interim analysis proved that protocol intervention had no preventive effect

Interscalene brachial plexus block (ISB) constitutes the analgesic criterion standard for shoulder surgery. However, it is associated with a high incidence of hemidiaphragmatic paralysis (HDP) that may not be tolerated by patients with chronic pulmonary disease. Continuous ISBs have not avoided this complication with the reported and regularly used local anesthetic dilutions (i.e. 0.125% bupivacaine, 0.25% ropivacaine, etc). This observational study will register the incidence of HDP in continuous interscalene block (CISB) using a very diluted solution of levobupivacaine (0.04%) in patients undergoing arthroscopic shoulder surgery.

The main objective of this study is to determine the frequency of HDP the first postoperative day before patient discharge(POD).

Inclusion Criteria:

• age between 18 and 80 years
• American Society of Anesthesiologists classification 1-3
• body mass index between 20 and 35

Exclusion Criteria:

• adults who are unable to give their own consent
• pre-existing neuropathy (assessed by history and physical examination)
• coagulopathy (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. platelets ≤ 100, International Normalized Ratio ≥ 1.4 or prothrombin time ≥ 50)
• renal failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. creatinine ≥ 100)
• hepatic failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. transaminases ≥ 100)
• allergy to local anesthetics (LAs)
• pregnancy
• prior surgery in the ipsilateral neck region
• chronic pain conditions

patients undergoing arthroscopic shoulder surgery and programmed to receive a continuous interscalene block as part of postoperative analgesia