Postmortem Forensic Toxicology

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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.

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