What Perioperative Factors Are Associated With High-risk Daily Morphine Milligram Equivalent Totals in Spinal Decompressions?

Study design/setting: Retrospective cohort analysis.

Objective: To determine what factors are associated with high-risk daily morphine milligram equivalent (MME) totals in patients undergoing spinal decompression.

Background: Daily dosages of ≥100 MME/d are associated with an almost 9-fold increased risk of overdose. Current general recommendations endorse the lowest effective dose and ≤50 MME/d.

Materials and methods: Retrospective analysis was conducted on 260 patients who underwent spinal decompressive surgery. Average MME/d was calculated as the sum of qualifying inpatient MMEs administered divided by the sum of inpatient length of stay. Independent variables across demographic, clinical, and surgical domains were subject to comparative and logistic regression analysis.

Results: Overall MME per day was 54.19 ± 39.37, with a range of 1.67-218.34 MME/d. Sixty-six patients were determined to have "high-risk MME." These patients were significantly younger (58.8 ± 13.1 vs 70.53 ± 11.5; P < 0.001) and reported higher preoperative pain visual analog scale (VAS; 4.8 ± 3 vs 2.8 ± 3.3; P = 0.0021) than the patients at low risk. In addition, high-risk patients had significantly higher body mass indexes (BMIs; P < 0.05) and received ketamine as part of anesthesia (P < 0.05). Patients who consumed high-risk dosages of MMEs in the perioperative period were more likely to have been on opioids before surgery and to report higher pain scores at 4-6 week follow-ups (P < 0.05). The final logistics regression model identified independent risk factors to be younger age, higher BMIs and preoperative VAS, and prior use of opioids and intraoperative ketamine.

Conclusions: Patients with high MME per day who underwent spinal decompression were significantly younger with higher BMIs and preoperative VAS with an increased incidence of preoperative opioid use and intraoperative ketamine. A closer look at interaction models revealed that a combination of high preoperative pain and intraoperative ketamine usage were at a significantly increased risk of higher MME consumption. Preoperative opioid risk education and mitigation strategies should be considered in patients with high MME risk, especially in younger patients already utilizing opioids before surgery.