Sabtu, 31 Maret 2012

Guidelines Define Hemoglobin Levels for Transfusion

Red blood cell (RBC) transfusions in most hospitalized patients should be performed based on "restrictive," rather than "liberal," hemoglobin levels (7 - 8 g/dL), according to new clinical guidelines from the American Association of Blood Banks (AABB).
The new guidelines are based on a systematic literature review and were formulated by a multinstitutional panel of 20 experts led by Jeffrey L. Carson, MD, from the University of Medicine and Dentistry of New Jersey–Robert Wood Johnson Medical School in New Brunswick, and were published online March 26 in the Annals of Internal Medicine.
"Many small trials have addressed the question of optimal use of RBC transfusions," Dr. Carson and colleagues write. "Recently, 2 additional trials were published that expanded by 30% the number of patients included in the evidence base of transfusion trials. Thus, it is timely to reexamine the data and provide guidance to the medical community," the authors write.
The new guidelines outline 4 major recommendations based on various levels of evidence. The authors conducted a systematic review of 19 randomized clinical trials (including 6264 patients) evaluating transfusion thresholds. Trials were published from 1950 to February 2011.
The first recommendation is adherence to a restrictive transfusion strategy (7 - 8 g/dL) in hospitalized, stable patients. This is classified as a "strong" recommendation based on high-quality evidence.
The second recommendation is that a restrictive strategy be used in hospitalized patients with preexisting cardiovascular disease with consideration of transfusion for patients with symptoms or a hemoglobin level of 8 g/dL or less. The authors describe this recommendation as "weak," with moderate-quality evidence.
The third recommendation is that the AABB cannot recommend either for or against a liberal or restrictive transfusion threshold for hospitalized, hemodynamically stable patients with acute coronary syndrome. The panel classified this as an uncertain recommendation, with very low-quality evidence.
The fourth recommendation is that transfusion decisions should be influenced by symptoms as well as hemoglobin concentration, although again, this was a weak recommendation with low-quality evidence.
According to the panelists, other guidelines have proposed that transfusion is generally not indicated when the hemoglobin concentration is above 10 g/dL, but is indicated when it is less than 6 to 7 g/dL. "However, none of these guidelines recommended a specific transfusion trigger," they write.
"[I]n the current guidelines we explicitly used an evidence-based process that employed the [Grading of Recommendations Assessment, Development, and Evaluation (GRADE)] method," the authors note. "Although individual clinical factors are important, hemoglobin level is one of the critical elements used daily by physicians in the decision to transfuse. Thus, specific evidence-based recommendations on use of hemoglobin levels will help standardize transfusion practice," they conclude.
Transfusing Based on Hemoglobin Levels Alone "Insufficient"
In a related editorial, Jean-Louis Vincent, MD, from the Department of Intensive Care, Erasme Hospital, Universit√© libre de Bruxelles, Belgium, points out that "basing the decision to transfuse only on hemoglobin levels is insufficient."
He adds that he does "not believe that available evidence supports a fixed transfusion trigger. Rather, transfusion decisions need to consider individual patient characteristics, including age and the presence of [coronary artery disease], to estimate a specific patient's likelihood of benefit from transfusion."
He concludes, "The decision to transfuse is too complex and important to be based guided by a single number."
Support for the development of the guidelines was provided by the AABB in Bethesda, Maryland. Dr. Carson reports having a grant or grants pending from Amgen. Conflict-of-interest information for all authors is available on the journal's Web site. Dr. Vincent has disclosed no relevant financial relationships.

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