Morphine Consumption in Joint Replacement Patients, With or Without Gabapentin Treatment

Multiple Doses of Gabapentin and Postoperative Morphine Consumption in Total Knee Arthroplasty

Total knee arthroplasty is amongst the most painful procedures postoperatively, and pain management can be a challenge. Different measures have been introduced to manage severe postoperative pain int hese patients. Previous studies have investigated gabapentin in acute postoperative pain and demonstrated reducted pain, postoperative morphine consumption, morphine related side effects, and postoperative pain scores. To date, this analgesia adjunct has yet to be investigated in total joint arthroplasty patients.

The study was submitted to Health Canada and received the letter of no objection. A randomized, double-blind, placebo-controlled study. The randomization scheme will be prepared and will be done by the pharmacy department at McMaster University. Ninety patients undergoing primary knee arthroplasty will be recruited from the preoperative clinic. Forty-five patients in each population will be allocated to a gabapentin group and the other forty-five to a placebo group.

Inclusion Criteria:

• participants aged 19-90
• elective single joint, primary total knee arthroplasty
• use of PCA with morphine for postoperative pain control has been discussed and agreed upon between patient and anesthetist

Exclusion Criteria:

• bilateral total knee arthroplasty
• revision knee arthroplasty
• underlying disease of epilepsy, seizure, or chronic pain syndrome
• active gastrointestinal bleeding within the last 6 months
• history of non-steroidal anti-inflammatory drug (NSAID) induced asthma
• known or suspected history of drug or alcohol abuse
• participant currently takes gabapentin or pregabalin for any reason
• participant currently takes pain medication that is more potency than codeine or oxycodone (morphine, hydromorphone, meperidine, methadone, fentanyl, including any long acting narcotics)
• known allergy to study medications: gabapentin, morphine, NSAID, acetaminophen
• unable to tolerate morphine
• liver impairments
• kidney impairment or calculated creatinine clearance by Cockcroft-Gault formula is <=60ml/min
• pregnancy or breast-feeding
• participant currently receives associated worker's compensation benefits (WSIB)
• participant unable or unwilling to give written or informed consent
• unable to use PCA