Elevated methemoglobin levels in patients treated with high-dose hydroxocobalamin.

OBJECTIVE: The aim of this study was to assess the impact of hydroxocobalamin (OHCbl) infusion on arterial blood gas and oximetry values in patients with vasoplegic syndrome. METHODS: Blood samples collected from 95 patients receiving OHCbl infusion were assayed using the ABL90 FLEX Plus blood gas analyzer for the concentration of methemoglobin (MetHb), total hemoglobin (tHb), carboxyhemoglobin (COHb), arterial oxygen saturation (SaO2), arterial oxygen partial pressure (PaO2), and arterial carbon dioxide partial pressure (PaCO2). Interference of OHCbl on these variables was evaluated using the measured difference between the preinfusion and postinfusion samples. RESULTS: Blood MetHb (%) measured after the infusion of OHCbl (5g) were significantly higher than the baseline levels, with a median of 4.8 (IQR, 3.0-6.5) versus 1.0 (IQR, 1.0-1.2) (P < .001). Blood COHb (%) increased from a median of 1.3 (IQR, 1.0-1.8) to 1.7 (IQR, 1.3-2.2) (P < .001) following the OHCbl infusion. No differences were seen in median levels of tHb, PaO2, PaCO2, and SaO2 between pre- and post-OHCbl treatment. CONCLUSION: The presence of OHCbl in blood clearly interfered with the oximetry measurements of the hemoglobin component fractions by falsely increasing the levels of MetHb and COHb. Blood levels of MetHb and COHb cannot be reliably determined by the co-oximetry when OHCbl is known or suspected.

Extracorporeal membrane oxygenators with light-diffusing fibers for treatment of carbon monoxide poisoning: Experiments, mathematical modeling, and performance assessment with unit cells.

BACKGROUND AND OBJECTIVES: Approximately 50,000 emergency department visits per year due to carbon monoxide (CO) poisoning occur in the United States alone. Tissue hypoxia can occur at very low CO concentration exposures because CO binds with a 250-fold higher affinity than oxygen to hemoglobin. The most effective therapy is 100% hyperbaric oxygen (HBO) respiration. However, there are only a limited number of cases with ready accessibility to the specialized HBO chambers. In previous studies, we developed an extracorporeal veno-venous membrane oxygenator that facilitates exposure of blood to an external visible light source to photo-dissociate carboxyhemoglobin (COHb) and significantly increase CO removal from CO-poisoned blood (photo-extracorporeal veno-venous membrane oxygenator [p-ECMO]). One objective of this study was to describe in vitro experiments with different laser wavelength sources to compare CO elimination rates in a small unit-cell ECMO device integrated with a light-diffusing optical fiber. A second objective was to develop a mathematical model that predicts CO elimination rates in the unit-cell p-ECMO  device design upon which larger devices can be based. STUDY DESIGN/MATERIAL AND METHODS: Two small unit-cell p-ECMO devices consisted of a plastic capillary with a length and inside diameter of 10 cm and 1.15 mm, respectively. Either five (4-1 device) or seven (6-1 device) gas exchange tubes were placed in the plastic capillary and a light-diffusing fiber was inserted into one of the gas exchange tubes. Light from lasers emitting either 635 nm or 465 nm wavelengths was coupled into the light-diffusing fiber as oxygen flowed through the gas exchange membranes. To assess the ability of the device to remove CO from blood in vitro, the percent COHb reduction in a single pass through the device was assessed with and without light. The Navier Stokes equations, Carreau-Yesuda model, Boltzman equation for light distribution, and hemoglobin kinetic rate equations, including photo-dissociation, were combined in a mathematical model to predict COHb elimination in the experiments. RESULTS: For the unit-cell devices, the COHb removal rate increases with increased 635 nm laser power, increased blood time in the device, and greater gas exchange membrane surface-to-blood volume ratio. The 6-1 device COHb half-life versus that of the 4-1 device with 4 W at 635 nm light was 1.5 min versus 4.25 min, respectively. At 1 W laser power, 635 nm and 465 nm exhibited similar CO removal rates. The COHb half-life times of the 6-1 device were 1.25, 2.67, and 8.5 min at 635 nm (4 W), 465 nm (1 W), and 100% oxygen only, respectively. The mathematical model predicted the experimental results. An analysis of the in vivo COHb half-life of oxygen respiration therapy versus an adjunct therapy with a p-ECMO device and oxygen respiration shows a reduction from 90 min to as low as 10 min, depending on the device design. CONCLUSION: In this study, we experimentally studied and developed a mathematical model of a small unit-cell ECMO device integrated with a light-diffusing fiber illuminated with laser light. The unit-cell device forms the basis for a larger device and, in an adjunct therapy with oxygen respiration, has the potential to remove COHb at much higher rates than oxygen therapy alone. The mathematical model can be used to optimize the design in practical implementations to quickly and efficiently remove CO from CO-poisoned blood.

Clinical and Laboratory Characteristics Predicting the Severity of Carbon Monoxide Poisoning in Children: A Single-Center Retrospective Study.

OBJECTIVES: Carbon monoxide poisoning (COP) is extremely common throughout the world. The purpose of this study was to assess the demographic, clinical, and laboratory characteristics predicting the severity COP in children. METHODS: The study included 380 children diagnosed with COP between January 2017 and January 2021 and 380 healthy controls. Carbon monoxide poisoning was diagnosed based on the medical history and a carboxyhemoglobin (COHb) level of more than 5%. The patients were classified as mild (COHb 10%), moderate (COHb 10%-25%), or severely (COHb > 25%) poisoned. RESULTS: The mean age of the severe group was 8.60 ± 6.30, for the moderate group was 9.50 ± 5.81, for the mild group was 8.79 ± 5.94, and for the control group was 8.95 ± 5.98. The most common place of exposure was at home and all cases were affected accidentally. The coal stove was the most common source of exposure, followed by natural gas. The most common symptoms were nausea/vomiting, vertigo, and headache. Neurologic symptoms such as syncope, confusion, dyspnea, and seizures were more common in the severe group. A total of 91.3% of the children had hyperbaric oxygen therapy, 3.8% were intubated, and 3.8% were transferred to intensive care in the severe group, whereas no death or sequela was observed. Mean platelet volume and red cell distribution width had the highest area under the curve in the receiver operating characteristic analysis (0.659; 0.379). A positive and low statistically significant relationship was found between COHb levels and troponin and lactate levels in the severe group ( P < 0.05). CONCLUSIONS: Carbon monoxide poisoning progressed more severely in children presented with neurological symptoms and have elevated red cell distribution width and mean platelet volume. Even in severe COP cases, satisfactory results have been obtained with early and appropriate treatment.

Non-invasive monitoring of carboxyhemoglobin during hyperbaric oxygen therapy.

Introduction: This study aimed to assess the capability of a pulse CO-oximeter to continuously monitor carboxyhemoglobin (COHb) during hyperbaric oxygen (HBO2) therapy. We estimated limits of agreement (LOA) between blood gas analysis and pulse CO-oximeter for COHb during HBO2 therapy in patients suffering from acute CO poisoning. Furthermore, we did a medicotechnical evaluation of the pulse CO-oximeter in hyperbaric conditions. Methods: We conducted a prospective, non-clinical, observational study in which we included n=10 patients with acute CO poisoning referred for HBO2 therapy. We did five repeated measurements of COHb for each patient during the HBO2 therapy. Bland-Altman analysis for multiple observations per individual was used to assess the agreement. The a priori LOA was ±6% for COHb. For the medicotechnical evaluation continuous measurements were obtained throughout each complete HBO2 therapy. The measurements were visually inspected and evaluated. Results: The Bland-Altman analysis showed that the pulse CO-oximeter overestimated COHb by 2.9 % [±1.0%] and the LOA was ±7.3% [±1.8%]. The continuous measurements by pulse CO-oximetry showed fluctuating levels of COHb and summarized saturations reached levels above 100%. Measurements were not affected by changes in pressure. Conclusion: To our knowledge, this study is the first to assess LOA and demonstrate use of a non-invasive method to measure COHb during HBO2 therapy. The pulse CO-oximeter performed within the manufactures reported LOA (±6%) despite hyperbaric conditions and was unaffected by changes in pressure. However, summarized saturations reached levels above 100%.

Predictors of Severe Clinical Course in Children With Carbon Monoxide Poisoning.

OBJECTIVE: Carbon monoxide (CO) is a gas, which is produced by incomplete combustion of hydrocarbon-containing substances, and causes significant tissue and organ damage in the common event of CO poisoning. This study aims to evaluate the demographic, clinical, and laboratory characteristics of patients diagnosed with CO poisoning in the emergency department and to determine the factors associated with severe course in the acute phase of poisoning. METHODS: A total of 331 patients diagnosed with CO poisoning in Hacettepe University Children's Hospital, Pediatric Emergency Unit, between January 2004 and March 2014 were included in the study. Their demographic characteristics, presenting complaints, physical examination findings, Glasgow Coma Scale scores, carboxyhemoglobin, leukocyte, hemoglobin, troponin T, pH and lactate levels, type of treatment (normobaric or hyperbaric oxygen), intensive care unit admissions, and outcome of poisoning were investigated. RESULTS: Ninety-three patients were given hyperbaric oxygen. Fifty-one patients were admitted to the pediatric intensive care unit, 18 patients have had a severe clinical course, and 6 patients have died. The risk factors associated with severe disease course were determined to be low Glasgow Coma Scale score, high leukocyte count, and high troponin T levels at presentation. CONCLUSIONS: Glasgow Coma Scale score, leukocyte count, and troponin T level may be beneficial in predicting clinical outcomes and tailoring therapy in children with CO poisoning.

Comparison between carbon monoxide poisoning from hookah smoking versus other sources.

Introduction: Carbon monoxide exposure is a relatively unknown risk of smoking hookah. Dozens of cases of hookah-associated carbon monoxide toxicity have been described over the past decades, but smoking hookah is generally perceived as safe. Only recently have larger series of hookah-associated carbon monoxide toxicity been published. This study evaluates the incidence of hookah-associated carbon monoxide toxicity over 4 years, and compares the exposures from hookah against other carbon monoxide sources.Methods: This is a retrospective cohort study of all patients with carbon monoxide toxicity referred for hyperbaric oxygen therapy at an urban hyperbaric oxygen referral center from January 2015 through December 2018. Cases of hookah-associated carbon monoxide toxicity were compared to patients exposed to other carbon monoxide sources, with an analysis of patient comorbidities, symptomatology, and laboratory evaluation.Results: Over a 48-month period, 376 patients underwent hyperbaric oxygen therapy for carbon monoxide exposure. After exclusions, 265 patients with carbon monoxide toxicity from various sources were analyzed. There were 58 patients with hookah-associated carbon monoxide toxicity (22%). The proportion of hookah-associated carbon monoxide cases increased markedly in the latter years: 2015: 9.5%, 2016: 8.6%, 2017: 24.1%, 2018 41.6%. In the final 2 years analyzed, hookah smoking was the most frequent source of carbon monoxide toxicity referred for therapy. Hookah-associated carbon monoxide patients were younger(28.1 vs. 45.0 years, mean difference 16.8 years, 95% confidence interval: 11.5, 22.1 years, p < 0.001) and more likely to be female (60% vs. 46.6%, p = 0.06) than patients exposed to other carbon monoxide sources. The mean difference in carboxyhemoglobin concentration between hookah associated and those exposed to other carbon monoxide sources was 4.6% (mean 20.1% vs. 24.6%, 95%CI: 1.7, 7.5, p = 0.002).Conclusion: A substantial portion of patients with severe carbon monoxide toxicity was exposed through smoking hookah. The incidence of hookah-related carbon monoxide toxicity appears to be increasing.

Carbon monoxide poisoning.

Despite established exposure limits and safety standards as well as the availability of carbon monoxide (CO) alarms, each year 50,000 people in the United States visit emergency departments for CO poisoning. Carbon monoxide poisoning can occur from brief exposures to high levels of CO or from longer exposures to lower levels. Common symptoms can include headaches, nausea and vomiting, dizziness, general malaise, and altered mental status. Some patients may have chest pain, shortness of breath, and myocardial ischemia, and may require mechanical ventilation and treatment of shock. Individuals poisoned by CO often develop brain injury manifested by neurological problems, including cognitive sequelae, anxiety and depression, persistent headaches, dizziness, sleep problems, motor weakness, vestibular and balance problems, gaze abnormalities, peripheral neuropathies, hearing loss, tinnitus, Parkinsonian-like syndrome, and other problems. In addition, some will have cardiac issues or other ailments. While breathing oxygen hastens the removal of carboxyhemoglobin (COHb), hyperbaric oxygen (HBO2) hastens COHb elimination and favorably modulates inflammatory processes instigated by CO poisoning, an effect not observed with breathing normobaric oxygen. Hyperbaric oxygen improves mitochondrial function, inhibits lipid peroxidation transiently, impairs leukocyte adhesion to injured microvasculature, and reduces brain inflammation caused by the CO-induced adduct formation of myelin basic protein. Based upon three supportive randomized clinical trials in humans and considerable evidence from animal studies, HBO2 should be considered for all cases of acute symptomatic CO poisoning. Hyperbaric oxygen is indicated for CO poisoning complicated by cyanide poisoning, often concomitantly with smoke inhalation.

Clinical Characteristics of Pediatric Patients With Carbon Monoxide Poisoning.

OBJECTIVES: Carbon monoxide (CO) poisoning is a common and deadly form of poisoning that is often treated with hyperbaric oxygen. The characteristics of children exposed to CO and then treated with hyperbaric oxygen have not been delineated. The purpose of this study was to describe the clinical characteristics of children treated with hyperbaric oxygen therapy for CO poisoning at a regional hyperbaric referral center. METHODS: The study is based on a retrospective review of data extracted from the medical records of children (age <19 years) who were referred to our center for hyperbaric oxygen therapy for CO poisoning between 2008 and 2013. Inferential analyses were used to compare demographic characteristics, serum carboxyhemoglobin (COHb) levels, and presenting symptoms. RESULTS: Forty-seven children met our study criteria. Their mean age was 8.9 years, and their mean COHb level was 14.3% (range, 3.4%-30.1%). Severity of symptoms did not correlate with serum COHb levels; however, neurologic symptoms at presentation were more common in patients with a COHb level greater than 25%. There was a correlation between increasing age and higher COHb levels and between COHb and lactate levels. CONCLUSIONS: Our retrospective review of patients' records showed no correlation of serum COHb levels with symptoms on presentation; however, a correlation was found between increasing age and COHb level as well as lactate level and COHb level.

S-100ß 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-100ß 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-100ß 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-100ß levels was significantly higher in patients with severe poisoning and those with DNS. Receiver operating characteristic curve analysis revealed that S-100ß 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-100ß was significantly higher than that of COHb, while its specificity and overall accuracy were significantly higher than those of HBO criteria. CONCLUSION: Serum S-100ß 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.

Trends and characteristics of cases when serial carboxyhemoglobins are obtained.

BACKGROUND: Carboxyhemoglobin (COHb) levels are obtained when there is suspicion for carbon monoxide (CO) exposure. Serial COHb levels are sometimes obtained despite the well-established half-life of COHb with oxygen supplementation. We sought to evaluate the trends and characteristics associated with obtaining serial carboxyhemoglobin levels. METHODS: A retrospective review was performed at an academic medical center for all inpatient and emergency department cases with either single COHb or serial COHb levels from 1 April 2010 through 31 March 2015. Data collected included age, gender, pregnancy status, smoking history, encounter month, admission status, oxygen administration, fire or burn history, vital signs, presenting symptoms, hyperbaric oxygen (HBO2) therapy use, initial pH, troponin, lactate, and COHb levels. The time and change in values between serial levels were also obtained. RESULTS: 624 cases were identified, with 106 (17%) having multiple carboxyhemoglobin levels. A mean of 2.6 (range 2 - 9) serial COHb levels were obtained. The average initial COHb was 8.9%. Subsequent serial levels were obtained on average at 353, 663 and 1,095 minutes and averaged 2.8%, 1.8% and 1.1% respectively. Serial COHb levels were obtained more commonly in burn patients, those admitted to the ICU and those who had HBO2 therapy. Four patients had an increase in COHb level on serial testing. The largest increase of these was from 2.0% to 3.9%. CONCLUSION: Serial COHb levels were not infrequent in this study. No clinically significant increase in COHb was identified by serial testing. Further studies should examine the clinical utility of such practices.

Outcome and prognostic factors of patients treated in the intensive care unit for carbon monoxide poisoning.

BACKGROUND: Carbon monoxide (CO), a colorless and odorless gas, is one of the common causes of poisoning-related deaths worldwide. CO poisoning can result in hypoxic brain damage and death, but intensive care can improve the likely outcome for critically ill patients. However, there is a paucity of clinical data regarding the prognostic factors and association between organ dysfunction and clinical outcome of patients treated for CO poisoning in the intensive care unit (ICU). METHODS: We performed a retrospective study of patients admitted to a university affiliated hospital ICU between July 2001 and December 2010 following CO poisoning. Outcomes were survival to ICU discharge and to hospital discharge. RESULTS: Seven hundred and eighty-seven patients were admitted to the university hospital following CO poisoning, of which 140 (17.8%) were admitted to the hospital ICU. The overall mortality rate of the patients admitted to the ICU was 14.3% (20/140). Univariate analysis indicated that non-surviving patients with CO poisoning were more likely to have initial blood carboxyhemoglobin (COHb) level > 30%, shock, acute respiratory failure, Acute Physiology and Chronic Health Evaluation II (APACHE II) score ≥ 25, Glasgow coma scale (GCS) score of 3, acute renal failure, dysfunction or failure of more than 3 organs, low blood pH, low HCO3- level, high potassium level, and high glucose level. They were also more likely to have not received hyperbaric oxygen (HBO) intervention. Multivariate logistical regression analysis indicated that the mortality rate of patients treated in the ICU for CO poisoning was higher if their initial APACHE II score was ≥25, GCS was 3, and more than 3 organs were dysfunctional. Moreover, HBO intervention in ICU significantly decreased patients' risk of mortality due to CO poisoning. CONCLUSION: In conclusion, we observed that APACHE II score >25, GCS 3, and dysfunction of more than 3 organ systems on admission to emergency department was associated with a significant mortality risk in patients treated in the ICU for CO poisoning. Moreover, HBO therapy could reduce the risk of mortality in patients with CO poisoning in ICU.

Carbon monoxide poisoning from waterpipe (narghile) smoking in a child.

Shisha smoking has spread to many countries since the 1990s and is now a global phenomenon among adolescents. Notwithstanding the connotations of conviviality of shisha smoking, it is in fact highly dangerous since the smoke inhaled contains toxic substances. Carbon monoxide (CO) poisoning carries a high risk of neurological and neuropsychological sequelae such as memory loss, impaired concentration, mood disorders, and various other symptoms. We report a case of severe CO poisoning in a 13-year-old boy after smoking shisha that caused loss of consciousness and seizure. To our knowledge, there have as yet been no reports of cases involving children. We present some epidemiological data on shisha smoking in adolescents as well as on CO intoxication.

Severe unintentional first trimester carbon monoxide poisoning: case report.

BACKGROUND: The fetus is uniquely susceptible to carbon monoxide (CO) exposure. We present a case of severe unintentional CO poisoning in the first trimester of pregnancy. CASE: A 23-year-old G5P2022 female at 11 weeks' gestational age sat in a car with the engine idling. She was unaware that the vehicle's exhaust pipe was blocked with snow. She was found to be unresponsive, with an initial carboxyhemoglobin (COHb) concentration of 47.1%. She underwent emergent treatment with hyperbaric oxygen therapy. The remainder of her pregnancy was complicated by a diagnosis of myasthenia gravis. She delivered a full-term infant who was noted to have persistently small head circumference. DISCUSSION: Fetal hemoglobin binds to CO more tightly than adult hemoglobin, and fetal carboxyhemoglobin concentrations are reported to exceed maternal levels. Fetal abnormalities may occur after CO poisoning in pregnancy and vary based on the gestational age of the fetus at the time of the exposure as well the chronicity of the exposure. CONCLUSION: Fetal survival after maternal CO exposure is possible even with significantly elevated maternal COHb concentrations, although teratogenic effects may occur depending on the timing of exposure.

Investigating the color of the blood stains on archaeological cloths: the case of the Shroud of Turin.

The unique reddish blood stains on the archaeological cloth known as the Shroud of Turin caught the attention of several scholars, who proposed different hypotheses to explain the unusual blood color. To date, just a few hypotheses have been tested experimentally, and the results are debatable. In this paper, we test the strength of two hypotheses (namely, the presence of carboxyhemoglobin and the long-term influence of ultraviolet light on high-bilirubin blood) by the spectral reflectance of the blood stained regions on the Shroud and by color analyses of ultraviolet irradiated high-bilirubin blood stains on linen. The relevance of these simple methods to the study of stained textiles is discussed.

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.

Cardiovascular Abnormalities in Carbon Monoxide Poisoning.

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

Comparison of normobaric vs. hyperbaric oxygen in the relief of carbon monoxide headache pain.

BACKGROUND: Headache is the most common symptom in carbon monoxide (CO) poisoning. While the mechanism of CO-induced headache is not well defined, it is felt that cerebral vasodilation plays a role. Clinical experience has demonstrated oxygen breathing is effective in resolving CO headache. However, the effectiveness of normobaric oxygen has never been compared to hyperbaric oxygen in this regard. METHODS: A 2016 paper by Ocak, et al. reported the response of CO headache pain severity to four hours of normobaric oxygen breathing in 82 patients using a 0-10 analog scale. The demographics, carboxyhemoglobin levels and response to therapy from that report were compared to data obtained by Hampson, et al. in an earlier study, but never published, using the same pain assessment method in 73 patients with CO headache and treated with hyperbaric oxygen. RESULTS: Comparing the normobaric and hyperbaric groups, neither average age nor presenting carboxyhemoglobin levels were significantly different. Baseline pain intensity scores were 6.5 ± 3.1 vs. 6.2 ± 2.6 (p=0.444) and post-treatment scores 1.5 ± 2.6 vs. 1.0 ± 1.5 (p=0.184) respectively on a 0-10 scale. CONCLUSIONS: In these two well-matched populations of patients with CO-induced headache pain, degree of resolution was not significantly different between normobaric and hyperbaric oxygen treatment.

[Evolution of the carboxyhemoglobinemia and methemoglobinemia during endoscopic resection: An observational study]. / Évolution de la carboxyhémoglobinémie et de la méthémoglobinémie lors de résections endoscopiques : une étude observationnelle.

AIM OF THE STUDY: Combustion of organic tissues due to endoscopic resection could induce methemoglobin (MetHb) and carboxyhemoglobin (COHb) formation. The aim of this study is to evaluate MetHb and COHb formation in patients undergoing prostatic or bladder endoscopic procedures. METHODS: COHb and MetHb measurements were performed in 44 patients at the beginning and end of the procedure. A third measurement was done in patients who stayed more than one hour in the recovery room. Means were compared using Student t-test, simple regressions were used for quantitative variables and ANOVA for categorical variables. Multiple linear regressions were used for multivariate analysis. RESULTS: COHb increased by 0.5±0.9 % (95 % CI: 0.2 to 0.7 % P=0.001). MetHb increase was 0.0±0.4 % (95 % CI: -0.1 to 0.2 % P=0.552). In univariate analysis, the variables associated with COHb increase are the length of surgery, the amount of irrigation fluid and location (prostate or bladder) of the procedure. In the multivariate model, COHb increase is associated with the amount of liquid and the location. CONCLUSION: MetHb did not increase during endoscopic surgery. In contrast, COHb increases, and can, in some patients, exceed 2-4 %. This could be responsible for a decreased angina threshold in patients with ischemic heart disease. LEVEL OF EVIDENCE: 4.