The aim of the study is to compare programmed intermittent bolus application and continuous epidural infusion with regard to additionally applied patient-controlled volume of local anesthesia and quality of analgesia.

Usually, patient controlled epidural analgesia (PCEA) is performed with a constant background infusion and patient-controlled bolus applications. An alternative approach is to give boluses at a regular rate for basic medication, instead of the continuous background infusion, maintaining the same amount of medication delivered per hour, (Programmed Intermittent Epidural Bolus injection; PIEB). In both cases, the patient has the option to trigger additional boluses. PIEB has been applied successfully in pain relief for lumbar epidural anesthesia in obstetrics, with better quality of analgesia and less total volume of local anesthetic required. It is assumed that the higher pressure in the epidural space with bolus injection results in a better and more uniform spread of the local anesthetic. In this study the PIEB-mode will be applied in major gynecological and abdominal surgery. In order to address the possibility that the different types of surgery result in different degrees of postoperative pain, the patients are stratified in three groups and randomized within these groups (Wertheim, Whipple, major colon surgery).

Inclusion Criteria:

• Abdominal tumors in gynecology and general surgery
• Enlightenment and written consent to the investigation

Exclusion Criteria:

• refusal to participate
• pregnancy and breast feeding period
• general contraindications for thoracic epidural anesthesia (e.g. coagulation disorders, --anticoagulation according to the guidelines of DGAI)
• Impossibility to place the epidural catheter correctly
• Known allergy to the drugs used in the study
• Lack of understanding how to use the patient-controlled system
• postoperative follow-up respiratory assistance