Paravertebral Versus Pectoralis Block for Post Mastectomy Pain

Inclusion Criteria: * The clinical decision has been made that the patient will have a bilateral mastectomy with tissue expander placement * The participant is ≥ 18 years and ≤ 80 years * Weight ≥ 60 kg and ≤ 90 kg * The participant's primary anesthesia care team has planned for general anesthesia * The participant agrees to receive a regional block * American Society of Anesthesiologists class 1-3 Exclusion Criteria: * 18 years of age or \>80 years of age * \< 60 kg or \> 90 kg * Non-English speaking * Known or believed to be pregnant * Participant is a prisoner * Participant has impaired decision-making capacity per discretion of the Investigator * Standard contraindications to regional blocks (coagulopathy including abnormal INR after discontinuation of warfarin, baseline INR (international normalized ratio) \>1.5, platelets \<100,000, elevated PTT (prothrombin time), failure to discontinue anticoagulant medication, or infection at site) * Significant renal, cardiac or hepatic disease per discretion of the investigator * A clinical decision made that indicates need for a partial or complete axillary node dissection * American Society of Anesthesiologists class 4-5 * Known hypersensitivity and/or allergies to local anesthetics * Chronic Opioid Use (daily or almost daily use of opioids for \> 3 months) * Participant refusal