The effect of regional nerve block on perioperative delirium in hip fracture surgery for the elderly: A systematic review and meta-analysis of randomized controlled trials

Introduction: With minimal systemic toxicity, an analgesic effect of regional nerve block (RNB) has been proved in hip fracture cases. Analgesia was expected to reduce delirium by controlling pain, a known predisposing factor for delirium. We performed a meta-analysis to investigate the effect of RNB on delirium after hip fracture surgery in elderly patients. We aimed to answer the question: Can regional nerve block reduce postoperative delirium in hip fracture patients?. Hypothesis: Our hypothesis was that RNB could reduce postoperative delirium after hip fracture surgery in elderly patients. Patients and Methods: MEDLINE, Embase, and Cochrane Library databases were searched systematically for studies published before September 9, 2020, investigating the effect of RNB on perioperative delirium after hip fracture in elderly patients. We performed synthetic analyses for overall RNB compared to a control group both in 1) overall elderly patients, including the cognitively impaired, and 2) for patients without cognitive impairment (CoI). Also, we performed subgroup analyses for each of the block techniques, such as fascia-iliac block (FIB) and femoral nerve block (FNB). Results: Eight randomized controlled trials compared the incidence of perioperative delirium between the RNB and control groups. A pooled analysis showed no differences in delirium incidence between the RNB and control groups (odds ratio [OR], 0.66; 95% confidence interval [CI], 0.36–1.22; P = 0.18; I2 = 58%) in overall elderly patients. However, there was a significant reduction of delirium in the RNB group in patients without CoI (OR, 0.44; 95% CI, 0.21–0.94; P = 0.03; I2 = 51%). In the subgroup analyses, we were unable to discern any differences in delirium incidence between the groups for FIB (OR, 0.89; 95% CI, 0.19–4.19; P = 0.88; I2 = 78%) and FNB (OR 0.61; 95% CI, 0.31–1.20, P = 0.15, I2 = 47%). Conclusions: In cases of hip fracture in elderly, RNB demonstrated a preventive effect on perioperative delirium for patients without preoperative CoI. No significant reduction in perioperative delirium was observed when cognitively impaired patients were included.