What Perioperative Factors are Associated with High-Risk Daily Morphine Milligram Equivalent Totals in Spinal Decompressions?

Introduction:
Morphine Milligram Equivalent (MME) dosing recommendations were introduced in 2016 by the Centers for Disease Control and Prevention (CDC) as a guideline for primary care providers to aid in understanding the cumulative effect of opioids and the risk associated with long term use in chronic pain patients. The formula is defined as: Strength per Unit X (Number of Units/Days’ Supply) X MME = MME/Day. Daily dosages of ≥ 100 MME/day are associated with an almost nine-fold increased risk of overdose. Current general recommendations endorse the lowest effective dose and ≤ 50 MME/day.

Aims/

Objectives:
To determine what factors are associated with high-risk daily Morphine Milligram Equivalent totals in patients undergoing spinal decompression.

Methods:
Retrospective analysis was conducted on 85 patients that underwent spinal decompressive surgery within a multi-center network over 2 years. Average MME/day was calculated as the sum of qualifying inpatient MMEs administered divided by the sum of inpatient length of stay (LOS). 21 independent variables were collected from demographic, clinical and surgical domains and were subject to comparative analysis. Data was then grouped and coded for logistic regression analysis.

Results:
Overall mean MME per day was 56.1 ± 41, with a range of 1.7-220 MME/day. “High MME” was defined as greater than the overall upper quartile value, 75.03 MME/day. A total of 21 patients were determined to have “High MME” during their inpatient stay. Patients with high MMEs were significantly younger (mean age 50.9 ± 17.5) than those with lower MMEs/day (69.2 ± 12.2), p=6.71E-05. Patients with high MMEs were also significantly more likely to carry a psychiatric diagnosis (anxiety, depression, bipolar disorder) (43.8% [n=14] vs 13.2% [n=7], p=0.00156). Additionally, patients who had high MMEs had lower ASA scores (2.4 ± 0.5 vs 2.7 ± 0.6) and reported higher preoperative Visual Analog Scale (VAS) pain scores (4.6 ± 2.8 vs 2.6 ± 3.4) than patients with lower MMEs/day. There were no significant demographic or intraoperative factors between the two groups, nor any significant difference in LOS. When subject to logistic regression, the final model identified for each unit decrease in age grouping increased the risk of high MME 0.31 times or 69.4%. A psychiatric comorbidity increased the risk of high MME by 8.7 times, or 770%.

Conclusions:
Patients with high MME/day who underwent spinal decompression were significantly younger with lower ASA scores, and higher preoperative VAS scores than those with lower MME/day. The incidence of psychiatric comorbidity was also higher in those with high MMEs. Psychiatric comorbidity in younger patients predicted a significant increased risk of higher MME. Pre-operative opioid risk education and mitigation strategies should be considered in patients with high MME risk, especially in younger patients and those with psychiatric comorbidities.