If the hemoglobin is <7 g/dL (70 g/L) for most patients (including those with stable coronary artery disease), with a goal of maintaining the hemoglobin at a level ≥7 g/dL (70 g/L)

Transfuse un-cossmatched type specific blood for hemodynamic instability despite crystalloid resuscitation if cross-match blood is unavailable.

For patients at increased risk of suffering adverse events in the setting of significant anemia, such as those with unstable coronary artery disease or elderly maintain the hemoglobin at a level of ≥9 g/dL (90 g/L)

Patients with active bleeding and hypovolemia require blood transfusion despite an apparently normal hemoglobin as intravascular blood has not had a chance to equilibrate with infused fluid or fluid has not moved by osmosis from the interstitum to the intravascular space to dilute the blood.

It is particularly important to avoid overtransfusion in patients with suspected variceal bleeding, as it can precipitate worsening of the bleeding. Transfusing patients with suspected variceal bleeding to a hemoglobin >10 g/dL (100 g/L) should be avoided.

●There is excellent clinical trial evidence that suggests that a restrictive policy of transfusion at a hemoglobin (Hgb) concentration of 7 to 8 g/dL should guide transfusion decisions in most patients. The use of transfusion thresholds that restrict transfusion to this Hgb concentration are safe in most patient populations, may improve clinical outcomes, and will reduce unnecessary transfusion.

 

●All patients should be assessed clinically when transfusion is considered. If the patient is stable, transfusion may not be needed even when the Hgb level is 7 to 8 g/dL.

 

●For patients in the intensive care unit, including those with septic shock, we recommend transfusion to maintain the Hgb at >7 g/dL rather than a higher threshold (Grade 1B); however there may be cases in which the patient is asymptomatic at a Hgb of 7 g/dL, and clinician judgment may support not administering a transfusion.

 

●For most medical and surgical patients who are hemodynamically stable, as well as ambulatory patients, we recommend blood transfusion to maintain the hemoglobin at ≥7 to 8 g/dL rather than 10 g/dL, with the threshold based on the value established as safe in the clinical trial that most closely resembles the patient (Grade 1B); however, there may be cases in which the patient is asymptomatic at a Hgb <8 g/dL, and clinician judgment may support not administering a transfusion.

---

Exceptions include the following:

 

•Symptomatic patients with Hgb <10 g/dL should be transfused to improve hemodynamic instability and symptoms of myocardial ischemia. (See 'Symptomatic patient' above.)

 

•For patients with acute coronary syndromes, we use an individualized approach. We transfuse when the Hgb is <8 g/dL; we consider transfusion when the Hgb is between 8 and 10 g/dL; and we maintain the Hgb ≥10 g/dL in the patient with symptoms or ongoing ischemia. In a stable, asymptomatic patient, it is unknown when to transfuse, although we tend to maintain a higher Hgb level based on evaluating the patient's symptoms and underlying condition. Other experts, including other authors for UpToDate, prefer a slightly lower Hgb threshold for transfusion in this population. (See 'Acute coronary syndrome' above and "Overview of the non-acute management of ST elevation myocardial infarction", section on 'Red cell transfusion' and "Overview of the non-acute management of unstable angina and non-ST elevation myocardial infarction", section on 'Red cell transfusion'.)

 

•Patients requiring massive transfusion (eg, from trauma or ongoing bleeding) often cannot be managed using Hgb thresholds. This issue is discussed separately. (See "Massive blood transfusion" and "Initial evaluation and management of shock in adult trauma", section on 'Transfusion of red blood cells'.)

 

●Transfusion may be appropriate in the palliative setting. Some hospice programs provide blood transfusion for comfort and symptom relief. (See 'Palliative care' above.)

 

●Transfusion of one unit of blood at a time is reasonable for hemodynamically stable patients, with assessment of symptoms immediately after transfusion and post-transfusion Hgb levels, which can be done as early as 15 minutes and as late as 24 hours after transfusion. (See 'Overview of our approach' above.)

 

●Hospital-wide patient blood management programs may be helpful in guiding transfusion practices and reducing unnecessary transfusions, but they should not supersede clinical judgment. (See 'Hospital-wide oversight programs' above.)

 

●Risks and complications of transfusion are discussed separately. (See 'Risks and complications of transfusion' above.)

---

 

No single criterion should be used as an indication for red cell component therapy, and that multiple factors related to the patient's clinical status and oxygen delivery needs should be considered.¹

In general, the different guidelines have recommended that transfusion is not indicated for Hgb >10 g/dL, but the lower threshold varies from 6 g/dL to 8 g/dL. As an example, the AABB guidelines (which we co-authored) include the following recommendations for hemodynamically stable patients without active bleeding [9]:

●Hgb <6 g/dL – Transfusion recommended except in exceptional circumstances

 

●Hgb 6 to 7 g/dL – Transfusion generally likely to be indicated

 

●Hgb 7 to 8 g/dL – Transfusion should be considered in postoperative surgical patients, including those with stable cardiovascular disease, after evaluating the patient’s clinical status

 

●Hgb 8 to 10 g/dL – Transfusion generally not indicated, but should be considered for some populations (eg, those with symptomatic anemia, ongoing bleeding, acute coronary syndrome with ischemia)

 

●Hgb >10 g/dL – Transfusion generally not indicated except in exceptional circumstances

 

The guidelines also emphasize that the decision to transfuse should not be based only on hemoglobin level but should incorporate individual patient characteristics and symptoms. Clinical judgment is critical in the decision to transfuse; therefore, transfusing RBCs above or below the specified hemoglobin threshold may be dictated by the clinical context. Similarly, the decision not to transfuse RBCs to a patient with a hemoglobin concentration below the recommended thresholds is also a matter of clinical judgment.²

The final decision to transfuse should incorporate the clinical status, co-morbidity, and the individual wishes of the patient.

For most patients, we prefer using a restrictive transfusion strategy (ie, giving less blood; transfusing at a lower Hgb level; and aiming for a lower target Hgb level) rather than a liberal transfusion strategy (ie, giving more blood; transfusing at a higher Hgb level). For most hemodynamically stable medical and surgical patients, we suggest considering transfusion at a Hgb of 7 to 8 g/dL, with the threshold based on the value established as safe in the clinical trial with the population that most closely resembles the patient. Some patients may tolerate a lower Hgb level

Assessment of the post-transfusion hemoglobin level can be performed as early as 15 minutes following transfusion, as long as the patient is not actively bleeding. This practice is based on studies showing a high degree of concordance between values measured 15 minutes after completion of the transfusion versus longer intervals [21,22].

Major exceptions to the use of a threshold of 7 to 8 g/dL include the following:

●Symptomatic patients may be transfused at higher Hgb levels to treat symptoms. (See 'Symptomatic patient' below.)

 

●Patients with acute coronary syndromes have not been adequately evaluated in clinical trials and may require higher thresholds for transfusion. (See 'Acute coronary syndrome' below.)

 

●Threshold-based transfusion is not appropriate for patients requiring massive transfusion, such as in the setting of trauma, because it requires waiting for Hgb levels to be reported. (See "Massive blood transfusion" and "Initial evaluation and management of shock in adult trauma", section on 'Transfusion of red blood cells'.)

 

Our goal of avoiding unnecessary transfusion also guides our practice of transfusing one unit of red blood cells at a time, rather than requesting multiple units, for a hemodynamically stable patient who is not actively bleeding [9]. Whenever possible, we also initiate or continue treatment of the underlying condition responsible for the anemia.

Our approach of considering a threshold Hgb of 7 or 8 g/dL for most patients is supported by a Cochrane systematic review and metaanalysis of clinical trials of red cell transfusion. The Cochrane review identified 19 randomized clinical trials comparing higher versus lower transfusion thresholds in a total of 6264 medical and surgical patients (adults and children) [23,24]. Trials were included if transfusion was administered on the basis a transfusion trigger, defined as a hemoglobin or hematocrit level below which a blood transfusion was to be given. Most trials compared outcomes in patients transfused at Hgb thresholds between 7 and 10 g/dL; specific thresholds differed for each trial. Compared with liberal transfusion strategies (higher thresholds), restrictive strategies (lower thresholds) resulted in the following [9,23]:

●A 39 percent decrease in the probability of receiving a transfusion (46 versus 84 percent; relative risk 0.61; 95% CI 0.52-0.72)

●Fewer units (1.19) transfused per patient

●A trend towards a lower 30-day mortality (relative risk = 0.85; 95% CI 0.70-1.03) (figure 1)

●A trend towards a lower overall infection rate (relative risk = 0.81; 95% CI 0.66-1.00); however, there was no difference seen with pneumonia.

●No difference in functional recovery, or hospital or intensive care length of stay

●No increased risk of myocardial infarction (MI) when all trials were included (relative risk = 0.88; 95% CI 0.38-2.04).

 

However, the two largest trials found opposite effects of a restrictive strategy on the risk of MI.

 

•In the Transfusion Requirements In Critical Care (TRICC) trial of adult intensive care unit patients, a restrictive transfusion strategy was associated with lower risk of MI (0.7 versus 2.9 percent; relative risk = 0.25; 95% CI 0.07-0.88). (See 'Intensive care unit/septic shock' below.)

 

•In patients undergoing hip fracture repair in the Functional Outcomes in Cardiovascular Patients Undergoing Surgical Hip Fracture Repair (FOCUS) trial, which was performed in patients with preexisting cardiovascular disease or risk factors, a restrictive transfusion strategy was associated with a non-statistically significant higher risk of MI (3.8 versus 2.3 percent; relative risk = 1.65; 95% CI 0.99-2.75). However, mortality was not adversely affected. (See 'Non-cardiac surgery' below.)

A blood group system consists of carbohydrate or protein red cell antigens produced by alleles of a single genetic locus or by closely linked alleles. Most blood group antigens stem from single nucleotide polymorphisms. For example, the S and s alleles of the glycophorin B gene differ by a single nucleotide polymorphism in codon 29, with the S allele encoding a methionine residue (ATG) and the s allele encoding a threonine residue (ACG). Most red cell antigens are proteins expressed on the cell surface, but some, most notably those of the ABO system, stem from differences in carbohydrates linked to surface proteins or glycolipids.

 

ABO blood group typing is determined by the presence or absence of A or B red blood cell (RBC) surface antigens: Type A blood has A RBC antigen, type B blood has B RBC antigen, type AB blood has both A and B RBC antigens, and type O blood has neither A nor B RBC antigen present.

Almost all individuals not having A or B antigen “naturally” produce antibodies, mainly immunoglobulin (Ig) M, against those missing antigens within the first year of life.

There are approximately 46 Rhesus group red cell surface antigens, and patients with the D Rhesus antigen are considered Rh-positive. Approximately 85% of the white population and 92% of the black population has the D antigen, and individuals lacking this antigen are called Rh-negative. In contrast to the ABO groups, Rh-negative patients usually develop antibodies against the D antigen only after an Rh-positive transfusion or with pregnancy, in the situation of an Rh-negative mother delivering an Rh-positive baby.

In 1492, as Pope Innocent VIII lapsed into a coma, the blood of three boys was infused—into his mouth! Considerable progress has been made since then, particularly following Karl Landsteiner's discovery of the ABO blood group antigens in 1901.

Autologous Transfusion

Patients undergoing elective surgical procedures with a high probability for transfusion can donate their own blood for use during that surgery. Collection is usually started 4-5 weeks prior to the procedure. The patient is allowed to donate a unit as long as the hematocrit is at least 34% or hemoglobin at least 11 g/dL. A minimum of 72 h is required between donations to make certain that plasma volume returns to normal. With iron supplementation and erythropoietin therapy, at least 3 or 4 units can usually be collected prior to operation. Some studies suggest that autologous blood transfusions do not adversely affect survival in patients undergoing operations for cancer. Although autologous transfusions likely reduce the risk of infection and transfusion reactions, they are not risk-free. Risks include those of immunological reactions due to clerical errors in collection, labeling, and administration; bacterial contamination; and improper storage. Allergic reactions can occur due to allergens (eg, ethylene oxide) that dissolve into the blood from collection and storage equipment.

Blood Salvage & Reinfusion

This technique is used widely during cardiac, major vascular, and orthopedic surgery (see Chapter 22). The shed blood is aspirated intraoperatively into a reservoir and mixed with heparin. After a sufficient amount of blood is collected, the red cells are concentrated and washed to remove debris and anticoagulant and then reinfused into the patient. The concentrates obtained usually have hematocrits of 50-60%. To be used effectively, this technique requires blood losses greater than 1000-1500 mL. Contraindications to blood salvage and reinfusion include septic contamination of the wound and perhaps malignancy. Newer, simpler systems allow reinfusion of shed blood without centrifugation.

Normovolemic Hemodilution

Acute normovolemic hemodilution relies on the premise that if the concentration of red cells is decreased, total red cell loss is reduced when large amounts of blood are shed; moreover, cardiac output remains normal because intravascular volume is maintained. One or two units of blood are typically removed just prior to surgery from a large-bore intravenous catheter and replaced with crystalloid and colloids so that the patient remains normovolemic but has a hematocrit of 21-25%. The blood that is removed is stored in a CPD bag at room temperature (up to 6 h) to preserve platelet function; the blood is given back to the patient after the blood loss or sooner if necessary.