FILTRATION COEFFICIENT IN ISOLATED PRESERVED AND REPERFUSED CANINE LUNG

The filtration coefficient (Kf) in Starling's equation for fluid exchange was estimated in isolated reperfused canine lobes to evaluate the effect of ischemia-reperfusion injury on alveolar-capillary permeability quantitatively and to determine the inhibitory effects of a high dose of methylprednisolone (MPS) or dimethylthiourea (DMTU), a potent hydroxyl radical scavenger, on this injury. We reperfused isolated canine left lower lobes (LLLs) with blood at a constant flow after 3 hr of warm (38°C) or cold (4°C) ischemia and measured Kf after 1 hr of reperfusion. The mean value of Kf (±1 SD) in the cold ischemic lobes (COLD, n = 7), 0.13 ± 0.04 g·min-1·cmH2O-1·100 g-1, was not different from that in the control nonischemic lobes (CONT, n = 6), 0.10 ± 0.04 g·min-1·cmH2O-1·100 g-1. In contrast, the mean value of the Kf in the warm ischemic lobes (WARM, n = 7), 0.38 ± 0.17 g·min-1·cmH2O-1·100 g-1, was significantly (P < 0.001) higher than in CONT. MPS (30 mg/Kg) or DMTU (0.75 g/kg) administered before isolation of LLL and before reperfusion reduced the increase in Kf in warm ischemic lobes to 0.19 ± 0.09 and 0.19 ± 0.05 g·min-1·cmH2O-1·100 g-1, respectively (P < 0.005 WARM vs MPS, and P < 0.01 WARM vs DMTU). MPS and DMTU also attenuated the impairment of gas exchange. We conclude that (1) reperfusion after 3 hr of warm ischemia increases Kf but after cold ischemia does not, and (2) MPS and DMTU prevent the increase in Kf. Our data suggest that the ischemic-reperfusion lung injury may be due in part to the hydroxyl radical and some pharmacological agents can prevent the injury by attenuating increase in pulmonary microvascular permeability. © 1991.