Influence of the Insertion Distance on Loss of Sensation Produced by Interscalene Perineural Catheters in the Context of Shoulder Surgery.

Pain following shoulder surgery is reported as severe for 70% of patients, and is a major concern in both hospitalised and ambulatory surgery patients. Pain control is particularly important, as adequate analgesia allows rapid mobilisation of the operated shoulder and prevents complications related to immobility. Several methods have been proposed to treat this pain, the most promising being the interscalene nerve block. The injection of local anesthetics reduces sensation from the shoulder and provides better pain relief after surgery than narcotic medication. To prolong the duration of the analgesia, a catheter must be positioned next to the brachial plexus. Through this catheter, small quantities of local anesthetics can be continuously delivered for several hours after surgery, effectively relieving the worst of the pain.

To date, the continuous interscalene nerve block has been shown to improve pain relief, to reduce nausea, vomiting, pruritus and sleep disturbances after shoulder surgery. It also reduces the need for opioids.

Until recently, catheter techniques were not frequently used due to technical difficulties encountered with catheter installation and catheter displacement after surgery. Due to recent improvements in nerve and catheter localisation, catheter installation has become easier, more precise and more reliable. However, the distance at which the catheter must be advanced next to the brachial plexus in order to provide the best pain relief remains unknown. Insertion distance could influence the initial quality and distribution of the freezing, its duration, or both. Therefore, this study is designed to compare two catheter insertion distances, in order to help determine which is best for pain relief after shoulder surgery.

Methods :

1. Insertion of the catheter :