What is the hemoglobin (Hgb) transfusion threshold?

From the Guidelines

The hemoglobin (Hgb) transfusion threshold is generally 7 g/dL for most hospitalized, hemodynamically stable adult patients, including those in critical care, while a threshold of 8 g/dL is recommended for patients undergoing orthopedic or cardiac surgery and those with pre-existing cardiovascular disease. For patients with acute coronary syndrome, a higher threshold of 8-10 g/dL may be appropriate. These recommendations are based on multiple large randomized controlled trials, including the TRICC trial, FOCUS trial, and AABB guidelines, which have consistently shown that restrictive transfusion strategies (using lower Hgb thresholds) are as effective as liberal strategies (using higher thresholds) and may actually reduce mortality, cardiac events, infections, and pulmonary edema 1. The most recent study from 2019 suggests that a more liberal hemoglobin threshold for transfusion may be associated with a lower risk for cardiovascular events in patients with cardiovascular disease 1. However, individual clinical judgment remains important, as patients with active bleeding, hemodynamic instability, or severe symptoms of anemia may require transfusion at higher thresholds regardless of their Hgb level. Some key points to consider when making transfusion decisions include:

• The patient's clinical status and the presence of any underlying cardiovascular disease
• The severity of bleeding and the risk of cardiovascular events
• The potential benefits and risks of transfusion, including the risk of infectious and noninfectious complications. Overall, the decision to transfuse should be guided by individual patient factors, rather than a single hemoglobin threshold. The use of restrictive transfusion strategies has been shown to decrease exposure to RBC transfusions by an average of approximately 40% (RR, 0.61 [CI, 0.52 to 0.72]) 1. This would have a large effect on blood use and the risks for infectious and noninfectious complications of transfusion. In contrast to the guidelines discussed, the current guidelines explicitly used an evidence-based process that employed the GRADE method, allowing for specific recommendations about transfusion thresholds 1. The addition of new data from recently published clinical trials allowed for specific recommendations about transfusion thresholds, which will help standardize transfusion practice. The physiological basis for these thresholds relates to the body's ability to compensate for anemia through increased cardiac output and oxygen extraction, with most patients tolerating moderate anemia well. However, the evidence is not sufficient to make specific recommendations for patients with acute coronary syndrome, and further research is needed to determine the optimal transfusion threshold for these patients. In general, the use of restrictive transfusion strategies is recommended, as it has been shown to be as effective as liberal strategies and may actually reduce mortality, cardiac events, infections, and pulmonary edema. The decision to transfuse should be guided by individual patient factors, rather than a single hemoglobin threshold, and should take into account the patient's clinical status, the presence of any underlying cardiovascular disease, and the severity of bleeding. The most recent and highest quality study, which is from 2019, provides the best evidence for the recommended hemoglobin transfusion threshold 1. This study suggests that a more liberal hemoglobin threshold for transfusion may be associated with a lower risk for cardiovascular events in patients with cardiovascular disease. However, the study also notes that the effects of liberal versus restrictive transfusion strategies may differ among various subgroups, and that the optimal transfusion threshold may depend on other factors, including the patient's clinical status, the type and severity of cardiovascular disease, and the severity of bleeding. Overall, the evidence suggests that the use of restrictive transfusion strategies, with a hemoglobin threshold of 7 g/dL for most patients and 8 g/dL for patients with pre-existing cardiovascular disease, is the best approach, as it has been shown to be as effective as liberal strategies and may actually reduce mortality, cardiac events, infections, and pulmonary edema.

From the Research

Hgb Transfusion Threshold

The hgb transfusion threshold is a topic of ongoing research and debate. According to the study by 2, a restrictive RBC transfusion threshold of 7 g/dL is recommended for hospitalized adult patients who are hemodynamically stable, including critically ill patients. However, the study by 3 suggests that a liberal transfusion strategy may be associated with improved safety for hospitalized patients with stable cardiovascular disease and/or acute coronary syndromes.

Key Findings

• A restrictive RBC transfusion threshold of 7-8 g/dL is recommended for most hospitalized patients, including critically ill patients and those undergoing orthopedic surgery, cardiac surgery, and those with preexisting cardiovascular disease 2.
• A liberal transfusion strategy may be associated with improved safety for hospitalized patients with stable cardiovascular disease and/or acute coronary syndromes 3.
• Restrictive transfusion strategies reduced the risk of receiving at least one RBC transfusion by 41% across a broad range of clinical contexts, but did not increase or decrease the risk of 30-day mortality compared with liberal transfusion strategies 4.
• Transfusion at a hemoglobin threshold of <7.0 g/dL was not associated with improved organ dysfunction compared with no transfusion in critically ill patients 5.

Studies Supporting the Hgb Transfusion Threshold

• 2: Clinical Practice Guidelines From the AABB: Red Blood Cell Transfusion Thresholds and Storage.
• 4: Transfusion thresholds for guiding red blood cell transfusion.
• 5: Red Blood Cell Transfusion at a Hemoglobin Threshold of 7 g/dl in Critically Ill Patients: A Regression Discontinuity Study.

Limitations and Future Research

• The optimal hemoglobin threshold for RBC transfusion remains uncertain, and further research is needed to inform guidelines and clinical practice 2, 3, 4.
• The safety of restrictive transfusion thresholds for certain clinical subgroups, such as myocardial infarction, vascular surgery, and haematological malignancies, remains unclear 4.
• Future trials of transfusion therapy should determine common practices before study inception and incorporate them as a usual-care "control" comparator arm into the trial design 3.