This is a prospective, randomized study of ketamine versus no ketamine in approximately 100 patients undergoing hemorrhoidectomy for Grade III or IV hemorrhoids. The participants will be blinded to which treatment arm they are assigned, because participants will be under anesthesia when the ketamine is administered. The investigators will know whether the participant receives ketamine or not.

Participants will be randomized into 2 groups: intraoperative ketamine infusion during operation or routine anesthesia with no ketamine. Participants are pre-medicated in the operating room with the same regimen: Gabapentin 300mg, Ultram 50mg, and Tylenol 1000mg.

For participants in the ketamine group, a pain dose of ketamine 0.3mg/kg IV bolus dosing will be given prior to incision. If the procedure lasts longer than 1 hour, an additional bolus dose will be given. All participants will undergo general anesthesia and receive routine anesthesia care, aside from ketamine verus no ketamine. All participants will also receive standard local anesthesia including a local regional perianal nerve block.

The procedure will be performed by three different surgeons, with the surgery done the same way using ligasure hemorrhoidectomy. Participants will all be sent home with the same post-operative instructions and pain medications to include: Tylenol 1000mg, oxycodone 5mg, ibuprofen 800mg, fiber/miralax, and tub baths twice daily for 15 minutes.

A patient pain handout will be given to participants upon discharge with instructions to rate pain according to a numeric rating scale and the Wong-Baker FACES pain scale. Participants will be contacted by a member of the research team to assess their post-operative pain based on a numeric rating scale. All participants will undergo post-operative clinic follow-up at 2 weeks post-operation. At that time they will be instructed to bring their oxycodone bottle to assess how many pills the participant required. The clinic medical assistant will count the number of remaining pills and record this in the electronic medical record. If a participant forgets their pain scale record or medications, a post-operative phone interview will be performed after the clinic appointment to gather this information.

The investigators will randomize 50 participants to the ketamine group and 50 participants to the placebo group. Study will take place until all participants have been analyzed, approximately 8-12 months. Randomization will occur using a statistical method with study arms placed into individual envelopes that will be stored at the University of Oklahoma (OU) Surgery Center. The investigator will blindly pull an envelope from the stack which will identify the participant's treatment arm. The participants will be blinded and not informed of their arm of the study as to not create bias toward subjective pain. Practitioners will not be blinded for ease of medication administration. The procedures will occur at OU Surgery Center by one of three surgeons. Anesthesiologists will administer ketamine based on study arm.

Inclusion Criteria:

• Adults aged 18-100
• Undergoing a hemorrhoidectomy for Grade III or IV hemorrhoids.

Exclusion Criteria:

• Inability to undergo general anesthesia
• Contraindications to hemorrhoidectomy
• History of schizophrenia or other hallucinatory psychiatric illnesses
• History of psychosis
• Chronic narcotic usage defined as either having a pain contract with a pain management specialist and no narcotic usage for one month prior to hemorrhoidectomy.