Post-mortem Toxicology

1. Post-mortem Toxicology Dr A J Jeffery MBChB MD FRCPath (Forensic) MFFLM Home Office registered forensic pathologist

2. 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

3. WHY TAKE TOXICOLOGY ?

4. 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

5. WHAT SAMPLES ARE APPROPRIATE ?

6. Samples • Blood (plain) (peripheral) • Blood (preserved) (peripheral) • Urine (plain) • Urine (preserved) • Fluoride – inhibits further alcohol production but won’t undo the damage already done. • Vitreous • Stomach Contents • Tissues • Liver (mid R lobe) • Skeletal muscle (eg psoas) (if embalmed buttock)

7. OBTAINING THE BLOOD SAMPLE

8. 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

9. Problem: MINIMAL FEMORAL BLOOD

10. 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

11. OBTAINING THE URINE SAMPLE

12. 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

13. Vitreous

14. WHAT DO THE TOXICOLOGISTS DO WITH THE SAMPLE ?

15. 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.

16. HOW TO INTERPRET THE RESULTS

17. General Considerations • Accuracy of reference ranges • Re-distribution – site matters! • Individual variation (e.g. renal disease) • Decomposition • Tolerance

18. 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

19. General Considerations • Re-distribution – site matters! • Individual variation (renal disease) • Decomposition • Tolerance

20. 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

21. 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

22. 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

23. 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

24. Alcohol

25. 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?

26. Alcohol • Acute alcohol toxicity • Ketoacidosis • Alcohol in combination with other drugs

27. Problems with Interpretation of Alcohol • Redistribution • Dealing with decomposition • Back calculations

28. Acute alcohol toxicity • How does it cause death? • Death – respiratory depression due to action on brainstem • UK legal driving limit? • Driving limit 80 mg/100ml • Less than 20 mg/100ml generally considered insignificant. • >30 =  higher skills • 30 – 50 = deterioration in 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 & 

29. 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.

30. What is ketoacidosis? • Can you explain why this happens?

31. 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

32. 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

33. Alcoholic vs Diabetic • How might you differentiate? • Urine glucose • HbA1c • 4 - 6.1%

34. 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

35. 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 Vitreous : Blood 1.23 : 1 1 : 0.81

36. Drugs of Abuse OPIOID AGONISTS SYMPATHOMIMETICS

37. Opioid agonists

38. Opioid agonists • Analgesia / euphoria / dysphoria • Respiratory depression • miosis

39. Morphine and other opioids • Morphine • Heroin (diamorphine) – IV, smoked, sniffed • Methadone (green liquid – oral or IV) • Pethidine, buprenorphine • ** CNS depression **

40. Findings • History / scene / paraphernalia • External • iv sites • Foam at nose / mouth • Limited & non specific • Pulmonary congestion and oedema • Stomach contents – methadone is usu green!

41. 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

42. Total morphine : Free Morphine • Gives some idea of time since administration • Eg in IV admin • 15 mins post admin 4 : 1 • 60 mins 9 : 1 Therapeutic Lethal_______ • Free morphine 10 – 100ng/ml 50 – 4000 ng/ml

43. 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

44. 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

45. 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

46. Opioids • Tolerance = V V important consideration • Eg. Prison release • Palliative care • Nb worth remembering that 10% of codeine will breakdown to become morphine. Therapeutic Lethal_______ • Free Codeine 30 – 340ng/ml >1600 ng/ml

47. Sympathomimetics

48. Sympathomimetics • Incr activity of adrenaline and serotonin • Adrenalin • Hypertension • Tachycardia • Mydriasis • Serotonin • Excitement • Hyperthermia

49. Stimulants • Cocaine • Amphetamine • Ecstasy • Other methamphetamines • Associated with subarchnoid haemorrhage • 80% of these assoc with aneurysms • Intracerebral haemorrhage • Associated with AVMs & hypertension

50. 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.