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Massive Transfusion Protocol: The 1:1:1 Ratio, and the Diamond of Death | Anesthesia Clinical Concepts

Ten units of red cells in 24 hours. That was the old definition — arbitrary, borrowed because ten units approximates one adult blood volume. It never accounted for rate. A patient can lose half their volume in an hour and never reach ten units before they arrest. Massive transfusion is not a number. It is a physiology problem with a clock attached.

This episode covers the protocol from activation to deactivation — the ABC score, the 1:1:1 ratio, and what the PROPPR trial actually showed. Then the mechanism underneath: the lethal triad of hypothermia, acidosis, and coagulopathy, plus the fourth variable that turns a triad into a death spiral — ionized hypocalcemia from citrate. Viscoelastic testing, tranexamic acid, calcium, warming, and the team roles that decide outcomes.

Key Takeaways

• Massive transfusion is traditionally defined as 10 or more units of red cells in 24 hours. Modern practice favors dynamic criteria

• The ABC score uses four bedside variables — penetrating mechanism, positive FAST, systolic BP ≤90, heart rate ≥120. Two or more activates the protocol.

• Balanced resuscitation with a 1:1:1 ratio of plasma to platelets to red cells improves early hemorrhage control. The PROPPR trial showed no significant 24-hour mortality difference versus 1:1:2, but more patients in the 1:1:1 group achieved hemostasis and fewer died of exsanguination.

• The lethal triad — hypothermia, acidosis, and coagulopathy. Citrate is the fourth variable that creates the diamond. Every unit of blood carries citrate that binds ionized calcium. Hypothermia and hypoperfusion slow citrate metabolism, prolonging hypocalcemia and worsening coagulopathy.

• Transexamic acid works by blocking plasmin activation, preventing clot degradation rather than promoting clot formation.

• Rapid infusers warm and deliver 200–1,200 mL/min. Warming is not comfort — it is coagulation management.

Timestamps

00:00 — The falling wall

02:00 — 1:1:1 ratio

02:36 — The lethal triad and the diamond of death

03:33 — Calcium, Transexamic Acid, Cryoprecipitate

04:10 — The rediscovery of balance

05:05 — PROPPR Trial

05:31 — From Theory to Practice

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