Diaphragmatic Paresis and Respiratory Failure After Interscalene Block in a Hypoxemic Trauma Patient: A Case Report.

Interscalene brachial plexus block (ISB) is frequently employed for analgesia in clavicle surgery but can cause ipsilateral diaphragmatic paresis, potentially leading to respiratory compromise in patients with limited pulmonary reserve. Trauma patients with pneumothorax may undergo regional anesthesia with spontaneous ventilation to avoid positive pressure ventilation (PPV), but this approach carries significant risk if respiratory function is already compromised. A woman in her 60s with multiple rib fractures, a small pneumothorax, and persistent hypoxemia underwent ISB for clavicle surgery. To avoid PPV, general anesthesia with spontaneous ventilation was performed using a laryngeal mask airway. Soon after induction, oxygenation worsened, and postoperative chest imaging revealed right diaphragmatic elevation consistent with phrenic nerve involvement. Emergent intubation and PPV were required. Further investigation identified a previously undiagnosed pulmonary embolism as a contributing factor to persistent hypoxemia. This case highlights the need for careful preoperative evaluation of respiratory reserve and thromboembolic risk when considering ISB in hypoxemic trauma patients. Strategies aimed at avoiding PPV may inadvertently increase the risk of respiratory decompensation in patients with limited respiratory capacity.