Best Evidence Topics
  • Send this BET as an Email
  • Make a Comment on this BET

Should critically ill patients be routinely transfused to a normal haemoglobin level?

Three Part Question

In [critically ill children] does [red cell transfusion to normal haemoglobin levels] improve [survival and reduce incidence of complications or duration of mechanical ventilation]?

Clinical Scenario

Joseph, a 4-year-old boy with septic shock, lactic acidosis and multi-organ failure has been admitted to the paediatric intensive care unit. Mechanical ventilation, vaso-active support and renal replacement therapy (CVVHD) are initiated. His haemoglobin level is 8.8 g/dl (5.5 mmol/l).
The senior consultant decides to order a red cell transfusion in order to optimise oxygen delivery, but the junior fellow argues that there is no evidence that transfusion improves outcome and that it may potentially be harmful.

Search Strategy

Secondary (Cochrane Library) and primary (PubMed) sources were included in the search.
Secondary sources: Search strategy: (("Intensive Care" [MeSH]) OR ("Critical Care" [MeSH]) OR ("Critical Illness" [MeSH])) AND (("Blood Transfusion" [MeSH]) OR ("Erythrocyte Transfusion" [MeSH])) AND systematic: five references, not related to the question.
Primary sources: Search strategy: (("Intensive Care" [MeSH]) OR ("Critical Care" [MeSH]) OR ("Critical Illness" [MeSH])) AND (("Blood Transfusion" [MeSH]) OR ("Erythrocyte Transfusion" [MeSH])): 548 references, five relevant to the question.

Search Outcome

5 records

Relevant Paper(s)

Author, date and country Patient group Study type (level of evidence) Outcomes Key results Study Weaknesses
Vincent et al,
Adult ICU patients, n = 3534, transfused 1037, not transfused 2227Prospective, multicentre, observational study (level 2)MortalityRelative risk reduction (RRR) –99% (95% CI: –121 to –78%). Absolute risk reduction (ARR): –0.13 (–0.15 to 0.1) Number needed to harm (NNH): 8 (7 to 10)Study limited to adults. No data presented on complication rate. Significant association betweendegree of multi-organ failure (SOFA rate) and transfusion rates, favouring non transfusion rates
Corwin et al,
Adult ICU patients, n = 4892, transfused 2152, not transfused 2740Prospective, multicentre, observational study (level 2)Mortality and complicationsMortality: RRR –38% (–54 to –23%) ARR: –0.05 (–0.07 to –0.02) NNH: 20 (14 to 34)

Complications: RRR: –165% (–179 to –151%) ARR: –0.30 (–0.33 to –0.28) NNH: 3 (3 to 4)
Study limited to adults
Taylor et al,
Adult ICU patients, n = 2085, transfused 449, not transfused 1636Prospective, single centre observational study (level 2)Mortality and nosocomial infection rateMortality: RRR –116% (–156 to –75%). ARR: –0.12 (–0.16 to –0.08) NNH: 9 (6 to 13)

Infections: RRR: –131% (–188 to –73%) ARR: –0.08 (–0.11 to 0.04) NNH: 13 (9 to 23)
Study limited to adults
Hιbert et al,
Ventilated adult ICU patients, n = 713, restrictive transfusion strategy 357, liberal strategy 356Randomised Controlled Study (level 2)Duration of mechanical ventilationMean duration of ventilation:8.3±8.1 days in both groups (NS)Study limited to adults, not designed and underpowered for this question
Goodman et al,
Critically ill anaemic (Hb9 g/dl) children, n = 240, transfused 131, not transfused 109Retrospective, multicentre cohort analysis (level 2)Days of oxygen use, ventilator days, length of stayTransfusion group had a longer duration of supplemental oxygen use (8±10 days vs 4±7 days; p<0.001), longer mechanical ventilation (6±9 days vs 2±4 days; p<0.05), and longer ICU stay (9±10 days vs 6±9 days; p<0.001)Paediatric multicentre study, using a restrictive transfusion protocol with a threshold of 9 g/dl


Anaemia is common among critically ill patients and may have multiple causes. Historically, expert opinion was that haemoglobin (Hb) concentrations should be maintained at levels of at least 10 g/dl (6 mmol/l) to maintain oxygen delivery. Transfusion decisions tend to be driven by individual transfusion triggers rather than by specific physiological triggers or consensus. In paediatric ICU patients, reported transfusion frequencies range up to 30% (Wheldon). After careful review of the literature, we found that available reports do not advocate liberal transfusion of red blood cells in critically ill patients. Evidently, critically ill patients are at increased risk of death whether or not transfusions are prescribed. Three studies in adult patients, corrected for predicted risk of mortality, found transfusion to be an independent risk factor. Based on these three studies, the number needed to harm (for death) is 14 (95% CI: 12 to 17). There is also evidence suggesting that red blood cell transfusions are associated with complications including pulmonary oedema (Hιbert) and nosocomial infection (Taylor). So far, mortality data are limited to adult studies. In the absence of further data, the decision to transfuse critically ill paediatric patients should be individualised and restricted to patients with Hb levels 9 g/dl (5.6 mmol/l) or even lower.

Clinical Bottom Line

Blood cell transfusion is an independent risk factor for mortality in critically ill adult patients. (Grade B) Blood cell transfusion is an independent risk factor for morbidity, including nosocomial infection and pulmonary oedema, in critically ill adult patients. (Grade B) So far, mortality data are limited to adult studies. Given the significant negative effects on mortality and morbidity, there is no support for liberal red blood cell transfusion in critically ill paediatric patients. (Grade C)


  1. Vincent JL, Baron J, Reinhart K, et al. Anemia and blood transfusion in critically ill patients. JAMA 2002; 288 1499–1507.
  2. Corwin HL, Gettinger A, Pearl RG, et al. The CRIT study: anemia and blood transfusion in the critically ill. Crit Care Med 2004; 32 39–52.
  3. Taylor RW, O'Brien J, Trottier J, et al. Red blood cell transfusions and nosocomial infections in critically ill patients. Crit Care Med 2006; 34 2302–8.
  4. Hιbert PC, Blajchman MA, Cook DJ, et al. Do blood transfusions improve outcomes related to mechanical ventilation? Chest 2001; 119 1850–7.
  5. Goodman AM, Pollack MM, Patel KM, et al. Pediatric red blood cell transfusions increase resource use J Pediatr 2003; 142 123–7.
  6. Weldon BC, Conner D, Walther WJ. Red blood cell transfusion practice in critically ill children Anesthesiology 2004; 101 A1468.