Effects of anaesthesia type on development of persistent postoperative opioid utilisation: a South Korean nationwide cohort study

INTRODUCTION: Previous studies comparing the effects of general and regional anaesthesia on postoperative opioid use have focused primarily on the immediate postoperative period, with limited investigations into long-term outcomes. METHODS: This retrospective cohort study included 558,944 patients aged ≥ 18 y who underwent one of nine surgical procedures (thoracotomy; total hip arthroplasty; total knee arthroplasty; shoulder arthroplasty; transurethral resection of the prostate; inguinal hernia repair; knee arthroscopy; varicose vein surgery; and caesarean section) that required regional anaesthesia, general anaesthesia or combined general/regional anaesthesia. The primary outcome was the incidence of persistent postoperative opioid utilisation, which was defined as having filled ≥ 10 prescriptions or a supply of > 120 days between postoperative days 91 and 365. Age, sex, medical comorbidities, pre-operative medications and surgery type were balanced among regional anaesthesia, general anaesthesia and combined general/regional anaesthesia using pairwise propensity score matching. RESULTS: General anaesthesia had significantly higher odds than regional anaesthesia for the development of persistent postoperative opioid utilisation (odds ratio 2.13, 95%CI 1.50-3.01, p < 0.001). The odds ratio of general anaesthesia vs. combined general/regional anaesthesia was significant in patients undergoing thoracotomy (odds ratio 1.47, 95%CI 1.25-1.74, p < 0.001). In the overall population, the regional anaesthesia group consumed fewer opioids than the other groups. Among the patients undergoing thoracotomy, the combined general/regional anaesthesia group consumed fewer opioids than the general anaesthesia group. DISCUSSION: This study found that regional anaesthesia was associated with a reduction in persistent postoperative opioid utilisation, particularly in patients undergoing thoracotomy.