What is the difference between whole blood and Packed Red Blood Cells (PRBC)?

Difference Between Whole Blood and Packed Red Blood Cells (PRBCs)

Whole blood contains all blood components (red cells, plasma, platelets, and clotting factors) in their natural proportions, while PRBCs are concentrated red blood cells with most plasma removed, resulting in a higher hematocrit (approximately 70-80%) in a smaller volume.

Composition and Preparation

Whole Blood

• Contains red blood cells, plasma (with clotting factors and proteins), platelets, and white blood cells in physiologic ratios as collected from the donor 1
• Standard collection volume is 450 mL from a single donor 2
• Hematocrit remains at approximately 35-45% (physiologic levels) 1

Packed Red Blood Cells (PRBCs)

• Prepared by centrifugation of whole blood to separate and remove most of the plasma component 3
• Results in concentrated red cells with hematocrit of 70-80% in approximately 250-350 mL volume 1
• Contains minimal plasma, platelets, and clotting factors compared to whole blood 1
• Retains significant white blood cells (10^8 to 10^9 WBCs per unit) unless leukoreduced 2

Storage Requirements

Critical storage differences exist that directly impact clinical handling:

Whole Blood Storage

• Must be stored at 1-6°C (refrigerated) 4
• Can be stored for up to 35 days depending on anticoagulant-preservative solution used 1
• Develops storage lesion including increased hemolysis, oxidative stress, and microparticle formation over time 5

PRBC Storage

• Stored at 1-6°C (refrigerated) 4
• Storage duration identical to whole blood (up to 35-42 days depending on preservative) 1
• Exhibits similar storage lesion characteristics including hemolysis rates when normalized to RBC count, though absolute hemolysis products are lower due to reduced plasma volume 5

Clinical Applications and Outcomes

When Whole Blood May Be Preferred

• Massive hemorrhage protocols: The 1:1:1 ratio (FFP:platelets:PRBCs) attempts to replicate whole blood composition 4
• Recent trauma data shows whole blood transfusion results in significantly fewer total units transfused, reduced ARDS incidence, and fewer ventilator days compared to balanced component therapy, though mortality rates are equivalent 6
• Whole blood reduces the need for massive transfusion protocol activation 6

When PRBCs Are Standard

• Routine transfusion for anemia: PRBCs allow precise volume control and higher oxygen-carrying capacity per unit volume 1
• Component separation maximizes utility—one whole blood unit can be separated into PRBCs, platelets, plasma, and cryoprecipitate for multiple patients 1
• More cost-effective for blood inventory management in non-hemorrhagic scenarios 1

Practical Transfusion Considerations

Administration Differences

• Never transfuse platelets through tubing previously used for red cells (either whole blood or PRBCs) 4
• Both whole blood and PRBCs require separate IV lines if platelets are being administered simultaneously 4
• Infusion rates can be faster with PRBCs due to smaller volume for equivalent red cell mass 1

Volume and Dosing

• One unit of PRBCs contains the red cell mass of one unit of whole blood but in approximately half the volume 1
• For equivalent hemoglobin increase, PRBCs require less total volume infused, critical for patients with volume restrictions 1
• Whole blood provides approximately 450 mL volume per unit, which may contribute to volume resuscitation in hemorrhagic shock 6

Common Pitfalls to Avoid

• Do not assume whole blood provides adequate platelet support: Platelets in stored whole blood lose function rapidly and are not therapeutically effective beyond 24-48 hours of storage 2
• Do not use outdated transfusion triggers: Current evidence supports restrictive thresholds (hemoglobin <7 g/dL for most patients, <8 g/dL for cardiac disease) regardless of product type 7
• Do not overlook storage lesion effects: Both products develop increased free hemoglobin, oxidative stress, and impaired oxygen delivery with prolonged storage, though clinical significance remains debated 5
• Avoid fixating solely on hemoglobin numbers: Always incorporate patient symptoms, comorbidities, and ongoing bleeding when deciding to transfuse either product 7