Optimizing the Use of Ketamine to Reduce Chronic Postsurgical Pain

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) equal to or greater than 41
* 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