Liver damage as a consequnce of ischemia (I) and reperfusion (R) is known to harm the liver and could hence be a critical factor of the postoperative outcome of patients undergoing liver surgery. In order to protect the liver from ischemic damage following interventions such as the Pringle Maneuver, preconditioning has been successfully applied in various animal models as well as in humans. Since ischemia inevitably leads to cell hypoxia and subsequnet release of endogenuous metabolites, the investigators hypothesize that instead of brief periods of ischemia, the exogenuous infusion of purine analogues may also protect against subsequent prolonged periods of ischemia. Moreover, after reperfusion, the antiinflamamtory action of purine ananlogue infusion can further attenuated liver damage.

Inclusion Criteria:

• elective resection of liver tumors
• age 18 to 80 years
• informed consent

Exclusion Criteria:

• chronic obstructive pulmonary disease
• heart insufficiency NYHA III-IV
• atrio-ventricular conductance blockage II. (Mobitz) or III. degree
• atrial fibrillation
• coronary heart disease (CCS III. or IV. degree)
• arterial hypertension
• acute renal failure
• increased intracranial pressure
• gout
• pregnancy