Effect of CO 2 Insufflation on the Number and Behavior of Air Microemboli in Open-Heart Surgery

Abstract

Background— The risks that the presence of air microemboli implies in open-heart surgery have recently been emphasized by reports that their number is correlated with the degree of postoperative neuropsychological disorder. Therefore, we studied the effect of CO 2 insufflation into the cardiothoracic wound on the incidence and behavior of microemboli in the heart and ascending aorta. Methods and Results— Twenty patients undergoing single-valve surgery were randomly divided into 2 groups. Ten patients were insufflated with CO 2 via a gas diffuser, and 10 were not. Microemboli were ascertained by intraoperative transesophageal echocardiography (TEE) and recorded on videotape from the moment that the aortic cross-clamp was released until 20 minutes after end of cardiopulmonary bypass (CPB). The surgeon performed standard de-airing maneuvers without being aware of TEE findings. Postoperatively, a blinded assessor determined the maximal number of gas emboli during each consecutive minute in the left atrium, left ventricle, and ascending aorta. The 2 groups did not differ in the usual clinical parameters. The median number of microemboli registered during the whole study period was 161 in the CO 2 group versus 723 in the control group ( P <0.001). Corresponding numbers for the left atrium were 69 versus 340 ( P <0.001), left ventricle 68 versus 254 ( P <0.001), and ascending aorta 56 versus 185 ( P <0.001). In the CO 2 group, the median number of detectable microemboli after CPB fell to zero 7 minutes after CPB versus 19 minutes in the control group ( P <0.001). Conclusions— Insufflation of CO 2 into the thoracic wound markedly decreases the incidence of microemboli.