Tension Pneumothorax After Ultrasound-Guided Interscalene Block and Shoulder Arthroscopy

Discussion

Interscalene brachial plexus anesthesia was first described by Winnie⁴ in 1970. This block targets the trunks of the brachial plexus, which are enclosed in a fascial sheath between the anterior and middle scalene muscles. In this region lie several structures at risk: the phrenic nerve superficially and inferiorly; the carotid sheath located superficially and medially; the subclavian artery parallel to the trunks; and the cupula of the lung that lies deep and inferior to the anterior scalene muscle. Recognized complications of the block include vocal hoarseness, Horner syndrome, and hemidiaphragmatic paresis caused by the temporary blockade of the ipsilateral recurrent laryngeal nerve, stellate ganglion, and phrenic nerve, in that order.⁵ Use of the interscalene block has been associated with minimal risk for pneumothorax, because the needle entry point is superior and directed away from the lung pleura.⁶ This is in contrast to the more inferiorly placed supraclavicular block, located in closer proximity to the lung cupula.⁵

Two different approaches are commonly used during ultrasound-guided nerve blocks. The in-plane approach generates a long-axis view of the needle by advancing the needle parallel with the long axis of the ultrasound probe. While this allows direct visualization of the needle tip, it requires deeper needle insertion from lateral to medial, causing puncture of the middle scalene muscle that may increase patient discomfort and risk nerve injury within the muscle.⁷ The out-of-plane approach used on our patient involves needle insertion parallel to the brachial plexus, but along the short axis of the ultrasound probe. Although this permits the operator to assess the periphery of the nerve, it may lead to poor needle-tip visualization during the procedure. As a result, operators often use a combination of tissue disturbance and “hydrolocation,” in which fluid is injected to indicate the needle-tip location.^8,9

Tension pneumothorax represents the accumulation of air in the pleural space that leads to impaired pulmonary and cardiac function. It is often caused by disruption or puncture of the parietal or visceral pleura, creating a connection between the alveoli and pleural cavity. The gradual buildup of air in the pleural cavity results in increased intrapleural pressure, which compresses and ultimately collapses the ipsilateral lung. Venous compression restricts blood return to the heart and reduces cardiac output. Clinical manifestations include dyspnea, hypoxemia, tachycardia, and hypotension.¹⁰ Multiple techniques were developed to better localize the brachial plexus while reducing injury to nearby structures, including the lung. These include eliciting needle paresthesias, electrical nerve stimulation, and ultrasound guidance. While nerve stimulation was once the gold standard for brachial plexus localization, ultrasound guidance has gained in popularity because of its noninvasive nature and dynamic capability to identify nerves and surrounding structures.¹¹ Perlas and colleagues¹² determined the sensitivity of needle paresthesias and nerve stimulation to be 38% and 75%, respectively, in cases in which plexus localization had been confirmed by ultrasound.

Several studies have reported on the efficacy of interscalene nerve block with either nerve stimulation or ultrasound guidance in the setting of shoulder surgery.^2,3 Bishop and colleagues³ reviewed 547 patients who underwent interscalene regional anesthesia with nerve stimulation for both arthroscopic and open-shoulder procedures. They reported a 97% success rate and 12 (2.3%) minor complications, including sensory neuropathy and complex regional pain syndrome. There were no cases of pneumothorax, cardiac events, or other major complications.³ In a prospective study of 1319 patients, Singh and colleagues² reported a 99.6% success rate using ultrasound-guided interscalene blocks for their shoulder surgeries. A total of 38 adverse events (2.88%) were identified: 14 transient neurologic events, including ear numbness, digital numbness, and brachial plexitis; 1 case of intraoperative bradycardia, and 2 cancellations after the block for chest pain and flank pain, which yielded negative cardiac workups. Other complications included postoperative emergency room visits and hospital admissions for reasons unrelated to the block.² Interscalene regional anesthesia, therefore, provides effective anesthesia for shoulder surgery with low complication rates.

Pneumothorax after ultrasound-guided interscalene block has rarely been reported.^13,14 In a review of 144 ultrasound-guided indwelling interscalene catheter placements, a 98% successful block rate with a single complication of small pneumothorax after total shoulder arthroplasty was reported.¹³ Mandim and colleagues¹⁴ reported a case of pneumothorax in a smoker who underwent an ultrasound-guided brachial plexus block prior to open reduction and internal fixation of an ulnar fracture. While the patient was asymptomatic and vital signs remained stable during the procedure, the patient complained postoperatively of chest pain with hypoxia, tachycardia, and hypotension. A chest radiograph confirmed an ipsilateral pneumothorax, and the patient was treated successfully with chest-tube placement. The authors attributed this complication to a higher pleural dome resulting from a hyperinflated lung caused by chronic smoking. Our patient reported no history of smoking and her preoperative chest radiograph had no evidence of lung disease.