Intravasation of fat from the bone marrow cavity.

Fat labeled with triolein-(131)I was introduced through a burr hole into single tibial marrow cavities and the hole was sealed. The radioactivity over the thorax was monitored for 2-5 hours. After sacrifice, the radioactivity was determined in lungs, injected tibia or leg, kidneys, brain, thyroid gland and blood. Presence of pulmonary embolic fat was verified by histologic methods. Intravasation occurred after closure of the burr hole; it was delayed in several animals and failed to occur in 1 animal. The following mean percentages of the injected activity were found: in lungs 44.8% (0.04-85.1%); in tibia 44.7% (7.1-96.8%); in other investigated tissues and organs collectively, less than 1%. In another group, the tibia was fractured either immediately after injection of the labeled fat and closure of the burr hole, or while intravasation was in progress. After 2-5 hours, the lungs contained 23.2% (0.1-65.6) of the labeled fat, which was significantly less than in animals without fracture. In 2 animals, the needle was sealed into the burr hole, and the pressure necessary to produce intravasation was measued. A pressure of 50-100 mm of H(2)O produced pulmonary fat embolism as rapidly as the fat was injected.