Re-oxygenation of haemoglobin in livores after post-mortem exposure to a cold environment.

When a body is exposed to a cold environment, the livid colour of livor mortis changes to cherry red. This colour change is due to an increase in the concentration of oxygenated haemoglobin. The chronological course and the extent of haemoglobin re-oxygenation associated with the exposure to low ambient temperatures have not been understood so far. The relations between refrigeration time under a constant ambient temperature (5 degrees C), skin temperature, body mass index (BMI), spectral reflectance curve and O2-Hb concentration in livor mortis were systematically investigated in 84 bodies brought to the Institute of Legal Medicine of the Freiburg University Hospital shortly after death. In the first measurements performed shortly after death, the reflectance curves of the livores of all bodies showed a broad minimum at 555 nm. After a refrigeration time of 44.9 +/- 17.9 h, the spectrum changed to the typical picture of O2-rich blood with 2 minima at 541 and 576 nm and a maximum at 560 nm in between. This qualitative change of the reflectance spectra was observed for a skin temperature of 10.3 +/- 2.7 degrees C. With the help of a physical skin model it was possible to calculate that due to the post-mortem exposure to cold the O2-Hb concentration in the livores rose from 0-1% to a value of up to 89.3%. The change in the reflectance curve was discernible from an oxygen saturation of 25 +/- 13.8%.