Since venous blood returns to the right heart and is pumped to the lungs for reoxygenation, the fat globules often get lodged in the pulmonary circulation. Fat globules may also pass through lung circulation back into the left ventricle of the heart to be pumped throughout the body in the systemic circulation. They may also reach the systemic circulation through a patent foramen ovale (a hole communicating the right atrium directly to the left atrium of the heart). If fat globules obstruct 80% of the lung capillary network, the resulting back pressure on the right heart increases workload and causes right heart dilatation through cor pulmonale, leading to acute right heart failure. Biochemical theory - Following trauma, an inflammation causes bone marrow to liberate fatty acids into the venous circulation. This is achieved through the increased activity of lipoprotein lipase which break down triglycerides into free fatty acids. Both the release of fatty acids and the inflammation causes damage to the capillary beds of the lungs and other organs, causing interstitial lung disease, chemical pneumonitis, and acute respiratory distress syndrome (ARDS). This theory can help to explain non-traumatic causes of fat embolism. Diagnosis
Fat embolism is presence of fat particles in the micro-circulation of the body. Meanwhile, fat embolism syndrome is the clinical manifestation as the result of fat particles lodging in the body micro-circulation. There are three major diagnostic criteria proposed for fat embolism syndrome, however, none of them are validated and accepted universally.
Administration of corticosteroids for 2 to 3 days is not associated with increased rates of infection. However, there is insufficient data to support the use of methyprednisolone once FES is established.Heparin has been used in the prevention of venous thrombosis in post-operative patients; however its regular use in those with FES has been contraindicated due to increase risk of bleeding in those with polytrauma. Placement of inferior vena cava filters has been proposed to reduce the amount of emboli going into the lung vascular system, however, this method has not been studied in detail. Treatment
Once FES develops,  the person should be admitted into intensive care unit (ICU), preferably with central venous pressure (CVP) monitoring. CVP monitoring would be helpful to guide the volume resuscitation. Supportive treatment is the only proven treatment method. Supplemental oxygen can be given if a person has mild respiratory distress. However, if a person has severe respiratory distress, either continuous positive pressure ventilation (CPAP), or mechanical ventilation using positive end-expiratory pressure (PEEP) may be indicated. Fluid replacement is required to prevent shock. Volume resuscitation with human albumin is recommended because it can restore blood volume in the circulatory system while also binds to free fatty acids in order to reduce lung injuries. In severe cases, dobutamine should be used to support the right ventricular failure. Frequent Glasgow coma scale (GCS) charting is required to assess the neurological progression of a person with FES. A placement of intracranial pressure monitor may be helpful to direct the treatment of cerebral odema.