The Effect of Preoperative Opioid Dosage on Postoperative Outcomes in Patients Undergoing Knee Surgery.

BACKGROUND

Opioid prescription before knee replacement surgery is associated with longer hospital stays, more postsurgical pain, and a higher rate of complications. Despite the growing evidence against opioids, they remain popular preoperative pain management prescriptions.

OBJECTIVES

The purpose of this study was to examine the effects of dosage of preoperative opioid use on orthopedic knee surgery pain control and postoperative outcomes and complications.

STUDY DESIGN

Observational, retrospective evaluation.

SETTING

University of Wisconsin Madison hospitals.

METHODS

The patients underwent orthopedic knee surgery between May 1, 2014 and April 30, 2015. We randomly selected 197 patients and divided them into 2 groups that had preoperative opioid dosages of either low dose <= 120 mEq morphine (MME) or high dose >120 MME. Of 197 patients, 100 were in the low dose morphine group, whereas 97 were high dose. The cutoff at 120 MME was calculated to be the median dosage across all patients. The primary outcomes were compared, differences in postoperative pain control, and range of motion (ROM). Secondary outcomes included anesthetic complications, length of hospital stay, postoperative opioid dose, and postoperative complications.

RESULTS

There were no statistically significant differences between the groups with regard to postoperative pain control, ROM, and immediate postoperative complications. Both groups showed similar length of hospitalization (2.199 to 2.304 days; P = 0.374), rate of postoperative infection, and joint intervention. The high dose group was more likely to have postoperative hemarthrosis and emergency department (ED) visits. However, the low dose group was more likely to have hypertension concurrently.

LIMITATIONS

Because the study length was restricted to one year, the lack of data on longer term prognosis may limit extrapolation of data. Subjectivity of pain is difficult to measure and compare objectively. This study was not randomized prospectively, which may bias certain results due to unobserved differences.

CONCLUSIONS

Preoperative opioid dose did not affect postoperative pain control or ROM in patients who received knee surgeries. Higher preoperative opioid doses were associated with more hemarthrosis and ED visits. Further exploration into quality of life indices and surgical complications such as need for revision may be a fruitful avenue.

KEY WORDS

Opioids, analgesic, knee pain, total knee replacement, knee surgery, pre-operative opioids, knee outcomes.