Postexcision Changes and the Death Process

Tissue metabolism decreases after the tissue has been excised. Often the temperature falls, and measured variations must account for such possible variables. If the tissue is supported by temperature and perfusion systems, then the tissue may be stabilized in a living state 

If the tissue is not supported, then irreversible changes will occur, followed by cell and tissue death. If blood flow is interrupted, then the metabolism continues, but in an anaerobic way. Osmosis will cause cell swelling and tissue damage, and a consequence of 

The initial drop in resistance is due to the warming up of the cool tissue sample, and the subsequent drop in 10-MHz resistance is probably caused by accumulation of metabolic products in the tissue (as mentioned previously). The 100-Hz resistance rises steeply after a period of approximately 3 h, indicating the onset of tissue damage. This damage is nonreversible when the upper plateau is reached and the organ cannot be revived. In addition, Salazar (2004) found that bioimpedance measurements enabled differentiation among 

In keratinized tissue such as the outer layers of the human skin and in hair, nad, and horn, the change and ultimate death of the cells are genetically programed to occur during a period of approximately 30 days. The dead keratinized cells need no intra- or extracellular fluids, and they may be in a dry state wifli low admittance values. 

Bozler and Cole (1935) measured the electrical impedance of frog sartorius muscle from 1.1 kHz to 1.1 MHz. Measurements were first done approximately 2 h after dissection. The tissue was then stimulated to induce contraction, and the tissue was measured again, approximately 3 h after dissection. They found a minor arc of a circle when the data were plotted in the complex impedance plane. Between the relaxed and contracted state, Rq was found to increase by 75% whereas Roo increased only 2%. As usual, Rq and Ra denote the resistances measured at very low and very high frequency, respectively. The significant increase in Rq was interpreted as a reduced ionic conduction through the cell membranes. 

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