Comprehensive evaluation of pericardial biochemical markers in death investigation

Abstract

Pericardial fluid (PCF) is a well-preserved cadaveric material in cases without structural damage. The present study investigated fundamental serum components of PCF, including total proteins (TP), albumin (Alb), urea nitrogen (UN), creatinine (Cr), uric acid (UA), glucose (Glu), sodium (Na), potassium (K), chloride (Cl), calcium (Ca) and magnesium (Mg) in PCF with regard to the postmortem and survival periods, and cause of death in serial medicolegal autopsy cases (n = 288) with intact pericardial and cardiac structures within 48 h postmortem. The amount of PCF (mostly 5–25 ml) showed no survival or postmortem time dependence, or difference among the causes of death. For all cases, there were moderate postmortem decreases of Na and Cl, and increases of K and Mg, which were insufficient for application to estimate the time since death; however, characteristic findings with regard to the cause of death were detected in cases of hours-long survival, especially in ‘functional causes of death’: higher Alb, UN, Cr, UA, K and Mg, and lower Na, Cl and Ca in intoxication; lower TP, Alb, Cr, K and Mg, and higher Na and Cl in hypothermia (cold exposure); higher Alb, UN, Cr, UA and Mg, and lower Glu and Ca in hyperthermia (heatstroke). These observations suggest the usefulness of pericardial biomarkers for investigating the cause and process of death to reinforce pathological and toxicological findings.

Introduction

A serial study has shown the usefulness of systematic biochemical analyses as ancillary procedures for investigating death, in which blood and various body fluids have been used, including the vitreous humor, and cerebrospinal and pericardial fluids [1], [2], [3], [4], [5], [33]. Rapid changes can occur in circulating blood in the death process, whereas such changes may be milder in body fluids; however, postmortem interference is inevitable for each of these materials. Pericardial fluid (PCF) is a transudate from the epicardium [11], [12], [13], and a well-preserved and useful postmortem material in cases without structural damage due to injury or medical intervention, containing various biochemical substances derived from serum and heart tissue [6], [7], [8], [9], [10], [11], [12], [13]. Alterations of heart tissue can immediately affect PCF components [8], but previous studies have suggested an hours-long half-life period of pericardial albumin [14], [15] as well as the substantial stability of circulating serum-derived substances, including urea nitrogen (UN), creatinine (Cr) and uric acid (UA), in agony and postmortem periods [6], [7]; however, pericardial electrolyte/mineral concentrations depend on postmortem period [16]. From these observations, we hypothesized that PCF components derived from circulating blood represent the antemortem status, including the status before fatal insults in acute death and the changes during survival in prolonged death, while pericardial electrolytes/minerals depend on both antemortem status, involving myocardial damage, and postmortem changes; the combined analysis of these PCF components may be useful for investigating the cause and process of death as well as postmortem changes of the myocardium, which can depend on the status at the time of death and ambient temperature after death.

With consideration of the hypothesis described above, the present study investigated a spectrum of fundamental serum components of PCF, including total protein (TP), albumin (Alb), non-protein nitrogen compounds (NPN), glucose (Glu), and electrolytes/minerals with regard to the postmortem time, survival time and cause of death in serial medicolegal autopsy cases and compared individual characteristics to provide basic data for postmortem biochemistry of PCF in death investigations.