In a stable adult without active bleeding, is it appropriate to transfuse two units of packed red blood cells (PRBCs)?

Single-Unit Transfusion Strategy is Recommended Over Routine Two-Unit Transfusion

In stable adults without active bleeding, you should transfuse one unit of packed red blood cells at a time, followed by clinical and laboratory reassessment before considering additional units, rather than routinely transfusing two units. 1

The Evidence-Based Approach

Single-Unit Transfusion as Standard Practice

• Single-unit transfusion is the cornerstone of restrictive transfusion strategies and patient blood management programs, despite the absence of head-to-head randomized trials comparing one versus two units. 1

• This approach is included in the majority of current transfusion guidelines and represents expert consensus with strong agreement. 1

• The landmark TRICC trial and subsequent randomized trials evaluating transfusion thresholds all applied single-unit transfusion protocols, demonstrating no excess risk with this strategy. 1

Clinical Benefits of Single-Unit Strategy

Reduction in blood product utilization:

• In hematology critical care patients, single-unit transfusion reduced total units administered from 7.7 to 5.0 units per patient (P < 0.01) with no difference in morbidity or mortality. 1

• In hematological oncology patients, single-unit transfusion independently reduced transfusion requirements by 2.7 units per chemotherapy cycle. 1

• Implementation of patient blood management programs increased single-unit transfusion from 38% to 70.9% of cases, serving as an independent factor in reducing overall red blood cell utilization. 1

No increase in adverse outcomes:

• Multiple observational studies confirm that single-unit transfusion in hemodynamically stable anemic patients is not associated with excess risk. 1

Practical Implementation Algorithm

Step 1: Assess Clinical Stability

• Confirm the patient is hemodynamically stable without active bleeding. 2
• Document baseline vital signs (temperature, heart rate, blood pressure, respiratory rate) before transfusion. 2

Step 2: Transfuse Single Unit

• Administer one unit of packed red blood cells. 1, 2
• No mandatory time gap is required between units in stable patients—the decision is based on clinical reassessment, not arbitrary time intervals. 2

Step 3: Reassess After Each Unit

• Obtain complete blood count 10-60 minutes post-transfusion to verify hemoglobin response and accurately assess transfusion efficacy. 3
• Monitor vital signs at 15 minutes after starting transfusion and at completion. 2
• If hemoglobin increment is significantly less than expected, consider ongoing bleeding, hemolysis, or transfusion refractoriness. 3

Step 4: Decide on Additional Transfusion

• Base the decision to transfuse additional units on post-transfusion hemoglobin level and clinical symptoms, not on a predetermined two-unit order. 2
• Use restrictive transfusion thresholds: hemoglobin <7 g/dL for stable patients, <8 g/dL for cardiovascular disease or symptomatic anemia. 2

Critical Pitfalls to Avoid

Do not order two units simultaneously as standard practice:

• The traditional "two-unit" order is outdated and leads to unnecessary blood product utilization. 4
• Studies show that changing from routine two-unit to single-unit transfusion decreased two-unit transfusions from 65% to 43% (P < 0.001) with a 50% reduction in overall red cell usage. 4

Do not assume hemostatic blood counts without laboratory confirmation:

• Always verify hemoglobin response with post-transfusion laboratory testing rather than assuming adequate correction. 3

Do not transfuse based solely on hemoglobin numbers:

• Always incorporate the patient's symptoms, comorbidities, and clinical condition when deciding whether to transfuse. 5

When Two Units May Be Appropriate

The single-unit strategy applies specifically to stable patients without active bleeding. 1

Exceptions where rapid multi-unit transfusion is indicated:

• Massive transfusion protocols for active hemorrhage, where PRBCs are given rapidly in high ratios with plasma (at least 1:2 plasma:PRBC ratio) without gaps between units. 2
• Acute blood loss exceeding 30% of blood volume with hemodynamic instability. 6

Cost and Resource Implications

• A single institution implementing single-unit policy achieved unit cost savings of £28,670 over 6 months. 4
• Key to successful implementation is engagement from medical staff and support from hospital transfusion teams. 4