Hypothermic Circulatory Arrest with "Low Flow" Lower Body Perfusion: An Experimental Feasibility Study of Microcirculatory Parameters.

Background: To avoid extended cardiopulmonary bypass (CPB), moderate temperatures are commonly accepted for hypothermic circulatory arrest (HCA), thereby jeopardizing organ protection. Distal aortic perfusion may be an option, but supportive experimental data is missing. Methods: Eight juvenile pigs (36 ± 2 kg) were cooled to 30°C followed by 60min of HCA with 50 min of lowflow(LF) lower bodyperfusion. Multimodal monitoring was used to measure overall metabolism, hemodynamics andmicrocirculation of the terminal ileum. The animals were observed for four hours following reperfusion. Organs were harvested for histopathological evaluation. Results: During LF perfusion, initially elevated llactate levels decreased subsequently (p < 0.05). Capillary blood flow decreased during cooling to 50% baseline levels (p = 0.03), but remained stable under LF conditions. Parameters indicative of reduced liver and kidney function were slightly elevated at the end of the experiment, but still within normal ranges. Conclusion: Under moderate hypothermia, low flow perfusion seems to provide adequate protection for the lower body organs. Microcirculatory parameters during perfusion as well as lactate levels within normal ranges throughout the experiments further confirm the concept. [ABSTRACT FROM AUTHOR]