Postoperative pain management plays an important role in elective shoulder surgery. The aim of this randomized quantitative study is to compare two frequently used postoperative pain regimes (hydromorphone versus piritramide) regarding onset and duration after the effectiveness of the single-shot interscalene block has diminished.

Inclusion Criteria:

• all patients undergoing elective shoulder surgery with a single-shot interscalene plexus brachialis block in addition to general anesthesia
• patients aged 18-99 years
• patients being capable of giving an informed consent to participation in this study

Exclusion Criteria:

• patients aged below 18 years
• patients with decompensated liver, heart or renal insufficiency
• patients with any kind of lung disease
• patients with a chronic pain syndrome
• patients with a previous pain medication with more than 3 drugs over more than 3 months