Ultrasound destruction of air microemboli as a novel approach to brain protection in cardiac surgery

摘要

Objective: Evaluation of a novel approach to eliminate air microemboli from extracorporeal circulation via ultrasonic destruction. Design: In vitro proof-of-concept study. Setting: Research laboratory. Participants: None. Interventions: None. Measurements and Main Results: An extracorporeal circulation device was filled with human blood circulating at 3 L/min. Air bubbles were injected into the system. For bubble destruction, the blood in the tubing system was repeatedly insonated for 3 minutes using a therapeutic 60-kHz device, with variation of intensity and duty cycle settings, ranging from 0.2 W/cm2 to 1.0 W/cm2 and from duty cycle 60% to continuous wave (CW). Number and diameter of air microemboli were counted upstream and downstream of the ultrasound device by a 2-channel microemboli Doppler detector. For safety assessment, circulating blood was insonated continuously for 2 hours at 0.8 W/cm2 CW and compared with circulation without insonation; and standard blood parameters were analyzed. Without treatment, 1,313 to 1,580 emboli were detected upstream, diameter ranging between 10 and 130 μm. Ultrasound treatment eliminated up to 87% of all detected bubbles in cw application (p0.01) and showed comparable effects at intensities from 0.4 W/cm2 to 1.0 W/cm2 cw. Bubbles sized 15 μm almost were eliminated completely (p0.001). Pulsed wave application rendered inferior results (p0.05). No relevant changes of blood parameters were observed compared with control circulation. Conclusions: Ultrasound destruction of air emboli is a very efficient method to reduce number and size of emboli. Within the limits of safety assessment, the authors could not detect relevant side effects on standard blood parameters.