Friday, June 14, 2019
How bad is chronic opioid use for spine surgery outcomes?
The literature makes it very clear that preoperative opioid use is associated with worse outcomes and more frequent complications following spine surgery. However, most of these studies have used large administrative databases with limitations inherent with that type of study design. In order to get a more detailed understanding of how preoperative opioid use affects postoperative outcomes, Dr. Hills and colleagues from Vanderbilt used their institution's spine surgery registry to identify over 2000 elective spine surgery patients from 2010-2017. They then queried the Tennessee Prescription Drug Monitoring Program (PDMP) to determine opioid prescription volumes for the 9 months prior to surgery and 12 months after surgery. They converted prescribed opioids to morphine milligram equivalents (MME) and defined high preoperative opioid use as greater than 30 MME per day for the two weeks preceding surgery. They defined chronic opioid use as using opioids on at least 50% of the days for at least a three-month period. At baseline, the chronic opioid users were significantly younger, more likely to be smoking, more likely to have arthritis, more likely to have Medicare or Medicaid, more likely to be ASA class 3 or 4, more likely to have anxiety or depression, more likely to be undergoing revision surgery, and had worse baseline symptoms. In their unadjusted analyses, they found that chronic opioid users were less likely to see a clinically meaningful improvement (defined as a 30% improvement vs. baseline) on the numeric rating scale for arm/leg pain, neck/back pain, the NDI/ODI or the EQ-5D. They were also less likely to be satisfied, less likely to return to work, more likely to have postoperative complications, and much more likely to use opioids chronically after surgery. Multivariate logistic regression showed all of these results to hold true while controlling the measured baseline differences. After controlling for chronic opioid use, high dose use did not portend worse outcomes than lower dose use other than increasing the odds of chronic use postoperatively. Only one third of chronic opioid users stopped their chronic use postoperatively.
While much has been written about the association between preoperative opioid use and poor outcomes following spine surgery, this study adds to the literature by looking at the topic in closer detail and including patient reported outcomes. The authors looked at both chronicity of use and dose and found that chronicity was a much stronger predictor of poor outcomes than high dose use. These results suggest that lower dose use over many months could be just as harmful for outcomes as higher dose use. The results held true even after accounting for the significant baseline differences between the two groups. This study begs the question about the effect of preoperative weaning of opioids but does not provide any data on whether or not that is effective. It is not clear if chronic opioid use causes permanent changes in pain pathways that are the driver of poor outcomes or if these changes are reversible with weaning. Additionally, chronic opioid use may be associated with other unmeasured confounders that are the true causative agents behind the poor outcomes. In reality, the relationship between preoperative chronic opioid use and outcomes is highly complex. There is essentially no doubt that patients would do better postoperatively if they wean down or stop opioid use preoperatively, though the magnitude of that benefit on patient reported outcomes is unclear. Observational studies likely cannot definitively answer the question about whether or not weaning opioids is helpful due to the potential for unmeasured confounders. Similarly, an RCT would be challenging to interpret on an intention to treat basis due to a likely high rate of failure to wean among those randomized to weaning. Determining the magnitude of benefit of preoperative opioid weaning may be academic as it seems almost certain to convey some benefit. Additionally, many patients are likely not willing to be weaned preoperatively and draconian weaning efforts would most likely result in illicit opioid use. Hopefully the opioid problem will improve over the long-term as physicians continue to change their prescribing habits and surgeons encounter fewer spine surgery patients on chronic opioid therapy. Until then, patients and their surgeons will likely continue to struggle with this.
Please read Dr. Hill's article on this topic in the June 15 issue. Does this change how you view the effect of preoperative chronic opioid use on spine surgery outcomes? Let us know by leaving a comment on The Spine Blog.
Adam Pearson, MD, MS
Associate Web Editor