A Case of Fatal Paradoxical Fat Embolism Syndrome Detected by Intraoperative Transesophageal Echocardiography

Abstract

We report a case of paradoxical fat embolism syndrome (PFES) detected by intraoperative transesophageal echocardiography (TEE). Case Report A 30-yr-old male truck driver with no history of cardiac or cerebral disease was admitted to the intensive care unit after his truck was struck by another truck from behind, and the dashboard trapped him. On arrival, he had no apparent neurological deficit, with normal findings on brain computed tomography (CT). Tachypnea (36 breaths/min), tachycardia (81 bpm), and hypercapnia (Paco2: 55.0 mm Hg) with normal oxygenation and normal arterial blood pressure were observed. Surgery was performed to fixate the closed fractures of the right femoral shaft fracture with intramedullary nails (with 12-mm diameter and 38-cm length) during general anesthesia. Approximately 90 min after starting the operation, a decreased end-tidal CO2 and oxygen saturation (Spo2) occurred followed by hypercapnia, hypoxia, tachycardia, hypotension, and pulmonary hypertension (pulmonary artery pressure was 46/29 mm Hg). TEE revealed multiple small vesicles in all four heart chambers (Fig. 1), marked pulmonary artery dilation, and depression of contraction of the right ventricle. PFES was strongly suspected, and the operation was completed as quickly as possible.Figure 1: Transesophageal echocardiographic four-chambers’ view, showing massive fat emboli in the left atrium (LA), left ventricle (LV), and Aorta (Ao). Shown are multiple small echogenic vesicles in the LA, LV, and Ao. Contraction of the right ventricle (RV) was decreased, and ventricular septum was overhung toward the LV.Postoperatively, the patient remained in a coma. Brain CT findings were almost the same as those of preoperative examination both immediately after, and 3 h after, the operation. However, there was severe global edema in both cerebral hemispheres at 8 h after the operation. After hypothermic therapy with a blood temperature of 34°C for 3 days, the patient remained in a coma; cerebral edema was observed on brain CT, which did not improve. Contrast TEE using plasma protein fraction revealed the appearance of microbubbles in both atria almost simultaneously. However, the location of the shunt was not identified by color Doppler echocardiography. Phagocytosis of fat vesicles by macrophages was also demonstrated in both pulmonary and arterial blood samples (Fig. 2) and a bronchoalveolar lavage fluid sample. The patient died on the ninth hospital day of severe hypotension caused by brain herniation. The request to perform an autopsy was denied by his family.Figure 2: Phagocytosis of fat vesicles by macrophages was demonstrated in arterial blood samples on the second hospital day. The triangle shows macrophages, including fat vesicles with Sudan stain.Discussion Intraoperative TEE yields real-time information on the frequency of embolic events during intramedullary procedures (1–3). In our case, the appearance of fat vesicles was observed continuously independently of surgical manipulations. However, it was difficult to distinguish between fat particles and microbubbles. No definitive treatment for PFES has been established. It has generally been reported that early stabilization of fracture sites decreases the incidence of fat embolism (4). When PFES is suspected, intramedullary procedures should be discontinued and other treatment options for long-bone fracture considered (5,6). We selected general anesthesia for the patient, because massive intraoperative bleeding was anticipated. However, mechanical positive-pressure ventilation would increase both intrathoracic pressure and right atrial pressure, possibly causing functional right-to-left shunt. One possible option to prevent an increase in intrathoracic pressure would be the use of other anesthetic techniques, such as continuous epidural or spinal anesthesia.