Preservation of Viscera for Analytical Toxicology

Following death there can be rapid changes in cellular biochemistry as autolysis proceeds, and drugs and other poisons may be released from their binding sites in tissues and major organs, also unabsorbed drug may diffuse from the stomach. Special care should always be taken in the selection of blood and tissue sampling site(s), the method of collection of samples, and the labelling of sample containers. (Image courtesy: rimkus.com)

There is substantial published evidence to show that for most drugs and poisons, including alcohol, there are important differences in their concentration in blood according to the time of specimen collection after death, choice of sampling site, method of sampling and volume of blood collected (Pounder and Jones 1990; Pounder 1993)

Blood for quantitative analysis
Blood for quantitative analysis (~ 5mL) should be obtained from two distinct peripheral sites, preferably left and right femoral veins, taken with care so as not to draw a large volume containing blood from more central vessels. The precise sampling site must be indicated on the label. Femoral blood can be taken by cutting the external iliac vein proximal to the inguinal ligament and milking the distal cut end into a plain 20mL sterile plastic container. Approximately 5mL of this blood should be placed in a fluoride/ oxalate tube containing 1% (w/v) sodium fluoride as a preservative.

Blood for qualitative analysis (screening)
An additional larger specimen of blood (~ 20mL) for qualitative screening should be taken from the heart (preferably right atrium or inferior vena cava) or if necessary from another convenient large vessel. This specimen should be placed in a plain 20mL sterile plastic container. The site of collection must be indicated on the label.

All organs to be preserved should be placed in separate sample containers to remove any chance of cross-contamination. Preservatives such as formalin must never be used. Sample containers should be clearly labelled.

Stomach tissue and contents
These materials may be useful in the investigation of oral cyanide poisoning, or in cases of rapid death where relatively large amounts of unabsorbed drug may be found in the stomach. In cases of suspected drug overdosage the entire stomach contents should be retained. If distinct tablets or capsules are observed in the stomach contents, these should be carefully extracted, and put in individual containers (e.g. plastic urine containers).

Liver
This tissue may be useful in certain complex poisoning cases. It is usual to take a portion of the right lobe of liver since it should be uncontaminated with bile and less affected by drug diffusion from the stomach; 100 grams are sufficient for most analytical purposes.

Brain
A portion of about 100g brain may be useful in the investigation of death due to gases or volatile substances (e.g. butane). The specimen should be placed in a glass specimen jar or nylon bag and deep-frozen prior to transport to the laboratory.

Lung
A portion of about 100g lung from the apex may be useful in the investigation of death due to gases or volatile substances. The specimen should be placed in a glass specimen jar or nylon bag and stored at 4oC prior to transport to the Laboratory.

Hair
Hair specimens may be useful in the investigation of death related to drug abuse (particularly opiates and methadone). Analysis of hair (approximate rate of growth 1 cm per month) is able to provide useful information concerning the chronicity of drug abuse, which is valuable in the interpretation of post mortem drug concentrations. If hair specimens are cut from the head, the proximal end should be clearly identified; the cut end tied with a piece of thread. However, the Laboratory does not currently provide a hair analysis service.

Vitreous Humour
A sample of vitreous humour is useful where a body has been exposed to heat, or if putrefaction is beginning to occur. This specimen may be especially useful for certain biochemical tests such as urea, creatinine, glucose, lactate and electrolytes; in addition to analysis of alcohols and heroin. More information on the collection of vitreous humour can be found in the recent reviews of Forrest (1993) and Knight (1995, 2002).

Nails and Bone
These specimens may be useful in the investigation of certain types of chronic metal poisoning, notably arsenic and lead.

DOCUMENTATION
The following documentation is desirable in every case:
· Details of the deceased, including name, age and date of birth.
· Relevant medical history, particularly with regard to prescribed medication and whether the deceased suffered from a serious infectious disease such as hepatitis, tuberculosis or AIDS.
· Circumstances surrounding the death, including date/time of death if known (particularly regarding deaths in hospital).
· Details of the name and quantity of the substance(s) thought to have caused death.
· A copy of the Pathologist's preliminary report indicating the likely cause of death.
· Details of the type of specimens obtained and the specific site of collection.
· Name, address and telephone number of the Pathologist and Coroner's Officer involved in the case.
· State HM Coroner's District and name, address and telephone number of HM Coroner (for billing purposes).
All of the above information is required to enable the Laboratory to provide an accurate interpretation of results and an efficient service.

Source: toxlab.co.uk