Pulsatile Perfusion (PP) has been shown to improve the performance of deceased donor organs, particularly when used with extended criteria donors. Performance on the pump has been used diagnostically to determine kidney viability. However, PP assessment is currently limited to measurements of flow (V) and intrarenal resistance (R) to assess organ viability and guide resuscitation, and may thus be insufficiently sensitive to guide prompt intervention. Additionally there are no objective measures of the local effects of ischemia in real-time. A non-invasive method that assesses perfusion globally during PP might allow for objective, real time assessment. We have thus investigated infrared (IR) imaging during hypothermic PP as a means for more precise organ assessment. ? ? Methods: IR was used to monitor 10 porcine kidneys procured in a model that mimics an uncontrolled Donor after Cardiac Death (5 pairs) and 8 human (3 pairs and 2 single) kidneys that were deemed non-transplantable during PP. All kidneys were placed on a hypothermic PP (4 degrees C) machine for 4 hours (RM3, Waters Medical Systems). Each kidney was cannulated and placed on individual cassettes primed with Belzer Machine Perfusion Solution and perfusate temperature (T degrees C), pressure, V, and R were recorded for each kidney. An IR camera (Lockheed Martin) was focused on the anterior surface of the kidneys. This device is sensitive to ~0.02 degrees C gradients in 3-5 micron wavelengths. Images (256x256 or 320x256 pixels) were collected every 3-10 sec during PP and later analyzed using regions of interest (ROI). The degree of perfusion homogeneity was assessed as compared with standard measurements.? ? Results: IR images revealed differences (0.5-0.9 degrees C) between left and right kidney temperatures for all cases. Higher flow and lower resistance as measured by the RM3 detectors were seen in cooler kidneys (n=9). Warmer kidneys had low flow and high resistance to perfusion (n=9). Temperature asymmetry between left and right kidney fluctuated (~0.3 degrees C) but never reversed during any experiment indicating consistent differences between kidneys. Significant intra-cortical variations in temperature were found in human, and to a lesser degree, in porcine kidneys. All IR images clearly demonstrated differences between superior, middle and inferior segments regions of interest for each kidney. More homogeneous IR images of both human and pig kidneys were seen at the end of perfusion (n=13).? ? Conclusion: IR assessment of perfusion correlates with V and R. Additionally, IR evaluation revealed inhomogeneous perfusion that improved over time with PP and was not evident by standard measurements of V and R. Ex vivo IR assessment is a promising methodology to finely measure human renal perfusion that may facilitate more accurate renal resuscitation and aid in the care and subsequent transplantation of Expanded Criteria Donor kidneys.
