Massive Transfusion Protocol Definition
Massive transfusion is conventionally defined as the administration of greater than 10 units of packed red blood cells within 24 hours, or alternatively, 4 or more units within 1 hour. 1
Standard Definitions in Clinical Practice
The European Society of Intensive Care Medicine establishes two primary definitions used across critical care settings 1:
- Traditional definition: >10 units of PRBCs transfused within 24 hours 1
- Acute definition: ≥4 units of PRBCs transfused within 1 hour 1
- Alternative acute threshold: ≥5 units within 4 hours, which better identifies patients at highest mortality risk 2
Clinical Context and Limitations
The 24-hour definition remains the most widely accepted conventional standard, though it has significant limitations in real-time clinical decision-making. 1
The acute timeframe definitions (1-hour or 4-hour) better capture the severity and urgency of hemorrhage, allowing earlier protocol activation 1, 2. The traditional 24-hour definition is retrospective by nature—patients must survive long enough to receive that volume, creating survivorship bias in observational studies 2.
Practical Activation Criteria
Modern massive transfusion protocols should be triggered by anticipated need rather than retrospective volume calculations. 2
Recommended activation parameters include 2:
- Systolic blood pressure <90-100 mmHg with signs of shock
- Lactate ≥5 mmol/L
- Base excess ≤-6
- Hemoglobin ≤9 g/dL
- Clinical evidence of uncontrolled hemorrhage requiring immediate intervention
Protocol Components
Once activated, massive transfusion protocols typically deliver 2:
- Blood product ratios: 1:1:1 to 1:1:2 (plasma:platelets:PRBCs), or at minimum 1:2 (plasma:PRBCs) 1, 2
- Standard packs: 3 PRBCs, 3 plasma units, 1 platelet unit per delivery round 2
- Rapid administration: No gaps between units during active massive hemorrhage 3
Common Pitfall
Do not wait to meet the retrospective definition of 10 units in 24 hours before activating the protocol—this delays life-saving intervention. 2 Activate based on hemodynamic instability, anticipated massive hemorrhage, and clinical parameters indicating shock, not on units already transfused. 2