Therapeutic effect of surfactant inhalation during warm ischemia in an isolated rat lung perfusion model

Warm ischemia-reperfusion injury related to donation after cardiac death donors is a crucial and inevitable issue. As surfactant function is known to deteriorate during warm ischemia, we hypothesized that surfactant inhalation during warm ischemia would mitigate warm ischemia-reperfusion injury. We used an isolated rat lung perfusion model. The rats were divided into three groups: sham, control, and surfactant. In the control and surfactant groups, cardiac arrest was induced by ventricular fibrillation. Ventilation was restarted 110 min later; subsequently, the lungs were flushed, and heart and lung block was recovered. In the surfactant group, a natural bovine surfactant Surfacten(®) was inhaled for 3 min at the end of warm ischemia. Then, the lungs were reperfused for 80 min. Surfactant inhalation significantly improved graft functions, effectively increased lung tissue ATP levels, and significantly decreased mRNA levels of IL-6 and IL-6/IL-10 ratio at the end of reperfusion. Histologically, lungs in the surfactant group showed fewer signs of interstitial edema and hemorrhage, and significantly less neutrophilic infiltration than those in the control group. Our results indicated that surfactant inhalation in the last phase of warm ischemia maintained lung tissue energy levels and prevented cytokine production, resulting in the alleviation of warm ischemia-reperfusion injury.