Microdialytic monitoring during a cardiovascular operation

In an aorta-coronary bypass operation, the heart is excluded from the circulation for many minutes, leading to ischemia. During this time the heart is cooled in order to mitigate damage. Microdialysis has been shown to be very suitable for detecting ischaemic changes e.g. in brain. We therefore used this method to study the time courses of several neurochemical parameters which have been shown to indicate ischaemia in animal models (ascorbic acid, glutathione, cysteine, uric acid, glucose, lactate and pH), during such a bypass operation. Three patients were investigated, the microdialysis probe being inserted into the interventricular septum of the heart. Our results show that microdialysis is technically feasible in the human heart in a clinical setting, although the operation becomes more demanding for the surgeon. All the above-mentioned parameters could be detected in the heart muscle. Some of them showed changes characteristic of ischaemia, and the effects of cooling on the metabolism could also be noted. Long term measurements are planned to enable delayed damage to be disclosed.