Vernard I Adams

DEFINITIONS, INDICATIONS AND LIMITATIONS OF THE METHOD

Autopsy chemistry, or postmortem chemistry, is the term applied to the measurement of endogenous constituents in dead bodies. Toxicologic tests, which measure concentrations of drugs and exogenous toxins, are discussed in Chapter 2. Postmortem chemical studies provide direct information concerning derangement of physiology. In contrast, customary gross and histological autopsy examinations are primarily tests of structural derangement, from which physiologic derangements may sometimes be inferred. Chemical testing may not only establish the cause of death but may contribute to the evaluation of the physiologic effects of recognizable anatomic lesions. For example, the extent of uremia can be determined in a case of polycystic kidney disease.

Although any clinical laboratory test may be applied to postmortem material, only a limited number of tests yield results that can be interpreted. Useful tests fall into two groups; those that measure analytes that are stable after death, toward the end of estimating the antemortem concentrations; and those that measure a diagnostically useful postmortem rise or fall in the concentration of the analyte. For many biochemical substances, interpretation of postmortem tests is precluded by the total absence of published data.

Our understanding of postmortem chemistry has been considerably enhanced by the pioneering work of Dr. Coe (1), a forensic pathologist who showed that the vitreous, which is normally unavailable for clinical testing, is the substrate of choice for what have become the most frequently used postmortem chemical tests. Because the eye is mechanically isolated and well-protected by the orbit, vitreous is usually preserved even if serious trauma to the head had occurred. Vitreous is less subject to putrefaction than is blood, and is not subject to diffusion of drugs and alcohol. Like cerebrospinal fluid, it is nearly free of erythrocytes, but it is more accessible and artifacts of procurement are easier to recognize.

In this chapter, we give only an overview of autopsy chemistry. For methodological details, the reader should consult standard textbooks and manuals of laboratory medicine as well as pertinent references in the review articles by Coe (1) and Kleiner et al. (2). Many of the data presented here are derived from Dr. Coe's work.

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