Sevoflurane and Isoflurane - During Cardiopulmonary Bypass With the MECC System (Minimized Extracorporeal Circuit)

The use of volatile anesthetics in cardiac anesthesia is very common, because of their cardioprotective effects and their ability to ensure a sufficient depth of anesthesia. In line with the development of fast track concepts in cardiac anesthesia, volatile anesthetics are widely used to avoid a delayed recovery from cardiac surgery and anesthesia. Volatile anesthetics are delivered from calibrated vaporizers in the anesthesia machine or the cardiopulmonary bypass machine (during extracorporeal circulation). Isoflurane and Sevoflurane are the most commonly used volatile anesthetics in patients undergoing cardiopulmonary bypass (CPB). The vaporizer of the anesthetics is on the cardiopulmonary bypass machine and the volatile agent is blended with air and oxygen. Until now, the pharmacokinetics of halothane, enflurane, isoflurane and desflurane during CPB have been described. Sevoflurane might be of advantage because of additional myocardial protective effects during cardiac anesthesia and cardiopulmonary bypass. However, the pharmacokinetics of sevoflurane during CPB have not been investigated so far, although its being used at many hospitals. The investigators will conduct a randomized prospective study with either sevoflurane or isoflurane during cardiopulmonary bypass surgery. The study will help to answer the questions about the possible cardioprotective effects of the widely used volatile anesthetics and the hemodynamic stability during cardiopulmonary bypass. Knowing the pharmacokinetics of these drugs allows the anesthesiologist to titrate the volatile anesthetics more precise. The investigators hypothesizes that the maximal postoperative increase in troponin T will be smaller in the sevoflurane group than in the isoflurane group. The investigators hypothesizes that the total amount of noradrenaline needed during the entire period of cardiopulmonary bypass will be smaller in the sevoflurane group than in the isoflurane group. The investigators hypothesizes