(216) Patterns of inpatient opioid trajectories following major or orthopaedic surgery

Background: Opioids are widely used in the postoperative setting to manage pain. However, less is known about patterns of administered opioid use immediately following surgery in hospital.

Objectives: To identify opioid utilisation trajectories within inpatients following major or orthopaedic surgery and patient factors associated with these trajectories.

Methods: A retrospective study included adult patients admitted to a teaching hospital in the North-West of England between 2010-2021 for major/orthopaedic surgery and who remained in hospital for 1-182 days. Opioid exposure was determined as such if patients were administered (rather than prescribed) the drug in hospital. Group-based trajectory modelling (GBTM) was used to classify patients into groups according to their morphine milligram equivalents (MME)/day and numbers of opioid types co-administered restricted to the first 90 days of admission. GBTM allows for the identification of homogenous subgroups, with the composition and number of subpopulations derived from the data over time. The best-fit model was determined by Bayesian Information Criterion. Differences in length of stay and proportion of patients who were discharged on opioids from hospital were assessed using descriptive statistics. Multinomial regression was used to assess factors associated with these trajectories including age, sex, ethnicity, deprivation, and Charlson Comorbidity Index (CCI).

Results: We included 14,085 patients contributing to 18,012 admissions. Mean age (SD) was 59 years (20), 54% were female and 96% were of white ethnicity. Using GBTM, four groups were identified. T1: low MME/day and administered monotherapy (n=12,725 admissions, 71%); T2: moderate MME/day with fewer opioid types (n=2,060, 11%); T3: high MME/day, fewer opioid types (n=951, 5%); T4: moderate MME/day, several opioid types (n=2,276; 13%). Those in T3 (high MME/day group) had a significantly longer median length of stay compared to other groups (T3: 15 days vs. T1: 4, T2: 8, T4: 4; p< 0.001) and included the highest proportion of patients discharged on opioids (T3: 68% vs. T1: 50%, T2: 62%, T4: 59%; p< 0.001). Older patients and those with a CCI of >3 were more likely to be assigned to the higher MME/day groups (relative risk ratio [95% CI] for T3: age: 1.00 [1.00, 1.01]; CCI >3: 2.31 [1.72, 3.11]). High deprivation was weakly related to the higher MME/day groups; sex and ethnicity had no associations.

Conclusions: Trajectories of postoperative administered opioid utilisation among inpatients were associated with both length of stay and opioid use at discharge. A smaller proportion of individuals in the high MME/day trajectory were more likely to be older with more comorbidities, likely reflecting a higher prevalence of pain and analgesia in these individuals.