QuestionSBA
QuestionChoice
A pulmonary embolism is an important differential for post operative hypoxia, especially in the context of orthopaedic patients where mobility may be dramatically reduced. However, pulmonary emboli usually present later in the post-operative period, with the highest risk being 1-5 weeks after an operation. This is since it takes time for the deep vein thrombus to form. Furthermore, pulmonary emboli are not associated with petechial rashes.
53318
b
Pulmonary embolism
QuestionChoice
Atelectasis post operatively may result in lung collapse and respiratory distress. It is a good differential diagnosis, but the presence of equal breath sounds, a central trachea (which may be deviated in a collapse), and a petechial rash, make this less likely.
53321
e
Atelectasis
QuestionChoice
Compartment syndrome presents with pain out of proportion to any clinical signs and passive stretch in the early stages. Progression leads to pallor, pulselessness, and paraesthaesia as the bloody supply to the limb is compromised. The pain typically does not responding to any analgesia. This can occur after limb trauma because muscle swelling and inflammation increases the pressure in the muscle compartment. This is an orthopaedic emergency which must be diagnosed and treated immediately as it can potentially result in loss of blood supply to the limbs if untreated. Patients with compartment syndrome would not present primarily with respiratory distress as in this case.
53319
c
Compartment syndrome
QuestionChoice
A pneumothorax is an important differential to exclude in this context, especially after trauma. It is likely this patient would have had a trauma series CT scan performed on presentation, which would image the thorax, and he would also likely get repeat chest imaging after being observed to be more short of breath during the ward round to rule this out. However, given the equal breath sounds on clinical examination and the presence of a petechial rash, this is unlikely. A tension pneumothorax may present with haemodynamic instability and shock, and warrants immediate needle decompression without delay. This patient has a central trachea, making this unlikely.
53320
d
Pneumothorax
QuestionChoice
A fat embolism is a potential complication of long bone fractures. Patients present with respiratory distress, a petechial rash, and haemodynamic instability. It may occur 24-72 hours after the initial injury. Management is supportive.
53317
a
Fat embolism
Concept
Chapter
# Summary

Fat embolism refers to a medical condition characterized by the entry of fat fragments into the systemic circulation, subsequently lodging in the small vessels of the lungs or other tissues. This typically occurs due to fractures, especially long bone fractures. Clinical manifestations vary depending on the site of embolism, with breathlessness being a common symptom in pulmonary fat embolism. Investigations may include radiographic imaging and serum markers. The mainstay of management is supportive care, focused on oxygenation and symptomatic relief.

# Definition

Fat embolism is a clinical syndrome resulting from the dissemination and subsequent lodgment of fat droplets or fat globules in the small vessels of the systemic and/or pulmonary circulation. This event typically follows trauma, particularly fractures of long bones or pelvic bones, but it can also occur after non-traumatic events such as orthopedic surgery or severe burns.

# Epidemiology

The incidence of fat embolism varies and is largely dependent on the context. It is estimated to occur in 1-3% of all long bone fractures, but the incidence can be as high as 10-30% in patients with polytrauma or after major orthopedic surgeries. Fat embolism syndrome, a severe manifestation of fat embolism characterized by multisystem involvement, is estimated to occur in approximately 10% of all cases of fat embolism.

# Aetiology

The aetiology of fat embolism generally involves:

-   Trauma, particularly long bone and pelvic fractures
-   Non-traumatic events such as orthopedic surgeries (hip or knee arthroplasty)
-   Severe burns
-   Liposuction
-   Prolonged corticosteroid therapy

# Signs and Symptoms

The signs and symptoms of fat embolism are largely determined by the site of embolization:

-   Pulmonary: Breathlessness, hypoxia, tachycardia, tachypnea, and fever
-   Neurologic: Altered mental status, seizures, focal deficits, or coma
-   Dermatologic: Petechial rash predominantly on the upper body

# Differential Diagnosis

Differential diagnosis for fat embolism includes conditions that present similarly such as:

-   Pulmonary embolism: Presents with sudden onset shortness of breath, chest pain, and hemoptysis.
-   Acute respiratory distress syndrome (ARDS): Presents with severe shortness of breath, rapid breathing, and bluish skin coloration (cyanosis).
-   Pneumonia: Presents with cough (often productive), fever, shortness of breath, and chest discomfort.
-   Sepsis: Presents with fever, increased heart rate, increased respiratory rate, and confusion.

# Investigations

The diagnosis of fat embolism is typically clinical, supported by relevant investigations:

-   Imaging studies: Chest X-ray may reveal diffuse bilateral infiltrates; CT of the chest may show fat within the vessels.
-   Laboratory tests: Serum markers such as fat macroglobulinemia, increased serum lipase, and increased serum LDH.
-   Bronchoalveolar lavage: To identify fat droplets in macrophages.

# Management

Management of fat embolism is primarily supportive and includes:

-   Oxygen therapy: To relieve hypoxia and dyspnea.
-   Fluid resuscitation: To maintain hydration and support circulatory function.
-   Pharmacological therapy: Prophylactic low-molecular-weight heparin may be considered to prevent thromboembolic events.
-   Fracture stabilization: Early immobilization of fractures can reduce the incidence of fat embolism.

# References

-   [Ortho Bullets: Fat Embolism Syndrome](https://www.orthobullets.com/basic-science/9055/fat-embolism-syndrome)
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1127
Fat embolism
Topic
37
Orthopaedics
Condition
387
Lower limb fractures
UkmlaTopic
16
Musculoskeletal
10724
Fat embolism syndrome can occur after long bone fractures, presenting with respiratory distress, petechial rash, and haemodynamic instability within 24-72 hours post-injury.
A 32-year-old male presents with bilateral fractures of the tibia following a road traffic accident. He undergoes operative management and is reviewed the following day on the ward round. On examination, he is unable to speak in full sentences and is visibly short of breath. There are equal breath sounds bilaterally on chest auscultation and his trachea is central. He has a petechial rash across his body. His vital signs are: HR 120bpm, oxygen saturations 90% on room air, RR of 33, BP 95/43, and temperature 36.5.

Which of the following is the most likely diagnosis?
a