FAT DROPLETS WITHIN MACROPHAGES OBTAINED BY BRONCHOALVEOLAR LAVAGE - INCIDENCE AND DIAGNOSTIC-VALUE

This study aimed to determine the incidence and diagnostic value of fa t-laden alveolar macrophages obtained by bronchoalveolar lavage (BAL). In 128 patients, including 66 patients admitted for multiple trauma, 158 BAL were carried out. However, 41 BAL from 32 patients were exclud ed because of poor quality of samples (not enough macrophages, too man y ciliated cells, or haemorrhage). All the patients were intubated and mechanically ventilated, having pulmonary infiltrates on the chest fi lm. BAL samples were examined after staining with oil-red-O. They were considered to be positive when more than 5 % of alveolar macrophages contained fat droplets. Among them 14 out of 47 patients (30 %) withou t multiple trauma were positive ; 7/14 had never been given any intrav enous lipid infusion, and 5/14 had aspiration pneumonia (as opposed to 3/32 patients with negative BAL). Further 27 patients out of the 49 ( 55 %) with multiple trauma were positive. Among them 10/49 had clinica l evidence of fat embolism, however, only 7/10 had positive samples. A ll these last ten patients had been given intravenous lipid infusions. The rate of positive alveolar macrophages was correlated neither with the plasma triglyceride concentration, nor the Fracture Index Score, nor the delay between the end of the lipid infusion and the BAL. There was no significant difference in PaO2/FIO2 ratio between the patients with positive and negative BAL. Positive BAL was significantly associ ated with lipid infusions. The data therefore suggest that the presenc e of fat-laden alveolar macrophages are associated with various pathol ogical pulmonary conditions, particularly aspiration pneumonia and lip id infusions. In the polytrauma patient with fat embolism, alveolar fa t droplets is a common event which cannot be considered as pathognomon ic because of numerous false positives in mechanically ventilated pati ents.