How should I transfuse blood in aliquots?

How to Transfuse Blood in Aliquots

Red blood cells should be transfused one unit at a time as aliquots, with the patient's hemoglobin checked before each subsequent unit is administered, unless there is ongoing active bleeding or a large deficit requiring urgent correction. 1

Core Principle of Aliquot Transfusion

The fundamental approach to transfusing blood in aliquots is to avoid administering multiple units simultaneously without reassessment. This single-unit strategy allows for:

• Individualized dosing based on patient response rather than arbitrary protocols 1
• Prevention of over-transfusion and its associated complications 1
• Real-time assessment of therapeutic effect before proceeding 1

Practical Implementation

Standard Aliquot Transfusion Protocol

For adults receiving packed red blood cells:

• Transfuse one unit (approximately 250-450 mL depending on the collection system) 1
• Check hemoglobin/hematocrit after each unit completes 1
• Reassess clinical need before ordering the next unit 1
• Document the clinical indication and response in the patient's notes 1

Pediatric Considerations

For small children, blood components should be prescribed by volume rather than number of units to allow more precise aliquot dosing appropriate to their smaller blood volumes 1. This prevents the administration of excessive volumes that could occur with standard adult unit sizes.

Timing and Storage Constraints

Critical Time Limits

Blood products have strict handling requirements that impact aliquot administration:

• Blood must be transfused within 4 hours of leaving controlled refrigeration 1
• Blood cannot be returned to stock if out of controlled temperature for >30 minutes 1
• If using validated transport boxes, blood may be returned within 2 hours if the box remains unopened 1

These constraints mean you cannot simply "pause" a transfusion and restart hours later—each aliquot must be completed within the 4-hour window or discarded.

Special Situation: Autologous Blood in Aliquots

When using autologous blood collected during acute normovolemic hemodilution, different rules apply:

• Blood removed during hemodilution must remain with the patient and should not be refrigerated 1
• May be kept up to 6 hours at room temperature in an insulated container 1
• Should be reinfused in theatre whenever possible 1
• Must be labeled "UNTESTED BLOOD: FOR AUTOLOGOUS USE ONLY" 1

Verification Process for Each Aliquot

Before administering each unit (aliquot), perform independent bedside verification:

• Scan or verify patient wristband identification 2
• Verify blood group compatibility on the unit label 1, 2
• Check donation/unit number matches the patient's cross-match 1, 2
• Visually inspect for leaks, discoloration, or clots 3
• Confirm pre-infusion checks equivalent to hospital standard procedures 1

This verification must occur for every single unit, not just the first one 1, 2.

Monitoring During Aliquot Administration

For each aliquot transfused:

• Monitor vital signs before, during, and after transfusion 3
• Stop immediately if signs of transfusion reaction appear (tachycardia, rash, dyspnea, hypotension, fever) 3
• Document the volume transfused and patient response in case notes 1

Exception: Massive Hemorrhage

The single-unit aliquot approach does not apply during massive hemorrhage, where:

• Multiple units may need to be transfused rapidly without checking hemoglobin between units 1
• Hemoglobin may remain falsely elevated due to inadequate fluid resuscitation and should not be the sole guide 3
• Additional indicators include elevated lactate, low pH, and low central venous saturation 3
• Massive transfusion protocols typically involve predetermined ratios of blood products rather than aliquot-by-aliquot assessment 1

Common Pitfalls to Avoid

Do not order multiple units simultaneously for non-emergent transfusions without a plan to reassess between units, as this leads to unnecessary transfusions and waste 1. The 2016 AAGBI guidelines explicitly recommend against this practice outside of massive hemorrhage scenarios 1.

Do not assume the initial hemoglobin deficit requires a fixed number of units—patient response varies, and one unit may be sufficient even when the initial hemoglobin suggests otherwise 1.