Preoperative intravenous versus oral iron supplementation for elective surgery: evidence based on 12 randomized trials

AIM: This study aims to clarify hematological parameters, transfusion requirements, and adverse events of preoperative intravenous (IVIS) versus oral iron supplementation (OIS) in elective surgery patients. METHODS: We conducted a comprehensive literature search across multiple databases up to 10 December 2023. Twelve RCTs involving 930 participants met our eligibility criteria. Our analysis focused on post-treatment hemoglobin levels, changes in hemoglobin from baseline, ferritin levels, hemoglobin attainment rates, transfusion requirements, and adverse events. We employed the random-effects model for data synthesis, calculating pooled standard mean differences (SMD) or mean differences (MD) or risk ratios (RR) with 95% confidence intervals (CI). Methodological quality was assessed using the Cochrane ROB 2 tool. The GRADE approach evaluated the confidence in effect estimates. FINDINGS: IVIS significantly improved post-treatment hemoglobin levels (MD = 0.77 g/dL, 95% CI [0.30 to 1.23]), hemoglobin increments (MD = 0.69 g/dL, 95% CI [0.01 to 1.37]), and ferritin levels (MD = 260.03 ng/mL, 95% CI [119.65 to 400.42]) compared to OIS. IVIS also led to a higher hemoglobin attainment rate (RR = 1.88, 95% CI [1.24 to 2.86]). No significant differences were noted in transfusion rates or volumes. IVIS was associated with fewer digestive (RR = 0.10, 95% CI [0.05 to 0.22]; I2 = 0%) but more pain-related adverse events (RR = 7.79, 95% CI [1.78 to 34.07]; I2 = 0%). Hospital stay durations and mortality rates were similar between the two groups. INTERPRETATION: IVIS offers a superior improvement in hematological parameters for elective surgery patients but not reducing transfusion needs compared to OIS. While IVIS has fewer digestive adverse events, it increases pain-related complications. These findings highlight the importance of personalized approaches in selecting iron supplementation methods, carefully balancing time, efficacy, and adverse event profiles. REGISTRATION: PROSPERO CRD42023483284.