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

Advancing the symptom science model with environmental health

OBJECTIVE

Globally, indoor and outdoor pollutants are leading risk factors for death and reduced quality of life. Few theories explicitly address environmental health within the nursing discipline with a focus on harmful environmental exposures. The objective here is to expand the National Institutes of Health Symptom Science Model to include the environmental health concepts of environmental endotype (causative pathway) and environmental exposure.

DESIGN

Meleis' research to theory strategy for theory refinement was used. Research workshop proceedings, environmental health nursing research expert consensus, panelist research trajectories, and review of the literature were utilized as data sources.

RESULTS

Ongoing emphasis on the physical environment as a key determinant of health and theoretical perspectives for including environmental exposures and endotypes in symptom science are presented. Definitions of these concepts, further developed, are provided. Recommendations to strengthen environmental health nursing research and practice through capacity building/infrastructure, methods/outcomes, translational/clinical research, and basic/mechanistic research are included.

CONCLUSION

The revised model deepens theoretical support for clinical actions that include environmental modification, environmental health education, and exposure reduction. This modification will enable a middle-range theory and shared mental model to inspire the prioritization of environmental health in nursing leadership, research, practice, and education.

The Effect of a 30-Min Water-Pipe Smoking Session on Cognitive Measures and Cardio-Pulmonary Parameters

Introduction

One session of water-pipe tobacco smoking (WPS) can increase carboxyhemoglobin (COHb) to levels comparable to those reported in carbon monoxide poisoning, which may cause memory impairment and confusion.

Methods

A prospective study evaluating healthy volunteers pre- and post-30 min of WPS session. Primary outcome parameters were executive cognitive measures [digit span test and Paced Auditory Serial Addition Test (PASAT)]. The effect of repeated cognitive testing 30 min apart without WPS was evaluated in age- and sex-matched healthy volunteers. Secondary outcome parameters included cardio-pulmonary, COHb, serum nicotine, and cytokine changes.

Results

Thirty-five subjects aged 25.6 ± 4.5 years smoked water-pipe for a 30-min session. Control group included 20 subjects aged 25.2 ± 5.1 years. Digit span test median score decreased after WPS (16 and 15, respectively, p = .003), insignificant decrease in controls. Median PASAT score increased after WPS (49 and 52, respectively, p = .009); however, a much larger significant increase was observed in controls (p ≤ .001). One WPS session resulted in significant increases in heart and respiratory rates and significant decrease in FEF25–75%. Post WPS, median COHb levels increased (from 2.2% to 10.7%, p < .0001) as did median serum nicotine levels (from 1.2 to 26.8 ng/mL, p < .0001). Serum cytokines levels: IL-2 and IL-6 increased (p < .0001 for each), and IL-10 and IL-5 decreased (p < .0001 and p = .04, respectively).

Conclusions

One session of WPS resulted in significant negative effects on cognitive executive measures, significant increases in COHb and serum nicotine levels, and significant changes in serum cytokines. Our findings call for increasing awareness towards the possible consequences of cognitive alterations following a 30-min session of WPS.

Implications

One 30-min session of water-pipe smoking resulted in negative effects on executive cognitive measures, increased carboxyhemoglobin and serum nicotine, and significant changes in serum cytokine levels. This study adds to the accumulating evidence on the harmful effects of water-pipe smoking, a growing epidemic, and calls for awareness of its possible consequences of acute cognitive alterations.

The role of fuel type and combustion phase on the toxicity of biomass smoke following inhalation exposure in mice

The characteristics of wildland fire smoke exposures which initiate or exacerbate cardiopulmonary conditions are unclear. We previously reported that, on a mass basis, lung toxicity associated with particulate matter (PM) from flaming smoke aspirated into mouse lungs is greater than smoldering PM. In this study, we developed a computer-controlled inhalation system which can precisely control complex biomass smoke emissions from different combustion conditions. This system was used to examine the toxicity of inhaled biomass smoke from peat, eucalyptus, and oak fuels generated under smoldering and flaming phases with emissions set to the same approximate concentration of carbon monoxide (CO) for each exposure (60-110 ppm), resulting in PM levels of ~ 4 mg/m³ for flaming and ~ 40 mg/m³ for smoldering conditions. Mice were exposed by inhalation 1 h/day for 2 days, and assessed for lung toxicity at 4 and 24 h after the final exposure. Peat (flaming and smoldering) and eucalyptus (smoldering) smoke elicited significant inflammation (neutrophil influx) in mouse lungs at 4 h with the peat (flaming) smoke causing even greater lung inflammation at 24-h post-exposure. A significant alteration in ventilatory timing was also observed in mice exposed to the peat (flaming) and eucalyptus (flaming and smoldering) smoke immediately after each day of exposure. No responses were seen for exposures to similar concentrations of flaming or smoldering oak smoke. The lung toxicity potencies (neutrophil influx per PM mass) agreed well between the inhalation and previously reported aspiration studies, demonstrating that although flaming smoke contains much less PM mass than smoldering smoke, it is more toxic on a mass basis than smoldering smoke exposure, and that fuel type is also a controlling factor.

A case of delayed neurological manifestation following carbon monoxide poisoning in Sri Lanka: epidemiology of exposure and literature review

BACKGROUND

Carbon monoxide poisoning is a common emergency worldwide, which carries high morbidity and mortality. Some patients who recover from the insult of acute carbon monoxide toxicity may later develop delayed neuropsychiatric sequelae (DNS) after a lucid period in the form of cognitive impairments, a broad spectrum of neurological deficits and affective disorders. Here, we present the first case of DNS following carbon monoxide poisoning in Sri Lanka and epidemiology of the exposure of nine (9) more victims.

CASE PRESENTATION

A 55-year-old patient and nine other people developed effects of carbon monoxide poisoning in two different occasions after sleeping few hours in the same room in their work place in Sri Lanka. These patients developed spectrum of symptoms with the acute carbon monoxide poisoning. However, one patient developed neurological deterioration pertaining to delayed neuropsychiatric sequelae (DNS) after 1 month of lucid interval. His MRI scan of the brain showed diffuse high signal intensity involving subcortical white matter, globus pallidus on FLAIR and T2W images. These areas showed high signals in DWI images with no significant changes appreciated on ADC map. There was no abnormal contrast enhancement appreciated in the above areas. EEG showed generalized slow waves. He gradually deteriorated over next 2 weeks, exhibited athetoid movements of his feet and hands and went into rigid akinetic mute state. He could not response to any stimulation and even displayed decorticated-like posture and died. Others had normal MRI brain finding at 8 weeks of acute toxicity and all were neurologically normal after 1 year.

CONCLUSION

Though, it is uncommon in a tropical country like Sri Lanka, clinicians should have high degree of suspicion with the correct circumstances, as it is a challenge for the emergency physicians, even in countries with higher rate of CO poisoning. The exact mechanisms of acute and delayed toxicity, preventive methods and the suggested treatments are yet to be elucidated and this needs further attention and studies.

[Treatment of carbon monoxide poisoning in Germany : A retrospective single center analysis]

BACKGROUND

The symptoms of acute carbon monoxide (CO) poisoning are unspecific, ranging from headaches to unconsciousness and death. In addition to acute symptoms, delayed severe neurological sequelae may occur. While a total of 440 deaths by CO poisoning were registered in Germany in 1999, a total of 594 patients died (0.73 per 100,000 inhabitants) in 2014 and in 2015 the number even increased to 648 deaths. A national database on clinical symptoms, course of illness or quality of care concerning CO poisoning does not yet exist.

METHODS

The treatment data of patients admitted to the Hyperbaric Emergency Centre Wiesbaden (HEC) from 2013 to 2017 with CO poisoning formed the basis of the study. This was a comparative evaluation of patient demographics, poisoning sources, symptom spectrum, course of treatment and time intervals registered on the preclinical and clinical levels.

RESULTS

From 2013 to 2017 a total of 476 patients (282 men and 194 women) with an average non-invasively measured CO-Hb of 15% (Q_0.25 = 7.6%, Q_0.75 = 22.3%) were treated with hyperbaric oxygen. Heaters (n = 131), charcoal barbecues (n = 93), fires (n = 90), hookahs (n = 78) and combustion engines (n = 37) were the most frequent CO sources identified. Headaches, vertigo, nausea and syncope were the most prevalent symptoms. A median of 91 min (Q_0.25 = 53 min; Q_0.75 = 147 min) passed between first medical contact and BGA-validated diagnosis. In total, 151 patients were transferred directly to the HEC, whereas 325 patients were secondarily transferred. The delay in this subgroup took 183 min (median Q_0.25 = 138 min; Q_0.75 = 248 min). After receiving the first hyperbaric treatment, 80% were free of symptoms. Remaining symptoms included headache (10%), fatigue (8%), vertigo (5%) and nausea (3%) and 45 patients terminated further treatment. Of the patients 417 received a second hyperbaric treatment and 370 patients were treated 3 times. After the third treatment, 89% were free of symptoms and 5% still reported headaches, 3% vertigo and 2% fatigue. In total, 6 patients died and 430 patients were symptom-free after treatment.

CONCLUSION

Commonly known sources (fire, charcoal grills) aside, many poisonings by smoking a hookah were observed. This study highlights the importance of considering CO poisoning as a differential diagnosis when encountering patients, especially of younger age, with non-specific neurological symptoms, as well as the importance of early initiation of treatment. A direct correlation between CO-Hb values (whether measured noninvasively or by invasive BGA) and the initial symptoms could not be demonstrated. In total, substantial time expired between the diagnosis and start of treatment of patients transported to a primary care hospital compared to those transported directly to the HEC. Although analysis showed adequate treatment with oxygen in the preclinical interval, administration of oxygen during primary hospital stay showed room for improvement. Introducing a national CO poisoning register and uniform treatment guidelines could improve in-house clinical processes. Multicenter studies are needed to close the gaps identified in the quality of care in Germany.

The neuroprotective effect of hyperoxygenate hydrogen-rich saline on CO-induced brain injury in rats

This study was designed to investigate the neuroprotective effect of hyperoxygenate hydrogen-rich saline (HOHS) against brain injury induced by carbon monoxide (CO) poisoning in rats. A rat model of CO poisoning was established by administering CO via intraperitoneal injection to male Sprague-Dawley rats. Forty-eight adult male rats were randomly divided into the following groups: normal control group (NG), CO poisoning group (CO), HOS treatment group (hyperoxygenated solution, HOS) and HOHS treatment group (HOHS). After CO poisoning, the carboxyhemoglobin (COHb) contents in the blood of rats in all the CO poisoning groups were increased significantly. However, HOS and HOHS significantly decreased COHb contents, furthermore, the HOHS group had lower COHb contents than the HOS group. Arterial oxygen partial pressure (PaO₂) and arterial oxygen saturation (SaO₂) results showed that HOS and HOHS could improve the oxygenation of the rats with CO poisoning. Compared with the CO group, the HOS group and the HOHS group had persistently neuroprotective effect on CO-induced brain injury, as assessed by modified neurological severity score (mNSS), furthermore, the HOHS group had better neurological functional recovery than the HOS group. The neuronal apoptosis induced by CO was also evaluated. Except the NG group, all the CO-poisoning groups had varying degrees of neuronal apoptosis. There was lesser degree of neuronal apoptosis in both the HOS group and the HOHS group than that in the CO group. Moreover, the HOHS group had more minor degree of neuronal apoptosis than the HOS group. Compared with the CO group, the free radicals production in the HOS group and the HOHS group were significantly inhibited. In addition, there were significantly difference in the free radicals production between the HOS group and the HOHS group. We could conclude that HOHS exerted a stronger neuroprotective effect against CO-induced brain injury than HOS, and the neuroprotective mechanism of HOHS may be related with inhibition of both neuronal apoptosis and free radicals.

Therapeutic effect of carbon monoxide-releasing molecule-3 on acute lung injury after hemorrhagic shock and resuscitation

Hemorrhagic shock and resuscitation (HSR) induces a pulmonary inflammatory response and frequently causes acute lung injury. Carbon monoxide-releasing molecule-3 (CORM-3) has been reported to liberate and deliver CO under physiological conditions, which exerts organ-protective effects during systemic insults. The present study aimed to determine whether the administration of CORM-3 following HSR exerts a therapeutic effect against HSR-induced lung injury without any detrimental effects on oxygenation and hemodynamics. To induce hemorrhagic shock, rats were bled to a mean arterial blood pressure of 30 mmHg for 45 min and then resuscitated with the shed blood. CORM-3 or a vehicle was intravenously administered immediately following the completion of resuscitation. The rats were divided into four groups, including sham, HSR, HSR/CORM-3 and HSR/inactive CORM-3 groups. Arterial blood gas parameters and vital signs were recorded during HSR. The histopathological changes to the lungs were evaluated using a lung injury score, while pulmonary edema was evaluated on the basis of the protein concentration in bronchoalveolar lavage fluid and the lung wet/dry ratio. We also investigated the pulmonary expression levels of inflammatory mediators and apoptotic markers such as cleaved caspase-3 and transferase-mediated dUTP-fluorescein isothiocyanate nick-end labeling (TUNEL) staining. Although HSR caused significant lung histopathological damage and pulmonary edema, CORM-3 significantly ameliorated this damage. CORM-3 also attenuated the HSR-induced upregulation of tumor necrosis factor-α, inducible nitric oxide synthase and interleukin-1β genes, and the expression of interleukin-1β and macrophage inflammatory protein-2. In addition, the expression of interleukin-10, an anti-inflammatory cytokine, was inversely enhanced by CORM-3, which also reduced the number of TUNEL-positive cells and the expression of cleaved caspase-3 following HSR. Although CORM-3 was administered during the acute phase of HSR, it did not exert any influence on arterial blood gas analysis data and vital signs during HSR. Therefore, treatment with CORM-3 ameliorated HSR-induced lung injury, at least partially, through anti-inflammatory and anti-apoptotic effects, without any detrimental effects on oxygenation and hemodynamics.

Poison severity score and sequential organ failure assessment score: Carbon monoxide poisoning prognosis

Purpose

We aimed to examine the utility of the Poison Severity Score (PSS) and Sequential Organ Failure Assessment (SOFA) score as early prognostic predictors of short-term outcomes in patients with carbon monoxide (CO) poisoning. We hypothesized that both the PSS and the SOFA score would be useful prognostic tools.

Methods

This was retrospective observational study of patients with CO poisoning who presented to the emergency department and were admitted for more than 24 hours. We calculated PSS, the initial SOFA score, a second (2^nd) SOFA score, and a 24-hour delta SOFA score. The primary outcome was reported as the cerebral performance category (CPC) scale score at discharge. We classified those with CPC 1–2 as the good outcome group and those with CPC 3–5 as the poor outcome group.

Results

This study included 192 patients: 174 (90.6%) belonged to the good outcome group, whereas 18 (9.4%) belonged to the poor outcome group. The PSS (1.00 [0.00, 1.00] vs 3.00 [3.00, 3.00], p < 0.001), initial SOFA (1.00 [0.00, 2.00] vs 4.00 [3.25, 6.00], p < 0.001), 2^nd SOFA score (0.00 [0.00, 1.00] vs 4.00 [3.00, 7.00], p < 0.001), and 24-hour delta SOFA score (-1.00 [-1.00, 0.00] vs 0.00 [-1.00, 1.00], p = 0.047) of the good outcome group were significantly higher than those of the poor outcome group. The areas under the receiver operating characteristic curve for PSS and the initial SOFA and 2^nd SOFA scores were 0.977 (95% confidence interval [CI] 0.944–0.993), 0.945 (95% CI 0.903–0.973), and 0.978 (95% CI 0.947–0.994), respectively.

Conclusion

The PSS, initial SOFA score, and 2^nd SOFA score predict acute poor outcome accurately in patients with CO poisoning.

[Evaluation and assessment of the health care process in patients with carbon monoxide poisoning in Germany]

BACKGROUND

Carbon monoxide poisoning (COP) is the most common cause for poisoning by inhalation in Germany. In the past 8 years, a marked increase in the number of COP-related deaths has been registered nationwide. A national German guideline is missing.

METHODS

The national and international literature was screened systematically. Existing international guidelines and expert recommendations for the diagnosis and treatment of COP were compared and evaluated. Furthermore, quality of health care was analyzed by a prospective preclinical dataset of emergency rescue services and retrospective analysis of routine data from 2014 to 2016 in Germany.

RESULTS

There is not a single evidence-based guideline worldwide. We determined 8 key performance indicators based on the five recommendations available for treatment of COP. These indices were subdivided into prehospital terms, hospital facilities, and diagnostic and therapeutic measures performed; they act as indicators for quality of care. In particular, the key figure "start oxygen" revealed that up to 41 % of the patients had not been treated with inhaled oxygen. In summary, data capture showed considerable incompleteness that is mainly due to missing time stamps.

CONCLUSION

In order to achieve a consistent treatment of patients with COP which meets the standard of recommended care, there is an urgent need for a consented national guideline. Another objective is to establish a nationwide prospective registry evaluating the treatment of carbon monoxide poisoning.

Hyperbaric oxygen therapy and mortality from carbon monoxide poisoning: A nationwide observational study

BACKGROUND

The effects of hyperbaric oxygen therapy (HBOT) on mortality or morbidity in patients with carbon monoxide (CO) poisoning remain unknown. We examined the effects of HBOT on CO poisoning and further strived to delineate its inherent effects on specific subgroups of patients using a nationwide inpatient database.

METHODS

We identified adult patients with CO poisoning who were registered in the Japanese Diagnosis Procedure Combination inpatient database from 2010 to 2016. Propensity score-matching was performed to compare patients who received HBOT within 1 day of admission (HBOT group) with those who did not receive HBOT (control group). The primary outcome was in-hospital mortality. The secondary outcomes were a depressed mental status and reduced activities of daily living (ADL) at discharge. We also performed subgroup analyses divided according to severity of CO poisoning.

RESULTS

Eligible patients were categorized into the HBOT group (n = 2034) or the control group (n = 4701). One-to-one propensity score-matching created 2034 pairs. In-hospital mortality was not significantly different between the HBOT and control groups (0.8% vs. 1.2%, risk difference: -0.4%, 95% confidence interval: -1.0 to 0.2). Patients in the HBOT group had significantly lower proportions of a depressed mental status and reduced ADL at discharge than did those in the control group. Similar associations were shown in the non-severe poisoning subgroup.

CONCLUSIONS

Although HBOT was not significantly associated with reduced mortality, it was significantly associated with a favorable consciousness level and ADL in patients with CO poisoning. HBOT may be beneficial even for patients with non-severe CO poisoning.

Sources of Vascular Nitric Oxide and Reactive Oxygen Species and Their Regulation

Nitric oxide (NO) is a small free radical with critical signaling roles in physiology and pathophysiology. The generation of sufficient NO levels to regulate the resistance of the blood vessels and hence the maintenance of adequate blood flow is critical to the healthy performance of the vasculature. A novel paradigm indicates that classical NO synthesis by dedicated NO synthases is supplemented by nitrite reduction pathways under hypoxia. At the same time, reactive oxygen species (ROS), which include superoxide and hydrogen peroxide, are produced in the vascular system for signaling purposes, as effectors of the immune response, or as byproducts of cellular metabolism. NO and ROS can be generated by distinct enzymes or by the same enzyme through alternate reduction and oxidation processes. The latter oxidoreductase systems include NO synthases, molybdopterin enzymes, and hemoglobins, which can form superoxide by reduction of molecular oxygen or NO by reduction of inorganic nitrite. Enzymatic uncoupling, changes in oxygen tension, and the concentration of coenzymes and reductants can modulate the NO/ROS production from these oxidoreductases and determine the redox balance in health and disease. The dysregulation of the mechanisms involved in the generation of NO and ROS is an important cause of cardiovascular disease and target for therapy. In this review we will present the biology of NO and ROS in the cardiovascular system, with special emphasis on their routes of formation and regulation, as well as the therapeutic challenges and opportunities for the management of NO and ROS in cardiovascular disease.

Carbon monoxide poisoning in Denmark with focus on mortality and factors contributing to mortality

Introduction

Carbon monoxide (CO) poisoning is frequent worldwide but knowledge regarding the epidemiology is insufficient. The aim of this study was to clarify the extent of this intoxication, its mortality and factors associated with mortality.

Materials and methods

National databases from Statistics Denmark were used to identify individuals who suffered from CO-poisoning during 1995–2015, as well as information regarding co-morbidities, mortality and manner of death.

Results

During the period from 1995 to 2015, 22,930 patients suffered from CO-poisoning in Denmark, and 21,138 of these patients (92%) were hospitalized. A total of 2,102 patients died within the first 30 days after poisoning (9.2%). Among these, 1,792 (85% of 2,102) were declared dead at the scene and 310 (15% of 2,102) died during hospitalization. Deaths due to CO-poisoning from smoke were intentional in 6.3% of cases, whereas deaths due to CO containing gases were intentional in 98.0% of cases. Among patients who survived >30 days, there was no significant difference in survival when comparing hyperbaric oxygen therapy (HBO) treatment with no HBO treatment after adjustment for age and co-morbidities such as drug abuse, psychiatric disease, stroke, alcohol abuse, arterial embolism, chronic obstructive pulmonary disease, cerebrovascular disease and atrial fibrillation. Several co-morbidities predicted poorer outcomes for patients who survived the initial 30 days.

Conclusions

Poisoning from smoke and/or CO is a frequent incident in Denmark accounting for numerous contacts with hospitals and deaths. Both intoxication and mortality are highly associated with co-morbidities interfering with cognitive and physical function. Treatment with HBO was not seen to have an effect on survival.

Clinical Predictors of Acute Brain Injury in Carbon Monoxide Poisoning Patients With Altered Mental Status at Admission to Emergency Department

OBJECTIVES

Objective screening tool for patients at a high risk of developing acute brain injury (ABI) is necessary for the proper treatment of carbon monoxide (CO) poisoning patients. The aim of this study is to identify clinical factors that could predict ABI due to CO poisoning in patients with an altered mental status.

METHODS

A prospectively collected CO poisoning registry at a single academic medical center was retrospectively analyzed. CO poisoning patients with an altered mental status at the emergency department, defined as unalert on the alert/responsive to voice/responsive to pain/unresponsive scale and underwent diffusion-weighted magnetic resonance imaging (DW-MRI) between January 1, 2013, and December 31, 2015, were included. ABI was defined as the presence of acute hypoxic brain lesions. Clinical predictors of ABI were identified by multivariate logistic regression analysis.

RESULTS

Of 180 patients, 67 (37.2%) had ABI as revealed by DW-MRI. Multivariate analysis showed that CO exposure duration > 5 hours (adjusted odds ratio [AOR] = 7.082; 95% confidence interval [CI] = 3.463-15.014; p < 0.001) defined as the time between CO exposure and rescue, abnormal white blood cell count (AOR = 2.568, 95% CI = 1.188-5.700, p = 0.02), and abnormal creatinine concentration (AOR = 2.667, 95% CI = 1.110-6.605, p = 0.03) were predictors of ABI. CO exposure duration had the highest predictive value (area under the curve, 0.815), and the optimal cutoff value was 5 hours. Moreover, increasing exposure durations (quartile) indicated a stepwise increase in the risk of ABI.

CONCLUSIONS

In CO poisoning patients with an altered mental status, CO exposure duration was useful for predicting ABI, which may help clinicians or paramedics identify high-risk patients and provide treatment on priority.

Magnesium sulfate ameliorates carbon monoxide‑induced cerebral injury in male rats

Carbon monoxide (CO) has been shown to induce several cardiovascular abnormalities, as well as necrosis, apoptosis and oxidative stress in the brain. Magnesium sulfate (MS) has been shown to have beneficial activities against hypoxia in the brain. In the present study, the possible protective effects of MS against CO‑induced cerebral ischemia were investigated. For this purpose, 25 male Wistar rats were exposed to 3,000 ppm CO for 1 h. The animals were divided into 5 groups (n=5 in each group) as follows: The negative control group (not exposed to CO), the positive control group (CO exposed and treated with normal saline), and 3 groups of CO‑exposed rats treated with MS (75, 150 and 300 mg/kg/day) administered intraperitoneally for 5 consecutive days. On the 5th day, the animals were sacrificed and the brains were harvested for the evaluation of necrosis, apoptosis and oxidative stress. Histopathological evaluation revealed that MS reduced the number and intensity of necrotic insults. The Bax/Bcl2 ratio and malondialdehyde (MDA) levels were significantly decreased in a dose‑dependent manner in the MS‑treated rats compared to the positive control group, while a significant dose‑dependent increase in Akt expression, a pro‑survival protein, was observed. In addition, MS administration reduced pro‑apoptotic indice levels, ameliorated histological insults, favorably modulated oxidative status and increased Akt expression levels, indicating a possible neuroprotective effect in the case of CO poisoning. On the whole, the findings of this study indicate that MS may prove to be useful in protecting against CO‑induced cerebral injury.

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

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

Radon and lung cancer: What does the public really know?

Radon causes approximately 21,000 deaths annually from lung cancer, making it the second most important cause of lung cancer after smoking. However, the extent of public knowledge about radon is unclear. We systematically reviewed the epidemiologic literature in order to assay the public's understanding about radon and specifically, whether radon is known to cause lung cancer. Radon knowledge has most often been gauged via telephone and in-person responses to the question, "Have you heard about radon?" Our review of 20 such studies reveals that although many individuals have "heard about" radon, many segments of the population, particularly individuals younger than thirty and those with less education, do not know what radon is. Of those who have heard about radon, the majority of respondents in many studies did not know that radon causes lung cancer. Conversely, misinformation about radon is common; approximately 50% of respondents in many studies reported the erroneous belief that radon causes headaches. This suggests that the public has confused the effects of radon with those of carbon monoxide. Rates of radon testing and mitigation are correpondingly low and appear to reflect cognitive defense mechanisms by which individuals believe that their risks from radon are lower than the risks faced by others. Our review suggests that public information materials about radon require revision. Specifically, these should emphasize that radon causes lung cancer and that household carbon monoxide detectors do not detect it. Radon education provided by realtors at the time of residential home sales may be a promising venue to increase radon testing and remediation.

Effects of ambient carbon monoxide on daily hospitalizations for cardiovascular disease: a time-stratified case-crossover study of 460,938 cases in Beijing, China from 2013 to 2017

BACKGROUND

Evidence focused on exposure to ambient carbon monoxide (CO) and the risk of hospitalizations for cardiovascular diseases (CVD) is lacking in developing countries. This study aimed to examine the effect of CO exposure on hospitalizations for CVD in Beijing, China.

METHODS

A total of 460,938 hospitalizations for cardiovascular diseases were obtained from electronic hospitalization summary reports from 2013 to 2017. A time-stratified case-crossover design was conducted to investigate the association between CO exposure and hospitalizations for total and cause-specific CVD, including coronary heart disease (CHD), atrial fibrillation (AF), and heart failure (HF). Stratified analysis was also conducted by age group (18-64 years and ≥ 65 years) and sex.

RESULTS

Linear exposure-response curves for the association between ambient CO exposure and hospitalizations for CVD was observed. Ambient CO was positively associated with hospitalizations for total CVD and CHD. However, the observed increased risk was not statistically significant for hospitalizations for AF and HF. The strongest effect of CO concentration was observed on the current- and previous-day of exposure (lag _0-1 day). For a 1 mg/m³ increase in a 2-day moving average CO concentration, an increase of 2.8% [95% confidence interval (CI): 2.2 to 3.3%] and 3.0% (95% CI: 2.4 to 3.6%) in daily hospital admissions for CVD and CHD were estimated, respectively. This association was robust after adjusting for other copollutants and did not vary by age group and sex.

CONCLUSIONS

Ambient CO exposure increased the risk of hospitalizations for CVD, especially for CHD in Beijing. Further studies are warranted to explore the association between ambient CO and hospitalizations for AF and HF.

Hypoxia and hyperbaric oxygen therapy: a review

Hypoxia causes a cascade of activity from the level of the individual down to the regulation and function of the cell nucleus. Prolonged periods of low oxygen tension are a core feature of several disease states. Advances in the study of molecular biology have begun to bridge the gap between the cellular response to hypoxia and physiology. Hyperbaric oxygen therapy is a treatment for hypoxic- and inflammatory-driven conditions, in which patients are treated with 100% oxygen at pressures greater than atmospheric pressure. This review discusses hypoxia, the physiologic changes associated with hypoxia, the responses that occur in the cells during hypoxic conditions, and the role that hyperbaric oxygen therapy can play as part of the treatment for many patients suffering from diseases with underlying hypoxia.

Therapeutic Aspects of Carbon Monoxide in Cardiovascular Disease

Carbon monoxide (CO) is being increasingly recognized as a potential therapeutic with important signaling functions in various diseases. Carbon monoxide-releasing molecules (CORMs) show anti-apoptotic, anti-inflammatory, and anti-oxidant effects on the tissues of organisms, thus contributing to tissue homeostasis. An increase in reactive oxygen species production from the mitochondria after exposure to CO is also considered one of the underlying mechanisms of cardioprotection, although mitochondrial inhibition is the main toxic mechanism of CO poisoning. This review highlights the mechanism of the biological effects of CO and its potential application as a therapeutic in clinical settings, including in cardiovascular diseases. This review also discusses the obstacles and limitations of using exogenous CO or CORMs as a therapeutic option, with respect to acute CO poisoning.

Red Blood Cell Disorders: Perioperative Considerations for Patients Undergoing Cardiac Surgery

Disorders affecting red blood cells (RBCs) are uncommon yet have many important physiologic considerations for patients undergoing cardiac surgery. RBC disorders can be categorized by those that are congenital or acquired, and further by disorders affecting the RBC membrane, hemoglobin, intracellular enzymes, or excessive RBC production. A foundational understanding of the physiologic derangement for these disorders is critical when considering perioperative implications and optimization, strategies for cardiopulmonary bypass, and the rapid recognition and treatment if complications occur. This review systematically outlines the RBC disorders of frequency and relevance with an emphasis on how the disorder affects normal physiologic processes, a review of the literature related to the disorder, and the implications and recommendations for patients undergoing cardiac surgery.

Oxygen Treatment in Intensive Care and Emergency Medicine

BACKGROUND

Oxygen treatment is often life-saving, but multiple studies in recent years have yielded evidence that the indiscriminate administration of oxygen to patients in the intensive care unit and emergency room can cause hyperoxia and thereby elevate mortality.

METHODS

This review is based on prospective, randomized trials concerning the optimum use of oxygen in adult medicine, which were retrieved by a selective search in PubMed, as well as on pertinent retrospective studies and guideline recommendations.

RESULTS

13 prospective, randomized trials involving a total of 17 213 patients were analyzed. In patients with acute exacerbations of chronic obstructive pulmonary disease (COPD) and in ventilated intensive-care patients, normoxia was associated with a lower mortality than hyperoxia (2% vs. 9%). In patients with myocardial infarction, restrictive oxygen administration was associated with a smaller infarct size on cardiac MRI at 6 months compared to oxygen administration at 8 L/min (13.1 g vs. 20.3 g). For patients with stroke, the currently available data do not reveal any benefit or harm from oxygen administration. None of the trials showed any benefit from the administration of oxygen to non-hypoxemic patients; in fact, this was generally associated with increased morbidity or mortality.

CONCLUSION

Hypoxemia should certainly be avoided, but the fact that the liberal administration of oxygen to patients in intensive care units and emergency rooms tends to increase morbidity and mortality implies the advisability of a conservative, normoxic oxygenation strategy.

Carbon monoxide analysis method in human blood by Airtight Gas Syringe - Gas Chromatography - Mass Spectrometry (AGS-GC-MS): Relevance for postmortem poisoning diagnosis

Carbon monoxide is one of the most abundant toxic air pollutants. Symptoms of a CO intoxication are non-specific, leading to a high number of misdiagnosed CO poisoning cases that are missing in the disease statistics. The chemical nature of the molecule makes it difficult to detect for long periods and at low levels, thus requiring a very accurate and sensitive method. Current methods capable of accurate and sensitive analyses are available, however an inconsistency between results and symptoms are frequently reported. Therefore, an improved method for the analysis of carbon monoxide in blood and in the headspace (HS) of the sampling tube with the use of Airtight Gas Syringe - Gas Chromatography - Mass Spectrometry (AGS-GC-MS) is hereby presented and validated, for CO concentrations in a range of 10-200 nmol/mL HS (2-40 μmol/mL blood). Analytical LOQ is found at 0.9 nmol/mL HS (0.18 μmol/mL blood) and LOD at 0.1 nmol/mL gas. Application to intoxicated samples from autopsies and comparison to previously published methods show that this method is more appropriate, since performed under fully controlled conditions. Results show higher CO concentrations compared to previous approaches, indicating that results might have been underestimating the true blood CO burden. Therefore, this approach has the potential to help reduce the misdiagnosed cases and the gap between measurement and diagnosis of CO poisonings.

Delayed neurologic sequelae of carbon monoxide intoxication

Altered consciousness and accompanying neurological symptoms are both complex and challenging cases for emergency physicians. These are not specific and may be a sign of a variety of medical conditions including stroke and delayed neurological sequelae (DNS) is a recurrent transient neuropsychiatric consequence of CO intoxication. DNS produces a spectrum of varying symptoms and the diagnosis is primarily made on the basis of clinical features and radiological findings from CT and conventional MRI. In clinical practice, serious CO intoxication is treated only with oxygen therapy although no effective treatment exists. Emergency physicians play a major role in managing patients presenting with CO intoxication and preventing DNS.

Accuracy of detection of carboxyhemoglobin and methemoglobin in human and bovine blood with an inexpensive, pocket-size infrared scanner

Detecting life-threatening common dyshemoglobins such as carboxyhemoglobin (COHb, resulting from carbon monoxide poisoning) or methemoglobin (MetHb, caused by exposure to nitrates) typically requires a laboratory CO-oximeter. Because of cost, these spectrophotometer-based instrument are often inaccessible in resource-poor settings. The aim of this study was to determine if an inexpensive pocket infrared spectrometer and smartphone (SCiO®Pocket Molecular Sensor, Consumer Physics Ltd., Israel) accurately detects COHb and MetHb in single drops of blood. COHb was created by adding carbon monoxide gas to syringes of heparinized blood human or cow blood. In separate syringes, MetHb was produced by addition of sodium nitrite solution. After incubation and mixing, fractional concentrations of COHb or MetHb were measured using a Radiometer ABL-90 Flex® CO-oximeter. Fifty microliters of the sample were then placed on a microscope slide, a cover slip applied and scanned with the SCiO spectrometer. The spectrograms were used to create simple linear models predicting [COHb] or [MetHb] based on spectrogram maxima, minima and isobestic wavelengths. Our model predicted clinically significant carbon monoxide poisoning (COHb ≥15%) with a sensitivity of 93% and specificity of 88% (regression r2 = 0.63, slope P<0.0001), with a mean bias of 0.11% and an RMS error of 21%. Methemoglobinemia severe enough to cause symptoms (>20% MetHb) was detected with a sensitivity of 100% and specificity of 71% (regression r2 = 0.92, slope P<0.001) mean bias 2.7% and RMS error 21%. Although not as precise as a laboratory CO-oximeter, an inexpensive pocket-sized infrared scanner/smartphone detects >15% COHb or >20% MetHb on a single drop of blood with enough accuracy to be useful as an initial clinical screening. The SCiO and similar relatively low cost spectrometers could be developed as inexpensive diagnostic tools for developing countries.

iTRAQ-based differential proteomic analysis of the brains in a rat model of delayedcarbon monoxide encephalopathy

Delayed encephalopathy after acute carbon monoxide poisoning (DEACMP) is a difficult-to-manage neurological complication that can severely affect the life quality of patients. Although the central nervous system (CNS) injuries have been reported, the underlying molecular mechanisms are still unclear. Therefore, we established a rat model of DEACMP, applying isobaric tags for a relative and absolute quantification (iTRAQ)-based proteomics approach to identify differentially expressed proteins in cerebral tissue. A total of 170 proteins in the CO exposure groups were identified as differentially changed. Bioinformatics analysis suggested that these proteins are mainly involved in the biological processes, such as energy metabolism and many neurodegenerative diseases. Three proteins, Glial fibrillary acidic protein (GFAP), mitochondrial malate dehydrogenase (MDHM), and isocitrate dehydrogenase [NAD] subunit alpha (IDH3A), were identified as playing important roles in CNS injuries in DEACMP, and were successfully confirmed by immunohistochemistry analysis. Our study not only offers us new insights into the pathophysiological mechanisms of CNS injuries in DEACMP, but also may provide clinicians with important references in early prevention and treatment.

A review of the experimental evidence on the toxicokinetics of carbon monoxide: the potential role of pathophysiology among susceptible groups

BACKGROUND

Acute high level carbon monoxide (CO) exposure can cause immediate cardio-respiratory arrest in anyone, but the effects of lower level exposures in susceptible persons are less well known. The percentage of CO-bound hemoglobin in blood (carboxyhemoglobin; COHb) is a marker of exposure and potential health outcomes. Indoor air quality guidelines developed by the World Health Organization and Health Canada, among others, are set so that CO exposure does not lead to COHb levels above 2.0%, a target based on experimental evidence on toxicodynamic relationships between COHb and cardiac performance among persons with cardiovascular disease (CVD). The guidelines do not consider the role of pathophysiological influences on toxicokinetic relationships. Physiological deficits that contribute to increased CO uptake, decreased CO elimination, and increased COHb formation can alter relationships between CO exposures and resulting COHb levels, and consequently, the severity of outcomes. Following three fatalities attributed to CO in a long-term care facility (LTCF), we queried whether pathologies other than CVD could alter CO-COHb relationships. Our primary objective was to inform susceptibility-specific modeling that accounts for physiological deficits that may alter CO-COHb relationships, ultimately to better inform CO management in LTCFs.

METHODS

We reviewed experimental studies investigating relationships between CO, COHb, and outcomes related to health or physiological outcomes among healthy persons, persons with CVD, and six additional physiologically susceptible groups considered relevant to LTCF residents: persons with chronic obstructive pulmonary disease (COPD), anemia, cerebrovascular disease (CBD), heart failure, multiple co-morbidities, and persons of older age (≥ 60 years).

RESULTS

We identified 54 studies published since 1946. Six studies investigated toxicokinetics among healthy persons, and the remaining investigated toxicodynamics, mainly among healthy persons and persons with CVD. We identified one study each of CO dynamics in persons with COPD, anemia and persons of older age, and no studies of persons with CBD, heart failure, or multiple co-morbidities. Considerable heterogeneity existed for exposure scenarios and outcomes investigated.

CONCLUSIONS

Limited experimental human evidence on the effects of physiological deficits relevant to CO kinetics exists to support indoor air CO guidelines. Both experimentation and modeling are needed to assess how physiological deficits influence the CO-COHb relationship, particularly at sub-acute exposures relevant to indoor environments. Such evidence would better inform indoor air quality guidelines and CO management in indoor settings where susceptible groups are housed.

Alterations in mitochondrial respiration and reactive oxygen species in patients poisoned with carbon monoxide treated with hyperbaric oxygen

Background

Carbon monoxide (CO) poisoning is the leading cause of poisoning mortality and morbidity in the USA. Carboxyhemoglobin (COHb) levels are not predictive of severity or prognosis. At this time, the measurement of mitochondrial respiration may serve as a biomarker in CO poisoning. The primary objective of this study was to assess changes in mitochondrial function consisting of respiration and generation of reactive oxygen species (ROS) in peripheral blood mononuclear cells (PBMCs) obtained from patients with CO poisoning.

Methods

PBMCs from patients having confirmed CO exposure treated with hyperbaric oxygen or HBO (CO group) and healthy controls (control group) were analyzed with high-resolution respirometry. PBMCs were placed in a 2-ml chamber at a final concentration of 3–4 × 10⁶ cells/ml to simultaneously obtain both respiration and hydrogen peroxide (H₂O₂) production. In the CO group, we performed measurements before and after patients underwent their first HBO treatment.

Results

We enrolled a total of 17 subjects, including 7 subjects with confirmed CO poisoning and 10 subjects in the control group. The CO group included five (71.4%) men and two (28.6%) women having a median COHb of 28%. There was a significant decrease in respiration as measured in pmol O₂ × s^− 1 × 10^− 6 PBMCs in the CO group (pre-HBO) when compared to the control group: maximal respiration (18.4 ± 2.4 versus 35.4 ± 2.8, P < 0.001); uncoupled Complex I respiration (19.8 ± 1.8 versus 41.1 ± 3.8, P < 0.001); uncoupled Complex I + II respiration (32.3 ± 3.2 versus 58.3 ± 3.1, P < 0.001); Complex IV respiration (43.5 ± 2.9 versus 63.6 ± 6.31, P < 0.05). There were also similar differences measured in the CO group before and after HBO treatment with an overall increase in respiration present after treatment. We also determined the rate of H₂O₂ production simultaneously with the measurement of respiration. There was an overall significant increase in the H₂O₂ production in the CO group after HBO treatment when compared to prior HBO treatment and the control group.

Conclusions

In this study, PBMCs obtained from subjects with CO poisoning have an overall decrease in respiration (similar H₂O₂ production) when compared to controls. The inhibition of Complex IV respiration is from CO binding leading to a downstream decrease in respiration at other complexes. PBMCs obtained from CO-poisoned individuals immediately following initial HBO therapy displayed an overall increase in both respiration and H₂O₂ production. The study findings demonstrate that treatment with HBO resulted in improved cellular respiration but a higher H₂O₂ production. It is unclear if the increased production of H₂O₂ in HBO treatment is detrimental.

Smoke Inhalation Injury: Etiopathogenesis, Diagnosis, and Management

Smoke inhalation injury is a major determinant of morbidity and mortality in fire victims. It is a complex multifaceted injury affecting initially the airway; however, in short time, it can become a complex life-threatening systemic disease affecting every organ in the body. In this review, we provide a summary of the underlying pathophysiology of organ dysfunction and provide an up-to-date survey of the various critical care modalities that have been found beneficial in caring for these patients. Major pathophysiological change is development of edema in the respiratory tract. The tracheobronchial tree is injured by steam and toxic chemicals, leading to bronchoconstriction. Lung parenchyma is damaged by the release of proteolytic elastases, leading to release of inflammatory mediators, increase in transvascular flux of fluids, and development of pulmonary edema and atelectasis. Decreased levels of surfactant and immunomodulators such as interleukins and tumor-necrosis-factor-α accentuate the injury. A primary survey is conducted at the site of fire, to ensure adequate airway, breathing, and circulation. A good intravenous access is obtained for the administration of resuscitation fluids. Early intubation, preferably with fiberoptic bronchoscope, is prudent before development of airway edema. Bronchial hygiene is maintained, which involves therapeutic coughing, chest physiotherapy, deep breathing exercises, and early ambulation. Pharmacological agents such as beta-2 agonists, racemic epinephrine, N-acetyl cysteine, and aerosolized heparin are used for improving oxygenation of lungs. Newer agents being tested are perfluorohexane, porcine pulmonary surfactant, and ClearMate. Early diagnosis and treatment of smoke inhalation injury are the keys for better outcome.

Carbon monoxide poisoning in Iran during 1999-2016: A systematic review and meta-analysis

BACKGROUND

Carbon monoxide (CO) poisoning is a common cause of emergency department (ED) visits worldwide with high levels of morbidity and mortality. No inclusive nationally statistics of CO poisoning in Iran is available. The present review aimed to describe and review the pattern of CO poisoning in Iran.

METHODS

The search of Medline, SCOPUS, Cochrane library, Google Scholar, Magiran, IranDoc and SID (Scientific Information Database) yielded only 10 studies discussing the epidemiology of CO poisoning in Iran. Outcomes of interest were determining the demographic characteristics, prevalence and mortality rates, annual trends, main sources and mechanisms, location of incidents of CO poisoning as well as providing the safety awareness and precautions.

RESULTS

Totally, 10 studies including 6372 victims of CO poisoning were reviewed. The estimated incidence rate of CO poisoning was 38.91 per 100,000, the proportionate mortality rate was 11.6 per 1000 death and the pooled case fatality rate of was 9.5% (95% CI 6.3%-14.30%). Of the total 5105 individuals with CO poisoning, 2048 (40.12%) were male and 3057 (59.88%) were female. In addition, of 5105 poisoned, 4620 (90.50%) were alive and 485 (9.50%) were dead. The number of fatal CO poisoning cases among men and women were 259 (5.07%) and 226 (4.43%) victims, respectively; while the number of non-fatal CO poisoning cases among men and women were 1790 (35.06%) and 2830 (55.44%) individuals, respectively. The mean age of victims was about 30 years. Most of the victims (36.37%) had the educational level of secondary school, marital status of single (52.74%), and occupational status of housekeeper (27.48%).

CONCLUSION

The incidence, proportionate mortality and case fatality rates of CO poisoning is high in Iran, particularly in young individuals. It seems that preventive strategies should be taught by health care providers more thoroughly and implemented by policy makers more strictly as a mandatory law.

Carbon monoxide in lung cell physiology and disease

Carbon monoxide (CO) is an endogenously produced gas that has gained recognition as a biological signal transduction effector with properties similar, but not identical, to that of nitric oxide (NO). CO, which binds primarily to heme iron, may activate the hemoprotein guanylate cyclase, although with lower potency than NO. Furthermore, CO can modulate the activities of several cellular signaling molecules such as p38 MAPK, ERK1/2, JNK, Akt, NF-κB, and others. Emerging studies suggest that mitochondria, the energy-generating organelle of cells, represent a key target of CO action in eukaryotes. Dose-dependent modulation of mitochondrial function by CO can result in alteration of mitochondrial membrane potential, mitochondrial reactive oxygen species production, release of proapoptotic and proinflammatory mediators, as well as the inhibition of respiration at high concentration. CO, through modulation of signaling pathways, can impact key biological processes including autophagy, mitochondrial biogenesis, programmed cell death (apoptosis), cellular proliferation, inflammation, and innate immune responses. Inhaled CO is widely known as an inhalation hazard due to its rapid complexation with hemoglobin, resulting in impaired oxygen delivery to tissues and hypoxemia. Despite systemic and cellular toxicity at high concentrations, CO has demonstrated cyto- and tissue-protective effects at low concentration in animal models of organ injury and disease. These include models of acute lung injury (e.g., hyperoxia, hypoxia, ischemia-reperfusion, mechanical ventilation, bleomycin) and sepsis. The success of CO as a candidate therapeutic in preclinical models suggests potential clinical application in inflammatory and proliferative disorders, which is currently under evaluation in clinical trials.