Carboxyhemoglobin Formation Research Articles

Exposure levels for carbon monoxide in nuclear submarine atmosphere

This work proposes exposure limits for carbon monoxide in the nuclear submarine environment. Linear and non-linear forms of the Coburn-Foster-Kane equation were used to evaluate carbon monoxide exposure for an environment with low oxygen content, different exposure times and crew physical activity levels. We evaluated the 90-day Continuous Exposure Guidance Level, 24-h and 1-h Emergency Exposure Guidance Levels and 10-day and 24-h Submarine Escape Action Levels. The results showed that the concentration of carbon monoxide in the environment must not exceed 9 ppm for the 90-day Continuous Exposure Guidance Level, 35 ppm for the 24-h Emergency Exposure Guidance Level, 90 ppm 1-h Emergency Exposure Guidance Level, 60 ppm for the 10-day Submarine Escape Action Level and 80 ppm for the 24-h Submarine Escape Action Level. Comparing these values with those established by the National Research Council for the United States Navy, the limits proposed by this work are verified to be lower, which may indicate a risk to the health of the crew. They also show the impact of the crew's level of physical activity on the formation of carboxyhemoglobin.

Carboxyhemoglobin as a diagnostic and prognostic biomarker of hemolytic anemias in dogs.

Endogenous production of carbon monoxide during hemoglobin metabolism leads to the formation of carboxyhemoglobin. Carboxyhemoglobin concentration is abnormally high in humans with hemolytic anemia (HA). Measurement of carboxyhemoglobin concentration can discriminate HA from other forms of anemia. Twenty-seven dogs with HA (immune-mediated HA, n=22; microangiopathic HA, n=5), 27 dogs with non-HA (kidney disease, n=14; immune-mediated thrombocytopenia, [n=6]; miscellaneous, n=7) and 24 nonanemic control dogs. Prospective cohort study. Carboxyhemoglobin quantification, a CBC and biochemistry profile were performed upon admission, and survival to hospital discharge and at 30 days were the measured outcomes. Groups were compared by the Mann-Whitney and Kruskal-Wallis tests. Receiver-operator characteristic (ROC) analyses were used to examine the predictive utility of carboxyhemoglobin for the diagnosis of HA in anemic dogs. Carboxyhemoglobin (median [interquartile range]) differed between dogs with HA (7.7% [2.5%]) and non-HA (3.6% [1.05]; P < .001) and dogs with HA and nonanemic dogs (3.5% [0.65%]; P < .001). No difference was detected between nonHA and nonanemic dogs. The area under the ROC curve for carboxyhemoglobin as predictor of HA in anemic dogs was 0.997 (95% CI, 0.99-1.00). Three optimal cut-off points were identified, including 5.05%, 4.55% and 4.85%, with corresponding sensitivity/specificity of 92.6%/100%, 100%/92.6% and 96.3%/96.3%, respectively. Neither carboxyhemoglobin nor any of the CBC or chemistry analytes were associated with survival. Carboxyhemoglobin proved an excellent predictor of HA in dogs and might constitute a useful, ancillary tool for diagnosing and monitoring hemolytic anemias.

Mass Carbon Monoxide Poisoning in a Family: A Case Report from Nepalgunj

Carbon monoxide (CO) is a colorless, odorless gas produced as a by-product of the complete combustion of hydrocarbons. CO binds rapidly to Haemoglobin (Hb), leading to the formation of carboxyhemoglobin (COHb), so the oxygen-carrying capacity of the blood will be decreased and causing tissue hypoxia. We present the case of accidental carbon monoxide poisoning in a family where four members were reported dead and three unconscious in the morning after sleeping in a room with burning briquettes. Carbon monoxide poisoning can be fatal. Public awareness about such poisoning is essential for prevention.

Why Do Marijuana and Synthetic Cannabimimetics Induce Acute Myocardial Infarction in Healthy Young People?

The use of cannabis preparations has steadily increased. Although cannabis was traditionally assumed to only have mild vegetative side effects, it has become evident in recent years that severe cardiovascular complications can occur. Cannabis use has recently even been added to the risk factors for myocardial infarction. This review is dedicated to pathogenetic factors contributing to cannabis-related myocardial infarction. Tachycardia is highly important in this respect, and we provide evidence that activation of CB1 receptors in brain regions important for cardiovascular regulation and of presynaptic CB1 receptors on sympathetic and/or parasympathetic nerve fibers are involved. The prototypical factors for myocardial infarction, i.e., thrombus formation and coronary constriction, have also been considered, but there is little evidence that they play a decisive role. On the other hand, an increase in the formation of carboxyhemoglobin, impaired mitochondrial respiration, cardiotoxic reactions and tachyarrhythmias associated with the increased sympathetic tone are factors possibly intensifying myocardial infarction. A particularly important factor is that cannabis use is frequently accompanied by tobacco smoking. In conclusion, additional research is warranted to decipher the mechanisms involved, since cannabis use is being legalized increasingly and Δ9-tetrahydrocannabinol and its synthetic analogue nabilone are indicated for the treatment of various disease states.

The comparative evaluation of the criteria used to determine the critical values of the partial density of carbon monoxide as part of the calculation of time to the blocking of escape routes in case of a room fire

Introduction. Critical values of the partial density of gas, the toxic dose or relative mass of carboxyhemoglobin in human blood serve as the criteria determining the time to the blocking of escape routes due to the presence of carbon monoxide. However, the comparative analysis of the effect produced by the selected criterion on the time to the blocking of escape routes due to the presence of this gas has not been conducted yet.Goals and objectives. The purpose of the article is to compare the values of the time to the blocking of escape routes by carbon monoxide obtained using various methods of determining the critical values of the carbon monoxide density. Towards this end, experimental studies on combustion processes of various solid and liquid combustible substances and materials were conducted in a small-scale test unit, and calculations of the time to the blocking of escape routes with carbon monoxide were made on their basis.Theoretical fundamentals. The amount of carbon monoxide, inhaled during a fire, is calculated using experimentally measured partial densities of CO and mathematical models designated for the calculation of the toxic dose of this gas and formation of carboxyhemoglobin in human blood.Results and discussion. Experimental dependencies between the testing time and medium-volume densities of monoxide emitted during the combustion of the “low smoke” PVC cable sheathing, timber (pinewood), chocolate, transformer oil and vegetable oil are presented. The authors obtained theoretical dependencies between the toxic dose and mass concentration of carboxyhemoglobin in human blood, on the one hand, and the time for the combustible materials, analyzed in the article. It has been found that the values of time to the blocking of escape routes due to the presence of carbon monoxide may differ significantly depending on the method used to determine the critical values of the carbon monoxide density.Conclusions. Standard methods, used to calculate the time to the blocking of escape routes due to the presence of carbon monoxide, employ the value of the critical partial density which may involve a substantial overestimation of the above time frame and the underestimation of the toxic effect produced on a person in the process of his/her evacuation. Therefore, it is necessary to apply all methods, discussed in the article, to select the minimum value of the above time frame.

Carbon monoxide: modern concepts to the treatment of acute poisonings (literature review)

Introduction. Carbon monoxide (CO) is one of the most common causes of chemical injuries and the main toxic factor in the people death in fires. The mechanism of the toxic effect of CO, associated with the formation of carboxyhemoglobin and the development of hypoxia, determines the rapid development of the clinical picture of acute intoxication and the need for emergency first aid and medical care to the poisoned. Material and methods. Literature sources, summarized in the bibliographic databases eLIBRARY.RU, PubMed and Scopus, were the material for analysis. Results. First aid is based on quickly removing the victim from the fire zone or other area with a high concentration of CO and providing him with oxygen as soon as possible. During medical evacuation, it is necessary to carry out continuous inhalation of 80-100% oxygen, to ensure rest and warmth of the victim. In the emergency department of the hospital, oxygen inhalation and maintenance therapy should be continued, clinical and laboratory diagnostic measures aimed at assessing the severity of intoxication, identifying complications and concomitant pathology should be performed. In the case of severe CO poisoning, medical care continues to be provided to the victims in the intensive care unit or in the oxygen-barotherapy unit. The main antidote for CO poisoning is oxygen, which can be used in two versions - normobaric or hyperbaric oxygenation. As a pharmacological antidote to CO, zinc bisvinylimidazole diacetate (acizol) which can accelerate the breakdown of carboxyhemoglobin, improve the oxygen-binding and gas-transport properties of blood, as well as the dissociation of oxyhemoglobin in tissues is used. Along with antidotes, an important role in the treatment of CO poisoning is played by pathogenetic and symptomatic therapy aimed at the prevention and treatment of toxic encephalopathy, brain edema, cognitive dysfunction, toxic myocardiodystrophy and arrhythmia, prevention of pneumonia, correction of the acid-base state, compensation of the energy needs of the body, etc. Conclusion. Further improvement of existing means and methods for the treatment of intoxication, the development and introduction of new antidots into medical practice will increase the effectiveness of therapeutic measures, reduce the number of deaths and disabilities after acute poisoning with carbon monoxide.

Carbon monoxide: mechanism of toxic action, pathogenesis and clinical manifestations of acute intoxication

Introduction. Carbon monoxide (CO) remains one of the most common causes of acute poisoning and death, both in everyday life and in emergency situations, especially in fires.Material and methods. The paper summarizes information about the regulatory effects, mechanisms of toxic action, pathogenesis and clinical picture of intoxication, as well as predictors of the severity of CO poisoning.Results. The main mechanism of the toxic effect of CO is due to its ability to bind to the protohemal iron of hemoglobin (Hb) to form carboxyhemoglobin (HbCO). The toxicity of CO may also be enhanced by impaired functions of the myoglobin of the myocardium and skeletal muscles, mitochondrial cytochrome oxidase, and iron-containing enzymes of the antioxidant system. The leading link in the pathogenesis of acute CO intoxication is a violation of the oxygen transport function of hemoglobin and the associated development of hemic and tissue hypoxia. CO-induced cell and tissue damage due to the induction of mitochondrial dysfunction, oxidative stress, free radical hyperproduction, lipid peroxidation, inflammation, and apoptosis also play a role in the pathogenesis of intoxication.Conclusion. The mechanism of toxic action of CO, associated primarily with the formation of carboxyhemoglobin and the development of hypoxia, determines the clinical manifestations of acute intoxication, which depend on the concentration of CO and the duration of exposure, but are almost always associated with the central nervous system and cardiovascular system.

Production of carbon monoxide from a He/CO2 plasma jet as a new strategy for therapeutic applications

AbstractA new method to deliver carbon monoxide (CO) for medical applications is presented using a kHz‐driven helium plasma jet with a 1% CO2 admixture. Despite being known for its anti‐inflammatory, vasorelaxing, and anti‐apoptotic effects, a possible role of CO generated from plasma for the treatment of various diseases has so far been neglected. Here, we show that CO production of a plasma jet can be tuned from 100 to 2000 ppm. The number of CO molecules produced per pulse is in the range of 1 × 1012 to 1.5 × 1013. To assess the delivery of CO, mouse blood hemoglobin was used as a scavenger of CO and the consequent formation of carboxyhemoglobin was quantified. This study reveals for the first time that plasma can generate and deliver CO for therapeutic interventions.

Methodical approach to determining permissible time limits of intermittent carbon monoxide exposure in rescuers

Relevance. Current operation time limits under hazardous chemical conditions (“emergency regulations”) have been developed mainly for a limited number of emergency situations occurring in spacecraft, submarines or other specific objects. At the same time, many emergencies accompanied by large-scale releases of toxic combustion products from various materials and compounds into the environment are not limited to these facilities. Therefore, risks associated with toxic effects of chemicals should be predicted, since permissible time limits with adequate performance of personnel under certain chemical exposures are used for individual protection (time-based protection).Intention: On the basis of physiological aspects, the peculiarities of the work performed by rescuers and the requirements for organizing and conducting emergency rescue operations, to propose a methodical approach to determining the permissible time for rescuers in conditions of intermittent carbon monoxide release.Methodology. The scientific works and results of experiments in the research area were analyzed. Systematization and generalization of empirical and theoretical data, traditional analysis of documents and publications were used with the least squares approximation.Results and Discussion. Specific effects of various carbon monoxide concentrations are shown for different exposure times. Critical concentrations and exposure times are revealed, functional relationships between permissible time of operation and carbon monoxide concentrations are determined. Carboxyhemoglobin formation and effects were taken into account.Conclusion. The data given in the article are an important basis for organizing and conducting emergency rescue operations at increased concentrations of carbon monoxide.

Hemoglobin: A General Review

Hemoglobin (Hb) is red blood corpuscle pigment causing red color in blood with centrally located iron atom, responsible for oxygen transport having molecular weight of a tetramer of 64,458 g/mol. The oxygen binding properties of hemoglobin are affected by pH and presence of carbon dioxide. It cause different clinical problems due to its high or low concentration in blood. Poisoning of Hb can also occur by combination of Hb with carbon monoxide resulting in formation of carboxyhemoglobin. Besides carboxyhemoglobin, sulfhemoglobin and methemoglobin are also derivatives of Hb.

Carbon monoxide poisoning

Carbon monoxide poisoning may be suicidal, homicidal and in many cases it is accidental. Poisoning is due to formation of carboxyhaemoglobin, which interferes transfers of oxygen and leads to appearance of symptoms.1 Which are not specific and may similar to coved19. Symptoms depends upon concentration of CO in surroundings. Antidote of CO is oxygen. In severe cases, can use oxygen with pressure CO.

Diagnostic utility of arterial spin labeling in identifying changes in brain perfusion in patients with carbon monoxide poisoning

ObjectiveCarbon monoxide (CO) poisoning is one of the most common poisonings worldwide. The affinity of hemoglobin for CO is significantly higher than that for oxygen, and the formation of carboxy-hemoglobin leads to a decrease in the capacity of blood to transport oxygen to tissues, tissue hypoxia, and early perfusion changes in the affected tissue. This study aimed to investigate the utility of arterial spin labeling perfusion imaging (ASL-PI) in revealing cerebral vascular hemodynamic changes in patients presenting to the emergency room with CO poisoning and to compare findings with those from diffusion-weighted imaging (DWI). MethodThis study was conducted between November 2016 and May 2019 and was approved by the local ethics committee. DWI and ASL-PI examinations were performed in 83 patients who presented to the emergency room with CO poisoning. Four regions—the cerebral cortex, basal ganglia, cerebral white matter, and cerebellum—were evaluated for alterations in perfusion and diffusion, and findings from DWI and ASL-PI were compared. ResultsThe study group included 39 (50.6%) females and 38 (49.4%) males, with a mean (±SD) age of 40.08 ± 20.41 years (range, 7–86 years). DWI revealed restricted diffusion in 10 regions in 6 (7.8%) patients, including the basal ganglia (n = 2), cerebral white matter (n = 2), cerebral cortex (n = 3), and the cerebellum (n = 3). ASL-PI revealed hypo-perfusion in 64 regions in 36 (46.8%) patients, including the basal ganglia (n = 21), cerebral white matter (n = 12), cerebral cortex (n = 23), and cerebellum (n = 7). ConclusionASL-PI provided additional information when used to identify perfusion changes in the brains of individuals who experienced CO poisoning and was superior to DWI as it revealed early changes in the brain. Considering its limitations, ASL-PI can be routinely used with DWI in cases of CO poisoning.

Effects of smoking on hemoglobin and erythrocytes sedimentation rate and its association with ABO blood groups

Context: “Smoking causes variation in different parameters of blood like hemoglobin (Hb) and erythrocyte sedimentation rate (ESR).” Continuous exposure to carbon monoxide leads to the formation of carboxyhemoglobin, an inactive form of Hb with no oxygen-carrying capacity; carboxyhemoglobin also leads to shifting in the Hb dissociation curve on the left side, causing a reduction in the ability of Hb to deliver oxygen to the tissue. Aims: The aim of this study was to compare the effect of cigarette smoking on Hb and ESR between smokers and nonsmokers and its association with ABO blood groups. Settings and Design: A total of 100 subjects which included 50 smokers and 50 age-matched nonsmoker controls were included in this study. Material and Methods: 5 ml of venous blood was collected by venipuncture method and Hb was measured by cyanmethhemoglobin method, ESR by Westergren's method, and ABO blood grouping by slide method. Statistical Analysis Used: Statistical software SPSS version 20 (SPSS, Chicago, Illinois) was used. Student's t test was performed for parametric numerical data and Chi-square test was performed for nonparametric categorical data. A value of P

Changes in the morphology of erythrocytes after &lt;i&gt;in vitro&lt;/i&gt; exposure of blood to carbon monoxide

Background: One of the pathological effects of carbon monoxide (CO) on blood is the formation of carboxyhemoglobin. Carboxyhemoglobin completely blocks oxygen transfer; therefore, there is a net decrease in oxygen transport by red blood cells potentially resulting in tissue hypoxia. The effects of CO on blood can also damage cell membranes. Atomic force microscopy (AFM) has been recognized as effective for investigation into the mechanisms of structural damage in erythrocyte membranes.Aim: By means of AFM, to identify characteristics of changes in morphology and aggregation of erythrocytes exposed to CO in vitro.Materials and methods: All experiments were performed in vitro. We studied the morphology of erythrocytes and their aggregates with AFM. Blood sampling (150 μl) in microvettes with EDTA (Sarstedt AG &amp; Co., Germany) was carried out during a prophylactic work-up of 5 volunteers. To obtain CO in a test tube, formic acid was mixed with sulfuric acid 1:1. Blood levels of carboxyhemoglobin were measured by spectrophotometry. A nonlinear fitting method of the experimental spectra was used to calculate the concentrations of hemoglobin derivatives in blood. Statistical analysis was done with the Origin software (OriginLab Corporation, Northampton, MA, USA).Results: After CO exposure, a shift in peaks was observed. At exposure time t₂=320 s, the percentage of carboxyhemoglobin (CHbCO) was 88±2%. As a result of blood exposure to CO, at t₁=160 s 10% of the cells differed in their shape from discocytes, whereas at t₂=320 s their proportion was 38%. With increasing duration of exposure to CO, erythrocyte aggregation occurred with formation of their large conglomerates up to 30 μm in size. In the control smear, the proportion of discocytes was 96±2%, and the remaining 4±1% of the cells had the form of echinocytes. The cell diameter (Dcont) was in the range 7.5±0.8 μm. After blood exposure to CO at t₁=160 s in the monolayer, 28±5% of cells had a diameter less than&lt;5.7 μm. After CO exposure at t₂=320 s, the proportion of cells with a diameter of less than&lt;5.7 μm increased to 72±11%.Conclusion: The experiments have shown that blood exposure to CO changed the morphology of erythrocytes. The formation of interconnected structures made of red blood cells was observed. With increased time of exposure, erythrocytes demonstrated aggregation with conglomerate formation.

SYSTEM FOR PREDICTION OF CARBOXYHEMOGLOBIN LEVELS AS AN INDICATOR FOR ON-TIME INSTALLATION OF SELF-CONTAINED SELF-RESCUERS IN CASE OF FIRE IN UNDERGROUND MINES

Accidents associated with fires and exposure to toxic gases are one of the main causes of injury and death in underground mines. This kind of accidents requires implementation of systems and approaches to tighten and promote underground mine safety. This paper introduces a system for real-time monitoring of carbon monoxide (CO) for prediction of carboxyhemoglobin (COHb) levels in human blood for an early-warning platform and indicator for on-time installation of self-contained self-rescuer (SCSR) device in case of fire in underground mines. The proposed system seamlessly integrates monitoring and analyzing approaches using Arduino, sensor board and smartphone with a specially developed app with Coburn, Forster, Kane (CFK) model for the prediction of COHb (%). This system is designed to predict the COHb (%) formation and also alert and identify the safety limit for on-time installation of SCSR in which the user is still not affected by the clinical symptoms of CO inhalation. The idea for this paper derived from the Sago mine explosion report from which confusion and insufficient training are identified about when to install the SCSR. The main contribution of this paper is the development of a prototype system with an open source and cost-effective platform for solving the problems associated with on-time installation of SCSR, on which the process for effective evacuation in case of fire scenario in underground mines depends. Keywords: Underground mines, safety, system, SCSR, COHb DOI 10.35180/gse-2019-0021

Investigation into the potential for post-mortem formation of carboxyhemoglobin in bodies retrieved from fires.

The forensic investigation of a deceased person retrieved following a fire includes measuring carboxyhemoglobin. A carboxyhemoglobin saturation above 10% is considered indicative of respiration during a fire, implying the person had been alive. This relies on the assumption that carbon monoxide will not diffuse into blood used for toxicological analysis. This project investigated the potential for carbon monoxide to passively diffuse into a body and if carboxyhemoglobin levels could become elevated post-mortem. Stillborn piglets with intact skin were exposed to carbon monoxide. Carboxyhemoglobin formed in the hypostasis of the skin, but carboxyhemoglobin levels in blood from the heart and chest cavities were not significantly elevated. However, defects in the skin over body cavities (producing breaches to replicate cases with stab wounds or heat damage) resulted in cavity blood carboxyhemoglobin levels above 10%. A review of fire death cases in South Australia 2000-2015 was performed to determine the origin of the blood samples used for toxicological analysis and the incidence of cases with breaches of body cavities. This revealed a small number of cases in which blood from the cavities had been analyzed when cavity breaches were present. Thus, there is a potential for significant elevation of carboxyhemoglobin saturation post-mortem in forensic casework involving bodies retrieved from fires.

Delayed neurological sequelae in carbon monoxide poisoning – a case report and present state of knowledge

Wstęp: Tlenek węgla (CO) jest jedną z najczęstszych przyczyn śmiertelnego zatrucia poprzez drogi oddechowe, spowodowane głównie niesprawnością urządzeń grzewczych. Tlenek węgla prowadzi do hamowania transportu tlenu przez połączenie z hemoglobiną i utworzenie karboksyhemoglobiny. Objawy neuropsychologiczne określane jako opóźnione następstwa neurologiczne zatrucia pojawiają się zwykle po okresie przejaśnienia.Opis przypadku: Objawy neurologiczne pojawiły się 27 dni po zatruciu tlenkiem węgla leczonym terapią hiperbaryczną. W badaniu stwierdzono objawy mutyzmu, znaczne zaburzenia poznawcze, hipomimię, obustronną sztywność kończyn, wzmożone odruchy głębokie, obustronnie objaw Babińskiego i nietrzymanie zwieraczy. W badaniu rezonansem magnetycznym mózgowia zaobserwowano rozlane zmiany hiperintensywne obustronnie w istocie białej i w środkach półowalnych. W leczeniu stosowano wlewy amantadyny, sertralinę, lewodopę oraz piracetam, uzyskując stopniową poprawę. Pomimo poprawy stanu neurologicznego zachorowanie skończyło się zgonem. Początkowy wynik w skali Glasgow wyniósł 7 pkt, obserwowano leukocytozę, podwyższony poziom troponiny. Wyniki te mogą być potencjalnie wykorzystane jako czynniki predykcyjne rokowania w przebiegu obserwowanych objawów neurologicznych.Wnioski: Kolejne badania powinny mieć za cel lepsze poznanie patogenezy powikłań neurologicznych w przebiegu zatrucia CO w celu prewencji i skutecznego leczenia schorzenia, które powoduje istotną niepełnosprawność.

Fire deaths – a review and an experimental investigation of post-mortem formation of carboxyhaemoglobin

The forensic investigation of deceased retrieved following a fire includes determining if death occurred before or during the event. A blood carboxyhaemoglobin level above 10% is considered indicative of respiration during a fire, implying that an individual was not deceased before the event. Previous spectroscopic studies have revealed that oxygen can passively diffuse through the skin and re-oxygenate haemoglobin. It was therefore questioned if carbon monoxide could also dermally diffuse and elevate post-mortem blood carboxyhaemoglobin levels, which could falsely insinuate that an individual had been alive and respired during a fire. Exposing both oxygenated and deoxygenated forms of haemoglobin to carbon monoxide converted them to carboxyhaemoglobin. This was measured using an ISP-REF Integrating sphere coupled to a USB spectrometer by fibre optic probe. Stillborn piglets were exposed to carbon monoxide to show that the gas can passively diffuse through the skin, resulting in formation of carboxyhaemoglobin in hypostasis, which was confirmed by observing a shift in the absorption spectrum. Piglets with significant cavity breaches, as could be found in cases with extensive stab/bullet wounds or heat defects, exposed to carbon monoxide demonstrated cavity carboxyhaemoglobin levels above 10% which could falsely suggest respiration of carbon monoxide had occurred.

Investigation into the potential for post-mortem formation of carboxyhaemoglobin in bodies retrieved from fires

Investigation into the potential for post-mortem formation of carboxyhaemoglobin in bodies retrieved from fires

Évolution de la carboxyhémoglobinémie et de la méthémoglobinémie lors de résections endoscopiques : une étude observationnelle

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. COHb and MetHb measurements were performed in 44patients 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. COHb increased by 0.5±0.9% (95% CI: 0.2to 0.7% P=0.001). MetHb increase was 0.0±0.4% (95% CI: -0.1to 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. 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. 4.