Unstable angina and exposure to carbon monoxide

Diagnosis of carbon monoxide exposure in clinical research and practice: A scoping review

OBJECTIVE

To undertake a scoping review to identify methods and diagnostic levels used in determining unintentional, non-fire related carbon monoxide exposure.

DESIGN

Online databases and grey literature were searched from 1946 to 2023 identifying 80 papers where carbon monoxide levels were reported.

RESULTS

80 papers were included; 71 research studies and 9 clinical guidelines. Four methods were described: blood carboxyhaemoglobin (arterial or venous blood analysis), carbon monoxide oximetry (SpO2), expired carbon monoxide, and ambient carbon monoxide sampling. Blood analysis methods predominated (60.0% of the papers). Multiple methods of measurement were used in 26 (32.5%) of the papers. Diagnostic levels for carboxyhaemoglobin were described in 54 (67.5%) papers, ranging between 2% and 15%. 26 (32.5%) papers reported diagnostic levels that were adjusted for the smoking status of the patient.

CONCLUSIONS

Four methods were found for use in different settings. Variability in diagnostic thresholds impairs diagnostic accuracy. Agreement on standardised diagnostic levels is required to enable consistent diagnosis of unintentional, non-fire related carbon monoxide exposure.

Rare Causes of Acute Coronary Syndrome: Carbon Monoxide Poisoning

Acute coronary syndrome (ACS) is a spectrum of clinical and paraclinical disorders arising from an imbalance of oxygen demand and supply to the myocardium. The most common cause is atherosclerosis; however, other rare causes such as carbon monoxide (CO) poisoning should be considered. Through tissue hypoxia and direct cell injury, CO poisoning can lead to a broad spectrum of cardiac disorders, especially ACS. Materials and Methods. We have conducted a retrospective study in the Toxicology Department of Saint Spiridon Emergency University Hospital, including all patients admitted through the emergency department with CO poisoning. We divided the cohort into event group (myocardial injury) and non-event group (patients without myocardial injury) and performed a subset analysis of the former. Results. A total of 65 patients were included, 22 in the event and 43 in the non-event group. The severity of poisoning did not correlate with myocardial injury; however, 50% of the event group had severe poisoning with carboxyhaemoglobin ≥ 20%. Cardiac enzyme markers (troponin and creatin-kinase MB) had a statistically significant increase in the event group compared to the non-event group (p < 0.05). Most of the patients in the STEMI (50%) and NSTEMI (66.7%) groups had severe CO intoxication. The STEMI group had a mean age of 27.7 years old and no comorbidities. Conclusions. Myocardial injury can develop in CO poisoning irrespective of the severity of poisoning, and it can be transient, reversible, or permanent. Our study introduces new information on adverse cardiac events in patients with CO poisoning, focusing on the ACS. We found that the severity of CO poisoning plays an important role in developing myocardial injury, as 50% of patients in the event group were severely intoxicated. While in-hospital mortality in our study was low, further prospective studies should investigate the long-term mortality in these patients.

Carbon Monoxide Poisoning

Carbon monoxide is a colorless, odorless, highly toxic gas primarily produced through the incomplete combustion of organic material. Carbon monoxide binds to hemoglobin and other heme molecules, causing tissue hypoxia and oxidative stress. Symptoms of carbon monoxide poisoning can vary from a mild headache to critical illness, which can make diagnosis difficult. When there is concern for possible carbon monoxide poisoning, the diagnosis can be made via blood co-oximetry. The primary treatment for patients with carbon monoxide poisoning is supplemental oxygen, usually delivered via a nonrebreather mask. Hyperbaric oxygen can also be used, but the exact indications are controversial.

Chronic carbon monoxide poisoning. A report of two cases

If acute carbon monoxide poisoning is a well-known emergency situation, this is not the case for chronic poisoning. The missed diagnosis of acute CO poisoning is a well-known problem but the identification of a chronic poisoning is very challenging. Knowledge and awareness of chronic poisoning is less defined and probably there is a great number of patients with undiagnosed chronic CO poisoning. It is possible that in case of missed diagnosis because of non-specific symptoms, chronic CO poisoning could be responsible for significant morbidity. We describe the case of a married couple who were rescued almost simultaneously, to show this clinical condition.

Cardiovascular Abnormalities in Carbon Monoxide Poisoning

Acute carbon monoxide (CO) poisoning is the most common cause of poisoning and poisoning-related death in the United States. It manifests as broad spectrum of symptoms ranging from mild headache, nausea, and fatigue to dizziness, syncope, coma, seizures resulting in cardiovascular collapse, respiratory failure, and death. Cardiovascular complications of CO poisoning has been well reported and include myocardial stunning, left ventricular dysfunction, pulmonary edema, and arrhythmias. Acute myocardial ischemia has also been reported from increased thrombogenicity due to CO poisoning. Myocardial toxicity from CO exposure is associated with increased short-term and long-term mortality. Carboxyhemoglobin (COHb) levels do not correlate well with the clinical severity of CO poisoning. Supplemental oxygen remains the cornerstone of therapy for CO poisoning. Hyperbaric oxygen therapy increases CO elimination and has been used with wide variability in patients with evidence of neurological and myocardial injury from CO poisoning, but its benefit in limiting or reversing cardiac injury is unknown. We present a comprehensive review of literature on cardiovascular manifestations of CO poisoning and propose a diagnostic algorithm for managing patients with CO poisoning.

Reversible Increases in Qt Dispersion and P Wave Dispersion during Carbon Monoxide Intoxication

Objectives

Carbon monoxide (CO) is a potent myocardial toxin. We investigated the association between acute CO intoxication and electrocardiographic QT interval (QTmax/QTmin), corrected QT interval (cQTmax/cQTmin), QT dispersion (QTd) and corrected QT dispersion (cQTd), P wave duration (Pmax/Pmin) and P wave dispersion (Pd), which were known as predictors of ventricular arrhythmias, atrial fibrillation and sudden death.

Methods

Electrocardiography with 12-leads and blood gas were taken from 65 patients with CO intoxication as well as 65 control patients with similar age and gender distribution at the admission time to the emergency department and at the 4th hour post-therapy. The carboxyhaemoglobin (COHb) levels and the relationships with electrocardiographic parameters were studied.

Results

The mean COHb levels were 21.43±6.85% and 1.37±0.98% in intoxicated patients and in the control group respectively. QTmax, QTd, cQTmax, cQTd, Pmax, and Pd were found significantly higher in intoxicated patients when compared to the control group (373.98±40.35 vs. 355.98±32.88, p=0.006; 49.29±22.66 vs. 20.43±11.16, p<0.001; 455.38±30.72 vs. 419.57±22.27, p<0.001; 60.88±25.99 vs. 25.75±13.13, p<0.001; 107.91±13.28 vs. 96.65±12.65, p<0.001, 46.85±13.49 vs. 35.22±10.07, p<0.001 respectively). In Pearson correlation analysis, there were significant correlations between COHb level and QTmax, QTd, cQTmax, cQTd, Pmax and Pd (r=0.211, p=0.016; r=0.610, p<0.001; r=0.599, p<0.001; r=0.628, p<0.001; r=0.458, p<0.001; r=0.414, p<0.001 respectively).

Conclusion

A correlation between reversible increases in QTd, cQTmax, cQTd, Pmax and Pd in the electrocardiogram and COHb can be observed in acute CO intoxication patients.

Medical and biological factors affecting mortality in elderly residential fire victims: a narrative review of the literature

For older people (aged over 65 years), the risk of dying in a residential fire is doubled compared to the general population. Obvious causes of death mainly include smoke inhalation and burn injuries. That older people are more fragile and have more concurrent diseases is inherent, but what is it that makes them more vulnerable? It is known that the number of elderly people is increasing globally and that the increased risk of death in fires can be explained, at least in part, by physical and/or cognitive disabilities as well as socioeconomic and behavioural factors. The possibility that medical illnesses and an aging organism/tissues might explain this increased risk has not been shown to the same extent. Therefore, this narrative literature review focuses on medical and biological explanations. An initial search using the terms ‘elderly’, ‘fatal’, ‘residential’ and ‘fire’ yielded some interesting articles. Using a broader snowball search also accepting grey literature, several additional risk factors could be identified. Cardiovascular diseases, in particular atherosclerotic heart disease, greatly increases the vulnerability to, for example, carbon monoxide and probably also other asphyxiating gases. Cardiovascular diseases and lack of physical fitness may also increase vulnerability to heat. Burned elderly patients are also at a higher risk of death than younger patients, but it is controversial whether it is age itself or the pre-existing illnesses that come with age that increase the risk. Immunosenescence, malnutrition and female gender are other risk factors for poorer outcome after burns, all of which are common among older people.

Elderly people have an increased risk of dying in house fires for several known reasons. This review explores possible medical/biological explanations and finds heart disease to be an important explanation.

Carbon monoxide exposure among police officers working in a traffic dense region of Southern India

Currently, in India, air pollution is widespread in urban areas where vehicles are major contributors. The aim of this study was to investigate the level of exposure in traffic police officers exposed to vehicle exhaust for less than 8 h/day. The specific objective of the study was to determine the levels of carboxyhaemoglobin (COHb) in these officers. The effect of exposure for 8 h/day is known, but shorter durations of chronic exposure need to be investigated, and there is a need to explore the policy options in this exposed population. This cross-sectional study, included non-smoking traffic police officers between 30 and 50 years of age working for more than 2 years in busy traffic junctions. The cases were sex matched with controls of same age group, working in offices at a teaching hospital. Venous blood was collected at the end of 3 h of duty for estimation of COHb among both the groups. The COHb levels were expressed as percentage values. Differences between the COHb levels among the traffic police officers and office workers were analysed using the Mann-Whitney U test and considered significant at p < 0.05. Traffic police officers had significantly elevated COHb levels compared with the controls; 76.5% of traffic police officers had COHb >2.5% compared with no office workers at this level and 41.2% of the police officers had COHb levels >4%. Overall, 53.8% of officers with COHb >2.5% reported headaches compared with 15.8% of officers with COHb <2.5%.

The neurotoxicology of carbon monoxide - Historical perspective and review

Carbon monoxide (CO) has been recognized as a poison for centuries, and remains one of the most common causes of both accidental and deliberate poisoning worldwide. Despite this, there are widespread misconceptions with regards to the mechanisms, diagnosis and outcomes of CO induced poisoning such as the idea that CO poisoning is rare; that carboxyhaemoglobin levels above 20% and loss of consciousness are required before nervous system damage ensues; and that the binding of CO to haemoglobin is the only mechanism of toxicity. Prevention and diagnosis of CO poisoning is hampered by the lack of awareness of CO as a cause of illness, among both the general public and healthcare professionals. To complicate matters further there is no standardized definition of CO poisoning. Carboxyhaemoglobin levels are often used as a marker of CO poisoning, yet plasma levels rapidly reduce upon removal of the source and are therefore an unreliable biomarker of exposure and tissue damage. Adverse neuropsychiatric outcomes after CO poisoning are difficult to define, especially as they fluctuate, mimic other non-specific complaints, and are not present in all survivors. This paper challenges a number of misconceptions about CO poisoning which can result in misdiagnosis, and consequently in mismanagement. We illustrate how recent developments in the understanding of CO toxicology explain the particular susceptibility of the central nervous system to the effects of CO exposure.

Myocardial Rupture following Carbon Monoxide Poisoning

We present the first case of severe cardiotoxicity of carbon monoxide leading to myocardial rupture and fatal outcome. 83-year-old woman was hospitalized 4 hours after the fire in her house with no respiratory or cardiac symptoms. After two days, she has suffered sudden collapse leading to cardiac arrest. Postmortem examination revealed intramural haemorrhage with myocardial rupture at the apex of the left ventricle. Minimal stenosis was noted in the proximal coronary arteries with no evidence of distal occlusion or any other long-standing heart disease. This case supports recommendations for targeted cardiovascular investigations in cases of CO poisoning.

Pathophysiology, clinics, diagnosis and treatment of heart involvement in carbon monoxide poisoning

The toxicity of carbon monoxide has been recognized for long throughout history and is unquestionably the leading cause of unintentional poisoning deaths in the Western countries. The severity of poisoning is dependent upon environmental and human factor. The leading pathophysiological mechanism resides in the ability of carbon monoxide to bind to hemoglobin molecules with high affinity, displacing oxygen and generating carboxyhemoglobin, which is virtually ineffective to deliver oxygen to the tissues. The organs with the highest demand for oxygen such as the brain and the heart are more vulnerable to injury. Myocardial involvement is commonplace in moderate to severe carbon monoxide poisoning and is associated with a substantially higher risk of mortality. Besides hypoxic damage, carbon monoxide produces myocardium injuries with cardiospecific mechanisms, mostly attributable to direct damage at cellular or subcellular level. The clinical spectrum of heart involvement is broad and encompasses cardiomyopathy, angina attack, myocardial infarction, arrhythmias and heart failure up to myocardial stunning, cardiogenic shock and sudden death. Patients with underlying cardiac disease, especially coronary heart disease, are at greater risk of infarction and arrhythmias. Single photon emission computed tomography (SPECT) is the technique of choice for diagnosing cardiac involvement, whereas the recent introduction of the highly sensitive troponin immunoassays seems promising for the early triage of patients. No specific treatment other than oxygen delivery can be advocated for cardiac toxicity at present, and 100% oxygen therapy should be continued until the patient is asymptomatic and carboxyhemoglobin levels decrease below 5-10%.

Screening for carbon monoxide exposure in selected patient groups attending rural and urban emergency departments in England: a prospective observational study

OBJECTIVES

Carbon monoxide (CO) exposure does not produce a classical toxidrome and so it is thought that it may easily be missed, allowing patients to continue to be exposed to CO. The aim of this study was to determine the proportion of raised carboxyhaemoglobin (COHb) levels in a targeted population of patients presenting to four emergency departments (EDs) in England.

DESIGN

A prospective observational study undertaken over a 9-month period.

SETTING

Four EDs; one in a rural/suburban area and three serving urban populations.

PARTICIPANTS

1758 patients presenting to the EDs with chest pain, exacerbation of chronic obstructive pulmonary disease (COPD), non-traumatic headache, seizures or flu-like symptoms.

MAIN OUTCOME

Measures COHb levels measured using a pulse CO-oximeter or venous sample. Patients with COHb levels ≥2.5% (non-smokers) or ≥5% (smokers) completed a questionnaire assessing potential sources. Patients were defined to be positive for CO exposure if they had a positive COHb and either an identified source or no other reason for their raised level.

RESULTS

Proportion of positive patients was: overall-4.3%; COPD-7.5%; headache-6.3%; flu-like-4.3%; chest pain-3.3%; seizures-2.1%. A variety of gas and solid (predominantly charcoal) fossil fuel sources were identified.

CONCLUSIONS

This study showed that 4.3% of patients presenting to EDs with non-specific symptoms had unexpectedly raised COHb levels 1.4% of patients had a source of CO identified. Study limitations included non-consecutive recruitment, delays in COHb measurements and a lack of ambient CO measurements, which precludes precise determination of incidence. However, this study should alert clinicians to consider CO exposure in patients presenting with non-specific symptoms, in particular headache and exacerbation of COPD, and if necessary refer patients for suitable public-health follow-up, even in the presence of low COHb readings. Further research should include standardised scene assessments.

Transient left ventricular systolic dysfunction associated with carbon monoxide toxicity

Carbon monoxide (CO) is one of well known chemical asphyxiants which cause tissue hypoxia with prominent neurologic and cardiovascular injury. Cardiac dysfunction after CO poisoning can be presented as two clinical patterns. One is transient global left ventricular (LV) dysfunction and the other is LV dysfunction with regional wall motion abnormalities. In this case report, we present a case with transient LV systolic dysfunction caused by intentional exposure to CO. After conservative treatment including high concentration of oxygen, the patient recovered completely without any complication.

Self-reported neurological symptoms in relation to CO emissions due to problem gas appliance installations in London: a cross-sectional survey

BACKGROUND

Previous research by the authors found evidence that up to 10% of particular household categories may be exposed to elevated carbon monoxide (CO) concentrations from poor quality gas appliance installations. The literature suggests certain neurological symptoms are linked to exposure to low levels of CO. This paper addresses the hypothesis that certain self-reported neurological symptoms experienced by a householder are linked to an estimate of their CO exposure.

METHODS

Between 27 April and 27 June 2006, 597 homes with a mains supply of natural gas were surveyed, mainly in old, urban areas of London. Qualified gas engineers tested all gas appliances (cooker, boiler, gas fire, and water heater) and reported, according to the Gas Industry Unsafe Situations Procedure, appliances considered At Risk (AR), Immediately Dangerous (ID) or Not to Current Standards (NCS). Five exposure risk categories were defined based on measurement of CO emitted by the appliance, its features and its use, with "high or very high" exposure category where occupants were considered likely to be exposed to levels greater than 26 ppm for one hour. The prevalence of symptoms at each level of exposure was compared with that at lowest level of exposure.

RESULTS

Of the households, 6% were assessed as having a "high or very high" risk of exposure to CO. Of the individuals, 9% reported at least one neurological symptom. There was a statistically significant association between "high or very high" exposure risk to CO and self-reported symptoms compared to "no exposure" likelihood, for households not in receipt of benefit, controlling for "number of residents" and presence of pensioners, OR = 3.23 (95%CI: 1.28, 8.15). Risk ratios across all categories of exposure likelihood indicate a dose-response pattern. Those households in receipt of benefit showed no dose-response pattern.

CONCLUSION

This study found an association between risk of CO exposure at low concentration, and prevalence of self-reported neurological symptoms in the community for those households not in receipt of benefit. As health status was self-reported, this association requires further investigation.

Serum levels of NT-ProBNP as an early cardiac marker of carbon monoxide poisoning

Acute carbon monoxide (CO) poisoning may cause cardiotoxicity. The natriuretic peptides, including atrial natriuretic peptide, brain natriuretic peptide (BNP), N-BNP, and NT-proBNP (N-terminal pro brain natriuretic peptide), are endogenous cardiac hormones that may be secreted upon myocardial stress. The aim of this study was to assess the plasma NT-proBNP level in acute CO poisoning and to compare it with healthy control. After approval by the ethical committee, 15 healthy controls and 15 patients admitted to the Gaziantep University Hospital (Gaziantep, Turkey) between January 2005 and July 2005 with the diagnosis of carbon monoxide poisoning were studied. Echocardiography was performed to all patients. Serum NT-proBNP, creatine kinase (CK), creatine kinase-MB (CK-MB), and troponin-T were also analyzed, along with the carboxyhemoglobin (COHb) level. The correlation between serum NT-proBNP and COHb level was investigated. Electrocardiography (ECG) was performed to all patients and healthy controls, and the results were compared. Differences in troponin, CK, and CK-MB levels were not statistically significant between groups (p > 0.05). The level of NT-proBNP and COHb were found to be increased in the study group. There was a positive correlation between the COHb and the NT-proBNP (r = 0.829, p < 0.01), and between the COHb and the CK (r = 0.394, p < 0.01). There was no difference between groups in other parameters, all of which were within normal range. Thus, in this study we showed that the plasma NT-proBNP level may contribute to the early diagnosis of cardiotoxicity in patients with carbon monoxide poisoning.

Carbon monoxide cardiotoxicity

Cardiac dysfunction including arrhythmias and myocardial ischemia have often been reported in carbon monoxide poisoning; scattered punctiform hemorrhages throughout the heart have been documented in autopsy samples. An appropriate diagnostic approach is crucial to assess carbon monoxide cardiac damage. This evaluation may be confounded by several factors, including the absence of overt symptoms and of specific ischemic changes in the electrocardiogram. In experimental studies, laboratory animals can develop cardiac changes similar to those seen in humans and therefore proved to be useful models to study the effects and the mechanisms of cardiac damage due to carbon monoxide. These investigations, as well as others performed in vitro, provide support for a direct action of carbon monoxide on the heart, in addition to systemic hypoxia produced by carboxyhemoglobin formation. This review focuses on the diagnostic aspects of carbon monoxide cardiotoxicity. Experimental results obtained in animals and in vitro models are also discussed.

Cardiac damage in pediatric carbon monoxide poisoning

BACKGROUND

Cardiovascular disorders including myocardial ischemia and heart failure have been described in both laboratory animals and humans following carbon monoxide poisoning. Carbon monoxide cardiotoxicity may be clinically occult and often remains undiagnosed because of the lack of overt symptoms and specific ischemic changes in the electrocardiogram. Routine myocardial necrosis markers have low diagnostic efficiency, particularly in patients with concomitant skeletal muscle necrosis or multiple organ failure complicating carbon monoxide poisoning. Carbon monoxide-induced cardiotoxicity has been investigated rarely in children.

CASE REPORT

This paper describes carbon monoxide poisoning in a 12-year-old child who suffered from occult cardiac damage despite mild symptoms and low carboxy hemoglobin concentrations. Myocardial and mitral valve dysfunctions were observed, suggesting an ischemia-like syndrome. Cardiac damage was completely reversible within 1 month.

CONCLUSION

This case report supports that a prolonged carbon monoxide exposure can cause cardiac damage in children even in the absence of specific symptoms, cerebral failure and high carboxyhemoglobin concentrations.

Carbon monoxide poisoning: easy to treat but difficult to recognise

Carbon monoxide (CO) poisoning is a common medical emergency and a frequent cause of deliberate or accidental death. It can cause acute and chronic central nervous system damage which may be minimised by prompt treatment with 100% oxygen or hyperbaric oxygen therapy. However, recognition of this intoxication can be difficult. Failure to diagnose it may have disastrous effects on the patient, and other members of the household who could subsequently become intoxicated. Guidance on the correct diagnosis of this condition is provided in the light of a number of studies screening emergency room populations. Guidelines for treatment with hyperbaric oxygen therapy are also reviewed.