The interscalene block provides effective analgesia after shoulder surgery. It consists of injecting local anaesthetic within the brachial plexus, in the interscalene groove, between the anterior and middle scalene muscles. Unfortunately, this technique is associated with respiratory complications such as hemidiaphragmatic paresis due to the spread of the local anaesthetic towards the phrenic nerve that lies close to the brachial plexus, with an incidence up to 100%. The diaphragmatic paresis may be a serious side-effect, especially in patients suffering from a reduced respiratory function such as chronic obstructive pulmonary disease; this entity may even represent a contraindication to the performance of the block.

The shoulder is mainly innervated by the suprascapular and axillary nerves, both of them coming from C5 and C6 branches of the brachial plexus block. Recently, several authors have successfully identified and block these two nerves under ultrasound guidance. Only one randomised controlled trial compared interscalene block with a combination of suprascapular and axillary nerve blocks, and showed inconclusive results probably due to the absence of ultrasound guidance; indeed, analgesia was equivalent at the sixth postoperative hour, while patients with an interscalene block had reduced pain scores in the recovery room. Besides, the authors did not investigate the impact on the respiratory function.

In that randomised controlled trial, the investigators would like to compare the analgesic efficacy and the respiratory outcomes between the interscalene block and the combined suprascapular-axillary nerve blocks.

Inclusion Criteria:

• ASA physical status I-III;
• 18-85 years of age, inclusive;
• surgery less than 3 hours.

Exclusion Criteria:

• indication for catheter insertion;
• contraindications to brachial plexus block (e.g., allergy to local anaesthetics, malignancy or infection in the area);
• existing neurological deficit in the area to be blocked;
• pregnancy;
• history of neck surgery or radiotherapy;
• severe respiratory disease;
• chest deformity;
• inability to understand the informed consent and demands of the study;
• patient refusal.