Plasma free cyanide and blood total cyanide: a rapid completely automated microdistillation assay

Concurrent determination of cyanide and thiocyanate in human and swine antemortem and postmortem blood by high-performance liquid chromatography-tandem mass spectrometry

Cyanide (in the form of cyanide anion (CN-) or hydrogen cyanide (HCN), inclusively represented as CN) can be a rapidly acting and deadly poison, but it is also a common chemical component of a variety of natural and anthropogenic substances. The main mechanism of acute CN toxicity is based on blocking terminal electron transfer by inhibiting cytochrome c oxidase, resulting in cellular hypoxia, cytotoxic anoxia, and potential death. Due to the well-established link between blood CN concentrations and the manifestation of symptoms, the determination of blood concentration of CN, along with the major metabolite, thiocyanate (SCN-), is critical. Because currently there is no method of analysis available for the simultaneous detection of CN and SCN- from blood, a sensitive method for the simultaneous analysis of CN and SCN- from human ante- and postmortem blood via liquid chromatography-tandem MS analysis was developed. For this method, sample preparation for CN involved active microdiffusion with subsequent chemical modification using naphthalene-2,3-dicarboxaldehyde (NDA) and taurine (i.e., the capture solution). Preparation for SCN- was accomplished via protein precipitation and monobromobimane (MBB) modification. The method produced good sensitivity for CN with antemortem limit of detection (LODs) of 219 nM and 605 nM for CN and SCN-, respectively, and postmortem LODs of 352 nM and 509 nM. The dynamic ranges of the method were 5-500 µM and 10-500 µM in ante- and postmortem blood, respectively. In addition, the method produced good accuracy (100 ± 15%) and precision (≤ 15.2% relative standard deviation). The method was able to detect elevated levels of CN and SCN- in both antemortem (N = 5) and postmortem (N = 4) blood samples from CN-exposed swine compared to nonexposed swine.

Noninvasive in vivo monitoring of cyanide toxicity and treatment using diffuse optical spectroscopy in a rabbit model

Currently, no reliable noninvasive methods exist for monitoring the severity of in vivo cyanide (CN) toxicity, treatment, and resulting physiological changes. We developed a broadband diffuse optical spectroscopy (DOS) system to measure bulk tissue absorption and scattering. DOS was used to optically monitor CN toxicity and treatment with sodium nitrite (NaNO2). To perform experiments, the DOS probe was placed on the hind leg of rabbits. A sodium CN solution was infused intravenously. DOS and concurrent physiologic measurements were obtained. After completion of CN infusion, NaNO2 was infused to induce methemoglobinemia (MetHb). During infusion of CN, blood gas measurements showed an increase in venous partial pressure of oxygen (pO2), and following reversal, venous pO2 values decreased. DOS measurements demonstrated corresponding changes in hemoglobin oxygenation states and redox states of cytochrome-c oxidase (CcO) during CN infusion and NaNO2 treatment. Therefore, DOS enables detection and monitoring of CN toxicity and treatment with NaNO2.

Intramuscular cobinamide sulfite in a rabbit model of sublethal cyanide toxicity

STUDY OBJECTIVE

Exposure to cyanide in fires and industrial exposures and intentional cyanide poisoning by terrorists leading to mass casualties is an ongoing threat. Current treatments for cyanide poisoning must be administered intravenously, and no rapid treatment methods are available for mass casualty cyanide exposures. Cobinamide is a cobalamin (vitamin B(12)) analog with an extraordinarily high affinity for cyanide that is more water-soluble than cobalamin. We investigate the use of intramuscular cobinamide sulfite to reverse cyanide toxicity-induced physiologic changes in a sublethal cyanide exposure animal model and determine the ability of an intramuscular cobinamide sulfite injection to rapidly reverse the physiologic effects of cyanide toxicity.

METHODS

New Zealand white rabbits were given 10 mg sodium cyanide intravenously over 60 minutes. Quantitative diffuse optical spectroscopy and continuous-wave near-infrared spectroscopy monitoring of tissue oxyhemoglobin and deoxyhemoglobin concentrations were performed concurrently with blood cyanide level measurements and cobinamide levels. Immediately after completion of the cyanide infusion, the rabbits were injected intramuscularly with cobinamide sulfite (n=6) or inactive vehicle (controls, n=5).

RESULTS

Intramuscular administration led to rapid mobilization of cobinamide and was extremely effective at reversing the physiologic effects of cyanide on oxyhemoglobin and within deoxyhemoglobin extraction. Recovery time to 63% of their baseline values in the central nervous system occurred within a mean of 1,032 minutes in the control group and 9 minutes in the cobinamide group, with a difference of 1,023 minutes (95% confidence interval 116 to 1,874 minutes). In muscle tissue, recovery times were 76 and 24 minutes, with a difference of 52 minutes (95% confidence interval 7 to 98 minutes). RBC cyanide levels returned toward normal significantly faster in cobinamide sulfite-treated animals than in control animals.

CONCLUSION

Intramuscular cobinamide sulfite rapidly and effectively reverses the physiologic effects of cyanide poisoning, suggesting that a compact cyanide antidote kit can be developed for mass casualty cyanide exposures.

Comparison of cobinamide to hydroxocobalamin in reversing cyanide physiologic effects in rabbits using diffuse optical spectroscopy monitoring

Our purpose is to compare cobinamide to hydroxocobalamin in reversing cyanide (CN)-induced physiologic effects in an animal model using diffuse optical spectroscopy (DOS). Cyanide poisoning is a major threat worldwide. Cobinamide is a novel molecule that can bind two molecules of cyanide, has a much higher binding affinity than hydroxocobalamin, and is more water soluble. We investigated the ability of equimolar doses of cobinamide and hydroxocobalamin to reverse the effects of cyanide exposure in an animal model monitored continuously by DOS. Cyanide toxicity was induced in 16 New Zealand white rabbits by intravenous infusion. Animals were divided into three groups: controls (n=5) received saline following cyanide, hydroxocobalamin (N=6) following cyanide, and cobinamide (N=5) following cyanide. Cobinamide caused significantly faster and more complete recovery of oxy- and deoxyhemoglobin concentrations in cyanide-exposed animals than hydroxocobalamin- or saline-treated animals, with a recovery time constant of 13.8+/-7.1 min compared to 75.4+/-25.1 and 76.4+/-42.7 min, for hydroxocobalamin- and saline-treated animals, respectively (p<0.0001). This study indicates that cobinamide more rapidly and completely reverses the physiologic effects of cyanide than equimolar doses of cobalamin at the dose used in this study, and CN effects and response can be followed noninvasively using DOS.

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.