Blood carboxyhaemoglobin and cyanide levels in fire survivors

Quantification of 2-aminothiazoline-4-carboxylic acid as a reliable marker of cyanide exposure using chemical derivatization followed by liquid chromatography-tandem mass spectrometry

In this research, we have developed a novel and simple liquid chromatography coupled with electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) method for quantification of 2-aminothiazoline-4-carboxylic acid (ATCA), which is produced by the direct reaction of cyanide (CN) with endogenous cystine. In forensic science, detection of CN is important because CN is a poison that is often used for murder or suicide, in addition to being produced by the thermal decomposition of natural or synthetic materials. However, because CN disappears rapidly from body tissue, ATCA is thought to be a more reliable indicator of CN exposure. For the method reported herein, human blood samples (20 μL) were subjected to protein precipitation followed by derivatization with 4-bromoethyl-7-methoxycoumarin. Blood spiked with ATCA at concentrations ranging from 50 to 1500 ng/mL was used to prepare a calibration curve (lower limit of quantification; 50 ng/mL, lower limit of detection; 25 ng/mL). Our method uses chemical derivatization, so unlike previously reported methods, it does not require tedious pretreatment procedures, hydrophilic interaction liquid chromatography columns, or specialized equipment. In addition, our method allows for repeatable and accurate quantification of ATCA, with intra- and inter-assay coefficients of variation of below 5.0% and below 6.0%, respectively. We used the method to analyze ATCA in postmortem human blood samples, including samples from people who had intentionally ingested CN or were fire victims. Blood ATCA concentrations were higher among people who had ingested CN or were fire victims than among people in a control group (P < 0.0001). The data reported herein demonstrate that our LC/ESI-MS/MS method can be used to detect and quantify ATCA in postmortem blood samples and that CN exposure strongly affects ATCA concentration, providing a useful tool for detection of CN poisoning.

Elevated Methemoglobin Levels in a Patient Treated with Hydroxocobalamin After Suspected Cyanide Exposure

BACKGROUND

Cyanide (CN) toxicity commonly occurs during enclosed-space fires. Historically, the first step in treating CN toxicity utilized amyl nitrite and sodium nitrite to induce methemoglobinemia, which can be dangerous in this population. Hydroxocobalamin (OHCob), which binds to CN to form the nontoxic metabolite cyanocobalamin, is now the first-line antidote for CN toxicity, and has the advantage of not inducing methemoglobinemia.

CASE REPORT

A 62-year-old man presented to the Emergency Department (ED) after a house fire. He was intubated for respiratory distress and hypoxia with an initial carboxyhemoglobin of 1.3%, methemoglobin 0.3%, and anion gap 19. Eleven hours after presentation, his serum lactic acid was 9 mmol/L. Given his continued deterioration, 14 h after arrival he received OHCob 5 g i.v. for presumed CN toxicity. Methemoglobin concentration 4 min prior to OHCob administration was 0.7%, and 2 h after administration was 4.2%. This subsequently increased to 14.3% (16 h after OHCob administration) and peaked at 16.3% (47 h after OHCob administration), at which time he was administered a dose of methylene blue 50 mg i.v., 60 h after ED arrival. His methemoglobin concentrations fluctuated until a consistent downward trend starting at 92 h from ED arrival. He continued to deteriorate and expired on hospital day 5 with a methemoglobin concentration of approximately 6.0%. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: CN toxicity requires immediate recognition and treatment. The antidote, OHCob, is believed to not induce methemoglobinemia. However, this potential side effect must be considered by emergency physicians when treating suspected CN toxicity, especially if the patient does not improve after antidotal therapy.

Smoke inhalation injury in a 2-year-old domestic fire victim

Smoke inhalation injury is common in victims of domestic fires, among whom children are the most vulnerable. Cyanide poisoning may occur in addition to carbon monoxide poisoning and is challenging to diagnose. In France, the recommended antidotes are hydroxocobalamin for cyanide and hyperbaric oxygen for carbon monoxide. We managed a 26-month-old girl who sustained smoke inhalation injury with both carbon monoxide and cyanide poisoning during a house fire. Despite hydroxocobalamin and sodium thiosulfate therapy combined with hyperbaric oxygen, she had residual neurological impairments 3 months after the injury. The treatment challenges and detailed neurological follow-up data are described.

A Retrospective Study on Carboxyhaemoglobin Half-Life in Acute Carbon Monoxide Poisoning in Patients Treated with Normobaric High Flow Oxygen

Objective

There has been a vast difference in the reported value for carboxyhaemoglobin (COHb) half-life (COHbt&frac12;) in carbon monoxide (CO) poisoning patients breathing 100% normobaric oxygen (O2). This could be due to the fact that all previous studies were performed on heterogeneous groups of patients with different aetiology. We wished to determine the COHbt&frac12; in a homogenous group of acute CO poisoning patients who attempted suicide by burning charcoal and were treated with normobaric high flow oxygen.

Methods

It was a retrospective descriptive cohort study for a period of 60 months (January 2001 to December 2005).

Setting

Accident and Emergency Department of Tuen Mun Hospital, serving a population of 1.5 millions.

Population

We recruited all cases of CO poisoning by burning charcoal for suicidal attempt and we excluded the cases if (1) there was only one COHb measurement; (2) the patient had not received high flow O2 therapy via tightly fitting facial mask with O2 reservoir, given before the first blood sample or throughout the period until a second blood sample was taken; (3) the first COHb was <10%; (4) the second COHb was <2%; (5) there was significant co-poisoning; (6) the patient was haemodynamically unstable; or (7) the time of blood sampling was not documented. We believed that the elimination of COHb under 100% normobaric O2 was constant and followed a simple exponential decay.

Results

Forty-three (27.4%) cases met all of the selection criteria and the mean COHbt&frac12; was 78±9 minutes.

Conclusion

We believed that our patients (i.e. CO poisoning patients who committed suicide by burning charcoal) represented a homogenous group of acute CO poisoning of unique aetiology. The estimated COHbt&frac12; would be useful in deciding the length of normobaric oxygen therapy for this group of patients.

Current concepts in the pathophysiology and treatment of inhalation injury

The opinions or assertions contained herein are the private views of the author, and are not to be construed as official or as reflecting the official views of the Department of the Army or Department of Defense. Smoke inhalation injury occurs in about 10% of patients admitted to burn centres, and increases the mortality of burn patients by up to 20% over predictions based on age and burn size alone. The primary lesion in smoke inhalation injury is localized to the small airways, with alveolar injury and pulmonary oedema exercising a less prominent role during the initial phases. Injury incites a cascade of events that include ventilation-perfusion mismatch, secondary lung injury, systemic inflammation, impaired immune function, and pneumonia. The most important recent developments in the treatment of inhalation injury have included improved methods of pulmonary care targeted at the pathophysiology of the injury, such as high-frequency percussive ventilation and gentle mechanical ventilation.

Respiratory Effects of Short-Term, High-Intensity Toxic Inhalations: Smoke, Gases, and Fumes

Respiratory insufficiency resulting from inhalation of hot air, smoke, or toxic gas is a common cause of death in fire victims. Toxic gas inhalation in settings other than fires is a less common but still important cause of death and disability. Pulmonary inhalation injury and systemic intoxication from exposure to a variety of agents are discussed with regard to their pathogenesis, pathophysi ology, diagnosis, and treatment. Upper airway obstruc tion and noncardiogenic pulmonary edema are the life- threatening respiratory complications in the immediate postinhalation period. Carbon monoxide and hydrogen cyanide intoxication are frequently associated with in halation injury in fire victims. Early recognition and treatment of inhalation injury and systemic intoxication in victims of fires and industrial and environmental acci dents could well result in improved survival.

Comparison of three techniques for calculation of the Parkland formula to aid fluid resuscitation in paediatric burns

CONTEXT

Inadequate fluid resuscitation of acute burns may result in hypovolaemic shock. Excessive fluid resuscitation may result in fluid overload. A nomogram which uses the popular Parkland formula and '4-2-1' regime has been recently described to facilitate the calculation of fluid requirements in children during the first 24 h following burn injury.

OBJECTIVE

To compare the accuracy and speed of calculation of three different methods (pen and paper, electronic calculator and nomogram), which all use the Parkland formula and '4-2-1' regime to calculate maintenance and resuscitation fluid requirements for children in the first 24 h after burn injury.

DESIGN

A randomised volunteer study using computer-generated simulated patient data.

SETTING

Welsh Centre for Burns, ABM University Local Health Board, Swansea, UK. Data were collected between February 2011 and October 2011.

PARTICIPANTS

The group consisted of 36 volunteers including trainee and consultant surgeons and anaesthetists.

INTERVENTION

Thirty-six participants performed 318 calculations, using each of the three methods of calculation up to three times.

MAIN OUTCOME MEASURES

Accuracy, speed and acceptability of the different methods.

RESULTS

For nomogram, calculator and pen and paper: magnitude of error [low (≥25%), medium (≥50%) and high (≥75%)]: [5.7, 4.7 and 3.8%], [12.1, 12.1 and 7.5%], [28.6, 21.9 and 16.2%]; [P <0.001, P = 0.001 and P = 0.006]. Calculation time: [s; mean (SD)]: 121 (48), 109 (52) and 240 (140); P <0.001. The mean (SD) of the difficulty scores were 17.3 (13), 20.6 (13.4) and 62.2 (23.4); P <0.001.

CONCLUSION

The nomogram was the most accurate method of calculating fluid requirements using the Parkland formula, was only slightly slower than the electronic calculator and was deemed the easiest to use. The nomogram is also low cost, robust, and provides a rapid means of detecting and preventing the large errors that we have shown can occur when an electronic device is used as the primary method of resuscitation fluid calculation. We, therefore, suggest that the nomogram is a suitable method for the calculation of the Parkland formula to guide resuscitation and maintenance fluid requirements in the first 24 h of paediatric burns or for cross-checking the results obtained by other means of calculation.

Comparison of three techniques using the Parkland Formula to aid fluid resuscitation in adult burns

We performed a randomised study to compare the accuracy and speed of three different techniques (pen and paper, electronic calculator and a novel graphic device: 'nomogram') for calculation of resuscitation fluid requirements for adults in the first 24 h of burn injury, based on the Parkland Formula. We also assessed acceptability of each technique using visual analogue scores and qualitative analysis of free text responses. 28 participants performed 252 calculations using a series of computer generated simulated patient data. For nomogram, electronic calculator, pen and paper: Magnitude of error [low (≥25%), medium (≥50%), high (≥75%)]: [6.0%, 1.2%, 0%], [17.9%, 14.3%, 8.3%], [25%, 16.7%, 9.5%]; p<0.002. Calculation time: [sec: mean (SD)]: 94(34), 73(31), 214(103); p<0.001. The mean (SD) of the difficulty scores for each method were 23(17), 17(14) and 70(21) out of 100. Of the 28 participants 15 preferred the calculator, 12 preferred the nomogram and 1 scored the calculator and nomogram equally (table 3). The nomogram was significantly more accurate at all levels, almost as fast as an electronic calculator, and deemed easy to use. It is low cost and robust, and provides a rapid means of detecting and preventing the large errors that we have shown can occur when an electronic device is used as the only method of calculation. We therefore suggest that the Parkland Formula nomogram is a suitable method for calculation of resuscitation fluid requirements in adult burns. Fluid requirement should, however, be reviewed frequently, and adjusted to ensure adequate organ perfusion.

Comparison of cyanide exposure markers in the biofluids of smokers and non-smokers

Cyanide is highly toxic and is present in many foods, combustion products (e.g. cigarette smoke), industrial processes, and has been used as a terrorist weapon. In this study, cyanide and its major metabolites, thiocyanate and 2-amino-2-thiazoline-4-carboxylic acid (ATCA), were analyzed from various human biofluids of smokers (low-level chronic cyanide exposure group) and non-smokers to gain insight into the relationship of these biomarkers to cyanide exposure. The concentrations of each biomarker tested were elevated for smokers in each biofluid. Significant differences (p < 0.05) were found for thiocyanate in plasma and urine, and ATCA showed significant differences in plasma and saliva. Additionally, biomarker concentration ratios, correlations between markers of cyanide exposure, and other statistical methods were performed to better understand the relationship between cyanide and its metabolites. Of the markers studied, the results indicate plasma ATCA, in particular, showed excellent promise as a biomarker for chronic low-level cyanide exposure.

Cyanide: an unreported cause of neurological complications following smoke inhalation

Although the combustion of natural and synthetic products can yield cyanide, its toxic role in residential fires is unclear. This case concerns a woman aged over 50 years who presented comatose, pulseless and apnoeic after a domestic fire. Cardiopulmonary resuscitation and on-site administration of 2.5 g hydroxocobalamin as an antidote to cyanide resulted in a return of spontaneous circulation. On admission to the intensive care unit, the patient was treated with hyperbaric oxygen for suspected carbon monoxide poisoning. In a blood specimen collected at the scene before hydroxocobalamin administration, blood cyanide and carbon monoxide levels were 68 µmol/l and 10.9%. On admission to hospital, plasma lactate was at 4.6 mmol/l. Brain scans revealed lesions which were confirmed 2 months later, consistent with the haemorrhagic necrosis often seen after poisoning by cyanide. These data suggest that smoke inhalation in a residential fire may cause cyanide poisoning. This case provides clinical, biological, analytical and brain imaging data supporting the hypothesis of the toxic role of smoke-induced cyanide poisoning which may result in neurological sequelae.

Rapid point of care analyzer for the measurement of cyanide in blood

A simple, sensitive optical analyzer for the rapid determination of cyanide in blood in point of care applications is described. HCN is liberated by the addition of 20% H(3)PO(4) and is absorbed by a paper filter impregnated with borate-buffered (pH 9.0) hydroxoaquocobinamide (hereinafter called cobinamide). Cobinamide on the filter changes color from orange (λ(max) = 510 nm) to violet (λ(max) = 583 nm) upon reaction with cyanide. This color change is monitored in the transmission mode by a light emitting diode (LED) with a 583 nm emission maximum and a photodiode detector. The observed rate of color change increases 10 times when the cobinamide solution for filter impregnation is prepared in borate-buffer rather than in water. The use of a second LED emitting at 653 nm and alternate pulsing of the LEDs improves the limit of detection by 4 times to ~0.5 μM for a 1 mL blood sample. Blood cyanide levels of imminent concern (≥10 μM) can be accurately measured in ~2 min. The response is proportional to the mass of cyanide in the sample: smaller sample volumes can be successfully used with proportionate change in the concentration LODs. Bubbling air through the blood-acid mixture was found effective for mixing of the acid with the sample and the liberation of HCN. A small amount of ethanol added to the top of the blood was found to be the most effective means to prevent frothing during aeration. The relative standard deviation (RSD) for repetitive determination of blood samples containing 9 μM CN was 1.09% (n = 5). The technique was compared blind with a standard microdiffusion-spectrophotometric method used for the determination of cyanide in rabbit blood. The results showed good correlation (slope 1.05, r(2) 0.9257); independent calibration standards were used.

Noninvasive in vivo monitoring of cyanide toxicity and treatment using diffuse optical spectroscopy in a rabbit model

Currently, no reliable noninvasive methods exist for monitoring the severity of in vivo cyanide (CN) toxicity, treatment, and resulting physiological changes. We developed a broadband diffuse optical spectroscopy (DOS) system to measure bulk tissue absorption and scattering. DOS was used to optically monitor CN toxicity and treatment with sodium nitrite (NaNO2). To perform experiments, the DOS probe was placed on the hind leg of rabbits. A sodium CN solution was infused intravenously. DOS and concurrent physiologic measurements were obtained. After completion of CN infusion, NaNO2 was infused to induce methemoglobinemia (MetHb). During infusion of CN, blood gas measurements showed an increase in venous partial pressure of oxygen (pO2), and following reversal, venous pO2 values decreased. DOS measurements demonstrated corresponding changes in hemoglobin oxygenation states and redox states of cytochrome-c oxidase (CcO) during CN infusion and NaNO2 treatment. Therefore, DOS enables detection and monitoring of CN toxicity and treatment with NaNO2.

Pathophysiology, management and treatment of smoke inhalation injury

Smoke inhalation injury continues to increase morbidity and mortality in burn patients in both the third world and industrialized countries. The lack of uniform criteria for the diagnosis and definition of smoke inhalation injury contributes to the fact that, despite extensive research, mortality rates have changed little in recent decades. The formation of reactive oxygen and nitrogen species, as well as the procoagulant and antifibrinolytic imbalance of alveolar homeostasis, all play a central role in the pathogenesis of smoke inhalation injury. Further hallmarks include massive airway obstruction owing to cast formation, bronchospasm, the increase in bronchial circulation and transvascular fluid flux. Therefore, anticoagulants, antioxidants and bronchodilators, especially when administered as an aerosol, represent the most promising treatment strategies. The purpose of this review article is to provide an overview of the pathophysiological changes, management and treatment options of smoke inhalation injury based on the current literature.

In vitro and in vivo evaluation of various carbonyl compounds against cyanide toxicity with particular reference to alpha-ketoglutaric acid

Cyanide is a rapidly acting neurotoxin that necessitates immediate, vigorous therapy. The commonly used treatment regimen for cyanide includes the intravenous administration of sodium nitrite (SN) and sodium thiosulphate (STS). Due to many limitations of these antidotes, a search for more effective, safer molecules continues. Cyanide is known to react with carbonyl compounds to form the cyanohydrin complex. The present study addresses the efficacy of several carbonyl compounds and their metabolites or nutrients with alpha-ketoglutaric acid (A-KG), citric acid, succinic acid, maleic acid, malic acid, fumaric and oxaloacetic acid, glucose, sucrose, fructose, mannitol, sorbitol, dihydroxyacetone, and glyoxal (5 or 10 mM; -10 min) against toxicity of potassium cyanide (KCN; 10 mM) in rat thymocytes in vitro. Six hours after KCN, cell viability measured by MTT assay and crystal violet dye exclusion revealed maximum cytoprotection by A-KG, followed by oxaloacetic acid. A-KG also resolved the leakage of intracellular lactate dehydrogenase, loss in nuclear integrity (propidium iodide staining), and altered mitochondrial membrane potential (rhodamine 123 assay) as a result of cyanide toxicity. Protection Index (ratio of LD(50) of KCN in protected and unprotected animals; PI) of all the compounds (oral; 1.0 g/kg; -10 min) determined in male mice, revealed that maximum protection was afforded by A-KG (7.6 PI), followed by oxaloacetic acid (6.4 PI). Comparative evaluation of various salts of A-KG alone or with STS (intraperitoneal; 1.0 g/kg; -15 min) showed that maximum protection was conferred by disodium anhydrous salt of A-KG, which also significantly prevented the inhibition of brain cytochrome oxidase caused by 0.75 LD(50) KCN. This study indicates the potential of A-KG as alternative cyanide antidote.

Non-invasive in vivo diffuse optical spectroscopy monitoring of cyanide poisoning in a rabbit model

The objective of this study is to establish a cyanide toxicity animal model and to investigate the ability of broadband diffuse optical spectroscopy (DOS) to non-invasively monitor physiological changes that occur during the development of cyanide toxicity in a rabbit model. Broadband DOS combines multi-frequency frequency-domain photon migration (FDPM) with time-independent near-infrared spectroscopy (NIRS) to quantitatively measure bulk tissue absorption and scattering spectra between 600 nm and 1000 nm. Serum cyanide concentration and arterial and venous blood gas analysis at pre- and post-cyanide infusion were presented. To investigate the ability of DOS to non-invasively monitor physiologic changes occurring during development of CN toxicity, tissue concentrations of deoxyhemoglobin [Hb-R], oxyhemoglobin [Hb-O2], cytochrome c oxidase oxidized state [CcO_Ox] and reduced state [CcO_Re] were determined from absorption spectra acquired in 'real time' during cyanide infusions (NaCN 6 mg/60 ml normal saline) in six pathogen-free New Zealand white rabbits. During cyanide infusion, in vivo tissue oxygen saturation increased ( approximately 10%). In addition, broadband DOS was able to detect a concurrent increase in [CcO_Re] and decrease in [CcO_Ox]. Changes in tissue scattering properties in all six animals were detected during these events, confirming the need for DOS-based methods over traditional NIR spectroscopy to obtain accurate results.

[Treatment strategies for acute smoke inhalation injury]

Most fatalities from fires are not due to burns, but are a result of inhalation of toxic gases produced during combustion. Fire produces a complex toxic environment, involving flame, heat, oxygen depletion, smoke and toxic gases such as carbon monoxide and cyanide. As a wide variety of synthetic materials is used in buildings, such as insulation, furniture, carpeting, electric wiring covering as well as decorative items, the potential for poisoning from inhalation of products of combustion is continuously increasing. The present review describes the pathophysiologic effects from smoke inhalation injury as well as strategies for emergency treatment on scene and in the intensive care setting.

Effect of combined exposure to carbon monoxide and cyanides in selected forensic cases

Carbon monoxide is a toxic gas with potentially lethal action, which forms as a result of incomplete combustion in conditions where there is a lack of oxygen and which, therefore, is present in varying percentages in environments where fire develops. In addition to carbon monoxide, other factors such as cyanide may contribute or might actually be the primary cause of a subject's demise. In cases of exposure to both substances, the role of cyanide as a toxic/lethal agent in death by asphyxiation is still not clear: some authors attribute a primary action to such a gas in causing the demise, others consider carbon monoxide to be the only cause of the lethal event. For this reason it is in the interest of forensic medicine to study all lethal cases of exposure to toxic substances originating from fires of various types of materials, in order to determine information regarding kinetic action and the possible strengthening of the effect of the two substances. Two case studies are presented here, in which the results of the toxicological examinations are quite different, and the contributions of CO and HCN in a fire asphyxiation are considered.

Cyanide poisoning and its treatment

Cyanide is both widely available and easily accessible throughout the world. Although the compound is not frequently encountered, it has been used as a poison and contaminant in the past and is a potential terrorist agent. Cyanide has the ability to cause significant social disruption and demands special attention to public health preparedness. It can be obtained from a variety of sources, including industrial, medical, and even common household products. Another frequently encountered source of cyanide exposure is residential fires. Exposure to high concentrations of the chemical can result in death within seconds to minutes. Long-term effects from cyanide exposure can cause significant morbidity. The only treatment for cyanide toxicity approved for use in the United States is a kit consisting of amyl nitrite, sodium nitrite, and sodium thiosulfate. Future research aims to find a faster-acting, more effective, and better tolerated treatment for cyanide toxicity.

The management of complicated charcoal contact burns involving deep tissues

This report describes the management of a charcoal burn involving deep tissues at different anatomic sites. The closure of burn wounds should be considered as a functional and cosmetic outcome whenever possible. Our aim should be to get the soft tissue of the early burned wound closed. A satisfactory result can be achieved if both the functional anatomy and the aesthetic outcome can be kept in mind while planning the management.

Rapid Cyanide Detection Using the Cyantesmo® Kit

BACKGROUND

Sources of cyanide exposure are many, including combustion of plastic and vinyl, such as in a house fire, laboratory or industrial exposures including exposure in the electroplating industry both of printed circuit boards and in jewelry work. Rapid and definitive diagnosis of cyanide poisoning is unavailable in the emergency department setting. It is desirable to make a definitive diagnosis in order to prevent potential complications of empiric treatment of presumptive cyanide poisoning from the cyanide antidote kit currently approved by the US Food and Drug Administration (FDA). We investigated a technique to detect cyanide currently utilized by water treatment facilities to determine if it can be applied to rapidly detect concentrations of cyanide in the clinically important range.

METHODS

Varying standardized dilutions of KCN ranging from 0.25 microg/mL to 30 microg/mL were acidified with a drop of sulphuric acid in a closed system under a ventilation hood. Cyantesmo test strips were placed into the test tubes above the fluid level where liberated HCN gas interacted with the test strip to effect a color change. Color changes were compared to negative controls and to each other.

RESULTS

The test strips demonstrated an incrementally increasing deep blue color change over a progressively longer portion of the test strip in less than 5 minutes for each concentration of KCN including 1, 3, 10, and 30 microg/mL. The concentrations of 0.25, 0.5, and 0.75 required more than 2 hours to begin demonstration of any color change.

CONCLUSION

The Cyantesmo test strips accurately and rapidly detected, in a semi-quantifiable manner, concentrations of CN greater than 1 microg/mL contained in each test sample. Future work to validate this test in blood and in clinical specimens is planned.

Fluorescence intensity and lifetime-based cyanide sensitive probes for physiological safeguard

We characterize six new fluorescent probes that show both intensity and lifetime changes in the presence of free uncomplexed aqueous cyanide, allowing for fluorescence based cyanide sensing up to physiological safeguard levels, i.e. <30 µM. One of the probes, m-BMQBA, shows a ≈15-fold reduction in intensity and a ≈10% change in mean lifetime at this level. The response of the new probes is based on their ability to bind the cyanide anion through a boronic acid functional group, changing from the neutral form of the boronic acid group R-B(OH)2 to the anionic R-B-(CN)3 form, a new cyanide binding mechanism which we have recently reported. The presence of an electron deficient quaternary heterocyclic nitrogen nucleus, and the electron rich cyanide bound form, provides for the intensity changes observed. We have determined the disassociation constants of the probes to be in the range ≈ 15-84 µM3. In addition we have synthesized control compounds which do not contain the boronic acid moiety, allowing for a rationale of the cyanide responses between the probe isomers to be made. The lifetime of the cyanide bound probes are significantly shorter than the free R-B(OH)2 probe forms, providing for the opportunity of lifetime based cyanide sensing up to physiologically lethal levels. Finally, while fluorescent probes containing the boronic acid moiety have earned a well-deserved reputation for monosaccharide sensing, we show that strong bases such as CN- and OH- preferentially bind as compared to glucose, enabling the potential use of these probes for cyanide safeguard and determination in physiological fluids, especially given that physiologies do not experience any notable changes in pH.

Discharge from the accident and emergency department after smoke inhalation: influence of clinical factors and emergency investigations

OBJECTIVES

Smoke inhalation has become the principal cause of death in burns patients. There are few guidelines for the management of smoke inhalation in the accident and emergency department. The aim was to identify what factors influence immediate management.

METHODS

A retrospective case note review using data from three west of Scotland accident and emergency departments in 1999. Computerized record systems were used to identify suitable patients.

RESULTS

Of 120 patients, 63 patients had incomplete data and were excluded. A total of 57 patients were classified into one of five categories: no burns, normal vital signs and examination (group 1, n=23); no burns, abnormal vital signs or examination (group 2, n=26); minor burns (<15% total body surface area) with or without abnormal vital signs or examination (group 3, n=5); major burns (>15% total body surface area) (group 4, n=2); in cardiac arrest on arrival (group 5, n=1). In groups 1 and 3, the result of two investigations significantly influenced management. In group 2, arterial blood gases and carboxyhaemoglobin levels were abnormal in 25% of cases, but only on one occasion did it influence an admission decision.

CONCLUSION

Arterial blood gases, chest radiography and carboxyhaemoglobin estimation rarely influence immediate management. Patients presenting with normal vital signs and examination and short smoke exposure may be safe to discharge from the accident and emergency department without further investigation.

Biomarkers of exposure to cyanogens in horses with grass sickness

To test the hypothesis that equine grass sickness may be associated with the ingestion of cyanogenic glycosides from white clover (Trifolium repens), the concentrations of whole blood cyanide, and plasma and urinary thiocyanate, the main metabolite of cyanide, were measured in 12 horses with acute grass sickness and 10 horses with subacute grass sickness, and in 43 control horses, of which 21 were co-grazing with cases of acute grass sickness, 12 grazed pastures where grass sickness had not been reported, and 10 were stabled horses. The healthy horses which grazed with cases of acute grass sickness had higher concentrations of blood cyanide, and plasma and urinary thiocyanate than the other control horses, consistent with an increased exposure to cyanogens. The horses with grass sickness had no evidence of a recent intake of cyanogens, but may have been exposed to increased levels of cyanogens before they became anorexic.

Toxicity of fire smoke

This review is an attempt to present and describe the major immediate toxic threats in fire situations. These are carbon monoxide, a multitude of irritating organic chemicals in the smoke, oxygen depletion, and heat. During the past 50 years, synthetic polymers have been introduced in buildings in very large quantities. Many contain nitrogen or halogens, resulting in the release of hydrogen cyanide and inorganic acids in fire smoke as additional toxic threats. An analysis of toxicological findings in fire and nonfire deaths and the results of animal exposures to smoke from a variety of burning materials indicate that carbon monoxide is still likely to be the major toxicant in modern fires. However, the additional toxic threats mentioned above can sometimes be the principal cause of death or their addition can result in much lower than expected carboxyhemoglobin levels in fire victims. This analysis also revealed that hydrogen cyanide is likely to be present in appreciable amounts in the blood of fire victims in modern fires. The mechanisms of action of acute carbon monoxide and hydrogen cyanide poisonings are reviewed, with cases presented to illustrate how each chemical can be a major contributor or how they may interact. Also, lethal levels of carboxyhemoglobin and cyanide in blood are suggested from an analysis of the results of a large number of fire victims from different fire scenarios. The contribution of oxygen depletion and heat stress are more difficult to establish. From the analysis of several fire scenarios, they may play a major role in the room of origin at the beginning of a fire. The results in animal studies indicate that when major oxygen depletion (<10%) is added to lethal or sublethal levels of carbon monoxide or hydrogen cyanide its major role is to substantially reduce the time to death. In these experiments the carboxyhemoglobin level at death was slightly reduced from the expected level with exposure to carbon monoxide alone. However, blood cyanide was reduced by a factor of ten from the expected level with exposure to hydrogen cyanide alone. This is another factor (among many other presented) complicating the task of establishing the contribution of cyanide in the death of fire victims, from its analysis in their blood. Finally the role of ethanol intoxication, as it may influence carboxyhemoglobin levels at death, is reviewed. Its role is minor, if any, but the data available on ethanol in brain tissue and blood of fire victims confirmed that brain ethanol level is an excellent predictor of blood ethanol.

Antagonism of cyanide poisoning by dihydroxyacetone

Dihydroxyacetone (DHA) effectively antagonized the lethal effect of cyanide in mice and rabbits, particularly if administered in combination with thiosulfate. Oral DHA (2 and 4 g/kg) given to mice 10 min before injection (i.p.) of cyanide increased the LD50 values of cyanide from 5.7 mg/kg to 12 and 17.6 mg/kg, respectively. DHA prevented cyanide-induced lethality most effectively, if given orally 10-15 min before injection of cyanide. A combination of pretreatment with oral DHA (4 g/kg) and post-treatment with sodium thiosulfate (1 g/kg) increased the LD50 of cyanide by a factor of 9.9. Furthermore, DHA given intravenously to rabbits 5 min after subcutaneous injection of cyanide increased the LD50 of cyanide from 6 mg/kg to more than 11 mg/kg, while thiosulfate (1 g/kg) given intravenously 5 min after cyanide injection increased the LD50 of cyanide only to 8.5 mg/kg. DHA also prevented the convulsions that occurred after cyanide intoxication.

Breath analysis to detect recent exposure to carbon monoxide

OBJECTIVES

To determine the normal range for carbon monoxide concentrations in the exhaled breath of subjects in the emergency department and to develop a protocol for the use of a breath analyser to detect abnormal carbon monoxide exposure.

METHODS

A hand held breath analyser was used to measure end expiratory carbon monoxide concentrations in 382 consenting subjects. Questionnaire data were collected to assess the effect of common sources of carbon monoxide exposure on breath carbon monoxide levels. Smokers were used as a carbon monoxide exposed group for comparison with non-smokers.

RESULTS

The range of carbon monoxide concentrations obtained in the non-smoking group was 0-6 ppm and in the smoking group was 1-68 ppm. Smokers had a mean breath carbon monoxide concentration of 16.4 ppm and non-smokers had a mean of 1.26 ppm (95% confidence interval (CI) for difference 13.6 to 16.8 ppm). Male sex and frequent motor vehicle use were associated with slightly higher carbon monoxide concentrations (by 0.40, 95% CI 0.18 to 0.63 ppm, and 0.38, 95% CI 0.13 to 0.63 ppm, respectively) in the non-smoking group. Mean breath carbon monoxide concentrations increased in direct proportion to the number of cigarettes smoked (p<0.001) and there was a negative correlation between carbon monoxide and time since last smoking a cigarette (p<0.001). Altogether 23% of smokers had breath carbon monoxide concentrations in the range 1-6 ppm.

CONCLUSIONS

Breath analysis was rapid and results correlated well with carbon monoxide exposure. In this population subjects with breath carbon monoxide concentrations greater than 6 ppm should be assessed for the risk of carbon monoxide poisoning. However even carbon monoxide concentrations less than 6 ppm do not exclude carbon monoxide poisoning within the last 24 hours.

Epidemiology of acute carbon monoxide poisoning in a Spanish region

BACKGROUND

In Spain, as in most of the world, the incidence of acute carbon monoxide poisoning is probably underestimated.

METHODS

During an eighteen-month period we studied, by means of a standardized data collection form, all the cases of acute carbon monoxide poisoning that were diagnosed in 2 university hospitals.

RESULTS

During the study, 154 patients were diagnosed with carbon monoxide poisoning. The mean age was 32.2+/-15.5 years. The two principal exposure sites were the kitchen (43%) and bathroom (23%). The majority of the cases related to malfunction of the water heater (30%) and of the central heating (23%) and 68% occurred in the home. Improper combustion of butane (31%), propane (13%), and natural gas (12%) were most frequent. The most prevalent clinical manifestations were headache (94%), dizziness (56%), nausea (45%), loss of consciousness (38%), and weakness (34%). Five patients died. In 14.4%, symptoms suggested delayed neurological syndrome. The largest number of cases of poisoning occurred during the months of December and January.

CONCLUSIONS

Compared with previous Spanish series or with the antecedent year, acute carbon monoxide poisoning has a high prevalence in our region. Two factors appear to be essential to the accurate diagnosis of acute carbon monoxide poisoning: 1) the ability of emergency room physicians to recognize the clinical symptoms of carbon monoxide poisoning and 2) access to a carbon monoxide-oximeter.

Immunohistochemical investigation of pulmonary surfactant-associated protein A in fire victims

To evaluate the forensic pathological significance of the immunohistochemical distribution of pulmonary surfactant-associated protein A (SP-A) in determining the cause of death in fires, 57 fire victims were examined by scoring the staining intensity. The highest SP-A score with dense granular deposits (aggregates) in the intra-alveolar space was frequently observed in cases with a lower blood carboxyhemoglobin (COHb) level (<60%). The SP-A score was relatively low in carbon monoxide intoxication due to causes other than fires. High SP-A scores showed a relation to the serum level and in part related to the bloody exudate in the lower airway. These observations suggested that the increase in SP-A in fire victims may be mainly related to pulmonary alveolar injury due to the inhalation of hot air and/or irritant gases rather than hypoxia.

Death from thermal effects and burns

One hundred and fifteen unselected autopsy cases of death from thermal effects and/or fire between 1990 and 1999 were analyzed with regard to time of death, signs of vitality at the scene of the fire, the manner and cause of death, and the extent of soft tissue loss. The cases represented approximately 6% of all autopsy cases at the Institute of Legal Medicine responsible for a catchment area with approximately 700,000 inhabitants. In 23 victims suffering burn injuries, death occurred during initial medical care or clinical treatment. The causes of death were primary respiratory arrest due to smoke poisoning or delayed shock caused by thermal injuries to the skin. Death occurred at the scene of the fatal event in 85 cases: eight cases exhibited no thermal effects; the cause of death in one of these cases was polytrauma incurred in a leap from a height; in seven cases there was poisoning due to smoke inhalation. The remaining 77 cases were characterized by signs of intensive thermal and/or fire effects. Clear signs of vitality (carboxyhemoglobin (COHb) in blood, inhalation and/or swallowing of soot) were found in 84.7% of the victims dying at the site of the fatal event. Of the 13 victims showing no signs of vitality at the scene, a cause of death could be determined in only seven cases; death in the other six cases remains unexplained. Quantification of the soft tissue loss revealed a possible correlation with the temperature and time course of heat exposure.

Evaluation of post-mortem oxymetry in fire victims

In order to investigate the pathophysiology of death due to fires, we examined blood samples of 48 fire victims on CO-oximeter systems and evaluated the oxymetric differences between arterial and venous blood as well as those between the heart and peripheral blood. Post-mortem carboxyhemoglobin (CO-Hb) levels in the left and right heart blood, respectively, ranged from 1.2 to 94.7% and from 0.4 to 90.5%. Marked arterio-venous and centro-peripheral differences were observed in the cases of high CO-Hb (above ca. 70%), suggesting an immediate effect of fatal carbon monoxide (CO) poisoning probably accompanied with acute heart failure. A relatively high oxyhemoglobin level was observed in the cases of low CO-Hb (below ca. 30%). In some cases, reduced hemoglobin levels in the left heart blood were paradoxically somewhat higher than those in the right. These oxymetric profiles may assist to consider the final balance of blood gas in fire victims depending on increased CO, carbon dioxide, and reduction of oxygen in the ambient atmosphere due to combustion, although post-mortem interference should be taken into consideration.

Epidemiology of hazardous materials responses by Massachusetts district HAZMAT teams

Hazardous materials releases can cause substantial morbidity and mortality, but very few studies have systemically investigated them. We analyzed responses by Massachusetts' six district hazardous materials (HAZMAT) teams from the time of their inception through February 1994. Spills, leaks, and other escapes of materials caused or contributed to 67 of 85 (79%) incidents. Transportation-related accidents accounted for 13 of 83 (16%), whereas the remainder of the releases occurred at fixed facilities. The chemicals most frequently involved were various hydrocarbons and corrosive materials. Most incidents (60 of 85 [70%]) had no reported injuries. Civilians were injured in 18 of 85 (21%) incidents; regular fire fighter and/or police were injured in eight of 85 (9%) incidents; and HAZMAT team members in one of 85 incidents (1%). Systematic study is needed to identify preventable causes of HAZMAT responses as well as ideas for better control of secondary health effects.

Combined carbon monoxide and cyanide poisoning: a place for treatment

During fires, victims can inhale significant carbon monoxide (CO) and cyanide (CN) gases, which may cause synergistic toxicity in humans. Oxygen therapy is the specific treatment for CO poisoning, but the treatment of CN toxicity is controversial. To examine the indication for treatment of CN toxicity, we have established a canine model to delineate the natural history of combined CO and CN poisoning. In seven dogs (24 +/- 3 kg), CO gas (201 +/- 43 mL) was administered by closed-circuit inhalation. Then, potassium CN was intravenously (i.v.) infused (0.072 mg.kg-1.min-1) for 17.5 +/- 3.0 min. Cardiorespiratory measurements were conducted before and after these toxic challenges. Despite significant CO poisoning (peak carboxyhemoglobin fractions [COHb] = 46% of total hemoglobin [Hb]; elimination t1/2 = 114 +/- 42 min) with attendant decrease in blood O2 content, CO had essentially little effect on any hemodynamic or metabolic variable. On the other hand, CN severely depressed most hemodynamic and metabolic functions. Compared to baseline values, CN caused significant (P < 0.01) decreases in cardiac output (6.4 +/- 2.0 to 3.1 +/- 0.5 L/min) and heart rate (169 +/- 44 to 115 +/- 29 bpm) and decreases in oxygen consumption (VO2) (133 +/- 19 to 69 +/- 21 mL/min) and carbon dioxide production (VCO2) (128 +/- 27 to 103 +/- 22 mL/min). However, these critical hemodynamic and metabolic variables recovered to baseline values by 15 min after stopping the CN infusion, except lactic acidosis which persisted for at least 25 min after the CN infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Warehouse workers' headache: emergency evaluation and management of 30 patients with carbon monoxide poisoning

BACKGROUND

Carbon monoxide (CO) is the leading cause of fatal toxic inhalation in the United States, but the medical literature contains few reports of mass exposures. Warehouse workers' headache (WWH) is an infrequently reported form of CO poisoning due to industrial exposure.

METHODS

We describe 30 persons who developed WWH after inhaling exhaust from a propane-fueled forklift, their emergency medical management at a small community hospital, and their long-term courses.

RESULTS

Workers with more direct exposures to vented exhaust had significantly higher expired CO levels (21.1 +/- 0.7% versus 8.4 +/- 4.8%, P < 0.0001) and higher acute symptom scores (9.0 +/- 2.2 versus 4.7 +/- 3.3, P = 0.01) than persons with less direct exposures. Work location, expired CO levels, and acute symptom scores did not correlate with symptom scores 2 years after exposure. Workers experiencing acute difficulty concentrating or confusion had higher expired CO levels than persons with neither of these symptoms (16.3 +/- 6.7% versus 8.4 +/- 5.2%, P = 0.005) and developed higher chronic symptom scores (3.9 +/- 3.0 versus 1.1 +/- 1.5, P = 0.04), suggesting that this subgroup may require closer follow-up for long-term complications.

CONCLUSION

With earlier recognition of ongoing CO toxicity, this disaster would likely have been averted. Since CO exposures are more common than is often recognized, general internists must be familiar with the manifestations of CO toxicity, its timely evaluation, management, and prevention.

Cyanide and methemoglobin kinetics in smoke inhalation victims treated with the cyanide antidote kit

STUDY OBJECTIVE

To evaluate serial cyanide, methemoglobin, and carbon monoxide levels in smoke inhalation patients.

SETTING

Regional poison center and regional toxicology treatment center.

PARTICIPANTS

Seven critically ill smoke inhalation patients referred to the regional poison center.

INTERVENTIONS

Peak level and half-life were determined by obtaining serial carboxyhemoglobin, cyanide, and methemoglobin levels.

RESULTS

The mean observed half-life of cyanide was 3.0 +/- 0.6 hours. Methemoglobinemia was evaluated in four patients after sodium nitrite administration. The peak measured methemoglobin levels (mean, 10.5% +/- 2%; range, 7.9% to 13.4%) did not occur until a mean of 50 minutes (range, 35 to 70 minutes) following administration of sodium nitrite. The total oxygen-carrying capacity reduced by the combination of carboxyhemoglobin and methemoglobin was never more than 21% (range, 10% to 21%) in this series.

CONCLUSION

The administration of sodium nitrite to smoke inhalation patients in the presence of concomitant carbon monoxide poisoning may be relatively safe.

The effect of dyshemoglobins on pulse oximetry: Part I, Theoretical approach and Part II, Experimental results using an in vitro test system

Pulse oximeters are known to be inaccurate in the presence of elevated concentrations of carboxyhemoglobin and methemoglobin. This paper attempts to alleviate some of the confusion that exists between fractional and functional saturation, and to clarify the comparison of each with SpO2. A series of theoretical relationships between pulse oximeter reading (SpO2) and actual oxygen saturation (both fractional and functional) is derived using simple absorption theory. The theoretical relationships are checked using an experimental in vitro test system. This consists of a blood circuit containing a model finger, capable of simulating the pulsatile transmission signals through a real finger. Theoretical predictions and experimental results are compared and are found to agree well in the presence of carboxyhemoglobin, but less well with methemoglobin. Possible reasons are discussed.