Organ preservation is a major determinant for post-transplant reperfusion injury, including preservation time, temperature, and solution. Experiments with liver, pancreas, and intestinal transplantation have demonstrated that the cold ischemia time determines post-transplant microcirculatory derangements, inasmuch as an increase of duration of preservation is associated with aggravation of both microvascular perfusion failure (no-reflow) and leukocytic response (reflow-paradox). In clinical practice, a temperature of 4°C for preservation is chosen because of the practicability of cooling the organ with ice and is based on the idea that the temperature should be as low as possible to achieve the utmost protection. However, recent experimental studies have demonstrated that for a 90-minute ischemia period, preservation at 15°C and 26°C is as effective as cooling to 4°C in preventing postischemic micro-circulatory failure, leukocytic inflammatory response, and hepatocellular disintegration. The protection achieved with only moderate cooling is probably the result of attenuation of intratissue reactive oxygen species production, associated with a reduced adenosine monophosphate hydrolysis during the ischemic time period. In fact, there is some evidence that a mild hypothermia of about 20°C may protect the grafts' microvascular endothelium even more efficiently than a storage temperature of 4°C.
Daily clinical practice has revealed that post-transplant graft function is strongly dependent on the preservation solution used for organ cold storage. Today, University of Wisconsin (UW) solution and HTK solution are the most applied introduced preservation solutions in parenchymal organ transplantation, including the liver, the kidney, and the pancreas. Although it has not been finally clarified which ingredients within the solutions are protective to prevent the manifestation of post-transplant microcirculatory dysfunction, there is evidence that preservation solutions that contain antioxidative compounds, such as UW or HTK solution, are more effective in reducing microvascular cold ischemia-reperfusion injury when compared with others lacking antioxidative components, such as Euro-Collins solution. The efficacy of UW and HTK solution to improve post-transplant microvascular perfusion after cold storage may, however, be due not only to their antioxidative action, but also to the solution-associated capacity to inhibit cell swelling, as shown directly by electron microscopy, and, indirectly, by the prevention of cold ischemia-reperfusion-induced sinusoidal diameter reduction.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.