A method to perfuse liver metastases with heated blood (45 degrees C, 45 min).

To heat the livers in ten pigs (20-30 kg) a system of two pumps, both connected to the cannulated A.femoralis and to two radio-wave heating devices, was used. With pump I the arterial vascular system of the liver was perfused for 45 min via the A.gastroduodenalis with a constant volume of 150-200 ml blood/min, heated to 44-45 degrees C. With pump II 50-700 ml/min heated blood was pumped into the portal vein to raise the temperature and oxygen content of the portal flow. During the heating period the A.hepatica was clamped. A temperature of 45 degrees C is a highly toxic for the differentiated liver tissue, but the more simply structured wall of the arteries tolerates this temperature. This difference in heat resistance allows the perfusion of the arterial vascular system of the liver with blood heated to a temperature that is fatal to liver tissues. On the way from the A.gastroduodenalis to the liver periphery the heated blood becomes cooled by the surrounding cooler liver tissues. Finally the supply to the lobules is a mixture of arterial and venous blood, i.e. the highly toxic agent, heat, becomes "detoxified" by cooling before reaching the heat-sensitive liver lobules. Changing flow and temperature in the portal vein allows the temperature of the liver lobules to be kept within a safe range, i.e. below 43 degrees C. The raised oxygen content in the portal flow allows the arterial perfusion to be stopped for 10 min (to subject a heated metastasis to a period of hypoxia). Liver enzymes reached their maximal level 2 days after heating and returned to normal within 1 week. It is supposed that this method allows the temperature in a liver metastasis to be raised to a tumoricidal level.