Iron supplementation has been evaluated in several randomized controlled trials (RCTs) for its potential to increase baseline hemoglobin and decrease red blood cell transfusion during cardiac surgery. This study's main objective was to evaluate the current evidence for iron administration in cardiac surgery patients. Methods We searched MEDLINE, EMBASE, CENTRAL, Web of Science databases, and Google Scholar from inception to 19 November 2020 for RCTs evaluating perioperative iron administration in adult patients undergoing cardiac surgery. The RCTs were assessed using a risk of bias assessment and the quality of evidence was assessed using the grading of recommendations, assessments, development, and evaluations. Results We reviewed 1,767 citations, and five studies (n = 554) met the inclusion criteria. The use of iron showed no statistical difference in incidence of transfusion (risk ratio, 0.86; 95% confidence interval, 0.65 to 1.13). Trial sequential analysis suggested an optimal information size of 1,132 participants, which the accrued information size did not reach. Conclusion The current literature does not support or refute the routine use of iron therapy in cardiac surgery patients. Trial registration PROSPERO (CRD42020161927); registered

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The development of plastic fiberoptic catheters, cheaper and less fragile than glass ones, has enabled the more widespread use of oxyhaemoglobin saturation (SO2) monitoring. They allow direct determinations of SO2 to be made, using reflection spectrophotometry. The purpose of the present work was to evaluate the accuracy of SO2 measurements as provided by these catheters. The studies were performed in dogs, with large variations of SO2, acid-base balance and haematocrit levels.