Perfusates

Perfusate, in the medical sense, is any liquid used to perfuse tissue or organs during preservation, transport, or therapeutic perfusion. It is designed to deliver oxygen and nutrients, remove waste products, maintain electrolyte and acid–base balance, and limit ischemic injury. Perfusates are employed in static cold storage as well as dynamic machine perfusion and may be acellular solutions or blood- or plasma-based formulations, depending on the strategy and organ involved.

In organ preservation for transplantation, acellular hypothermic solutions such as University of Wisconsin (UW) solution, Custodiol HTK, and Celsior aim to minimize metabolic demand at low temperatures. In machine perfusion, especially normothermic or subnormothermic approaches, perfusates may be cellular or blood-based and can include albumin, red blood cells or hemoglobin-based oxygen carriers, metabolic substrates, and vasodilators. Steen solution is commonly used for ex vivo lung perfusion, while lung procurement may also employ dextran-containing flushing solutions such as Perfadex.

Typical perfusate components include electrolytes (sodium, potassium, calcium, magnesium, chloride), buffers (bicarbonate, histidine), and osmotic agents (dextran, albumin) to maintain oncotic pressure and reduce edema. Many formulations also incorporate energy substrates, antioxidants, and anti-inflammatory additives. Temperature, oxygenation, perfusion pressure and flow, and compatibility with the specific organ largely determine perfusate selection, with the overarching goal of preserving viability during preservation or ex vivo perfusion.