Mixed Local for Sciatic Block

Choice of local anesthetics is the major determinant of the characteristics of a peripheral nerve block. Short acting local anesthetics while provides faster onset suffer from shorter duration. On the other hand, long acting local anesthetics while provides long duration suffered from long onset time. The ideal local anesthetics should provide faster nerve block onset while providing reasonable duration to provide sustained postoperative analgesia. Mixing short and long acting local anesthetics for nerve blocks may appear to be the solution however previous published studies have demonstrated similar onset time to long acting local anesthetics and with reduced duration. Recently, the London Health Sciences Centre established an ambulatory surgical centre. Fast onset peripheral nerve block is desirable. Previous studies have not looked at popliteal sciatic block and anecdotally we feel addition of short acting local anesthetics appear to speed up onset. We are therefore interested in conducting a randomize trial to determine whether mixing short and long acting local anesthetics can speed up onset of surgical quality block.