Fat embolism syndrome is a rare but serious complication of long bone fractures or multiple trauma. It is the consequence of the dissemination of fatty particles in the blood microcirculation. It can cause major respiratory, neuro-psychic and skin disorders in a few hours or a few days, fortunately reversible in the majority of cases.

Definition

Fat embolism occurs when micro-droplets of insoluble fat block small vessels. It is most often localized in the pulmonary circulation (pulmonary fatty embolism). However, peripheral vessels can also be blocked, for example in the brain or kidneys (systemic fat embolism).

Small fatty embolisms in the microcirculation can go unnoticed. But in trauma – rarely in other circumstances – massive vascular obstruction can cause fat embolism syndrome, characterized by respiratory distress, impaired brain function and hematological disturbances. The cure is most often total in 15 days but respiratory or neuro-psychic sequelae cannot be ruled out.

Causes

Most often, fat particles enter the bloodstream when a bone fracture brings the bone marrow into contact with an injured blood vessel. More rarely, the initial lesion affects soft tissues such as fatty tissue reserve or the liver. Under certain conditions, fatty deposits can form in the absence of lesion.

During the journey of the fatty particles, the lung is the first organ encountered where they are found blocked in the microcirculation. But sometimes they manage to pass through the large circulation, called systemic circulation, which irrigates the rest of the body. The obstruction of the vessels can therefore also occur in the brain, skin, eye, kidneys or heart.

Coagulation disorders are responsible for an aggravation of the obstruction of the microcirculatory network, leading to a sudden interruption in the supply of oxygen to the tissues (ischemia). The action on fatty deposits of a pulmonary enzyme, lipase, also releases toxic fatty acids causing tissue damage. Fat embolism syndrome results from all of these phenomena.

Diagnostic

The diagnosis is very difficult because the manifestations are variable and not very specific. It is essentially based on the attention paid to clinical signs by the practitioner. 

Different tests can be useful, but they do not allow the diagnosis to be confirmed with certainty.

• Chest x-ray sometimes reveals bilateral opacities in the lungs, but difficult to distinguish from pulmonary edema. 
• Brain MRI can make it possible to distinguish a large fatty mass or present the image of a constellation of lesions.
• The fundus may show scintillating deposits corresponding to fatty globules.
• The measurement of gases in the blood measures the fall in the level of oxygen in the blood.
• The blood test (blood count) shows anemia and low blood platelet counts.
• Blood and urine tests can detect the presence of fatty droplets.
• Bronchopulmonary lavage reveals certain lipid abnormalities.

Various other examinations are performed depending on the symptoms: pulmonary scintigraphy, computed tomography, electro-cardiogram, etc.

The people concerned

Fat embolisms occur in trauma victims 95% of the time. They more often affect men than women, and preferentially young people. In 90% of cases, they suffered a fracture of a long bone, most often located in the femur. Shin fractures or double leg fractures, and to a lesser extent multiple trauma to the pelvis, upper limb and ribs can also be responsible.

Rarely, fat embolism occurs after liposuction, hepatic trauma, bone marrow transplantation, kidney transplantation or in severe burns.

Risk factors

In trauma patients, various situations favor the occurrence of fatty embolism:

• the multiplicity of fractures,
• the presence of closed fractures with significant displacement,
• persistent hypovolemic shock;
• poor restraint of the bill hearth,
• association with visceral lesions …

Certain diseases constitute a favorable ground for fatty embolisms:

• necrotic and hemorrhagic pancreatitis,
• alcoholic fatty liver disease,
• diabetes
• severe infections …

Finally, certain medical situations can constitute risk factors: prolonged infusion of propofol, establishment of extracorporeal circulation, etc.

Warning signs

The first signs can appear within hours or days. A high fever, an increase in the respiratory rate (polypnea), a persistent anemia or a blood oxygen deficit (hypoxemia) are likely to alert practitioners.

Respiratory manifestations

Respiratory manifestations are present in over 90% of cases, accompanied by tachychardia. They present themselves in the form of short and rapid breathing (tachypnea), breathing difficulties (dyspnea), or even acute respiratory failure or “cor pulmonale”, that is to say a dysfunction of the heart pump as a result of increased pressure in the pulmonary arteries. In the most serious cases, they cause cardio-respiratory arrest.

Manifestations neuropsychiques

These are mainly disorders of vigilance: disorientation, agitation, confusion, delirium, coma …

Cutaneous and mucous membrane damage

Small red-purplish spots, petechiae, appear very frequently between the second and fourth day.

Damage to the oral and conjunctive mucous membranes is frequent.

There is no specific treatment.

Symptomatic treatment is based mainly on respiratory resuscitation. Advances in the management of respiratory distress syndrome have significantly improved the prognosis.

In the absence of treatment, prevention has a key role to play. Fractures should be reduced if possible within 24 hours of an accident. Surgical procedures must also be adapted to the risk factors. The management of pain and stress should not be forgotten.

The effectiveness of preventive drug treatments, including corticosteroids, is not confirmed.