The differences between venous air embolism and fat embolism in routine intraoperative monitoring methods, transesophageal echocardiography, and fatal volume in pigs.

Background: Venous air embolism (VAE) or fat embolism (FE) may occur in similar clinical settings such as after multiple injuries or total hip replacement. We designed this study to observe the differences between VAE and FE in routine intraoperative monitoring methods, transesophageal echocardiography (TEE), and fatal volume in pigs. Methods: Sixteen domestic pigs were randomly assigned to either a fat group (n = 8) or an air group (n = 8). Each animal was injected with a series of volumes of air or fat. TEE and routine intraoperative monitoring were used during the experiment. The echogenic pattern of air or fat emboli were recorded and was graded (grade 0, no emboli; grade 1, a few fine emboli; grade 2, embolic masses less than 5 mm in diameter and the right atrium opacified with echogenic materials; grade 3, fine emboli mixed with large embolic masses greater than 5 rum in diameter or serpentine emboli). Precordial auscultation was performed before and after each injection of air or fat. The fatal volumes of air and fat were recorded. Results: No echogenic pattern grade 3 on TEE in the fat group was observed even fatal volume of fat was injected, whereas echogenic pattern grade 3 was found in all pigs in the air group when >= 0.5 mg/kg of air was injected (0/8 vs. 8/8, p < 0.01). Paradoxical embolism and cutaneous petechiae was more common in the fat group than in the air group (8/8 vs. 1/8, 6/8 vs. 0/8, p < 0.05). "Bubble-like" sounds, "drum-like" murmurs, and "mill-wheel" murmurs were only heard in the air group but not in the fat group (8/8 vs. 0/8, p < 0.01). Fatal volume of air was much higher than that of fat (4 mL/kg +/- 0.76 mL/kg vs. 0.24 mL/kg +/- 0.05 mL/kg, P < 0.01). Conclusions: Large extensive echogenic masses on TEE, "bubble-like" sounds, "drum-like" murmurs, and "mill-wheel" murmurs were more likely associated with VAE. All of fat emboli were fine on TEE. Paradoxical embolism and cutaneous petechiae were more common in FF. Fatal volume of fat is lower than that of air.