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Transfusion Evidence Alert and Round-Up

On this page you can view articles from previous editions of the Transfusion Evidence Alert and Round-Up; use the button on the left to sign up to receive future editions direct to your inbox. The Transfusion Evidence Alert is a monthly overview of 10 selected evidence-based publications in the field of transfusion medicine, including relevant COVID-19 articles. The articles are selected by experts in the field from the Systematic Review Initiative, funded by the four UK blood services. The Transfusion Evidence Round-Up is a quarterly overview of the top 10 high quality studies about an internationally relevant subject in the field of transfusion medicine. The articles are selected by members from the International Society of Blood Transfusion and drawn from the Transfusion Evidence Library and where relevant Stem Cell Evidence.

January 2022


  1. Accuracy of risk tools to predict critical bleeding in major trauma: a systematic review with meta-analysis
    The journal of trauma and acute care surgery. 2021

    Abstract

    BACKGROUND Early detection of critical bleeding by accurate tools can help ensure rapid delivery of blood products to improve outcomes in major trauma patients. We conducted a systematic review to evaluate the accuracy of risk tools to predict critical bleeding in patients with major trauma. METHODS PubMed, Embase and CENTRAL were searched up to February 2021 for studies investigating risk tools to predict critical bleeding for major trauma people in pre-hospital and emergency department. We followed the PRISMA-DTA guidelines. Two independent authors included studies, extracted data, appraised the quality using the Quality Assessment of Diagnostic Accuracy Studies-2 and assessed the certainty of evidence using thee Grading of Recommendations Assessment, Development and Evaluation methodology. Sensitivity, specificity and the Receiver Operating Characteristics curve for all selected triage tools. RESULTS Eighty-nine observational studies for adults and 12 observational studies for children met our inclusion criteria. In adults, we found 23 externally validated and 28 un-validated tools; in children, 3 externally validated tools and 5 un-validated. In the externally validated tools, we identified those including clinical, laboratory and ultrasound assessments. Among tools including only a clinical assessment, the Shock Index showed high sensitivity and specificity with the Certainty of Evidence ranging from very low to moderate in adults, as well as Shock Index Pediatric Age-adjusted (SIPA) with a moderate Certainty of Evidence. We found that tools using clinical, laboratory and ultrasound assessments were overall more accurate than those tools without all three components. CONCLUSIONS Clinicians should consider risk tools to predict critical bleeding in a time-sensitive setting like major life threatening trauma. The Shock index and SIPA are easy and handy tools to predict critical bleeding in the pre-hospital setting. In the emergency department, however, many other tools can be utilized which include laboratory and ultrasound assessments, depending on staff experience and resources. LEVEL OF EVIDENCE Systematic review, diagnostic Level III.
    PICO Summary

    Population

    Adults and children with major trauma (101 studies).

    Intervention

    Systematic review to identify the most accurate risk tools to predict critical bleeding.

    Comparison

    Outcome

    Twenty-three externally validated and 28 un-validated tools were found for adults, and 3 externally validated tools and 5 un-validated, for children. Among tools including only a clinical assessment, the Shock Index showed high sensitivity and specificity with the Certainty of Evidence ranging from very low to moderate in adults, as well as Shock Index Paediatric Age-adjusted with a moderate Certainty of Evidence. It was found that tools using clinical, laboratory and ultrasound assessments were overall more accurate than those tools without all three components.
  2. The Difference in Potential Harms between Whole Blood and Component Blood Transfusion in major Bleeding: A Rapid Systematic Review and Meta-Analysis of RCTs
    Transfusion medicine reviews. 2021

    Abstract

    Our aim was to assess whether there is a difference in outcomes of potential "all-cause" harm in the transfusion of whole blood (WB) compared to blood components (BC) for any bleeding patient regardless of age or clinical condition. We searched multiple electronic databases using a pre-defined search strategy from inception to 2(nd) March 2021. 1 reviewer screened, extracted, and analysed data, with verification by a second reviewer of all decisions. We used Cochrane ROB1 and GRADE to assess the quality of the evidence. We used predefined subgroups of trauma and non-trauma studies in the analysis. We included six RCTs (618 participants) which compared WB and BC transfusion therapy in major bleeding, one trauma trial (n = 107), and 5 surgical trials (non-trauma) (n = 511). We GRADED evidence as very-low for all outcomes (downgraded for high and unclear risk of bias, small sample size, and wide confidence intervals around the estimate). Our primary outcome (all-cause mortality at 24-hours and 30-days) was reported in 3 out of 6 included trials. There was no evidence of a difference in mortality of WB compared to BC therapy (very-low certainty evidence). There may be a benefit of WB therapy compared to BC therapy in the non-trauma subgroup, with a reduction in the duration of oxygen dependence (1 study; n = 60; mean difference 5.9 fewer hours [95% Confidence Interval [CI] -10.83, -0.99] in WB group), and a reduction in hospital stay (1 study, n = 64, median difference 6 fewer days in WB group) (very-low certainty evidence). For the remaining outcomes (organ injury, mechanical ventilation and intensive care unit requirement, infection, arterial/venous thrombotic events, and haemolytic transfusion reaction) there was no difference between WB and BC therapy (wide CI, crossing line of no effect), though many of these outcomes were based on small single studies (very-low certainty evidence). In conclusion, there appears to be little to no difference in harms between WB and BC therapy, based on small studies with very low certainty of the evidence. Further large trials are required to establish the overall safety of WB compared to BC, and to assess differences between trauma and non-trauma patients.
    PICO Summary

    Population

    Adults and children with any type of major bleeding (6 studies, n= 618).

    Intervention

    Fresh or whole blood (containing red blood cells (RBC), plasma, and platelets) from allogeneic donors (WB group).

    Comparison

    Blood component therapy, (RBC, and/or any forms of plasma, and/or platelets, and/or cryoprecipitate, or standard care), (BC group).

    Outcome

    All-cause mortality at 24-hours and 30-days was reported in 3 trials. There was no evidence of a difference in mortality of WB compared to BC therapy (very-low certainty evidence). For the remaining outcomes (organ injury, mechanical ventilation and intensive care unit requirement, infection, arterial/venous thrombotic events, and haemolytic transfusion reaction) there was no difference between WB and BC therapy (very-low certainty evidence).
  3. Restrictive vs. Liberal Red Blood Cell Transfusion Strategy in Patients With Acute Myocardial Infarction and Anemia: A Systematic Review and Meta-Analysis
    Frontiers in cardiovascular medicine. 2021;8:736163

    Abstract

    Objective: Anemia is frequent in patients with acute myocardial infarction (AMI), and the optimal red blood cell transfusion strategy for AMI patients with anemia is still controversial. We aimed to compare the efficacy of restrictive and liberal red cell transfusion strategies in AMI patients with anemia. Methods: We systematically searched PubMed, EMBASE, Web of Science, Cochrane Library, and Clinicaltrials.gov, from their inception until March 2021. Studies designed to compare the efficacy between restrictive and liberal red blood cell transfusion strategies in patients with AMI were included. The primary outcome was all-cause mortality, including overall mortality, in-hospital or follow-up mortality. Risk ratios (RR) with 95% confidence intervals (CI) were presented and pooled by random-effects models. Results: The search yielded a total of 6,630 participants in six studies. A total of 2,008 patients received restrictive red blood cell transfusion while 4,622 patients were given liberal red blood cell transfusion. No difference was found in overall mortality and follow-up mortality between restrictive and liberal transfusion groups (RR = 1.07, 95% CI = 0.82-1.40, P = 0.62; RR = 0.89, 95% CI = 0.56-1.42, P = 0.62). However, restrictive transfusion tended to have a higher risk of in-hospital mortality compared with liberal transfusion (RR = 1.22, 95% CI = 1.00-1.50, P = 0.05). No secondary outcomes, including follow-up reinfarction, stroke, and acute heart failure, differed significantly between the two groups. In addition, subgroup analysis showed no differences in overall mortality between the two groups based on sample size and design. Conclusion: Restrictive and liberal red blood cell transfusion have a similar effect on overall mortality and follow-up mortality in AMI patients with anemia. However, restrictive transfusion tended to have a higher risk of in-hospital mortality compared with liberal transfusion. The findings suggest that transfusion strategy should be further evaluated in future studies.
    PICO Summary

    Population

    Patients with acute myocardial infarction and anaemia (6 studies, n= 6,630).

    Intervention

    Restrictive red blood cell transfusion strategy (n= 2,008).

    Comparison

    Liberal red blood cell transfusion strategy (n= 4,622).

    Outcome

    No difference was found in overall mortality and follow-up mortality between restrictive and liberal transfusion groups. However, restrictive transfusion tended to have a higher risk of in-hospital mortality compared with liberal transfusion. No secondary outcomes, including follow-up reinfarction, stroke, and acute heart failure, differed significantly between the two groups. Subgroup analysis showed no differences in overall mortality between the two groups based on sample size and design.
  4. Effect of High-Titer Convalescent Plasma on Progression to Severe Respiratory Failure or Death in Hospitalized Patients With COVID-19 Pneumonia: A Randomized Clinical Trial
    JAMA network open. 2021;4(11):e2136246

    Abstract

    IMPORTANCE Convalescent plasma (CP) has been generally unsuccessful in preventing worsening of respiratory failure or death in hospitalized patients with COVID-19 pneumonia. OBJECTIVE To evaluate the efficacy of CP plus standard therapy (ST) vs ST alone in preventing worsening respiratory failure or death in patients with COVID-19 pneumonia. DESIGN, SETTING, AND PARTICIPANTS This prospective, open-label, randomized clinical trial enrolled (1:1 ratio) hospitalized patients with COVID-19 pneumonia to receive CP plus ST or ST alone between July 15 and December 8, 2020, at 27 clinical sites in Italy. Hospitalized adults with COVID-19 pneumonia and a partial pressure of oxygen-to-fraction of inspired oxygen (Pao2/Fio2) ratio between 350 and 200 mm Hg were eligible. INTERVENTIONS Patients in the experimental group received intravenous high-titer CP (≥1:160, by microneutralization test) plus ST. The volume of infused CP was 200 mL given from 1 to a maximum of 3 infusions. Patients in the control group received ST, represented by remdesivir, glucocorticoids, and low-molecular weight heparin, according to the Agenzia Italiana del Farmaco recommendations. MAIN OUTCOMES AND MEASURES The primary outcome was a composite of worsening respiratory failure (Pao2/Fio2 ratio <150 mm Hg) or death within 30 days from randomization. RESULTS Of the 487 randomized patients (241 to CP plus ST; 246 to ST alone), 312 (64.1%) were men; the median (IQR) age was 64 (54.0-74.0) years. The modified intention-to-treat population included 473 patients. The primary end point occurred in 59 of 231 patients (25.5%) treated with CP and ST and in 67 of 239 patients (28.0%) who received ST (odds ratio, 0.88; 95% CI, 0.59-1.33; P = .54). Adverse events occurred more frequently in the CP group (12 of 241 [5.0%]) compared with the control group (4 of 246 [1.6%]; P = .04). CONCLUSIONS AND RELEVANCE In patients with moderate to severe COVID-19 pneumonia, high-titer anti-SARS-CoV-2 CP did not reduce the progression to severe respiratory failure or death within 30 days. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT04716556.
    PICO Summary

    Population

    Patients with COVID-19 pneumonia (n= 487).

    Intervention

    Convalescent plasma (CP) plus standard therapy (ST), (n= 241).

    Comparison

    Standard therapy (n= 246).

    Outcome

    The primary outcome was a composite of worsening respiratory failure (Pao2/Fio2 ratio <150 mm Hg) or death within 30 days from randomization. The primary end point occurred in 59 of 231 patients (25.5%) treated with CP and ST and in 67 of 239 patients (28.0%) who received ST. Adverse events occurred more frequently in the CP group (12 of 241 (5.0%)) compared with the control group (4 of 246 (1.6%)).
  5. Coagulation Abnormalities and Clinical Complications in Children With SARS-CoV-2: A Systematic Review of 48,322 Patients
    Journal of pediatric hematology/oncology. 2021

    Abstract

    Given the limited information on the coagulation abnormalities of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in pediatric patients, we designed a systematic review to evaluate this topic. A comprehensive literature search was conducted for "SARS-CoV-2," "coagulopathy," and "pediatrics." Two authors independently screened the articles that the search returned for bleeding, thrombosis, anticoagulant and/or antiplatelet usage, and abnormal laboratory markers in pediatric patients with SARS-CoV-2, and the authors then extracted the relevant data. One hundred twenty-six publications were included. Thirty-four (27%) studies reported thrombotic complications in 504 patients. Thirty-one (25%) studies reported bleeding complications in 410 patients. Ninety-eight (78%) studies reported abnormal laboratory values in 6580 patients. Finally, 56 (44%) studies reported anticoagulant and/or antiplatelet usage in 3124 patients. The variety of laboratory abnormalities and coagulation complications associated with SARS-CoV-2 presented in this review highlights the complexity and variability of the disease presentation in infants and children.
    PICO Summary

    Population

    Paediatric patients with SARS-CoV-2 (126 studies, n= 48,332).

    Intervention

    Systematic review to evaluate coagulation abnormalities and clinical complications.

    Comparison

    Outcome

    Thirty-four (27%) studies reported thrombotic complications in 504 patients. Thirty-one (25%) studies reported bleeding complications in 410 patients. Ninety-eight (78%) studies reported abnormal laboratory values in 6,580 patients. Finally, 56 (44%) studies reported anticoagulant and/or antiplatelet usage in 3,124 patients.
  6. Deferiprone vs deferoxamine for transfusional iron overload in SCD and other anemias: a randomized, open-label, noninferiority study
    Blood advances. 2021

    Abstract

    Many people with sickle cell disease (SCD) or other anemias require chronic blood transfusions, which often causes iron overload and requires chelation therapy. The iron chelator deferiprone is often used in individuals with thalassemia syndromes, but data in patients with SCD are limited. This open-label study (NCT02041299) assessed the efficacy and safety of deferiprone in patients with SCD or other anemias receiving chronic transfusion therapy. A total of 228 patients (mean age: 16.9 [range 3-59] years; 46.9% female) were randomized to receive either oral deferiprone (n = 152) or subcutaneous deferoxamine (n = 76). The primary endpoint was change from baseline at 12 months in liver iron concentration (LIC), assessed by R2* magnetic resonance imaging (MRI). The least squares mean (standard error) change in LIC was -4.04 (0.48) mg/g dry weight for deferiprone vs -4.45 (0.57) mg/g dry weight for deferoxamine, with noninferiority of deferiprone to deferoxamine demonstrated by analysis of covariance (least squares mean difference 0.40 [0.56]; 96.01% confidence interval, -0.76, 1.57). Noninferiority of deferiprone was also shown for both cardiac T2* MRI and serum ferritin. Rates of overall adverse events (AEs), treatment-related AEs, serious AEs, and AEs leading to withdrawal did not differ significantly between the groups. AEs related to deferiprone treatment included abdominal pain (17.1% of patients), vomiting (14.5%), pyrexia (9.2%), increased alanine transferase (9.2%) and aspartate transferase levels (9.2%), neutropenia (2.6%), and agranulocytosis (0.7%). The efficacy and safety profiles of deferiprone were acceptable and consistent with those seen in patients with transfusion-dependent thalassemia.
    PICO Summary

    Population

    Patients with sickle cell disease or other anaemias receiving chronic transfusion therapy (n= 228).

    Intervention

    Oral deferiprone (n= 152).

    Comparison

    Subcutaneous deferoxamine (n= 76).

    Outcome

    The least squares mean (standard error) change in liver iron concentration was -4.04 (0.48) mg/g dry weight for deferiprone vs. -4.45 (0.57) mg/g dry weight for deferoxamine, with noninferiority of deferiprone to deferoxamine demonstrated by analysis of covariance. Non-inferiority of deferiprone was also shown for both cardiac T2* MRI and serum ferritin. Treatment-related adverse events (AEs), serious AEs, and AEs leading to withdrawal did not differ significantly between the groups.
  7. Role of AScorbic acid Infusion in critically ill patients with Transfusion Related Acute Lung Injury (ASTRALI)
    British journal of clinical pharmacology. 2021

    Abstract

    INTRODUCTION In critically ill patients, Transfusion Related Acute Lung Injury (TRALI) remains the leading cause of transfusion-related fatalities in critical care setting and associated with inflammation and oxidative stress state. Recent research raised the potential efficacy of high dose intravenous ascorbic acid in critically ill patients. OBJECTIVE The aim of this trial was to investigate the effect of high dose intravenous ascorbic acid (VC) as a targeted therapy for TRALI in terms of serum proinflammatory (interleukin-8, interleukin-1β, C-reactive protein), anti-inflammatory (interleukin-10), oxidative stress (superoxide dismutase, malondialdehyde) markers, and plasma VC levels. Secondary outcomes were oxygenation (PaO(2) /FiO(2) ratio), vasopressor use, duration of mechanical ventilation, ICU length of stay, 7-days mortality and 28-days mortality. METHODS Eighty critically ill patients with TRALI (n=80) were randomized to receive 2.5gm/6hr intravenous vitamin C for 96 hours (ASTRALI group) or placebo. Patients were followed-up to measure the outcomes initially (T0) and at the end of treatment (T96). RESULTS When compared to control group, ASTRALI group at T96, showed significantly higher median of interleukin-10 (31.6 ± 25.8 Vs. 17.7 ± 12.0 pg/mL, p<0.0001) levels and superoxide dismutase (12876 ± 4627 U/L Vs. 5895 ± 6632 U/L, p<0.0001) activities, lower median C-reactive protein (76 ± 50 Vs. 89 ± 56 mg/L, p=0.033), interleukin-8 (11.8 ± 7.3, 35.5 ± 19.8 pg/mL, p<0.0001), and malondialdehyde (0.197 ± 0.034 Vs. 0.234 ± 0.074 μM/L, p=0.002) levels. CONCLUSION High dose ascorbic acid was associated with significantly reduced oxidative stress, reduced pro-inflammatory markers except IL-1β, elevated anti-inflammatory marker, and elevated plasma VC levels.
    PICO Summary

    Population

    Critically ill patients with transfusion related acute lung injury (TRALI), (n= 80).

    Intervention

    Intravenous ascorbic acid (n= 40).

    Comparison

    Placebo (n= 40).

    Outcome

    High dose ascorbic acid was associated with significantly reduced oxidative stress, reduced pro-inflammatory markers except IL-1β, elevated anti-inflammatory marker, and elevated plasma VC levels.
  8. Intravenous iron to treat anaemia following critical care: a multicentre feasibility randomised trial
    British journal of anaesthesia. 2021

    Abstract

    BACKGROUND Anaemia is common and associated with poor outcomes in survivors of critical illness. However, the optimal treatment strategy is unclear. METHODS We conducted a multicentre, feasibility RCT to compare either a single dose of ferric carboxymaltose 1000 mg i.v. or usual care in patients being discharged from the ICU with moderate or severe anaemia (haemoglobin ≤100 g L(-1)). We collected data on feasibility (recruitment, randomisation, follow-up), biological efficacy, and clinical outcomes. RESULTS Ninety-eight participants were randomly allocated (49 in each arm). The overall recruitment rate was 34% with 6.5 participants recruited on average per month. Forty-seven of 49 (96%) participants received the intervention. Patient-reported outcome measures were available for 79/93 (85%) survivors at 90 days. Intravenous iron resulted in a higher mean (standard deviation [sd]) haemoglobin at 28 days (119.8 [13.3] vs 106.7 [14.9] g L(-1)) and 90 days (130.5 [15.1] vs 122.7 [17.3] g L(-1)), adjusted mean difference (10.98 g L(-1); 95% confidence interval [CI], 4.96-17.01; P<0.001) over 90 days after randomisation. Infection rates were similar in both groups. Hospital readmissions at 90 days post-ICU discharge were lower in the i.v. iron group (7/40 vs 15/39; risk ratio=0.46; 95% CI, 0.21-0.99; P=0.037). The median (inter-quartile range) post-ICU hospital stay was shorter in the i.v. iron group but did not reach statistical significance (5.0 [3.0-13.0] vs 9.0 [5.0-16.0] days, P=0.15). CONCLUSION A large, multicentre RCT of i.v. iron to treat anaemia in survivors of critical illness appears feasible and is necessary to determine the effects on patient-centred outcomes. CLINICAL TRIAL REGISTRATION ISRCTN13721808 (www.isrctn.com).
    PICO Summary

    Population

    Patients being discharged from the intensive care unit (ICU) with moderate or severe anaemia (n= 98).

    Intervention

    Single dose of ferric carboxymaltose (n= 49).

    Comparison

    Usual care (n= 49).

    Outcome

    Patient-reported outcome measures were available for 85% survivors at 90 days. Intravenous iron resulted in a higher mean (standard deviation [sd]) haemoglobin at 28 days (119.8 [13.3] vs. 106.7 [14.9] g L(-1)) and 90 days (130.5 [15.1] vs. 122.7 [17.3] g L(-1)), adjusted mean difference (10.98 g L(-1)) over 90 days after randomisation. Infection rates were similar in both groups. Hospital readmissions at 90 days post-ICU discharge were lower in the intravenous iron group (7/40 vs. 15/39). The median (inter-quartile range) post-ICU hospital stay was shorter in the intravenous iron group but did not reach statistical significance (5.0 [3.0-13.0] vs. 9.0 [5.0-16.0] days.
  9. Viscoelastometric versus standard coagulation tests to guide periprocedural transfusion in adults with cirrhosis: A meta-analysis of randomized controlled trials
    Vox sanguinis. 2021

    Abstract

    BACKGROUND AND OBJECTIVES Due to rebalanced haemostasis in cirrhosis, viscoelastometric testing (VET) is more accurate than standard coagulation tests (SCTs) in preprocedural haemostatic evaluation, resulting in decreased unnecessary transfusion. We aimed to determine the impact of VET-guided strategy on postprocedural bleeding, periprocedural transfusion rates and quantities, transfusion-related adverse events (TRAEs), lengths of stay (LOS) and mortality from randomized controlled trials (RCTs) of cirrhotic patients. METHODS PubMed and EMBASE were searched for RCTs comparing VET-guided with SCT-guided transfusion in cirrhotic adults undergoing esophagogastroduodenoscopy, liver transplantation or other invasive interventions. Using random-effects models, the pooled risk ratios (RRs) and/or mean differences (MDs) of postprocedural bleeding-free events and the other outcomes were estimated alongside 95% confidence intervals (CIs). RESULTS Of seven included RCTs (n = 421; 72.2% men; mean age 49.1 years), VET-guided transfusion did not change postprocedural bleeding-free statuses (RR 1.05; 95% CI 0.94-1.17). However, VET-based algorithms decreased the rates of fresh frozen plasma (FFP; RR 0.52; 95% CI 0.35-0.77) and platelet transfusions (RR 0.34; 95% CI 0.16-0.73), the quantities of transfused FFP (MD -1.39 units; 95% CI -2.18 to -0.60), platelets (MD -1.06 units; 95% CI -2.01 to -0.12) and cryoprecipitate (MD -7.13 units; 95% CI -14.20 to -0.07) and the risk of TRAEs (RR 0.42; 95% CI 0.27-0.65). The overall mortality rates and LOS were not significantly different between two groups. CONCLUSION Compared with conventional SCT-guided, VET-guided strategy decreases periprocedural plasma and platelet transfusions and TRAEs, without increasing haemorrhagic complications, LOS or mortality in cirrhosis.
    PICO Summary

    Population

    Patients with cirrhosis undergoing esophagogastroduodenoscopy, liver transplantation or other invasive interventions (7 studies, n= 421).

    Intervention

    Viscoelastometric testing (VET) guided transfusion.

    Comparison

    Standard coagulation testing (SCT) guided transfusion.

    Outcome

    VET-guided transfusion did not change post-procedural bleeding-free statuses. However, VET-based algorithms decreased the rates of fresh frozen plasma (FFP) and platelet transfusions, the quantities of transfused FFP (MD -1.39 units), platelets (MD -1.06 units) and cryoprecipitate (MD -7.13 units) and the risk of transfusion-related adverse events. The overall mortality rates and lengths of stay were not significantly different between two groups.
  10. Individualised or liberal red blood cell transfusion after cardiac surgery: a randomised controlled trial
    British journal of anaesthesia. 2021

    Abstract

    BACKGROUND Current practice guidelines for red blood cell (RBC) transfusion in ICUs are based on haemoglobin threshold, without consideration of oxygen delivery or consumption. We aimed to evaluate an individual physiological threshold-guided by central venous oxygen saturation ScvO(2). METHODS In a randomised study in two French academic hospitals, 164 patients who were admitted to ICU after cardiac surgery with postoperative haemoglobin <9 g dl(-1) were randomised to receive a transfusion with one unit of RBCs (haemoglobin group) or transfusion only if the ScvO(2) was <70% (individualised group). The primary outcome was the number of subjects receiving at least one unit of RBCs. The secondary composite outcome was acute kidney injury, stroke, myocardial infarction, acute heart failure, mesenteric ischaemia, or in-hospital mortality. One- and 6-month mortality were evaluated during follow-up. RESULTS The primary outcome was observed for 80 of 80 subjects (100%) in the haemoglobin group and in 61 of 77 patients (79%) in the individualised group (absolute risk -21% [-32.0; -14.0]; P<0.001). There was no significant difference in the secondary outcome between the two groups. Follow-up showed a non-significant difference in mortality at 1 and 6 months. CONCLUSIONS An individualised strategy based on an central venous oxygen saturation threshold of 70% allows for a more restrictive red blood cell transfusion strategy with no incidence on postoperative morbidity or 6-month mortality. CLINICAL TRIAL REGISTRATION NCT02963883.
    PICO Summary

    Population

    Patients admitted to intensive care unit after cardiac surgery (n= 164).

    Intervention

    Transfusion with one unit of red blood cells (RBCs), (haemoglobin group), (n= 82).

    Comparison

    Transfusion only if the ScvO(2) was <70% (individualised group), (n= 82).

    Outcome

    The number of patients receiving at least one unit of RBCs was observed for 80 of 80 subjects (100%) in the haemoglobin group and in 61 of 77 patients (79%) in the individualised group. There was no significant difference in the secondary outcome between the two groups. Follow-up showed a non-significant difference in mortality at 1 and 6 months.