Interpleural Migration of an Interscalene Catheter

To the Editor: Continuous interscalene brachial plexus block (ISB) through a catheter is widely used to provide an optimal postoperative analgesia after major shoulder surgery (1). Improperly placed catheters like epidural, intrathecal, intravascular, or subcutaneous can lead to serious complications such as acute respiratory distress, total spinal block, epidural block, heart failure, or seizures and finally miss its initial purpose, an efficient analgesia (2–5). We present an unusual and potentially dangerous complication of an ISB catheter: an interpleural migration. A 50-yr-old ASA physical status I woman (height, 155 cm; weight, 60 kg) was scheduled for an arthroscopic rotator cuff repair with a subacromial decompression of her left shoulder under an ISB and a mild sedation. The latter was performed following Winnie’s landmarks with the aid of a 50-mm insulated needle and a nerve stimulator (set up to deliver a current of 2 mA, with a frequency of 2 Hz and an impulse duration of 0.1 ms). The brachial plexus (upper trunk) was located by obtaining an elbow flexion with a threshold of 0.3 mA. After injection of 30 mL of ropivacaine 0.75% through the needle, a catheter was introduced through that needle with a caudally oriented needle bevel and advanced 8 cm distally from the needle tip. During the operation the patient was sedated with a target-controlled propofol infusion (0.8 μg · mL−1). After an uneventful intervention, the patient was brought into the recovery room, where no abnormalities were observed, notably any pulmonary symptoms. It is a standard procedure in our institution to control the position of some catheters in the recovery room by one anteroposterior radiograph of the shoulder-neck region. This is done radiographically by injecting 5 mL of a contrast medium (Iopamiron 300®) before starting the continuous injection of local anesthetics via an elastomeric infusion pump for adequate long-lasting postoperative pain relief. On these radiographs, the perfusion area of the catheter can well be visualized throughout the contrast medium but not so for the needle placement, as variations in the making of the images (e.g., patient position, plate placement) do not allow a precise localization. The control radiograph of our patient showed an opacification of the upper part of the left pleura, assuming that the catheter lay in the interpleural space (between parietal and visceral pleurae), without signs of proper perfusion of the interscalene region or a pneumothorax (Fig. 1). After drawing the catheter back 5 cm, another control radiograph was obtained that showed a proper opacification of the interscalene region (Fig. 2). The patient showed no signs of respiratory distress or other symptoms that could have been related to the firstly malpositioned catheter. On the basis of the stable clinical status and the radiograph evidenced right position of the catheter, we decided to keep the latter in situ. The following 48 hours passed uneventfully, and adequate pain relief could be obtained by continuous infusion of ropivacaine 0.2%.Figure 1: Interpleural location of the interscalene catheter (black arrow).Figure 2: Adequate interscalene location of the catheter (white arrow) and residual interpleural opacification (black arrow).The injection of an initial bolus of a long-lasting anesthetic provides adequate anesthesia during the surgery and an efficient pain relief during the next 12 h and is performed systematically in our institution. The dosage of local anesthesia in this case may appear to be elevated in a patient with this body morphology but corresponds to a recommended modus operandi (40 mL of ropivacaine 0.6% for patients weighting less than 60 kg) (1). Before this case, we had no standard practice concerning the depth of catheter insertion. Generally, it was more than 5 cm from the needle tip to prevent accidental catheter desinsertion. After this incident, an average distance of about 3 cm is used from the needle tip and always shows appropriate positioning on the postoperative control radiographies. Nevertheless, special care must be taken when inserting the ISB catheter in small or short-necked individuals, such as our patient. If an interscalene catheter is inserted too deeply, although unusual, it could go into the interpleural space and create major complications as described for interpleural catheters that have been placed intentionally for regional anesthesia of the chest wall (6). Reported complications of interpleural analgesia for different indications such as breast, renal, gall bladder and thoracic surgery, include pneumothorax, systemic toxicity, pleural effusion, Horner’s syndrome, pleural infection, and of course inadequate analgesia of the intentionally aimed region (7). The method of systematic catheter opacification is an unusual procedure and is surely not beyond controversy. We justify our proceeding with the knowledge that intrathecal or epidural migration of catheters has been reported for catheterization of the interscalene or psoas compartments (3,5,8). We therefore prefer to opacify all catheters placed near the spine. Another reason for radiographic control of ISB catheters is that shoulder surgery such as rotator cuff repairs can be very painful in the postoperative period, and an appropriate early alternative, such as an IV morphine PCA, can be used when a malpositioned catheter is existent and cannot be placed properly. Vincent Souron, MD Youri Reiland, MD Antoine De Traverse, MD Laurent Delaunay, MD Laurent Lafosse, MD