Postoperative pain assessment, and opioid utilisation after hospital discharge following colectomy

Abstract

Background and aims Opioids have an established role in the management of postoperative pain; however, inappropriate opioid utilisation is evident, influenced by several factors including the overreliance on unidimensional pain assessment tools to guide opioid dosing. This thesis aims to advance the understanding of the management of postoperative pain, including pain assessment, opioid utilisation trends and persistent postoperative opioid use (PPOU) following colectomy. Methods Three interrelated studies were performed:1) a systematic review to assess the measurement properties of unidimensional and functional pain assessment tools in adult postoperative patients. Two pharmacoepidemiological studies were conducted using linked primary and secondary care data sources from England. 2): a retrospective cohort study to determine the prevalence and predictors of PPOU after colectomy. 3) A repeated cross-sectional analysis to describe the temporal trends in opioid prescriptions following discharge after colectomy. Results After a systematic search of four databases, 31 studies involving 12,498 participants were included. The quality of evidence for the measurement properties of all identified unidimensional pain assessment tools was suboptimal. Studies on functional assessment tools were scarce, with only one study including an ‘objective pain score’. However, it had suboptimal quality, with a very low quality of evidence. Amongst the 93,262 patients undergoing colectomy between 2010 and 2019, 15,081 (16.2%) were issued at least one opioid prescription within 90 days of discharge. From the whole cohort, 7540 (8.1%) developed PPOU. The odds of developing persistent opioid use were highest [OR 3.41 (95%CI 3.07–3.77)] for individuals who used long-acting opioid formulations in the 180 days before colectomy. Predictors of PPOU included previous opioid exposure; high deprivation index; multiple comorbidities; use of long-acting opioids; white race; and open surgery. Minimally invasive surgical approaches were associated with lower odds of PPOU. There was a downward trend in the proportion of opioid naïve patients who had post-discharge opioid prescriptions, from 11.4% in 2010 to 6.7% in 2019 (-41.3%, p < 0.001). However, the proportions prescribed opioids prior to surgery remained stable [57.5% in 2010 to 58.3% in 2019 (p = 0.637)]. Codeine represented 44.5% of all prescriptions and prescribing increased by 14.5%. Prescriptions for morphine and oxycodone rose significantly by 76.6% and 31.0% respectively, while tramadol prescribing dropped by 48.0%. Conclusion This thesis contributes to a deeper understanding of postoperative pain assessment and challenges the validity and reliability of unidimensional tools to quantify postoperative pain, and shows limited evidence for the use of functional pain assessment tools. There have been changes in the prescription of opioids following colectomy over the last decade and PPOU does occur after colectomy in England.