Background & Aims
Concomitant use of high dose Gabapentinoids (Gabapentin or Pregabalin) and high dose opioids is associated with increased incidences of peri-operative complications including post-operative respiratory depression, difficult post op pain management, poor wound healing, and risk of infection (1). This combination is also associated with high risk of accidental overdose, as high as 49% in the epidemiological study from Canada in 2017. High dose of Gabapentinoids is associated with respiratory depression, weight gain and increasing the risk of falls in the elderly population group. The Faculty of Pain Medicine in United Kingdom advises such “at-risk” patients be referred to pain services pre-operatively [2]. We developed a pathway at our institution to identify patients with high dose opioids and/ or high dose Gabapentinoids scheduled for elective surgery and referred them to the chronic pain service for pain medication optimization before surgery aiming for better perioperative outcome.
Methods
We identified patients on high-dose opioids with or without concomitant use of high dose of gabapentinoids and identified triggers for referring them to the chronic pain service. The Faculty of Pain Medicine Opioid Aware guidance suggests limiting dose of opioid under 120 mg of oral morphine equivalence per day for management of chronic non cancer pain. We used the ANZCA FPM Opioid Calculator to calculate the Oral Morphine Equivalence (OME) of different opioids. Further, when we identified patients above 1800 mg of gabapentin per day or above 300 mg of pregabalin per day, coupled with high dose of opioids, it triggered a referral electronically to the chronic pain service and was logged into a database. The referrals were reviewed by chronic pain consultants and after an individualised assessment of the risks, a plan was made and and communicated to the preassessment team and documented on patient electronic records. Awareness of the pathway was done with emails & drop-in sessions.
Results
(Partial data analysed, at the time of abstract submission in Jan 2024). There were 104 referrals to the chronic pain service, 62% were male, the mean age was 57yrs (34-77), the mean BMI was 34 (20-45) and 19% had concomitant diagnosis of obstructive sleep apnoea. The mean Oral Morphine Equivalent dose was 146mg/ day (40-490 mgs). 81% of this cohort were also prescribed high dose gabapentinoids, 42% were also on an anti-depressant and 19% were prescribed a benzodiazepine. About one third of them (31%) were already seen by a specialist pain service for their chronic pain condition. The most common specialty under which the elective surgery was planned was spinal surgery (69%). Following referral, preassessment notes and current pain medications were reviewed by a chronic pain consultant which prompted an outcome in form of notes review and advice (65%), an urgent face-to-face appointment in pain clinic (17%), a telephone consultation (9%) and medication advice letter to them & GP (9%).
Conclusions
Our findings from this quality improvement project demonstrates a significant proportion of this patient group have additional risk factors for peri-operative complications, e.g., obesity, diagnosed or suspected Obstructive Sleep Apnea and pain medication polypharmacy. This is a challenging and complex patient cohort and a multidisciplinary approach to their chronic conditions and planned surgery is essential with input from surgical specialties, preassessment, chronic pain, anaesthetic and primary care colleagues working together to make their perioperative journey safer with minimal perioperative complications. The preassessment team plays a key role in identifying this high-risk cohorts and coordinating a safer perioperative journey for the patients. Further work would involve conducting multicentre studies to identify these cohorts and raise awareness about risks of high doses of opioids and/ or gabapentinoids to effect changes in prescribing patterns of health care professionals.
References
1. Benyamin R, Trescot AM, Datta S, et al. Opioid complications and side effects. Pain Physician. 2008; 11 S105-S120
2. The Faculty of Pain Medicine. Surgery and Opioids: Best Practice Guidelines. 2021.