Clinical policy: critical issues in the management of adult patients presenting to the emergency department with acute carbon monoxide poisoning

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

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

[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.

The Value of Neutrophil:Lymphocyte Ratio and Platelet:Lymphocyte Ratio in Predicting Clinical Severity in Children with Carbon Monoxide Poisoning

OBJECTIVE

To compare the values of neutrophil:lymphocyte ratio (NLR), platelet:lymphocyte ratio (PLR), and mean platelet volume (MPV) with carboxyhemoglobin (COHb) and lactate levels in children with acute CO intoxication.

METHODS

In this retrospective study, the patients were divided into two groups: mild-to-moderate carbon monoxide poisoning (COP) (COHb 10%-20%) and severe COP (COHb > 20%) according to the COHb levels in the application. All patients were compared in terms of NLR, PLR, and MPV parameters according to the severity of poisoning and the high lactate levels (≥ 2.2 mmol/L).

RESULTS

A total of 261 children with COP were included in the study. The number of patients with mild-to-moderate COP was 183 (70.1%), and the number of patients with severe COP was 78 (29.9%). NLR [2.57 (3.27), 1.65 (1.93), (p = 0.001)] and PLR [123.0 (88.24), 92.8 (54.1), (p = 0.001)] values of mild-to-moderate COP were statistically significantly lower than the severe COP group. In the group with high lactate level, PLR values were significantly lower [120.1 (71.9), 100.2 (85.4), (p = 0.017)]. NLR and PLR values were found to be predictive of severe COP.

CONCLUSION

NLR and PLR can be used for detection of clinical severity in patients with COP. PLR can be used in conjunction with lactate levels to detect tissue-level exposure in patients with COP.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Increased long-term risk of major adverse cardiovascular events in patients with carbon monoxide poisoning: A population-based study in Taiwan

Background

Carbon monoxide (CO) poisoning may cause toxicity to the cardiovascular system. However, the association between CO poisoning and the risk of major adverse cardiovascular events (MACE) remains unestablished. We investigated the incidence of MACE after CO poisoning in Taiwan and evaluated whether CO-poisoned individuals had a higher risk of MACE than did the general population.

Methods

Using Taiwan’s National Health Insurance Research Database (NHIRD) during 2005–2013, a nationwide population-based cohort study was conducted among patients who experienced CO poisoning between 2005 and 2013. CO poisoning was defined according to the International Classification of Diseases, Ninth Revision, Clinical Modification codes. The study cohort comprised patients with CO poisoning between 2005 and 2010 (N = 13,939). Each patient was matched according to age, sex and index date with four randomly selected controls from the comparison cohort (N = 55,756). All patients were followed from the study date until MACE development, death, or the end of 2013. The hazard ratios for MACE were compared between the two cohorts by using Cox proportional hazards regressions analyses.

Results

Incident cases of MACE were identified from the NHIRD. After adjustment for potential confounders, the study cohort was independently associated with a higher MACE risk (adjusted hazard ratio, 2.00; 95% confidence interval, 1.83–2.18).

Conclusion

This population-based cohort study indicated that patients with CO poisoning have a higher risk of MACE than do individuals without CO poisoning.

Review of the health effects of wildland fire smoke on wildland firefighters and the public

Each year, the general public and wildland firefighters in the US are exposed to smoke from wildland fires. As part of an effort to characterize health risks of breathing this smoke, a review of the literature was conducted using five major databases, including PubMed and MEDLINE Web of Knowledge, to identify smoke components that present the highest hazard potential, the mechanisms of toxicity, review epidemiological studies for health effects and identify the current gap in knowledge on the health impacts of wildland fire smoke exposure. Respiratory events measured in time series studies as incidences of disease-caused mortality, hospital admissions, emergency room visits and symptoms in asthma and chronic obstructive pulmonary disease patients are the health effects that are most commonly associated with community level exposure to wildland fire smoke. A few recent studies have also determined associations between acute wildland fire smoke exposure and cardiovascular health end-points. These cardiopulmonary effects were mostly observed in association with ambient air concentrations of fine particulate matter (PM2.5). However, research on the health effects of this mixture is currently limited. The health effects of acute exposures beyond susceptible populations and the effects of chronic exposures experienced by the wildland firefighter are largely unknown. Longitudinal studies of wildland firefighters during and/or after the firefighting career could help elucidate some of the unknown health impacts of cumulative exposure to wildland fire smoke, establish occupational exposure limits and help determine the types of exposure controls that may be applicable to the occupation.

Risk factors for the delayed onset of neuropsychologic sequelae following carbon monoxide poisoning

Aim

Carbon monoxide (CO) poisoning often manifests delayed neuropsychological sequelae. The risks and preventive factors for the development of delayed neuropsychological sequelae are controversial at present. The purpose of this retrospective study was to assess the risk factors for this condition.

Method

We studied 81 patients with CO poisoning admitted to the Critical Care and Emergency Medicine Center at the Kansai Medical University from 2006 to 2012. All patients (64 males and 17 females; average age, 45.9 years) were divided into non‐ delayed neuropsychological sequelae and delayed neuropsychological sequelae groups and retrospectively studied. Patient data were analyzed by univariate and multivariate analyses.

Results

The results of our study indicated that prolonged CO exposure, elevated serum creatinine phosphokinase levels, head image abnormality in the basal ganglion or white matter region, low Glasgow Coma Scale score, bedsore occurrence, and CO poisoning attributable to burning charcoal were each predictive risk factors for the development of delayed neuropsychological sequelae. Bedsore occurrence and serum creatinine phosphokinase elevation were significant risk factors by multivariate analysis, whereas no significant differences were found for age, gender, mean blood pressure, heart rate, arterial carboxyhemoglobin and lactate concentrations, or base excess.

Conclusion

We identified several predictive risk factors of delayed neuropsychological sequelae. We believe that these factors will contribute to identifying optimum therapeutic methods and follow‐up terms for patients with acute CO poisoning at risk of developing delayed neuropsychological sequelae.

Pulmonary Phototherapy for Treating Carbon Monoxide Poisoning

RATIONALE

Carbon monoxide (CO) exposure is a leading cause of poison-related mortality. CO binds to Hb, forming carboxyhemoglobin (COHb), and produces tissue damage. Treatment of CO poisoning requires rapid removal of CO and restoration of oxygen delivery. Visible light is known to effectively dissociate CO from Hb, with a single photon dissociating one CO molecule.

OBJECTIVES

To determine whether illumination of the lungs of CO-poisoned mice causes dissociation of COHb from blood transiting the lungs, releasing CO into alveoli and thereby enhancing the rate of CO elimination.

METHODS

We developed a model of CO poisoning in anesthetized and mechanically ventilated mice to assess the effects of direct lung illumination (phototherapy) on the CO elimination rate. Light at wavelengths between 532 and 690 nm was tested. The effect of lung phototherapy administered during CO poisoning was also studied. To avoid a thoracotomy, we assessed the effect of lung phototherapy delivered to murine lungs via an optical fiber placed in the esophagus.

MEASUREMENTS AND MAIN RESULTS

In CO-poisoned mice, phototherapy of exposed lungs at 532, 570, 592, and 628 nm dissociated CO from Hb and doubled the CO elimination rate. Phototherapy administered during severe CO poisoning limited the blood COHb increase and improved the survival rate. Noninvasive transesophageal phototherapy delivered to murine lungs via an optical fiber increased the rate of CO elimination while avoiding a thoracotomy.

CONCLUSIONS

Future development and scaling up of lung phototherapy for patients with CO exposure may provide a significant advance for treating and preventing CO poisoning.

Increased Long-Term Risk of Dementia in Patients With Carbon Monoxide Poisoning: A Population-Based Study

Carbon monoxide (CO) poisoning may cause toxicity of the central nervous system and heart. However, the association between CO poisoning and long-term dementia risk remains unestablished. We investigated the incidence of dementia in patients with CO poisoning in Taiwan and evaluated whether they had a higher risk of dementia than did the general population.A nationwide population-based cohort study was conducted among patients with CO poisoning identified using Taiwan's National Health Insurance Research Database (NHIRD) during 2004 to 2013. CO poisoning was defined according to the International Classification of Diseases, Ninth Revision, Clinical Modification codes. The study cohort comprised patients with CO poisoning between 2005 and 2010 (N = 14,590). Each patient was age-, sex-, and index date-matched with 4 randomly selected controls from the comparison cohort (N = 58,360). All patients were followed from the study date until dementia development, death, or the end of 2013. Cox proportional hazards regressions were performed for comparing the hazard ratios for dementia between the 2 cohorts.Incident cases of dementia were identified from the NHIRD.After adjustment for potential confounders, the study cohort was independently associated with a higher dementia risk (adjusted hazard ratio, 2.75; 95% confidence interval, 2.26-3.35).This population-based cohort study indicated that patients with CO poisoning have a higher risk of dementia than do people without CO poisoning.

Heart-type fatty acid-binding protein as a potential biomarker of acute carbon monoxide poisoning

BACKGROUND

The aim of this study was to investigate the role of serum heart-type fatty acid-binding protein (H-FABP) in the evaluation of patients with carbon monoxide (CO) poisoning.

METHODS

Forty patients with acute CO poisoning admitted to the emergency department and 15 healthy adults as the control group were included in the study. Serum H-FABP levels of patients were studied on admission and at the 6th, 12th, and 18th hours. Patients were divided into 3 groups according to clinical severity as mild, moderate, and severe. Patients were also divided into 2 groups according to treatment with hyperbaric oxygen (HBO) or normobaric oxygen.

RESULTS

Serum H-FABP levels of the patients were higher than those of the control group. There was a negative correlation between H-FABP levels and Glasgow Coma Scale score on admission. Heart-type fatty acid-binding protein levels were significantly higher in patients in the severe compared with mild group. Heart-type fatty acid-binding protein levels in patients treated with HBO were significantly higher than in those treated with normobaric oxygen. The cutoff value of serum H-FABP as an indicator for HBO treatment was determined as 1.5 ng/mL or higher, with a sensitivity of 85.7% and specificity of 69.7%. Serial measurement revealed that H-FABP level peaked at the sixth hour and reduced over time but remained higher than in the control group at the 18th hour.

CONCLUSION

Heart-type fatty acid-binding protein may be a promising novel biomarker in the evaluation of clinical severity and in the selection of patients for HBO therapy in acute CO poisoning.