for sex and underlying comorbidities (liver disease, thyroid disease, mental disorder). The risk continued to elevate even after 1 year (AHR = 2.1; 95% CI: 1.4–3.4). The COP patients who had acute respiratory failure had an even higher risk for adrenal insufficiency than those without acute respiratory failure, which may indicate a dose–response relationship. Stratified analyses showed that female patients had an elevated risk (AHR = 3.5; 95% CI: 2.1–6.0), but not male patients. Younger patients (< 50 years) had higher risks, and the AHR reached statistical significance in the age groups 20–34 (AHR = 5.5; 95% CI: 1.5–20.6) and 35–49 (AHR = 4.9; 95% CI: 2.3–10.6) years old. The risk for developing adrenal insufficiency elevated after COP, especially in female and younger patients. Carbon monoxide is the most common gaseous agent causing acute intoxication worldwide. Results of the current study call for monitoring adrenal function of patients with COP.

Cyanine-flavonol hybrids as NIR-light activatable carbon monoxide donors in methanol and aqueous solutions

Here we report on carbon monoxide-photoreleasable compounds (photoCORMs) that combine heptamethine cyanine and flavonol chromophores and are activated upon irradiation with near-infrared light. Excellent CO-release yields and uncaging cross sections in aqueous solutions, enhanced water solubilities thanks to polar substituents or a host-guest approach using cucurbit[7]uril are demonstrated. The hybrids display outstanding biocompatibility and diverse, structure-dependent cell penetrability and internalization.

Study of the value of homocysteine levels in predicting cognitive dysfunction in patients after acute carbon monoxide poisoning

PURPOSE

The purpose of this research was to assess the value of homocysteine (HCY) levels in predicting cognitive dysfunction in patients after acute carbon monoxide (CO) poisoning.

METHODS

A total of 115 patients who were admitted to the emergency department of Yinzhou NO. 2 Hospital after CO poisoning between January 2017 and December 2021 were enrolled in this retrospective study. All patients were followed up for 1 month. According to the Mini-Mental State Examination (MMSE) scores, patients were divided into two groups. The demographic and clinical characteristics and magnetic resonance imaging (MRI) results were gathered and statistically analysed.

RESULTS

Twenty-six and 89 patients were ultimately enrolled in the cognitive dysfunction and control groups, respectively. There were significant differences between the groups in terms of age, coma duration, and carboxyhaemoglobin (COHB), lactate and HCY levels (p < 0.05), but there were no significant differences in white blood cell (WBC) counts or aspartate transaminase (AST), alanine transaminase (ALT), creatinine, troponin T, creatinine kinase (CK), or creatinine kinase muscle and brain (CK-MB) levels (p > 0.05). Univariate and multivariate analyses identified that a higher HCY level (OR 2.979, 95% CI 1.851-5.596, p < 0.001) was an independent risk factor for patient cognitive dysfunction after acute CO poisoning. Linear regression analysis showed a negative correlation between MMSE scores and HCY levels (r = - 0.880, P < 0.001). According to the MRI results, the most common lesion site was the globus pallidus, and the central ovale, diffuse white matter, corona radiata, basal ganglia (other than the globus pallidus) and cerebral cortex were also involved.

CONCLUSIONS

Higher HCY levels were associated with cognitive impairment and were independent risk factors for cognitive impairment after acute CO poisoning. The level of HCY was negatively correlated with the degree of cognitive impairment.

Should We Use Hyperbaric Oxygen for Carbon Monoxide Poisoning Management? A Network Meta-Analysis of Randomized Controlled Trials

Carbon monoxide (CO) poisoning is a public health issue in numerous countries. Oxygen supplementation is the standard and initial management for acute CO poisoning. Normobaric oxygen (NBO) and hyperbaric oxygen (HBO) therapies for CO poisoning have been discussed for several decades. NBO, one-session HBO, two-session HBO, and three-session HBO have not been clearly compared, although there are some syntheses. Therefore, this study aimed to provide an overview of various HBO therapies for CO poisoning. We searched online databases for randomized controlled trials (RCTs) on this topic, and two authors individually extracted data on characteristics, mortality, headache recovery, general fatigue, memory impairment, and difficulty concentrating. Outcomes were pooled using network meta-analysis. We included eight RCTs (n = 1785) that met our eligibility criteria. Pooled estimates showed that HBO had no better outcomes than NBO. Moreover, two-session HBO seemed to have a higher general fatigue rate than NBO, and compared with one-session HBO therapy, it had a higher fatigue rate (risk ratio (RR): 1.29, 95% confidence interval (CI): 1.03–1.62), memory impairment rate (RR = 1.80, 95% CI: 1.01–3.19), and concentration impairment rate (RR = 1.85, 95% CI: 1.19–2.89). HBO may be ineffective for patients with CO poisoning. Therefore, clinicians should consider the available treatment options carefully before recommending HBO to patients.

A Hemicyanine-Assembled Upconversion Nanosystem for NIR-Excited Visualization of Carbon Monoxide Bio-Signaling In Vivo

Carbon monoxide (CO) is considered as the second gasotransmitter involved in a series of physiological and pathological processes. Although a number of organic fluorescent probes have been developed for imaging CO, these probes display excitation within the ultraviolet or visible range, which restrict their applications in the complex biosystems. In the present work, a strategy is developed to construct an upconversion nanoparticles-based nanosystem for upconversion luminescent (UCL) sensing CO. This nanosystem exhibits a fast response to CO with high sensitivity and selectivity in aqueous solution by a near-infrared-excited ratiometric UCL detection method. Meanwhile, laser scanning upconversion luminescence microscope experiments demonstrate that this nanosystem can visualize the endogenous CO bio-signaling in living cells, deep tissues, zebrafish, and living mice by ratiometric UCL imaging. In particular, this nanosystem has been successfully employed in visualization of the endogenous CO bio-signaling through up-regulation of heme oxygenase-1 (HO-1) in the progression of hypoxia, acute inflammation, or ischemic injury. This work demonstrates that the outstanding performance of the nanosystem not only can provide an effective tool for further understanding the role of CO in the physiological and pathological environment, but also may have great potential ability for tracking the expression of HO-1 in living systems.

Validation of Diagnostic Codes to Identify Carbon Monoxide Poisoning in Taiwan’s Claims Data

Purpose: Previous studies identified the study cohort or outcome of carbon monoxide poisoning (COP) by using the relevant disease diagnosis codes in secondary databases, but the validity of diagnosis codes of COP is unclear in such secondary databases. This study aimed to evaluate the accuracy of case definitions for COP using the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) and Tenth Revision, Clinical Modification (ICD-10-CM) diagnosis codes in Taiwan’s health insurance claims data.

Methods: We selected a 10% simple random sample from an original cohort of patients newly undergoing carboxyhemoglobin (COHb) testing under any clinical diagnosis at four Chang Gung Memorial Hospitals in Taiwan during 2011–2020. Two clinical doctors independently ascertained the COP diagnosis by reviewing the medical records as the reference standard. We estimated the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of various case definitions (e.g., ICD-9-CM code, ICD-10-CM code and the uses of hyperbaric oxygen therapy) in the claims data.

Results: We randomly selected 557 cases from the original cohort of 5,571 cases newly receiving COHb test in the study hospitals. We found 90, 35, and 9 cases were true-positive, false-positive, and false-negative episodes of COP, respectively, among 278 cases with an ICD-9-CM code of 986. A further 111, 34, and 6 cases were true-positive, false-positive, and false-negative episodes of COP, respectively, among 279 cases with an ICD-10-CM code of T58. Using ICD-9-CM codes, the sensitivity, specificity, PPV and NPV for COP were 90.9, 80.4, 72, and 94.1%, respectively. Using ICD-10-CM codes they were 94.9, 79, 76.6, and 95.5%, respectively. PPV typically increased when COP was the primary diagnosis and could reach 100% if patients with ICD-CM code 986 or T58 also received hyperbaric oxygen therapy during hospitalization.

Conclusion: The COP-related ICD-CM codes alone did not accurately identify COP patients, but accuracy improved after including oxygen therapy data with the ICD-CM codes in Taiwan’s claims data.

Adsorption of Industrial Gases (CH4, CO2, and CO) on Olympicene: A DFT and CCSD(T) Investigation

Olympicene C₁₉H₁₂, an organic semiconductor, is investigated as an adsorption material for toxic industrial gas molecules such as CH₄, CO₂, and CO. A deep insight of complexation of CH₄, CO₂, and CO with olympicene (analyte@OLY) was obtained by interaction energy, symmetry-adopted perturbation theory (SAPT2+), quantum theory of atoms in molecules (QTAIM), density of states (DOS), noncovalent interaction (NCI), and frontier molecular orbital and natural bond orbital analysis. Domain-based local pair natural orbital coupled cluster theory single-point energy calculations were performed using the cc-pVTZ basis set in combination with corresponding auxiliary cc-pVTZ/JK and cc-pVTZ/C basis sets. For all property calculations of doped olympicene complexes, the ωB97M-V functional was employed. The stability trend for interaction energies is CO₂@OLY > CH₄@OLY > CO@OLY. QTAIM and NCI analysis confirmed the presence of NCIs, where the dispersion factor (in CH₄@OLY) has the highest contribution, as revealed from SAPT2+. The chemical sensitivity of the system was evidenced by the origination of new energy states in DOS spectra. The recovery time for the analyte@OLY complex was calculated at 300 K, and an excellent recovery response was observed. All results evidently indicated weak interactions of the olympicene surface with CH₄, CO₂, and CO.

Glutamate Chemical Exchange Saturation Transfer (GluCEST) Magnetic Resonance Imaging of Rat Brain With Acute Carbon Monoxide Poisoning

OBJECTIVES

To evaluate the diagnostic and prognostic values of glutamate chemical exchange saturation transfer (GluCEST) magnetic resonance imaging as a quantitative method for pathogenetic research and clinical application of carbon monoxide (CO) poisoning-induced encephalopathy combined with the proton magnetic resonance spectroscopy (¹H-MRS) and the related histopathological and behavioral changes.

METHODS

A total of 63 Sprague-Dawley rats were randomly divided into four groups. Group A (n = 12) was used for animal modeling verification; Group B (n = 15) was used for magnetic resonance molecular imaging, Group C (n = 15) was used for animal behavior experiments, and Group D (n = 21) was used for histopathological examination. All the above quantitative results were analyzed by statistics.

RESULTS

The peak value of carboxyhemoglobin saturation in the blood after modeling was 7.3-fold higher than before and lasted at least 2.5 h. The GluCEST values of the parietal lobe, hippocampus, and thalamus were significantly higher than the base values in CO poisoning rats (p < 0.05) and the ¹H-MRS showed significant differences in the parietal lobe and hippocampus. In the Morris water maze tests, the average latency and distance were significantly prolonged in poisoned rats (p < 0.05), and the cumulative time was shorter and negatively correlated with GluCEST.

CONCLUSION

The GluCEST imaging non-invasively reflects the changes of glutamate in the brain in vivo with higher sensitivity and spatial resolution than ¹H-MRS. Our study implies that GluCEST imaging may be used as a new imaging method for providing a pathogenetic and prognostic assessment of CO-associated encephalopathy.

Oxygenation Performance of Different Non-Invasive Devices for Treatment of Decompression Illness and Carbon Monoxide Poisoning

Study Objective: Application of high concentrations of oxygen to increase oxygen partial pressure (pO2) is the most important treatment for patients with carbon monoxide intoxication or divers with suspected decompression illness. The aim of this study was to evaluate the oxygenation performance of various non-invasive oxygen systems.

Methods: The effect of different oxygen systems on arterial pO2, pCO2 and pH and their subjective comfort was evaluated in 30 healthy participants. Eight devices were included: nasal cannula, non-rebreather mask, AirLife Open mask, Flow-Safe II CPAP device, SuperNO₂VA nasal PAP device, all operated with 15 L/min constant flow oxygen; nasal high-flow (50 L/min flow, 1.0 FiO2), non-invasive positive pressure ventilation (NPPV, 12 PEEP, 4 ASB, 1.0 FiO2) and a standard diving regulator (operated with pure oxygen).

Results: Diving regulator, SuperNO₂VA, nasal high-flow and NPPV achieved mean arterial pO2 concentrations between 538 and 556 mm Hg within 5 minutes. The AirLife Open mask, the nasal cannula and the non-rebreather mask achieved concentrations of 348–451 mm Hg and the Flow-Safe II device 270 mm Hg. Except for the AirLife open mask, pCO2 decreased and pH increased with all devices. The highest pH values were observed with NPPV, diving regulator, Flow-Safe II and nasal high-flow but apparent hyperventilation was uncommon. The AirLife Open and the non-rebreather mask were the most comfortable, the SuperNO₂VA and the nasal cannula the most uncomfortable devices.

Conclusion: A standard diving regulator and the SuperNO₂VA device were equally effective in providing highest physiologically possible pO2 as compared to nasal high-flow and NPPV.

Neurological sequelae in acute carbon monoxide poisoning: A prospective observational study with MRI data

OBJECTIVES

Acute carbon monoxide (CO) poisoning survivors may experience persistent neurological sequelae (PNS) and delayed neurological sequelae (DNS). This study evaluated the clinical features, laboratory results, acute brain lesions (ABLs) on diffusion-weighted imaging (DWI) at presentation, and long-term outcomes and explored differences between patients with PNS and DNS.

METHODS

The study included 443 patients who had experienced CO poisoning, underwent DWI and completed 1-year follow-ups. The demographics, comorbidities, symptomatology, laboratory results, ABLs on DWI at presentation, and long-term outcomes were compared between patients with PNS and those with DNS.

RESULTS

The 42 (9.5%) and 96 (21.7%) patients with PNS and DNS, respectively, showed no significant differences in demographics, duration of CO exposure, initial conscious level, symptomatology, and laboratory results. ABLs on DWI were observed in 33 patients (33/42) with PNS and 62 patients (62/96) with DNS. The most common region of ABLs was the globus pallidus (60.6% and 56.6% in PNS and DNS, respectively). The proportion of ABLs present and lesion distribution did not differ significantly between the two groups. At 1 year, a significantly higher proportion of patients in the PNS group showed a good outcome (defined as modified Rankin Scale [mRS] scores of 0-2, 81%) compared with the DNS group (81% vs. 56.3%, p = .047).

CONCLUSION

Demographics, clinical features, laboratory results, and acute brain lesions on MRI at presentation did not differ between the PNS and DNS groups. However, the long-term outcome of PNS was better than that of DNS.

Towards Personalization of Indoor Air Quality: Review of Sensing Requirements and Field Deployments

As humans spend more time indoors, ensuring acceptable indoor air quality (IAQ) through ubiquitous sensing systems has become a necessity. Although extensive studies have been conducted on the IAQ sensing systems, a holistic review of the performance and deployment of Ubiquitous IAQ Sensing (UIAQS) systems with associated requirements in IAQ sensing standards is still lacking. In this study, we first reviewed IAQ pollutants and other IAQ-related factors and the associated requirements in the prominent IAQ sensing standards. We found that while non-pollutant factors are influential on occupants' perception of IAQ and their satisfaction, they do not have evaluation metrics in the IAQ standards. Then, we systematically reviewed field studies on UIAQS technologies in the literature. Specific classes of information were recorded and analyzed further. We found that the majority of the UIAQS systems did not meet the requirements of the prominent IAQ sensing standards and identified four primary research gaps. We concluded that a new holistic and personalized approach that incorporates UIAQS measurements and subjective feedback is needed. This study provides valuable insights for researchers and policymakers to better improve UIAQS technologies by developing personalized IAQ sensors and sensing standards.

Trends in carbon monoxide poisoning deaths in high frequency hurricane states from 2014-19: the need for prevention intervention strategies

INTRODUCTION

Hurricanes often result in power outages, which increase generator usage and carbon monoxide (CO) deaths. We aim to identify states with the highest frequency of hurricanes and evaluate the number of unintentional CO poisoning deaths by region, age, race and metropolitan distribution.

METHODS

The number of hurricanes was determined using the FEMA database, and the number of unintentional CO poisoning deaths was determined using the CDC WONDER database from 2014-19. Hurricane-associated consumer outages were obtained from the Department of Energy.

RESULTS

The number of unintentional CO poisoning deaths was as follows: Florida, South Carolina, North Carolina, Georgia and Alabama. Adults displayed a significantly higher number of unintentional CO poisoning deaths than pediatrics (P < 0.001). The total number of unintentional CO poisoning deaths was highest in the White population (P < 0.001); however, unintentional CO poisoning death rates were nearly two times higher among Black population in adults (0.5 versus 0.3) and pediatrics (0.2 versus 0.1). Medium metropolitan areas exhibited significantly more unintentional CO poisoning deaths (P < 0.001).

CONCLUSIONS

Hurricanes and unintentional CO poisoning deaths were most common in Florida. Death rates were higher among Black individuals. Medium metropolitan areas displayed significantly more unintentional CO poisoning deaths than all other areas.

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.

Thoracic Society of Australia and New Zealand Position Statement on Acute Oxygen Use in Adults: 'Swimming between the flags'

Oxygen is a life-saving therapy but, when given inappropriately, may also be hazardous. Therefore, in the acute medical setting, oxygen should only be given as treatment for hypoxaemia and requires appropriate prescription, monitoring and review. This update to the Thoracic Society of Australia and New Zealand (TSANZ) guidance on acute oxygen therapy is a brief and practical resource for all healthcare workers involved with administering oxygen therapy to adults in the acute medical setting. It does not apply to intubated or paediatric patients. Recommendations are made in the following six clinical areas: assessment of hypoxaemia (including use of arterial blood gases); prescription of oxygen; peripheral oxygen saturation targets; delivery, including non-invasive ventilation and humidified high-flow nasal cannulae; the significance of high oxygen requirements; and acute hypercapnic respiratory failure. There are three sections which provide (1) a brief summary, (2) recommendations in detail with practice points and (3) a detailed explanation of the reasoning and evidence behind the recommendations. It is anticipated that these recommendations will be disseminated widely in structured programmes across Australia and New Zealand.

A Critical Review on Organic Small Fluorescent Probes for Monitoring Carbon Monoxide in Biology

Endogenous carbon monoxide (CO) is an important intracellular gas messenger that is intimately involved in many physiological and pathological processes. The abnormal concentration of CO in living organisms can cause many diseases. Therefore, it is of great significance to monitor CO in biological samples. Fluorescent probe technology provides an effective and convenient method for CO monitoring, with the advantages of high selectivity and sensitivity, fast response time and in situ fluorescence imaging in biological tissues, which is favored by the majority of researchers. In this paper, the research progress of CO fluorescent probes since 2018 is reviewed, and the design, detection mechanism and biological application of the related fluorescent probes are summarized. And the relationship between the structure and performance of the probes is discussed. Furthermore, the development trend and application prospect of CO fluorescent probes are prospected.

Early neuroimaging and delayed neurological sequelae in carbon monoxide poisoning: a systematic review and meta-analysis

We aimed to assess the evidence regarding the usefulness of brain imaging as a diagnostic tool for delayed neurological sequelae (DNS) in patients with acute carbon monoxide poisoning (COP). Observational studies that included adult patients with COP and DNS were retrieved from Embase, MEDLINE, and Cochrane Library databases in December 2020 and pooled using a random-effects model. Seventeen studies were systematically reviewed. Eight and seven studies on magnetic resonance imaging (MRI) and computed tomography (CT), respectively, underwent meta-analysis. The pooled sensitivity and specificity of MRI for diagnosis of DNS were 70.9% (95% confidence interval [CI] 64.8–76.3%, I² = 0%) and 84.2% (95% CI 80.1–87.6%, I² = 63%), respectively. The pooled sensitivity and specificity of CT were 72.9% (95% CI 62.5–81.3%, I² = 8%) and 78.2% (95% CI 74.4–87.1%, I² = 91%), respectively. The areas under the curve for MRI and CT were 0.81 (standard error, 0.08; Q* = 0.74) and 0.80 (standard error, 0.05, Q* = 0.74), respectively. The results indicate that detecting abnormal brain lesions using MRI or CT may assist in diagnosing DNS in acute COP patients.