The clinical experience of acute cyanide poisoning

Cyanide Poisoning Compromises Gene Pathways Modulating Cardiac Injury in Vivo

Smoke inhalation from a structure fire is a common route of cyanide poisoning in the U.S. Cyanide inhibits cellular respiration, often leading to death. Its rapid distribution throughout the body can result in injuries to multiple organs, and cyanide victims were reported to experience myocardial infarction and other cardiac complications. However, molecular mechanisms of such complications are yet to be elucidated. While FDA-approved CN antidotes such as sodium thiosulfate and hydroxocobalamin are clinically used, they have foreseeable limitations during mass casualty situations because they require intravenous administration. To facilitate the development of better antidotes and therapeutic treatments, a global view of molecular changes induced by cyanide exposure is necessary. As an exploratory pursuit, we performed oligonucleotide microarrays to establish cardiac transcriptomes of an animal model of nose-only inhalation exposure to hydrogen cyanide (HCN), which is relevant to smoke inhalation. We also profiled cardiac transcriptomes after subcutaneous injection of potassium cyanide (KCN). Although the KCN injection model has often been used to evaluate medical countermeasures, this study demonstrated that cardiac transcriptomes are largely different from that of the HCN inhalation model at multiple time points within 24 h after exposure. Pathway analysis identified that HCN-induced transcriptomes were enriched with genes encoding mediators of pathways critical in modulation of cardiac complications and that a large number of such genes were significantly decreased in expression. We utilized the upstream regulatory analysis to propose drugs that can be potentially employed to treat cyanide-induced cardiac complications.

Cyanogenic glycoside amygdalin influences functions of human osteoblasts in vitro

Amygdalin has been promoted as an alternative cancer cure. However, it is still unclear how this cyanogenic glycoside affects non-cancer cells including bone cells. This study first investigated the impact of amygdalin on viability, morphology and expression of important genes in human osteoblasts in vitro. Primary human osteoblast cultures were exposed to amygdalin at concentrations 0; 0.1; 1 and 10 mg/mL in growth medium for 72 h. Cell viability, osteoblasts morphology and expression of 10 genes associated with osteoblast-specific pathways, oxidative stress and cell death were determined. Osteoblasts viability was significantly decreased (-27.26%) and their size was reduced (-23.20%) at the highest concentration of amygdalin (10 mg/mL). This concentration of amygdalin down-regulated the expression of COL1A1 and ALPL genes, whereas the expression of BGLAP, TNFSF11 and WNT5A genes was increased. The osteoblast cultivation with 0.1 mg/mL amygdalin caused down-regulation of COL1A1 gene. No changes in expression were determined for RUNX2, BAX, CASP1, SOD1 and GPX1 genes among all tested concentrations of amygdalin. In conclusion, amygdalin in a high concentration negatively affected mineralization of extracellular matrix, increased bone resorption and decreased osteoblast viability. These changes were accompanied by modified expression profiles of responsible genes.

Role of Hemodialysis in the Management of Cyanide Intoxication From Apricot Kernels in a 3-Year-Old Child

Cyanide (CN) is one among the most potent and rapidly acting lethal poisons, and it may cause death unless immediately diagnosed and treated. We report an unusual case of pediatric CN poisoning after ingestion of apricot kernels containing amygdalin, who survived with antidotal therapy and hemodialysis. A 3-year-old girl presented with respiratory distress and coma following tonic-clonic convulsions after ingestion of 3 apricot kernels. She had severe metabolic acidosis (pH 6.91, bicarbonate [HCO3] 5.6 mEq/L, base excess -26.0 mEq/L). Her blood CN level was measured 3.15 mg/L, 3 hours after ingestion. Hydroxocobalamin could not be administered immediately because it had to be brought from a medical center 4 hours apart. Therefore, a 3-hour hemodialysis session was carried out, following which she showed some clinical improvement. In addition, when hydroxocobalamin was obtained, it was then administered. During follow-up, she was completely asymptomatic with blood pressure, and other hemodynamic parameters normalized. This case presents hemodialysis as a way to correct metabolic derangements from CN poisoning and suggests that it may have a role in select cases of pediatric CN poisoning, especially when CN-scavenging antidotes may be unavailable.

Case Files of the University of Massachusetts Toxicology Fellowship: Does This Smoke Inhalation Victim Require Treatment with Cyanide Antidote?

Cyanide toxicity is common after significant smoke inhalation. Two cases are presented that provide framework for the discussion of epidemiology, pathogenesis, presenting signs and symptoms, and treatment options of inhalational cyanide poisoning. An evidence-based algorithm is proposed that utilizes point-of-care testing to help physicians identify patients who benefit most from antidotal therapy.

Cyanide: critical issues in diagnosis and treatment

The concern of a terrorist attack using cyanide, as well as the gradual awareness of cyanide poisoning in fire victims, has resulted in a renewed interest in the diagnosis and treatment of cyanide poisoning. The formerly academic presentation of cyanide poisoning must be replaced by more useful knowledge, which will allow emergency physicians and rescue workers to strongly suspect cyanide poisoning at the scene. Human cyanide poisonings may result from exposure to cyanide, its salts, or cyanogenic compounds, while residential fires are the most common condition of exposure. In fire victims, recognition of the cyanide toxidrome has been hampered by the short half-life in blood and poor stability of cyanide. In contrast, carboxyhemoglobin, as a marker of carbon monoxide poisoning, is easily measured and long-lasting. No evidence supports the assumption of the arbitrary fixed lethal thresholds of 50% for carboxyhemoglobin, and 3 mg/L for cyanide, in fire victims. Preliminary data, drawn when comparing pure carbon monoxide and pure cyanide poisonings, suggest that a cyanide toxidrome can be defined considering signs and symptoms induced by cyanide and carbon monoxide, respectively. Prospective studies in fire victims may provide value in clarifying signs and symptoms related to both toxicants. Cyanide can induce a lifethreatening poisoning from which a full recovery is possible. A number of experimentally efficient antidotes to cyanide exist, whose clinical use has been hampered due to serious side effects. The availability of potentially safer antidotes unveils the possibility of their value as first-line treatment, even in a complex clinical situation, where diagnosis is rapid and presumptive.

In vivo studies on hepato-renal impairments in freshwater fish Cyprinus carpio following exposure to sublethal concentrations of sodium cyanide

Reactive oxygen species is an inevitable composite of aerobic systems that could channelize their lethality by imparting oxidative stress under a stressful environment. Cyanide is an important environmental toxicant that could be responsible in the resulting detrimental health issues of aquatic fauna. The present effort investigates the possibilities of hepato-renal damage in freshwater fish Cyprinus carpio following exposure to sublethal concentrations of sodium cyanide (NaCN). Fish were exposed to 0.1 mg/L of NaCN for 10 days (E1) and 20 days (E2) and were further subjected to recovery for 14 days (R) in NaCN-free medium. Liver tissue exhibited a significant decline in activity of catalase, superoxide dismutase, glutathione peroxidase, and glutathione S-transferase enzymes in exposed fish, unlike in control (C). Subsequent levels of lipid peroxidation elevation at 'E1' and 'E2' suggested oxidative damage to hepatocytes. This was further confirmed through a histopathological evaluation which indicated important findings like lymphocytic infiltration and necrosis in liver and tubular and glomerular degeneration in renal organ. The investigation suggests biochemical and histopathological alterations in fish following exposure to NaCN. Nevertheless, fish upon the recovery period were known to exhibit incomplete recuperation which was indicated by partial restoration tendencies under biochemical and histopathological factions. The study clearly implicated the role of NaCN in emphasizing its toxicity to C. carpio, further suggesting lack of recovery transition at a limited tenure of 14 days. The study might contribute in the course of regulatory surveillance and monitoring of aquatic bodies and may also reflect the possibilities of NaCN contamination during aquaculture practices. Graphical Abstract ᅟ.

High Anion Gap Metabolic Acidosis after a Suicide Attempt with Cyanide: The Rebirth of Cyanide Poisoning

A 33-year-old woman was admitted to our emergency department in a state of unconsciousness after attempting suicide with unknown substances. Severe metabolic acidosis (pH: 6.81), with a high anion gap (36.2) and high lactate level (20.2 mmol/L), was observed. After four hours of intensive medical treatment, the patient regained consciousness, with a return of the arterial pH to 7.42. Finally, cyanide intoxication was diagnosed based on the detection of a serum cyanide level of 3.5 mg/L. The presence of a high anion gap associated with severe lactic acidosis is a clue for making a rapid differential diagnosis of acute cyanide intoxication. Providing intensive and immediate supportive management is also crucial, even in cases without obtainable specific antidotes.

Review article: management of cyanide poisoning

Cyanide poisoning is uncommon, but generates interest because of the presumed utility of an antidote immediately available in those areas with a high risk of cyanide exposure. As part of its regular review of guidelines, the Australian Resuscitation Council conducted a systematic review of the human evidence for the use of various proposed cyanide antidotes, and a narrative review of the relevant pharmacological and animal studies. There have been no relevant comparative or placebo-controlled human trials. Nine case series were identified. Treatment with hydroxocobalamin was reported in a total of 361 cases. No serious adverse effects of hydroxocobalamin were reported, and many patients with otherwise presumably fatal poisoning survived. Sodium thiosulphate use was reported in two case series, similarly with no adverse effects. Treatment with a combination of sodium nitrite, amyl nitrite and sodium thiosulphate was reported in 74 patients, with results indistinguishable from those of hydroxocobalamin and sodium thiosulphate. No case series using dicobalt edetate or 4-dimethylaminophenol were identified, but successful use in single cases has been reported. Hydroxocobalamin and sodium thiosulphate differ from alternatives in having negligible adverse effects, and on the basis of current evidence are the antidotes of choice. The indications for the use of an antidote, the requirements for supportive care and a recommended approach for workplaces where there is a risk of cyanide poisoning are presented.

Treatment of neuroterrorism

Bioterrorism is defined as the intentional use of biological, chemical, nuclear, or radiological agents to cause disease, death, or environmental damage. Early recognition of a bioterrorist attack is of utmost importance to minimize casualties and initiate appropriate therapy. The range of agents that could potentially be used as weapons is wide, however, only a few of these agents have all the characteristics making them ideal for that purpose. Many of the chemical and biological weapons can cause neurological symptoms and damage the nervous system in varying degrees. Therefore, preparedness among neurologists is important. The main challenge is to be cognizant of the clinical syndromes and to be able to differentiate diseases caused by bioterrorism from naturally occurring disorders. This review provides an overview of the biological and chemical warfare agents, with a focus on neurological manifestation and an approach to treatment from a perspective of neurological critical care.

A controlled evaluation of case clinical effect coding by poison center specialists for detection of WMD scenarios

BACKGROUND

Many public health entities employ computer-based syndromic surveillance to monitor for aberrations including possible exposures to weapons of mass destruction (WMD). Often, this is done by screening signs and symptoms reported for cases against syndromic definitions. Poison centers (PCs) may offer significant contributions to public health surveillance because of their detailed clinical effect data field coding and real-time data entry. Because improper clinical effect coding may impede syndromic surveillance, it is important to assess this accuracy for PCs.

METHODS

An AAPCC-certified regional PC assessed the accuracy of clinical effect coding by specialists in poison information (SPIs) listening to audio recordings of standard cases. Eighteen different standardized cases were used, consisting of six cyanide, six botulism, and six control cases. Cases were scripted to simulate clinically relevant telephone conversations and converted to audio recordings. Ten SPIs were randomly selected from the center's staff to listen to and code case information from the recorded cases. Kappa scores and the percentage of correctly coding a present clinical effect were calculated for individual clinical effects summed over all test cases along with corresponding 95% confidence intervals. The rate of the case coding by the SPIs triggering the PC's automated botulism and cyanide alerts was also determined.

RESULTS

The kappa scores and the percentage of correctly coding a present clinical effect varied depending on the specific clinical effect, with greater accuracy observed for the clinical effects of vomiting and agitation/irritability, and poor accuracy observed for the clinical effects of visual defect and anion gap increase. Lack of correct coding resulted in only 60 and 86% of the cases that met the botulism and cyanide surveillance definitions, respectively, triggering the corresponding alert. There was no difference observed in the percentage of coding a present clinical effect between certified (9.0 years experience) and non-certified (2.4 years experience) specialists. There were no cases of coding errors that resulted in the triggering of a false positive alert.

CONCLUSION

The success of syndromic surveillance depends on accurate coding of signs and symptoms. Although PCs generally contribute high-quality data to public health surveillance, it is important to recognize this potential weak link in surveillance methods.

Classification tree methods for development of decision rules for botulism and cyanide poisoning

INTRODUCTION

Identification of predictors of potential mass poisonings may increase the speed and accuracy with which patients are recognized, potentially reducing the number ultimately exposed and the degree to which they are affected. This analysis used a decision-tree method to sort such potential predictors.

METHODS

Data from the Toxic Exposure Surveillance System were used to select cyanide and botulism cases from 1993 to 2005 for analysis. Cases of other poisonings from a single poison center were used as controls. After duplication was omitted and removal of cases from the control sample was completed, there remained 1,122 cyanide cases, 262 botulism cases, and 70,804 controls available for both analyses. Classification trees for each poisoning type were constructed, using 131 standardized clinical effects. These decision rules were compared with the current case surveillance definitions of one active poison center and the American Association of Poison Control Centers (AAPCC).

RESULTS

The botulism analysis produced a 4-item decision rule with sensitivity (Se) of 68% and specificity (Sp) of 90%. Use of the single poison center and AAPCC definitions produced Se of 19.5% and 16.8%, and Sp of 99.5% and 83.2%, respectively. The cyanide analysis produced a 9-item decision rule with Se of 74% and Sp of 77%. The single poison center and AAPCC case definitions produced Se of 10.2% and 8.6%, and Sp of 99.8% and 99.8%, respectively.

CONCLUSIONS

These results suggest the possibility of improved poisoning case surveillance sensitivity using classification trees. This method produced substantially higher sensitivities, but not specificities, for both cyanide and botulism. Despite limitations, these results show the potential of a classification-tree approach in the detection of poisoning events.

Recognition of illness associated with covert chemical releases

Public health threats from intentional releases of chemicals into the environment (ie, chemical terrorism) are an increasing concern in the United States. Recent situations of deliberate contamination of food and beverages with chemicals highlight the need for health care providers and public health officials to be alert for adult and pediatric patients in their communities who have signs and symptoms consistent with chemical exposures. In an effort to increase knowledge of surveillance and preparedness for illness related to potential chemical releases, we provide guidance to health care providers and public health personnel for recognizing illnesses or patterns of illnesses that might be associated with the intentional, covert release of chemical agents. In this article, we will discuss 5 examples of outbreaks of illnesses after a covert chemical release, obstacles to recognition of these illnesses, clues (ie, epidemiological patterns and syndromic presentations) that might enhance the recognition of illnesses from a covert chemical release, and public health strategies to enhance the rapid identification of a chemical terrorism event.

Severe cyanide toxicity from ???vitamin supplements???

The use of alternative medicines is increasing and poorly regulated. We describe a case of severe cyanide poisoning arising from amygdalin, a putative vitamin supplement. A 32-year-old woman arrived in the emergency department by ambulance unresponsive, shocked and with fixed dilated pupils. She was hypothermic and tachycardic but was breathing spontaneously. Despite her age, she had documented breast cancer with hepatic metastases. Conventional treatment having failed, she only took 'vitamin supplements' bought on the Internet, her father said. Over the next 6 h she required mechanical ventilation and increasing doses of inotropes. Diabetes insipidus developed. As the appropriateness of further treatment was considered, a relative arrived with her medications including 'vitamin B 17' or amygdalin. An Internet search identified this as a debunked cancer remedy and cyanogen. Serum thiocyanate level was markedly elevated. She recovered fully over 8 h. While various antidotes to cyanide exist, in this case supportive therapy alone proved effective.

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 role of clinical neurophysiology in bioterrorism

Chemical and biological agents have been used as weapons of mass destruction for a long time and presents as a serious threat to mankind. They have been used in many great wars and terrorist attacks with devastating results. The knowledge about these weapons of mass destruction is crucial to health care providers. Early recognition of the clinical characteristics of poisoning as a result of these chemical and biological agents is important to initiate appropriate therapy and minimizing casualties. Neurophysiological investigations when integrated with clinical features are helpful in early identification of some of these agents, especially when serological confirmation is not rapidly available. In this review, we have focused on chemical and biological weapons, which affect the nervous system and the role of clinical neurophysiology in such conditions.

Some histologic and biochemical evidence for mitigation of cyanide-induced tissue lesions by antioxidant vitamin administration in rabbits

The effect of antioxidant vitamins on cyanide-induced tissue damage was investigated in New Zealand White rabbits using a combination of colorimetric, spectrophotometric, enzymatic, gravimetric and histological methods. Three groups of rabbits (six per group) were used in a 4-week feeding experiment. One group received pure grower's mash, while a second group was fed mash containing 400 ppm inorganic cyanide. The third group received daily oral doses of vitamins A, C and E, in addition to mash and 400 ppm cyanide. There were significant decreases (P < 0.05) in activities of superoxide dismutase (SOD), catalase and alkaline phosphatase (AP) in the liver, lung and kidney of the two groups given cyanide, but the decreases were significantly lower (P < 0.05) in the group fed antioxidant vitamins. In addition, the antioxidant vitamin supplementation led to marked reductions in the severity of histopathological degeneration in these tissues. These results strongly suggest that cyanide-induced tissue lesions may be relieved by adequate intake of antioxidant vitamin supplements.

Microbiological, biological, and chemical weapons of warfare and terrorism

Microbiological, biological, and chemical toxins have been employed in warfare and in terrorist attacks. In this era, it is imperative that health care providers are familiar with illnesses caused by these agents. Botulinum toxin produces a descending flaccid paralysis. Staphylococcal enterotoxin B produces a syndrome of fever, nausea, and diarrhea and may produce a pulmonary syndrome if aerosolized. Clostridium perfringens epsilon-toxin could possibly be aerosolized to produce acute pulmonary edema. Ricin intoxication can manifest as gastrointestinal hemorrhage after ingestion, severe muscle necrosis after intramuscular injection, and acute pulmonary disease after inhalation. Nerve agents inhibit acetylcholinesterase and thus produce symptoms of increased cholinergic activity. Ammonia, chlorine, vinyl chloride, phosgene, sulfur dioxide, and nitrogen dioxide, tear gas, and zinc chloride primarily injure the upper respiratory tract and the lungs. Sulfur mustard (and nitrogen mustard) are vesicant and alkylating agents. Cyanide poisoning ranges from sudden-onset headache and drowsiness to severe hypoxemia, cardiovascular collapse, and death. Health care providers should be familiar with the medical consequences of toxin exposure, and understand the pathophysiology and management of resulting illness.

Hydroxocobalamin: improved public health readiness for cyanide disasters

The United States is under the constant threat of a mass casualty cyanide disaster from industrial accidents, hazardous material transportation incidents, and deliberate terrorist attacks. The current readiness for cyanide disaster by the emergency medical system in the United States is abysmal. We, as a nation, are simply not prepared for a significant cyanide-related event. The standard of care for cyanide intoxication is the cyanide antidote kit, which is based on the use of nitrites to induce methemoglobinemia. This kit is both expensive and ill suited for out-of-hospital use. It also has its own inherent toxicity that prevents rapid administration. Furthermore, our hospitals frequently fail to stock this life-saving antidote or decline to stock more than one. Hydroxocobalamin is well recognized as an efficacious, safe, and easily administered cyanide antidote. Because of its extremely low adverse effect profile, it is ideal for out-of-hospital use in suspected cyanide intoxication. To effectively prepare for a cyanide disaster, the United States must investigate, adopt, manufacture, and stockpile hydroxocobalamin to prevent needless morbidity and mortality.

Survival from a lethal blood concentration of cyanide with associated alcohol intoxication

We present a patient with a lethal blood concentration of cyanide. Additionally, he was found to have an alcohol blood level of 270 mg. dl-1, but made a complete recovery following administration of the antidotes dimethylaminophenol and thiosulphate. It is postulated that the patient may have been able to detoxify himself as a result of metabolism of cyanide to the non-toxic form, thiocyanate.

Differential effects of chronic cyanide intoxication on heart, lung and pancreatic tissues

The histotoxic effects of chronic cyanide insult on heart, lung and pancreatic tissues, and some corroborative enzyme and metabolite changes were studied in New Zealand White rabbits using colorimetric, enzymatic and histochemical methods. Two groups of rabbits were fed for 10 months on either pure growers mash or grower mash +702 ppm inorganic cyanide. There were no significant differences in time-course profiles of serum amylase and fasting blood glucose between the cyanide-fed group and control. Pancreatic islet and heart histologies showed no pathological changes, and there were no significant differences in both serum and heart aspartate transaminase activities between the two groups. However, there were significant decreases (P<0.01) in alkaline phosphatase activity in the lungs of the cyanide-fed group, with corresponding significant (P<0.05) increases in the serum activity of the enzyme. Histological examination of lung tissue of the cyanide-treated rabbits revealed focal areas of pulmonary oedema and necrosis. These results suggest the existence of variabilities in tissue susceptibilities to the toxic effect of chronic cyanide exposure. It would appear that chronic cyanide exposure may not predispose to diabetes in the presence of adequate protein intake.

Acute cyanide poisoning: a case report

A case of attempted homicide by cyanide ingestion is reported. The victim, a 19-year-old woman, unknowingly ingested cyanide and presented to the Emergency Department unresponsive, in shock, and in profound metabolic acidosis. The differential diagnosis of this presentation and the patient's successful treatment are reviewed. The important management issues surrounding the treatment of cyanide poisoning are discussed.

Liver and kidney lesions and associated enzyme changes induced in rabbits by chronic cyanide exposure

The effect of prolonged chronic cyanide exposure on liver and kidney integrity, as well as some associated enzyme and metabolite changes, were investigated in New Zealand white rabbits (initial mean weight 1.52 kg) using a combination of colorimetric, spectrophotometric, enzymatic, gravimetric and histological procedures. Two groups of rabbits were fed for 40 weeks on either pure growers' mash or growers' mash containing 702 ppm inorganic cyanide. Results obtained indicate that the cyanide-fed rabbits had significantly decreased liver activities of alkaline phosphatase, glutamate pyruvate transaminase and sorbitol dehydrogenase relative to controls (P<0.05). On the other hand, there were significant increases (P<0.05) in the serum activities of these enzymes in the cyanide-treated group. Kidney alkaline phosphatase activity was significantly decreased (P<0.05), while serum urea and creatinine were significantly higher (P<0.05) in the cyanide group relative to controls. The cyanide treatment led to significant increases in both tissue and serum activities of lactate dehydrogenase. In addition, liver and kidney rhodanese activities were significantly raised in the cyanide-fed group. There were marked degenerative changes in the liver and kidney sections from the cyanide-treated rabbits. These results suggest that chronic cyanide exposure may be deleterious to liver and kidney functions.

Differential effects of cooking in open cups and in sealed cellophane bags on the residual cyanide content of moi-moi, a processed legume product

Bean pastes from the black eyed bean (Vigna unguiculata), pigeon pea (Cajanus cajan) and Ife brown (V. unguiculata) were processed into a popular West African snack moi-moi, cooked in open aluminium cups and in sealed, thin, transparent cellophane bags. The residual total, free and bound cyanide levels of moi-moi from both processes were determined using a combination of enzymatic and colorimetric procedures. Results showed that in all cases, cooking of moi-moi in open aluminium cups caused retention of significantly higher (P<0.05) residual free cyanide than cooking in sealed cellophane bags. Loss of bound cyanide was unaffected by cooking procedure. These results suggest that cooking of moi-moi in cellophane bags reduces the risks of cyanide exposure from legumes.

Effect of potassium cyanide on behaviour and time to death in possums

AIM

To assess the sickness behaviours of possums after eating a lethal dose of potassium cyanide.

METHOD

Spontaneous behaviour and the time to loss of physical responses were examined.

RESULTS

Cyanide ingestion caused a short-lasting period of mild respiratory stimulation. There was no salivation, retching or vomiting. Convulsions occurred in 73% of the possums. After the ingestion of cyanide, the average time to onset of ataxia was 3 minutes, the average time to overall loss of consciousness was 6.5 minutes, and the time to cessation of breathing was 18 minutes.

CONCLUSION

Cyanide is a rapid-acting toxin with few undesirable signs from the welfare perspective.