Transcript Post-mortem Toxicology

Post-mortem Toxicology
DR A J JEFFERY
MBChB MD FRCPath (Forensic) MFFLM
HOME OFFICE REGISTERED FORENSIC PATHOLOGIST
Areas to Cover
 Why take toxicology
 What samples
 How to take them
 What does the toxicologist do with the samples?
 How to interpret the results – general considerations
 Alcohol
 Drugs of abuse
 Toxicology in other causes of death
 Other specimens
 Case examples
WHY TAKE
TOXICOLOGY
?
Why take toxicology ?
 To ascertain if the deceased was under the influence
of alcohol or drugs of abuse at the time of their
death.

RTAs / Accidental deaths / suicides
 To confirm or refute overdose / poisoning
 To confirm presence / levels of therapeutic drugs.
 Eg epilepsy / antidepressants
WHAT SAMPLES
ARE
APPROPRIATE
?
Samples




Blood
Blood
Urine
Urine

(plain)
(preserved)
(plain)
(preserved)
(peripheral)
(peripheral)
Fluoride – inhibits further alcohol production but won’t undo the damage
already done.
 Vitreous
 Stomach Contents
 Tissues
 Liver
 Skeletal muscle
(mid R lobe)
(eg psoas) (if embalmed buttock)
OBTAINING
THE
BLOOD SAMPLE
Femoral Vein Sampling
 Vein NOT artery
 Before evisceration
 Before urine sampling
 Ideal = tie off / clamp, then sample by wide-bore
needle below
 Routine = clean catch
 Ideal = don’t milk the leg
 Routine = required to gain sufficient sample
Problem:
MINIMAL FEMORAL
BLOOD
Insufficient Femoral Blood
 Take what ever you can in preserved tubes
 Subclavian = reasonable alternative
 Could take free-lying chest blood etc for screening
for the general presence of drugs
 Make sure you say where each sample has come from
 Obtain an alternative specimen
OBTAINING
THE
URINE SAMPLE
Urine Sampling
 Needle and syringe
or
 Open dome of bladder and aspirate with syringe
alone
 Presence of a catheter may be important
toxicologically as the urine may contain artefactually
high lignocaine due to catheter lubricant gel
Vitreous
WHAT DO THE
TOXICOLOGISTS
DO WITH THE SAMPLE
?
Analysis
 Screening (GC / Immunoassay)
 What classes of drug are present
 Confirmation (GCMS)
 Specific drugs found by breaking them down & looking at the
breakdown products.
 Quantification
 Technique may vary dependent on the nature of the drug being
analysed.
HOW TO
INTERPRET
THE RESULTS
General Considerations
 Accuracy of reference ranges
 Re-distribution – site matters!
 Individual variation (e.g. renal disease)
 Decomposition
 Tolerance
Accuracy of reference ranges
 Interpretation of absolute drug levels / Reference
ranges

Based on individual reports

Variable from lab to lab due to varying techniques

Need to consider the previous list
General Considerations
 Re-distribution – site matters!
 Individual variation (renal disease)
 Decomposition
 Tolerance
Redistribution
 Discovered with digoxin
 Most drugs that undergo
redistribution do so
because of their relative
lipid solubility.
 Due to


Loss of cell integrity
Diffusion
 GI tract – to adjacent
structures
 Through conduits – lymph
 Diffusion from bladder
Natural Disease
 Depends or route of administration
 1st pass / second pass metabolism
 Absorption
 With or without meal
 GI surgery
 Elimination / Clearance
 Renal impairment
 Liver impairment
Decomposition
 Significant redistribution
 Some drug levels increase
 Alcohol production by bacterial action
 Others degrade
 If there is a degree of decomposition make sure you
write it on the tox request
Tolerance
 Increasing doses required over time to achieve same
effects.
 What is lethal to a naïve user may have no effect at
all in a chronic user.

First dose deaths

People walking around and working with enough drugs on
board to kill an elephant!

Prison release deaths
Alcohol
Deaths due to Alcohol
 What alcohol related causes of death do you know?
 How might you classify them?
 Which specific toxicological causes do you know?
Alcohol
 Acute alcohol toxicity
 Ketoacidosis
 Alcohol in combination with
other drugs
Problems with Interpretation of Alcohol
 Redistribution
 Dealing with decomposition
 Back calculations
Acute alcohol toxicity
 How does it cause death?
 >30 =  higher skills
 Death – respiratory
 30 – 50 = deterioration in
depression due to action
on brainstem


 UK legal driving limit?
 Driving limit 80

mg/100ml

 Less than 20 mg/100ml
generally considered
insignificant.

driving
50 – 100 =  inhibitions /
laughter
100 – 150 = slurring,
insteadiness, poss nausea
150 – 200 = obvious
drunkenness, nausea
staggering
200 – 300 = stupor, vomiting,
coma
300 + = stupor, coma,
aspiration & 
Alcohol – fatal level or not?
 LD 50 = 400 mg/100ml
 Alcohol has symbiotic relationship with other drugs.
e.g.



< 200mg/100ml can be fatal if opioids are taken.
> 200mg/100ml can ½ the fatal dose of opioids
> 100mg/100ml may enhance heroin toxicity
 Ethyl glucuronide (minor breakdown product) in
urine if imbibed within 5 days of death.
What is ketoacidosis?
 Can you explain why this happens?
Ketoacidosis
 Brain can utilise ketone bodies when glucose is unavailable – fasting /
starvation
 Ketone bodies, formed by the breakdown of fatty acids and the de-amination of
amino acids.
 Ketoacidosis is an extreme and uncontrolled form of ketosis, which is a normal
response to prolonged fasting. In ketoacidosis, the body fails to adequately
regulate ketone production causing such a severe accumulation of keto acids
that the pH of the blood is substantially decreased.
 Alcoholic ketoacidosis



Metabolic acidosis
Malnutrition
Binge drinking superimposed on chronic alcohol abuse
Ketoacidosis
 Ketones:
 Acetone (can be produced pm)


<0.5 mg/100ml
Beta hydroxybutyrate (less likely to be raised artefactually)
<0.5 mmol/L
 1.26 – 47.2 mmol/L (assoc with fatalities)

 Causes
 Alcoholic ketoacidosis
 Diabetic ketoacidosis
Alcoholic vs Diabetic
 How might you differentiate?
 Urine glucose
 HbA1c
 4 - 6.1%
Calculations
 AVOID !
 Clearance
 10 – 25 mg/dl/hr ( about a unit an hour)
 In 10 hours you can clear ~ 100-200 mg/dl
 Alcoholics can clear 30 – 40 mg/dl/hr (due to training!)
 Widmark equation
 Used by some to predict amount of alcohol consumed
Decomposition
 70 – 190 mg/100ml reported as artefact
 Consider pm findings
 Look for other substances produced pm
 Use vitreous and urine as supportive evidence

These are relatively protected from redistribution

Normal ratios (if in equilibrium)

Urine : Blood
1.23 : 1
Vitreous : Blood
1 : 0.81
Drugs of Abuse
OPIOID AGONISTS
SYMPATHOMIMETICS
Opioid agonists
Opioid agonists

Analgesia / euphoria / dysphoria

Respiratory depression

miosis
Morphine and other opioids
 Morphine
 Heroin (diamorphine) – IV, smoked, sniffed
 Methadone (green liquid – oral or IV)
 Pethidine, buprenorphine
 ** CNS depression **
Findings
 History / scene / paraphernalia
 External
 iv sites
 Foam at nose / mouth
 Limited & non specific
 Pulmonary congestion and oedema
 Stomach contents – methadone is usu green!
Morphine / Heroin
 Heroin / diamorphine – synthetic morphine
derivative

Powerful opioid analgesic

Metabolised almost immediately (10 – 15 mins) to 6
monoacetyl morphine 6MAM and then within 24 hours to
morphine.


Presence of 6MAM is consistent with use within 12-24 hours
 Ie recent intake / top up injections
Acute alcohol intoxication potentiates the effects
 Total morphine : Free Morphine
 Gives some idea of time since administration
 Eg in IV admin
15 mins post admin
 60 mins

4
9
Therapeutic
 Free morphine 10 – 100ng/ml
:
:
1
1
Lethal_______
50 – 4000 ng/ml
Heroin
 A contaminate of street heroin is acetylcodeine
 Hence may have +ve codeine levels
 Most heroin deaths occur several hours after taking
the drug


Sleepy / snoring
May have time to metabolise drug despite irreversible
respiratory depression
Methadone
 Therapeutic
 75 – 1100 ng/ml
 Toxic
 200 – 2000 ng/ml
 Lethal
 400 – 2000 ng/ml
 Significant overlap
 Tolerance becomes very important
 Interpretation requires knowledge of drug history
 Long & variable T ½
Methadone
 Breakdown product – EDDP
 This is inactive
 Titration is important
 Many deaths occur during first few weeks of treatment
 Can cause respiratory depression at therapeutic doses
 Lipophilic so undergoes significant redistribution
 Even peripheral samples can be 2x in
and 3x in
Opioids
 Tolerance = V V important consideration
 Eg. Prison release
 Palliative care
 Nb worth remembering that 10% of codeine will
breakdown to become morphine.
 Free Codeine
Therapeutic
Lethal_______
30 – 340ng/ml
>1600 ng/ml
Sympathomimetics
Sympathomimetics

Incr activity of adrenaline and serotonin
Adrenalin
 Hypertension
 Tachycardia
 Mydriasis
 Serotonin
 Excitement
 Hyperthermia

Stimulants
 Cocaine
 Amphetamine
 Ecstasy
 Other methamphetamines
 Associated with subarchnoid haemorrhage
 80% of these assoc with aneurysms
 Intracerebral haemorrhage
 Associated with AVMs & hypertension
Findings
 Hearts of stimulant users tend to be heavier than




controls
Fibrosis
Contraction band necrosis
Accelerated atherosclerosis
Non specific pulmonary changes
 Crack cocaine smokers – prominent anthracosis esp
in alveolar macrophages & emphysematous changes.
Cocaine
 Naturally occurring plant alkaloid stimulant
 Snorted, smoked, cutaneous, injected
 Nb always consider in sudden death in the same way
that you might consider HOCM.
 Breakdown Products
 Benzoylecgonine
Inactive
 Methylecgonine
 Cocaethylene
As active as cocaine itself & indicative of alcohol
consumption at the same time
Cocaine Toxicity
 Less than 50 ng/ml cocaine is considered not to
produce measurable physiological effects
 T ½ can be as little as 40 mins
 Benzoylecgonine – 1-4 days in urine
 Toxic
 >900 ng/ml
 Lethal
 >1000 ng/ml
 Benzoylecgonine
 Lethal - >1000 ng/ml *
Cocaine
 But lethal nature not dose related
 Long term effects:
 Cardiovascular damage –
incr ischaemic event / Coronary Art thrombosis
coronary artery spasm
contraction band necrosis
fibrosis / sudden arrhytmia
myocarditis/cardiomyop/valvular/aortic
dissection/hypertensive crisis

Non cardiac -
Cerebral infarction / intracerebral haemorrhage
 So death can be attributed to cocaine even if not found in blood.
 Cocaine can decrease rapidly in unpreserved blood samples stored
at room temperature.
Cocaine, death & Excited delirium
 Excited delirium





Hyperthermia
Mental & physiological arousal
Excited, erratic & sometimes bizarre, violent behaviour
May have florid psychosis
May exhibit extra-ordinary strength
 Tends to result in sudden respiratory arrest


Blood cocaine and benzoylecgonine may be low but there is usually
concentration of benzoylecgonine within the brain indicating long
term use
Marked decease in D2 receptors in hypothalamus in psychotic
cocaine abusers.

D2 receptors play a role in temperature regulation
Amphetamine
 Prevalence second only to cannabis
 Synthetic stimulant
 Effects similar to cocaine
 Stimulate release of catecholamines, particularly
adrenaline
 Tolerance & dependence develop
 Absorbed by GIT, clinical effects commence within
20 minutes, last 4-6 hours.
Amphetamine
 Toxic
 >500 ng/ml amphetamine
 >1800 ng/ml methamphetamine
 Lethal
 Usu > 1000 ng/ml amphetamine
 But can be seen if >50ong/ml
 Usu > 10 000 ng/ml methamphetamine
Different Forms
 Amphetamine (Benzedrine, uppers, 'A', speed, whizz,
cranks, wake-up, sulph, hearts)
 Dextroamphetamine (Dexedrine, dex, dexy, dexies)
 Methamphetamine (ICE, crystal, glass, meth)
 Methylenedioxyamphetamine (MDA, EVE)
 3 ,4, Methylenedioxymethamphetamine (MDMA, ADAM,
Ecstasy, 'E', doves, Dennis)
Amphetamine
 Alcohol can potentiate effects on the heart.
 Rare toxic effects:
 Coma
 Cerebral vasculitis
 Cerebral haemorrhage
 Rhabdomyolysis
 D.I.C.
 Renal dysfunction
 Cardiac – long term users
 Accelerated coronary atherosclerosis
 Microvascular disease
MDMA / Ecstasy
 Amphetamine-like drugs
 3,4-methylenedioxymethamphetamine

Serotinergic and noradrenergic effects
• Hyperthermic effects
 Liquid ecstasy – GHB
 Gamma hydroxybutyrate
Other
Benzodiazepines
 Diazepam – 20 – 4000 ng/ml
 Nordiazepam – 20 – 1800 ng/ml

Need in the order of thousands to consider fatal.
Cannabis
 Cannabinoids


THC – tetrahydrocannabinol
Delta 9 THC carboxylic acid
 Rapidly distributed into tissues
 Blood levels drop >90% within 2 hours of intake
 THC can only be found within 4-12 hours post intake

>2 ng/ml suggestive of recent intake
 THC metabolites remain in


Blood – up to ~ 5 days
Urine – up to ~ 12-36 days
Volatile substance abuse - VSA
 Adhesives, aerosols, petrols, paint stripper, nail varnish




remover ….. amongst others
Increased risk taking behaviour
Accidental suffocation
CNS depression
Deaths thought to be due to cardiac arrhythmias


Sensitisation of myocardium to effects of adrenaline
Deaths often seen in association with physical exertion
 Blood sample must be in a glass tube with a foil top filled
to the top.
 Tie off whole lung and place within a nylon bag.

Head space
‘New’ Drugs
 Mephadrone
 ‘Cream’
Toxicology
IN
OTHER
CAUSES OF DEATH
Fire deaths
 Carboxyhaemoglobin
 Normal <10%
 Toxic 15 – 35%
 Lethal >48%
 Cyanide
 Normal < 0.1mg/L
 Develops within the potted blood sample if not preserved
Carbon Monoxide
 In an individual breathing air
 T ½ = 4 hours
 Breathing O2 in Hospital
 T ½ = 60 minutes
Therefore always consider survival time.
Therapeutic Drugs
 Anti-depressants
 Anti-convulsants
Overdose
 Aspirin
 Therapeutic


Hyper ventilation
Resp
Alkalosis
Enhanced
BBB transfer
Met
Acidosis
Body
Compensates
Toxic


20 – 100mg/l
Stimulation
of Resp
Centres
>150 mg/l
Lethal

>500 mg/l
 NB those on reg Rx (eg arthritis – 3g/day) – 44-
330mg/L

T ½ up to 36 hours in massive OD
Findings
 Pm
 Blood stained gastric content / frank haematemesis
 Rarely skin petechiae
 Mucosal gastric erosions
 Malaena if survival sufficiently long
 Petechiae through other organs due to anticoagulant effect

esp parietal pleura and epicardium
 Paracetamol
 Therapeutic


Toxic


10 – 20 mg/l
>150 mg/l
Lethal

>160 mg/l
Other samples of interest
IMMUNOLOGY – ANAPHYLAXIS
BIOCHEMISTRY – DIABETES
Immunology - Anaphylaxis
 Secure ante-mortem samples
 Needs to be peripheral as mast cell rich organs can
release tryptase after death.
 Serum (plain tube – spun down)
 Mast cell tryptase ( = more specific)
 Specific IgE
 Make sure you give details of any suspected cause

Available for venoms, foods, medicines, contrast agents, latex…….
Mast cell tryptase
 T ½ during life is ~ 2 hours so may be unhelpful if they have been resuscitated
and have survived and die later ( usu from cerebral anoxia)
 Antemortem!!!
 Tryptase is a sensitive marker for mast cell activation
 High levels will be found post severe anaphylaxis
 Levels are not raised in local allergic reaction eg rhinitis
 Can be raised in pure asthma deaths but not of the same order of magnitude
 Slight increases can be seen in


non-anaphylactic mast cell degranulation – EG opioids for chest pain
Trauma – disruption of mast cell rich tissues
 Unless grossly elevated – interpret with caution
 In presence of suggestive history and absence of pm findings it may provide
confirmatory evidence.
 Normal Levels:

IgE
MCT

MCT can be produced pm

0 – 122 kU/L
2-14 mg/L
Biochemistry - Diabetes
Vitreous is best for biochem as most blood is already haemolysed
 Glucose drops significantly after death
 Bacterial metabolism
 Drops even in vitreous
 So low glucose ≠ hypoglycaemia
 It is not possible to diagnose hypoglycaemia accurately at pm.
 A high vitreous glucose virtually rules out hypoglycaemia as one can assume it was
the same or higher in the antemortem period unless peri-mortem dextrose admin


HbA1c – heparinised sample

Insulin
 If endogenous the body has to cleave C peptide from pro-insulin to make active
insulin.
 If exogenous the insulin is already cleaved and so they will have no C peptide.
Case Examples
Case 1
60 yr old male, in house fire, extensive burns, no suspicious injuries, no
soot in airways or stomach.

Ranges
Norm
Tox
Leth

CO = 40%
<10%
15-35%
>50%

Cyanide = 0.5 mg/L
<0.1mg/L

Paracetamol
 6mg/l
10-20mg/l
>150mg/l
>160mg/l

Codeine
 56ng/ml
30-340ng/ml
>1600ng/ml

Morphine (free)
 <5ng/ml
10-100ng/ml
50-4000ng/ml
Case 2
 30 year old female found on floor with green fluid trailing
from corner of mouth

Ethanol





Blood
181 mg/100mls
Urine
244 mg/100ml
 Ethylglucuronide present in urine
Acetone
negative
Methanol negative
Isopropanol negative

What effect might you expect?
What caveat would you include?

Is this likely to by PM alcohol production?


Ranges:
Normal
Toxic
Lethal

Methadone
75-1100ng/ml
 413 ng/ml
 EDDP = 276 ng/ml
200-2000ng/ml
400-2000ng/ml

Amphetamine
 471 ng/ml
>500ng/ml
>1000ng/ml

Diazepam
 21 ng/ml
 Nordiaz = 73ng/ml
>5000ng/ml
>30 000ng/ml
 Cause of Death??
20-4000ng/ml
20-1800ng/ml
Case 3
 Chronic alcoholic found dead at home, head injury
consistent with fall to the ground.

Ethanol





16 mg/100mls
72 mg/100mls
25 mg/100mls
145 mg/100mls
Supports ante-mortem consumption
Acetone




Blood
Urine
Vitreous
Stom Cont
Blood
Urine
Vitreous
3mg/100mls
9mg/100mls
4mg/100mls
Methanol & Isopropanol

2mg/100mls of each in Blood, urine and vitreous
Ketone
But
Can be produced pm
What else do you want to know?
 Urine Glucose – negative
 Vitreous glucose – unrecordable
 Urine Ketones – present
 Blood Betahydroxybutyrate 2.3 mmol/L (<0.5 mmol/L)
more specific than acetone
 HbA1c – 12.1% (4.0 – 6.1%)
 Urine ethyl glucuronide - present
Diabetes – reconsider
urine alcohol
Case 4
Decomposed @ home on sofa with drug paraphenalia around
LIVER
Homogenate
 Ethanol
 Methanol
0.88 mg/g
Not detected
Not detected
 Isopropanol
Not detected
 Acetone

General drug screen by gas chromatography – mass spectrometry (GC-MS)
Liver homogenate:
Morphine, cocaine metabolites, flupenthixol and metabolites, paracetamol,
chlorpromazine metabolites and cotinine detected detected

Liver Tissue Homogenate Quantitative Analysis by Gas chromatography –
Mass spectrometry (GC-MS)
Cocaine
= <0.02 ug/g
Benzoylecgonine = 0.28 ug/g
Methylecgonine = 0.26 ug/g
Cocaethylene
= 0.42 ug/g
Morphine (free) = 1.05 ug/g
Morphine (total) = 1.50 ug/g
 Was it worth doing if the concentrations mean
nothing?
COMMENTS

The external examination showed an advanced state of decomposition with no evidence
of injury to suggest involvement of another individual.

Within the limits imposed by the degradation of the tissues, the internal examination
showed no apparent pathology which could have caused or contributed to death.

Interpretation of toxicological results is complicated in cases where the individual has
been dead for some time. Drug levels are altered after death by diffusion of the
substances throughout the body (post-mortem redistribution) and certain substances are
produced or degraded in the post-mortem period. As such, it would be unreliable to draw
conclusions from the drug concentrations themselves. However cocaine and morphine
are not produced endogenously by the body and so their presence indicates that cocaine
and morphine (possibly heroin) were taken by the deceased. Alcohol can be produced by
the body after death but the presence of cocaethylene would suggest that alcohol and
cocaine were used concurrently.

The exact levels of the fore-mentioned drugs within the body at the time of death cannot
be determined with any accuracy. However, we feel that their presence, along with the
drug paraphernalia noted in the vicinity of the body and the absence of identifiable
natural disease is significant. Based on the above information, we are of the opinion that,
on the balance of probabilities, death was in keeping with polydrug toxicity.

The information given within this report represents our understanding of the views,
opinions and circumstances of this case based on the information that we have received
to date, either in writing (all forms) or by oral communication. We recognise that in
part this may reproduce or rely upon witness statements, oral communications or
hearsay evidence of second parties and that the information given to us by others may
or may not be factually correct at the time of our consideration.

We reserve the right to reconsider any aspect of this report should further factual
information arise that contradicts the information provided at the time of the postmortem examination, upon which we have based our interpretations.
Cause of Death
Ia. In keeping with polydrug toxicity
Confounding Factors
Considerations
Ask Yourself
 Arterial vs venous variation
 Where was it from?
 Continuing gastric residue




absorption
Redistribution
Post-mortem production or
degradation
Tolerance
Limited reference range data


Vitreous / blood / urine
Site
 Was it appropriately preserved
 Is there decomposition?
 Is it a drug prone to
redistribtution / pm production
 Do you know about their drug
taking / drinking habits
In Practice
 Seek a drug history from coroner’s officer
 Always give the toxicologists as much info as you
have
 If you are looking for a specific substance – tell them
as it might not be on their routine screen
 Appropriate specimens / appropriate site
 If tox is important talk to coroner’s officer about
accessing ante-mortem bloods.
Resources
 http://www.dundee.ac.uk/forensicmedicine/
 C. Baselt, Disposition of Toxic Drugs & Chemicals in
Man.