Summary
Bubble activity was recorded simultaneously with ultrasonic probes over the arterial line of the pump oxygenator and the carotid artery of 30 patients undergoing either valve replacement (20) or aortocoronary vein bypass procedures (10). The results were analysed semiquantitatively. in selected cases bubbles were visualized in the chambers of the heart by 2-D echocardiography. Bubbles were found regularly during the Initiation of bypass despite the use of arterial line filters, while during perfusion on total bypass bubble activity was significantly reduced by the use of a filter in both the arterial line and the carotid artery. During reperfusion with the aortic cross-clamp removed there is only a slight increase of bubble activity in the arterial line, due to rewarming of the perfusate, but a considerable increase in the carotid artery, due to ejection of microbubbles from the cavities of the heart into the systemic circulation. This bubble-activity considerably exceeds the time on bypass in valve patients. The significance of the microbubbles from the cavities of the heart was studied in an expertmental model, allowing differentiation of the influences of thoracotomy, thoracotomy plus routine CPB, and bypass plus cardiotomy with various de-airing procedures. While cerebrospinal fluid enzymes indicating cerebral injury remained normal during routine CPB, there was a significant increase of these after cardiotomy. Carbon dioxide purge of the heart before de-airing significantly reduced the rise in spinal fluid enzymes.
Key words
Open heart surgery - Neurological damage - Gas emboli - Spinal fluid enzymes
