FES (fat embolism syndrome) is a clinical problem, and, although ARDS (acute respiratory distress syndrome) has been considered as a serious complication of FES, the pathogenesis of ARDS associated with FES remains unclear. In the present study, we investigated the clinical manifestations, and biochemical and pathophysiological changes, in subjects associated with FES and ARDS, to elucidate the possible mechanisms involved in this disorder. A total of eight patients with FES were studied, and arterial blood pH, P a O 2 (arterial partial pressure of O 2 ), P a CO 2 (arterial partial pressure of CO 2 ), biochemical and pathophysiological data were obtained. These subjects suffered from crash injuries and developed FES associated with ARDS, and each died within 2 h after admission. In the subjects, chest radiography revealed that the lungs were clear on admission, and pulmonary infiltration was observed within 2 h of admission. Arterial blood pH and P a O 2 declined, whereas P a CO 2 increased. Plasma PLA 2 (phospholipase A 2 ), nitrate/nitrite, methylguanidine, TNF-α (tumour necrosis factor-α), IL-1β (interleukin-1β) and IL-10 (interleukin-10) were significantly elevated. Pathological examinations revealed alveolar oedema and haemorrhage with multiple fat droplet depositions and fibrin thrombi. Fat droplets were also found in the arterioles and/or capillaries in the lung, kidney and brain. Immunohistochemical staining identified iNOS (inducible nitric oxide synthase) in alveolar macrophages. In conclusion, our clinical analysis suggests that PLA 2 , NO, free radicals and pro-inflammatory cytokines are involved in the pathogenesis of ARDS associated with FES. The major source of NO is the alveolar macrophages.
Acute pulmonary oedema usually has a fatal outcome. In this clinical report, we present rare cases of pulmonary oedema that were associated with Japanese B encephalitis, lymphangitis in breast carcinoma, fat embolism due to long-bone fracture, and the rupture of cerebral mycotic aneurysms. A total of 18 patients in the four disease categories were collected in two teaching hospitals in Taipei and Hualien. Upon admission, routine and specific examinations were taken and all patients showed clear lungs by chest X-ray; however, signs of acute pulmonary oedema occurred within 7 days. After resuscitation, all patients died of acute pulmonary oedema. In patients with fat embolism, the levels of non-esterified plasma fatty acids, cGMP, 5-hydroxytryptamine (serotonin) and nitrates/nitrites were increased during pulmonary oedema. Immunohistochemical staining revealed virus infection and neuronal death, predominantly in the medial, ventral and caudal medulla in cases of Japanese B encephalitis. The pulmonary oedema due to central sympathetic activation in Japanese B encephalitis may be related to destruction of depressor mechanisms in the medulla. The rupture of mycotic aneurysms is known to cause cerebral compression that results in acute pulmonary oedema. Blockade of lymphatics, capillaries and venules in breast carcinoma with lymphangitis causes the development of rapid lung oedema. The pathogenesis of pulmonary oedema is much more complicated in fat embolism. Mediators such as cGMP, 5-hydroxytryptamine, nitric oxide and presumably other chemical substances may also be involved.