Inclusion Criteria:  Woman 18 years of age or older Undergoing elective breast surgery for oncologic indication as follows: unilateral or bilateral mastectomy, prophylacticmastectomy, +/- lymph node dissection, +/- immediate or delayed reconstruction. No distant metastases  Exclusion Criteria:  History of cognitive impairment or clinical signs of altered mental status (AMS) that may interfere with adherence to study procedures and/or participant safety. Clinical signs of AMS may include but are not limited to: confusion, amnesia, disorientation, fluctuating levels of alertness, etc. Past ketamine or phencyclidine misuse or abuse Schizophrenia or history of psychosis History of post-traumatic stress disorder Known sensitivity or allergy to ketamine Liver or renal insufficiency History of uncontrolled hypertension, chest pain, cardiac arrhythmia, stroke, head trauma, intracranial mass or hemorrhage, glaucoma, porphyria, uncontrolled thyroid disease, or other contraindication to ketamine Lamotrigine, alfentanil, physostigmine, or 4-aminopyridine use Currently Pregnant Body mass index (BMI) greater than 35 Non-English or non-Spanish speaker Currently participating in another pain interventional trial Unwilling to comply with all study procedures and be available for the duration of the study Patient is American Society of Anesthesiologists (ASA) physical status 4, 5, or 6 Patient has started or undergone hormone therapy for gender transition into male. Patient scheduled for any bilateral (or greater) flap reconstruction