Cyanide: critical issues in diagnosis and treatment

Thermoresponsive copolymer containing a coumarin-spiropyran conjugate: reusable fluorescent sensor for cyanide anion detection in water

A simple copolymer consisting of N-isopropylacrylamide and coumarin-conjugated spiropyran (CS) units, poly(NIPAM-co-CS), has been synthesized. This polymer enables selective fluorometric detection of cyanide anion (CN(-)) in water at room temperature. The polymer itself shows almost no fluorescence, but shows a strong blue fluorescence in the presence of CN(-) under irradiation of UV light. The fluorescence enhancement occurs via a nucleophilic interaction between CN(-) and the photoformed merocyanine form of the CS unit, leading to a localization of π-electrons on the coumarin moiety. The polymer enables accurate determination of very low levels of CN(-) (>0.5 μM). The polymer can be recovered from water by simple centrifugation at high temperature (>40 °C), due to the heat-induced aggregation of the polymer. In addition, the polymer is regenerated by simple acid treatment, and the resulting polymer is successfully reused for further CN(-) sensing without loss of sensitivity.

Cyanide: an unreported cause of neurological complications following smoke inhalation

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

Development of nano alpha-ketoglutarate nebulization formulation and its pharmacokinetic and safety evaluation in healthy human volunteers for cyanide poisoning

Development of nano alpha-ketoglutarate (A-KG) nebulization formulation for neutralization of inhaled cyanide ion toxicity. Objectives of the present study were to (a) develop a novel A-KG nebulization formulation against cyanide poisoning, particularly hydrogen cyanide gas (b) validate its respiratory fraction in vitro and in vivo, and (c) create its pharmacokinetic data in human volunteers. The formulation was optimized on the basis of particle size of aerosolized droplets after nebulization in 6 volunteers. Gamma scintigraphy was used to quantify total and regional lung deposition of nebulized A-KG after radiolabeling it with Technetium-99m. The formulation was optimized using 30% ethanol-saline with particle size in the range of 300-500 nm. In vitro and in vivo studies showed that drug nebulization resulted in a significant respirable fraction of 65 ± 0.6% with whole lung deposition of 13 ± 1%. Human pharmacokinetic data was derived in 6 healthy human volunteers with peak serum concentration (C(max)) of 39 ± 3 μg/ml, while the area under curve (AUC) after inhalation was 376 ± 23 μg × h/ml indicating that the drug was rapidly and completely absorbed when targeted directly to lungs. Significant lung deposition of A-KG was achieved with the developed formulation. The formulation appears to have several advantages, including the potential of neutralizing inhaled CN(-) ions in the lungs themselves. It is a safe and efficacious procedure, suitable for hospital or ambulance use in accidental cyanide poisoning cases, or as a preventive approach for fire-rescue teams.

Cyanide intoxication as part of smoke inhalation--a review on diagnosis and treatment from the emergency perspective

This paper reviews the current literature on smoke inhalation injuries with special attention to the effects of hydrogen cyanide. It is assumed that cyanide poisoning is still an overlooked diagnosis in fire victims. Treatment against cyanide poisoning in the emergency setting should be given based on the clinical diagnosis only. Oxygen in combination with a recommended antidote should be given immediately, the first to reduce cellular hypoxia and the second to eliminate cyanide. A specific antidote is hydroxycobalamin, which can be given iv. and has few side effects.

Specific recognition and sensing of CN- in sodium cyanide solution

Specific recognition of CN(-) in sodium cyanide solution was achieved using two imidazole-based receptors (A and B). Visually detectable color changes were associated with the formation of hydrogen bonded adducts, A.CN(-) and B.CN(-). Ratiometric fluorescence response was achieved for receptor A on binding to CN(-), and this reagent was used for imaging bacterial cells pre-exposed to 1.42 microM CN(-) solution.

A case of cyanide poisoning and the use of arterial blood gas analysis to direct therapy

Cyanide poisoning is a difficult diagnosis for health care professionals. Existing reports clearly demonstrate that the initial diagnosis is often missed in surreptitious cases. The signs and symptoms can mimic numerous other disease processes. We report a case in which a suicidal patient ingested cyanide and was found unresponsive by 2 laboratory coworkers. The coworkers employed cardiopulmonary resuscitation with mouth-to-mouth resuscitation. The suicidal patient died shortly after arrival to the hospital, while the 2 coworkers who performed mouth-to-mouth resuscitation presented with signs and symptoms that mimicked early cyanide toxicity but were instead due to acute stress response. An arterial blood gas analysis may help aid in the diagnosis of cyanide toxicity. Electrocardiographic findings in a patient with cyanide poisoning range significantly, depending on the stage of the poisoning.

Effect of hyperbaric oxygen therapy on whole blood cyanide concentrations in carbon monoxide intoxicated patients from fire accidents

Background

Hydrogen cyanide (HCN) and carbon monoxide (CO) may be important components of smoke from fire accidents. Accordingly, patients admitted to hospital from fire accidents may have been exposed to both HCN and CO. Cyanide (CN) intoxication results in cytotoxic hypoxia leading to organ dysfunction and possibly death. While several reports support the use of hyperbaric oxygen therapy (HBO) for the treatment of severe CO poisoning, limited data exist on the effect of HBO during CN poisoning. HBO increases the elimination rate of CO haemoglobin in proportion to the increased oxygen partial pressure and animal experiments have shown that in rats exposed to CN intoxication, HBO can increase the concentration of CN in whole blood.

Objective

The purpose of the present study was to determine whole blood CN concentrations in fire victims before and after HBO treatment.

Materials and methods

The patients included were those admitted to the hospital because of CO intoxication, either as fire victims with smoke inhalation injuries or from other exposures to CO. In thirty-seven of these patients we measured CN concentrations in blood samples, using a Conway/microdiffusion technique, before and after HBO. The blood samples consisted of the remaining 2 mL from the arterial blood gas analysis. CN concentration in blood from fire victims was compared to 12 patients from non-fire accidents but otherwise also exposed to CO intoxication.

Results

The mean WB-CN concentration before patients received HBO did not differ significantly between the two groups of patients (p = 0.42). The difference between WB-CN before and after HBO did not differ significantly between the two groups of patients (p = 0.7). Lactate in plasma before and after did not differ significantly between the two groups of patients. Twelve of the 25 fire patients and one of the non-fire patients had been given a dose of hydroxycobalamin before HBO.

Discussion and Conclusion

CN concentrations in blood from patients admitted to hospital with CO intoxication and smoke inhalation exposure did not differ significantly from controls. Accordingly, we were not able to detect any changes in CN concentrations in blood after treatment with HBO.

Trial Registration

ClinicalTrials.gov identifier: NCT00280579

Airway management and smoke inhalation injury in the burn patient

Smoke inhalation injury, a unique form of acute lung injury, greatly increases the occurrence of postburn morbidity and mortality. In addition to early intubation for upper-airway protection, subsequent critical care of patients who have this injury should be directed at maintaining distal airway patency. High-frequency ventilation, inhaled heparin, and aggressive pulmonary toilet are among the therapies available. Even so, immunosuppression, intubation, and airway damage predispose these patients to pneumonia and other complications.

Strapped calix[4]pyrroles bearing a 1,3-indanedione at a beta-pyrrolic position: chemodosimeters for the cyanide anion

A strapped calix[4]pyrrole bearing a 1,3-indanedione group at a beta-pyrrolic position has been synthesized and studied as a ratiometric cyanide-selective chemosensor. A concentration-dependent bleaching of the initial yellow color was observed upon addition of the cyanide anion. The bleaching, which was observed exclusively with the cyanide anion, occurred even in the presence of other anions. Spectroscopic studies provide support for a mechanistic interpretation wherein the cyanide anion forms a complex with the receptor (K = 2.78 x 10(4) M(-1)) through a fast equilibrium, which is followed by slow nucleophilic addition to the beta-position of the 1,3-indanedione group. A minimum inhibitory effect from other anions was observed, a feature that could be beneficial in the selective sensing of the cyanide anion.

Haemodiafiltration for Poisoning with an Unknown Substance

We describe the case of a young male, found collapsed following poisoning with an unknown substance. He had a Glasgow Coma Score (GCS) of three with a profound metabolic acidosis, despite poisoning with a substance which was strongly basic. He was treated with haemodiafiltration to correct the biochemical derangements. The poison was found to be cyanide, so the patient was also given sodium thiosulphate as an antidote. We review the pathophysiology of cyanide toxicity, the antidotes available and discuss the role of haemodiafiltration in poisoning where the ingested substance is unknown.

Ammonium Boranes for the Selective Complexation of Cyanide or Fluoride Ions in Water

With the recognition of aqueous fluoride and cyanide ions as an objective, we have investigated the anion binding properties of two isomeric ammonium boranes, namely [p-(Mes2B)C6H4(NMe3)]+ ([1]+) and [o-(Mes2B)C6H4(NMe3)]+ ([2]+). These cationic boranes, which could be obtained by reaction of the known 4- and 2-dimesitylboryl-N,N-dimethylaniline with MeOTf, have been investigated both experimentally and computationally. They both react with fluoride and cyanide ions in organic solvents to afford the corresponding fluoroborate/ or cyanoborate/ammonium zwitterions 1F, 1CN, 2F, and 2CN. In aqueous solution, however, these cationic boranes behave as remarkably selective receptors. Indeed, [1]+ only complexes cyanide ions while [2]+ only complexes fluoride ions. In H2O/DMSO 60:40 vol (HEPES 6 mM, pH 7), the cyanide binding constant of [1]+ and the fluoride binding constant of [2]+ are respectively equal to 3.9 (+/-0.1) x 108 and 910 (+/-50) M-1. Structural and computational studies indicate that both steric and electronic effects contribute to the unusual selectivity displayed by these cationic boranes. Owing to favorable Coulombic effects, the para-derivative [1]+ has a very high affinity for cyanide; yet these effects are not sufficiently intense to allow complexation of the more efficiently hydrated and less basic fluoride anion. In the case of the ortho-derivative [2]+, the proximity of the ammonium moiety leads to an increase in the Lewis acidity of the boron center thus making fluoride binding possible. However, steric effects prevent cyanide coordination to the boron center of [2]+. Finally, cation [1]+ and [2]+ bind their dedicated anions reversibly and show a negligible response in the presence of other common anions including Cl-, Br-, I-, NO3-, OAc-, H2PO4-, and HSO4-.