Intraoperative monitoring of the potassium-activity and pH- value on the myocardial surface during coronary bypass surgery.

Introduction: Ischemic periods very often occur a dysfunction of the heart. In this series the intraoperative changes of potassium-activity and pH- value on the heart undergoing cardioplegic induced cardiac arrest were studied. Furthermore, the sensitivity of the system in diagnostic fields of ischemic periods and reperfusion damages were investigated.

Methods: In eight patients (7 male and 1 female pts.) undergoing elective cardiosurgical procedures (aortocoronary bypass grafts) the ion activity of potassium and hydrogen ions were monitored on the heart, intraoperatively. By ion-selective electrodes the superficial cardiac ion activities were evaluated on definitive time periods on the left (LV) and right ventricle (RV).

Results: Preliminary results suggest: In the reperfusion-period different pH-values result on the ventricles. In the end of reperfusion the pH-values return to the starting points. Though the evaluated parameters are too alcaline in comparison to physiological intervals. The time course of epicardial potassium-concentrations is not different between the RV and LV. Initially, only low concentrations were found during perfusion and reperfusion, in the last interval of reperfusion period an increase of potassium on both ventricles were evaluated. In the end of the operations the superficial ion concentrations approximate to the values evaluated at the starting points.

Conclusion: These results suggests, that the dynamics of ion-exchange-processes in the myocardium can be monitored with the help of ion-selective probes. This new technique opens new strategies in the qualitative check-up of myocardial protective procedures during cardioplegic cardiac arrest.