Feasibility of lung microdialysis to assess metabolism during clinical ex vivo lung perfusion

BACKGROUND: Lung metabolism during ex vivo lung perfusion (EVLP) is increasingly studied. Microdialysis (MD) allows metabolic monitoring by sampling parenchymal interstitial fluid. This study investigated lung metabolism using MD during EVLP and evaluated whether microdialysate metabolites could improve selection and discriminate outcome of donor lungs. METHODS: MD monitoring was used during 14 clinical EVLP procedures. Paired microdialysate and perfusate samples were analyzed for glucose, lactate, pyruvate, glutamate, and the lactate/pyruvate (L/P) ratio, and values that best discriminated an unfavorable outcome were determined. Outcome was defined as unfavorable (lungs not transplanted or transplanted with primary graft dysfunction at 72 hours = 2) or favorable (lungs transplanted with primary graft dysfunction < 2). RESULTS: Microdialysate markers and the perfusate L/P ratio could discriminate unfavorable outcome with sensitivity and specificity of 0.85 and 0.81 for MD glutamate > 18.4 mmol/liter, 0.81 and 0.74 for MD lactate > 685 mmol/liter, 0.92 and 0.75 for MD glucose > 530 mu mol/liter, 0.85 and 0.65 for MD pyruvate > 25 mmol/liter, and 0.73 and 0.67 for perfusate L/P ratio > 24.17. All microdialysate markers, perfusate and microdialysate L/P ratio, and perfusate lactate discriminated outcome when we limited analysis only to transplanted lungs. CONCLUSIONS: We report the use of MD to evaluate lung metabolism during clinical EVLP, demonstrating that MD metabolites can contribute to selection of reconditioned lungs and discriminate early outcome after transplantation. Furthermore, glutamate as a marker of lung injury during EVLP is proposed and could hence be used as a potential target for future therapies.