Perfusate composition and edema formation in isolated rat lungs

The effect of perfusate composition on duration of lung perfusion until development of alveolar edema was evaluated in isolated ventilated rat lungs perfused at a rate of 25 ml/min in a recirculating system. When the perfusate was Krebs-Ringer bicarbonate solution (KRB) alone, alveolar edema developed in 40-85 min. Addition of glucose (5 mM) slightly prolonged the time to edema while addition of 3% fatty acid-poor bovine serum albumin (BSA) extended mean survival to 3.5 hr. With KRB containing both glucose and BSA, mean survival was greater than 4 hr and three of eight lungs had not become edematous when the experiments were terminated at 5 hr. Similar results were obtained when a synthetic plasma-stimulating solution (SPSS) that is essentially free of protein or other colloid was used as a perfusate. Perfusion at reduced flow rates (12 ml/min) with KRB plus glucose and BSA or with SPSS gave 5-hr survival rates of 100%. These results indicate that prolonged lung perfusion is possible with a colloid-free artificial medium and suggest that both mechanical and metabolic factors are important in maintaining isolated perfused rat lungs free of alveolar edema.