Perfusion scheme for long-term preservation of isolated pig liver in an experiment

Abstract

Background:  Recently, the method of machine perfusion of a liver transplant, which has been gaining popularity, justifies the hopes placed on it. At the same time, the existence of many perfusion schemes confirms the need to find the optimal one. The purpose of this study was to experimentally develop a perfusion scheme for long-term preservation of the liver outside the body by perfusion with normothermic oxygenated blood.

Materials and methods: To create a perfusion device, we used a roller blood pump console, a standard pediatric oxygenator, venous and arterial filters, polyvinyl chloride and silicone lines, and a constant-flow-to-pulsating (external pulsator) converter of our own design. In the perfusion scheme after the roller pump, the blood flow was divided into two streams. The first was sent to the oxygenator. Then, having passed the pulsator, the flow was fed through the aortic stump into the hepatic artery. The second flow was directed to the upper soft-walled tank. As an experimental model, 5 pigs weighing up to 20 kg were used. Under general endotracheal anesthesia under conditions of thoraco-laparotomy, the liver was explanted along with a section of the caudal vena cava and aorta. Injection cannulas were inserted into the aorta and portal vein, and a draining cannula was inserted into the distal end of the vena cava. The cannulas were connected to the perfusion machine and perfusion of the organ was started. Sensors for monitoring blood flow volume, pressure, temperature, and blood oxygen saturation were located at different parts of the perfusion scheme.

Results and discussion: All experiments were carried out for 12 hours. The temperature of the perfusate was maintained within the range up to 37°C; volumetric blood flow in the portal vein was 450-500 ml/min; pressure was maintained within 12-24 mm Hg; the pulse rate in the arterial line did not exceed 100 beats/world; volumetric blood flow in the hepatic artery averaged 80-120 ml/min; the average pressure was maintained within 70 mm Hg. Dosing clamps located on the lines provided the opportunity to optimally redistribute the perfusate flows. So in the caudal vena cava, the pressure was maintained within the physiological norm. At the same time, the required level of perfusate for gravitational injection into the portal vein was stabilized in the soft-walled reservoir.

Conclusion: The developed scheme for machine perfusion liver preservation allows stabilizing two blood (arterial and venous) flows of different characteristics during a prolonged experiment. In parallel with the liver, the kidney, which is adequately perfused in the general blood flow, can function as a controller of hemohydrobalance, a stabilizer of acid-base balance, and an eliminator of metabolic wastes.