抄録
Purpose: High-intensity transient signals (HITS) are commonly detected during cardiopulmonary bypass (CPB) . However, the clinical significance of HITS during CPB is still controversial. Micro-bubbles are reported to produce HITS of more than 400-500 Hz. We attempted to elucidate the incidence of HITS exceeding 400 Hz during CPB. Methods: The subjects were 6 patients who underwent open heart surgery using CPB. HITS were detected by TC2020, PIONEER (Nicolet /EME) with a 2.0-MHz pulsed Doppler probe at the middle cerebral artery. Transesophageal echocardiography (TEE) was undertaken during the operation. Results: The total number of HITS during CPB was 1707±1392 (n=6) . Of the total HITS, 88.1±6.8% had a frequency of more than 400 Hz. On the other hand, HITS of less than 400 Hz were frequently detected at aortic cannulation, aortic decannulation and aortic cross-clamping. HITS of more than 400 Hz were detected in cases showing cardiac or aortic micro-bubbles in TEE. Conclusion: The present findings suggest that the majority of HITS during CPB reflect micro-bubbles, and that aortic manipulation may be related to the formation of solid micro-emboli. HITS frequency analysis may be useful for differentiating between micro-bubbles and solid micro-emboli formed during CPB.
