Warm Ischemia in Transplantation: Search for a Consensus Definition

“Warm ischemia” is a term used to describe ischemia of cells and tissues under normothermic conditions. In the transplant setting, this term is used to describe two physiologically distinct periods of ischaemia: (1) Ischemia during implantation, from removal of the organ from ice until reperfusion, and (2) Ischemia during organ retrieval, from the time of cross clamping (or of asystole in non-heart-beating donors), until cold perfusion is commenced. These periods of warm ischemia differ in their nature and the magnitude of their pathophysiologic consequences. In much transplant literature, however, the term “warm ischaemia” is used to describe both of these periods indiscriminately. This paper attempts to produce a definition to distinguish between the two periods of warm ischemia. We conducted a questionnaire survey of all UK transplant surgeons. The definitions proposed in the survey were: (a) warm ischemia and re-warm ischemia; (b) first warm ischemia and second warm ischemia; (c) in-situ warm ischemia and ex-vivo warm ischemia; (d) warm ischemia in donor and warm ischemia in recipient; (e) no opinion or other opinion. There was a 64% response rate among 134 consultants with no consensus definition being reached. The majority of consultants (31.4%) preferred the terms “warm ischemia in donor”, and “warm ischemia in recipient” to distinguish the two periods. This paper highlights the need to adopt uniform terms to avoid confusion between different types of warm ischemia in transplantation.