Massive transfusion protocol — triggers, 1:1:1, TXA, calcium, ROTEM

Definition / Overview

Massive transfusion is conventionally defined as the requirement for $\geq 10$ units of packed red blood cells (PRBCs) within the first 24 hours of injury or haemorrhage. In operational terms, a more actionable definition is transfusion of $\geq 4$ units PRBCs in under 4 hours with ongoing haemorrhage. Massive transfusion protocol (MTP) is a pre-hospital-to-ICU system response that standardises the delivery of blood products in fixed haemostatic ratios, coordinates the blood bank and clinical teams, and ensures simultaneous haemostasis measures occur alongside resuscitation.

The FACEM leads MTP activation in the ED and must simultaneously:

• Identify the trigger and activate the protocol
• Designate a clinical contact responsible for blood bank communication
• Direct resuscitation in a damage-control framework
• Prevent the lethal triad of coagulopathy, acidosis and hypothermia

Pathophysiology: Acute Traumatic / Haemorrhagic Coagulopathy

Acute haemorrhagic coagulopathy is not simply dilutional; it begins at the moment of major tissue injury and shock. Key mechanisms include:

• Coagulation factor consumption: massive tissue factor exposure activates the extrinsic pathway; clotting factors are rapidly depleted
• Fibrinolysis: early trauma-induced fibrinolysis degrades formed clot within minutes; this is the target of tranexamic acid
• Platelet dysfunction: platelet function deteriorates rapidly after major trauma, independent of platelet count
• Hypothermia: enzymatic coagulation activity falls precipitously below $34^\circ\text{C}$; platelet aggregation is impaired below $33^\circ\text{C}$
• Acidosis: $\text{pH} < 7.2$ significantly impairs clotting factor activity
• Hypocalcaemia: citrate in stored PRBCs and FFP chelates ionised calcium ($\text{Ca}^{2+}$), a critical cofactor for every step of the coagulation cascade

These factors are interdependent and self-amplifying. MTP addresses all of them concurrently.

Triggers for MTP Activation

Clinical Gestalt

The bedside impression of a patient with uncontrolled haemorrhage and haemodynamic instability is sufficient to activate MTP without waiting for laboratory confirmation. Time-to-blood-product delivery is the modifiable variable.

Shock Index (SI)

$$\text{SI} = \frac{\text{Heart Rate (bpm)}}{\text{Systolic BP (mmHg)}}$$

• $\text{SI} \geq 1.0$: suggests significant haemorrhage; consider MTP
• $\text{SI} \geq 1.4$: high probability of requiring massive transfusion; activate MTP

Assessment of Blood Consumption (ABC) Score

Each variable scores 1 point; total $\geq 2$ triggers MTP consideration with sensitivity 76-90%:

Critical Bleeding Clinical Criteria

MTP activation is appropriate when any of the following are present:

• Obvious uncontrolled external haemorrhage not responding to pressure
• Pelvic fracture with haemodynamic instability
• Penetrating torso or junctional injury with shock
• Major obstetric haemorrhage ($> 1000\,\text{mL}$ with ongoing bleeding, or any haemorrhage with haemodynamic instability)
• Ruptured AAA, oesophageal varices with active haemorrhage, or massive upper GI bleeding

Management: Stepwise ED MTP Leadership

Step 1: Immediate Priorities (First 5 Minutes)

1. Activate MTP by calling the blood bank directly; provide patient name, date of birth, MRN, sex, location, and the name of a single designated clinical contact
2. Designate roles: team leader (FACEM), clinical contact for blood bank, runner for product collection, airway officer, documentation officer
3. Establish access: two large-bore peripheral IV cannulae ($\geq 16$ G) or intraosseous if unable; consider early central access (femoral preferred in haemorrhage to avoid pneumothorax risk during resuscitation)
4. Send early bloods: group and screen, full blood count, coagulation panel (PT/INR, APTT, fibrinogen), EUC, LFTs, ionised calcium, ABG (including lactate, haematocrit, potassium)
5. Control external haemorrhage: direct pressure, tourniquets for extremity haemorrhage, pelvic binder for suspected pelvic fracture (applied at level of greater trochanters, not the iliac crests)

Step 2: Blood Product Strategy (1:1:1 Ratio)

The target is to replace shed whole blood by transfusing haemostatic blood: PRBCs for oxygen-carrying capacity, FFP for coagulation factors, and platelets for primary haemostasis.

$$\text{Target ratio: PRBC: FFP: Platelets} = 1:1:1$$

Practical delivery:

• Most Australian MTPs issue packs: 6 units PRBC: 4 units FFP: one 5-pack platelets per cycle
• Transfuse the first pack immediately upon arrival; do not wait for laboratory results
• The clinical contact calls the blood bank for the next pack before the current one is exhausted
• Use a pressure bag or rapid infuser; use a blood warmer on all lines

O-negative blood: Release immediately if type and screen not yet resulted. Transition to type-specific then fully cross-matched blood as soon as available. O-negative is a finite resource; in female patients of reproductive age, O-negative is mandatory to prevent Rh(D) sensitisation and haemolytic disease of the newborn.

Step 3: Tranexamic Acid (TXA)

Administer TXA as early as possible and always within 3 hours of injury or onset of haemorrhage.

• Dose: $1\,\text{g}$ IV over 10 minutes, then $1\,\text{g}$ IV over 8 hours
• TXA inhibits fibrinolysis by blocking plasminogen binding to fibrin; it does not form clot but prevents clot breakdown
• Benefit is time-critical: TXA administered after 3 hours confers no mortality benefit and may increase mortality
• TXA is indicated in trauma, major postpartum haemorrhage, and significant GI bleeding with haemodynamic compromise
• Do not delay TXA for laboratory confirmation of fibrinolysis

Step 4: Calcium Replacement

• Ionised hypocalcaemia is universal during massive transfusion due to citrate chelation
• Monitor ionised calcium after every 4 units of blood product
• Target ionised calcium $\geq 1.1\,\text{mmol/L}$; do not allow it to fall below $0.9\,\text{mmol/L}$
• Preferred agent: calcium chloride $10\%$ solution; $10\,\text{mL}$ (1 g) IV via central line or large peripheral vein over 5-10 minutes; repeat as needed guided by ionised calcium
• Calcium gluconate requires hepatic metabolism to liberate free calcium; it is less reliable in the context of haemorrhagic shock with hepatic hypoperfusion. Calcium chloride delivers three times more elemental calcium per volume
• Document each dose and the corresponding ionised calcium result

Step 5: Cryoprecipitate for Fibrinogen Replacement

• Fibrinogen is consumed early and heavily in major haemorrhage; it is also poorly represented in FFP
• Trigger: fibrinogen $< 1.5\,\text{g/L}$ in the context of active bleeding (do not wait for fibrinogen to fall below $1.0\,\text{g/L}$)
• Dose: two 5-packs of cryoprecipitate (10 units); each unit contains approximately 250 mg fibrinogen, providing roughly 2.5 g total per 5-pack
• Cryoprecipitate also contains Factor VIII, von Willebrand factor, and Factor XIII

Step 6: Prevent and Manage the Lethal Triad

Hypothermia:

• Use an in-line blood warmer on all transfusion lines
• Apply forced-air warming blanket to the patient
• Warm IV crystalloid to $39^\circ\text{C}$ if required
• Target core temperature $\geq 35^\circ\text{C}$; monitor with rectal or oesophageal probe

Acidosis:

• The primary treatment is haemorrhage control and restoration of perfusion
• Avoid large-volume normal saline (hyperchloraemic acidosis); use balanced crystalloid (Hartmann's or Plasma-Lyte) for any crystalloid administered
• Sodium bicarbonate is not routinely indicated; address the cause (poor perfusion)

Coagulopathy:

• Addressed by 1:1:1 transfusion, TXA, calcium, and cryoprecipitate as above

Viscoelastic Testing: ROTEM and TEG

Rotational thromboelastometry (ROTEM) and thromboelastography (TEG) provide real-time, point-of-care assessment of the full coagulation sequence from clot initiation through fibrinolysis. Where available, these tests should guide targeted product replacement rather than relying solely on empirical 1:1:1 ratios.

Key clinical point: ROTEM/TEG detects hyperfibrinolysis earlier than standard coagulation tests. A pattern of maximum lysis in the absence of clot strength supports early TXA even before INR or APTT results are available. ROTEM/TEG also prevents unnecessary transfusion when coagulation is intact, reducing transfusion-related complications.

Haemorrhage Source Control

Resuscitation is not a substitute for haemostasis. Simultaneous activation of surgical, interventional radiology, and anaesthetic teams is a core leadership function of the FACEM.

• Pelvic fracture: apply pelvic binder immediately; activate IR for angioembolisation or prepare for pelvic packing in theatre
• Intra-abdominal haemorrhage: eFAST positive with haemodynamic instability unresponsive to two packs is an indication for emergency laparotomy; activate theatre and trauma surgery immediately
• Upper GI bleeding: urgent gastroscopy after stabilisation; consider balloon tamponade (Sengstaken-Blakemore tube) for variceal haemorrhage as temporising measure
• Obstetric haemorrhage: uterotonic therapy (oxytocin, ergometrine, carboprost, misoprostol), bimanual compression, Bakri balloon, surgical haemostasis

Monitoring During MTP

Repeat labs after every two MTP packs (or every 30-45 minutes of active resuscitation):

• Full blood count and platelets: target haemoglobin $\geq 70\,\text{g/L}$, platelets $\geq 50 \times 10^9/\text{L}$ (or $\geq 100 \times 10^9/\text{L}$ in traumatic brain injury or ophthalmic injury)
• Coagulation: target INR $\leq 1.5$, APTT $< 60\,\text{s}$
• Fibrinogen: target $\geq 1.5\,\text{g/L}$
• Ionised calcium: target $\geq 1.1\,\text{mmol/L}$
• ABG: lactate, pH, potassium (hyperkalaemia is a risk with rapid transfusion of stored red cells), haematocrit
• Temperature: continuous

Hyperkalaemia risk: stored PRBCs contain elevated extracellular potassium; monitor potassium every 30-60 minutes and treat hyperkalaemia ($K^+ > 5.5\,\text{mmol/L}$) with calcium, dextrose-insulin, and salbutamol as required.

MTP Deactivation

Deactivation is the FACEM's (or receiving team's) decision, and must be clearly communicated to the blood bank.

Criteria for deactivation:

• Haemorrhage controlled clinically and surgically
• Haemodynamic stability restored (MAP $> 65\,\text{mmHg}$, HR $< 100\,\text{bpm}$ without ongoing fluid boluses)
• Coagulation parameters normalising
• Lactate trending towards $< 2\,\text{mmol/L}$
• No further clinical or laboratory signs of ongoing haemorrhage

Deactivation process:

1. Notify blood bank immediately; return all unused blood products to the blood bank as soon as possible to preserve product viability for other patients
2. Switch to standard haematology orders guided by laboratory results
3. Document total product usage, clinical contact name, and time of deactivation
4. Brief handover to ICU or theatre team including cumulative volumes, current ionised calcium, temperature, and last coagulation results

Special Populations

Paediatric MTP

• Trigger: anticipated requirement of $> 40\,\text{mL/kg}$ blood products in 24 hours, or haemodynamic instability with ongoing haemorrhage
• All dosing is weight-based; maintain the 1:1:1 ratio
• O-negative blood is mandatory for all paediatric patients and all female patients of reproductive age
• Hypothermia risk is higher due to increased surface-area-to-body-mass ratio; aggressive warming

Obstetric MTP (PPH)

• Trigger: blood loss $> 1000\,\text{mL}$ with ongoing haemorrhage, or any haemorrhage causing haemodynamic instability
• TXA 1 g IV over 10 minutes, repeated at 30 minutes if ongoing haemorrhage; must be given within 3 hours of delivery
• Fibrinogen falls early in PPH; target fibrinogen $\geq 2.0\,\text{g/L}$ in obstetric patients (higher threshold than trauma)

Anticoagulated Patients

• Warfarin: Prothrombin complex concentrate (PCC) preferred over FFP for urgent reversal (faster, lower volume); vitamin K $10\,\text{mg}$ IV concurrently for sustained effect
• Direct oral anticoagulants (DOACs): specific reversal agents where available: idarucizumab for dabigatran; andexanet alfa for factor Xa inhibitors (apixaban, rivaroxaban); PCC as second-line
• Heparin: protamine $1\,\text{mg}$ per $100\,\text{units}$ of heparin administered (consider timing; maximum dose $50\,\text{mg}$)

Complications of Massive Transfusion

Disposition

• All patients requiring MTP activation are resuscitation-bay patients
• Source control determines immediate disposition: theatre for surgical haemostasis, IR suite for angioembolisation, or ongoing ED resuscitation pending source control
• Post-haemorrhage control disposition: ICU for monitoring, ventilation, and correction of residual coagulopathy, hypothermia, and acidosis
• Clear, structured handover to the ICU team with: cumulative product volumes, current laboratory results, remaining coagulopathy burden, ongoing surgical plans, and active antibiotic or adjunctive therapy

Common Exam Errors to Avoid

• Missing TXA or giving it after 3 hours: TXA must be given early; document the time of injury on every MTP case
• Omitting calcium replacement: failure to replace calcium is common and potentially fatal; ionised calcium monitoring is mandatory
• Using normal saline as the crystalloid: this worsens hyperchloraemic acidosis; use Hartmann's or Plasma-Lyte
• Not returning unused products: deactivation includes product return to blood bank immediately
• Failing to apply a pelvic binder early: in pelvic fracture with haemorrhage, the binder is applied before CT, not after
• Not designating a single blood bank contact: MTP requires one named clinical contact; multiple callers cause dangerous confusion
• Delaying theatre or IR activation: the FACEM must simultaneously run resuscitation and activate the definitive haemostasis pathway; these are not sequential

Sources

• ACEM policy documents
• ANZCOR / ARC Resuscitation Guidelines
• ATLS (Advanced Trauma Life Support)