Double-blind Study to Assess effectIveness of Pectoral Nerves Block After Breast Surgery on Piritramide Consumption

The aims of this study is to compare the effectiveness of pecs block associated to a general anesthesia in terms of Piritramide consumption compared with a general anaesthesia alone and the chronic pain incidence in patients that undergoing either a lumpectomy or a mastectomy associated with axillary dissection This is a double-blind, placebo controlled study that will randomise breast cancer subjects in 1:1 ratio to receive a \"pecs block\" of Ropivacaine 3.5 mg/ml and Clonidine 5 µg/ml (arm A) versus placebo (arm B).