Postmortem serum nitrogen compounds and C-reactive protein levels with special regard to investigation of fatal hyperthermia

The present study analyzed serum levels of urea nitrogen (UN), creatinine (Cr), and C-reactive protein (CRP), which are very stable during the early postmortem period, for investigation of the cause of death with special regard to hyperthermia (heat stroke) in serial medico-legal autopsy cases (n = 429), excluding fatal injury, intoxication, and fire fatality. In this series, mechanical asphyxiation, drowning, and sudden cardiac death cases (n = 56, n = 43, and n = 212, respectively) usually showed low levels within postmortem reference ranges for these serum markers, although UN and CRP levels were mildly elevated in cases of sudden cardiac death and cerebrovascular stroke. There were concomitant significant elevations in serum levels of UN (>50 mg/dL), Cr (>2 mg/dL), and CRP (>2 mg/dL) for chronic renal failure, gastrointestinal bleeding, pneumonia, and hypothermia (cold exposure). UN and CRP were especially high for chronic renal failure and pneumonia, respectively. However, hyperthermia cases showed an isolated elevation in the serum Cr level, suggesting an influence of systemic skeletal muscle damage. These serum markers may be practically useful for postmortem investigation of death due to hyperthermia (heat stroke), for which specific pathological and toxicological evidence may not be available.