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Đầu tiên là một tác dụng trầm cảm thần kinh trung ương. Một kết quả của hiệu ứng này là tê liệt trung tâm hô hấp và tử vong. Thứ hai là ức chế cytochrome oxidase trong một cách rất tương tự như tác dụng của cyanide. H2S thực sự là một chất ức chế mạnh hơn của cytochrome oxidase hơn là xyanua. | Toxicity of Sulfides Hydrogen sulfide has two major toxic actions. The first is a depressant effect on the CNS. A result of this effect is paralysis of the respiratory center and death. The second is inhibition of cytochrome oxidase in a manner very similar to the effect of cyanide. H2S is actually a more potent inhibitor of cytochrome oxidase than is cyanide. Carbon disulfide has some toxic features in common with H2S. It attacks the CNS and the cardiovascular system. However it has its own uniquely toxic character in causing a peripheral neuropathy with cranial nerve damage see Chapter 10 on neurotoxins . Curiously it is also atherogenic in experimental animals. Therapy The cyanide antidote kit is effective with H2S poisoning. The nitrites within the kit convert hemoglobin to methemoglobin which becomes an agent for binding hydrogen sulfide before it can bind cytochrome oxidase and cause death. Sulfmethemoglobin is formed by the reaction between methemoglobin and either H2S or hydrogen sulfide anion and this substance is excreted into the urine as such or as nontoxic metabolites. Laboratory Testing Hydrogen sulfide is like cyanide in the sense that many victims will die too soon for laboratory evaluation to be of any help. However testing for sulfide ion in blood may help to make the diagnosis for those who are less disabled. An ion-selective electrode has been developed for measurement of sulfide ion. Because this electrode is not completely specific to sulfide to the exclusion of all other ions it is necessary to pre-treat the specimen and isolate sulfide. This has been done in one method with Conway microdiffusion cells. Concentrations of sulfide ion found in H2S deaths ranged from 1.7 to 3.75 pg mL. hydrocarbons By definition these are compounds which contain only carbon and hydrogen. Many such compounds have been identified in the natural world a good number of which are found in crude oil. They include the aliphatic alkanes alkenes and alkynes which differ