This is a clinical trial of intrathecal morphine for patients Patient with primary as well as revision knee and hip arthroplasty under regional anesthesia. This study would include a total of 134 patients. It is the intention to randomize these patients postoperatively into 2 groups of patients:

Group 1 - Patients will receive intrathecal morphine 100 mcg in addition to the standard dose of bupivacaine and 15 mcg of fentanyl for spinal anesthesia.

Group 2 - Patients will not receive intrathecal morphine. Patients will receive only bupivacaine and 15 mcg of fentanyl for spinal anesthesia.

It is postulated that the use of intrathecal morphine may be associated with an increase length of stay in the hospital.

Procedures:

Preoperative phase- The patients will receive the consent form together with the standard sheet in the pre-admission unit or remotely via telephone or email, usually one week before surgery, explaining intrathecal morphine and its benefits and drawbacks. These patients will receive an educational booklet regarding the "fast track protocol" which includes clear instruction related to their upcoming surgery. The material covers a wide range of topics such as instructions related to fasting for solids and liquids before coming for surgery, the expectation of pain relief and physiotherapy, types of anesthesia and expected length of hospital stay. Upon hospital admission, one hour before the procedure, patients will receive gabapentin 300mg, celecoxib 400mg (will be reduced to celecoxib 200mg in patients ≥ 65 years old) and acetaminophen 1000mg orally.

Intraoperative phase- Surgical procedures to be included in the study are elective primary as well as revision arthroplasty of knee and hip joints under spinal anesthesia with or without sedation. Patient will be randomized to one of two groups. One group will receive intrathecal morphine 100 mcg in addition to the standard dose of bupivacaine and fentanyl 15 mcg for spinal anesthesia and another group will not receive intrathecal morphine. Upon prosthesis implant, the surgeon will infiltrate periarticular 100 ml (40 ml bupivacaine 0.5% + 60 ml of normal saline) as per the orthopedic protocol. Sedation will be titrated to keeping modified Ramsay sedations score (RSS) between 3 and 5.

Postoperative phase- upon emergence from anesthesia patients will be taken to the recovery room. As per our hospital protocol, the patient will be catheterized if the bladder residual volume by ultrasound is 500ml or more. Post-operative pain score and opioid requirements and complications including urinary retention, vomiting and respiratory depression will be recorded. Overall duration of stay in the hospital will be noted. If any patient requires catheterization of bladder, the duration of catheter requirement and frequency of catheterization will be monitored and recorded.

Inclusion Criteria:

• ASA 1-3
• Age 18 to 85 years
• BMI 18 to 40 kg/cm2
• Patient with primary as well as revision knee and hip arthroplasty under regional anesthesia only.
• Provision of written informed consent.

Exclusion Criteria:

• Language barrier or difficulty in communication: inability to read write or speak English
• Allergy to morphine
• Patients under increased risk for respiratory depression with intrathecal morphine (central apnea)
• Patients with pre-existing urinary problems
• Women of child bearing potential not on birth control
• Patients with chronic pain who are currently on pain medications
• Patients with cognitive impairment
• Patients who have alcohol and/or other substance dependency