Real-Time assessment of organ vitality during the transplantation procedure

Abstract

Although organ transplantation has become well established as a treatment modality for many patients with organ failure, little attention has been given to the evaluation of organ quality during its various steps. A critical factor in the success of the actual engraftment procedure is the integrity of energy metabolism and oxygen balance (supply/demand) at the microvasculature and intracellular mitochondrial level. The supply of oxygen to the cells is dependent on the saturation of hemoglobin (HbO 2 ), tissue blood flow, and tissue oxygen partial pressure. The mitochondrial reduced nicotinamide adenine dinucleotide redox state represents oxygen balance in the tissue. Although these parameters can be monitored in all tissues of the body, demand for oxygen may be organ-specific. The various steps surrounding transplantation may require different techniques for the evaluation of tissue vitality. Assessment of blood flow or HbO 2 is not possible during preservation of the organ. On the other hand, because extracellular levels of potassium may represent the energy demand processes in many organs, monitoring of extracellular potassium as an indicator of ionic homeostasis may provide important information regarding the quality of the preservation techniques. Although a large number of relevant studies have been performed in small laboratory animals, real-time monitoring in patients needs more practical tools. We present here the principles of multiparametric monitoring by which tissue vitality may be measured in both experimental and clinical situations. Much of the relevant literature on the subject is limited to the monitoring of kidney and liver. There are also some data on the monitoring of skin flaps. We have reviewed the major published reports in which organ and tissue vitality and quality were assessed in real time and will describe tissue and organ oxygen balance, vitality principles, technologic features of the various monitoring techniques, the clinical or experimental tools available and the conceptual and technologic aspects of the multiparametric monitoring concept. We will also discuss both experimental results and preliminary clinical observations by using multiparametric monitoring.