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Asphyxiants dr.zachariah thomas
- 1. ASPHYXIANTS MECAHANISMOF ACTION CLINICAL FEATURES DIAGNOSIS MANAGEMENT AUTOPSY APPEARANCE FORENSIC IMPORTANCE 1.HYDROGEN CYANIDE. Cyanidearewhite powders Prussicacid (2%) Scheelesacid (4%) 20-40% persons cannot smell the gas, sex-linked recessive trait. HCN normal constituent (15 to 30microgram) Inhibits cytochrome oxidase, carbonic anhydrase. It blocks final step of oxidative phosphorylation and preventsformationof ATP. Cyanide acts by reducing oxygencapacityof blood.It preventsuptake of oxygen for cellular respiration Cause histotoxic anoxia Absorbed from respiratory system. Alkaline cyanides wheningestedare converted by hydrochloric acid in the gastric juice into chlorides and hydrocyanic acid is liberated. Symptoms due to cellular hypoxia. CNS,GIT,RS,CVS manifestations.Tobacco amblyopia,Lebershereditary optic atrophy, tropical ataxia Lee Jones test (Gastric aspirate with ferrous sulphate and 2% NaOH and 10 drop HCl resultsin greenblue colour. Smell of bitter almonds, similar to crushed tapioca leaves Stabilisation, Amyl nitrate(0.2ml inhalation, Sodiumnitrate (0.3gm)insterile water, form methHb competes with cytochrome oxidase, through same needle give Sod: thiosulphate50% solution it converts cyanide to thiocyanate which is excreted in urine. Hydroxocobalamin infusionform nontoxic cyanocobalamin Corrosion of mouth and nostrils, smell of bitter almonds. Hemorrhagic gastritis, pulmonary edema. Bright red postmortem staining Suicidal pills Homicidal Judicial execution (cyanide gas) 2.CARBON MONOXIDE (Cellulartoxin) Absorbedacrossthe alveolus,combineswith Hb.COaffinityto myoglobinisabout40 timesgreaterthanO2 which cause myocardial depression. Ithas200 to 300 time’sgreateraffinity for Hb. It inhibitselectron transportby blocking CytochromeA3 oxidase and P450.It interfereswith other ferroprotein suchas myglobin&enzymes 10%-breathlessness, headache 20-30%-Throbbingheadache, irritability 30-40%-Cherryred discoloration,confusion 40-50%-Confusion, hallucination 50-60%-Syncope,coma 70-80%-Coma, depressed reflex,weak pulse. 80%- Deathfrom respiratory arrest.Death due to anaemic anoxia. CO oximeter BloodTests: Kunkelstest or tannicacid test: cherryred colour Hoppe Seylers test:blood& 10%NaOH, CO turn pink. Spectroscopy: bandin yellow between D&E ,no changeafter addingNH3 S. Removal,100% hyperbaricO2 , inhalationof O2 ata pressure greaterthan one atmos, correct metabolic acidosis,cerebral oedema Cherryred discolouration of skin, blood, cutaneous bullae. Necrosisof putamen, globuspallidus CO automatism Accidental poisoning
- 2. ASPHYXIANTS MECHANISM OF ACTION CLINICAL FEATURES DIAGNOSIS MANAGEMENT AUTOPSY APPEARANCE FORENSIC IMPORTANCE 2.CARBON DIOXIDE Simple asphyxiant preventingtissue fromobtaining oxygen 5%- labouredbreathing 10% ataxiaunconsciousness 40%-dyspnoea, discomfort muscle weakness 50%- dyspnea,tightness fullnessof headandringing inears,lossof muscular power,drowsiness,coma and death. 60-80%- Unconsciousness, convulsion,coma,and death. History,Cyanosis, congestion Remove fromsource Artificial respiration OXYGEN administration Cardiac stimulants. congestion, cyanosis, featuresof respiratory failure GHOST WELL Accidental poisoning inpersonsentering unusedwell. 3.HYDROGEN SULPHIDE Formedbydecompositionof organicmatter. Industrieswhere sulphur compoundisused. Sewergas Combineswith methhaemoglobin to form sulphmethhaemogl obin It interefereswith cellularrespiration by inhibing cytochrome oxidase Tolerable limit 20ppm Cough,giddiness,nausea, feelingof oppression, laboredbreathing,heart beatirregular History,Cyanosis, congestion Remove fromsource Artificial respiration OXYGEN administration Amyl nitrate inhalation and sodiumnitrite infusion Rottenegg odour,signsof asphyxia, greenish discoloration of skin,viscera, bronchial secretions Occupational hazard insewerworkers