Cyanide poisoning treated with hyperbaric oxygen

Amygdalin - A pharmacological and toxicological review

ETHNOPHARMACOLOGICAL RELEVANCE

Amygdalin is commonly distributed in plants of the Rosaceae, such as peach, plum, loquat, apple and bayberry, but most notably in the seeds (kernels) of apricot almonds. As a naturally aromatic cyanogenic compound, it has long been used in Asia, Europe and other regions for the treatment of various diseases including cough, asthma, nausea, leprosy and leukoderma. Importantly, in recent years, an increasing attention has been paid to its antitumor effect.

AIM OF THE STUDY

The paper aims to review the pharmacological activities and toxicological effects of amygdalin and provide a reference and perspective for its further investigation.

METHODS

Electronic databases including the Web of Science, Cochrane Library, PubMed, EMBASE, the Chinese Biological Medicine Database, China National Knowledge Infrastructure, Wanfang database and VIP information database were searched up to November 2019 to identify eligible studies. A meticulous review was performed, an in-depth analysis on the pharmacological activity and toxicology of amygdalin was conducted, and perspectives for future research were also discussed.

RESULTS

A total of 110 papers about in vitro/in vivo studies on amygdalin have been reviewed. Analysis on the data suggested that this compound presented pharmacological activities of anti-tumor, anti-fibrotic, anti-inflammatory, analgesic, immunomodulatory, anti-atherosclerosis, ameliorating digestive system and reproductive system, improving neurodegeneration and myocardial hypertrophy, as well as reducing blood glucose. In addition, studies revealed that amygdalin's toxicity was caused by its poisonous decomposite product of benzaldehyde and hydrogen cyanide after oral ingestion, toxicity of intravenous administration route was far less than the oral route, and it can be avoidable with an oral dose ranging from 0.6 to 1 g per day.

CONCLUSION

This paper has systematically reviewed the pharmacology and toxicology of amygdalin and provided comprehensive information on this compound. We hope this review highlights some perspectives for the future research and development of amygdalin.

Effects of the Gut microbiota on Amygdalin and its use as an anti-cancer therapy: Substantial review on the key components involved in altering dose efficacy and toxicity

Conventional and Alternative Medicine (CAM) is popularly used due to side-effects and failure of approved methods, for diseases like Epilepsy and Cancer. Amygdalin, a cyanogenic diglycoside is commonly administered for cancer with other CAM therapies like vitamins and seeds of fruits like apricots and bitter almonds, due to its ability to hydrolyse to hydrogen cyanide (HCN), benzaldehyde and glucose. Over the years, several cases of cyanide toxicity on ingestion have been documented. In-vitro and in-vivo studies using various doses and modes of administration, like IV administration studies that showed no HCN formation, point to the role played by the gut microbiota for the commonly seen poisoning on consumption. The anaerobic Bacteriodetes phylum found in the gut has a high β-glucosidase activity needed for amygdalin hydrolysis to HCN. However, there are certain conditions under which these HCN levels rise to cause toxicity. Case studies have shown toxicity on ingestion of variable doses of amygdalin and no HCN side-effects on consumption of high doses. This review shows how factors like probiotic and prebiotic consumption, other CAM therapies, obesity, diet, age and the like, that alter gut consortium, are responsible for the varying conditions under which toxicity occurs and can be further studied to set-up conditions for safe oral doses. It also indicates ways to delay or quickly treat cyanide toxicity due to oral administration and, reviews conflicts on amygdalin's anti-cancer abilities, dose levels, mode of administration and pharmacokinetics that have hindered its official acceptance at a therapeutic level.

Antidote Use in the Critically Ill Poisoned Patient

The proper use of antidotes in the intensive care setting when combined with appropriate general supportive care may reduce the morbidity and mortality associated with severe poisonings. The more commonly used antidotes that may be encountered in the intensive care unit ( N-acetylcysteine, ethanol, fomepizole, physostigmine, naloxone, flumazenil, sodium bicarbonate, octreotide, pyridoxine, cyanide antidote kit, pralidoxime, atropine, digoxin immune Fab, glucagon, calcium gluconate and chloride, deferoxamine, phytonadione, botulism antitoxin, methylene blue, and Crotaline snake antivenom) are reviewed. Proper indications for their use and knowledge of the possible adverse effects accompanying antidotal therapy will allow the physician to appropriately manage the severely poisoned patient.

Inhalation injury: epidemiology, pathology, treatment strategies

Lung injury resulting from inhalation of smoke or chemical products of combustion continues to be associated with significant morbidity and mortality. Combined with cutaneous burns, inhalation injury increases fluid resuscitation requirements, incidence of pulmonary complications and overall mortality of thermal injury. While many products and techniques have been developed to manage cutaneous thermal trauma, relatively few diagnosis-specific therapeutic options have been identified for patients with inhalation injury. Several factors explain slower progress for improvement in management of patients with inhalation injury. Inhalation injury is a more complex clinical problem. Burned cutaneous tissue may be excised and replaced with skin grafts. Injured pulmonary tissue must be protected from secondary injury due to resuscitation, mechanical ventilation and infection while host repair mechanisms receive appropriate support. Many of the consequences of smoke inhalation result from an inflammatory response involving mediators whose number and role remain incompletely understood despite improved tools for processing of clinical material. Improvements in mortality from inhalation injury are mostly due to widespread improvements in critical care rather than focused interventions for smoke inhalation.

Morbidity associated with inhalation injury is produced by heat exposure and inhaled toxins. Management of toxin exposure in smoke inhalation remains controversial, particularly as related to carbon monoxide and cyanide. Hyperbaric oxygen treatment has been evaluated in multiple trials to manage neurologic sequelae of carbon monoxide exposure. Unfortunately, data to date do not support application of hyperbaric oxygen in this population outside the context of clinical trials. Cyanide is another toxin produced by combustion of natural or synthetic materials. A number of antidote strategies have been evaluated to address tissue hypoxia associated with cyanide exposure. Data from European centers supports application of specific antidotes for cyanide toxicity. Consistent international support for this therapy is lacking. Even diagnostic criteria are not consistently applied though bronchoscopy is one diagnostic and therapeutic tool. Medical strategies under investigation for specific treatment of smoke inhalation include beta-agonists, pulmonary blood flow modifiers, anticoagulants and antiinflammatory strategies. Until the value of these and other approaches is confirmed, however, the clinical approach to inhalation injury is supportive.

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.

Clarification of cyanide's effect on oxygen transport characteristics in a canine model

OBJECTIVE

To clarify the cardiovascular mechanisms of cyanide poisoning by evaluating oxygen transport characteristics using a canine model.

METHODS

A prospective controlled experiment was performed at a hospital-based animal laboratory. Five male beagle (17 (2) kg) dogs were anesthetised with alpha-chloralose, paralysed with pancuronium bromide and mechanically ventilated. Potassium cyanide was infused at 0.045 mg/kg/min for 110 min. Heart rate, blood pressure, cardiac output, oxygen delivery (DO2), oxygen consumption (VO2) and oxygen extraction ratio (OER) were measured every 10 min for 140 min. DO2 was measured by an indirect calorimeter.

RESULTS

Cyanide and lactate levels peaked at 1.52 (0.25) mg/l and 9.1 (1.5) mmol/l, respectively. Systolic blood pressure remained relatively constant whereas diastolic blood pressure decreased by 19%. Cardiac output, heart rate and DO2 increased to a maximum of 6%, 10% and 10%, respectively, at 40 min, after which they declined to a low of 32%, 28% and 30% below baseline, respectively. Stroke volume remained constant. Oxygen consumption initially increased by 5%, then decreased to 24% below baseline. The OER initially declined to 35% below baseline, then increased throughout the rest of the study.

CONCLUSION

Cyanide poisoning in the canine model showed two phases of injury. The first (compensated) phase had a mechanism consistent with a traditional global oxygen consumption defect. The second (decompensated) phase had a mechanism consistent with heart failure. This heart failure was due to bradycardia. These data suggest chronotropy as an avenue of further study in the temporary treatment of cyanide poisoning.

Cyanides

Cyanide is a likely weapon for terrorists due to its notoriety, lethality, and availability. Poisoning results in central nervous system and cardiovascular dysfunction due to inhibition of oxidative phosphorylation. Laboratory findings of anion gap metabolic acidosis and hyperlactemia aid in confirming the diagnosis. Treatment for significant poisonings includes aggressive supportive care and administration of antidotes such as sodium nitrite, sodium thiosulfate, and hydroxocobalamin. Survivors of significant poisonings can have long-term neurologic dysfunction.

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.

Toxicology in the critically ill patient

Intoxications present in many forms including: known drug overdose or toxic exposure, illicit drug use, suicide attempt, accidental exposure, and chemical or biological terrorism. A high index of suspicion and familiarity with toxidromes can lead to early diagnosis and intervention in critically ill, poisoned patients. Despite a paucity of evidence-based information on the management of intoxicated patients, a rational and systematic approach can be life saving.

An incident of hydrogen cyanide poisoning

Seven cases of hydrogen cyanide gas poisoning which occurred in an industrial building in Hong Kong are presented here. Two of them were more severely injured and required specific antidotal treatment. The other five were mild and responded to supportive treatment alone. All except one patient recovered completely. Cyanide poisoning is relatively uncommon in urbanized area, so high index of suspicion is important for early diagnosis and treatment. We believe that prevention of cyanide poisoning can be achieved by proper storage of chemicals, and by enforcing rescuers to wear special chemical protective clothing to avoid systemic poisoning because of dermal absorption of hydrogen cyanide gas. As there are newer and safer cyanide antidotes available, each emergency department should have a stock of updated products such as hydroxocobalamin.

Hydrogen cyanide generation by mu-opiate receptor activation: possible neuromodulatory role of endogenous cyanide

Hydrogen cyanide, a gaseous molecule, is produced by white blood cells during phagocytosis. The present study examined the possibility that neuronal-like cells may also produce cyanide following activation. Rat pheochromocytoma (PC12) cells exhibited a low level of cyanide generation that was significantly increased by mu-opiate agonists (hydromorphone, morphine) and blocked by naloxone. A variety of other agonists including bradykinin, nicotine and glutamate did not generate cyanide in PC12 cells. Systemic administration of hydromorphone to rats increased brain cyanide levels by 61% after 15 min. Using microdialysis probes implanted in the cortical-hippocampal areas of the anesthetized rat or in the hypothalamus of the conscious hamster, a 2- to 5-fold increase in cyanide generation was seen after hydromorphone administration and this increase was blocked by naloxone. To determine whether cyanide release by hydromorphone has functional significance in a neuronal system, cyanide enhancement of N-methyl-D-aspartate (NMDA)-induced increased [Ca2+]i was measured in rat cerebellar granule cells. Hydromorphone enhanced the response to NMDA similar to cyanide and the hydromorphone effect was blocked by cyanide scavengers. These data show that cyanide generation is increased in neuronal tissue by a mu-opiate receptor agonist and it is proposed that endogenous cyanide may modulate the NMDA receptor response.

The clinical experience of acute cyanide poisoning

The authors reviewed the clinical manifestations, complications, and the prognosis affected by Lilly Cyanide Antidote in 21 victims of acute cyanide poisoning over a 10-year period. The clinical signs and symptoms in cyanide poisoning are variable. Among 21 cases, loss of consciousness (15), metabolic acidosis (14), and cardiopulmonary failure (9) were the three leading manifestations of cyanide intoxication. Anoxic encephalopathy (6) was not uncommon in the severely intoxicated victims. Diabetes insipidus (1) or clinical signs and symptoms mimicking diabetes insipidus (3) may be an ominous sign to encephalopathy victims. The major cause of fatal cyanide poisoning is the intentional ingestion of cyanide compounds as part of a suicide attempt. Decrease of arteriovenous difference of O2 partial pressure may be a clue for the suspicion of cyanide intoxication. Although the authors cannot show a statistically significant difference (P = .47) for the Lilly cyanide antidote kit in terms of improving the survival rate for victims of cyanide poisoning, the antidote kit was always mandatory in our study in the cases of severely intoxicated victims who survived. Early diagnosis, prompt, intensive therapy with antidote, and supportive care are still the golden rules for the treatment of acute cyanide poisoning, whether in the ED or on the scene.

Poisonings in laboratory personnel and health care professionals

A case report of an unresponsive chemist presenting to the emergency department is presented; in retrospect, the patient was discovered to have intentionally ingested cyanide. A review of literature regarding ingestions in laboratory and health care personnel reveals five common points encountered in these personnel: barbiturates, carbon monoxide, cyanide, azides, and methemoglobin-inducing chemicals. Key diagnostic findings, in the absence of history of exposure, are discussed for these five agents.

Hyperbaric oxygen therapy for acute smoke inhalation injuries

Hyperbaric oxygen therapy is an important adjunct in the management of respiratory injuries secondary to smoke inhalation, especially when injury is complicated by inhalation of a toxic chemical such as carbon monoxide or cyanide. For carbon monoxide poisoning, such therapy has become a standard of practice. As more information becomes available concerning the ability of hyperbaric oxygen to reduce reperfusion injuries, we anticipate that this therapy will become a standard of practice for managing smoke inhalation injuries and cyanide poisoning as well.

Cyanide poisoning successfully treated without 'therapeutic methemoglobin levels'

A 24-year-old woman ingested an unknown amount of potassium cyanide in a suicide attempt. Coma and metabolic acidosis developed. Administration of the Lilly Cyanide Antidote kit (Eli Lilly and Co, Indianapolis) resulted in prompt resolution of symptoms and full recovery. Whole blood cyanide level was 13 micrograms/mL approximately one hour after ingestion. The highest measured methemoglobin level after sodium nitrite administration was 9.2%, demonstrating that attaining a "therapeutic methemoglobin level" of 25% is unnecessary to insure a satisfactory clinical outcome. Because severe hypotension or excessive methemoglobinemia can be caused by the sodium nitrite component of the Lilly kit, only enough to produce an acceptable clinical response should be administered.

Hyperbaric oxygen. A therapy in search of diseases

The application of HBO to the therapy of various human diseases developed over a 300 year period. Like most of medicine, the basis of these applications was and continues to be pragmatic in nature, and involves uncritical and untested judgments. The possibility of risks has been understated and possible benefits have been overstated. Individual physicians offering HBO and organized groups, such as the Undersea Medical Society, advocating its use may well be highly motivated, well meaning, and sincerely convinced that HBO is an important therapeutic approach. It may be that, buried among the host of indications, will be some disorders for which HBO is uniquely and highly effective. If so, the present nonsystem for evaluating responses to HBO will require modification, so that these potentially valuable additions to therapeutics are not lost. Because of its almost global application to a wide variety of diseases, HBO therapy lends itself easily to medical adventurism (therapy in search of a disease) and economic exploitation. If there is some patient benefit to come from the experience of the last 300 years, changes in approach, initiated by baromedical devotees or by medicine generally, or resulting from pressures outside of medicine, will be required.

Physical assessment and differential diagnosis of the poisoned patient

The rapid diagnosis and immediate intervention required in patients with serious drug overdose or poisoning makes toxicological screening of limited value to the emergency department physician. Instead, a careful clinical evaluation using the history, physical examination, and the more readily available laboratory tests may allow a tentative diagnosis and the initiation of life-saving treatment. Laboratory tests should include serum osmolality, electrolytes, glucose, BUN and an estimation of the anion and osmolar gaps. The ECG can also provide useful information. Clinical findings of important include altered blood pressure, pulse, respiration and body temperature, the presence of coma, agitation, delirium or psychosis, and muscular weakness. An ophthalmological examination is also of importance in the acutely poisoned patient. Oral burns or dysphagia may occur following ingestion of any strongly reactive substance, but the absence of oral burns does not preclude the possibility of oesophageal or stomach injury. Odours and skin colour may also contribute to the diagnosis. Comprehensive toxicology screening may not be immediately available, or may be inaccurate, thus adding little to the information obtained during the initial evaluation of the poisoned patient.

Nitrite/thiosulfate treated acute cyanide poisoning: estimated kinetics after antidote

A 34 year old, 73 kg man ingested a 1 gram potassium cyanide pellet in a suicide attempt. Within one hour, coma, apnea, metabolic acidosis, and seizures developed. Sodium nitrite and sodium thiosulfate were administered. Dramatic improvement in the clinical condition occurred by the completion of antidote infusion. Methemoglobin level was 2% immediately after nitrite administration. Serial whole blood cyanide levels were obtained, documenting a highest measured level of 15.68 mcg/mL. Estimations of toxicokinetic parameters including terminal half-life (t 1/2) (19 hours), clearance (163 mL/minute), and volume of distribution (Vd) (0.41 L/kg) were calculated. The nitrite/thiosulfate combination was clinically efficacious in this case and resulted in complete recovery.

Hydroxycobalamin/sodium thiosulfate as a cyanide antidote

Severe, acute cyanide poisoning is uncommon and can be very difficult to diagnose if a history of exposure is unavailable. Victims of smoke inhalation may have significant cyanide poisoning as well as carbon monoxide toxicity. The Lilly Cyanide Antidote Kit currently available in America unfortunately has its own inherent toxicity. An efficacious antidote lacking toxicity is desirable, especially in cases where the diagnosis of cyanide poisoning cannot be made with certainty. Hydroxycobalamin/sodium thiosulfate has been used in France since 1970. Both components have been shown to be safe and efficacious in animal studies. Case reports of human cyanide poisoning treated with hydroxycobalamin/sodium thiosulfate have been published only in French. Animal and human data on the use of this antidotal combination are reviewed. Hydroxycobalamin/sodium thiosulfate is an efficacious cyanide antidote with little inherent toxicity.

Clinical toxicology of cyanide

Cyanide poisoning causes a high incidence of severe symptomatology and fatality. There are numerous sources of potential cyanide exposure. Without the history of cyanide exposure, diagnosis is often difficult. Treatment with supportive measures and available specific and efficacious antidotes frequently allows survival. The toxicology of cyanide, including sources, clinical features, diagnosis, and treatment, is reviewed.