SUMMARY

Post-mortem redistribution (PMR) refers to the site and time-dependent blood drug concentration variations occurring after death. Our study aimed to compare central blood concentration (subclavian site) with peripheral blood concentration (femoral and popliteal sites) of selected psychoactive substances. Time-dependent variation of blood concentration is also assessed by means of two methods. To our knowledge, popliteal blood concentration has never been compared with other sites before. In this preliminary study, there were 23 cases divided in 2 groups: a general group in which central (subclavian) and femoral blood was drawn, and a group labelled popliteal in which an additional blood sample was obtained from the popliteal vein. Each group was also divided in 2 subgroups, one with only one sample and the other with a second sample taken from the same case at a later time. The targeted substances were diazepam and metabolites, methadone and metabolite and morphine and metabolites. For each substance, mean concentration ratios were calculated as follows: [subclavian]/[femoral] in the general group and [subclavian]/[femoral], [subclavian]/[ popliteal] and [femoral]/[popliteal] in the popliteal group. In the cases sampled only once, correlations between concentration ratios and estimated post-mortem interval were obtained for each substance. In those cases sampled a second time after a time interval, correlations between concentration difference ratios (and concentration differences) and precise time interval elapsed between samples No. 1 and No. 2 were obtained for each substance. The results indicate that the popliteal sample site appears to be less subject to PMR as seen in the concentration ratios in the group with popliteal sampling. Cases sampled only once, as well as those sampled a second time, when correlated with the post-mortem interval, show that the latter did not have significant influence on concentration ratios, concentration difference ratios or concentration differences.

Keywords: Popliteal blood, Postmortem redistribution, Psychoactive drugs, Postmortem interval.