Hemoglobin Levels for Transfusion

From Medscape Education Clinical Briefs

New AABB Guidelines State Specific Hemoglobin Levels for Transfusion CME/CE

News Author: Emma Hitt, PhD
CME Author: Laurie Barclay, MD

 Faculty and Disclosures

CME/CE Released: 03/29/2012; Valid for credit through 03/29/2013

 
 
 

CLINICAL CONTEXT

Worldwide, approximately 85 million units of red blood cells (RBCs) are transfused each year. However, there is great variation in transfusion practices.

The purpose of this guideline from the AABB (formerly, the American Association of Blood Banks) was to offer clinical recommendations regarding criteria for RBC transfusions in hemodynamically stable adults and children. These criteria include hemoglobin concentration thresholds and other clinical variables.

STUDY SYNOPSIS AND PERSPECTIVE

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 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, Université 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.

Ann Intern MedPublished online March 26, 2012Editorial full text

Related Link 
The Royal College of Nursing in the United Kingdom provides guidance for the nursing care of patients receiving transfusions. Right blood, right patient, right time is available online.

STUDY HIGHLIGHTS

 

  • The guidelines were based on a systematic literature review without language restrictions from 1950 to February 2011.
  • Criteria for inclusion were randomized clinical trials assessing transfusion thresholds.
  • To evaluate the effect of restrictive transfusion strategies on RBC use, a 20-member panel of experts analyzed the proportion of patients who received any RBC transfusion and the number of RBC units transfused.
  • The reviewers evaluated outcomes associated with restrictive transfusion strategies, including overall mortality, nonfatal myocardial infarction, cardiac events, pulmonary edema, stroke, thromboembolism, renal failure, infection, hemorrhage, mental confusion, functional recovery, and length of hospital stay.
  • For hospitalized, stable adults and children, the AABB recommends adhering to a restrictive transfusion strategy (hemoglobin threshold of 7 – 8 g/dL).
  • This is a strong recommendation based on high-quality evidence, because the evidence showed that patients receiving transfusion with a liberal strategy or a restrictive strategy had no difference in mortality, independent ambulation, or length of hospital stay.
  • However, the reviewers note that clinical judgment is critical and that individual patient characteristics may affect clinicians’ decisions to transfuse above or below the specified hemoglobin threshold.
  • For hospitalized patients with preexisting cardiovascular disease, the AABB suggests adhering to a restrictive strategy but considering transfusion for patients with symptoms of anemia or for those with a hemoglobin level of 8 g/dL or less.
  • However, this was a weak recommendation based on moderate-quality evidence, because there was some uncertainty about the risk for perioperative myocardial infarction associated with this strategy.
  • For hospitalized, hemodynamically stable patients with acute coronary syndrome, the AABB could not recommend for or against a liberal or restrictive transfusion threshold (grade: uncertain recommendation; very low-quality evidence).
  • Overall, the AABB suggests that the presence or absence of symptoms of anemia, as well as hemoglobin concentration, should influence transfusion decisions (grade: weak recommendation; low-quality evidence).
  • The panel found insufficient evidence to recommend a liberal or restrictive transfusion strategy for patients with acute coronary syndrome.

 

CLINICAL IMPLICATIONS

  • A new AABB guideline recommends a restrictive transfusion strategy (hemoglobin threshold of 7 – 8 g/dL) for hospitalized, hemodynamically stable patients. The underlying evidence shows no difference in mortality, independent ambulation, or length of hospital stay for patients receiving transfusion with a liberal strategy or a restrictive strategy.
  • For hospitalized patients with preexisting cardiovascular disease, the AABB suggests adhering to a restrictive strategy but considering transfusion for patients with symptoms of anemia or for those with a hemoglobin level of 8 g/dL or less. However, this was a weak recommendation, and some uncertainty exists about the risk for perioperative myocardial infarction associated with this strategy.
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