Left Recurrent Laryngeal Nerve Paralysis after Interpleural Analgesia

To the Editor:—

In patients with multiple rib fractures, interpleural analgesia has proved efficacious for improving the airway hygiene and reducing the need for ventilator support. 1Despite the ease and safety with the procedure, complications such as pneumothorax, 2pleural effusion, 3Horner syndrome, 4phrenic nerve paralysis, 5and unilateral bronchospasm 6are occasionally reported. We report a case with intermittent hoarseness due to recurrent laryngeal nerve block following each injection.

A 39-yr-old man sustained a left lung contusion and fracture of left ribs two through six after a motorcycle accident. Examination showed patient tachypneic with respiration rate of 30/min. The patient complained of severe pain on respiration, changing position, and breath holding. No paradoxical chest wall motion was observed. Radiologic findings showed, in addition to the fractures, mild parenchymal contusion and hemothorax of the left lung (fig. 1A).

Despite the use of intramuscular pethidine and external bandaging, the pain was so severe that the patient became dyspneic and hypoxemic (oxygen saturation measured by pulse oximetry: 82–85%). An interpleural block was performed. The patient was placed horizontally with the left side up. The point for injection was 5 cm medial to posterior midaxillary line, i.e. , 6 cm from the midline. The skin was infiltrated with lidocaine over the upper margin of the fifth rib. A 16-gauge Tuohy needle (Portex Ltd., Hythe, United Kingdom) with the bevel directed cephalad was introduced, and entry into the pleural space was identified by the “loss of resistance” technique. An epidural catheter was advanced 15 cm into the interpleural space. On aspiration, about 3 ml of bloody fluid was aspirated. We then withdrew the catheter 3 cm until no more blood was aspirated. A test dose of 1:200000 epinephrine in 3 ml of normal saline was given via  the catheter. Because no tachycardiac response was noted within 5 min, a bolus dose of 20 ml 0.5% bupivacaine with 1:200000 epinephrine was injected. The patient remained in a left lateral decubitus position for 20 min after the injection and reported pain relief 15 min later. Peak analgesic activity was noted 45 min after the injection. A unilateral zone of analgesia to pinprick extended from the T²to T¹²dermatomal level. There was no significant change in blood pressure or heart rate.

The pain returned 6 h later, and the second dose of 20 ml 0.5% bupivacaine was given. The analgesic effect was achieved within 15 min and persisted for 12 h. However, hoarseness and mild dysphagia were noted beginning 15 min after the second injection; these symptoms disappeared 6 h later. The same response developed after a third injection of bupivacaine 12 h after the episode of hoarseness. Despite the two episodes of hoarseness, the vital signs remained stable and satisfactory analgesia was obtained.

We consulted an otolaryngologist after the second insult. Direct laryngoscopy revealed a complete paralysis of paramedian portion of the left vocal cord. Following 5 ml Angiografin (meglumine diatrizoate) injected through the catheter, a chest radiograph in the standing position showed a patchy accumulation of contrast medium in the T⁶paravertebral area and along the aortic arch at T⁴level (fig. 1B). Because the analgesic effect was satisfactory, we withdrew the catheter for 5 cm under the fluoroscopy to avoid further blockade of the left recurrent laryngeal nerve. Bupivacaine was resumed on demand. There was no hoarseness after the subsequent injections of bupivacaine. Analgesia remained satisfactory for the following 3 days. The patient was discharged 5 days later.

Left recurrent laryngeal nerve arises from vagus nerve and courses around the aortic arch near the ligamentum arteriosum. Then, it runs in the groove between the trachea and esophagus and proceeds superiorly to innervate the intrinsic muscles of the larynx. 7In close contact with various anatomic structures at the T⁴level, the nerve is extremely vulnerable to pathologic conditions associated with these organs, e.g. , dissecting aneurysm of the ascending aorta, and Pan coast tumor of the left lung. On the other hand, the right recurrent laryngeal nerve courses around the right subclavian artery that never enters the thoracic cavity.

In our case, contrast medium was accumulated near the sixth thoracic vertebral body and along the aortic arch in the standing position. Because contrast medium injected via  the interpleural catheter has been shown to diffusely distribute along the mediastinum, 8,9local accumulation of dye should not be visualized when 5 ml contrast medium is injected into the interpleural space. Accordingly, our catheter could be located in the subpleural space of the upper mediastinum and resulted in block of the adjacent left recurrent laryngeal nerve. It is possible that repeated injection and body movement may in part lead to migration of the catheter into the upper mediastinum.

Misplacement of the catheter either into the extrapleural space or into lung tissue has been previously reported. 10Identifying the pleural space by the “loss of resistance” technique is associated with catheter displacement more frequently than by the traditional “detection of negative pressure” technique. In our case, the swollen lateral chest wall and fractured ribs were extremely tender to touch. A more medial approach, i.e. , 6 cm from the midline, was thus used to avoid inserting needle directly over the hematoma and the underlying fracture ribs. Therefore, the syringe had to be attached horizontally, and its entry into the interpleural space was identified by loss of resistance.

In summary, we demonstrated an intermittent blockade to the left recurrent laryngeal nerve following the inadvertent injection of 20 ml 0.5% bupivacaine into the left upper mediastinum. A sudden onset of hoarseness following the bolus injection and the local accumulation of contrast medium suggest a misplaced catheter in the subpleural space. Because subpleural block per se  provides effective analgesia as well, the therapeutic benefit from replacing the catheter is outweighed by the potential risks with further procedures. In such situations, we recommend that the catheter be withdrawn immediately a few centimeters and replaced only if this intervention is insufficient.