Comparison of the Catheter-over-needle and Catheter-through-needle Methods for Continuous Delivery of Local Anesthetic During Peripheral Nerve Blockade

When anesthesiologists perform a regional nerve block, they will often put a catheter - a flexible plastic tube - in the patient to allow for continuous delivery of local anesthetic. This allows the nerve(s) to be 'frozen' so that the patient is more comfortable during and after surgery. The most common method of placing the catheter close to a nerve involves threading the catheter through a needle which has been inserted under the skin. Because the catheter is very thin and flexible, it does not thread well through tissue and will buckle and kink when enough force is applied to it. Another problem is that the puncture hole left by the needle is larger than the diameter of the catheter, meaning that when the needle is withdrawn, the catheter is not secure, which increases the chance that it will dislodge and cause leakage of local anesthetic. One solution to these problems is to use a catheter placement method similar to how intravenous catheters are installed. In this method, the catheter fits around ('over') the needle, which results in more support for the catheter while it is being pushed under the skin. We wish to examine if a catheter-over-needle method would be useful for placing a catheter to deliver local anesthetic during peripheral nerve blockade. We will compare the catheter-over-needle method to the currently used catheter-through-needle method on patients who require continuous anesthetic delivery for their surgery; half the patients will receive anesthetic through one method, and the other half will receive anesthetic through the other method. We believe that using the catheter-over-needle method will result in more secure placement of the catheter and more efficient delivery of local anesthetic.