Prevalence and Predictors of Prolonged Post-surgical Opioid Use: a Prospective Observational Cohort Study

There are growing concerns that surgery is a risk factor for chronic opioid use. Existing studies suggest that post-surgical opioid prescribing intended for the short-term management of acute pain may result in unintended long-term opioid use for a small, but meaningful number of patients.

Increasing numbers of patients are discharged from hospital post-surgery with opioids for the management of their acute post-surgical pain. Opioids have proven efficacy for the management of acute post-surgical pain, but can cause significant harm when used long-term for non-cancer pain. Evidence suggests that post-surgical opioid use continues in some patients for years after surgery.

Identification of patients at risk of prolonged opioid use after surgery may assist in reducing the adverse outcomes associated with long-term opioid use. Pre-operative risk stratification tools may be of use in identifying surgical patients at risk of long-term opioid use. Validated tools are widely used to identify patients at high risk of opioid misuse in the chronic pain setting, but currently there is no optimal method to predict patients at risk of chronic opioid use after surgery.

Existing studies have found that a wide range of patient characteristics and psychiatric comorbidities are associated with long-term opioid use in a post-surgical setting.

There are 5 primary study procedures in the investigators research project:

• Enrolment in the study: Subjects will be recruited and enrolled at the pre-operative admission clinic and day surgery unit at St Vincent's Private Hospital, Sydney. This study aims to enrol 1000 patients.
• Informed consent: Patients who meet inclusion criteria, and agree to enrol in the study will be asked to read and sign an informed consent document.
• Initial questionnaire: Trained nursing staff will administer an initial questionnaire to all patients participating in the study. This questionnaire will gather data regarding potential predictors of delayed opiate cessation including age, sex, operation type, pre-operative opioid use, depression traits, anxiety traits, addictive traits, perceived susceptibility to addiction, average hours of sleep per night, history of chronic pain, and perceived general health.
• Follow-up questionnaire: At approximately 90 days post-surgery, a follow-up questionnaire will be administered to all enrolled subjects via phone call or email. This questionnaire will determine current pain scores and details regarding current pain medication usage.
• Statistical analysis: Once data collection is complete, identifying details will be removed, and data will be entered into a password-protected electronic database. The investigators will analyse data from all patients and determine the prevalence of delayed opioid cessation, and which questionnaire items independently predict delayed opioid cessation.

The investigators primary study objective is to determine the prevalence of prolonged post-surgical opioid use, defined by our study as patients taking opioids >90 days post-surgery. The investigators secondary objective is to identify patient-related factors that are independently associated with prolonged post-surgical opioid use. These factors may be used to develop a pre-operative screening tool for patients undergoing surgery, in order to assign a level of risk for chronic post-surgical opioid use.

Inclusion criteria

• Age ≥18 years
• Able to give written informed consent
• Willing to participate and comply with the study
• Scheduled to undergo surgery at St Vincent's Private Hospital, and attending the pre-admission clinic or day surgery unit

Exclusion criteria

• Opioid tolerant patients (patients who are chronically receiving opioid analgesics on a daily basis)
• Scheduled to undergo surgery relating to malignancy
• Surgical procedures completed under local anaesthetic
• Minimally invasive procedures including gastroscopy, colonoscopy, bronchoscopy, cardioversion or transoesophageal echo
• Patients who were unable to complete study questionnaires due to psychological illness, medical condition or significant language barrier were excluded from the study.