4. Red Cell Restrictive Transfusion Thresholds and Single-Unit Transfusion in Patient Blood Management

There is a large variation in the transfusion thresholds being followed in different countries and even between hospitals within a country. However, accumulating evidence has revealed that centres using a restrictive transfusion threshold (<7-8g/dl) and single-unit dosing have demonstrated safety and efficacy across diverse clinical settings, from stable medical patients to those undergoing surgery or intensive care.

Barr and co-workers investigated red blood cell transfusion practice in Northern Ireland in 2005 and still found a two-unit instead of single-unit transfusion practice in medical and surgery patients (n=1474) (Barr et al. Vox Sang 2010).

Table 1: Recent Studies Supporting Restrictive Transfusion Strategies

Table 2: Recent Studies Single unit Transfusion Strategies

Study	Population	Key Findings	Reference
Single-unit Transfusion Policy in Autologous Hematopoietic Stem cell Transplantation: Less is not worse (2024)	Patients with autologous stem cell transplantation	Single-unit transfusion policy reduces RBC utilization by 32% with no significant differences in clinical outcomes between 1-RBC and 2-RBC policies.	Marco-Ayala J et al. Single-Unit Transfusion Policy in Autologous Hematopoietic Stem Cell Transplantation: Less is Not Worse Transfus Med Rev. 2024
Significant reduction of red blood cell transfusion requirements by changing from a double-unit to a single-unit transfusion policy in patients receiving intensive chemotherapy or stem cell transplantation	Oncology patients receiving intensive chemotherapy or hematopoietic stem cell transplantation	Switching to single-unit policy reduced RBC use by 25% without adverse effects	Berger et al. Significant reduction of red blood cell transfusion requirements by changing from a double-unit to a single-unit transfusion policy in patients receiving intensive chemotherapy or stem cell transplantation Haematologica. 2012

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Latest Guidelines on Red Cell Transfusion

Multiple international bodies have updated their transfusion guidelines to reflect the growing consensus around restrictive and individualized strategies:

1. CHEST (2025): Recommends restrictive transfusion (Hb <7–8 g/dL) for most critically ill adults, including those with GI bleeding and post-cardiac surgery. Suggests caution in ACS patients (1).

2.AABB (2025): Endorses restrictive thresholds for stable medical and surgical patients, emphasizing clinical context over fixed numbers (2).

3. BSH/EISCM (2025): Advocates restrictive threshold of 75 g/L (7.5 g/dL) in ICU patients post-cardiac surgery, citing safety and resource optimization (3).

4. ANZSBT (2025): Supports single-unit transfusion and restrictive thresholds in non-bleeding patients, with emphasis on reassessment before additional units (4).

However, all these guidelines emphasize that transfusion should be based on symptoms, clinical context, and hemoglobin levels—not routine practice or fear of under-treatment.

Restrictive Thresholds across Patient Populations

In Non bleeding patients:

1. Chronic Stable Anemia (Non-Bleeding): In patients with chronic anemia (e.g., iron deficiency, renal disease), transfusion is rarely indicated unless symptomatic. Iron supplementation, erythropoiesis-stimulating agents, and nutritional correction are preferred over transfusion.
2. In Hospitalized stable patients: It is recommended that a restrictive transfusion strategy (transfusion at Hb below 7 to 8 g/dl) should be used. However, the decision to transfuse should take into consideration the underlying clinical condition of the patient.
3. In Hospitalized patients with pre-existing cardiovascular disease, using a Hb threshold of 8 g/dl is recommended. However, liberal transfusion may increase the risk of thrombosis. And the reality trial and meta-analyses suggest that restrictive strategies do not worsen outcomes in stable CVD (7).
4. In patients with acute coronary syndrome, there is not much evidence to support the restrictive transfusion strategy for these patients. In a recent AABB international clinical Practice guidelines, patients hospitalized with acute myocardial infarction (AMI), a liberal red blood cell transfusion strategy when hemoglobin falls below 10 g/dL is recommended. A restrictive threshold (7–8 g/dL) may increase mortality in AMI, making liberal transfusion the preferred approach despite low-certainty evidence. Decisions should be context-driven, considering comorbidities, symptoms, and individual risk profiles—not just hemoglobin levels. To reduce complications like volume overload, mitigation strategies are advised. Similarly, the CHEST (2025) study also offers a conditional recommendation against restrictive transfusion in ACS due to potential increased mortality risk (1,2).
5. Transfusion-Dependent Thalassemia: These patients require regular transfusions to maintain Hb >9–10.5 g/dL for growth and organ protection. Restrictive thresholds are not applicable in these patients. Transfusion is guided by pre-transfusion Hb and iron overload monitoring. An effective transfusion regimen should ensure normal growth and development, maintain adequate energy levels, and provide sufficient suppression of intra‑ and extramedullary hematopoiesis (5).

Bleeding Patients

1. Acute Blood Loss: In trauma or GI bleeding, Restrictive strategy (Hb <7 g/dL) shown to reduce rebleeding and mortality. Adoption of Liberal transfusion may worsen outcomes in these patients.
2. Perioperative Blood Loss: The transfusion threshold Hb <7–8 g/dL is recommended.
3. In general: it is advisable to use Single-unit transfusion followed by reassessment

Ultra-Restrictive Thresholds: Emerging Evidence

A 2025 Amsterdam UMC review advocates exploring Hb <5 g/dL thresholds in stable ICU patients, citing evidence from hemodilution studies, transfusion refusers, and select populations (burns, hematology) showing no increased organ ischemia or mortality at these levels, with potential for reduced transfusion volume/cost. While provocative, the authors call for feasibility trials and individualized assessment rather than immediate adoption, as larger RCTs remain needed.
This provocative study challenges the long-held 7 g/dL benchmark and opens doors for precision transfusion medicine. However, larger studies are needed to confirm these preliminary results.

Key Messages

• Restrictive transfusion thresholds and single-unit dosing are safe, effective, and resource-conscious strategies in most patient populations. 
• Restrictive transfusion does not lead to an increased rate in mortality, cardiac events, myocardial infarction, stroke, pneumonia, infections and thromboembolism when compared to liberal transfusion strategies in the majority of patients.
• Exceptions exist—such as ACS and transfusion-dependent conditions—but the overarching principle remains: transfuse less, reassess more, and individualize always.

Conclusions

1. Based on recent literature regarding transfusion thresholds and clinical transfusion guidelines, the following recommendations can be made:

• Restrictive transfusion threshold of haemoglobin level of 7 g/dL should be used for hemodynamically stable hospitalized adult patients, including critically ill patients. 
• Single-unit transfusion reduces complications and conserves blood
• Restrictive transfusion threshold of haemoglobin level of 8 g/dL should be used for those undergoing orthopaedic surgery, and those with underlying stable cardiovascular disease. 
• Patients admitted with an acute upper gastrointestinal bleed may have a mortality benefit from using a restrictive transfusion threshold of haemoglobin level of 7 g/dL.

2. There is insufficient evidence to recommend an optimal transfusion threshold in the following groups of patients:

• Acute coronary syndrome: The 2025 AABB international Clinical Practice Guidelines also suggest a liberal red cell transfusion (<10g/dl) for patients with acute Myocardial infarction. Of note, this paper included the MINT trial (2023), that evaluated restrictive (Hb ≤8 g/dL) versus liberal (≤10 g/dL) transfusion strategies in patients with acute myocardial infarction and anemia, and was the largest study included in the meta-analysis. In this RCT, a liberal strategy showed a non-significant trend toward lower 30-day death or nonfatal MI, but failed superiority; at 6 months, cardiac mortality was higher with restrictive. Recommendations favour caution with restrictive thresholds in this group, considering potential harm signals favouring liberal transfusion
• Chronic transfusion-dependent anaemia (cancer, haematological malignancies, bone marrow failure)
• Acute neurologic disorders such as stroke and traumatic brain injury

Together, these strategies align with the goals of PBM: improve outcomes, reduce harm, and steward blood wisely.

References

1. American College of Chest Physicians. Guideline on Red Blood Cell Transfusion. CHEST. 2025. 
2. Pagano MB, et al. Red Cell Transfusion in Acute Myocardial Infarction: AABB International Clinical Practice Guidelines. Ann Intern Med.2025;178(10). doi:10.7326/ANNALS-25-00706.
3. BSH position paper on the ESICM guideline: Transfusion strategies in non-bleeding critically ill adults.2025.    
4. Australian New Zealand Society of Blood Transfusion (ANZSBT). Guidelines for the administration of blood products. 3rd ed. Sydney: ANZSBT; 2018 (revised October 2019, minor revision February 2024).
5. Taher AT, Farmakis D, Porter J, et al. 2021 Thalassaemia International Federation guidelines for the management of transfusion-dependent thalassemia. Hemasphere. 2021;5(8):e595.
6. Schaap CM, Klanderman RB, van der Sluijs GM, et al. Ultra-restrictive transfusion thresholds in critically ill adults: are we ready for the next step? Transfus Med Rev. 2025;39(2):150893
7. Carson JL, Brooks MM, Hébert PC, et al. Restrictive or liberal transfusion strategy in myocardial infarction and anemia. N Engl J Med. 2023;389(26):2446–56. 
8. Holst LB, et al. Lower versus Higher Hemoglobin Threshold for Transfusion in septic Shock.N Engl J Med. 2014;371:1381-1391.
9. Berger MD, et al. Significant reduction of red blood cell transfusion requirements by changing from a double-unit to a single-unit transfusion policy in patients receiving intensive chemotherapy or stem cell transplantation. Haematologica. 2012;97:116–22. 

The authors

The original version was created by Cynthia So-Osman. The current version was revised by Lakhvinder Singh.

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