Chapter 140: Postmortem Toxicology

CASE

A newly hired train conductor sustains irreversible brain injury due to a large subdural hematoma from a train crash. Surgical intervention is deemed futile. After 4 days in the hospital, he is declared dead by neurologic criteria (ie, “brain dead”) and removed from life support. An autopsy confirms the brain injury. Postmortem toxicologic samples are obtained from the femoral vein and reveal oxycodone and oxycodone metabolites. As a toxicologist, you are asked to interpret the findings. How do you proceed?

INTRODUCTION

Postmortem toxicology is the study of the identification, distribution, and quantification of xenobiotics after death. This information is used to account for physiologic effects of a xenobiotic at the time of death through its quantification and possible redistribution in the body at the time of autopsy. Several variables cause changes in xenobiotic concentrations during the interval between (1) the time of death and subsequent autopsy and (2) the storage interval between the time of sampling and the time of testing. Toxicologists and forensic experts are frequently asked to interpret postmortem xenobiotic concentrations and decide whether the reported values are meaningful and whether these xenobiotics were incidental or contributory to the cause of death.

The development of the field of forensic toxicology and the improvement of laboratory technology now permit more refined identification and quantification of xenobiotics. The interpretation of postmortem xenobiotic concentrations and their significance, however, continues to evolve.

This chapter reviews factors that affect xenobiotic concentrations identified at autopsy and discusses an approach for interpreting postmortem toxicologic reports as they relate to the cause and manner of death.^{39,40,43,45,52-54,61,86,105}

HISTORY AND ROLE OF MEDICAL EXAMINERS

The relationship between antemortem xenobiotic exposures and death has been a subject of investigation for centuries. In 12th-century England, an appointee of the royal court, eventually named the coroner, was designated to record and identify causes of death.⁷⁸ In suspicious circumstances, coroners investigated poisonings, but scientific methods were primitive, and conclusions regarding such deaths were conjecture at best.

By the mid-19th century, however, techniques for detecting certain xenobiotics in postmortem tissue were developed and focused generally on identifying heavy metals as a cause of death in homicides.^{46,78,83,102,108} At that time, coroners were still elected or appointed individuals with little or no medical training. However, with better laboratory techniques and autopsies being performed by trained pathologists, the specialty of forensic medicine continued to develop. In Massachusetts during the late 19th century, these forensically trained pathologists, referred to as medical examiners, ultimately replaced the coroner system and were eventually empowered by the state to investigate and determine the cause and manner of death in certain types of unusual or suspicious cases and the medicolegal autopsies ...