Trauma: MTP & The Lethal Triad

What the Examiner Is Testing

This case tests whether you understand that rapid transfusion of blood products creates its own metabolic emergencies. The examiner specifically wants to see you identify hyperkalemia from banked pRBCs and respond systematically — calcium first, then insulin/dextrose, then hyperventilation — without missing the concurrent citrate toxicity causing ionized hypocalcemia.

The Board Trap

The trap is continuing to give more pRBCs when the EKG shows peaked T-waves and widening QRS. The same blood that's keeping the patient alive is causing a hyperkalemic cardiac emergency. You need to simultaneously treat the arrhythmia and investigate the cause, not just keep running the MTP.

Walk-Through: How This Case Plays Out

Examiner: EKG shows peaked T-waves and widening QRS. BP is 60/30. What's your immediate response?

Me: I'm treating this as hyperkalemia from banked blood immediately. Calcium chloride 1 gram IV right now to stabilize the cardiac membrane — that's the fastest intervention and it doesn't require a confirmed K+ level to start. I'm also stopping the pRBC transfusion temporarily. I'll get a STAT ABG with electrolytes simultaneously to confirm, but I'm not waiting for the result to start treatment.

Examiner: ABG comes back: K+ 7.8, pH 7.12, ionized calcium 0.6. What do you do with these results?

Me: Three problems. Hyperkalemia I'm already treating with calcium. Acidosis I'll address with sodium bicarbonate and hyperventilation — driving CO2 down creates a respiratory alkalosis that shifts K+ intracellularly. The ionized calcium of 0.6 is citrate toxicity — banked blood contains citrate as an anticoagulant, and when given rapidly, the liver can't metabolize it fast enough. I'd give additional calcium — a second gram of calcium chloride. I'd also check the temperature because hypothermia impairs citrate metabolism.

Examiner: What's the lethal triad and how do you address each component?

Me: Hypothermia, acidosis, and coagulopathy — each one worsens the other two. For hypothermia: warm all fluids, warm blankets, heated humidifier on the ventilator. For acidosis: bicarbonate, hyperventilation, and getting the hemodynamics stable so perfusion restores normal lactate clearance. For coagulopathy: TEG-guided products — cryoprecipitate for fibrinogen if below 1.5, platelets if the platelet amplitude is low on TEG. I'm not giving FFP blindly; I'm guiding every product by the TEG.

Examiner: The K+ is now 9.1 and the QRS is very wide. The BP is unrecordable. What do you do?

Me: This is a cardiac emergency. I've already given calcium and bicarbonate — I'd now give sodium bicarbonate 50-100 mEq as a bolus for cardiac stabilization in extreme hyperkalemia, along with 50 mL of 50% dextrose and 10 units of regular insulin. If the QRS widens further or he arrests, I follow ACLS. If he arrests, I'd consider that hyperkalemic arrest may benefit from double-dose epinephrine — there's some evidence for this. And I need to get him to dialysis if we can keep him alive long enough.

Key Phrases That Score Points

• "Calcium chloride first — I'm not waiting for the K+ level before stabilizing the cardiac membrane."
• "Citrate toxicity causes ionized hypocalcemia — check it after any large transfusion."
• "The lethal triad: hypothermia, acidosis, coagulopathy — treat all three simultaneously."
• "TEG guides my blood products, not empirical 1:1:1 after the first 10 units."
• "Stop the pRBC transfusion during the hyperkalemic crisis — the blood is contributing to the problem."

Why This Case Appears on the Boards

Massive transfusion complications test whether you understand that blood products are drugs with side effects. The ability to recognize hyperkalemia, citrate toxicity, and the lethal triad as distinct and treatable entities — and manage them concurrently — is exactly the ICU-level thinking examiners are looking for.