Methadone Versus Morphine for Orthopedic Surgery Patients

Patients will receive 1-4 mg midazolam before being transferred to the operating room. All patients will receive standard ASA monitoring. In the operating room, the anesthesiologist will open a randomization envelope to determine patient group assignment (see below). Patients will be anesthetized with 0.2 mg/kg ketamine, 2 µg/kg fentanyl and propofol or etomidate IV. Muscle relaxant of the anesthesiologist's choice will be given and the patient will be intubated. After intubation, the computer-generated randomization codes stored in opaque envelopes will be opened. The patients will be randomized to one of two groups:

1. Methadone group: Patients will receive 0.2 mg/kg of methadone IV immediately after intubation
2. Control group: Patients will receive 0.2 mg/kg of morphine IV immediately after intubation

The unblinded investigator will draw the drug and dilute to a total volume of 10 cc. This syringe will be handed to the anesthesia provider, who will administer the medication after induction. They will be maintained with oxygen, air and an inhalational agent of anesthesiologist's choice, targeted at BIS between 40 and 60. Additional analgesia will be provided with fentanyl in 50 µg increments as required throughout surgery. At the end of surgery the neuromuscular block will be reversed and patients will breathe spontaneously. Fentanyl will be titrated to maintain a respiratory rate of 12-15 breaths per minute to obtain an O2 saturation \> 95% and the other extubation criteria are met before tracheal extubation . The intraoperative use of narcotics, sedatives and anesthetic drugs will be noted. The type of surgery, the duration of surgery and use of additional analgesics and antiemetics will be noted.

An investigator blinded to randomization will track the patients in the PACU. If rescue medication is necessary, morphine IV will be given in 2-4 mg increments up to a total of 20 mg. If the patients continue to report pain (VAS \> 4), IV hydromorphone will be given in 0.5 mg dose every 10-15 minutes until the patient has adequate analgesia (VAS \< 4), as decided by the PACU nurse.

Patients will receive morphine patient-controlled analgesia (PCA) for pain relief as the primary analgesic. Percocet (Acetaminophen/Oxycodone 325 mg/5 mg) or Lortab (Acetaminophen/Hydrocodone 325/5 mg) will be prescribed as needed to maintain VRS \< 4.

In the PACU, vital signs including respiratory rate, heart rate, non-invasive blood pressure, sedation score and oxygen saturation will be recorded every 15 minutes. VAS scores for pain will be obtained from the patient every 15 minutes until the patient is discharged to the floor. VAS (visual analog scale) is a 100-mm scale where 0 = no pain and 100 = worst pain imaginable. The investigator will record sedation scores every 15 minutes using the following scale until patient is discharged to the floor:

0-Patient is fully alert

1. Patient has intermittent sedation
2. Patient sedated but responsive to verbal stimuli
3. Patient unresponsive to verbal stimuli

Patients will be seen at 8 am and 4 pm on the following day and will be contacted at home or in the hospital on POD 2 and 3 for information regarding pain scores and analgesic requirement. The initial dose of rescue analgesic and time it is given will be recorded. VAS at rest and on movement will be recorded, when the patients are seen or VRS will be recorded via phone contact. Morphine or other analgesics required during the first 24 and 48 hours after surgery, and times to first ambulation, first fluid, solid and flatus will be recorded, as will incidence and severity of postoperative nausea and vomiting be recorded.

Our primary outcome will be opioid consumption during the 48 hours after surgery. All analgesics consumed will be converted to morphine equivalent.

The secondary outcomes will be

1. Overall rescue analgesic, converted into equipotent doses compared between the two groups
2. Side effects with special attention paid to respiratory rate and possible respiratory depression, and PONV
3. Visual pain score at 48 h post-op.