“A Multicenter, Randomized, Controlled Clinical Trial of Transfusion Requirements in Critical Care”
N Engl J Med. 1999 Feb 11; 340(6): 409-417. [free full text]
Although intuitively a hemoglobin closer to normal physiologic concentration seems like it would be beneficial, the vast majority of the time in inpatient settings we use a hemoglobin concentration of >7g/dL as our threshold for transfusion in anemia. Historically, higher hemoglobin cutoffs were used, often aiming to keep Hgb >10g/dL. In 1999, the landmark TRICC trial was published showing no mortality benefit in the liberal transfusion strategy and even harm in certain subgroup analysis.
Inclusion: critically ill patients expected to be in ICU > 24h, Hgb ≤ 9g/dL within 72hr of ICU admission, and clinically euvolemic after fluid resuscitation
Exclusion criteria: age < 16, inability to receive blood products, active bleed, chronic anemia, pregnancy, brain death, consideration of withdrawal of care, and admission after routine cardiac procedure.
Intervention: liberal strategy (transfuse to Hgb goal 10-12g/dL, N=420)
Comparison: restrictive strategy (transfuse to Hgb goal 7-9g/dL, N=418)
Primary outcome: 30-day all-cause mortality
Secondary outcomes: 60-day all-cause mortality, mortality during hospital stay (ICU plus step-down), multiple-organ dysfunction score, change in organ dysfunction from baseline
Subgroup analyses: patients with APACHE II score ≤ 20 (i.e. less-ill patients), patients younger than 55, cardiac disease, severe infection/septic shock, and trauma
The primary outcome of 30-day mortality was similar between the two groups (18.7% vs. 23.3%, p = 0.11). Secondary outcomes of mortality rates during hospitalization were lower in the restrictive strategy (22.2% vs. 28.1%, p = 0.05). 60-day all-cause mortality trended towards lower in the restrictive strategy although did not reach statistical significance (22.7% vs. 26.5 %, p = 0.23). Between the two groups there was no significant difference in multiple-organ dysfunction score or change in organ dysfunction from baseline.
Subgroup analysis was most notable for finding statistically significant benefits for the restrictive strategy in the patients with APACHE II score ≤ 20 and patients younger than 55. In these patients, a restrictive strategy showed decrease in 30-day mortality and a lower multiple-organ dysfunction score. In the subgroups of primary disease process (i.e. cardiac disease, severe infection/septic shock, and trauma) there was no significant difference.
Complications in the ICU were monitored, and there was a significant increase in cardiac events (primarily pulmonary edema) in the liberal strategy compared to the restrictive strategy.
TRICC showed no difference in 30-day mortality between a restrictive and liberal transfusion strategy. Secondary outcomes were notable for a decrease in inpatient mortality with the restrictive strategy. Furthermore, subgroup analysis showed benefit in various metrics for a restrictive transfusion strategy when adjusting for younger and less-ill patients. This evidence laid the groundwork for our current standard of transfusing to hemoglobin >7g/dL. A restrictive strategy has also been supported by more recent studies. In 2014 the Transfusion Thresholds in Septic Shock (TRISS) study showed no change in 90-day mortality with a restrictive strategy. Additionally, in 2013 the Transfusion Strategy for Acute Upper Gastrointestinal Bleeding study showed reduced 40-day mortality in the restrictive strategy. However, it excluded patients who had massive exsanguination or low rebleeding risk, thus making it difficult to generalize to our patient population. Currently, the Surviving Sepsis Campaign endorses only transfusing RBCs when Hgb <7g/dL unless there are extenuating circumstances such as MI, severe hypoxemia, or active hemorrhage.
References and Further reading:
1. TRISS @ Wiki Journal Club, full text, Georgetown Critical Care Top 40 pages 14-15
2. Transfusion strategy for acute upper gastrointestinal bleeding @ Wiki Journal Club, full text
3. “Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock 2016”
4. Wiki Journal Club
Summary by Gordon Pelegrin, MD