Asphyxia due to oxygen deficiency by gaseous substances

Tracheal injury diagnosed by a sudden increase in end-tidal carbon dioxide levels during mediastinoscopic subtotal esophagectomy: a case report

BACKGROUND

Mediastinoscopic surgery for esophageal cancer facilitates early postoperative recovery. However, it can occasionally cause serious complications. Here, we present the case of a patient with a tracheal injury diagnosed by a sudden increase in end-tidal carbon dioxide (EtCO2) during mediastinoscopic subtotal esophagectomy.

CASE PRESENTATION

A 52-year-old man diagnosed with esophageal cancer was scheduled to undergo mediastinoscopic subtotal esophagectomy. During the mediastinoscopic procedure, the EtCO2 level suddenly increased above 200 mmHg, and the blood pressure dropped below 80 mmHg. We immediately asked the operator to stop insufflation and found a tracheal injury on the right side of the trachea near the carina by bronchoscopy. The endotracheal tube was replaced with a double-lumen tube, and the trachea was repaired via right thoracotomy. There were no further intraoperative complications. After surgery, the patient was extubated and admitted to the intensive care unit.

CONCLUSIONS

Monitoring EtCO2 levels and close communication with the operator is important for safely managing sudden tracheal injury during mediastinoscopic esophagectomy.

Suicide by Gaseous Displacement of Atmospheric Oxygen With Carbon Dioxide From Dry Ice Sublimation

ABSTRACT

Deaths from gaseous substances can occur from exposure to toxic gases or from accumulation of nontoxic gases that displace oxygen. We present a 38-year-old man with no known medical history, who was found deceased in a small bathroom with blankets and towels shoved under the door from the inside.At autopsy, the decedent was found to be in a moderate state of decomposition. There was mild pulmonary congestion, with no other significant findings. Standard postmortem toxicology on femoral blood was noncontributory.A search of the decedent's cell phone revealed statements and internet searches regarding carbon dioxide (CO 2 ) and asphyxia using dry ice. A journal entry also outlined a suicide plan using large amounts of dry ice, which was enacted by placing a laundry basket of dry ice into a bathtub containing water. Based on the investigation, the cause of death was determined to be asphyxia from displacement of oxygen with CO 2 .Dry ice sublimates into gaseous CO 2 , which quickly accumulates, with concentrations of 10% or more, rapidly becoming life-threatening. There are no pathognomonic autopsy findings seen in CO 2 -related asphyxia. In these circumstances, scene investigation is the most important factor in determining cause of death.

Bioactivity of Inhaled Methane and Interactions With Other Biological Gases

A number of studies have demonstrated explicit bioactivity for exogenous methane (CH₄), even though it is conventionally considered as physiologically inert. Other reports cited in this review have demonstrated that inhaled, normoxic air-CH₄ mixtures can modulate the in vivo pathways involved in oxidative and nitrosative stress responses and key events of mitochondrial respiration and apoptosis. The overview is divided into two parts, the first being devoted to a brief review of the effects of biologically important gases in the context of hypoxia, while the second part deals with CH₄ bioactivity. Finally, the consequence of exogenous, normoxic CH₄ administration is discussed under experimental hypoxia- or ischaemia-linked conditions and in interactions between CH₄ and other biological gases, with a special emphasis on its versatile effects demonstrated in pulmonary pathologies.

Fentanyl causes naloxone-resistant vocal cord closure: A platform for testing opioid overdose treatments

BACKGROUND

High doses of the synthetic opioid fentanyl cause rapid and sustained vocal cord closure (VCC) leading to airway obstruction that prevents overdose victims from breathing. This airway effect is not caused by morphine-derived opiates (e.g. heroin), is distinct from respiratory depression, resistant to naloxone, and can be lethal. However, VCC has not been previously included in animal models of opioid overdose.

METHODS

Video laryngoscopy was used to monitor vocal cord movement in anesthetized Sprague-Dawley rats. Rats were administered saline, fentanyl (5, 25, or 50 μg/kg) or morphine (5 mg/kg) in an intravenous (IV) bolus delivered over a 10 s period. The mu opioid receptor (MOR) antagonist naloxone was administered as a pre-treatment (1 mg/kg, IV) 5 min prior to fentanyl (25 μg/kg) or a post-treatment (1 and 2 mg/kg) 1 min after fentanyl (25 μg/kg).

RESULTS

Fentanyl (25 and 50 μg/kg) caused sustained and lethal VCC within 10 s. Morphine (5 mg/kg) and fentanyl (5 μg/kg) caused only brief laryngospasm with full recovery. Pre-treatment with naloxone (1 mg/kg) prevented fentanyl-induced VCC, but naloxone (1 and 2 mg/kg) was unable to reverse VCC when administered after fentanyl.

CONCLUSIONS

These results indicate sustained VCC is a lethal physiological reaction, specific to fentanyl and resistant to naloxone treatment. While pre-treatment with naloxone prevented fentanyl-induced VCC, naloxone was unable to reverse the effect, suggesting a non-opioid receptor-mediated mechanism. These findings demonstrate the necessity of VCC inclusion in animal models of synthetic opioid overdose and the urgent need for more effective treatments for fentanyl-related overdoses.

Lethal physiological effects of carbon dioxide exposure at high concentration in rats

The acute toxicity of high concentrations of carbon dioxide (CO₂) was investigated in anesthetized rats using physiological parameters. At an oxygen concentration of 21%, the survival time decreased in a concentration-dependent manner from ≥7.3 h at 20% CO₂ to 1.0 h at 50% CO₂. The animals were divided into groups that were exposed to 40% CO₂ and 21% O₂ balanced with nitrogen (CO₂ group), 40% CO₂ and 12.6% O₂ (CO₂-Hypoxia group), 0% CO₂ and 12.6% O₂ (Hypoxia group), and 0% CO₂ and 21% O₂ (Control group) for 3 h. In the CO₂ group, mean blood pressure (MBP) increased temporarily in the first 60 min followed by a gradual decrease, while breathing rate (BR) decreased immediately up to 3 h and the concentration of serum indicators reflecting organ damage increased. Most of these effects progressed in the CO₂-Hypoxia group. The Hypoxia group showed a contrasting response to the CO₂ groups in MBP and BR, and a slight partial increase in the serum indicators. Histological changes were not observed in any primary organs of any group, except for eosinophilic or necrosis of pyramidal cells in the hippocampal CA1 region of the CO₂ group. These results indicate that high concentrations of CO₂ inhalation are toxic, likely due to BR suppression, and that hypoxia produced under a high CO₂ environment, while showing little effect on its own, enhances the toxic effects of CO₂.

Prehospital characteristics, incidence trends, and outcome of emergency self-inflicted injury patients with gas substances: a population-based descriptive study in Osaka, Japan

Aim

Little is known about the detailed characteristics of patients using gas substances for self‐inflicted injury in prehospital settings. The aim of this study was to investigate the characteristics, incidence trends, and outcomes of patients who used gas substances for self‐inflicted injury in Osaka City, Japan, using ambulance records.

Methods

This was a retrospective observational study that used data from 2009 to 2015. We extracted details from ambulance records of self‐inflicted injury patients who used gas substances. The annual incidence of self‐inflicted injury by gas substance and age group and Poisson regression models were applied for calculating the annual incidence trend by type of gas substance. The main outcome was confirmed death at the scene, and we also calculated the crude odds ratios and 95% confidence intervals for each gas substance.

Results

During the study period, there were 324 self‐inflicted injury patients who used gas substances. The most commonly used gases were carbon monoxide (CO) (54.9%), followed by hydrogen sulfide (12.7%), helium (6.5%). The incidence of CO and hydrogen sulfide have subsequently decreased (P for trend = 0.023 and <0.001, respectively); however, the incidence of helium did not change during the study period (P for trend = 0.586). The mortality rate was highest in patients who used helium (66.7% [14/21]) and the crude odds ratio of helium was 3.857 (95% confidence interval, 1.267–11.745; P = 0.017) compared with hydrogen sulfide.

Conclusion

This study revealed that the incidence of self‐inflicted injury with helium did not change and its proportion of death at the scene was high in Osaka City.

Methane ameliorates spinal cord ischemia-reperfusion injury in rats: Antioxidant, anti-inflammatory and anti-apoptotic activity mediated by Nrf2 activation

Methane is reported to have antioxidant, anti-inflammatory and anti-apoptotic properties. We investigated the potential neuroprotective effects of methane-rich saline (MS) on spinal cord ischemia-reperfusion injury and determined that its therapeutic benefits are associated with the activation of nuclear factor erythroid 2-related factor 2 (Nrf2). Rats received 9min of spinal cord ischemia induced by occlusion of the descending thoracic aorta plus systemic hypotension followed by a single MS treatment (10ml/kg, ip) and 72h reperfusion. MS treatment attenuated motor sensory deficits and produced high concentrations of methane in spinal cords during reperfusion, which increased Nrf2 expression and transcriptional activity in neurons, microglia and astrocytes in the ventral, intermediate and dorsal gray matter of lumbar segments. Heme oxygenase-1, superoxide dismutase, catalase and glutathione were upregulated; and glutathione disulfide, superoxide, hydrogen peroxide, malondialdehyde, 8-hydroxy-2-deoxyguanosine and 3-nitrotyrosine were downregulated in MS-treated spinal cords. MS treatment reduced neuronal apoptosis in gray matter zones, which was consistent with the suppression of cytochrome c release to the cytosol from the mitochondria and the activation of caspase-9 and -3. Throughout the gray matter, the activation of microglia and astrocytes was inhibited; the nuclear accumulation of phosphorylated nuclear factor-kappa B p65 was reduced; and tumor necrosis factor α, interleukin 1β, chemokine (C-X-C motif) ligand 1, intercellular adhesion molecule 1 and myeloperoxidase were decreased. MS treatment attenuated blood-spinal cord barrier dysfunction by preventing the expression and activity of matrix metallopeptidase-9 and disrupting tight junction proteins. Consecutive intrathecal injection of specific siRNAs targeting Nrf2 at 24-h intervals 3 days before ischemia reduced the beneficial effects of MS. Our data indicate that MS treatment prevents IR-induced spinal cord damage via antioxidant, anti-inflammatory and anti-apoptotic activities that involve the activation of Nrf2 signaling. Thus, methane may serve as a novel promising therapeutic agent for treating ischemic spinal cord injury.

Suicidal nitrogen inhalation by use of scuba full-face diving mask

A 29-year-old man was found dead lying on the bed in a hotel room in a famous Slovak mountain resort. He had a full-face diving mask on his face, connected through a diving breath regulator to a valve of an industrial (nondiving) high-pressure tank containing pure 100% nitrogen. The breath regulator (open-circuit type) used allowed inhalation of nitrogen without addition of open air, and the full-face diving mask assured aspiration of the gas even during the time of unconsciousness. At autopsy, we found the typical signs of suffocation. Toxicological analysis revealed 94.7% content of nitrogen in alveolar air. Following the completion of the police investigation, the manner of death was classified as a suicide. Within the medico-legal literature, there has been only one similar case of suicidal nitrogen inhalation described.

The anti-inflammatory effects of methane

OBJECTIVE

Gastrointestinal methane generation has been demonstrated in various stress conditions, but it is not known whether nonasphyxiating amounts have any impact on the mammalian pathophysiology. We set out to characterize the effects of exogenous methane administration on the process of inflammatory events arising after reoxygenation in a large animal model of ischemia-reperfusion.

DESIGN

A randomized, controlled in vivo animal study.

SETTING

A university research laboratory.

SUBJECTS

Inbred beagle dogs (12.7 6 2 kg).

INTERVENTIONS

Sodium pentobarbital-anesthetized animals were randomly assigned to sham-operated or ischemia-reperfusion groups, where superior mesenteric artery occlusion was maintained for 1 hr and the subsequent reperfusion was monitored for 3 hrs. For 5 mins before reperfusion, the animals were mechanically ventilated with normoxic artificial air with or without 2.5% methane. Biological responses to methane-oxygen respirations were defined in pilot rat studies and assay systems were used with xanthine oxidase and activated canine granulocytes to test the in vitro bioactivity potential of different gas concentrations.

MEASUREMENTS AND MAIN RESULTS

The macrohemodynamics and small intestinal pCO(2) gap changes were recorded and peripheral blood samples were taken for plasma nitrite/nitrate and myeloperoxidase analyses. Tissue superoxide and nitrotyrosine levels and myeloperoxidase activity changes were determined in intestinal biopsy samples; structural mucosal damage was measured by hematoxylin and eosin staining. Methane inhalation did not influence the macrohemodynamics but significantly reduced the magnitude of the tissue damage and the intestinal pCO(2) gap changes after reperfusion. Furthermore, the plasma and mucosal myeloperoxidase activity and the intestinal superoxide and nitrotyrosine levels were reduced, whereas the plasma nitrite/nitrate concentrations were increased. Additionally, methane effectively and specifically inhibited leukocyte activation in vitro.

CONCLUSIONS

These data demonstrate the anti-inflammatory profile of methane. The study provides evidence that exogenous methane modulates leukocyte activation and affects key events of ischemia-reperfusion-induced oxidative and nitrosative stress and is therefore of potential therapeutic interest in inflammatory pathologies.

Asphyxia Due to Accidental Nitrogen Gas Inhalation: A Case Report

Intoxications resulting from asphyxiate gases, such as nitrogen can cause hypoxia and even death. We present a case of a patient with nitrogen intoxication due to inadvertent industrial exposure. In this case, the patient survived and the outcome was different from those reported in the literature. For patients presenting to the emergency department from a workplace with a history of loss of consciousness after using of self-contained breathing apparatus, possibility of nitrogen or other simple asphyxiate gas intoxication should be considered seriously.

Deaths involving natural gas inhalation

Death due to gas inhalation is accidental or suicidal. Natural gas can be a cause of death as a result of oxygen replacement in the atmosphere. Three male victims who were killed from gas inhalation are described in this study. One 19-year-old man attempted suicide using a combination of plastic bag suffocation and natural gas tube in his mouth. The other victim (24 years old man) attempted suicide by natural gas inhalation, and the cause of death of the third victim was inhalation of the vapor from a furnace that contained crude oil or gasoline. Methanol was detected in blood and liver samples by headspace gas chromatography (HSGC) and headspace gas chromatography-mass spectrometry (HSGCMS). Carboxyhemoglobin (CO-Hb) and other drugs and poisons were not detected in blood and liver samples.

Deaths involving natural gas inhalation

Death due to gas inhalation is accidental or suicidal. Natural gas can be a cause of death as a result of oxygen replacement in the atmosphere. Three male victims who were killed from gas inhalation are described in this study. One 19-year-old man attempted suicide using a combination of plastic bag suffocation and natural gas tube in his mouth. The other victim (24 years old man) attempted suicide by natural gas inhalation, and the cause of death of the third victim was inhalation of the vapor from a furnace that contained crude oil or gasoline. Methanol was detected in blood and liver samples by headspace gas chromatography (HSGC) and headspace gas chromatography-mass spectrometry (HSGCMS). Carboxyhemoglobin (CO-Hb) and other drugs and poisons were not detected in blood and liver samples.

Temporal trends over the past two decades in asphyxial deaths in South Australia involving plastic bags or wrapping

Asphyxial deaths utilising plastic bags or wrappings occurring over a 20-year period from March 1984 to February 2004 were reviewed at Forensic Science SA, Australia. A total of 45 cases were identified, with three occurring in infants and children (one accidental asphyxia; two homicides). Of the remaining 42 adults the male to female ratio was approximately 1:1 (23 and 19 cases, respectively), with all deaths attributed to suicide. The 42 adult cases represented 1.2% of the 3569 suicides autopsied at the centre over the time period of the study. The age ranges of the adult victims were 19-88 years (mean=47.1 years) for the males, and 32-89 years (mean=60.5 years) for the females. The adult female victims were significantly older than the males (p<0.001). A number of victims had histories of depression and had taken prescription medications. A significant difference was found in the temporal occurrence of the adult deaths, with six cases occurring between 1984 and 1989, nine between 1989 and 1994, 11 between 1994 and 1999, and 16 between 1999 and 2004 (p<0.001). Plastic bag asphyxial deaths were rare and in adults were due to suicide involving either older females or younger males. A significant increase in cases in South Australia in recent years was demonstrated, possibly related to publicity surrounding assisted suicides, and the ready availability of suicide manuals and information on suicide techniques from the internet.

Plastic bag asphyxia in southeast Scotland

Death resulting from plastic bag asphyxia has been recognized for >40 years, but relatively little is known about either its epidemiology or its pathophysiology. Over 15 years (1984-1998), 30 deaths were attributed to plastic bag asphyxia among the 14,560 autopsies performed in the Forensic Medicine Unit in Edinburgh. These 30 deaths involved 20 male and 10 female subjects, with an age range of 13 to 81 years. Eleven had some alcohol measurable in the blood, with four having levels >80 mg/dl. Only one individual appeared to have ingested a drug overdose, but inhaled substances within the plastic bag may have contributed to death in five cases. The absence of childhood accidental deaths may reflect successful preventive measures. The 3 accidental deaths involved adults (including 2 who died of autoerotic asphyxia), and the remaining deaths were 27 suicides. Of those who committed suicide, most (59%) had chronic psychiatric illness rather than chronic debilitating or terminal physical illness. In contrast with reports from the United States, publicity associated with "self-deliverance" did not result in an increased number of deaths from plastic bag asphyxia (4 deaths in this series). Analysis of the circumstances of all the deaths revealed them to be difficult to predict and hence prevent.