Background and Aims: There is a general perception that viscous solutions reduce the rate at which blood is washed out of organs during the cold flush during procurement, inhibit efficient cool-down, and prohibit optimal cortical perfusion of donor organs. Actual data on this topic are scarce but opinions are strong. To study perfusion characteristics we compared four hypothermic preservation solutions for abdominal organs i.e. UW SCS, HTK, IGL-1 and UW-MPS in a large animal model simulating donation after circulatory death (DCD).
Materials and Methods: Twenty 70kg female pigs were terminated [UW (6) and HTK (6), IGL-1 (4), UW-MPS (4)] followed by aortic cold flush-out and addition of slush-ice after 40min warm ischaemia. Companies’ instructions for volumes were used. During wash-out at pre-defined time points perfusate samples were obtained for further analysis and to determine viscosity. Organ temperature was measured continuously and cortical perfusion of kidney and liver was recorded using contrast-enhanced ultrasound. Biopsies were taken at start and end for histology and EM, including assessment of wash-out of blood.
Results: All solutions decreased the temperature of liver and kidney, although no solution reached temperatures lower than 18°C and 15°C resp. No significant difference in end liver temperatures was observed between different solutions (p=0.63), however end temperatures of kidneys were significantly different when comparing UW to HTK (15.1°C vs 20.3°C) (p=0.04). Cortical perfusion of livers was equally good between solutions (p=0.28), while in kidneys UW and IGL-1 penetrated better compared to HTK (p=0.02 and 0.03, resp.). No significant differences in histology or EM were seen in kidneys at the beginning or the end of the procedure, reflecting adequate intravascular wash-out, irrespective of viscosity.
Discussion: This study contradicts a popular perception and provides evidence that increased viscosity of a preservation solution does not negatively affect cooling and quality of organ perfusion. In fact, we found that UW SCS may be better at flushing out blood and cooling DCD kidneys. This study also provides interesting physiological data about the interaction between cold flush-out solutions and kidney and liver tissue at time of retrieval and start of preservation.
Conclusion: A higher viscosity in a preservation solution does not negatively affect cooling during flush-out at time of retrieval and does not have any detrimental effect on the quality of organ perfusion and preservation.