Background and Aims The brachial plexus innervates the upper limbs through roots from the cervical and thoracic nerves. Due to its anatomical location with proximity to other important nervous and vascular structures, which directly implies the occurrence of post-block complications. The purpose of this article is to review news evidence about the main complications of the interscalene brachial plexus block.

Methods Case report with bibliographic review of PUBMED with the descriptors ‘interscalene block’, without time limitation.

Results JFS patient, 61 years old, undergoes surgery to repair left rotator cuff injuries under interscalene brachial plexus block (Ropivacaine 0,5% 25 ml e Clonidine 75mcg) and sedation. Needle-guided ultrasound block Stimuplex® A50 (BBraun). The patient remained clinically stable throughout the procedure and was partially sedated to the recovery room.

When alert, the patient evolves with difficulties to communicate. On clinical examination, the patient presented hemodynamically stable with dysphonia and left eyelid ptosis. Kept under observation and after 24 hours the reported symptoms were no longer present.

Conclusions Horner’s Syndrome (HS) is a set of signs and symptoms due to the blockade of the ipsilateral sympathetic pathway that innervates head, face and eye. Manifested with the triad of ptosis, miosis and anhidrosis. In the current literature, the development of HS after interscalene brachial plexus block is 4 – 37.5%, depending on the block technique, distribution, volume and dilution of the local anesthetic, in continuous infusion or after a single injection. Data showed that the use of ultrasound and neurostimulator to perform the block can reduce the rate of HS.