Analgesic Requirements for Post-operative Pain Control in Total Shoulder Replacement Patients: Comparison of Interscalene Single Shot Exparel (Bupivacaine Liposome) Injections to Cervical Paravertebral Catheter With Ropivacaine (0.2% Continuous Infusion)

Procedure Description:

The investigators commonly use these blocks for patients requiring total shoulder replacement: the patient is usually sedated with propofol. The patient is positioned in the lateral decubitus, or sitting position for this block. After the skin preparation and draping, the fingers of the non-operative hand separate the trapezius and levator scapulae muscle and a 25 gauge needle is used to anesthetize the skin and subcutaneous tissue.

The Trapezius and Levator Scapulae muscles are again separated with the non-operative hand and a 17 or 18 gauge insulated tuohy needle is inserted, which is attached to a nerve stimulator set at a current output of one to three milliamps, a frequency of two Hertz, and a pulse width of 200 to 300 microseconds. The needle is advanced towards the suprasternal notch until contact with the bony structures is made.

After contact with the bone the stylet of the needle is removed, the needle tip is walked off the bony structures in a lateral and slightly superior direction remaining on the plane of the line drawn from the dorsal spine of C6 to the suprasternal notch. After walking off of these bones structures the needle is advanced carefully in an anterior direction. As the needle is advanced there will be a motor response from the stimulator current. The muscles involved are usually the triceps, biceps, deltoids or major pectoral muscle but any muscle group of the upper limb would be acceptable for this block since the needle is now in contact with the posterior aspects of the roots of the brachial plexus. The tip of the needle at this point is situated between the anterior and middle scalene muscles and is in contact with the C6 root of the brachial plexus. At this point either a single-shot injection of Exparel will be performed, or a catheter for Ropivacaine will be inserted, as described below.

For catheter insertion: the nerve stimulator is removed from the needle and attached to the proximal end of the stimulating catheter and the tip of the catheter is inserted into the needle shaft. The nerve stimulator is usually set at a current output of one milliamp. The motor response should be unchanged. The catheter is advanced beyond the needle tip, if the motor response disappears, the catheter is careful drawn into the needle shaft and small adjustment to the needle, advancing slightly or withdrawing it slightly is done. This maneuver is repeated until the muscle twitch is unchanged during catheter advance. This indicates the catheter tip is now situated on the nerve root; the catheter is advanced 3 to 5 centimeter beyond the needle tip but not further than 5 centimeters. The needle is then removed without disturbing the catheter and the inner stylet of the catheter is also removed. The catheter position can be confirmed by attaching the nerve stimulator to the catheter, the motor response should be unchanged. The catheter is then subcutaneously tunneled and continuous infusion of Ropivacaine is inserted.