Acute glenohumeral dislocation is a common emergency department (ED) presentation, however, pain control to facilitate reduction in these patients can be challenging. Although both procedural sedation and peripheral nerve blocks can provide effective analgesia, both also carry risks. Specifically, the interscalene brachial plexus block carries risk of ipsilateral hemidiaphragmatic paralysis due to inadvertent phrenic nerve involvement. There are techniques, however, that the emergency clinician can utilize to reduce these risks and optimize the interscalene brachial plexus block for specific pathologies such as glenohumeral dislocation.
We report three cases of patients who presented to the ED with acute anterior glenohumeral dislocation. Two of the patients had a history of pulmonary disease. In all three cases, targeted low-volume interscalene nerve blocks were performed and combined with systemic analgesia to facilitate successful closed glenohumeral reduction and reduce the risk of diaphragm paralysis. All 3 patients were monitored after the procedure and discharged from the ED. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Contrary to anesthesiologists who often seek to obtain dense surgical blocks, the goal of the emergency clinician should be to tailor blocks for specific procedures, patients, and pathologies. The emergency clinician can optimize the interscalene brachial plexus block for glenohumeral dislocation by using a low volume (5-10 mL) of anesthetic targeted to specific nerve roots (C5 and C6) to provide effective analgesia and reduce the risk diaphragm involvement.

Interscalene brachial plexus blockade is regularly used for postoperative pain management following shoulder surgery. A known but generally benign side effect of this technique is Horner syndrome. Another syndrome known as harlequin syndrome exists but does not appear to be as common. This syndrome consists of contralateral facial flushing and sweating secondary to ipsilateral sympathetic chain inhibition. Despite the alarming presentation in the perioperative setting, this syndrome appears to be benign and self-limiting when precipitated by regional anesthetic technique. This article describes an occurrence of harlequin syndrome without observed ptosis or miosis following a postoperative interscalene nerve block.