Abstract: Objective · To evaluate if ultrasound acoustic force can reduce cerebrovascular micro-emboli after cardiac surgery.  Methods · Seven pigs were used during the experiment, three for air emboli injection, three for solid emboli injection, and one for safety study. After anesthesia, right carotid artery, left atrial appendage, ascending aorta, and proximal innominate artery were exposed surgically. An intravenous catheter was inserted into left atrial appendage for injecting air or solid micro-emboli. The ultrasound transducer was placed at the bifurcation of the aorta and the innominate artery, with the sonic beacon toward the descending aorta. Micro-emboli through the right carotid artery were monitored by ultrasound transducer. Micro-emboli mixture (10 mL, air emboli or solid emboli) was injected with or without ultrasonic activation, each repeating three times. Micro-emboli through right carotid artery were measured under each condition. Ultrasonic time-intensity curves were performed and analyzed. For safety test, ultrasound with the same energy on a pig for 5 minutes was applied. The tissue samples were obtained for pathological evaluation from sonicated and non-sonicated areas of the aorta, trachea and the esophagus.  Results · Ultrasonic time-intensity curve showed that the mean ultrasonic intensity of the right common carotid artery significantly decreased after ultrasonic activation. The intensity of air emboli reduced from 128.8±32.7 to 56.4±21.1 (P=0.000), while the intensity of solid emboli reduced from 109.8±19.9 to 75.4±21.9 (P=0.000). H-E staining of the surrounding tissues showed no differences between sonicated and nonsonicated areas of the aorta, trachea and the esophagus.  Conclusion · Ultrasonic acoustic force can decrease the number of micro-emboli that enter the brain. Thus, it may lower the risk of postoperative neurological complications after cardiac surgery.

Key words: ultrasonic radiation, micro-emboli, cardiac surgery, complication