Association of peripheral nerve blocks with increased postoperative pain and opioid use in orthopaedic surgery: a single-centre retrospective cohort study.

Abstract

Peripheral nerve blocks have become popular in orthopaedic surgeries to improve acute postoperative pain. However, studies are mixed on their effectiveness in decreasing postoperative opioid consumption. A more comprehensive analysis is necessary to understand if peripheral nerve blocks reduce postoperative opioid exposure and risk for opioid dependence. This retrospective cohort study evaluated electronic health record data for adults undergoing orthopaedic surgery with general anaesthesia from 2016 to 2020 at the Massachusetts General Hospital. Linear models were fitted on propensity-weighted data to characterise the association between single injection peripheral nerve blocks and clinical outcomes. Our primary outcomes were maximum pain score and cumulative opioid dose, quantified in morphine milligram equivalents, administered in the PACU. Post-discharge outcomes associated with pain and opioid consumption were also evaluated. Among 22 956 patients, peripheral nerve block administration was associated with lower maximum pain scores and lower probability of opioid administration in the PACU. However, it was associated with higher maximum pain scores and a 22.7% increase in opioid consumption during the hospital stay. Peripheral nerve blocks were associated with an increase in opioid prescriptions at 30 days after discharge, but no increase at 90 or 180 days, and with decreased chronic pain diagnoses 1 yr after operation. Although single injection peripheral nerve blocks were effective in reducing immediate postoperative pain and opioid consumption, they were associated with greater opioid consumption that could increase the risk for opioid dependence. Standardised protocols to mitigate the risk for rebound pain could help minimise postoperative opioid exposure.