Therapy
A multicentere, randomized, controlled clinical trial of transfusion requirements in critical care.
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Summary
Posted By: Gordon S. Doig
E-Mail: gdoig@med.usyd.edu.au
Posted Date: March 6, 2003
Title: A multicentere, randomized, controlled clinical trial of transfusion requirements in critical care.
Authors: Hebert PC, Wells G, Blajchman MA, Marshall J et al
Reference: N Engl J Med 1999;340:409-417
Link: Click here for a direct link to the paper. A password may be required for access to fulltext.
Abstract: BACKGROUND: To determine whether a restrictive strategy of red-cell transfusion and a liberal strategy produced equivalent results in critically ill patients, we compared the rates of death from all causes at 30 days and the severity of organ dysfunction.
METHODS: We enrolled 838 critically ill patients with euvolemia after initial treatment who had hemoglobin concentrations of less than 9.0 g per deciliter within 72 hours after admission to the intensive care unit and randomly assigned 418 patients to a restrictive strategy of transfusion, in which red cells were transfused if the hemoglobin concentration dropped below 7.0 g per deciliter and hemoglobin concentrations were maintained at 7.0 to 9.0 g per deciliter, and 420 patients to a liberal strategy, in which transfusions were given when the hemoglobin concentration fell below 10.0 g per deciliter and hemoglobin concentrations were maintained at 10.0 to 12.0 g per deciliter.
RESULTS: Overall, 30-day mortality was similar in the two groups (18.7 percent vs. 23.3 percent, P= 0.11). However, the rates were significantly lower with the restrictive transfusion strategy among patients who were less acutely ill -- those with an Acute Physiology and Chronic Health Evaluation II score of < or =20 (8.7 percent in the restrictive-strategy group and 16.1 percent in the liberal-strategy group; P=0.03) -- and among patients who were less than 55 years of age (5.7 percent and 13.0 percent, respectively; P=0.02), but not among patients with clinically significant cardiac disease (20.5 percent and 22.9 percent, respectively; P=0.69). The mortality rate during hospitalization was significantly lower in the restrictive-strategy group (22.3 percent vs. 28.1 percent, P=0.05).
CONCLUSIONS: A restrictive strategy of red-cell transfusion is at least as effective as and possibly superior to a liberal transfusion strategy in critically ill patients, with the possible exception of patients with acute myocardial infarction and unstable angina.
 
Are the Results Valid?
1. Was the assignment of patients to treatments randomized?
Yes. The authors report using sealed opaque envelopes, distributed to each study center.
2. Were all patients who entered the trial properly accounted for and attributed at its conclusion?
2a. Was followup complete?
Yes. Of 838 patients who consented to randomization, 30 day mortality was available on all patients. At 60 days, mortality was available on all but 2 patients in the restrictive strategy group and 1 in the liberal strategy group.
2b. Were patients analyzed in the groups to which they were randomized?
Yes. A true intention to treat analysis was carried out. All patients were analyzed in the group to which they were originally randomzied.
3. Were patients, health workers, and study personnel blind to treatment?
No. Blinding was not possible.
4. Were the groups similar at the start of the trial?
There were no significant differences in any baseline characteristics.
5. Aside from the experimental intervention, were the groups treated equally?
Yes. The authors report that both groups were treated equally with regards to the use of vasoactive drugs, the administration of fluids, the use of PA catheters and the use of dialysis, mechanical ventilation and surgical procedures.
What are the Results?
1. How large was the treatment effect?
Primary outcome: 30 day mortality
  • 30 day mortality was 18.7% in the restricted transfusion group vs. 23.3% in the liberal transfusion group (p=0.11).
    Secondary outcomes:
  • Hospital discharge mortality was 22.2% in the restricted transfusion group vs. 28.1% in the liberal transfusion group (p=0.05).
  • There were no significant differences with regards to ICU LoS, hospital LoS, organ dysfucntion scores.
  • There were significantly more cardiac events (13.2% vs. 21.0%, p<0.01) in the liberal transfusion group compared to the restrictive transfusion group.
  • 2. How precise was the estimate of the treatment effect?
    Primary outcome: 30 day mortality
  • The 95% confidence interval surrounding the 4.6% decrease (p=0.11) in mortality in the restrictive transfusion group ranges from -0.84 to 10.2 %.
    Secondary outcome: Hospital mortality
  • The 95% confidence interval surrounding the 5.8% decrease (p=0.05) in mortality in the restrictive transfusion group ranges from 0 to 12%.
  • Will the Results Help Me In Caring For My Patients?
    1. Can the results be applied to my patient care?
    Yes. This paper enrolled a fairly representative patient population. Although a greater number of patients with cardiac disease did not enter the trial as compared to those who did enter the trial (26% of patients who were not enrolled vs. only 20% of patients who were enrolled, p<0.01), might suggest that these results may not generalize to patients with severe cardiac disease, however an a priori specified sub-group analysis failed to demonstrate any harm in this patient group.
    2. Were all clinically important outcomes considered?
    Yes. Although costs were not specifically recorded, restrictive transfusion did result in decreased blood product usage.
    3. Are the likely treatment benefits worth the potential harms and costs?
    Yes. Given that decreased exposure to blood products may even lead to improved clinical outcomes and decreased costs, the benefits do indeed appear to outweigh any potential harms. An evidence-based recommendation, which is the building block for an evidence-based guideline, that summarizes this topic can be found in the EBR section.

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