Fundamentals of Analytical Toxicology. Robin Whelpton

Fundamentals of Analytical Toxicology

Sample Notes^a Heart whole blood (right ventricle) 20 mL unpreserved (normally qualitative toxicology only) Jugular vein whole blood 20 mL unpreserved (normally qualitative toxicology only) Peripheral whole blood 20 mL from femoral or other peripheral site ensuring no contamination from urine or from central or cavity blood. Collect one portion into 2 % w/v sodium fluoride and another into a plain tube Urine 20–50 mL if available (plain tube, no preservative unless a portion is required for ethanol measurement) Gastric contents^b 25–50 mL (plain bottle, no preservative; record the total weight or volume) Vitreous humour Maximum available, plain tube, separate specimens from each eye if feasible. Avoid excessive suction to minimize the risk of aspirating retinal fragments. Collect one portion into 2 % w/v sodium fluoride if for ethanol measurement Cerebrospinal fluid 5–10 mL, plain tube Pericardial fluid Maximum available, plain tube Synovial fluid^c Maximum available, plain tube Intra-osseous fluid Maximum available, plain tube Bile Maximum available, plain tube Liver and other tissues Liver 10 g (deep inside right lobe), other tissues 10 g as appropriate^d Scene residues^e As appropriate

^aSmaller volumes may often be acceptable, for example in the case of young children

^bIncludes vomit, gastric lavage (SWO, first sample), etc.

^cAlternative if vitreous humour not available

^dBecause there is little information on drug distribution within solid tissues in man, collection of approximately 10 g specimens from several sites from organs such as the brain is recommended if the whole organ is available

^eTablet bottles, drink containers, aerosol canisters, etc. should be packed entirely separately from biological samples, especially if poisoning with volatiles is a possibility

Table 2.6 Advantages and disadvantages of different sample types in analytical toxicology

Specimen	Advantage	Disadvantage	Comment
Blood (plasma/serum or whole blood)	Detect parent compound. Interpretation of quantitative data	Limited volume. Low concentrations of many basic drugs and some other poisons	Interpretation of quantitative results from post-mortem blood may be difficult
Dried blood spot on filter paper	If known volume of venous blood added, then easy to store and transport (room temperature)	Almost impossible to get accurate volume of blood without use of a pipette or special device. Need analyte to be stable on the paper	Advocated for collecting capillary blood, but capillary blood not venous blood
Urine	Often large volume.High concentrations of many poisons, but sometimes only metabolites detectable	Not always available. Quantitative data not often useful	Standard sample for substance misuse screening
Gastric aspirate (stomach contents, SWO, vomit, etc.)	May contain large amounts of poison, particularly if ingested	If available, variable sample. Limited use if exposure is by inhalation or injection	Ensure no cross-contamination of other specimens during transport/storage/analysis
Oral fluid	Non-invasive. Qualitative information on exposure to many drugs	Variable sample hence little use for quantitative work. Low concentrations of many analytes	Interpretation of quantitative results may be difficult
Hair/nails or nail clippings	Usually available even if decomposition advanced	High sensitivity needed. May only give exposure data for the weeks/months before death. Susceptible to external contamination	Easy to store (room temperature)
Exhaled air	Non-invasive. Large volume available	Need live patient. Analyte must be volatile or present as an aerosol	Mainly used to assess ethanol ingestion, carbon monoxide exposure, and monitor volatile anaesthetics
Scene residues (tablet bottles, aerosol cans, etc. near patient)	May contain large amounts of poison	May not have been the poison taken	Ensure no cross-contamination of other specimens during transport/storage/analysis
Vitreous humour	May be used instead of urine if latter not available	Limited volume but normally two specimens	Analysis may be valuable to help interpret post-mortem blood data for ethanol and for some other compounds
Additional tissues (liver, brain, lung, kidney, etc.)	May contain large amounts of poison.If available then large quantity	Interference in analysis.Difficult to prepare calibrators/QCs, assess recovery, etc. Quantitative data not always easy to interpret	Analysis may be valuable to help interpret post-mortem blood data

Box 2.2 Information that should accompany a request for general toxicological analysis

Name, sex, date of birth, date and time of death if appropriate, details of the sample(s) sent for analysis

Name, address, and telephone number of clinician/pathologist and/or coroner's/police officer requesting the analysis, and address to which the report and invoice are to be sent. A post-mortem (reference) number may also be appropriate

Circumstances of incident (including copy of sudden death report if available)

Past medical history, including current or recent prescription medication, and details of whether the patient suffered from any serious potentially infectious disease such as hepatitis, tuberculosis, or HIV

Information

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