Prospective randomized double blinded, placebo controlled study that will evaluate the effect of intra-operative ketamine administration on post-operative analgesic requirements and self-reported pain in patients undergoing total hip and total knee arthroplasty who demonstrate high levels of pain catastrophizing.

Pain management can be one of the most challenging aspects of care for total joint arthroplasty patients. Poor post-operative pain control can lead to poor patient satisfaction and functional outcomes. Moreover, prolonged post-operative opioid utilization for post-operative pain is associated with substantial adverse sequelae. Identifying patients at high risk for poor post-operative pain control, and implementing strategies to improve pain management in this population is of utmost importance. One patient feature that has been shown to reliably predict poor post-operative pain management is pain catastrophizing. Currently available self-reported metrics such as the pain catastrophizing scale allow for pre-operative identification of patients who exhibit high levels of pain catastrophizing. Furthermore, there currently exist strategies which may effectively improve post-operative pain management in this population. One such strategy is "pre-emptive" analgesia utilizing ketamine administered at the time of surgery. Ketamine is commonly utilized in the treatment of both acute and chronic pain, and is believed to reduce pain intensity through a complex mechanism involving opioid receptors and excitatory neurotransmitters. It has been utilized in a variety of surgical procedures and has consistently been shown to reduce acute post-operative pain and analgesic consumption as long as 6 months after surgery, without a significant incidence of medication related side effects. To date, no study has evaluated the use of ketamine for total joint arthroplasty patients who demonstrate high levels of pain catastrophizing. We aim to study the effect of intra-operative ketamine administration on post-operative analgesic requirements and self-reported pain in patients undergoing total hip and total knee arthroplasty who demonstrate high levels of pain catastrophizing.

Inclusion Criteria:

• Adults, 18 years and older, undergoing primary total hip arthroplasty or total knee arthroplasty

Exclusion Criteria:

• History of intolerance or allergy to ketamine, either documented or self-reported.
• History of increased intra-ocular pressure, uncontrolled hypertension, increased intra-cranial pressure, psychosis.
• Unable to provide consent.
• Current incarceration.
• Pregnant or breast feeding

The investigator, participant, research staff and medical provider will all be masked. The pharmacy will maintain the randomization and will provide the code at the conclusion of the study prior to data analysis.