Clinical chameleons: an emergency medicine focused review of carbon monoxide poisoning

Diagnostic challenge in a 2-year-old boy poisoned with carbon monoxide: A case report

Key Clinical Message

Carbon monoxide poisoning diagnosis is sometimes very difficult and should be considered in the differential diagnosis list of children's consciousness disorders even in summer.

Abstract

Carbon monoxide poisoning is very dangerous, and sometimes, it is difficult to diagnose. Especially, this poisoning may have non-specific manifestations in children and can be confused with other diseases. Here we present a 2-year-old child who suffered a disturbance of consciousness during the summer season. He and his family were travelers who had come to Mashhad from Kerman and were staying in a hotel room, after various investigations. It has been found that he was poisoned with carbon monoxide gas due to the leakage of carbon monoxide gas from the chimney pipe of the engine room related to the hotel's water heating into the room. After receiving oxygen and supportive treatments, he recovered and was discharged with good health. Poisoning with carbon monoxide gas is very dangerous, and the awareness of health and medical personnel in this field is essential.

Evaluation of a Portable Blood Gas Analyzer for Prehospital Triage in Carbon Monoxide Poisoning: Instrument Validation Study

BACKGROUND

Carbon monoxide (CO) poisoning is an important cause of morbidity and mortality worldwide. Symptoms are mostly aspecific, making it hard to identify, and its diagnosis is usually made through blood gas analysis. However, the bulkiness of gas analyzers prevents them from being used at the scene of the incident, thereby leading to the unnecessary transport and admission of many patients. While multiple-wavelength pulse oximeters have been developed to discriminate carboxyhemoglobin (COHb) from oxyhemoglobin, their reliability is debatable, particularly in the hostile prehospital environment.

OBJECTIVE

The main objective of this pilot study was to assess whether the Avoximeter 4000, a transportable blood gas analyzer, could be considered for prehospital triage.

METHODS

This was a monocentric, prospective, pilot evaluation study. Blood samples were analyzed sequentially with 2 devices: the Avoximeter 4000 (experimental), which performs direct measurements on blood samples of about 50 µL by analyzing light absorption at 5 different wavelengths; and the ABL827 FLEX (control), which measures COHb levels through an optical system composed of a 128-wavelength spectrophotometer. The blood samples belonged to 2 different cohorts: the first (clinical cohort) was obtained in an emergency department and consisted of 68 samples drawn from patients admitted for reasons other than CO poisoning. These samples were used to determine whether the Avoximeter 4000 could properly exclude the diagnosis. The second (forensic) cohort was derived from the regional forensic center, which provided 12 samples from documented CO poisoning.

RESULTS

The mean COHb level in the clinical cohort was 1.7% (SD 1.8%; median 1.2%, IQR 0.7%-1.9%) with the ABL827 FLEX versus 3.5% (SD 2.3%; median 3.1%, IQR 2.2%-4.1%) with the Avoximeter 4000. Therefore, the Avoximeter 4000 overestimated COHb levels by a mean difference of 1.8% (95% CI 1.5%-2.1%). The consistency of COHb readings by the Avoximeter 4000 was excellent, with an intraclass correlation coefficient of 0.97 (95% CI 0.93-0.99) when the same blood sample was analyzed repeatedly. Using prespecified cutoffs (5% in nonsmokers and 10% in smokers), 3 patients (4%) had high COHb levels according to the Avoximeter 4000, while their values were within the normal range according to the ABL827 FLEX. Therefore, the specificity of the Avoximeter 4000 in this cohort was 95.6% (95% CI 87%-98.6%), and the overtriage rate would have been 4.4% (95% CI 1.4%-13%). Regarding the forensic samples, 10 of 12 (83%) samples were positive with both devices, while the 2 remaining samples were negative with both devices.

CONCLUSIONS

The limited difference in COHb level measurements between the Avoximeter 4000 and the control device, which erred on the side of safety, and the relatively low overtriage rate warrant further exploration of this device as a prehospital triage tool.

Hickam's Suicide: A Case of Carbon Monoxide Toxicity, Compartment Syndrome, Rhabdomyolysis, and Renal Failure From Attempted Dual Suicide

Suicide pacts among elderly couples afflicted by a terminal disease process present a significant challenge to emergency clinicians. If one member of the pair aborts their attempt, the surviving member of a dual suicide attempt can present a complex case with numerous clinical issues reflected by Hickam's dictum rather than by Occam's razor. Thus, emergency clinicians must keenly search for a multitude of concomitant but compounding conditions, potentially projected onto pre-existing comorbidities in an elderly population. The authors present a case of a suicide pact in which one member of the couple completed the attempt while the surviving member experienced carbon monoxide toxicity, compartment syndrome, rhabdomyolysis, and renal failure following her aborted suicide attempt.

Diagnostic value of systemic immune-inflammation index and red cell distribution width-lymphocyte ratio in predicting troponin elevation in carbon monoxide poisoning

Purpose: The aim of our study was to assess the significant value of the systemic inflammatory index (SII) and red cell distribution width/lymphocyte ratio (RLR) in patients with carbon monoxide poisoning (COP). Materials and Methods: Based on a retrospective cross-sectional study design, this study was conducted among patients 18 years and older who presented to the hospital's emergency department with COP. The patients were separated into troponin positive and negative groups as an outcome of serial troponin measurements. Receiver operating characteristic (ROC) analysis was used to determine the cut-off value of neutrophil/lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), RLR, and SII to predict troponin positivity. Results: This study included 195 patients with CO exposure, 50 of whom had positive troponin tests. It was discovered that the diagnostic power of NLR, RLR, MLR, and SII was acceptable for identifying troponin positivity (AUC: 0.71-0.77). According to ROC curve comparisons, there was no diagnostic difference between these inflammatory biomarkers. Increased NLR, RLR, MLR, and SII were found to be independent predictors of troponin positivity after CO exposure (Odds ratio respectively: 8.65, 4.31, 7.24, 6.31). Conclusion: SII and RLR, which are simple, inexpensive, and easily accessible parameters, are valuable in predicting troponin positivity in COP cases.

Clinical and Epidemiological Characteristics of Acute Poisoning in Children in Southwestern China: A Review of 1755 Cases from 2014 to 2020

Purpose

Acute poisoning is a major cause of disability and death in children, but there is a lack of large-scale and multicenter epidemiological data on acute poisoning in children.

Patients and Methods

The current study was a retrospective analysis of clinical data from 1755 children aged 0 to 14 years who were hospitalized between 01 January 2014 and 31 December 2020 in southwestern China.

Results

Acute poisoning was common in childhood, particularly in early childhood (607; 34.6%) and preschool (655; 37.3%), and most cases occurred in rural areas (1191; 67.9%). It was more common in boys (934; 53.2%) than in girls (821; 46.8%). In urban areas, poisoning was mainly caused by drugs (266; 47.2%), chemical agents (59; 10.5%), and alcohol (54; 9.6%). In rural areas, it was mainly caused by pesticides (620; 52.1%) and medications (213; 17.9%), the route of poisoning was usually the digestive tract (1671; 95.2%), in most cases the poisoning was accidental (1618; 92.3%), and pesticides (659; 37.5%) and medications (479; 27.3%) predominated. After timely treatment, the majority of patients had no substantial organ damage, sequelae, or disabilities, and mortality was low (17; 1.0%).

Conclusion

Acute poisoning is a frequent accident in childhood, mainly in infants and preschool children, mostly in rural areas, and poisoning mostly occurs via the digestive tract. Family and community education should be conducted to prevent poisoning.

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Extracorporeal Hyperoxygenation Therapy (EHT) for Carbon Monoxide Poisoning: In-Vitro Proof of Principle

Carbon monoxide (CO) poisoning is the leading cause of poisoning-related deaths globally. The currently available therapy options are normobaric oxygen (NBO) and hyperbaric oxygen (HBO). While NBO lacks in efficacy, HBO is not available in all areas and countries. We present a novel method, extracorporeal hyperoxygenation therapy (EHT), for the treatment of CO poisoning that eliminates the CO by treating blood extracorporeally at elevated oxygen partial pressure. In this study, we proof the principle of the method in vitro using procine blood: Firstly, we investigated the difference in the CO elimination of a hollow fibre membrane oxygenator and a specifically designed batch oxygenator based on the bubble oxygenator principle at elevated pressures (1, 3 bar). Secondly, the batch oxygenator was redesigned and tested for a broader range of pressures (1, 3, 5, 7 bar) and temperatures (23, 30, 37 °C). So far, the shortest measured carboxyhemoglobin half-life in the blood was 21.32 min. In conclusion, EHT has the potential to provide an easily available and effective method for the treatment of CO poisoning.

Risk factors for venous thromboembolism after carbon monoxide poisoning: A nationwide population-based study

Introduction:

The risk of venous thromboembolism increases after acute carbon monoxide poisoning. However, studies on the characteristics of patients who develop venous thromboembolism after carbon monoxide poisoning are rare. The aim of this study was to identify the risk factors for venous thromboembolism within 3 months after carbon monoxide poisoning.

Methods:

This is a population-based study that employed nationwide claims data from South Korea. Among the carbon monoxide poisoning patients (⩾18 years), the characteristics of the groups with and without venous thromboembolism (pulmonary embolism or deep vein thrombosis) were identified. All the significant variables in the univariable analysis were included in the multivariable logistic regression to determine the risk factors for venous thromboembolism occurrence.

Results:

Among the 24,232 carbon monoxide poisoning patients, 130 subjects developed venous thromboembolism within 90 days of their carbon monoxide poisoning diagnosis. The significant risk factors for venous thromboembolism in the multivariable analysis were age (adjusted odds ratio (aOR) = 1.01; 95% confidence interval (CI) = 1.003–1.03), intensive care unit admission (aOR = 3.80; 95% CI = 2.34–6.12), length of stay (aOR = 1.02; 95% CI = 1.0001–1.04), congestive heart failure (aOR = 2.17; 95% CI = 1.36–3.42), and cancer (aOR = 1.94; 95% CI = 1.10–3.22). The adjusted odds ratios for intensive care unit admission for patients with pulmonary embolism and deep vein thrombosis were 3.05 (95% CI = 1.61–5.61) and 5.60 (95% CI = 2.89–10.90), respectively.

Conclusion:

Patients with older age, intensive care unit admission, a longer length of stay, congestive heart failure, or cancer are at greater risk of developing venous thromboembolism after carbon monoxide poisoning. In particular, intensive care unit admission was the strongest risk factor for venous thromboembolism, pulmonary embolism, and deep vein thrombosis. Monitoring and administering prophylactic treatments to prevent venous thromboembolism would be helpful in high-risk in carbon monoxide poisoning patients.

Urgent hyperbaric oxygen therapy for suicidal carbon monoxide poisoning: from a preliminary survey to a proposal for an integrated somatic-psychiatric protocol

A considerable number of patients who made a carbon monoxide (CO) suicidal attempt are treated with urgent hyperbaric oxygen therapy (HBOT). For these patients at potential persistent risk of suicide, the hyperbaric chamber is a dangerous environment and their management a complex challenge for the Emergency Department (ED) and Hyperbaric Medicine Unit (UMH) teams. We aimed to (1) identify cases of intentional CO poisoning treated with urgent HBOT in the UMH of the University Hospitals of Geneva (HUG) during 2011-2018 and (2) test a proposed operational and integrated somatic-psychiatric protocol based on acquired experience. A total of 311 patients with CO poisoning were treated using urgent HBOT, for which poisoning was assumed suicidal in 40 patients (12.9%). This percentage appears greater than in other European countries. Both the excess of cases of intentional CO poisonings and difficulties encountered in their management resulted in the implementation of an operational and integrated somatic-psychiatric protocol addressing the entire patient's clinical trajectory, from the admission at ED-HUG to the treatment at the UMH-HUG. The established institutional protocol includes (1) clinical evaluation, (2) suicide risk assessment, and (3) safety measures. This is the first report-at our best knowledge-of a protocol detailing a practical procedure algorithm and focusing on multidisciplinary and mutual collaboration between the medical-nursing teams at the ED, psychiatric ED, and UMH. Improvements in patient's safety and care team's sense of security were observed. In conclusion, the opportunity to refer to a standardized protocol was beneficial in that it offers both reduced risks for suicidal patients and reduced stress for care teams operating in very acute and complex situations. Further studies are needed.

Use of Hemoglobin for Delivering Exogenous Carbon Monoxide in Medicinal Applications

Carbon Monoxide (CO), at low concentrations, can have a variety of positive effects on the body including anti-apoptosis, anti-inflammatory, anti-oxidative and anti-proliferative effects. Although CO has great potential for use as a potent medical bioactive gas, for it to exist in the body in stable form, it must be associated with a carrier. Hemoglobin (Hb) represents a promising material for use as a CO carrier because most of the total CO in the body is stored associated with Hb in red blood cells (RBC). Attempts have been made to develop an Hb-based CO carrying system using RBC and Hb-based artificial oxygen carriers. Some of these have been reported to be safe and to have therapeutic value as a CO donor in preclinical and clinical studies. In the present review, we overview the potential of RBC and Hb-based artificial oxygen carriers as CO carriers based on the currently available literature evidence for their use in pharmaceutical therapy against intractable disorders.

DNA damage and antioxidant properties of CORM-2 in normal and cancer cells

In this study, we compared the effect of tricarbonyldichlororuthenium (II) dimer (CORM-2) and its CO-depleted molecule (iCORM-2) on human peripheral blood mononuclear cells (PBMCs) and human promyelocytic leukemia HL-60 cells. We determined cell viability, DNA damage and DNA repair kinetics. We also studied the effect of both compounds on DNA oxidative damage, free radical level and HO-1 gene expression. We showed that at low concentrations both CORM-2 and iCORM-2 stimulate PBMCs viability. After 24-h incubation, CORM-2 and iCORM-2, at the concentration of 100 µM, reduce the viability of both PBMCs and HL-60 cells. We also demonstrated that CORM-2 and iCORM-2, in the 0.01–100 µM concentration range, cause DNA damage such as strand breaks and alkaline labile sites. DNA damage was repaired efficiently only in HL-60 cells. CORM-2 significantly reduces oxidative stress induced by 1 mM H₂O₂ in normal and cancer cells. On the contrary, iCORM-2 in HL-60 cells increases the level of free radicals in the presence of 1 and 5 mM H₂O₂. We also revealed that both CORM-2 and iCORM-2 induce HO-1 gene expression. However, CORM-2 induces this gene to a greater extent than iCORM-2, especially in HL-60 cells at 100 µM. Finally, we showed that CORM-2 and iCORM-2 reduce H₂O₂-induced DNA oxidative damage. Furthermore, CORM-2 proved to be a compound with stronger antioxidant properties than iCORM-2. Our results suggest that both active CORM-2 and inactive iCORM-2 exert biological effects such as cyto- and genotoxicity, antioxidant properties and the ability to induce the HO-1 gene. The released CO as well as iCORM-2 can be responsible for these effects.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Risk of Venous Thromboembolism After Carbon Monoxide Poisoning: A Nationwide Population-Based Study

STUDY OBJECTIVE

Few studies have investigated the association between carbon monoxide (CO) poisoning and risk of venous thromboembolism. We aim to identify the risk of pulmonary embolism and deep venous thrombosis after CO poisoning.

METHODS

We conducted a nationwide cohort-crossover study using administrative claims data in Korea. We compared the risk of venous thromboembolism (pulmonary embolism or deep venous thrombosis) in the cohort period after CO poisoning to that of the same period 1 year later (crossover period), using conditional logistic regression analysis.

RESULTS

We included 22,699 patients with a diagnosis of CO poisoning during the study period between 2004 and 2015. The risk of venous thromboembolism was significantly elevated during days 0 to 90 after CO poisoning (odds ratio 3.96; 95% confidence interval 2.50 to 6.25). However, this risk was not significantly elevated during subsequent postexposure periods through 360 days. During days 0 to 30 after CO poisoning, the risks of pulmonary embolism (odds ratio 22.00; 95% confidence interval 5.33 to 90.75) and deep venous thrombosis (odds ratio 10.33; 95% confidence interval 3.16 to 33.80) were significantly elevated.

CONCLUSION

We found that the risk of venous thromboembolism persisted for up to 90 days after CO poisoning. The risk was increased 22-fold for pulmonary embolism and 10-fold for deep venous thrombosis, especially in the first month after CO poisoning. Patients should be monitored for venous thromboembolism risk after CO poisoning.

Does alcohol play the role of confounder or neuroprotective agent in acute carbon monoxide poisoning?

Objectives: This study investigated whether alcohol influences the predictive value of initial blood lactate concentration and Glasgow Coma Scale (GCS) score at presentation for the severity of acute carbon monoxide (CO) poisoning and neurologic outcome in patients with acute CO poisoning. Additionally, whether alcohol has a neuroprotective effect after acute CO poisoning was evaluated.Methods: This retrospective study included 158 patients who presented with acute CO poisoning between January 2017 and July 2018 and had an available blood alcohol content (BAC) at presentation. The baseline characteristics, clinical course during hospitalization and neurologic status at 30 days after acute CO poisoning were collected and compared according to BAC. To account for possible confounding or neuroprotective effects of alcohol, BAC was introduced as a continuous variable and a stratified categorical variable in the analysis.Results: The mean and maximum BAC at presentation were 56.8 mg/dl and 408 mg/dl, respectively, in 158 patients presented at a mean of 1.0 hour after acute CO poisoning. Lactate, adjusted for previously suggested predictors, was not associated with acute CO poisoning severity; however, after additional adjustment with BAC variables, lactate was associated with CO poisoning severity. Initial GCS score was associated with CO poisoning severity during hospitalization and neurologic outcome at 30 days after acute CO poisoning, regardless of BAC adjustment. BAC variables were negatively associated with CO poisoning severity but not neurologic outcome at 30 days.Discussion and conclusion: The severity of CO poisoning should never be predicted based on serum lactate alone without adjusting for BAC. However, the initial GCS score can be used as a predictor of CO poisoning severity and the neurologic outcome at 30 days after acute CO poisoning, regardless of alcohol consumption history. Alcohol does not have a neuroprotective effect on acute CO poisoning. Further study is needed to validate these results.

Availability of Bedside and Laboratory Testing for Carbon Monoxide Poisoning in the Upper Midwestern United States

INTRODUCTION

The objective of this study was to assess the ability to test patients for carbon monoxide (CO) exposure in all hospitals in three United States (U.S.) Midwestern states.

METHODS

We surveyed hospitals in three states. Telephone queries assessed processes for measuring carboxyhemoglobin, including capacity for real-time vs send-out testing. Facilities were separated based on their location's population size for further analysis. Descriptive statistics are reported.

RESULTS

Of the 250 hospitals queried, we ultimately excluded 25. Nearly all (220, 97.8%) reported a process in place to test for CO exposure. Over 40% (n=92) lacked real-time testing. Testing ability was positively associated with increasing population size quartile (range 32.6% - 100%). Hospitals in the lowest-quartile population centers were more likely to report that they were unable to test in real time than those in the largest-quartile population centers (67.4% vs 0%).

CONCLUSION

In a large geographic region encompassing three states, hospital-based and real-time capacity to test for CO exposure is not universal. Hospitals in smaller population areas are more likely to lack real-time testing or any testing at all. This may have significant public health, triage, and referral implications for patients.

Longitudinal White Matter Changes following Carbon Monoxide Poisoning: A 9-Month Follow-Up Voxelwise Diffusional Kurtosis Imaging Study

BACKGROUND AND PURPOSE

Patients with carbon monoxide (CO) intoxication exhibit progressive WM changes that are not well-understood. The purpose of this study was to detect longitudinal WM changes using voxelwise diffusional kurtosis imaging in patients with CO intoxication from the acute-to-chronic stage after CO intoxication.

MATERIALS AND METHODS

Twenty-four patients with CO intoxication and 21 age- and sex-matched healthy controls were enrolled in this study. Diffusional kurtosis imaging was performed on all subjects and was conducted repeatedly in patients at 1 week and 1, 3, and 9 months after CO intoxication. Voxelwise diffusional kurtosis imaging analysis was performed to detect global WM changes in the patients with and without WM lesions. Receiver operating characteristic analysis was performed to compare the performance of diffusional indices in differentiating patients with delayed neuropsychiatric sequelae from patients without them.

RESULTS

In voxelwise analysis, progressive WM changes were detected in patients with WM lesions. In the acute phase, WM injuries were found mainly in the dopaminergic pathways at 1 week, whereas in the chronic stage, WM injuries extended toward subcortical areas from 1 to 9 months. However, no significant WM change was noted in patients without WM lesions during the 9 months after CO intoxication. Moreover, receiver operating characteristic analysis demonstrated that axial kurtosis and mean kurtosis values had better performance than other diffusional indices in differentiating patients with delayed neuropsychiatric sequelae from patients without them at 1 week after CO intoxication.

CONCLUSIONS

Voxelwise diffusional kurtosis imaging analysis was helpful to longitudinally investigate WM changes and predict the prognosis of patients after CO intoxication.

A New Promising Treatment Strategy for Carbon Monoxide Poisoning: High Flow Nasal Cannula Oxygen Therapy

Background

High-flow nasal cannula (HFNC) is an alternative to conventional normobaric oxygen therapy (NBO) for hypoxemic patients. Since nothing is known about its effect on carbon monoxide (CO) poisoning, we hypothesized that HFNC might be a useful device in the treatment of CO poisoning victims.

Material/Methods

We retrospectively reviewed the medical records of patients who were admitted consecutively to the emergency department with CO intoxication. Patients were divided into 2 groups: patients treated with HFNC and patients treated with conventional face mask (CFM). Demographic data, pretreatment, and control (after 1 hour) arterial blood gas analyses values of the patients were evaluated.

Results

Sixty-eight patients (mean age 35.8±18.7 years) were included in this study. NBO was given via HFNC to 38 patients (55.9%), and via CFM to 30 patients (44.1%). The demographic characteristics and pretreatment values of carboxy-hemoglobin (COHb) were similar in the 2 groups. The mean COHb value of the HFNC group at the first hour was found significantly lower than the CFM group: 9.5±4.7 and 12.0±5.1, respectively (P=0.041). Improvement of COHb level was significantly higher in the HFNC group compared to the CFM group: 12.5±4.5 versus 6.7±3.7, respectively (P=0.001).

Conclusions

HFNC was superior than CFM in alleviating COHb levels in the victims of CO poisoning. We believe that using HFNC will increase patient comfort by shortening the duration of treatment in emergency department settings, especially in patients who have mild clinical findings of CO poisoning.

The impact of hyperthermia after acute carbon monoxide poisoning on neurological sequelae

This study investigated whether hyperthermia within the first 24 h after presentation was associated with long-term neurological outcomes after acute carbon monoxide (CO) poisoning. This retrospective study included 200 patients with acute severe CO poisoning. Hyperthermia (≥ 37.5°C) developed during the first 24 h after presentation in 55 (27.5%) patients, and poor long-term neurological sequelae assessed at 23 months after acute CO poisoning developed in 19.5% of the patients. The incidence of poor long-term neurological outcomes was significantly higher in the hyperthermia group than in the normothermia group. Patients with poor long-term neurological outcomes had higher maximum temperatures than patients with good outcomes. No significant difference was found in the time of hyperthermia onset within the first day according to the neurological outcomes. Hyperthermia (adjusted odds ratio (aOR) 5.009 (95% confidence interval (CI) 1.556-16.126)) and maximum temperature (aOR 2.581 (95% CI 1.098-6.063)) within the first 24 h after presentation to the emergency department were independently associated with poor long-term neurological outcomes. Body temperature measurements, which are easily and noninvasively recorded at the bedside in any facility, help to predict the risk for poor long-term neurological outcomes. This study carefully emphasizes fastidious control of pyrexia, particularly during the early period after acute CO poisoning.