Detrimental effects of experimental fat embolism on the lung: a correlative clinical, histological and histochemical study

Among the many factors responsible for pulmonary damage after major surgery and trauma are free fatty acids. This study was done to find out the acute histological and histochemical changes in the lung of experimentally induced fat embolism syndrome. Oleic acid was injected directly into the right atrium of 10 dogs [study group]. Two dogs were used as control. All dogs were anesthetized, mechanically ventilated and subjected to midline sternotomy. Histological and histochemical study of lung biopsy two hours after embolization revealed narrowed and atelectatic alveoli, plasma and hemorrhagic exudation, hyaline membranes, widened interstitium with massive edema, mononuclear cellular infiltrate, marked congestion of the capillaries and increase in the protein content. There was a definite increase in the activity of both acid and alkaline phosphatase enzymes. This reflected the intensity of the exudative inflammatory reaction and increased vascular permeability, respectively. These findings provided an explanation of the hypoxemia encountered in the clinical settings of respiratory insufficiency following major trauma and surgery and emphasize the role of positive end expiratory pressure to open up the collapsed alveoli