Postmortem Discussion Summary
Nikolas Lemos, San Francisco Medical Examiner’s Office
There were four Postmortem Toxicology Round tables during the March 2005 CAT Meeting in Sacramento, CA and participants from four different States participated. Many were employed in government toxicology laboratories already performing postmortem toxicology, others were private consultants and some were considering employment in the postmortem forensic toxicologic arena. In addition, some vendors also sat at these round tables.
Topics covered a broad spectrum of postmortem toxicologic issues including the collection of specimens. Postmortem forensic toxicologists reported a significant variation between organizations on the specimens and quantities collected. Hospital blood was generally considered to be the specimen which would give the most accurate peri-mortem toxicologic profile. Central Blood was offered as the specimen on which general drug screening should be performed. Confirmations and quantitation are best performed using peripheral blood. On the topic of peripheral blood, several participants
suggested that toxicologists play a more prominent role in educating those professionals collecting specimens (medical examiners, coroners, autopsy technicians, etc) on the best locations for peripheral blood (femoral, iliac and subclavian veins) following visualization and clamping of the veins.
The round table participants discussed in great detail the use of urine as a screening specimen and it was reported that the vast majority of analytical laboratories represented at the round tables use urine as a screening specimen and not for quantitations.
The collection and analysis of other specimens such as vitreous humor and cerebrospinal fluid were also briefly discussed. Existing techniques on the collection and homogenization of specimens such as liver and gastric contents were also discussed. It was generally agreed that a liver section from deep within the right liver lobe is best in order to avoid contamination from gastric content diffusion and that the total volume of gastric contents should be thoroughly mixed and homogenized in an appropriate blender in order for the analytical results to be most representative of the actual gastric contents.
On the subject of specimen preservation, there was agreement that blood specimens are generally preserved with sodium fluoride and refrigerated and most other specimens are also refrigerated as part of existing protocols even while awaiting analysis. On the subject of specimen retention by analytical laboratories, it was generally agreed that the current practices as dictated by N.A.M.E. are satisfactory and that analytical laboratories should have written policies on the retention and destruction of specimens.
Several participants reported specimen handling as a significant analytical challenge - postmortem specimens tend to be more difficult to handle and laboratories should establish method and train scientists in the best way to handle denatured, decomposed and other postmortem specimens. Liver alcohol analysis was flagged as a potential challenge as there may be alcohol production in unpreserved liver specimens due to bacterial activity - it was suggested that liver be preserved like blood during the homogenization stage of the analysis and that it be placed at the beginning of a batch so that it does not sit on the autosampler for hours waiting analysis.
On the topic of postmortem toxicologic reporting, it was generally agreed that analytical laboratories should avoid listing reference tables on their reports due to the fact that cases always differ and frequently reference table list clinical levels and not postmortem ones. The interpretation of postmortem toxicologic results was the final topic of discussion and it was agreed that forensic toxicologists interpreting postmortem toxicologic results must always exercise caution and must consider the totality of the circumstances surrounding the death and also must remember that drug interactions and postmortem redistribution must also be taken into account before an opinion is offered.