Title:

Impact of Ketamine on Opioid Utilization in Patients with Pre-existing Opioid Tolerance Undergoing LumbarSpinal Fusion Surgery

 

Introduction:

Lumbar fusion surgery causes significant postoperative pain.Many of these patients are opioid tolerant due to long-termpreoperative opioid use, complicating postoperative analgesicmanagement. Ketamine use demonstrates opioid-sparingeffects with reduced pain scores and fewer adverse events invarious procedures, including lumbar fusion [1-5]. However,research on its effects in patients with defined opioid toleranceremains unclear. This study aimed to evaluate ketamine as apostoperative analgesic adjunct in opioid tolerant patientsundergoing lumbar fusion.

 

Materials and Methods:

This was a single center retrospective cohort study of 2,466patients who received lumbar fusion surgery at the University ofTennessee Medical Center from 2017 through 2023. Patientswere assigned to one of three groups based on their opioidtolerance status as measured in morphine milligramequivalents (MME) per day prior to procedure. These includedopioid naïve (< 30 MME), opioid exposed (30-60 MME), andopioid tolerant ( >60 MME). The opioid exposed and opiatetolerant groups of patients were further divided intopostoperative ketamine infusion or control subgroups. Opiatenaïve patients did not receive ketamine. This cohort was alsocompared against a historical opioid naïve cohort to assess forsecular changes across the hospital. The primary outcomemeasured was post-operative length of stay (LOS), withsecondary outcomes of opioid utilization in the first 72 hourspostoperatively.

 

Results:

Baseline demographics were similar among groups. Both opioidexposed and opioid tolerant patients receiving ketamine showedan increased LOS compared to their respective control groups.Only opioid exposed patients receiving ketamine had significantlylower opioid requirements on postoperative day (POD) 1-3compared to those who did not receive ketamine. There was nosignificant reduction in opioid tolerant patients receiving ketamineon POD 1-3 compared to those who did not receive ketamine. 

 

Discussion:

Perioperative ketamine infusion significantly reduced postoperativeopioid requirements in opioid exposed, but not tolerant patients.This interesting finding may be due to tolerance physiology, butwarrants further research. The opioid sparing benefit in opioidexposed patients was limited to POD 1-3. The ketamine infusioncould reasonably be discontinued after POD 3, while still achievingthe opioid sparing effects. The increased length of stay observedin patients receiving ketamine is unlikely to be explained by secularchanges across the hospital. There was a system-wide reduction inopioid prescribing over time, but no change in LOS.

 

References:

1. Yuan J, Chen S, et al. Intraoperative Intravenous Infusion of Esketamine Has Opioid-Sparing Effect and Improves theQuality of Recovery in Patients Undergoing Thoracic Surgery: A Randomized, Double-Blind, Placebo-ControlledClinical Trial. PMID: 36608010

2. Huda AU, Minhas R, et al. Intravenous ketamine in gynaecological surgeries reduces pain score and opioidconsumption. PMID: 37246675

3. Mariscal G, Morales J, et al. Meta-analysis of the efficacy of ketamine in postoperative pain control in adolescentidiopathic scoliosis patients undergoing spinal fusion. PMID: 36253657

4. Murphy GS, Avram MJ, et al. Perioperative Methadone and Ketamine for Postoperative Pain Control in Spinal SurgicalPatients: A Randomized, Double-blind, Placebo-controlled Trial. PMID: 33730151

5. Brinck ECV, Maisnieme K, et al. Analgesic Effect of Intraoperative Intravenous S-Ketamine in Opioid-Naïve PatientsAfter Major Lumbar Fusion Surgery Is Temporary and Not Dose-Dependent: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial. PMID: 32167978