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

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.

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.

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.

Binding of Carbon Monoxide to Hemoglobin in an Oxygen Environment: Force Field Development for Molecular Dynamics

Carbon monoxide (CO) is a byproduct of the incomplete combustion of carbon-based fuels, such as wood, coal, gasoline, or natural gas. As incomplete combustion in a fire accident or in an engine, massively produced CO leads to a serious life threat because CO competes with oxygen (O2) binding to hemoglobin and makes people suffer from hypoxia. Although there is hyperbaric O2 therapy for patients with CO poisoning, the nanoscale mechanism of CO dissociation in the O2-rich environment is not completely understood. In this study, we construct the classical force field parameters compatible with the CHARMM for simulating the coordination interactions between hemoglobin, CO, and O2, and use the force field to reveal the impact of O2 on the binding strength between hemoglobin and CO. Density functional theory and Car-Parrinello molecular dynamics simulations are used to obtain the bond energy and equilibrium geometry, and we used machine learning enabled via a feedforward neural network model to obtain the classical force field parameters. We used steered molecular dynamics simulations with a force field to characterize the mechanical strength of the hemoglobin-CO bond before rupture under different simulated O2-rich environments. The results show that as O2 approaches the Fe2+ of heme at a distance smaller than ∼2.8 Å, the coordination bond between CO and Fe2+ is reduced to 50% bond strength in terms of the peak force observed in the rupture process. This weakening effect is also shown by the free energy landscape measured by our metadynamics simulation. Our work suggests that the O2-rich environment around the hemoglobin-CO bond effectively weakens the bonding, so that designing of O2 delivery vector to the site is helpful for alleviating CO binding, which may shed light on de novo drug design for CO poisoning.

Delayed neuropsychiatric sequelae with improvement of decreased cerebral bold flow by single-photon emission computed tomography during hyperbaric oxygen therapy: A case report with a 10-year follow-up

Background

Delayed neuropsychiatric sequelae (DNS) occurs in 10%-30% of acute carbon monoxide poisoning cases. Patients with this condition present higher brain dysfunction. Hyperbaric oxygen (HBO) therapy was reportedly an effective treatment for DNS in the acute phase. Favorable predictive factors affecting the prognosis of patients with DNS after HBO therapy include younger age and longer interictal periods. However, the relationship between these factors and neuroimaging findings remains unclear.

Case Presentation

The patient was a 59-year-old man with DNS, who developed major depressive disorder and attempted suicide with charcoal briquettes. He was diagnosed with carbon monoxide poisoning and underwent acute HBO therapy. After a 1-month lucid period, the patient developed intermittent carbon monoxide poisoning with cognitive dysfunction, following which HBO therapy was re-initiated. Following treatment, the patient returned to work for 10 years. Frontal lobe hypoperfusion, measured by single-photon emission computed tomography and cognitive impairment, improved with HBO therapy. However, magnetic resonance imaging revealed brain volume atrophy over time.

Conclusion

This study reported a case of DNS that completely resolved within a 10-year follow-up period. Cerebral blood flow reduction, mainly in the frontal lobe, improved along with cognitive recovery during HBO therapy. Despite gradually progressive brain atrophy over the past decade, no noted deficits in cerebral blood flow were observed in the frontal lobes. These findings suggest that improvement in cerebral blood flow during HBO therapy and its retention may be factors associated with a favorable prognosis in patients with DNS.

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.

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.

[Carbon monoxide intoxication-New aspects and current guideline-based recommendations]

Carbon monoxide poisoning is a common and potentially life-threatening intoxication, showing an interindividual variety of unspecific symptoms as well as late neurological and other sequelae. Two new German guidelines (S2k guidelines diagnosis and treatment of carbon monoxide poisoning as well as S3 guidelines oxygen therapy in the acute care of adult patients) focus on current evidence-based information on diagnostics as well as therapeutic options with considerable uncertainty remaining. This review summarizes current information and presents a flow scheme for daily practical use.

A New Phased-Array Magnetic Resonance Imaging Receive-Only Coil for HBO2 Studies

The paper describes a new magnetic resonance imaging (MRI) phased-array receive-only (Rx) coil for studying decompression sickness and disorders of hyperbaricity, including nitrogen narcosis. Functional magnetic resonance imaging (fMRI) is noninvasive, is considered safe, and may allow studying the brain under hyperbaric conditions. All of the risks associated with simultaneous MRI and HBO2 therapy are described in detail, along with all of the mitigation strategies and regulatory testing. One of the most significant risks for this type of study is a fire in the hyperbaric chamber caused by the sparking of the MRI coils as a result of high-voltage RF arcs. RF pulses at 128 MHz elicit signals from human tissues, and RF sparking occurs commonly and is considered safe in normobaric conditions. We describe how we built a coil for HBO2-MRI studies by modifying an eight-channel phased-array MRI coil with all of the mitigation strategies discussed. The coil was fabricated and tested with a unique testing platform that simulated the worst-case RF field of a three-Tesla MRI in a Hyperlite hyperbaric chamber at 3 atm pressure. The coil was also tested in normobaric conditions for image quality in a 3 T scanner in volunteers and SNR measurement in phantoms. Further studies are necessary to characterize the coil safety in HBO2/MRI.

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.

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.