Postmortem Forensic Toxicology
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Transcript of Postmortem Forensic Toxicology
Postmortem Forensic Toxicology Outline Definitions and purpose
of postmortem tox
Samples of forensic interest Pitfalls in postmortem toxicology
Interpretation of results Outline Definitions and purpose of
postmortem tox What is postmortem forensic toxicology? What are the
boundaries of postmortem forensic toxicology and the role of the
toxicologist in postmortem cases? Samples of Forensic Interest What
samples are the most relevant to the forensic toxicologist?
Handling and storage of samples How should postmortem forensic
toxicology samples be stored and handled? And why should we care
about how postmortem forensic toxicology samples are stored and
handled? Pitfalls in postmortem toxicology What are some of the
most common problems in postmortem forensic toxicology?How do
factors such as putrefaction, decomposition and redistribution of
drugs after death affect the ability of the forensic toxicologist
to draw conclusions? Interpretation of results What are the
limitations of the toxicologist in reporting results from
postmortem blood samples? What are some of the interesting pieces
of information that the toxicologist is able to give to the
pathologist in order to help them determine cause and circumstances
of death - as examples - discuss acute v. chronic ingestion of
drugs and identify pathological changes that occur following drug
overdose. Postmortem Forensic Toxicology
The analysis of drugs or poisons specimens collected during an
autopsy How might one define postmortem forensic toxicology? In
terms of purpose: The purpose of postmortem forensic toxicology is
to perform qualitative and quantitative analysis for drugs and
their metabolites, and poisons such as metals, carbon monoxide, and
volatile substances in human fluids and tissues collected after
death. The postmortem forensic toxicologist will then evaluate the
role of drugs or poisons as either determining factors or
contributory factors in the death of the individual.This includes
interpretation as to what the physiological effect at time of death
might have been (e.g. acute toxicity such as respiratory
depression) and/or what the behavioural effect at the time of death
may have been (e.g. impairment leading to drowning, motor vehicle
collision or other traumatic cause of death). What Can The
Determine? the presence or absence of a drug or poison in a
submitted sample the amount of drug or poison that is present in
the submitted sample Two important definitions - qualitative versus
quantitative analysis. Qualitative analysis simply determines the
presence or absence of a drug or poison in a submitted sample,
basically answering the question was this person exposed to a drug
or poison? Quantitative analysis actually determines the amount of
drug or poison that is present in the sample.In other words, you
are determining the quantity of drug that is present this is a
memory tool to remember the difference between quantitative and
qualitative analysis (determining quantity is quantitative
analysis). Quantitative analysis is always preferable as it is
difficult to make a meaningful interpretation based solely on the
presence or absence of a drug or poison.However, in some situations
qualitative analysis may be all that is meaningful due to the
nature of the submitted sample, or qualitative analysis may be a
useful starting point in order to direct further work. For example,
many initial drug screens are qualitative in their analysis; it is
the confirmatory method that is quantitative in its nature. Some
Examples Types of cases: Suspected drug intoxication cases
Fire deaths Homicides Driver and pilot fatalities Therapeutic drug
monitoring Sudden infant death (SIDS) These are the types of cases
that typically fall into the realm of postmortem forensic
toxicology. Unexplained deaths, with no apparent cause (often
suspected to be drug intoxication cases) as well as those that are
strongly suspected of being drug intoxication cases. Fire deaths
measurment of toxic gases such as carbon monoxide and cyanide which
may be inhaled during a fire.Furthermore, drugs may be implicated
as having incapacitated a victim, thereby preventing their escape
from a fire. Homicides homicidal poisonings themselves, are rare
but many homicide cases are related to drug use and drug abuse.
Driver and pilot fatalities where drug impairment may help
determine the cause of a crash. Other traumatic causes of death
will also require postmortem toxicology analysis (such as
drownings, falls) Therapeutic drug monitoring for example,
determining whether an individual with a seizure disorder has been
compliant in their medication use. SIDS by definition, SIDS is a
diagnosis of exclusion. Therefore, toxicology must be comprehensive
in these case to rule out any other cause of death. Samples of
Forensic Interest Issues in Specimen Collection
Selection sites: Multiple, varied sites of collection Collection
Appropriate method of collection Adequate volumes for analysis
Storage and handling Important to ensure results are accurate and
interpretations are sound In postmortem forensic toxicology, the
onus for specimen collection lies entirely on the pathologist
performing the autopsy.Since it is out of the toxicologists hands,
we can only hope that the pathologist has properly selected the
most appropriate samples for analysis and collected them using good
technique. In terms of selection, in the most general sense, the
pathologist should collect samples from a variety of sources
(example blood, urine, liver, stomach contents,hair) and should
collect them in sufficient quantity for analysis. We will further
discuss which samples are the best samples for analysis and
ultimately for interpretation of findings in postmortem cases.For
example, well talk about how some blood sampling sites are
preferable over others. Method of collection is also important.Has
the pathologist performed a full autopsy or only an external
autopsy? In the case of an external autopsy, there is a danger that
the pathologist, in attempting to collect a heart blood sample may
actually be sampling pericardial fluid. For interpretive purposes
the ideal toxicological blood sample is a specimen that is obtained
from a ligated vessel immediately after death (in other words, the
vein should be selected, clamped off and then sampled. In reality,
most autopsy samples do fall short of this ideal. Another issue is
adequacy of collection comprehensive drug testing may require 20 30
mL of blood, so the pathologist should ensure they have collected
enough sample to meet the needs of the investigation. Storage and
handling are also important aspects of specimen collection.Well
talk about some of theconditions under which samples for toxicology
are stored and some of the criteria under which samples should be
stored. Typical autopsy specimens
Blood Urine Stomach contents Bile Liver Hair Vitreous humor:the
transparent jellylike tissue filling the eyeball behind the lens.
Blood Antemortem ideal blood sample
Postmortem blood is not truly blood Anatomical site of collection
at autopsy should be noted The best possible blood sample, even in
postmortem forensic toxicology is an antemortem blood sample. In
the case of postmortem forensic toxicology, this antemortem blood
sample would ideally be a blood sample that is collected just prior
to the expiration of the patient.Occasionally these samples are
available - for example, in cases where the deceased was rushed to
hospital and where blood was collected in the hospital emergency
room. What we are usually faced with, however, is an analysis in
postmortem blood samples.Something to keep in mind is that
postmortem blood is not truly blood. It may look like blood - but
in fact it is not - it is a fluid, from the vasculature that is
collected after death.Postmortem blood however has already begun to
break down and hemolyze and is not the same as an antemortem blood
sample. As will become clear through discussions of the limitations
and pitfalls of postmortem forensic toxicology, the anatomical site
of collection at autopsy should be noted and MUST be accurate (for
an appropriate interpretation of the blood drug concentrations).
Example: heart blood collected from a patient who was an organ
donor and whose heart was taken for transplantation purposes in
hospital. Central sites Peripheral sites Other sites Heart Femoral
Iliac
Subclavian Other sites Head blood Hematoma blood Subclavian Heart
Iliac Femoral Examples of central blood collection sites and
peripheral blood collection sites.Ideally, blood should be
collected from both a central site, such as from the chambers of
the heart in addition to one or more samples being collected from a
peripheral site.The most common peripheral sites of blood
collection are femoral, iliac, and subclavian (emphasis on
femoral). [No, students do not need to know exact location of these
veins in the body, this picture is for reference only.] Other sites
of blood sample collection: Head blood rarely seen in adults, but
is not an uncommon site of selection in babies, especially since in
infants it is difficult to obtain blood from the peripheral sites
and blood volume of the heart is small. Hematoma blood a hematoma
is a blood clot, formed extravascularly (outside the circulating
blood system). Because it is outside the blood system, any drugs or
poisons that are contained in the hematoma are actually protected
from metabolism.This can be important in providing information as
to what drugs were present in the system at the time of hematoma
formation. Analysis of hematoma blood has has proven especially
useful with alcohol Hematoma Hematoma: a solid swelling of clotted
blood in the tissues
Protected from metabolism Analysis will indicate what drugs were
present in the blood at the time ofthe hematoma was formed Hematoma
case example A 26 year old man was found dead at the bottom of a
staircase.Death was due to physical injuries. Question as to
alcohol use prior to fall down stairs No urine available at autopsy
Alcohol not detected in femoral blood Alcohol in hematoma blood 150
mg/100 mL The deceased had been drinking prior to receiving the
head trauma. The deceased had survived for several hours after the
injury. For example These results indicate that the deceased had
been drinking prior to receiving the head trauma.Since ethanol is
detected in the hematoma, but not in the femoral blood, you can
also conclude that this individual survived for a substantial
period of time AFTER receiving the head trauma but BEFORE death
occurred.In the case of alcohol, the rate of elimination of alcohol
from the blood is very well know and I can predict that this
individual would have had to survive between 7 and 15 hours after
hematoma formation in order to clear the femoral blood of alcohol.
Caution:Hematomas may not form immediately upon receiving an
injury.Therefore this hematoma alcohol concentration will not
necessarily indicate the BAC at the time of the accident.more
appropriate to state the hematoma alcohol concentratoin indicates
the BAC at the time of hematoma formation. Hematoma Caution: There
may be a delay between the incident which resulted in hematoma and
the actual formation of the hematoma Therefore, this alcohol
concentration does not necessarily indicate the BAC at the time of
the fall down the stairs. Urine Produced by the kidneys Blood
filtered by the kidneys
Stored in the bladder until voided the presence of a drug in the
urine of an individual indicates that some time prior to death the
drug or poison was present in the blood of the individual Urine is
produced by the kidneys as a result of blood filtration.Along with
other wastes, drugs and their metabolites are filtered by the
kidneys and are contained in urine.Urine, is stored in the bladder
until voided.It may sound weird to think of it his way but urine,
since it is stored in the bladder is actually outside of the body
and it is no longer subjected to metabolism. Since urine is stored
for a period of time before it is expelled, the presence of a drug
in the urine does not necessarily mean the drug was present in the
blood at the time of death.It simply means that some time prior to
death the drug or poison was present in the blood. In this way,
urine analysis in isolation of blood analysis is of limited value.
Stomach contents Visual examination may reveal tablets
Drugs that have been orally ingested may be detected in stomach
contents Caution: drugs administered by other routes may also
diffuse into stomach contents from the blood Useful for directing
further analysis A portion of the stomach contents are typically
collected at autopsy.Stomach contents may contain unabsorbed
poisons, tablets, capsules, caplets which may be intact and
visible. These can be removed from the stomach contents,
photographed, and identified. Drugs in the stomach contents do not
necessarily indicate oral ingestion! Many weak bases are subject to
secretion into the gastric contents due to the pH gradient between
plasma and the stomach. Ion trapping in the stomach produces very
high concentrations of these agents, even after intravenous or
other non-oral routes of administration. Thus the finding of even
appreciable amounts of a basic drug in the gastric contents is not
a reliable indication of oral ingestion. Can you quantify stomach
contents to determine if a person has taken a drug overdose?
Stomach contents are not homogenous in their nature. Correct
procedure of collecting stomach contents is for the pathologist to
ligate the stomach, remove it from the body, remove all stomach
contents, mix thoroughly and provide a small quantity to the
toxicology lab again this is rarely, if ever, done. If stomach
contents were collected properly, quantitation may be valid and may
be usefulhowever, in light of the fact that stomach contents are
typically a scooped, non-homogenous sample, it is not acceptable
practice to quantify the contents and make any valid interpretation
from the results. Case Example A 26 year old woman is found dead in
bed
Numerous medications in her home: Amitriptyline, Oxycodone,
Morphine, Paroxetine, Diphenhydramine, Pseudoephedrine,
Phenobarbital, Codeine, Temazepam, Diazepam Only 3 mL of blood
collected at autopsy Analysis of stomach contents: Amitriptyline:
detected Nortriptyline: detected Point out that 3 mL of blood is
not a lot of blood for analyses in fact, probably only enough blood
to perform one or two quantitative analyses. Liver Drug metabolism
occurs in the liver
Both parent compounds (main drug) and metabolites (what the drug
breaks down to) may be present in higher concentrations in the
liver than in the blood ease of detection Limitation is that drugs
are not uniformly distributed throughout the liver confounds
interpretation A sample of liver (not the whole liver) is also
typically collected at autopsy and submitted to the tox lab. Liver
is the main drug metabolizing organ.As such, most drugs and poisons
that enter the blood stream will travel to the liver for
biotransformation.Both parent compounds (the drug that is ingested)
and their metabolites may not only be present in the liver, but may
also be present in higher concentrations than in the blood this may
help to identify drugs that are present in quantities that are
below detection limits in the blood. Quantitative analysis of liver
can be performed, however it is very difficult to make an
interpretation with any certainty from liver analysis.Drugs are not
uniformly distributed throughout the liver and therefore, where you
sample the liver for drug analysis may have an effect on the
quantity of drug that is identified. Bile Digestive secretion
Continuously produced by the liver
Stored in the gallbladder Qualitative - the presence of a drug in
the bile of an individual indicates that sometime prior to death,
the individual was exposed to the drug Bile is another sample that
is often collected at autopsy. Bile is a digestive secretion that
is continously produced by the liver and stored in the gallbladder.
[Not the policy of the CFS tox lab to analyze bile samples];
however some labs do perform analysis in bile and some labs also
quantify the amount of drug in bile (although I would caution that
bile rarely has a quantitiative value).Since it is produced by the
liver, it is similar in respect to the liver samples in that
concentrations of drugs in the bile are usually greater than
concentrations in the blood.Therefore the duration of detection of
a drug may be increased in the bile compared to the blood. As with
any quantitative analysis, however, the presence of a drug in the
bile simply indicates that sometime prior to death the individual
was exposed to the drug. Vitreous humor Fluid that occupies the
space between the lens and the retina of the eye. Useful in cases
where decomposition is advanced, body is exhumed or in fire deaths
Limitation is blood:vitreous ratio may not be known Vitreous humor
is in a protected position behind the lens of the eye.Because of
this protected position, it is isolated from putrefactive
processes, from charring and from trauma for example, the vitreous
humor can be obtained intact even if a corpse has been extensively
burned or damaged.Blood is very susceptible to postmortem changes
(more on this later) however the vitreous fluid is less susceptible
to these effects, particularly because it is likely to be free from
microorganisms. Particularly useful for determining alcohol
concentrations and may be useful for determining some drug
concentrations - depending on whether or not the blood:vitreous
ratio of the drug is known. Hair Recent specimen of interest
Metabolism does not occur in hair
Can provide a historical record of drug or poison exposure Pros and
cons of hair analysis still being uncovered racial variability?
Hair analysis has, in recent years, become a new interest in
postmortem forensic toxicology.Drugs and poisons are stable in hair
that is, they are not subject to metabolism or other non-enzymatic
degradation. Since hair grows at a predictable rate (generally 1
cm/month) hair can be used to provide a historical record of drug
or poison exposure.Procedure is to chop a hair sample into 1 cm
increments and analyze them separately to track drug exposure over
a long period of time (as long as the hair will allow, basically).
Pros and cons of hair analysis are still being uncovered for
example there have been studies that have shown racial variability
in the binding of drugs to hair. It is a developing area of
research in forensics right now [not something that we at the CFS
do] Case Example 30 year old woman, previously in good health
Poklis, A Abstract SOFT, Dearborn, Michigan. 30 year old woman,
previously in good health Nausea, vomiting, diarrhea, rash, fever
Weakness in hands and feet Guillian Barre? Hospitalized with
hypotension, seizures Misplaced laboratory result Arsenic!
Sequential hair analysis for arsenic showed chronic arsenic
poisoning over 8 month period A case of homicide by chronic arsenic
poisoning.The victim was a 30 year old mother of two who was in
excellent health until 8 months prior to her death when she
developed an apparent viral syndrome characterized by persistent
nausea, vomiting and diarrhea with low grade fever and rash.Within
2 weeks she developed a symmetrical parasthesia and weakness in
both her hands and feet.These symptoms progressed and resulted in a
diagnosis of Guillian Barre syndrome.During the following 2 months
she had several episodes of severe g.I. distress. Two weeks prior
to her death she was hospitalized for mental confusion, hypotension
and seizures.Her condition improved until she had dinner with her
husband after which she developed severe gastrointestinal
distress.Her condition then gradually deteriorated until death. A
misplaced laboratory result found after her death indicated an
arsenic concentration of 2.1 mg/100 mL. Non-biological
submissions
Used to direct analysis of biologicals (toxins or drug obtained)
May indicate the nature of substances that may have been ingested,
inhaled or injected Examples: Containers found at the scene
Syringes Unidentified tablets or liquids Case example of the
veterinarian who was found seated in a chair in his office,
intravenous infusion machine attached to empty I.v. bag, and needle
in left antecubital fossa.As a veterinarian, this individual had
access to a number of drugs analysis of the I.v. bag showed it to
contain phenobarbital and isopropanol.Blood analysis then revealed
a fatal blood concentration of phenobarbital and also a potentially
fatal level of isopropanol (although it was likely simply meant to
be the vehicle for the phenobarbital). Samples taken after
embalming
Methanol is a typical component of embalming fluid Most drugs are
soluble in methanol Embalming process will essentially wash the
vasculature and tissues Case Example A 72 year old woman, given
meperidine to control pain following surgery, later died in
hospital.The woman was in poor health and it is possible that death
was due to natural causes. However, coroner requests toxicology to
rule out inappropriate meperidine levels. BUT: Body had been
embalmed Liver and spleen submitted Storage and Handling Storage
and Handling Not feasible to analyze specimens immediately
Sample should be in well-sealed container Sample containers must be
sterile Use of preservatives and anti-coagulants Glass tubes will
break during the freeze-thaw cycle Storage of Samples Preservative
Anti-coagulants Sodium fluoride
Sodium citrate Potassium oxalate EDTA Heparin Not imperative for
postmortem blood samples Anticoagulants are not really necessary in
postmortem blood samples since the blood is hemolyzed! But any
changes that have occurred before the sample is put into the proper
container cannot be reversed. Pitfalls in Postmortem Forensic
Toxicology Decomposition Fewer samples available for
collection
Quality of samples is diminished Putrefaction produces alcohols
Ethanol Isopropanol Acetaldehyde n-propanol Fewer samples available
for collection - liquefication means fewer intact vessels from
which to sample Quality of samples is diminished - dirty samples;
interfering compounds during GC analysis Volume of
distribution
Volume of distribution is the amount of drug in the whole body
(compared to the amount of drug in the blood) If a drug has a large
volume of distribution, it is stored in other fluids and tissues in
the body Example: Digoxin p. 60, Principles of Forensic Toxicology
A 33 year old white female is admitted to hospital after taking 60
digoxin tablets An antemortem blood sample collected 1 hour prior
to her death indicates a blood digoxin level of 18 ng/mL Heart
blood digoxin concentration obtained at autopsy is 36 ng/mL
Example: Digoxin Postmortem increase in blood digoxin
concentrations is suspected to be due to the release of the drug
from the myocardium (heart) Postmortem redistribution
Coping with the problem of postmortem redistribution: Analysis of
both central blood and peripheral blood in cases where postmortem
redistribution may be a factor Compilation of tables to determine
average and range of postmortem redistribution factors for drugs
Incomplete Distribution
Site dependent differences in drug levels due to differential
distribution of drugs at death Has been noted in rapid iv drug
deaths Example: Intravenous injection of morphine between the toes
Fatal amount of drug reaches the brain Full distribution of the
morphine throughout the body has not occurred Femoral concentration
> Heart concentration Site dependent differences may be due to
incomplete distribution as opposed to postmortem redistribution The
difference between this and postmortem redistribution (in my mind)
is that there is a differential distribution in the drugs at the
time of death. The end