Intoxication with methemoglobinizing substances
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Aromatic amines[edit | edit source]
- Aniline, toluidine - liquids.
- Benzidine , 2-naphthylamine - pinkish powder substance.
Professional exposure[edit | edit source]
- Production of dyes (textiles, paper, leather), plastics, rubber, pesticides.
Etiopathogenesis[edit | edit source]
- Fat-soluble substances - they are well absorbed by the skin ,
- They are metabolized into hydroxylamines, which change hemoglobin into methemoglobin , create VR in erythrocytes and give rise to so-called Heinz bodies in erythrocytes (precipitated hemoglobin with cytoskeletal proteins),
- Erythrocytes are more fragile, hemolysis , hemoglobinuria and subsequent kidney damage may occur .
- They are removed by acetylation (people we refer to as so-called slow acetylators are at risk of bladder cancer ).
Aniline (its metabolite phenylhydroxylamine) has the strongest methemoglobinizing effect → functional anemia occurs , the curve shifts to the left, and tissue hypoxia increases . Therapy uses alternative ways of reducing methemoglobin by the enzyme NADPH methemoglobin reductase - it needs methylene blue (a redox substance) as a cofactor.
Clinical picture[edit | edit source]
Acute – lower exposure – CNS excitation (so-called aniline spike);
- Then the manifestations depend on the degree of metHbemia ,
- 10–30% cyanosis , tachycardia , fatigue,
- 30-50% weakness, shortness of breath, headache,
- 50-70% impaired consciousness and death,
- The blood taken is dark brown to black in color (striking plum-blue cyanosis).
Chronic - polyglobulia due to chronic hypoxia.
Therapy[edit | edit source]
Antidote - methylene blue .
Indication[edit | edit source]
- Symptoms of hypoxemia ( dyspnea , confusion, chest pain),
- Methemoglobinemia at 25%,
- Initial dose – 1–2 mg/kg iv,
- Risks - people with a defect of G6P-dehydrogenase (they do not create NADPH) - it does not work and, moreover, it accumulates and can aggravate methemoglobinemia and cause hemolysis.
Toluidine blue - works by the same mechanism, paradoxically, cyanosis deepens after administration (given by the color of the antidote) ascorbic acid - works weaker and slower.
Aromatic nitro compounds[edit | edit source]
- They have the NO 2 group , e.g. nitrobenzene, TNT, trinitrophenol (picric acid),
- Professional exposure – production of aniline, dyes, explosives,
- Etiopathogenesis - they are well absorbed by the skin, by a similar mechanism to the previous ones, they cause methemoglobinemia. In addition, TNT causes massive necrosis and yellow atrophy of the liver with a lethal end, or cataract.
Nitroglycerin[edit | edit source]
- Oily liquid, easily explosive,
- Application – manufacture of explosives, pharmacology,
- They are easily absorbed through the skin, after absorption they are hydrolyzed into inorganic compounds and cause vasodilation,
- After 2-4 days of professional exposure, tolerance develops (thanks to compensatory sympathetic mechanisms) → angina pectoris may occur after exposure is interrupted ,
- After high doses, methemoglobinemia, of mild degree, without Heinz bodies, may occur.
- Acute intoxication - headaches (caused by vasodilatation of CNS vessels), "powder headache" in the occiput, restlessness, depression , sleep disorders, paleness of sweating, drop in pressure, shock,
- High doses – methemoglobinaemia, shortness of breath, unconsciousness,
- Professional exposure - typically the so-called "Monday sickness" - always after a weekend break, compensation sets in during the week, symptoms disappear...,
- Chronic intoxication - angina pectoris and sudden death, paradoxically on days off from work (after interruption of exposure), pseudoneurasthenic symptoms are also described.
Therapy[edit | edit source]
- Angina from habit - we will remove nitrates,
- Acute hypotension is difficult to influence therapeutically - anti-shock position, IV fluids, possibly dopamine , norepinephrine .
Nitrites[edit | edit source]
Synonym: nitrites, -NO 2 ,
- Sodium nitrite – a yellowish solid substance soluble in water,
- It was also used as a methemoglobinizing substance in cyanide poisoning,
- Additive for smoking meat, for cigarette papers, for fuel,
- Lethal dose after – 4g .
Nitrates[edit | edit source]
Synonym: nitrates, -NO 3 ,
- In order to cause metHbemia, they must be reduced to nitrites by flora in the intestine,
- They are dangerous for infants (they have bacteria in the GIT higher - due to less acidic stomach contents),
- As little as 10 mg/l can be dangerous for infants,
- Others, chlorates, drugs – primaquine (antimalarial), phenacetin (analgesic).
Links[edit | edit source]
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Source[edit | edit source]
- BENEŠ, Jiří. Studijní materiály [online]. [cit. 24.02.2010]. <http://jirben.wz.cz>.
References[edit | edit source]
- PELCLOVÁ, Daniela. Nemoci z povolání a intoxikace. 2. vydání. Praha : Karolinum, 2006. 207 s. ISBN 80-246-1183-X