Recovery of alveolar microcirculation after lung transplantation in a pig model: direct visualization by OPS imaging

Objectives: Transplant failure due to ischemia/reperfusion injury is one of the major risks during transplantation. It was the aim of our study to analyze microcirculatory changes in the early phase of reperfusion after lung transplantation (LTX).

Material and Methods: We performed single LuTX on 6 pigs after 24h graft-ischemia preserved with low-potassium-dextran solution. Microcirculation was assessed by intravital microscopy (OPS). Images were obtained before graft extirpation (BL), after 15min (I), 30min (II), 1h (III) and 3h (IV) of reperfusion. Microcirculatory parameters were evaluated offline at a later timepoint. Hemodynamic parameter and blood gas exchange were recorded at each timepoint.

Results: Mean diameter of alveolar capillaries showed a significant increase after transplantation (from 6.91±2.64µm to 8.56±4.33µm, BL vs. III, mean±SD; p<0.05) and stayed increased after 3h (8.3±5.7µm). Mean velocity of RBC significantly decreased after LTX (from 293.1±87.5µm/s to 175.6±77.3µm/s, BL vs. II, p<0.05) and demonstrated a slow recovery after 3h (230.5±78.3µm/s). FCD decreased (from 26.4±6.6mm/mm² to 15.1±4.1mm/mm², BL vs. II, p<0.05) and still showed a significant decrease after 3h (19.9±9.8mm/mm²). All hemodynamic parameters and the blood gas exchange remained stable during observed timepoints.

Conclusions: Our study describes changes of the microcirculation after LTX for the first time. We noted a significant delay of microcirculatory blood flow when compared to large vessels reperfusion and a relative vasoplegia of the denervated organ. The importance of microcirculatory changes and the clinical relevance of therapeutic measures shall be evaluated further.