Background: The use of local anesthetics as a supplement to conventional techniques in breast surgery is widely reported in the literature. Currently there is controversy regarding the efficacy of surgery for breast infusion of local anesthetic after surgery. The aim of this study demonstrate the efficacy of administering a local anesthetic into the surgical bed of women operated radical mastectomy for breast cancer for the control of postoperative pain.

Material and methods: double-blind randomized clinical trial. The investigators recruited patients who underwent modified radical mastectomy that met inclusion and exclusion criteria. The intervention group were infused with L-bupivacaine 0.50% 2 ml/h for 48 hours, and saline control group at 2 ml/h during surgery and anesthetic technique 48 hours. Local anesthetic and rescue medication was identical in both groups.

Statistical analysis: The baseline patient characteristics of the patients were analyzed by Chi square or Student t always meet criteria of normality, otherwise it will use the Mann-Whitney. To determine the effectiveness of treatment as well as pain scale adverse events will be held on chi-square test.

Inclusion Criteria:

• Patients diagnosed with operable breast cancer, which will be submitted to modified radical mastectomy
• Sign informed consent.

Exclusion Criteria:

1. Mastectomy without lymphadenectomy
2. Over 80 years
3. Cognitive impairment and patients with serious psychiatric disorders before diagnosis of the cancer process
4. Severe liver or kidney disease
5. Patients allergic or intolerant to any of the drugs used in the study protocol.
6. Regular users of analgesics or narcotics