Other criteria for diagnosis have been suggested, including those published by Lindeque et al, which focuses primarily on the respiratory characteristics, and a more recent set of semiquantitative diagnostic criteria called the fat embolism index, published by Schonfeld et al.7,8 Schonfeld’s scoring index accounts for the major signs and symptoms of fat embolism syndrome and weighs them according to relative specificity. A score of 5 or more is required for diagnosis of fat embolism syndrome. Table 2 compares the three sets of criteria used for diagnosis of fat embolism syndrome.
Treatment. The treatment of fat embolism syndrome is supportive. Most often, this requires supplemental oxygen for hypoxia and, possibly, fluid resuscitation in the case of hypovolemia. Occasionally, though, these relatively minor supportive therapies need to be escalated to bipap or even full ventilatory support and vasopressors in the more severe cases.
Based on the premise that steroids will attenuate the inflammatory reaction to free fatty acids within the lung, steroids have been tried in the treatment of fat embolism syndrome. However, there are no studies that clearly show benefit with their use.
Prevention. Most of the methods of prevention involve surgical intervention rather than medical therapy. Because microscopic fat emboli are showered during manipulation of long-bone fragments, early immobilization of fractures is recommended, and operative correction rather than conservative management is the preferred method.2,3 One report estimates a 70% reduction in pulmonary complications from this intervention alone.9
Further, two surgical techniques are debated as possible means of preventing fat embolism syndrome. The first is “venting,” in which a hole is made distal to the site of intramedullary nail placement. This reduces intramedullary pressure elevation and, therefore, extravasation of fat into the circulation.10 The second technique is the use of a reamer, irrigator, aspirator (RIA) device. A reamer is a tool used to create an accurate-sized hole for an intramedullary nail. Reaming before intramedullary nail placement can release fat deposits into the circulation. The RIA device irrigates and aspirates resident fat deposits as it reams the canal, releasing fewer deposits into the circulation.11 At this time, these two techniques are considered but not used routinely by surgeons.
Corticosteroids remain a debated method of prevention of fat embolism syndrome. A number of smaller studies suggest steroid therapy might reduce the incidence of fat embolism syndrome and hypoxia; a 2009 meta-analysis pooling nearly 400 patients from these smaller studies found such results.12 Unfortunately, the included studies were noted to be of poor quality, and no change in mortality was found. These results, combined with the possibility of poor wound healing or infection as a complication of steroid use, keep steroids from being used routinely to prevent fat embolism syndrome.
Clinical course. The severity of fat embolism syndrome ranges from mild transient hypoxia with confusion to progressively worsening symptoms leading to acute respiratory distress syndrome and coma. Bulger et al found a 7% mortality rate in this population.1 Less commonly, patients have a fulminant presentation with symptom onset less than 12 hours after injury. With this presentation, patients have a higher rate of mortality—as high as 15%.13
Back to the Case
This young man with bilateral long-bone fractures was at high risk of developing fat embolism syndrome. As is recommended, he was quickly taken to the operating room for fracture stabilization with open reduction and internal fixation. In addition, a RIA device was used to decrease intramedullary pressure. Nonetheless, within the first two days of injury, he developed hypoxia and confusion. These clinical changes were associated with an unexpected drop in hematocrit.
Chest X-ray and high-resolution computed tomography did not reveal a cause of his hypoxia. Similarly, laboratory evaluation for a reversible cause of encephalopathy was negative. A Sudan stain of his urine revealed free fat globules. Though he did not develop axillary petechiae, this clinical picture is consistent with fat embolism syndrome based on Gurd’s criteria. He was supported with oxygen therapy, and he stabilized without further complications.