10.3 Trauma Diamond
Key Takeaways
- The 2026 outline names the trauma diamond—hypothermia, acidosis, coagulopathy, and hypocalcemia—not the older three-part lethal triad.
- A cold cabin, wet clothes, and unwarmed blood create hypothermia that shuts down clotting enzymes and platelets.
- Shock lactate plus large-volume 0.9 percent sodium chloride plus hypoventilation drive acidosis; over-bagging steals preload and worsens the lactic load.
- Citrate in stored blood binds ionized calcium; give calcium with massive transfusion and stop pouring unneeded crystalloid.
- Prevention is the skill: warm cabin, patient, fluids, and blood; strip wet clothes; trend temperature; stop the bleed.
The August 2026 Certified Flight Registered Nurse (CFRN) outline names the trauma diamond, not the older lethal triad. Domain 3.A will not give you credit for stopping at three corners. The four are hypothermia, acidosis, coagulopathy, and hypocalcemia. They feed one another. Flight makes every corner easier to cause and harder to see.
From triad to diamond
For years, trauma teaching used the lethal triad: cold, acid, and blood that will not clot. That language is not wrong as history. It is incomplete as 2026 exam language. Stored blood is anticoagulated with citrate, which binds ionized calcium. Calcium is a clotting cofactor and a myocardial inotrope. A patient who is already cold and acidotic, then filled with citrated product, loses the calcium the clot needs. Board of Certification for Emergency Nursing (BCEN) wrote hypocalcemia into the diamond so you treat it as a primary problem, not a laboratory afterthought.
If a question stem says "lethal triad," recognize the old three. If it says "trauma diamond" or asks for the four flight-relevant derangements of clotting, include calcium. Do not waste time arguing nomenclature on the ramp; warm the patient, stop the bleed, hang blood, and replace calcium.
Why each corner happens in the aircraft
Hypothermia
Cabin air is cold. Rotor wash on a winter ramp is colder. Wet clothing, an open bay door, a 4 °C unit of blood, and a room-temperature crystalloid bag all steal heat. Coagulation enzymes slow as core temperature falls; platelet function fails. A "normal" international normalized ratio (INR) drawn in a warm lab does not describe the clot in a 34 °C patient. Vibration and packaging hide shivering. Treat a falling temperature as a coagulopathy you are causing.
Acidosis
Hypoperfusion makes lactic acid. Large-volume 0.9 percent sodium chloride (NaCl) adds hyperchloremic metabolic acidosis. Hypoventilation adds respiratory acid. Over-bagging does not blow off the diamond. Stacked breaths drop venous return, worsen shock, and leave a larger lactic load. Acidosis impairs thrombin generation and makes the heart less responsive to catecholamines. A bouncing end-tidal carbon dioxide (ETCO2) that you ignore while you squeeze the bag is part of this corner.
Coagulopathy
Bleeding consumes factors and platelets. Crystalloid dilutes what remains. Cold and acid prevent what is left from working. Traumatic endotheliopathy and hyperfibrinolysis add a biological coagulopathy on top of the dilutional one. A single hematocrit does not tell you whether the patient can clot. Tranexamic acid (TXA) given early (section 10.2) addresses fibrinolysis; it does not fix cold, acid, or missing calcium.
Hypocalcemia
Every unit of citrated blood binds calcium. The faster you transfuse, the faster ionized calcium falls. Hypocalcemia is a coagulopathy and a cause of hypotension that will not make sense if you only chase volume. Do not mix calcium in the same lumen as packed red blood cells (PRBCs).
| Corner | Flight cause | What you do |
|---|---|---|
| Hypothermia | Cold cabin, wet clothes, cold fluids and blood | Warm cabin, patient, fluids, and blood; strip wet clothes |
| Acidosis | Shock, chloride load, hypoventilation or over-bagging | Stop bleeding, give blood not salt water, ventilate without over-bagging |
| Coagulopathy | Dilution, cold, acid, consumption, fibrinolysis | Blood products, early TXA, keep the patient warm |
| Hypocalcemia | Citrate in stored blood | Give calcium with massive transfusion; recheck if you have a cartridge |
Prevention is the testable skill
You will not treat the diamond with one drug. You prevent it.
- Warm everything. Request cabin heat. Remove wet clothes before they ride along as a cold pack. Use blankets, a chemical warmer, and the in-line fluid warmer for crystalloid and blood. Never microwave a unit or bake it on the glare shield.
- Limit unneeded crystalloid. After the first bridging liters, more salt water is dilution. Blood is the hemorrhage fluid (Chapter 8). "Uncrossmatched crystalloid" on this exam means pouring volume that is not matched to the deficit—not a blood-bank typing problem.
- Give calcium with massive transfusion protocol (MTP) product. Program doses of calcium chloride or calcium gluconate belong next to the cooler, not after the last unit.
- Stop the bleeding. A tourniquet, a pack, and a binder do more for coagulopathy than another amp of buffer.
- Ventilate without over-bagging. Target a normal ETCO2 unless a brain-injury protocol says otherwise. Stacked breaths steal preload from an empty tank and worsen lactic acidosis. Do not under-ventilate into a respiratory acidosis either.
Serial temperature and the wet-clothes rule
Measure temperature more than once. A single forehead reading on the ramp is not a trend. Recheck after loading, after the first units, and before handoff. An esophageal probe in the intubated patient beats a skin sensor under a wet sheet. If the number is falling, treat the diamond; do not just chart it.
Wet clothes come off. This is heat transfer, not a dignity lecture. Cut them, drop them on the scene, and cover the patient. An open aircraft door during a long load is a hypothermia machine—stage the package, then close. A vacuum mattress on wet denim will refrigerate the pelvis for the entire hop.
The August 2026 Certified Flight Registered Nurse outline names the trauma diamond. Which four derangements belong in that diamond?
Why does massive transfusion worsen the fourth corner of the trauma diamond during a long rotor-wing leg?
Which bundle best prevents the trauma diamond during flight?