What is the primary temperature difference between hypothermic and normothermic machine perfusion techniques for organ preservation?

The primary temperature difference between hypothermic and normothermic machine perfusion techniques for organ preservation lies in their operational temperatures: hypothermic perfusion operates at very low temperatures, typically between 1 and 10 degrees Celsius, whereas normothermic perfusion operates at physiological temperatures, generally between 34 and 37 degrees Celsius. Hypothermic machine perfusion (HMP) is a technique where an organ is continuously perfused with a preservation solution at cold temperatures. The purpose of these low temperatures is to induce metabolic suppression, which means significantly slowing down the metabolic rate of the organ's cells. The metabolic rate refers to the speed at which chemical processes occur within cells to sustain life and produce energy. By reducing the metabolic rate, the cellular demand for oxygen and nutrients is drastically decreased, thereby minimizing cellular damage that would otherwise occur from a lack of blood supply and oxygen (ischemia) during the preservation period. This cold environment essentially puts the organ into a dormant state, extending its viable preservation time. In contrast, normothermic machine perfusion (NMP) involves perfusing the organ with an oxygenated, nutrient-rich solution at temperatures similar to that of the human body, typically 34 to 37 degrees Celsius. At these physiological temperatures, the organ's cells maintain near-normal metabolic activity, meaning their chemical processes function much as they would inside the body. This continuous supply of oxygen and nutrients allows the organ to remain metabolically active, potentially enabling repair of ischemic injury incurred prior to perfusion, assessment of organ function, and prediction of post-transplant viability. Physiological conditions refer to maintaining the organ in an environment that closely mimics its natural state within the body, allowing it to function and metabolize.