ED90 of Bupivacaine After Lidocaine Test Dose with DPE and EPL

The investigators will be conducting a randomized controlled trial with patients randomized into either an EPL or a DPE group. For the first subject in the DPE and EPL techniques, the initial dose of bupivacaine 25 mg will be used, with an endpoint being the achievement of an NRS \< 3 at 30 min. Subsequent patients are administered bupivacaine doses determined by the response of the previous subject, as per the biased coin method. The subsequent up and down interval doses are bupivacaine 2.5 mg (1 mL) increments. Hence, if the first subject does not respond successfully, the dose for the second subject will be bupivacaine 27.5 mg. If the second subject does not respond successfully, the dose for the third subject will be bupivacaine 30 mg. By contrast, if a subject responds successfully, the bupivacaine dose will be decreased to 22.5 mg with a probability of 10% and maintained with a probability of 90% (ratio 1:9).