ACUTE LUNG INJURY AFTER AORTIC-SURGERY - THE RELATION BETWEEN LUNG AND LEG MICROVASCULAR PERMEABILITY TO (111)INDIUM-LABELED TRANSFERRIN AND CIRCULATING MEDIATORS

Background - Aortic surgery is a risk factor for acute lung injury and this may relate to ischaemia/reperfusion (I/R) of the lower body and release of inflammatory mediators. The aim of this study was to define the changes in microvascular protein permeability and circulating inf lammatory mediators after aortic surgery. Methods - In 11 consecutive patients who underwent elective aortic surgery microvascular permeabil ity in lung and leg was measured before and a median of 2.8 hours afte r completion of surgery using (111)indium (In)-labelled transferrin an d (99m)technetium (Tc)-labelled red blood cells, yielding a protein le ak index (PLI) that is specific for protein permeability. Circulating leucocyte counts and levels of inflammatory mediators were determined. Results - In the lung the PLI rose from a median of 0.6 (range -0.5 t o 2.2)x10(-3)/ min before surgery to 5.4 (-2.3 to 33.5)x10(-3)/min aft er surgery, and in the leg from 0.3 (-1.6 to 1.7) x 10(-3)/min to 5.0 (1.0 to 27.8)x10(-3)/min. The increase in PLI in the lung was related to that in the leg. Levels of activated complement C3a and tumour necr osis factor-alpha did not change, but levels of interleukin (IL)-6, IL -8 and elastase-alpha(1)-antitrypsin increased. After surgery there wa s slight neutrophilia and the leucocyte counts were inversely related to the IL-8 level. The rise in lung but not in leg PLI was greatest in patients with the highest IL-8 levels and the lowest leucocyte counts . Conclusions - Early after aortic surgery microvascular protein perme ability increases in the leg and lung. Leg IIR injury may result in ne utrophil activation and release of IL-8, which may induce neutrophil s equestration and subsequently increased pulmonary microvascular permea bility. These findings may help to explain the occurrence of acute lun g injury after IIR in man.