Monday, March 25, 2019

Growing evidence challenges conservative transfusion dogma

The last few years have seen quite a push toward restrictive transfusion strategies with conservative hemoglobin (less than seven) triggers.  Not only did numerous research publications support such an approach but there are important theoretical concerns. For example banked blood is relatively ineffective in terms of oxygen delivery due to depletion of 2, 3 DPG levels. There's also a concern based on indirect evidence that blood transfusions may be immunosuppressive by poorly understand mechanisms. Guidelines support a conservative (hemoglobin seven) trigger in almost all situations (though allowing room for clinical judgment which might favor a trigger of 8 in some circumstances).
In recent years the discussion around transfusion restriction has morphed into a campaign of sorts with conservative triggers embedded into electronic medical records and institutional policies taking the form of dogma with little regard for clinical judgment or the unique attributes of certain patients.

A paper in Critical Care Medicine challenges this dogma in certain patients:

Patients: Adult cancer patients with septic shock in the first 6 hours of ICU admission.

Interventions: Patients were randomized to the liberal (hemoglobin threshold, less than 9g/dL) or to the restrictive strategy (hemoglobin threshold, less than 7g/dL) of RBC transfusion during ICU stay.

Measurements and Main Results: Patients were randomized to the liberal (n = 149) or to the restrictive transfusion strategy (n = 151) group. Patients in the liberal group received more RBC units than patients in the restrictive group (1 [0-3] vs 0 [0-2] unit; p less than 0.001). At 28 days after randomization, mortality rate in the liberal group (primary endpoint of the study) was 45% (67 patients) versus 56% (84 patients) in the restrictive group (hazard ratio, 0.74; 95% CI, 0.53-1.04; p = 0.08) with no differences in ICU and hospital length of stay. At 90 days after randomization, mortality rate in the liberal group was lower (59% vs 70%) than in the restrictive group (hazard ratio, 0.72; 95% CI, 0.53-0.97; p = 0.03).

Conclusions: We observed a survival trend favoring a liberal transfusion strategy in patients with septic shock when compared with the restrictive strategy. These results went in the opposite direction of the a priori hypothesis and of other trials in the field and need to be confirmed.
Although the survival advantage for more aggressive transfusion did not reach statistical significance 28 days it did at 90 days.

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