Transcellular and extracellular impedances of the intact abdomen in putrefying rat cadavers.

Total (Zt) and extracellular (Ze) abdominal impedances of putrefying rat cadavers, stored at 18.0 +/- 0.7 degrees C, were measured at 50 kHz and at 1 kHz, respectively, during the first 7 days of death. Transcellular impedance was calculated from the measured values of Zt and Ze. Total impedance and Ze increased during the first day, and then decreased with increasing postmortem interval, while Zi remained unchanged during the first 3 days before increasing more than 4-fold between 3 and 7 days postmortem. These changes are consistent with net gain of electrolyte by the extracellular fluids and with degeneration of cell membranes which occur postmortem. It is concluded that, during putrefaction, Ze is a potentially more useful index of postmortem interval than Zt or Zi, and that measurement of total abdominal impedance at 50 kHz, rather than at 10 kHz, markedly improves the precision and accuracy of impedance measurement.