Influence of blood thiosulfate produced by postmortem changes for the diagnosis of hydrogen sulfide poisoning in forensic autopsy

Background

Thiosulfate concentration in blood is an important indicator for the diagnosis of hydrogen sulfide poisoning. It may also be detected at high levels in postmortem decomposition cases.

Objectives

To determine the effect of postmortem decomposition on blood thiosulfate concentration and define precautions for diagnosing hydrogen sulfide poisoning based on thiosulfate concentration.

Methods

A total of 57 cadavers (37 males and 20 females) of non-hydrogen sulfide poisoning-related deaths that underwent forensic autopsy in our department between 2016 and 2019 were classified into the non-decomposed (19 cases), partially decomposed (19 cases), and severely decomposed (19 cases) groups based on forensic findings. Blood samples collected from each case were analyzed for thiosulfate concentration using liquid chromatography-tandem mass spectrometry.

Results

The mean concentration of thiosulfate detected in the blood was 70.9 (10.5-266.6) μmol/L in the severely decomposed group, 16.3 (0.1-52.7) μmol/L in the partially decomposed group, and 1.1 (0.1-3.6) μmol/L in the non-decomposed group. There was a statistically significant difference between each of the 3 groups (P < 0.01).

Conclusions

Previous studies have reported a blood thiosulfate concentration of >14 μmol/L in hydrogen sulfide poisoning cases and <4 μmol/L in normal cases. Thus, thiosulfate concentration is believed to have a significant impact on the diagnosis of hydrogen sulfide poisoning. This study revealed that postmortem decomposition produced thiosulfate in the blood, and the concentration of thiosulfate was often as high as that observed in cases of hydrogen sulfide poisoning-related death. In addition to cases of advanced decomposition, an increase in thiosulfate concentration was also observed in cases of partial decomposition. Therefore, when measuring thiosulfate concentration as an indicator of hydrogen sulfide poisoning, it is necessary to carefully consider the influence of decomposition.

Fatal poisoning of four workers in a farm: Distribution of hydrogen sulfide and thiosulfate in 10 different biological matrices

We evaluate the distribution of sulfide and thiosulfate (TS) in biological samples of four dairy farmers died inside a pit connected to a manure lagoon. Autopsies were performed 4 days later. Toxicological analyses of sulfide and TS were made using an extractive alkylation technique combined with gas chromatography/mass spectrometry (GC/MS). Autopsies revealed: multiorgan congestion; pulmonary edema; manure inside distal airways of three of the four victims. Sulfide concentrations were cardiac blood: 0.5-3.0 μg/mL, femoral blood: 0.5-1.2 μg/mL, bile: <0.1-2.2 μg/mL; liver 2.8-8.3 μg/g, lung: 5.0-9.4 μg/g, brain: 2.7-13.9 μg/g, spleen: 3.3-6.3 μg/g, fat: <0.1-1.5 μg/g, muscle: 2.6-3.5 μg/g. TS concentrations were cardiac blood: 2.1-4.9 μg/mL, femoral blood: 2.1-2.3 μg/mL, bile: 2.5-4.4 μg/mL, urine: <0.5-1.8 μg/mL; liver <0.5-2.6, lung: 2.8-5.4 μg/g, brain: <0.5-1.9 μg/g, spleen: 1.2-2.9 μg/g, muscle: <0.5-5.6 μg/g. The cause of death was assessed to be acute poisoning by hydrogen sulfide (H₂S) for all the victims. Manure inhalation contributed to the death of three subjects. The measurement of sulfide and TS concentrations in biological samples contributed to better understand the sequence of the events. Subjects 3 provided the highest concentration of sulfide in brain, thus, supporting the hypothesis of a rapid loss of consciousness and respiratory depression. One by one, the other farmers entered the pit in attempts to rescue the coworkers but collapsed. Despite the rapid death, subject 3 was the only one with TS detectable in urine. This could be due to differences in metabolism of H₂S.

Sample preparation method with ultrafiltration for whole blood thiosulfate measurement

Quantitative analysis of thiosulfate is useful for diagnosing hydrogen sulfide poisoning. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) enables more rapid and sensitive measurements than previous methodologies. As simple measurements of blood thiosulfate concentration are affected by the blood matrix, blood is used as the solvent to prepare the standard solution for calibration curve generation. Thus, a large amount of blood devoid of thiosulfate is required. We developed a preparation method by incorporating an ultrafiltration step to overcome this limitation and generate a calibration curve using a standard solution prepared with pure water. We used this improved method to investigate the stability of thiosulfate in refrigerated samples. To compare the effects of refrigeration, blood samples were prepared using the following two methods: one sample was treated with a 50-kDa exclusion ultrafiltration membrane and the other was not treated. The samples were stored at 4 °C, and then measured at 0, 3, 6, 24, 48, and 96 h. The incorporation of the ultrafiltration step in the measurement procedure enabled the quantification of thiosulfate, by plotting a calibration curve using a standard of pure water; it did not require a blood standard. Additionally, the reduction in whole blood thiosulfate concentration was within 10% during 2 days of refrigeration. Thus, the need for a large amount of blood to prepare the standard solution was resolved by the ultrafiltration step in test sample preparation. This method is useful to measure thiosulfate concentration and is not hindered by sample refrigeration for a few days.

Lethal Hydrogen Sulfide poisoning in open space: An atypical case of asphyxiation of two workers

Hydrogen sulfide is one of the most dangerous toxic gases that has led to the deaths in confined spaces of many workers. We report an atypical case of a fatal accident of H₂S poisoning in an open space when two workers died during the opening of a hatch on a tanker truck filled with leachate water. Despite being outdoors, the two workers, were suddenly and quickly overwhelmed by a lethal cloud of H₂S, which escaped like a geyser from the hatch and hovered over the top of the tanker making it impossible for them to survive. The first operator was engulfed by the sudden flow of lethal gas near the hatch while the second worker, who came to his aid, immediately lost consciousness and fell off the tanker onto the ground. Environmental toxicological analyses were carried out on the air near the hatch and inside the tanker 2h, 20 days and 70 days after the accident. Toxicological analyses on the blood were also carried out but unfortunately, no urine sample was available. The thiosulfate, detected by GC/MS analysis after derivatization of PFBBr, was found to be 0.01 and 0.04mM/L. These values are included in the medium-low lethal values of occupational fatalities involving H₂S reported in the literature.

Toxicological investigations in a fatal and non-fatal accident due to hydrogen sulphide (H2S) poisoning

Hydrogen sulphide (H₂S) is one of the most toxic natural gas and represents a not rare cause of fatal events in workplaces. We report here a serious accidental poisoning by hydrogen sulphide inhalation involving six sailors. Three of them died while the other three survived and were transported to the emergency room. No greenish discolouration of the body, that could be a feature of these type of deaths, was observed at autopsy. Given that blood and/or urine H₂S detection does not allow to discriminate if it is related to inhalation or to putrefactive processes, the determination of thiosulphate, H₂S main metabolite, is decisive. The succession of fatal events reported here can be rebuilt by toxicological data interpretation: the subject 1 died after a longer interval of time as demonstrated by the highest blood and urine thiosulfate concentrations; the subject 2 died after a short interval of time as showed by a lower blood and urine thiosulfate concentrations than subject 1; the subject 3 died almost immediately after H₂S inhalation since he showed the lowest blood thiosulfate concentration, and no trace of sulphide and thiosulfate was found in the urine.

Novel Composite Electrodes for Selective Removal of Sulfate by the Capacitive Deionization Process

Capacitive deionization (CDI) can remove ionic contaminants from water. However, concentrations of background ions in water are usually much higher than target contaminants, and existing CDI electrodes have no designed selectivity toward specific contaminants. In this study, we demonstrate a selective CDI process tailored for removal of SO₄^2- using activated carbon electrodes modified with a thin, quaternary amine functionalized poly(vinyl alcohol) (QPVA) coating containing submicron sized sulfate selective ion exchange resin particles. The resin/QPVA coating exhibited strong selectivity for SO₄^2- at Cl^-: SO₄^2- concentration ratios up to 20:1 by enabling preferential transport of SO₄^2- through the coating, but had no negative impact on the electrosorption kinetics when the coating thickness was small. The cationic nature of the coating also significantly improved the charge efficiency and consequently the total salt adsorption capacity of the electrode by 42%. The resin/QPVA coated CDI system was stable, showing highly reproducible performance in more than 50 adsorption and desorption cycles. This work suggests that addition of selective ion exchange resins on the surface of a carbon electrode could be a generally applicable approach to achieve selective removal of target ions in a CDI process.

Liquid chromatography-tandem mass spectrometry method for the determination of thiosulfate in human blood and urine as an indicator of hydrogen sulfide poisoning

Being a stable metabolite of hydrogen sulfide, thiosulfate has been utilized as an index for hydrogen sulfide poisoning (HSP). Thiosulfate analysis is mainly performed using gas chromatography/mass spectrometry (GC-MS) due to its high sensitivity and specificity. The GC-MS analysis requires two-step derivatizations of thiosulfate, and the derivative is not stable in solution as it has a disulfide moiety. To resolve this stability issue, we developed a novel analytical method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for monitoring the pentafluorobenzyl derivative of thiosulfate (the first reaction product of the GC-MS method) in this study. The established method exhibited high reproducibility despite being a more simplified and rapid procedure compare to the GC-MS method. Phenyl 4-hydroxybenzoate was used as an internal standard because 1,3,5-tribromobenzene which had been used in the GC-MS method was not suitable compound for LC-MS/MS with Electrospray ionization (ESI) negative detection. The linear regression of the peak area ratios versus concentrations was fitted over the concentration ranges of 0.5-250μM and 0.25-250μM in blood and urine, respectively. The validation results satisfied the acceptance criteria for intra- and inter-day accuracy and precision. Blood and urine samples from 12 suspected HSP cases were tested using this method. The thiosulfate concentration detected in the sample coincided well with that determined at the scene of each HSP accident.

Development for the measurement of serum thiosulfate using LC-MS/MS in forensic diagnosis of H2S poisoning

Thiosulfate measurement is crucial to diagnosis of hydrogen sulfide (H2S) poisoning in forensic toxicology. Although GC-MS method is currently regarded as a standard thiosulfate measurement, it requires complicated sample preparation prior to analysis. This study presents a simple, rapid, and highly sensitive method for the quantitative analysis of serum thiosulfate by using liquid chromatography-tandem mass spectrometry (LC-MS/MS). This method is based on selected reaction monitoring and has high sensitivity with a lower quantification limit of 0.5μM. Precision and accuracy of this method meet the basic requirements for quantitative analysis (intra- and inter-day tests have a relative standard deviation of ⩽10.4%; range of analytical recovery is 94.3-102.6%). On the measurements of serum thiosulfate by our developed method, a thiosulfate concentration as 57.5μM was detected clearly in the H2S poisoning case comparing to the non poisoning case in which only a trace amount of thiosulfate was observed.

A fatal work-related poisoning by hydrogen sulfide: report on a case

Hydrogen sulfide (H2S) is a colorless and potentially deadly gas that may cause rapid loss of consciousness and respiratory depression without warning. Although occupational exposure to H2S and the medical management of H2S-associated toxicity are widely established, it remains a problem in the sour gas industry and in other industrial settings, predominantly in new workers. In this article, the authors report a fatal case of a factory worker who died after breathing in H2S while undertaking a task that he was not trained to perform. Toxicological assessment supported by autopsy findings and circumstantial data was essential to clarify the cause of death, determined as H2S poisoning. This case emphasizes the need to develop work safety initiatives, improve on-the-job training, and introduce more consciousness to put on protective equipment for workers; indeed, correct training and education for workers regarding safety in the workplace may help to reduce worker fatalities.

Toxicological analysis of 17 autopsy cases of hydrogen sulfide poisoning resulting from the inhalation of intentionally generated hydrogen sulfide gas

Although many cases of fatal hydrogen sulfide poisoning have been reported, in most of these cases, it resulted from the accidental inhalation of hydrogen sulfide gas. In recent years, we experienced 17 autopsy cases of fatal hydrogen sulfide poisoning due to the inhalation of intentionally generated hydrogen sulfide gas. In this study, the concentrations of sulfide and thiosulfate in blood, urine, cerebrospinal fluid and pleural effusion were examined using GC/MS. The sulfide concentrations were blood: 0.11-31.84, urine: 0.01-1.28, cerebrospinal fluid: 0.02-1.59 and pleural effusion: 2.00-8.59 (μg/ml), while the thiosulfate concentrations were blood: 0-0.648, urine: 0-2.669, cerebrospinal fluid: 0.004-0.314 and pleural effusion: 0.019-0.140 (μmol/ml). In previous reports, the blood concentration of thiosulfate was said to be higher than that of sulfide in hydrogen sulfide poisoning cases, although the latter was higher than the former in 8 of the 14 cases examined in this study. These results are believed to be strongly influenced by the atmospheric concentration of hydrogen sulfide the victims were exposed to and the time interval between exposure and death.

Health hazards from volcanic gases: a systematic literature review

Millions of people are potentially exposed to volcanic gases worldwide, and exposures may differ from those in anthropogenic air pollution. A systematic literature review found few primary studies relating to health hazards of volcanic gases. SO2 and acid aerosols from eruptions and degassing events were associated with respiratory morbidity and mortality but not childhood asthma prevalence or lung function decrements. Accumulations of H2S and CO2 from volcanic and geothermal sources have caused fatalities from asphyxiation. Chronic exposure to H2S in geothermal areas was associated with increases in nervous system and respiratory diseases. Some impacts were on a large scale, affecting several countries (e.g., Laki fissure eruption in Iceland in 1783-4). No studies on health effects of volcanic releases of halogen gases or metal vapors were located. More high quality collaborative studies involving volcanologists and epidemiologists are recommended.

Fatal hydrogen sulfide poisoning at a dye works

An adult Japanese man (A) entered a pit to remove sludge in a drainage pipe at a dye works in Japan. When he took off a joint of the pipe, the sludge in the pipe flowed into the pit. As he suddenly lost consciousness, three colleagues (B, C, D) entered the pit to rescue him. All of these (A, B, C and D) lost consciousness in the pit, and died soon after the accident. Since hydrogen sulfide gas was detected in the sludge of the pit, gas poisoning was suspected. Toxicological analyses of sulfide and thiosulfate, a metabolite of sulfide, in blood and urine of the victims were made, using the extractive alkylation technique combined with gas chromatography/mass spectrometry. Sulfide and thiosulfate were detected in whole blood of the four workers at levels of 0.32-9.36 mg/l and 0.11-0.23 mmol/l, respectively. These concentrations were at least 6-187 times higher in sulfide and 37-77 times higher in thiosulfate than those in healthy persons, and were similar to values found in fatal cases of hydrogen sulfide poisoning. Thiosulfate was not detected in the urine of four workers, which indicated acute death. Based on these results, all four patients were victims of hydrogen sulfide poisoning, who died soon after the exposure.

Twenty-foot fall averts fatality from massive hydrogen sulfide exposure

Hydrogen sulfide is a colorless irritant and asphyxiant gas with a noxious odor of "rotten eggs." Acute hydrogen sulfide exposure may cause, depending on the level and duration of toxicity, symptoms ranging from mild mucous membrane irritation to permanent neurologic impairment and cardiopulmonary arrest. We present a case of an oil refinery worker exposed to a typically fatal concentration of hydrogen sulfide gas (>1000 ppm) while working on top of a 20-foot ladder. The "knockdown" effect of exposure to high concentrations of hydrogen sulfide caused him to lose consciousness and fall from the top of the ladder. He was transported to the Emergency Department as a major trauma victim. Ironically, this 20-foot fall saved his life and possibly those of the rescuers by immediately removing him from the source of the hydrogen sulfide. Treatment of hazardous materials incidents and the pathophysiology and treatment options for hydrogen sulfide poisoning are discussed.