Effect of Hyperbaric Oxygen Therapy Initiation Time in Acute Carbon Monoxide Poisoning

Effects of Smoking on Neurocognitive Outcomes in Patients with Carbon Monoxide Poisoning

Background/Objectives: The concept of the "smoker's paradox" in prior research posits that smoking could potentially offer neuroprotective effects in cases of acute carbon monoxide (CO) poisoning. This study aimed to determine the validity of this hypothesis by minimizing selection bias and confounding variables in a comparison of neurocognitive outcomes between smokers and non-smokers following acute CO poisoning. Methods: A total of 1150 patients were included in this retrospective study. Propensity Score Matching (PSM) was used to control for variables such as age, initial Glasgow Coma Scale (GCS) score, co-morbidities, and HBO2 therapy application. Neurocognitive outcomes were assessed and compared between smokers and non-smokers. Results: In the initial analysis, 1150 patients were divided into non-smoking (61.7%) and smoking (38.3%) groups. Before PSM, smokers had a lower rate of poor outcomes (12.1% vs. 6.8%, p = 0.004). However, baseline differences emerged, with non-smokers being older with longer CO exposure, while smokers had more males and higher rates of intentional CO poisoning and drug ingestion. Smokers had a 0.56 times lower relative risk of poor outcomes compared to non-smokers (95% CI: 0.38-0.84, p = 0.004). After meticulous 1:1 PSM with 15 covariates, 317 patient pairs were matched, creating balanced cohorts. Neurocognitive outcomes at 1 month post-CO exposure showed no significant differences between matched non-smoking and smoking groups (9.8% vs. 7.9%, p = 0.461). Post-PSM, the relative risk for poor outcomes remained approximately 0.81 times lower in smokers compared to non-smokers, but with no statistical significance [0.81 (95% CI: 0.49-1.33, p = 0.402)]. Conclusions: Our findings do not support the idea of a protective effect from smoking in the context of acute CO poisoning. After accounting for potential confounders through PSM, we found that smoking status was not significantly associated with more favorable neurocognitive outcomes.

Rapid Initiation of Hyperbaric Oxygen Therapy for Multiple Simultaneous Cases of Acute Carbon Monoxide Poisoning at a Single Center

INTRODUCTION

Hyperbaric oxygen therapy (HBOT) is used to treat acute carbon monoxide poisoning. However, few reports have detailed its use in large patient cohorts, and optimal management guidelines have yet to be established. Herein, we report the clinical presentation and simultaneous treatment of multiple patients experiencing acute carbon monoxide poisoning on an offshore ship within the territorial waters of Japan.

CASE PRESENTATION

Eleven patients were promptly transported to our hospital from a Japanese Maritime Self-Defense Force destroyer owing to accidental acute carbon monoxide poisoning. We opted to treat this incident as a mass casualty and immediately appointed a medical control officer and established medical teams. The medical control officer guided the general treatment plan and coordinated with the various sections, and the medical teams treated the patients. The patients were immediately administered normobaric oxygen via a facial mask. Those with the most severe conditions underwent simultaneous HBOT within 3 hours of hospital arrival. Two and 4 weeks after the second therapy session, all symptoms had resolved, with no physical or cognitive sequelae.

CONCLUSION

We report the successful treatment of patients with concurrent acute carbon monoxide poisoning via HBOT at a single facility. This report highlights the feasibility of efficacious treatment at a single facility in scenarios in which multiple individuals experience carbon monoxide poisoning. It is important that all staff members, including those in administration, understand the concept of disaster medicine. Additionally, in HBOT facilities, regular training is needed for events involving a large number of HBOT-indicated patients.

Hyperbaric oxygen therapy for acute carbon monoxide poisoning patients with coma onset

OBJECTIVE

This study aimed to evaluate the effects of coma on the prognosis and delayed encephalopathy in patients with acute carbon monoxide poisoning (DEACMP) and to analyze the predictive factors affecting the prognosis of these patients.

METHODS

Patients with acute carbon monoxide poisoning were divided into comatose and non-comatose groups. The primary outcomes included clinical cure and the occurrence of DEACMP. Multivariate logistic regression analysis was performed to identify independent predictors of clinical outcome.

RESULTS

Multivariate analysis indicated that coma (clinical cure: adjusted odds ratio [aOR] 0.24, 95% CI 0.12-0.47; DEACMP: aOR 42.5, 95% CI 7.99-789), longer the time from onset to the first HBOT (clinical cure: aOR 0.43, 95% CI 0.24-0.77; DEACMP: aOR 3.21, 95% CI 1.56-6.78) and abnormal chest CT findings (clinical cure: aOR 0.23, 95% CI 0.12-0.45; DEACMP: aOR 5.36, 95% CI 2.41-12.60) were associated with a lower rate of clinical cure and a higher proportion of DEACMP; and lower age was an independent predictor of clinical cure (aOR 0.96, 95% CI 0.94-0.98), but not of DEACMP (aOR 0.99, 95% CI 0.96-1.01). In comatose patients, both the duration of coma and abnormal chest CT findings were an independent factor for clinial cure (aOR 0.96, 95% CI 0.93-0.99; aOR 0.34, 95% CI 0.15-0.74) and DEACMP (aOR 1.09, 95% CI 1.06-1.14; aOR 4.93, 95% CI 1.67-16.30).

CONCLUSION

Coma and the duration of coma were significant predictors of clinical cure and DEACMP in patients; the older the patient, the longer the duration of coma, and the longer the time from onset to the first hyperbaric oxygen therapy (> 6 h), indicating that the patient's prognosis is often worse; abnormal chest CT manifestations were also an independent risk factor for a poor patient's prognosis.

Early and late adverse clinical outcomes of severe carbon monoxide intoxication: A cross-sectional retrospective study

BACKGROUND

Carbon monoxide (CO) results from incomplete combustion of carbon-based materials, causing symptoms such as headaches, dizziness, nausea, chest pain, confusion, and, in severe cases, unconsciousness. Normobaric oxygen therapy (NBOT) is the standard therapy, whereas hyperbaric oxygen therapy (HBOT) is recommended in severe cases of organ damage. This study examined the early and late adverse outcomes in patients with severe CO poisoning.

MATERIALS AND METHODS

This study analyzed severe cases of CO poisoning among patients admitted to the emergency department between January 2020 and May 2022. The demographic, clinical, and laboratory data of symptomatic individuals and those requiring HBOT were examined. The study recorded early outcomes, such as intubation and in-hospital mortality, and late outcomes, such as delayed neurological sequelae and 1-year mortality. Chi-square tests, Spearman's rho correlation tests, and logistic regression analyses were performed to identify factors affecting these outcomes.

RESULTS

Patients who received HBOT showed a significant difference in delayed neurological sequelae (DNS) compared to those who received NBOT (p = 0.037). Significant differences were observed in the need for intubation, in-hospital mortality, and 1-year mortality between patients based on COHb levels, but no significant differences were found in DNS. The 1-year mortality probability was significantly influenced by COHb level (odds ratio = 1.159, 95% CI [1.056-1.273]). Patients receiving NBOT had a higher odds ratio for DNS risk than those receiving HBOT (odds ratio = 8.464, 95% [1.755-40.817], p = 0.008).

CONCLUSION

The study showed no differences in intubation, in-hospital mortality, and 1-year mortality rates between the HBOT and NBOT groups. However, significant differences in DNS suggest that treatment modalities have different effects on neurological outcomes. High COHb levels are associated with an increased risk of intubation, and mortality underscores the significance of monitoring COHb levels in clinical evaluations.

Analysis of factors associated with the development of delayed encephalopathy following acute carbon monoxide poisoning

In this study, we analyzed the factors influencing the development of delayed encephalopathy in patients with acute carbon monoxide poisoning (ACOP) (DEACMP) following conventional treatment such as hyperbaric oxygen therapy (HBOT). Between January 2012 and January 2022, we retrospectively analyzed 775 patients with ACOP, who were admitted to the Second Department of Rehabilitation Medicine and received HBOT in the Second Hospital of Hebei Medical University. These patients were divided into the non-DEACMP and DEACMP groups based on their follow-up; we then compared the general data, clinical characteristics, admission examination, and treatment between the two groups to identify risk factors for the development of DEACMP. The DEACMP group comprised of 168 cases, while the non-DEACMP group consisted of 607 cases. Univariate analysis showed that there were 20 possible prognostic factors in the non-DEACMP and DEACMP groups. The results of multivariable regression analyses suggested that the occurrence of DEACMP was significantly correlated with advanced age, the combination of multiple medical histories, the duration of CO exposure, the duration of coma, poisoning degree, the Interval between ACOP and the first HBOT, the total number of HBOTs, and the combination with rehabilitation treatment. DEACMP patients who are older, have more comorbidities, prolonged CO exposure, prolonged coma, severe intoxication, long intervals between ACOP and the first HBOT, fewer HBOT treatments, and who are not treated with a combination of rehabilitative therapies have a poor prognosis.

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.

Clinical and Echocardiographic Predictors for the Presence of Late Gadolinium Enhancement on Cardiac Magnetic Resonance Imaging in Patients with Carbon Monoxide Poisoning

Late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging (CMRI) reflects the burden of myocardial damage in carbon monoxide (CO) poisoning. This study aimed to identify the clinical and echocardiographic parameters that can predict myocardial LGE on CMRI in CO poisoning. This prospective observational study included patients who presented with acute CO poisoning and elevated troponin I and underwent echocardiography and CMRI to identify myocardial damage at a tertiary university hospital between August 2017 and May 2019 and August 2020 and July 2022. Based on the CMRI findings, participants were categorized into LGE and non-LGE groups. The median age of the 155 patients was 51.0 years, and 98 (63.2%) were males. Median times from emergency department arrival to either CMRI or echocardiography were 3.0 days each. The LGE group included 99 (63.9%) patients with LGE positivity on CMRIs. Time from rescue to hyperbaric oxygen therapy >4 h (odds ratio (OR): 3.31, 95% confidence interval (CI): 1.28-8.56, p = 0.01); serum lactate levels >2 mmol/L (OR: 2.62, 95% CI: 1.20-5.73, p = 0.02); and left ventricular global longitudinal strain >-16% (OR: 2.95, 95% CI: 1.35-6.47, p = 0.007) were significant predictors of LGE positivity. The area under the curve of these predictors was 0.711. Our prediction model, which combines the clinical parameters with left ventricular global longitudinal strain, may be helpful in the early detection of LGE positivity.

Association between number of hyperbaric oxygen therapy sessions and neurocognitive outcomes of acute carbon monoxide poisoning

Background

Hyperbaric oxygen therapy (HBO2) is recommended for symptomatic patients within 24 h of carbon monoxide (CO) poisoning. Currently, there is no consensus on the number of HBO2 sessions within 24 h after arrival at the hospital. Therefore, we evaluated differences in the therapeutic effects according to the number of HBO2 sessions in acute CO poisoning.

Methods

This cohort study included data collected from our CO poisoning registry and prospective cohorts between January 2006 and August 2021 in a single academic medical center in South Korea. Based on the number of HBO2 sessions performed within 24 h, we classified patients into one- and multiple- (two or three) session groups. We also compared mild (non-invasive mechanical ventilation) and severe (invasive mechanical ventilation) groups. CO-related neurocognitive outcomes were measured using the Global Deterioration Scale (GDS; stages: 1-7) combined with neurological impairment at 1 month after poisoning. We classified GDS stages as favorable (1-3 stages) and poor (4-7 stages) neurocognitive outcomes. Patients belonging to a favorable group based on GDS assessment, but with observable neurological impairment, were assigned to the poor outcome group. Propensity score matching (PSM) was performed to adjust for age, sex, and related variables to identify statistical differences between groups.

Results

We analyzed the data of 537 patients between ages 16 and 70 years treated with HBO2. After PSM, there was no significant difference in neurocognitive outcomes at 1 month among the two groups of patients (p = 0.869). Furthermore, there were no significant differences in neurocognitive outcomes between invasive mechanical ventilation and non-invasive mechanical ventilation patients in the three groups (p = 0.389 and p = 0.295).

Conclusion

There were no significant differences in the reduction of poor neurocognitive outcomes according to the number of HBO2 sessions implemented within 24 h of CO exposure.

Quantitative pupillary light reflex assessment for prognosis of carbon monoxide poisoning

Background

A non-reactive pupil in standard pupillary light reflex (sPLR) is regarded as a factor predicting neurological sequelae at 1-month after carbon monoxide (CO) poisoning. An automated pupillometer is used in the intensive care unit to quantitatively assess PLR. Quantitative PLR (qPLR) was superior to sPLR using penlight for prognosis of various neurological diseases. Therefore, this study aimed to analyze whether quantitative pupillary variables (neurological Pupil index [NPi] and qPLR) are superior to sPLR in predicting 1-month neurocognitive sequelae after acute CO poisoning.

Methods

We performed a prospective observational study of consecutive patients with acute CO poisoning admitted to an emergency department (ED) between August 2019 and December 2020 in a single academic medical center. sPLR and pupillometer examinations (qPLR and NPi) were performed by emergency physicians at the ED on hospital days 0-2. The lowest values among those recorded within 24 h and during the total measurement period were considered the 24-h and total lowest values, respectively. Global Deterioration Scale scores were measured at 1 month as an outcome and were dichotomized into favorable (1-4) or poor (5-7) outcomes.

Results

We analyzed the data of 104 adult patients with acute CO poisoning. qPLR was significantly higher in the favorable outcome group than in the poor outcome group 24-h and total lowest values (21.2% vs. 15.0%, p = 0.006 and 21.0% vs. 14.8%, p = 0.006). qPLR <18% had fair predictive power for poor neurocognitive outcomes [area under the curve (AUC), 0.70; 95% confidence interval (0.60-0.78)]. Among the patients with decreased mental status (Glasgow Coma Scale ≤12), the power of NPi and qPLR increased [AUC, 0.72 and AUC, 0.80]. NPi < 1 and qPLR <18% showed sensitivity (9.5% vs. 76.2%) and specificity (98.8% vs. 67.5%) for the prediction of poor outcomes. qPLR was significantly superior to sPLR in predicting poor neurocognitive outcomes at 1 month after CO poisoning (p = 0.007).

Conclusion

qPLR and NPi were superior to sPLR in terms of predicting poor neurocognitive outcomes. qPLR and NPi measured from hospital days 0-2 may be valuable in predicting neurocognitive outcome.

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.

Application of Mitochondrial and Oxidative Stress Biomarkers in the Evaluation of Neurocognitive Prognosis Following Acute Carbon Monoxide Poisoning

Mitochondrial and oxidative stress play critical roles in the pathogenic mechanisms of carbon monoxide (CO)-induced toxicity. This study was designed to evaluate whether the serum levels of specific stress biomarkers might reflect brain injury and act as prognostic markers for the development of neurocognitive sequelae following CO poisoning. We analyzed the data from 51 adult patients admitted with acute CO poisoning and measured the serum level expression of growth differentiation factor 15 (GDF15) and fibroblast growth factor 21 (FGF21), indicators of mitochondrial stress, and 8-Oxo-2′-deoxyguanosine (8-OHdG) and malondialdehyde (MDA), indicators of oxidative stress. Serum was collected upon arrival at the hospital, at 24 h post treatment, and within 7 days of HBO₂ therapy. Global Deterioration Scale scores were measured 1 month post incident and used to place the patients in either favorable or poor outcome groups. Initial serum GDF15 and 8-OHdG concentrations were significantly increased in the poor-outcome group and all four biomarkers decreased at 24 h post HBO₂ therapy, and were then maintained or further decreased at the 1-week mark. Notably, the degree of change in these biomarkers between baseline and 24 h post HBO₂ were significantly larger in the poor-outcome group, reflecting greater CO-associated stress, confirming that post-CO poisoning serum biomarker levels and their response to HBO₂ were proportional to the initial stress. We suggest that these biomarkers accurately reflect neuronal toxicity in response to CO poisoning, which is consistent with their activity in other pathologies.