Remote ischaemic preconditioning (RIPC) is an intervention involving brief periods of limb ischaemia to protect remote organs from subsequent ischaemic injury. Although evidence exists on the beneficial effects of RIPC on biomarkers, its effect on survival is unknown. We performed a meta-analysis of randomised controlled trials (RCTs) to evaluate whether RIPC improves survival in noncardiac surgery. We searched several electronic databases for randomised trials comparing RIPC vs a control group in adult noncardiac surgical settings. The primary outcome was mortality at the longest follow-up available. We conducted a random-effects meta-analysis to calculate the risk ratio (RR) and 95% confidence intervals (CIs). Bayesian statistics were used to estimate the probability of mortality benefit (RR <1). We identified 72 RCTs, which included 7457 subjects. Mortality was reported in 28 RCTs and was lower in the RIPC group compared with the control group (88/2122 [4.1%] vs 102/1767 [5.8%]; RR 0.74, 95% CI 0.57-0.98, P=0.03; I²=0%; moderate certainty; number needed to treat = 67), corresponding to a 97.0% probability of any reduction in mortality. RIPC was also associated with a reduced incidence of postoperative stroke (moderate certainty) and with a shorter duration of hospital stay (low certainty). RIPC was associated with improved survival and reduced postoperative stroke and hospital stay in noncardiac surgery. These findings warrant careful considerations of the benefits of RIPC and support the need for a large, multicentre RCT to confirm these promising results. CRD42024588358 (PROSPERO).

Hypercoagulability and thrombo-inflammation are the main reasons for death in COVID-19 patients. It is unclear whether there is a difference between D-dimer levels in patients without or with COVID-19 acute respiratory distress syndrome (ARDS). We searched PubMed, EMBASE, and ClinicalTrails.gov databases looking for studies reporting D-dimer levels in patients without or with COVID-19 ARDS. Secondary endpoints included length of hospital stay, and mortality data at the longest follow-up available. We included 12 retrospective and 3 prospective studies with overall 2,828 patients, of whom 1,404 (49.6%) had non-COVID-19 ARDS and 1,424 had COVID-19 ARDS. D-dimer levels were not significantly higher in non-COVID-19 ARDS than in COVID-19 ARDS patients (mean 7.65 mg/L vs. mean 6.20 mg/L MD 0.88 [CI: -0.61 to 2.38] p = 0.25; I² = 85%) while the length of hospital stay was shorter (non-COVID-19 mean 37.4 days vs. COVID-19 mean 48.5 days, MD -10.92 [CI: -16.71 to -5.14] p < 0.001; I² = 44%). No difference in mortality was observed: non-COVID-19 ARDS 418/1167 (35.8%) vs. COVID-19 ARDS 467/1201 (38.8%). We found no difference in the mean D-dimer levels between non-COVID-19 ARDS and COVID-19 ARDS patients.