Interleukin-6 as an early marker for fat embolism

Abstract

Background: Fat Embolism is a complication of long bone fractures, intramedullary fixation and joint arthroplasty. It may progress to fat embolism syndrome, which is rare but involves significant morbidity and can occasionally be fatal. Fat Embolism can be detected at the time of embolization by transoesophageal echocardiography or atrial blood sampling. Later, a combination of clinical signs and symptoms will point towards fat embolism but there is no specific test to confirm the diagnosis. We investigated serum Interleukin-6 (IL-6) as a possible early marker for fat embolism.

Methods: An animal study was conducted to simulate a hip replacement in 31 adult male Sprague Dawley rats. The procedure was performed under general anesthesia and the animals divided into 3 groups: control, uncemented and cemented. Following surgery and recovery from anaesthesia, the rats allowed to freely mobilize in their cages. Blood was taken before surgery and at 6 hours, 12 hours and 24 hours to measure serum IL-6 levels. The rats were euthanized at 24 hours and lungs removed and stained for fat. The amount of fat seen was then correlated with serum IL-6 levels.

Results: No rats in the control group had fat emboli. Numerous fat emboli were seen in both the uncemented and cemented implant groups. The interleukin levels were raised in all groups reaching a peak at 12 hours after surgery reaching 100 pg/ml in the control group and around 250 pg/ml in the uncemented and cemented implant groups. The IL-6 levels in the control group were significantly lower than any of the implant groups at 12 and 24 hours. At these time points, the serum IL-6 correlated with the amount of fat seen on lung histology.

Conclusion: Serum IL-6 is a possible early marker of fat embolism.

Figure 1

Kirschner wire being advanced into the femoral canal.

Figure 2

Cement being injected into the medullary canal using a syringe.

Figure 3

Fat emboli seen in the 3 different groups.

Figure 4

Presence of fat (stained black) in the lungs of the rat. There are numerous inflammatory cells and red blood cells seen outside the capillaries.

Figure 5

Serum Interleukin-6 levels plotted at 4 different time points.

Figure 6

Serum IL-6 values against time between the cemented and uncemented group after values from the control group were subtracted from the corresponding values.