ICU · Haematology / transfusion
Anaemia in the ICU — Phlebotomy, Functional Iron & Restrictive Transfusion
Also known as Anaemia in the ICU · ICU-acquired anaemia · Phlebotomy · Blood conservation · Functional iron deficiency · Hepcidin · Anaemia of chronic disease · IV iron · Erythropoietin · EPO · Restrictive transfusion · TRICC trial · TRISS trial · TRALI · TACO · Iron studies · Transfusion thresholds
Anaemia is near-universal in ICU and deepens with every day of the stay (mean admission Hb 11.3 g/dL in the ABC cohort). The number 1 MODIFIABLE cause is the phlebotomy (the classic ICU series bled patients 3.4 times a day, mean 41.5 mL/day, 762 mL per stay — and daily diagnostic volumes up to 377 mL have been reported). The other causes: the inflammation (anaemia of chronic disease — IL-6-driven hepcidin internalises ferroportin and causes functional iron deficiency), the blood loss (GI, surgical, coagulopathy), the haemodilution (fluids), the marrow suppression (sepsis, CKD, low EPO), the nutritional (B12, folate, iron). The management: reduce the phlebotomy (the blood-conservation bundle — paediatric-size tubes cut draw volume almost half, question-driven testing, batching, cumulative-volume review), the restrictive transfusion (Hb under 70 — TRICC, TRISS, TRIPICU, TRICS III; one unit at a time), the IV iron for the functional iron deficiency (IRONMAN: higher discharge Hb, no significant transfusion saving), and EPO is NOT routine (no transfusion reduction, thrombotic events HR 1.41 — Corwin 2007). In acute MI the threshold is contested: MINT/REALITY left possible harm with a restrictive strategy and the 2025 AABB guideline conditionally suggests transfusing when Hb is under 10 g/dL.
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- Phlebotomy is the number 1 MODIFIABLE cause of ICU anaemia — the classic series drew 3.4 samples a day (mean 41.5 mL/day, 762 mL per admission; arterial-line patients 944 mL); the blood-conservation bundle (paediatric-size tubes cut draw volume 46.8 per cent, question-driven testing, batching, cumulative-volume review) is the single most effective intervention
- ICU anaemia is usually FUNCTIONAL iron deficiency — IL-6 drives hepcidin, hepcidin binds ferroportin and triggers its internalisation and degradation, so iron is locked in macrophages and enterocytes; give IV iron, not oral
- Restrictive transfusion (Hb <70 g/L) is supported in general ICU (TRICC), septic shock (TRISS), stable children (TRIPICU) and cardiac surgery (TRICS III); TRISS transfused ONE unit at the threshold, then rechecked
- Acute MI is the contested zone — REALITY met non-inferiority but the CI included possible clinically important harm, MINT showed death/MI 16.9 vs 14.5 per cent favouring liberal (RR 1.15, P=0.07), and the 2025 AABB guideline conditionally suggests a liberal strategy (transfuse under 10 g/dL) in AMI
- EPO is NOT routine for ICU anaemia — Corwin 2007 (1460 patients): no reduction in transfusions and a significant increase in thrombotic events (HR 1.41)
- Haemodilution from fluid resuscitation causes APPARENT anaemia (the Hb is diluted) — treat the cause, not the number
- TRALI is the donor-antibody ARDS-like reaction and a leading cause of transfusion-related mortality (2019 consensus: Type I without, Type II with an ARDS risk factor) — supportive care only, NOT diuretics; TACO is circulatory overload — diuretics, and BNP helps confirm it (sensitivity 81 per cent, specificity 89 per cent)
Meet the patient
A 68-year-old man is on ICU day 9 with severe necrotising pancreatitis, ventilated for a week and on CRRT for AKI since day 3. His haemoglobin has drifted from 112 to 67 g/L. He is afebrile, stable on no vasopressors, lactate 1.1, no active bleeding. Ferritin 680, transferrin saturation 14 per cent, CRP 95, reticulocytes low. The registrar asks whether to transfuse two units.[1]
Two questions decide the answer, and they decide every ICU transfusion: why is he anaemic? (here, phlebotomy plus inflammation-driven functional iron deficiency, not bleeding), and does he need the oxygen-carrying capacity right now? (he does not — stable, no ACS, no shock). The number alone never transfuses the patient.[1]
References21ShowHide
- [1]Hébert PC, Wells G, Blajchman MA, et al A multicenter, randomized, controlled clinical trial of transfusion requirements in critical care. Transfusion Requirements in Critical Care Investigators, Canadian Critical Care Trials Group N Engl J Med, 1999.PMID 9971864
- [2]Holst LB, Haase N, Wetterslev J, et al Lower versus higher hemoglobin threshold for transfusion in septic shock N Engl J Med, 2014.PMID 25270275
- [3]Lacroix J, Hébert PC, Hutchison JS, et al Transfusion strategies for patients in pediatric intensive care units N Engl J Med, 2007.PMID 17442904
- [4]Mazer CD, Whitlock RP, Fergusson DA, et al Restrictive or Liberal Red-Cell Transfusion for Cardiac Surgery N Engl J Med, 2017.PMID 29130845
- [5]Ducrocq G, Gonzalez-Juanatey JR, Puymirat E, et al. Effect of a Restrictive vs Liberal Blood Transfusion Strategy on Major Cardiovascular Events Among Patients With Acute Myocardial Infarction and Anemia: The REALITY Randomized Clinical Trial JAMA, 2021.PMID 33560322
- [6]Carson JL, Brooks MM, Abbott JD, et al Restrictive or Liberal Transfusion Strategy in Myocardial Infarction and Anemia N Engl J Med, 2023.PMID 37952133
- [7]Vlaar APJ, Toy P, Fung M, et al. A consensus redefinition of transfusion-related acute lung injury Transfusion, 2019.PMID 30993745
- [8]Smoller BR, Kruskall MS Phlebotomy for diagnostic laboratory tests in adults. Pattern of use and effect on transfusion requirements N Engl J Med, 1986.PMID 3702919
- [9]Smoller BR, Kruskall MS Reducing adult phlebotomy blood loss with the use of pediatric-sized blood collection tubes Am J Clin Pathol, 1989.PMID 2729182
- [10]Helmer P, et al Avoidable Blood Loss in Critical Care and Patient Blood Management: Scoping Review of Diagnostic Blood Loss J Clin Med, 2022.PMID 35054014
- [11]Vincent JL, Baron JF, Reinhart K, et al Anemia and blood transfusion in critically ill patients JAMA, 2002.PMID 12243637
- [12]Corwin HL, Gettinger A, Fabian TC, et al Efficacy and safety of epoetin alfa in critically ill patients N Engl J Med, 2007.PMID 17804841
- [13]Nemeth E, Rivera S, Gabayan V, et al. IL-6 mediates hypoferremia of inflammation by inducing the synthesis of the iron regulatory hormone hepcidin J Clin Invest, 2004.PMID 15124018
- [14]Nemeth E, Tuttle MS, Powelson J, et al Hepcidin regulates cellular iron efflux by binding to ferroportin and inducing its internalization Science, 2004.PMID 15514116
- [15]Litton E, Baker S, et al Intravenous iron or placebo for anaemia in intensive care: the IRONMAN multicentre randomized blinded trial : A randomized trial of IV iron in critical illness Intensive Care Med, 2016.PMID 27686346
- [16]Pagano MB, et al Red Cell Transfusion in Acute Myocardial Infarction: AABB International Clinical Practice Guidelines Ann Intern Med, 2025.PMID 40825204
- [17]Zhou L, Giacherio D, Cooling L, et al Use of B-natriuretic peptide as a diagnostic marker in the differential diagnosis of transfusion-associated circulatory overload Transfusion, 2005.PMID 15987348
- [18]Matzek LJ, et al A Contemporary Analysis of Phlebotomy and Iatrogenic Anemia Development Throughout Hospitalization in Critically Ill Adults Anesth Analg, 2022.PMID 35977360
- [19]Villanueva C, Colomo A, Bosch A, et al Transfusion strategies for acute upper gastrointestinal bleeding N Engl J Med, 2013.PMID 23281973
- [20]Rock GA, Shumak KH, Buskard NA, et al Comparison of plasma exchange with plasma infusion in the treatment of thrombotic thrombocytopenic purpura. Canadian Apheresis Study Group N Engl J Med, 1991.PMID 2062330
- [21]Marik PE, Corwin HL Acute lung injury following blood transfusion: expanding the definition Crit Care Med, 2008.PMID 18824899