11 - Medico-Legal Aspects of Common Poisons Flashcards
Carbon monoxide sources
- Endogenous
- Incomplete combustion of fossil fuels and carbon-containing compounds
- Exposure to methylene chloride (found in paint stripper)
- Some drug therapy (phenytoin, phenobarbital -> increase breakdown of heme in the liver which produces carbon monoxide)
Carbon monoxide analysis
- Specialized analysis (not part of routine testing)
- Done for suicides, murders, industrial exposure, and fire victims
Carbon monoxide levels (% saturation)
- 1-10% = no detrimental effect
- 5-9% = smoker level
- 10-20% = slight headache, flu-like sx
- 20-30% = throbbing temples
- 30-40% = severe headache, weakness, dizziness, N/V, collapse
- 40-50% = retinal hemorrhages, increased respiration
- > 50% = convulsions, coma, death
Which patients are most susceptible to CO poisoning (more likely to die from lower concentrations)?
- Infants (high respiration rate)
- Those w/ lung disease
- Those w/ CV disease
- Elderly
- Anemics (b/c have less heme to transport oxygen)
Tx of CO poisoning
- Remove person from source of CO
- Hyperbaric oxygen (100% oxygen, normal air = 20%)
- Used if concentration is really high
- Breathing hyperbaric oxygen will decrease CO level by ½ in 40 minutes, whereas normal air would take 4 hours
CO analysis interpretation
- Must analyze whole blood sample (w/ hemoglobin) -> can’t use serum, plasma, or urine sample
- Putrefaction
- Fire victims -> bodies w/ severe burns have coagulated blood, so wouldn’t be able to do a sample on it; would likely use a liver sample
Forms of cyanide
- Hydrogen cyanide (HCN) -> colourless gas or blue-white liquid
- Cyanide salts (KCN, NaCN) -> white crystalline powder
- 2 mg/kg is enough to kill a person
Sources of cyanide
- Normal metabolism
- Cigarette smoking
- Fumigants, insecticides
- Electroplating industry
- Dyeing, printing, photography
- Combustion of N-containing compounds
- Cyanogenic glycosides
What happens to the body during cyanide toxicity?
- Enzymatic poison
- Attacks cytochrome system
- Prevents oxygen utilization at the cellular level (cytotoxic anoxia)
- Results in metabolic asphyxiation
Acute sx of cyanide toxicity
- Giddiness
- Stiffness in lower jaw
- Rapid, slow, irregular breathing
- Muscle twitching
- Palpitations
- Cyanosis
- Convulsions, coma
- Death due to respiratory arrest
- *Brain and heart are most sensitive to cyanide toxicity
Chronic sx of cyanide toxicity
- Exposure to small doses over a longer period of time
- Dizziness, weakness
- Congestion of lungs
- Conjunctivitis
- Loss of appetite, weight loss
- Mental deterioration
Cyanide poisoning treatment
- Body can detoxify cyanide on its own
- CN -> SCN- (via rhodanese enzyme) -> inefficient system, can be sped up by adding an exogenous source of sulfur (ex: amyl nitrite, sodium nitrite, sodium thiosulfate)
- Sodium thiosulfate is most effective, but slow to get started
Cyanide interpretation
- Analyze whole blood sample
- Post-mortem production of cyanide (can prevent by using sodium fluoride or freezing the sample)
What are inhalants?
- Breathable chemical vapours that produce psychoactive (mind-altering) effects
- Includes -> volatile solvents, aerosols, anesthetics, volatile nitrites
- Estimated that about 1000 substances are abused/ misused as inhalants
Examples of volatile solvents and common sources
- Ex: toluene, acetone, benzene
- Common sources = paint thinner, nail polish remover, household cement and glue, lighter fluid, gasoline
