The following is a summary of “Impaired O2 unloading from stored blood results in diffusion-limited O2 release at tissues: evidence from human kidneys,” published in the December 2023 issue of Hematology by Dumbill et al.

In the systemic transfer of oxygen from capillaries to tissues, the oxygen content within red blood cells (RBCs) and their ability to release oxygen are essential factors affecting this process. Traditionally, the rapid kinetics of oxygen unloading from RBCs have been considered negligible, leading to the assumption that oxygen transport to tissues is primarily limited by blood flow. Medical strategies to enhance oxygen delivery typically focus on improving arterial oxygen content and blood flow rather than handling oxygen by RBCs. However, previous research has indicated that stored blood experiences a decline in the ability to release oxygen, potentially compromising overall oxygen distribution to tissues and transitioning the transport into a diffusion-limited state. Their study aimed to ascertain evidence supporting diffusion-limited oxygen release in functional human kidneys perfused with stored blood under normothermic conditions. In kidneys intended for transplantation, the researchers observed a correlation between ex-vivo renal respiration and the rate of oxygen release from the RBCs used for perfusion, indicating an inverse relationship.

Additionally, the kidney’s rate of oxygen consumption did not correlate with arterial oxygen delivery unless the rate of oxygen release from RBCs was considered, aligning with the expectations of diffusion-limited transport. In kidneys deemed unsuitable for transplantation, the study group performed alternating perfusion experiments using stored and rejuvenated RBCs from the same donation, allowing them to control oxygen unloading without affecting other non-RBC parameters or inducing ischemia. This intervention demonstrated that rejuvenated oxygen-unloading kinetics notably improved the kidney’s oxygen diffusion capacity, enhancing cortical oxygen partial pressure by approximately 60%. Their findings underscore the potential for oxygen delivery to tissues to shift into a diffusion-limited state when perfused with stored blood. This insight holds implications for various scenarios, including ex-vivo organ perfusion, cases of significant hemorrhage, and pediatric blood transfusions.

Source: sciencedirect.com/science/article/abs/pii/S0006497123145733