Fig. 1

Study enrolment. A large number of consecutive patients for shoulder sugery was screened and in a second step the same surgical procedure with the same surgeon selected. The subjects should be without pre-existent immune deficiencies and comorbidities such as diabetes, bowel diseases, and ASA 1 to 2. Planned anesthesia also should be homogenously; we planned a combination of regional anesthesia (interscalene plexus block for pain control), low dose opioid induction and propofol, no muscle relaxant, and anesthesia maintenance with sevoflurance for anesthesia depth at the target level deep or superficial