Fat Embolism Syndrome - Causes, Symptoms, Diagnosis, and Treatment

What Is Fat Embolism Syndrome?

Fat Embolism Syndrome(FES) is the systemic manifestation that occurs when fat particles (fat emboli) enter the bloodstream and block blood circulation. This embolized fat causes tissue damage and produces an inflammatory response, which results in pulmonary, retinal, cutaneous, neurological, and cardiovascular manifestations.

The exact pathophysiology of the condition is unknown. There is no definitive diagnostic test for FES, so diagnosis is difficult. Orthopedic trauma is the most common cause of FES. FES can also occur due to liposuction, pancreatitis, and bone marrow transplant. FES is a rare condition, but subclinical fat embolism (without clinical manifestation) is common among trauma patients.

What Are the Causes?

Orthopedic trauma (fracture of bone, joints, and soft tissue) is the most common cause of FES. The risk for developing FES is more in cases of fracture of the femur bone and also in cases of multiple fractures. FES can occur at any age but is rare in children.

Other than in orthopedic fractures, FES may occur in the following conditions:

• Bone marrow transplantation.

• Osteomyelitis (a serious but rare bacterial/fungal bone infection).

• Liposuction (surgical removal of excess body fat).

• Alcoholic fatty liver.

• Pancreatitis (inflammation of the pancreas).

• Severe burns.

• Following knee or hip replacement.

• Sickle cell anemia.

What Is Pathophysiology?

The exact pathophysiology is still unclear. The fat emboli that enter the bloodstream damage the capillary bed. Pulmonary(lung) circulation is affected the most, but it can also occur in the eyes, skin, brain, and heart microvasculature. Two theories explain the formation of fat emboli.

These theories are:

• Mechanical Theory: Mechanical theory suggests that as a result of trauma, direct release of bone marrow into the venous system occurs. The fat is released from open venous sinusoids. Fat embolization takes place in the capillary bed. This theory explains fat embolism within pulmonary capillaries.

• Biochemical Theory: Biochemical theory suggests that following trauma, free fatty acids are released from the bone marrow into the venous system. The inflammatory response following trauma and elevation of free fatty acid levels result in the damage of capillary beds. The free fatty acid is associated with inflammation within the lungs and hypoxemia (insufficient blood oxygen levels).

What Are the Signs and Symptoms?

FES can affect microcirculation in the lungs, skin, retina, brain, kidney, liver, and heart. Pulmonary circulation is most commonly affected. Symptoms depend on the organ system that is affected.

The symptoms include:

• Respiratory depression (ranges from mild hypoxemia to ARDS (Acute Respiratory Distress Syndrome).

• Fever.

• Tachypnea (abnormally rapid breathing).

• Tachycardia (increased heart rate).

• Petechial rashes(pinpoint round red/purple dots).

• Lethargy.

• Confusion.

• Restlessness.

• Anemia.

• Decrease in platelet count.

• Changes in Glasgow coma scale due to cerebral edema.

• Jaundice.

In severe cases, DIC (Disseminated Intravascular Coagulation) occurs. Fulminant cases can result in ARDS, shock, and death.

What Are the Diagnostic Tests Done?

1. There are no specific diagnostic tests for FES. Moreover, there are no pathognomonic features for the condition. Most of the cases present with respiratory distress that is indistinguishable from ARDS (Acute Respiratory Distress Syndrome). FES should be suspected in high-risk patients (having a high risk for FES) when they develop respiratory distress or petechial rashes.

2. As there are no pathognomonic features and gold standard diagnostic tests for the condition, researchers have come forward with some diagnostic criteria. One such criterion is Gurd and Wilson’s criteria. The criteria include major and minor criteria. The presence of any two major criteria or one major and four minor criteria suggests FES.

Gurd and Wilson’s Criteria:

Major Criteria-

• Respiratory distress.

• Neurological symptoms in patients without head injury.

• Petechial rashes.

Minor Criteria-

• Fever.

• Decrease in hemoglobin level.

• Decrease in platelet count.

• ESR (Erythrocyte Sedimentation Rate) elevation.

• Jaundice (a condition characterized by an elevation in bilirubin levels and yellowing of the skin, mucous membrane, and sclera of the eye).

• Increased heart rate.

• Renal changes.

• Retinal changes.

• Fat in sputum.

1. Chest X-rays: Chest X-rays show patchy infiltrates on both lungs, similar to ARDS, which is difficult to differentiate from pulmonary edema. In other cases, chest X-rays may be interpreted as normal.

2. MRI(Magnetic Resonance Imaging)- MRI of the brain shows punctate diffuse and hyperintense lesions.

3. Bronchoalveolar Lavage- Some studies have shown bronchoalveolar lavage samples that show greater than 30 % alveolar cells stained for neutral fat indicate FES.

4. A fundoscopic examination may reveal retinal hemorrhage.

What Are the Treatment Options?

There is no specific treatment for the condition, and the treatment is mostly supportive.

The treatment options for FES include:

• Corticosteroid Therapy: Corticosteroids reduce inflammation and limit free fatty levels. Methylprednisolone is the commonly used steroid for FES therapy. Corticosteroids are also used for FES prophylaxis in long bone fracture cases.

• Anticoagulants (Blood Thinners): Anticoagulant therapy prevents blood clot formation. But, it is not widely used, and more studies are required on the same.

• Inferior Vena Cava Filters: The placement of inferior vena cava filters reduces the embolization of pulmonary vasculature.

• Intracranial Pressure Monitor: Intracranial pressure monitor placement is used in the case of FES patients with cerebral edema.

• Fluid Resuscitation: Fluid resuscitation is required in the case of hypovolemic patients.

• Supplemental Oxygen/Mechanical Ventilation: To compensate for low oxygen levels, supplemental oxygen or mechanical ventilation may be required.

What Is the Prognosis?

The prognosis of FES is generally favorable. The prognosis is favorable due to supportive care and early fixation of long bone fractures. The mortality rate of FES is less than 10 %. Complete recovery from neurological, dermatological, and pulmonary manifestations is possible.

What Are the Preventive Measures?

The most common cause of FES is a long bone fracture or multiple unstable fractures. Early fixation of long bone fractures within 24 hours will reduce the risk of FES. Some studies show corticosteroid therapy (Methylprednisolone) to be effective in FES prophylaxis.

Conclusion

FES includes the systemic manifestations that occur following fat embolism in the microvasculature. Though fat embolism is common in trauma patients, FES is rare. FES is most common in orthopedic trauma cases. There are no definitive diagnostic tests nor any definite treatment for the condition. However, the prognosis is favorable in most cases due to early fixation of long bone fracture and supportive therapy.