Effect of CO2 Insufflation on the Number and Behavior of Air Microemboli in Open-heart Surgery: a Randomized Clinical Trial

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 CO2 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 CO2 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 CO2 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 CO2 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 CO2 into the thoracic wound markedly decreases the incidence of microemboli.