Reamed Intramedullary Femoral Nailing After Induction of an 'ARDS-Like' State in Sheep: Effect on Clinically Applicable Markers of Pulmonary Function

Objectives/Hypothesis: At present, the optimal treatment for appropriately resuscitated, multiply injured patients includes fixation of long bone fractures within twenty-four hours of injury. This management approach has been shown to decrease the incidence of pulmonary complications, multiple organ failure, and death. Some investigators have hypothesized that acute reamed intramedullary nailing of the femur (RIMNF) may result in pulmonary dysfunction as a result of the pulmonary fat embolization generated during this procedure. Patients with concomitant thoracic trauma may be at particular risk for this potentially severe complication. In an attempt to determine whether RIMNF can be safely carried out regardless of the severity of a pulmonary injury, we monitored the pulmonary effects of RIMNF in sheep in which an acute respiratory disorder (ARDS)-like state had been induced. Our hypothesis was that, if the pulmonary fat embolization that occurs as a result of RIMNF has a clinically significant effect, it would be detectable in an animal model in which a severe lung injury had been induced prior to the start of RIMNF. Study Design: This was an acute experimental procedure performed on yearling sheep. Methods: Reamed intramedullary nailing of the femur was performed in two groups of instrumented sheep. The first group had no pulmonary injuries. The second group had an ARDS-like state induced by intravenous infusion of perilla ketone prior to RIMNF. Perilla ketone increases pulmonary microvascular permeability without changing filling pressures and is used to induce a model of human ARDS. Hemodynamic and oximetric parameters were measured or calculated, as was pulmonary dynamic compliance during the experiment. Results: Infusion of perilla ketone caused a significant pulmonary injury. RIMNF caused no additional significant effect on intrapulmonary shunt, mixed venous oxygen saturation, or dynamic compliance, which are clinically used to assess the severity of pulmonary dysfunction in injured patients. Conclusions: The fat embolization that occurs during RIMNF in an appropriately resuscitated sheep has no clinically significant effect on pulmonary function, even in the setting of a severe pulmonary dysfunction.