Abstract: We included 51 RCTs with 2793 participants; of these 45 RCTs (2491 participants: peripheral nerve block = 1288; comparators = 1203) were included in meta-analyses. There are 11 ongoing studies and three awaiting classification. Compared to systemic analgesia alone, peripheral nerve blocks reduced: pain at rest on arrival in the postoperative care unit (SMD -1.12, 95% CI -1.67 to -0.56; 9 trials, 429 participants; equivalent to 3.2 on 0 to 10 scale; moderate-quality evidence); risk of acute confusional status: risk ratio (RR) 0.10 95% CI 0.02 to 0.54; 1 trial, 225 participants; number needed to treat for additional benefit (NNTB) 12, 95% CI 11 to 22; very low-quality evidence); pruritus (RR 0.16, 95% CI 0.04 to 0.70; 2 trials, 259 participants for continuous peripheral nerve blocks; NNTB 4 (95% CI 4 to 8); very low-quality evidence); hospital length of stay (SMD -0.75, 95% CI -1.02 to -0.48; very low-quality evidence; 2 trials, 249 participants; equivalent to 0.75 day). Participant satisfaction increased (SMD 0.67, 95% CI 0.45 to 0.89; low-quality evidence; 5 trials, 363 participants; equivalent to 2.4 on 0 to 10 scale). We did not find a difference for the number of participants walking on postoperative day one (very low-quality evidence). Two nerve block-related complications were reported: one local haematoma and one delayed persistent paresis. Compared to neuraxial blocks, peripheral nerve blocks reduced the risk of pruritus (RR 0.33, 95% CI 0.19 to 0.58; 6 trials, 299 participants; moderate-quality evidence; NNTB 6 (95% CI 5 to 9). We did not find a difference for pain at rest on arrival in the postoperative care unit (moderate-quality evidence); number of nerve block-related complications (low-quality evidence); acute confusional status (very low-quality evidence); hospital length of stay (low quality-evidence); time to first walk (low-quality evidence); or participant satisfaction (high-quality evidence). We found that peripheral nerve blocks provide better pain control compared to systemic analgesia with no major differences between peripheral nerve blocks and neuraxial blocks. We also found that peripheral nerve blocks may be associated with reduced risk of postoperative acute confusional state and a modest reduction in hospital length of stay that could be meaningful in terms of cost reduction considering the increasing numbers of procedures performed annually. Compared to systemic analgesia alone, there is moderate-quality evidence that peripheral nerve blocks reduce postoperative pain, low-quality evidence that patient satisfaction is increased and very low-quality evidence for reductions in acute confusional status, pruritus and hospital length of stay . We found moderate-quality evidence that peripheral nerve blocks reduce pruritus compared with neuraxial blocks. The 11 ongoing studies, once completed, and the three studies awaiting classification may alter the conclusions of the review once assessed

Plain-language summary: We included 51 studies (2793 participants) in the review and analysed results from 45 studies (2491 participants). There are 11 ongoing studies and three awaiting classification. Funding sources included governments, charities, institutions, industry (in part, n = 1); over half were unspecified (n = 29). Compared to systemic analgesia, we found that peripheral nerve blocks reduce pain, reduce the risk of becoming confused (e.g. not knowing the date, time, or location) (for every 12 people treated one fewer will become confused), reduce itching (for every 4 people treated one fewer will develop itch), hospital length of stay (equivalent to 0.75 day) and increase patient satisfaction for pain treatment (equivalent to 2.4 points more on a 0 to 10 scale). We did not find a difference in time to first walk after surgery. Two people had complications: one local haematoma and one delayed persistent muscle weakness. The quality of evidence for peripheral nerve blocks compared with systemic pain relievers was rated as moderate to very low. The quality of evidence for peripheral nerve blocks compared to neuraxial blocks was rated as high for patient satisfaction, moderate for reducing itch, similar pain relief, low for similar block-related complications, hospital length of stay and time to first walk. Evidence for confusion was assessed as very low quality. Evidence quality was downgraded to low or very low due to flawed study designs and limited numbers of trials and participants.