Fat Embolism Score Calculator

How does this fat embolism score calculator work?

This health tool consists of two methods of FES diagnosis with their own criteria and method of interpretation. The first tab uses Schonfeld’s criteria for fat embolism with 7 items, each awarded a number of points as explained:

■ Petechiae (5 points);

■ X-ray chest diffuse infiltrates (4 points);

■ Hypoxemia (3 points);

■ Fever (1 point);

■ Tachycardia (1 point);

■ Tachypnea (1 point);

■ Confusion (1 point).

Positive diagnosis of FES in the Schonfeld method has a cut off of 5 points.

The second tab in the fat embolism score calculator consists of Gurd's and Wilson's criteria:

Major criteria:

■ Axillary or subconjunctival petechiae;

■ Hypoxaemia (PaO₂ <60 mm Hg; FIO₂ = 0.4);

■ Central nervous system depression disproportionate to hypoxaemia;

■ Pulmonary oedema.

Minor criteria:

■ Tachycardia >110 bpm;

■ Pyrexia >38.5°C;

■ Emboli present in the retina on fundoscopy;

■ Fat present in urine;

■ A sudden inexplicable drop in haematocrit or platelet values;

■ Increasing ESR;

■ Fat globules present in the sputum.

Positive diagnosis after Gurd's and Wilson's criteria requires at least one major criteria and four minor criteria being present.

Fat embolism syndrome is a serious condition (with 15% mortality left untreated) and is diagnosed by non specific tests and universal criteria therefore clinical judgment in individual cases should trump.

Fat embolism guidelines

FE is characterized by hypoxia, bilateral pulmonary infiltrates and an altered mental status. Basically it refers to the presence of fat droplets in the lung microcirculation that can lead to clinical sequelae.

FES, the syndrome is the manifestation of fat embolism with clinical signs such as petechial rash, or progressive respiratory insufficiency. FES usually occurs within 24 hours of injury.

Most common causes are trauma and orthopedic injuries with a 3-4% incidence in isolated bone trauma and 10-15% incidence in polytrauma. However, studies have correlated some non traumatic conditions with FE occurrence, such as diabetes and pancreatitis.

Incidence is greater in adults in general (men in particular, due to proneness of being involved in high velocity trauma causing accidents) because children’s bone marrow contains more hematopoietic tissue and less fat thus decreasing risk of fat embolization.

FES is the inflammatory response of the body to the presence of embolized fat globules. There are two theories explaining the creation of the fat globules, the first sources them in the bone marrow fat as they are released by the mechanical trauma and the second is a metabolic theory sourcing the fat from changes in chylomicrons due to cellular stress caused by trauma.

For diagnosis, the main laboratory work performed is:

■ ABG – revealing an increase in pulmonary shunt fraction alveolar to arterial oxygen difference;

■ Hematocrit, platelet count, fibrinogen – revealing thrombocytopenia, anemia and hypofibrinogenemia;

■ Microglobulinemia – required test when applying Gurd’s criteria.

Imaging used in diagnosis:

■ Chest radiography – revealing the bilateral pulmonary infiltrates;

■ CT – revealing petechial hemorrhages indicating microvascular injury.

References

1) Akhtar S. (2009) Fat embolism. Anesthesiol Clin; 27(3):533-50

2) Gurd AR, Wilson RI. (1974) The fat embolism syndrome. J Bone Joint Surg Br; 56B(3):408-16.

3) Glazer JL, Onion DK. (2001) Fat embolism syndrome in a surgical patient. J Am Board Fam Pract; 14(4):310-3.

4) Nandi R, Krishna HM, Shetty N. (2010) Fat Embolism Syndrome Presenting as Sudden Loss of Consciousness. J Anaesthesiol Clin Pharmacol; 26(4): 549–550.