Hyperbaric Oxygen Therapy Is Associated With Lower Short- and Long-Term Mortality in Patients With Carbon Monoxide Poisoning

Carbon monoxide poisoning: a clinical case report

BACKGROUND

Carbon monoxide (CO) poisoning is a serious yet frequently overlooked condition with diverse and nonspecific clinical presentations. The analysis of Lithuanian statistics reveals fluctuations in patient admissions and consultations through the poisoning center over a four-year period, with notable variations in fatality rates. Despite these trends, CO poisoning remains a significant public health concern due to its potential for severe long-term sequelae or death.

CASE

This case report focuses on two distinct presentations of CO poisoning in a young couple, illustrating the varied manifestations and outcomes of this toxic exposure. The first case describes a 23-year-old male presenting with altered consciousness and neurological symptoms, while the second case involves a 21-year-old pregnant female presenting with cardiovascular symptoms, including Takotsubo cardiomyopathy.

DISCUSSION

Highlights include the challenges in diagnosing CO poisoning; factors influencing the severity and symptoms of CO poisoning; potential complications; and considerations for hyperbaric oxygen therapy (HBO) in severe cases and pregnancy.

CONCLUSION

These cases illustrate the importance of recognizing CO poisoning, advocating for oxygen therapy as the first-line treatment, and calling for further research to improve understanding, treatment, and prevention of this potentially fatal condition.

Mortality Risks and Causes in Previous Carbon Monoxide Poisoning: A Nationwide Population-Based Cohort Study

OBJECTIVES

Carbon monoxide (CO) poisoning can cause brain, heart, and kidney injuries. We aimed to determine the association of risks of all-cause and cause-specific mortality in patients with previous CO poisoning.

DESIGN, SETTING, AND PATIENTS

This population-based cohort study used data from the National Health Insurance Service database and the National Death Registry of Korea. Adult patients diagnosed with CO poisoning and controls between 2002 and 2020 were included. Patients were matched with controls on a 1:1 ratio, considering age, sex, insurance type, income level, residential location, smoking status, alcohol consumption, obesity status, medical and psychiatric illness history, and Charlson Comorbidity Index at the index date. The cohort was monitored from 2002 to 2022 or until death or emigration in terms of all-cause and cause-specific mortality.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 48,600 patients with CO poisoning and matched controls were included. The cohort included 41.30% females, and the mean age was 48.05 years. Patients with CO poisoning exhibited a substantially elevated risk of all-cause mortality compared with those in the control group, with an adjusted hazard ratio (aHR) of 15.67 (95% CI, 12.58-19.51). The mortality associated with infectious (aHR, 6.71; 95% CI, 1.51-29.72), neoplasm/oncologic (aHR, 5.20; 95% CI, 3.39-7.99), endocrine (aHR, 13.44; 95% CI, 1.76-102.70), neurologic (aHR, 7.42; 95% CI, 2.91-18.90), cardiovascular (aHR, 8.97; 95% CI, 5.05-15.93), respiratory (aHR, 17.54; 95% CI, 5.48-56.17), and gastrointestinal (aHR, 24.72; 95% CI, 3.34-182.69) disorders was significantly greater in the former. Deaths due to external causes, including suicide, were significantly higher in the CO poisoning group (aHR, 50.07; 95% CI, 30.98-80.90).

CONCLUSIONS

Patients with CO poisoning exhibited a heightened risk of all-cause mortality compared with the matched controls. Additionally, the cause-specific mortality risk differed between the groups.

Effects of Pressure, Hypoxia, and Hyperoxia on Neutrophil Granulocytes

Background: The application of normo- and hyperbaric O2 is a common therapy option in various disease patterns. Thereby, the applied O2 affects the whole body, including the blood and its components. This study investigates influences of pressure and oxygen fraction on human blood plasma, nutrient media, and the functions of neutrophil granulocytes (PMNs). Methods: Neutrophil migration, reactive oxygen species (ROS) production, and NETosis were examined by live cell imaging. The treatment of various matrices (Roswell Park Memorial Institute 1640 medium, Dulbecco's Modified Eagle's Medium, H2O, human plasma, and isolated PMNs) with hyperbaric oxygen (HBO) was performed. In addition, the expression of different neutrophil surface epitopes (CD11b, CD62L, CD66b) and the oxidative burst were investigated by flow cytometry (FACS). The application of cold atmospheric plasma (CAP) to normoxic and normobaric culture media served as a positive control. Soluble reaction products such as H2O2, reactive nitrogen species (RNS: NO2- and NO3-), and ROS-dependent dihydrorhodamine oxidation were quantified by fluoro- and colorimetric assay kits. Results: Under normobaric normoxia, PMNs migrate slower and shorter in comparison with normobaric hyper- or hypoxic conditions and hyperbaric hyperoxia. The pressure component has less effect on the migration behavior of PMNs than the O2 concentration. Individual PMN cells produce prolonged ROS at normoxic conditions. PMNs showed increased expression of CD11b in normobaric normoxia, lower expression of CD62L in normobaric normoxia, and lower expression of CD66b after HBO and CAP treatment. Treatment with CAP increased the amount of ROS and RNS in common culture media. Conclusions: Hyperbaric and normobaric O2 influences neutrophil functionality and surface epitopes in a measurable way, which may have an impact on disorders with neutrophil involvement. In the context of hyperbaric experiments, especially high amounts of H2O2 in RPMI after hyperbaric oxygen should be taken into account. Therefore, our data support a critical indication for the use of normobaric and hyperbaric oxygen and conscientious and careful handling of oxygen in everyday clinical practice.

Development of a risk prediction nomogram for delayed neuropsychiatric sequelae in patients with acute carbon monoxide poisoning

OBJECTIVES

Delayed neuropsychiatric sequelae (DNS) are critical complications following acute carbon monoxide (CO) poisoning that can substantially affect the patient's life. Identifying high-risk patients for developing DNS may improve the quality of follow-up care. To date, the predictive DNS determinants are still controversial. Consequently, this study aimed to construct a practical nomogram for predicting DNS in acute CO-poisoned patients.

METHODS

This retrospective study was conducted on patients with acute CO poisoning admitted to the Tanta University Poison Control Center (TUPCC) from December 2018 to December 2022. Demographic, toxicological, and initial clinical characteristics data, as well as laboratory investigation results, were recorded for the included patients. After acute recovery, patients were followed up for six months and categorized into patients with and without DNS.

RESULTS

Out of 174 enrolled patients, 38 (21.8%) developed DNS. The initial Glasgow Coma Scale (GCS), carboxyhemoglobin (COHb) level, CO exposure duration, oxygen saturation, PaCO2, and pulse rate were significantly associated with DNS development by univariate analysis. However, the constructed nomogram based on the multivariable regression analysis included three parameters: duration of CO exposure, COHb level, and GCS with adjusted odd ratios of 1.453 (95% CI: 1.116-1.892), 1.262 (95% CI: 1.126-1.415), and 0.619 (95% CI: 0.486-0.787), respectively. The internal validation of the nomogram exhibited excellent discrimination (area under the curve [AUC] = 0.962), good calibration, and satisfactory decision curve analysis for predicting the DNS probability.

CONCLUSIONS

The proposed nomogram could be considered a simple, precise, and applicable tool to predict DNS development in acute CO-poisoned patients.

Carbon Monoxide Poisoning: From Occupational Health to Emergency Medicine

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

Increased Long-Term Risk of Dementia in Patients With Carbon Monoxide Poisoning: A Systematic Review and Meta-Analysis of Cohort Studies

OBJECTIVE

To assess whether carbon monoxide (CO) poisoning increases the incidence of dementia.

METHODS

We searched the Cochrane Library, PubMed, and EMBASE from inception to 14 August 2022. Two authors independently selected studies, assessed the quality of included studies, and extracted data. Any disagreement was resolved by discussion with a third author. Only cohort study with an enough follow-up period was included for systematic reviews and meta-analysis.

RESULTS

Thirty-three full texts were initially searched, but only three studies met our inclusion criteria, and they were comprised of 134,563 participants who were initially free of dementia. The follow-up period ranged from 9 to 12 years. We found that CO poisoning increased the risk of dementia incidence (adjusted hazard ratio 2.61, 95% confidence interval 1.56 to 4.36, p=0.0003). Subgroup analysis showed that the increased dementia risk was significant in males but not in females, and the highest risk was in young age group, followed by in middle age group, but not in the old one.

CONCLUSION

Overall the evidence from prospective cohort studies supported a link between CO exposure and an increased dementia risk, although all the included studies were limited to Taiwanese population.

Correlation between Time to Hyperbaric Oxygen Therapy and Delayed Neurological Sequelae in Acute Carbon Monoxide Poisoning Patients

Carbon monoxide (CO) is one of the most common causes of intoxication. Delayed neurologic sequelae (DNS) have a major impact on prognosis of CO poisoning patients. Hyperbaric oxygen therapy (HBOT) is widely used to treat DNS. However, there is no consensus regarding the optimal timing of HBOT. This prospective study enrolled patients who visited the hospital from November 2019 to October 2022. The cutoff value for the latency to HBOT after CO exposure was determined, and the area under the receiver operating characteristic curve (AUC) was estimated. In total, 167 patients were divided into non-DNS and DNS groups. The initial Glasgow Coma Scale (GCS) score, CO exposure time, latency to HBOT after CO exposure, median length of hospital stay (p < 0.001) and creatine kinase (p = 0.016) showed significant differences. A GCS score ≤ 9 had an odds ratio (OR) of 5.059 (95% confidence interval [CI]: 1.602-15.976, p = 0.006), and latency to HBOT after CO exposure ≥ 200 min had an OR of 18.971 (95% CI: 4.310-83.508, p < 0.001). The AUC was 0.8235 (95% CI: 0.7504-0.8966). A GCS score ≤ 9 and latency to HBOT ≥ 200 min may be significant risk factors for DNS.

Predicting acute brain lesions on magnetic resonance imaging in acute carbon monoxide poisoning: a multicenter prospective observational study

An acute brain lesion (ABL) identified by brain magnetic resonance imaging (MRI) after acute carbon monoxide (CO) poisoning is a strong prognostic factor for the development of delayed neuropsychiatric syndrome (DNS). This study aimed to identify predictors of ABLs on MRI in patients with acute CO poisoning. This was a multicenter prospective registry-based observational study conducted at two tertiary hospitals. A total of 1,034 patients were included. Multivariable logistic regression analysis showed that loss of consciousness (LOC) (adjusted odds ratio [aOR] 2.68, 95% Confidence Interval [CI]: 1.49-5.06), Glasgow Coma Scale (GCS) score < 9 (aOR 2.41, 95% CI: 1.49-3.91), troponin-I (TnI) (aOR 1.22, 95% CI: 1.08-1.41), CO exposure duration (aOR 1.09, 95% CI: 1.05-1.13), and white blood cell (WBC) (aOR 1.05, 95% CI: 1.01-1.09) were independent predictors of ABLs on MRI. LOC, GCS score, TnI, CO exposure duration, and WBC count can be useful predictors of ABLs on MRI in patients with acute CO poisoning, helping clinicians decide the need for an MRI scan or transfer the patient to an appropriate institution for MRI or hyperbaric oxygen therapy.

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

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

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

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

Hyperbaric oxygen should be used for carbon monoxide poisoning

This short review addresses the mechanisms of injury mediated by carbon monoxide (CO) and current information on efficacy of hyperbaric oxygen therapy (HBOT). Recent clinical series involving large, country-wide databases and prospective randomized trials are summarized. We conclude that there is an abundance of basic science and preclinical and clinical research supporting the use of HBOT for acute CO poisoning. With appropriate consideration for pathology and therapeutic mechanisms, HBOT at a dose of 2.5-3.0 atm absolute is a necessary treatment for this toxidrome.

Multi-Modal Synergistic 99mTc-TRODAT-1 SPECT and MRI for Evaluation of the Efficacy of Hyperbaric Oxygen Therapy in CO-Induced Delayed Parkinsonian and Non-Parkinsonian Syndromes

Background: Delayed neuropsychiatric syndrome (DNS) is characterized by motor dysfunction after acute carbon monoxide (CO) poisoning. We examined the relationship between dopamine transporter (DAT) loss using kit-based Tc-99m-TRODAT-1 (DAT single-photon emission-computed tomography (SPECT) radioligand) and globus pallidus necrosis on MRI, DAT availability before and after hyperbaric oxygen therapy (HBOT), and feasibility of Tc-99m-TRODAT-1 as an index for parkinsonian syndrome in CO poisoning. Methods: Twenty-one CO-intoxicated patients (mean ± SD age, 38.6 ± 11.4; range, 20−68 years) with DNS underwent Tc-99m-TRODAT-1 SPECT and MRI before HBOT and follow-up Tc-99m-TRODAT-1 SPECT to assess DAT recovery. Neurological examinations for Parkinsonism were performed after development of DNS. Results: Over 70% (15/21) of DNS patients showed globus pallidus necrosis on MRI. Significantly lower bilateral striatal DAT availability was associated with globus pallidus necrosis (p < 0.005). Moreover, 68.4% (13/19) of DNS subjects with Parkinsonian syndrome had lower bilateral striatal DAT availability vs. non-parkinsonian subjects pre- or post-HBOT. The SURs for both striata increased by ~11% post-HBOT in the Parkinsonian group; however, the left striatum presented a significantly higher DAT recovery rate than the right (*** p < 0.005). Conclusions: Coupled Tc-99m TRODAT-1 SPECT and MRI could assist evaluation of Parkinsonism risk and indicate DAT availability after HBOT in CO-poisoned patients with DNS.

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

Purpose

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

Methods

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

Results

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

Conclusion

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

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

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

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

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

Derivation and Validation of a Score for Predicting Poor Neurocognitive Outcomes in Acute Carbon Monoxide Poisoning

IMPORTANCE

Preventing neurocognitive sequelae is a major goal of treating acute carbon monoxide (co) poisoning. There is a lack of reliable score systems exist for assessing the probability of these sequelae.

OBJECTIVE

To develop and validate a novel clinical scoring system for predicting poor neurocognitive outcomes after acute co poisoning.

DESIGN, SETTING, AND PARTICIPANTS

This prognostic study included derivation and validation cohorts based on consecutive patient data prospectively collected at university hospitals from January 2006 to July 2021 in Wonju, Republic of Korea, and from August 2016 to June 2020 in Incheon, Republic of Korea. Participants included individuals aged 16 years or older admitted with co poisoning. Data were analyzed from October 2021 to January 2022.

EXPOSURES

Clinical and laboratory variables.

MAIN OUTCOMES AND MEASURES

The outcome of interest was neurocognitive sequelae at 4 weeks after co poisoning. Logistic regression models were used to identify predictors of poor neurocognitive outcomes in the derivation cohort. Outcomes were assessed using the Global Deterioration Scale [GDS] at 1-month after co exposure and classified as good (1-3 points) or poor (4-7 points).

RESULTS

A total of 1282 patients (median [IQR] age, 47.0 [35.0-59.0] years; 810 [63.2%] men) were assessed, including 1016 patients in the derivation cohort and 266 patients in the validation cohort. The derivation cohort included 126 patients (12.4%) with poor GDS scores. Among 879 patients in the derivation cohort with 1-year follow-up data, 757 (86.1%) had unchanged GDS scores, 102 (11.6%) had improved GDS scores, and 20 (2.3%) had worsened GDS scores. In the final prediction model, age older than 50 years (1 point), Glasgow Coma Scale score of 12 or less (1 point), shock (1 point), serum creatine kinase level greater than 320 U/L at emergency department presentation (1 point), and no use of hyperbaric oxygen therapy (1 point) remained factors significantly associated with worse outcome; therefore, this scoring system was called COGAS (creatine kinase, hyperbaric oxygen therapy, Glasgow Coma Scale, age, shock). Area under the receiver operating characteristic curve for COGAS score was 0.862 (95% CI, 0.828-0.895) for the derivation cohort and 0.870 (95% CI, 0.779-0.961) for the validation cohort.

CONCLUSIONS AND RELEVANCE

These findings suggest that assessing the COGAS score during the early phase of co poisoning may help identify patients at risk of poor neurocognitive sequelae.

État de connaissance des médecins urgentistes sur la prise en charge des intoxications au monoxyde de carbone en région Auvergne-Rhône-Alpes

Objectif : L’intoxication au monoxyde de carbone (ICO) est un diagnostic souvent difficile en urgence. Son incidence restant faible, les médecins urgentistes (MU) y sont rarement confrontés mais la pertinence de leur prise en charge est essentielle pour limiter la morbi-mortalité. L’objectif principal de cette étude était d’évaluer le niveau de connaissance des MU sur la prise en charge des ICO dans une région française de 8,1 millions d’habitants. L’objectif secondaire était d’individualiser les facteurs associés à une bonne connaissance de la prise en charge en urgence de cette pathologie.

Matériel et méthodes : Étude descriptive multicentrique et déclarative, réalisée auprès de MU travaillant au sein de cette région à l’aide d’un questionnaire en ligne.

Résultat : 246 MU ont répondu à l’enquête, représentant 82 % des structures de médecine d’urgence de la région. Parmi eux, 27 % estimaient prendre en charge moins de deux ICO par an. Le protocole territorial était connu par 59 % des répondeurs. La médiane de réponses justes au questionnaire de connaissance était de 43 [40-47] sur 60. Un taux de réponses justes plus faible (< 70 %) était retrouvé sur les questions traitant du diagnostic (65 %) et des indications et contre-indications de l’oxygénothérapie hyperbare (61 %). Les facteurs associés à un meilleur taux de réponses justes étaient : la connaissance du protocole territorial (63 vs 46 %, p = 0,035), une ancienneté d’exercice ≥ 5 ans (60 vs 40 %, p = 0,014), une formation complémentaire à la médecine hyperbare (85 vs 53 %, p = 0,018), un nombre estimé de prise en charge d’ICO ≥ 2 (60 vs 43 %, p = 0,022) et une auto-évaluation de ses connaissances > 7/10 (68 vs 50 %, p = 0,007).

Conclusion : Cette étude a montré un niveau de connaissance perfectible des MU sur cette pathologie en rapport avec un faible nombre de prise en charge annuel. La création d’un consensus national est à encourager pour améliorer les pratiques.

Repeated unconsciousness due to chronic carbon monoxide poisoning in an older patient: a case report

Objective: Although much is known about acute carbon monoxide (CO) poisoning, little is known about chronic CO poisoning. Chronic CO poisoning is often diagnosed based on the patient's living environment and medical history. Herein, we report the case of an older patient who presented with repeated unconsciousness due to chronic CO poisoning. Case presentation: A 90-year-old man was brought to the emergency department after being found at home with a disturbance of consciousness. Arterial blood gas measurements in room air revealed a carboxyhemoglobin level of 18.0%. Impaired consciousness was caused by chronic CO poisoning. The patient received high-flow oxygen therapy, which promptly improved his condition. According to his family, briquette kotatsu was the cause of chronic CO poisoning. Conclusion: Although high-flow oxygen therapy has been said to be less effective than hyperbaric oxygen therapy in CO poisoning treatment, recent studies have demonstrated that high-flow oxygen has similar effects and benefits. Thus, in institutions that do not have hyperbaric oxygen, high-flow oxygen may be sufficient to treat patients with CO poisoning, as seen in the present case. It should be noted that briquette kotatsu can lead to CO poisoning. This case highlights the need for clinicians to consider patients' living conditions.

Use of hyperbaric oxygen therapy for preventing delayed neurological sequelae in patients with carbon monoxide poisoning: A multicenter, prospective, observational study in Japan

BACKGROUND

The purpose of this study was to clarify the practical clinical treatment for acute carbon monoxide (CO) poisoning in Japan and to investigate the efficacy of hyperbaric oxygen (HBO2) therapy in preventing delayed neurological sequelae (DNS) in the acute phase of CO poisoning.

METHODS

We conducted a multicenter, prospective, observational study of acute CO poisoning in Japan. Patients with acute CO poisoning were enrolled and their treatment details were recorded. The primary endpoint was the onset of DNS within 2 months of CO exposure. Factors associated with DNS were assessed with logistic regression analysis.

RESULTS

A total of 311 patients from 57 institutions were registered and 255 were analyzed: 171 received HBO2 therapy (HBO2 group) and 84 did not (normobaric oxygen [NBO2] group). HBO2 therapy was performed zero, once, twice, or three times within the first 24 h in 1.8%, 55.9%, 30.9%, and 11.3% of the HBO2 group, respectively. The treatment pressure in the first HBO2 session was 2.8 ATA (47.9% of the HBO2 group), 2.0 ATA (41.8%), 2.5 ATA (7.9%), or another pressure (2.4%). The incidence of DNS was 13/171 (7.6%) in the HBO2 group and 3/84 (3.6%) in the NBO2 group (P = 0.212). The number of HBO2 sessions in the first 24 h was one of the factors associated with the incidence of DNS (odds ratio, 2.082; 95% confidence interval, 1.101-3.937; P = 0.024).

CONCLUSIONS

The practical clinical treatment for acute CO poisoning, including HBO2 therapy, varied among the institutions participating in Japan. HBO2 therapy with inconsistent protocols showed no advantage over NBO2 therapy in preventing DNS. Multiple HBO2 sessions was associated with the incidence of DNS.

Neurocognitive sequelae after carbon monoxide poisoning and hyperbaric oxygen therapy

Carbon monoxide (CO) has been the leading cause of poisoning mortality in many countries and hyperbaric oxygen (HBO) is a widely accepted treatment for CO poisoning. However, some patients with CO poisoning will still develop neurocognitive sequelae regardless of HBO therapy, which can persist since CO poisoning or be present days to weeks after a recovery from CO poisoning. HBO has been used in the prevention and treatment of neurocognitive sequelae after CO poisoning, and some mechanisms are also proposed for the potential neuroprotective effects of HBO on the neurocognitive impairment after CO poisoning, but there is still controversy on the effectiveness of HBO on neurocognitive sequelae after CO poisoning. In this paper, we briefly introduce the neurocognitive sequelae after CO poisoning, summarize the potential predictive factors of neurocognitive sequelae, and discuss the use of HBO in the treatment and prevention of neurocognitive sequelae after CO poisoning.

Hyperbaric Oxygen Therapy in Management of Diabetic Foot Ulcers: Indocyanine Green Angiography May Be Used as a Biomarker to Analyze Perfusion and Predict Response to Treatment

SUMMARY

The authors present indocyanine green angiography to assess the effects of hyperbaric oxygen therapy and as a potential biomarker to predict healing of chronic wounds. They hypothesize that favorable initial response to hyperbaric oxygen therapy (improved perfusion) would be an early indicator of eventual response to the treatment (wound healing). Two groups were recruited: patients with chronic wounds and unwounded healthy controls. Inclusion criteria included adults with only one active wound of Wagner grade III diabetic foot ulcer or caused by soft-tissue radionecrosis. Patients with chronic wounds underwent 30 to 40 consecutive hyperbaric oxygen therapy sessions, once per day, 5 days per week; controls underwent two consecutive sessions. Indocyanine green angiography was performed before and after the sessions, and perfusion patterns were analyzed. Healing was determined clinically and defined as full skin epithelialization with no clinical evidence of wound drainage. Fourteen chronic-wound patients and 10 controls were enrolled. Unlike unwounded healthy volunteers, a significant increase in indocyanine green angiography perfusion was found in chronic-wound patients immediately after therapy (p < 0.03). Moreover, the authors found that 100 percent of the wounds that demonstrated improved perfusion from session 1 to session 2 went on to heal within 30 days of hyperbaric oxygen therapy completion, compared with none in the subgroup that did not demonstrate improved perfusion (p < 0.01). This study demonstrates a beneficial impact of hyperbaric oxygen therapy on perfusion in chronic wounds by ameliorating hypoxia and improving angiogenesis, and also proposes a potential role for indocyanine green angiography in early identification of those who would benefit the most from hyperbaric oxygen therapy.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Increased Risk of Congestive Heart Failure Following Carbon Monoxide Poisoning

BACKGROUND

Carbon monoxide poisoning (COP) is an important public health issue around the world. It may increase the risk of myocardial injury, but the association between COP and congestive heart failure (CHF) remains unclear. We conducted a study incorporating data from epidemiological and animal studies to clarify this issue.

METHODS

Using the National Health Insurance Database of Taiwan, we identified patients with COP diagnosed between 1999 and 2012 and compared them with patients without COP (non-COP cohort) matched by age and the index date at a 1:3 ratio. The comparison for the risk of CHF between the COP and non-COP cohorts was made using Cox proportional hazards regression. We also established a rat model to evaluate cardiac function using echocardiography and studied the pathological changes following COP.

RESULTS

The 20 942 patients in the COP cohort had a higher risk for CHF than the 62 826 members in the non-COP cohort after adjusting for sex and underlying comorbidities (adjusted hazard ratio, 2.01 [95% CI, 1.74-2.32]). The increased risk of CHF persisted even after 2 years of follow-up (adjusted hazard ratio, 1.85 [95% CI, 1.55-2.21]). In the animal model, COP led to a decreased left ventricular ejection fraction on echocardiography and damage to cardiac cells with remarkable fibrotic changes.

CONCLUSIONS

Our epidemiological data showed an increased risk of CHF was associated with COP, which was supported by the animal study. We suggest close follow-up of cardiac function for patients with COP to facilitate early intervention and further studies to identify other long-term effects that have not been reported in the literature.

Optimal sessions of hyperbaric oxygen therapy in patients with carbon monoxide poisoning: A prospective observational study

INTRODUCTION

Hyperbaric oxygen (HBO) therapy may be a useful treatment to prevent the development of delayed neuropsychiatric sequelae (DNS) in patients with acute carbon monoxide (CO) poisoning. However, there is no clear consensus regarding the optimal number of HBO therapy sessions in patients with CO poisoning. Here, we compared the development of DNS after 3 and > 3 sessions of HBO therapy in patients with acute CO poisoning.

METHODS

This prospective observational study recruited 299 patients with CO poisoning. Demographic and clinical information were obtained, including comorbidities, vital signs, and symptoms. Patients were divided into two groups according to whether they received 3 or > 3 sessions of HBO therapy (3 HBO vs. >3 HBO). A propensity score-matching process was used to balance potential prognostic factors in both groups.

RESULTS

Of the 299 patients with acute CO poisoning enrolled in this study, 183 (59.0%) were included in the analysis. Patients were excluded for the following reasons: age < 18 years, not underwent HBO therapy, discharged against medical advice, and loss to follow-up. The overall rate of DNS development was 17.5%. The >3 HBO group had a higher incidence of DNS development compared to the 3 HBO group (36.3% vs. 16.3%; p = 0.09). Propensity score-matching analysis revealed similar incidences of DNS (31.3% vs. 28.1%, respectively; p > 0.99).

CONCLUSIONS

There is a critical need to determine the optimal number of HBO therapy sessions for patients with acute CO poisoning. This study showed no difference in DNS development after 3 and > 3 sessions of HBO therapy.

Memory Impairment and Hippocampal Volume after Carbon Monoxide Poisoning

OBJECTIVE

We report longitudinal changes in neuroimaging and neuropsychological measurements in a case of carbon monoxide (CO) poisoning showing reversible changes in hippocampal volume, which was closely linked to the degree of memory impairment.

METHODS

The current study presents a female in her early 20s, with a high school level of education. She became aware of headaches and drowsiness while working in a restaurant that operated charcoal braziers, and she was urgently transported to our hospital. Her high blood carboxyhemoglobin concentration led to a diagnosis of CO poisoning, but no obvious abnormalities were found by brain magnetic resonance imaging (MRI) and physical examinations. She underwent a series of hyperbaric oxygen therapies. One year after CO poisoning, she consulted a psychiatrist due to her own awareness of gradually worsening memory function. She was assessed by brain MRI and standard neuropsychological tests every 6 months for 1 year.

RESULTS

Her neuropsychological profile showed the impairment of memory function according to a low score of Delayed Recall Index of Wechsler Memory Scale-Revised. At 320 days after CO poisoning, her hippocampal volume had decreased by 3%. Her memory function was found to have improved at 530 days after CO poisoning. Of note, during this period, her hippocampal volume had increased by approximately 7%.

CONCLUSIONS

This report suggests that a clinician should conduct careful neuropsychological examinations to avoid overlooking mild sequelae of CO poisoning, even if a general assessment of brain MRI is normal.

Autoimmune Connective Tissue Disease Following Carbon Monoxide Poisoning: A Nationwide Population-Based Cohort Study

Background

In addition to hypoxia, oxidative stress and inflammation due to carbon monoxide (CO) poisoning cause adverse health effects. These mechanisms are related to the occurrence of autoimmune connective tissue disease, but studies on the association between CO poisoning and autoimmune connective tissue disease are limited. We conducted a study to evaluate the occurrence of autoimmune connective tissue disease following CO poisoning.

Methods

We identified participants with CO poisoning diagnosed between 1999 and 2012 from the Nationwide Poisoning Database and selected participants without CO poisoning from the Taiwan National Health Insurance Research Database with matching age and index dates at a 1:3 ratio. Sex, underlying comorbidities, and monthly income were also included in the analyses. We followed up the participants until 2013 and made comparison of the risk of autoimmune connective tissue disease between participants with and without CO poisoning.

Results

The 23,877 participants with CO poisoning had a higher risk for autoimmune connective tissue disease than the 71,631 participants without CO poisoning (adjusted hazard ratio [AHR], 3.5; 95% confidence interval [CI], 3.1–3.9) after adjustment for sex, diabetes, Lyme disease, herpes zoster, infectious mononucleosis, hepatitis, HIV infection, liver disease, renal disease, non-CO poisoning or drug abuse, malignancy, hypertension, hyperlipidemia, coronary artery disease, congestive heart failure, chronic obstructive pulmonary disease, and monthly income. An increased risk was observed even after 4 years of follow-up (AHR, 3.6; 95% CI, 3.0–4.4).

Conclusion

The risk of autoimmune connective tissue disease increased following CO poisoning. Close follow-up of the patients with CO poisoning for the development of connective tissue disease is recommended, and further investigation of the detailed mechanisms is warranted.

Impact of carbon monoxide poisoning on the risk of breast cancer

Carbon monoxide (CO) is a toxic gas and an endogenous signaling molecule. Some studies involving cell lines have revealed the potential antibreast cancer effects of CO. Data on such effects in humans, however, are limited. Thus, we conducted a study on patients with CO poisoning (COP) to evaluate the effects of CO on the risk of breast cancer. We identified female patients who were diagnosed with COP over the period of 2002 and 2009 from the Nationwide Poisoning Database of Taiwan. For comparison, we selected females without COP from the National Health Insurance Research Database. Participants in the COP and comparison cohorts were matched on the index year, age, monthly income, and geographic region of residence at a 1:6 ratio. We followed up the two cohorts until the end of 2014 and compared their risks of developing breast cancer. We included 7053 participants with COP and 42,318 participants without COP. Participants with COP were at a lower risk of developing breast cancer than those without COP (0.7% vs. 1.0%, p < 0.001). Cox proportional hazard regression analyses revealed that COP was associated with a hazard ratio of 0.67 (95% confidence interval [95% CI] 0.50–0.90) for breast cancer after we adjusted for age, monthly income, geographic region, and comorbidities of hypertension, diabetes, and hyperlipidemia. Our result provides evidence for the potential protective effects of CO against breast cancer in humans. Further studies that directly evaluate the potential effects are warranted.

Pediatric Veno-Veno Extracorporeal Membrane Oxygenation Rescue From Carbon Monoxide Poisoning

BACKGROUND

Carbon monoxide poisoning affects approximately 5000 children per year and can be challenging to diagnose and treat (Pediatr Emerg Med Pract. 2016;13:1-24). It is in the differential diagnosis of a patient presented with altered consciousness. Patients may look quite "pink" and well perfused, but are often in serious distress. We present the first case in the literature of carbon monoxide poisoning treated with the use of veno-veno extracorporeal membrane oxygenation (ECMO).

CASE

We report the case of a 10-year-old patient who had carbon monoxide poisoning (carboxyhemoglobin of 18%). She was treated with hydroxocobalamin at 70 mg/kg and was being prepared to transfer to a facility that offered hyperbaric therapy when she suffered a cardiac arrest requiring cardiopulmonary resuscitation. After 11 minutes of resuscitation, she had return of spontaneous circulation and an echocardiogram showed reasonable cardiac function. She was judged too unstable for ambulance transport and the ECMO team was called. Veno-veno ECMO was placed via a single right internal jugular dual-lumen catheter with fluoroscopy in the cardiac catheterization laboratory. There was a rapid improvement in carboxyhemoglobin level, and the ECMO therapy was weaned the next day. The patient eventually made a full recovery.

CONCLUSIONS

This is the first time that veno-veno ECMO has been reported for the emergent treatment of carbon monoxide intoxication. If emergency physicians are treating such a patient and cannot administer hyperbaric oxygen therapy, ECMO represents a valuable alternative that is not commonly thought of in this situation before.

Chronic Pain Increases the Risk for Major Adverse Cardiac and Cerebrovascular Events: A Nationwide Population-Based Study in Asia

OBJECTIVE

Chronic pain (CP) may increase the risk for major adverse cardiac and cerebrovascular events (MACCEs); however, this issue is still unclear in the Asian population. We conducted this study to delineate it.

DESIGN

From the Taiwan National Health Insurance Research Database, we identified 17,614 participants (<65 years) with CP and matched them by age and sex at a 1:2 ratio to participants without CP, who made up the comparison cohort. Several causes of CP and its underlying comorbidities were also analyzed.

OUTCOME MEASURE

A comparison of MACCE occurring in the two cohorts was performed via follow-up until 2015.

RESULTS

The mean age (SD) was 50.2 (11.5) years and 50.4 (11.7) years in participants with and without CP, respectively. In both cohorts, the percentage of female participants was 55.5%. Common causes of CP were spinal disorders (23.9%), osteoarthritis (12.4%), headaches (11.0%), gout (10.2%), malignancy (6.2%), and osteoporosis (4.5%). After adjusting for hypertension, diabetes, chronic obstructive pulmonary disease, renal diseases, hyperlipidemia, liver diseases, dementia, and depression, participants with CP had a higher risk for MACCE than those without CP (adjusted hazard ratio [AHR] = 1.3, 95% confidence interval [CI] = 1.3 - 1.4). After conducting subgroup analyses, an increased risk was also found for all-cause mortality (AHR = 1.4, 95% CI = 1.1 - 1.8), acute myocardial infarction (AHR = 1.2, 95% CI = 1.0 - 1.4), and stroke (AHR = 1.3, 95% CI = 1.3 - 1.4).

CONCLUSIONS

CP is associated with increased occurrence of MACCE. Early detection and interventions for CP are suggested.

Hyperbaric Oxygen Therapy: Descriptive Review of the Technology and Current Application in Chronic Wounds

Hyperbaric oxygen therapy (HBOT) serves as "primary" or "adjunctive" therapy in a wide range of pathologies. It is considered the mainstay of management for potentially life-threatening conditions such as carbon monoxide poisoning, decompression illness, and gas embolisms. Moreover, HBOT has been utilized for decades as an adjunctive therapy in a variety of medical disciplines, including chronic wounds, which affect approximately 6.5 million Americans annually. In general, chronic wounds are characterized by hypoxia, impaired angiogenesis, and prolonged inflammation, all of which may theoretically be ameliorated by HBOT. Nonetheless, the cellular, biochemical, and physiological mechanisms by which HBOT achieves beneficial results in chronic wounds are not fully understood, and there remains significant skepticism regarding its efficacy. This review article provides a comprehensive overview of HBOT, and discusses its history, mechanisms of action, and its implications in management of chronic wounds. In particular, we discuss the current evidence regarding the use of HBOT in diabetic foot ulcers, while digging deeply into the roots of controversy surrounding its efficacy. We discuss how the paucity of high-quality research is a tremendous challenge, and offer future direction to address existing obstacles.

Usefulness of N-terminal pro-B-type natriuretic peptide (NT-ProBNP) as a marker for cardiotoxicity and comparison with echocardiography in paediatric carbon monoxide poisoning

OBJECTIVES

To demonstrate the usefulness of N-Terminal Pro-B-Type natriuretic peptide (NT-proBNP) as an early biomarker of carbon monoxide-induced myocardial injury in children. It also aimed to identify the correlation between NT-proBNP and left ventricular systolic dysfunction findings shown by echocardiography.

METHODS

Prospective, observational study conducted at a paediatric emergency department between October 2017 and April 2019 which involved children aged 0-17 years. The patients were divided into three groups based on severity; mild, moderate and severe groups. The patient characteristics, carboxyhaemoglobin, CK-MB Mass (CKMB-M), troponin-T, and NT-proBNP levels were measured, and echocardiography was performed and left ventricular ejection fraction was measured.

RESULTS

Sixty-nine patients and 60 healthy controls were included. Male gender, younger age, higher carboxyhaemoglobin levels, and altered mental status were found as independent predictors of carbon monoxide-induced myocardial injury. If the cut-off value for NT-proBNP level is >480 pg/ml, the sensitivity-specificity for decreased left ventricular ejection fraction, which is the strongest carbon monoxide-induced myocardial injury sign, were 100-96%, respectively. A high negative correlation was found between NT-proBNP levels and left ventricular ejection fraction (r = -0.769, p < 0.01) in the carbon monoxide poisoning group, and there was a positive correlation between the carboxyhaemoglobin and NT-proBNP levels (r = 0.583, p < 0.01).

CONCLUSION

Echocardiography is an ideal tool and very sensitive, but its routine use is limited due to its non-availability. An increased level of NT-proBNP (>480pg/ml) may be useful as an ideal biomarker for early detection of carbon monoxide-induced myocardial injury sign and reduced left ventricular ejection fraction which is the most crucial point in making a decision on hyperbaric oxygen therapy.

Hyperbaric oxygen ameliorates cognitive impairment in patients with Alzheimer's disease and amnestic mild cognitive impairment

INTRODUCTION

It has been reported that environmental factors such as hypoxia could contribute to the pathogenesis of Alzheimer's disease (AD). Therapeutics like hyperbaric oxygen treatment, which improves tissue oxygen supply and ameliorates hypoxic conditions in the brain, may be an alternative therapy for AD and amnestic mild cognitive impairment (aMCI). The present work aims to investigate the potential therapeutic effect of hyperbaric oxygen treatment for AD and aMCI.

METHODS

We recruited 42 AD, 11 aMCI, and 30 control AD patients in this study. AD and aMCI patients were treated with 40 minutes of hyperbaric oxygen once a day for 20 days and assessed by neuropsychiatric assessments including Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), and Activities of Daily Living (ADL) scale before and at 1-, 3-, and 6-month follow-up after treatment. Control AD patients who were not given hyperbaric oxygen treatment had similar clinical profile as hyperbaric oxygen treated AD. We examined 10 of the AD/aMCI patients with fluorodeoxyglucose positron emission tomography.

RESULTS

In self-comparison study, one course of hyperbaric oxygen treatment significantly improved the cognitive function assessed by MMSE and MoCA in AD patients after 1-month follow-up; such treatment also significantly improved MMSE score at 3-month follow-up and MoCA score at 1- and 3-month follow-up in aMCI patients. The ADL scale was significantly improved in AD patients after 1- and 3-month follow-up. Compared to the control AD patients, the MMSE and MoCA in hyperbaric oxygen treated AD patients were significantly improved after 1-month follow-up. Hyperbaric oxygen treatment also ameliorated the reduced brain glucose metabolism in some of the AD and aMCI patients.

CONCLUSION

Based on previous studies and our recent findings, we propose that hyperbaric oxygen treatment may be a promising alternative therapy for AD and aMCI.

Cardiac injury after acute carbon monoxide poisoning and its clinical treatment scheme

This study was designed to investigate cardiac injury after acute carbon monoxide poisoning and its clinical treatment scheme. Seventy patients with moderate and severe acute carbon monoxide poisoning (ACOP) admitted from January 2017 to December 2018 into The Affiliated Hospital of Qingdao University were regarded as a research group (RG), and another 30 healthy adults undergoing physical examination in the hospital during the same period were selected as a control group (CG). Thirty-five patients in the RG who received hyperbaric oxygen therapy were considered as group A, and 35 patients who received extracorporeal membrane oxygenation therapy were considered as group B. The effective rates and complications of the two groups after treatment were compared. The concentrations of creatine kinase isoenzyme (CK-MB) and lactate dehydrogenase (LDH) of myocardial enzymes at different time points before and after treatment were detected. Expression of miR-30a in the blood of experimental subjects was detected by time-fluorescence quantitative PCR, and the relationship between miR-30a expression and ACOP patients was analyzed. Patients in groups A and B achieved obvious efficacy, but the effective rate and incidence rate of complications in the extracorporeal membrane oxygenation (ECMO) group were better than those in the hyperbaric oxygen group. The concentrations of CK-MB and LDH in group A and group B were significantly higher than those in control group (P<0.01). The expression level of miR-30a in the RG was significantly higher than that in the control group (P<0.05). Both hyperbaric oxygen therapy and ECMO therapy have obvious efficacy on ACOP patients, but the latter is better than the former. The expression level of miR-30a in blood of ACOP patients increased significantly, which is positively correlated with myocardial injury, and it decreased after treatment. It is believed that miR-30a can provide a reference index for early diagnosis and prediction of disease progression and prognosis in cardiac injury of ACOP.

Blood carboxyhemoglobin elimination curve, half-lifetime, and arterial-venous differences in acute phase of carbon monoxide poisoning in ovine smoke inhalation injury model

Smoke inhalation injury (SII) affects more than 50,000 people annually causing carbon monoxide (CO) poisoning. Although the increased blood level of carboxyhemoglobin (CO-Hb) is frequently used to confirm the diagnosis of SII, knowledge of its elimination in the acute phase is still limited. The aim of this study is to determine CO-Hb elimination rates and their differences in arterial (aCO-Hb) and mixed-venous (vCO-Hb) blood following severe SII in a clinically relevant ovine model. Forty-three chronically instrumented female sheep were subjected to SII (12 breaths, 4 sets) through tracheostomy tube under anesthesia and analgesia. After the SII, sheep were awakened and placed on a mechanical ventilator (FiO₂ = 1.0, tidal volume 12 mL/kg, and PEEP = 5cmH₂O) and monitored. Arterial and mixed-venous blood samples were withdrawn simultaneously for blood gas analysis at various time points to determine CO-HB half-lifetime and an elimination curve. The mean of highest aCO-Hb level during SII was 70.8 ± 13.9%. The aCO-Hb elimination curve showed an approximated exponential decay during the first 60 min. Per mixed linear regression model analysis, aCO-Hb significantly (p < 0.001) declined (4.3%/minute) with a decay constant lambda of 0.044. With this lambda, mean lifetime and half-lifetime of aCO-Hb were 22.7 and 15.7 min, respectively. The aCO-Hb was significantly lower compared to vCO-Hb at all-time points (0-180 min). To our knowledge, this is the first report describing CO-Hb elimination curve in the acute phase after severe SII in the clinically relevant ovine model. Our data shows that CO-Hb is decreasing in linear manner with supportive mechanical ventilation (0-60 min). The results may help to understand CO-Hb elimination curve in the acute phase and improvement of pre-hospital and initial clinical care in patients with CO poisoning.

Carbon monoxide intoxication in geriatric patients: How important are lactate values at admission?

PURPOSE

The aim of this study was to investigate the demographic and clinical characteristics and treatment modalities of elderly patients with carbon monoxide (CO) intoxication. The secondary aim was to evaluate the importance of plasma lactate values in the diagnosis of acute CO intoxication in geriatric patients.

METHODS

Data on geriatric patients who were admitted to the emergency department of Atatürk University Medical Faculty between January 2013 and April 2016 were analyzed retrospectively.

RESULTS

Of the 197 cases included in the study, 97 were in the intoxication group and 100 were in the control group; 82.5% of the intoxication cases had mild neurological symptoms and 17.5% had severe neurological symptoms. Carboxyhemoglobin levels were significantly higher in patients with severe neurological symptoms (p = 0.031). All patients with severe neurological symptoms received hyperbaric-oxygen therapy (p < 0.001). In the intoxication group, lactate levels were significantly higher than in the control group (p = 0.001). The specificity for lactate 4 mmol/L and above was found as 98.0% with a positive predictive value and negative predictive value of 84.5% and 53.3%, respectively.

CONCLUSION

High initial lactate levels may be a guide for cases with nonspecific symptoms in geriatric patients with suspected CO intoxication.

Prognostic factors of carbon monoxide poisoning in Taiwan: a retrospective observational study

OBJECTIVES

To identify the risk factors related to the prognosis of carbon monoxide (CO)-poisoned patients in the hospital.

DESIGN

Retrospective observational study.

SETTING

Tri-Service General Hospital, Taiwan.

METHODS

We conducted a review of the medical records of 669 CO-poisoned patients, who were admitted to the Department of Emergency, Tri-Service General Hospital, Taiwan, from 2009 to 2014. Demographic, clinical and laboratory data were collected for analysis. In the study, the end points for poor outcome were patients who either still had sequelae, were bedridden or died after treatment. The independent t-test, χ² test and binary logistic regression were used to identify the association between the prognostic factors and the outcomes.

RESULTS

The logistic regression analysis confirmed that the Glasgow Coma Scale (GCS) score (p=0.008) and blood urea nitrogen (BUN) (p=0.002) were related to poor outcomes. Furthermore, the receiver operating characteristic (ROC) curve showed that the cut-off point of intubation days was 1.5 days (area under the ROC curve [AUC]=0.793) for all patients and 2.5 days (AUC=0.817) for patients with intubation when predicting poor outcomes.

CONCLUSION

We identified the factors that most strongly predict the prognosis of CO poisoning, including the GCS score, serum BUN and intubation days. Moreover, the number of hyperbaric oxygen treatments seems to have impact of the outcome.

Incidence Rate and Predictors of Globus Pallidus Necrosis after Charcoal Burning Suicide

Objective: This study examined predictors of globus pallidus necrosis as there was a paucity of literature of globus pallidus necrosis resulted from carbon monoxide poisoning after charcoal burning suicide. Methods: A total of 67 patients who had attempted charcoal burning suicide were recruited and stratified into two subgroups based on either presence (n = 40) or absence (n = 27) of globus pallidus necrosis. Demographic, clinical, laboratory, and radiographic data were obtained for cross-sectional analysis. All patients were followed to investigate the risks for mortality. Results: The patients aged 36.8 ± 11.1 years (67.2%) were male. Patients with globus pallidus necrosis were younger (p = 0.044) and had less hypertension (p = 0.015) than patients without globus pallidus necrosis. Furthermore, patients with globus pallidus necrosis suffered from severer medical complications, i.e., fever (p = 0.008), acute myocardial injury (p = 0.022), acute rhabdomyolysis (p = 0.022), and neuropsychiatric symptoms (p < 0.001) than patients without globus pallidus necrosis. Moreover, patients with globus pallidus necrosis received less hyperbaric oxygen therapy than without necrosis (p = 0.024). Two patients (3.0%) died on arrival. In a multivariable regression model, it was revealed that acute myocardial injury (odds ratio 4.6, confidence interval 1.1–18.9, p = 0.034) and neuropsychiatric symptoms (odds ratio 8.0, confidence interval 2.0–31.4, p = 0.003), decreased blood bicarbonate level (odds ratio 0.8, confidence interval 0.7–1.0, p = 0.032), and younger age (odds ratio 0.9, confidence interval 0.9–1.0, p = 0.038) were significant predictors for globus pallidus necrosis. Conclusion: Although patients who had attempted charcoal burning suicide had a low mortality rate (3.0%), globus pallidus necrosis was not uncommon (59.7%) in this population. Further studies are warranted.

Increased risk for hypothyroidism associated with carbon monoxide poisoning: a nationwide population-based cohort study

Carbon monoxide poisoning (COP) may cause injuries to the central nervous and endocrine systems, which might increase the risk of developing hypothyroidism. We wanted to evaluate the association between COP and the risk of developing hypothyroidism because epidemiological data on this potential association are limited. We conducted a nationwide population-based cohort study using the Nationwide Poisoning Database and identified 24,328 COP subjects diagnosed between 1999 and 2012. By matching the index date and age, we selected 72,984 non-COP subjects for comparison. Subjects with thyroid diseases and malignancy before 1999 were excluded. We followed up the two groups of subjects until 2013 and compared the risk of developing hypothyroidism. COP subjects had a significantly higher risk for hypothyroidism than non-COP subjects (adjusted hazard ratio [AHR]: 3.8; 95% confidence interval [CI]: 3.2-4.7) after adjusting for age, sex, underlying comorbidities, and monthly income, and the AHR was particular higher in subjects with diabetes mellitus, hyperlipidemia, and mental disorder. The increased risk was highest in the first month after COP (AHR: 41.0; 95% CI: 5.4-310.6), and the impact remained significant even after 4 years. In conclusion, COP was associated with an increased risk for hypothyroidism. Further studies regarding the underlying mechanisms are warranted.

Effectiveness of Hyperbaric Oxygenation Versus Normobaric Oxygenation Therapy in Carbon Monoxide Poisoning: A Systematic Review

Carbon monoxide (CO) is a gas product of combustion, considered highly poisonous. Prolonged CO exposure is responsible for more than half of fatal poisonings and is also one of the leading causes of poisoning in Western countries. We aimed to compare the effectiveness of therapy with hyperbaric oxygen (HBO) versus normobaric oxygen (NBO) in the setting of carbon monoxide poisoning (COP). We independently searched the National Library of Medicine's Medline (PubMed™), ScienceDirect™, and Scielo™ for any relevant studies published from 1989 to 2017, using the following keywords: hyperbaric therapy, hyperbaric oxygenation, normobaric therapy, carbon monoxide poisoning, carboxyhemoglobin, Haldane effect. We analyzed the studies that suggested the effectiveness of HBO or NBO. Also, we searched for studies related to COP; including history, epidemiology (risk factors, incidence, demographics), pathophysiology, clinical manifestations, diagnosis, and treatment. Sixty-eight articles were found, sixteen of which dealt with either HBO or NBO or both. Twelve suggested HBO as the treatment of choice in COP; four studies indicated that NBO was an adequate treatment due to its cost-effectiveness and availability in the emergency department (ED). HBO has been shown in several studies to be effective in moderate to high-risk COP situations, being the therapy of choice to avoid sequelae, especially neurologically. NBO can be considered as a reasonable alternative due to its cost-effectiveness. The availability and understanding of different therapeutic interventions are critical in the management of patients with COP in ED and the Critical Care unit.

Effect of Hyperbaric Oxygen on Neurologic Sequelae and All-Cause Mortality in Patients with Carbon Monoxide Poisoning: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND Hyperbaric oxygen (HBO) is used in patients with carbon monoxide (CO) poisoning to prevent the occurrence of delayed neurological sequelae. However, inconsistent results were obtained regarding the treatment effects of HBO. Therefore, the current meta-analysis was conducted based on published randomized controlled trials (RCTs) to determine the effect of HBO on neurologic sequelae and all-cause mortality in patients with CO poisoning. MATERIAL AND METHODS Electronic databases MedLine, EmBase, and the Cochrane Library were searched for relevant RCTs from inception to March 1, 2019. The pooled relative risks (RRs) and weighted mean differences (WMDs) with corresponding 95% confidence intervals (CIs) were calculated to evaluate the outcomes by using a random-effects model. Sensitivity, subgroup, and publication bias analyses were also conducted. RESULTS Seven RCTs, including 9 cohorts and a total of 2023 patients with CO poisoning, were enrolled in this study. The summary results revealed that HBO showed an association with lower risk of memory impairment compared to patients receiving normobaric oxygen (NBO), whereas 2 sessions of HBO showed an association with higher risk of memory impairment compared to those who received 1 session of HBO. Moreover, HBO was associated with increased neuropsychologic scores of block design and trail making when compared with NBO. No other significant differences regarding the treatment effects of HBO were observed. CONCLUSIONS These results indicate that HBO therapy significantly reduces the risk of memory impairment compared to NBO, but 2 sessions of HBO might not be better for memory impairment than 1 session of HBO.

The Diagnosis and Treatment of Carbon Monoxide Poisoning

BACKGROUND

The symptoms of carbon monoxide (CO) poisoning are nonspecific, ranging from dizziness and headache to unconsciousness and death. A German national guideline on the diagnosis and treatment of this condition is lacking at present.

METHODS

This review is based on a selective literature search in the PubMed and Cochrane databases, as well as on existing guidelines from abroad and expert recommendations on diagnosis and treatment.

RESULTS

The initiation of 100% oxygen breathing as early as possible is the most important treatment for carbon monoxide poisoning. In case of CO poisoning, the reduced oxygen-carrying capacity of the blood, impairment of the cellular respiratory chain, and immune-modulating processes can lead to tissue injury in the myocardium and brain even after lowering of the carboxyhemoglobin (COHb) concentration. In patients with severe carbon monoxide poisoning, an ECG should be obtained and biomarkers for cardiac ischemia should be measured. Hyperbaric oxygen therapy (HBOT) should be critically considered and initiated within six hours in patients with neurologic deficits, unconsciousness, cardiac ischemia, pregnancy, and/or a very high COHb concentration. At present, there is no general recommendation for HBOT, in view of the heterogeneous state of the evidence from multiple trials. Therapeutic decision-making is directed toward the avoidance of sequelae such as cognitive dysfunction and cardiac complications, and the reduction of mortality. Smoke intoxication must be considered in the differential diagnosis. The state of the evidence on the diagnosis and treatment of this condition is not entirely clear. Alternative or supplementary pharmacological treatments now exist only on an experimental basis.

CONCLUSION

High-quality, prospective, randomized trials that would enable a definitive judgment of the efficacy of HBOT are currently lacking.

Long-Distance Transportation of Carbon Monoxide-Poisoned Patients on Extracorporeal Membrane Oxygenation Seems Possible: A Porcine Feasibility Study

OBJECTIVE

Extracorporeal membrane oxygenation (ECMO) has been widely used to stabilize patients with impairment of cardiac/respiratory function, and ECMO has been used to stabilize cardiopulmonary insufficiency caused by carbon monoxide (CO) poisoning in a porcine model. Airborne transportation in fixed wing aircraft of patients suffering from CO poisoning is challenging because as the air pressure drops, the oxygen content falls correspondingly. The aim of this study was to show the feasibility of cannulating and establishing ECMO therapy during airborne transportation after severe CO poisoning in a porcine model.

METHODS

An anesthetized pig was subjected to severe CO poisoning and loaded onto a Hercules aircraft. Cardiac arrest was induced at an altitude of 8,000 feet, after which cannulation and the establishment of venoarterial (VA) ECMO were performed. Vital signs were monitored, and arterial blood samples were analyzed while airborne.

RESULTS

CO poisoning was induced with carboxyhemoglobin at 58% before takeoff. We successfully cannulated the animal in-flight during cardiac arrest and initiated VA ECMO. The animal regained spontaneous circulation and was successfully weaned from ECMO. During VA ECMO, PaO₂ was maintained at high levels (420-615 mm Hg).

CONCLUSION

It is possible to cannulate and initiate VA ECMO treatment as airborne en route therapy for cardiac arrest and severe CO intoxication in a porcine model.