Acute chemical intoxications

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Acute chemical intoxications systemically toxic
chemicals

• Paide 4.11.03 Tiina Santonen

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• Chemical asphyxiants
• Carbon monoxide
• Cyanides
• Hydrogen sulphide
• Methaemoglobinemia inducing substances
• Anticholinesterase inhibitors
• Organic solvents

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Carbon monoxide

• the most common cause of chemical intoxication in
  industry
• mechanism of action binds to haemoglobin at
  200-300 higher affinity than oxygen and forms
  carboxyhaemoglobin, but it also enters the
  tissues and attacts the cytochrome system

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Adapted from Rom W.N. Environmental and
Occupational Medicine, 3rd ed., Philadelphia,
1998.
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• smoking causes 3-8 COHb
• Finnish OEL 30 ppm gt 4 COHb
• IDLH 1200 ppm /30 min

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• The amount of carboxyhaemoglobin is highly
  dependent on the physical activity of the exposed
  individual
• COHbCOair x K x T
• Kconstant for physical activity, at rest
  K0.018, in light work K0.048
• If the air concentration of CO is 1 (10000
  ppm), 50 COHb level will be reached at rest in
  16 min, in light work in 6 min

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• Individual susceptibility people suffering from
  heart and lung diseases at highest risk
• Pregnancy!
• methylene chloride forms carbon monoxide in the
  body

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Carbon monoxide poisoning -treatment

• diagnosis anamnesis, status, blood
  carboxyhaemoglobin content (does not necessary
  correlate with the severity of symptoms!)
• monitoring of ECG, electrolytes and arterial
  blood gases
• treatment 100 oxygen hyperbaric oxygen
  (in special cases)

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Hydrogen cyanide and Cyanide salts

• Cyanides are used e.g. in the metal finishing
  operations, HCN is formed also in fires
• Cyanide ion (CN- ) inhibits the cellular
  respiration by binding to mitochondrial
  cytochrome oxidases
• affects all organs, however, the organs with high
  oxygen demand most susceptible

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• Hydrogen cyanide bitter almond-like odor
• Finnish OEL 10 ppm / 15 min
• IDLH for hydrogen cyanide 50 ppm / 30 min
• symptoms of cyanide poisoning are due to the
  decreased tissue oxygen utilisation and became
  evident mainly as CNS symptoms like weakness,
  dizziness, nausea, headache, confusion,
  convulsions and unconsciousness

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• Note cyanide salts like KCl, NaCl, Ca(CN)2 are
  well absorbed through the skin
• Treatment of cyanide poisoning
• First aid administration of 100 oxygen, amyl
  nitrite inhalation
• Hydroxycobalamin 5 g i.v. during the 30 minutes
• (sodium nitrite or 4-dimethylaminophenol
  4-DMAP)
• sodium tiosulfate 25 50 ml
• (dicobalt edetate in severe cases)
• Education of the workers for safe handling!

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Nitriles

• Nitriles like acrylonitrile deliberate cyanide in
  the body
• acrylonitrile is used e.g. in the manufacture of
  acrylic fibers, ABS-plastics, latexes and nitrile
  rubber
• acrylonitrile IDLH 85 ppm, well absorbed through
  the skin, high vapour pressure
• symptoms of poisoning are equivalent to those of
  cyanides
• treatment of poisoning is equivalent to that of
  cyanide poisoning

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Hydrogen sulfide

• formed during the decomposition of organic
  materials exposure to H2S may occur e.g. in
  sewage treatment plants, cellulose industry)
• odor of rotten eggs at low concentrations (odor
  threshold 0.008 ppm), however, at high
  concentrations the sense of smell is paralyzed

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• highly toxic, inhibits cellular respiration like
  cyanide
• Finnish OEL 10 ppm / 15 min
• IDLH 100 ppm /30 min
• symptoms of poisoning resemble those of cyanide
  poisoning
• treatment 100 oxygen
• (amyl nitrite, sodium nitrite, 4-DMAP)

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Methaemoglobinemia inducing agents

• methaemoglobinemia oxidation of haemoglobin
  Fe2 to Fe3 gt inability of haemoglobin to carry
  oxygen
• many aromatic amino and nitro compounds (e.g.
  aniline, nitrobenzenes), and nitrites and nitric
  oxide may induce methaemoglobinemia

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• Physical properties of the compound determine the
  possible routes of exposure
• For example sodium and potassium nitrites are
  solid compounds, which do not evaporise at normal
  conditions, but amyl and isobutylnitrites are
  liquids with a vapour pressure and may evaporise.
  Aniline and nitrobenzenes are liquids which may
  evaporate and be absorbed through the skin (good
  fat-solubility)

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• Symptoms of methaemoglobinemia
• cyanosis (15-25 methamoglobin), more severe
  cyanosis and CNS symptoms at 40 level of
  methaemoglobinemia
• treatment of methaemoglobinemia
• 100 oxygen
• Monitoring of the methaemoglobin levels
• 1-2 mg/kg 1 methylene blue i.v. in severe
  poisoning cases (usually caused by ingestion)

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Anticholinesterase inhibitors
-organophosphorus pesticides and nerve agents
like sarin and tabun
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Organophosphorus pesticides

• e.g. azinphos-methyl, dichlorvos, dimethoate,
  fenitrothion, azamethiphos, isophenphos,
  chlorpyriphos
• used as insecticides
• depending on the use, the main route of exposure
  to organophosphates is the skin, but also
  inhalation exposure may occur

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Organophosphorus pesticides

• irreversible inactivation of acetylcholinesterase
  gt increase in acetylcholine levels in nerve
  endings
• gt Cholinergic symptoms which include salivation,
  sweeting, lachrymation, miosis, bradycardia,
  hypotension (muscarinic effects), muscle spasms,
  convulsions and finally paralysis (nicotinic
  effects)

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Organophosphorus pesticides

• treatment of poisoning
• - the patient should be kept at rest
• -supportive care oxygen, ventilation
• -treatment of convulsions with diazepam
• -antidote atropine 2 mg every 5-10 min
• -obidoxime 250 mg i.v. reactivates
  acetylcholinesterase
• biological monitoring measurement of blood
  acetylcholinesterase activity

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Organic solvents

• aliphatic and aromatic hydrocarbons, halogenated
  hydrocarbons, alcohols, ketones, ethers, esters
• toxicity varies
• generally may cause CNS depressant effects, some
  of them may sensitize cardiac muscle for
  catecholamines and cause arrhytmias
• Lipid solubility affects the toxicity
• Abusers!