ABFM Toxicology and Cause of Death Analysis 2 — Questions and Answers
Question 1: Which specimen is considered the gold standard for detecting drugs in postmortem toxicology due to its resistance to redistribution artifacts?
- Peripheral blood
- Vitreous humor (Correct answer)
- Central blood
- Urine
Correct answer: Vitreous humor
Vitreous humor is largely protected from postmortem redistribution and microbial degradation, making it highly reliable for toxicological analysis.
Question 2: A decedent is found with cherry-red lividity. Which toxicological finding would most support carbon monoxide poisoning over cyanide poisoning?
- Carboxyhemoglobin >30% (Correct answer)
- Elevated blood cyanide >3 mg/L
- Lactic acidosis on blood chemistry
- Elevated hydroxocobalamin levels
Correct answer: Carboxyhemoglobin >30%
Carboxyhemoglobin saturation above 30% is diagnostic of significant carbon monoxide exposure and distinguishes CO poisoning from cyanide, which does not elevate carboxyhemoglobin.
Question 3: Postmortem redistribution most significantly affects which class of drugs, leading to overestimation of antemortem levels?
- Water-soluble drugs with low protein binding
- Lipophilic basic drugs with large volumes of distribution (Correct answer)
- Polar acidic drugs excreted renally
- Hydrophilic drugs with narrow therapeutic indices
Correct answer: Lipophilic basic drugs with large volumes of distribution
Lipophilic basic drugs with large volumes of distribution (e.g., tricyclic antidepressants, methadone) concentrate in solid organs and redistribute postmortem into central blood.
Question 4: During autopsy, the liver is sampled for toxicology. Which analyte is liver particularly useful for quantifying due to its high concentration there?
- Ethanol
- Morphine
- Acetaminophen (Correct answer)
- Fentanyl
Correct answer: Acetaminophen
Acetaminophen undergoes hepatic metabolism producing a toxic intermediate (NAPQI), and its concentration in liver tissue can confirm hepatotoxic overdose even when blood levels are declining.
Question 5: Which parameter best differentiates acute ethanol ingestion from postmortem ethanol production by putrefactive organisms?
- Blood ethanol concentration alone
- Presence of ethanol in vitreous humor equal to blood levels
- Detection of n-propanol as a marker of fermentation (Correct answer)
- Urine ethanol concentration
Correct answer: Detection of n-propanol as a marker of fermentation
n-Propanol (1-propanol) is a byproduct of microbial fermentation and its presence alongside ethanol strongly suggests postmortem production rather than antemortem ingestion.
Question 6: A fatality involves a combination of opioids and benzodiazepines at individually sublethal concentrations. This is best described as which type of drug interaction in cause-of-death determination?
- Antagonism
- Pharmacokinetic induction
- Synergism (potentiation) (Correct answer)
- Tachyphylaxis
Correct answer: Synergism (potentiation)
Synergism or potentiation occurs when combined CNS depressants produce greater respiratory depression than either drug alone, a common polypharmacy cause of death.
Question 7: When interpreting a postmortem fentanyl blood concentration of 25 ng/mL in a known opioid-tolerant individual, the forensic pathologist should primarily consider:
- This level is universally lethal regardless of tolerance
- Tolerance significantly raises the threshold for lethality (Correct answer)
- Fentanyl concentrations above 10 ng/mL are always fatal
- Only urine confirmation is needed for causation
Correct answer: Tolerance significantly raises the threshold for lethality
Opioid tolerance raises the lethal concentration threshold substantially, so published reference ranges for naive individuals cannot be directly applied to tolerant users.
ABFM Toxicology and Cause of Death Analysis 2
Which specimen is considered the gold standard for detecting drugs in postmortem toxicology due to its resistance to redistribution artifacts?