Efficacy of topical cooling in lung preservation: is a reappraisal due?

The aim of the present study was to test the efficacy of topical cooling as the only viable lung preservation method using the most challenging evaluation method, namely single-lung transplantation followed by immediate contralateral pneumonectomy. Ten domestic pigs (5 donors and 5 recipients) with a mean body weight of 57 kg (range, 53 to 59 kg) were used. After we administered systemic heparin (4 mg/kg), the lungs were harvested and placed in an atelectatic state under cold (8 degrees to 9 degrees C) low-potassium-dextran solution for 12 hours. Left lung transplantation was then done in the recipient pig followed by right pneumonectomy, thus making the recipient 100% dependent on the transplanted donor lung. No operative mortality or morbidity occurred. All animals were in excellent condition throughout the 24-hour observation period. They had normal blood gases which did not differ significantly from the preoperative blood gases obtained from the 5 recipients before transplantation (ie, when they had their own two lungs). A moderate increase (p < 0.05) in pulmonary vascular resistance was seen as compared with sham-operated animals. To conclude, topical cooling to 8 degrees C provides excellent lung preservation for 12 hours in pigs. If similar results can be obtained with other species, the currently accepted 6-hour limit for safe clinical lung preservation may be extended to 12 hours. It seems also warranted to critically reconsider which factors, apart from cooling alone, actually contribute favorably to 12-hour lung preservation.