[Gas embolisms during operations on the open heart]

During routine open heart procedure the amount of microbubbles released from the oxygenator and the heart into the arterial circulation were measured by ultrasonic probes, placed over the arterial line and the carotid artery. The significance of microbubbles ejected from the cavities of the heart for cerebral cell injury were studied in an experimental model, analyzing enzyme levels in cerebrospinal fluid. A typical phasic bubble-activity was found in both the arterial line and the carotid artery, with an initial high during the initiation of bypass, a lower plateau during perfusion and a slight increase again with rewarming during reperfusion after releasing the aortic cross clamp. The increase of bubble activity during reperfusion was more pronounced in the carotid artery as bubbles released from the heart were added to those coming from the heart lung machine. After leftsided cardiotomy this activity lasted for up to 20 min after termination of extracorporeal circulation (ECC). The use of filters reduced the bubble activity during perfusion significantly, but did not change the activity during reperfusion and after termination of ECC. Liquor enzyme levels were found normal during and after bubbles reperfusion, but rose significantly after leftsided cardiotomy. CO2 wash-out reduced the increase in liquor enzyme levels markedly.