Massive Blood Transfusion (MBT) Protocol and Complications

DEFINITION

• Transfusion of ≥10 units of packed red blood cells (PRBCs) within 24 hours, OR
• Replacement of 1 complete blood volume within 24 hours, OR
• Ongoing blood loss of ≥150 mL/minute

MASSIVE TRANSFUSION PROTOCOL (MTP)

Goals of MTP

1. Prevent/treat hypovolemic shock
2. Maintain adequate oxygen-carrying capacity
3. Maintain oncotic pressure
4. Correct and prevent coagulopathy
5. Avoid the "lethal triad": Hypothermia + Acidosis + Coagulopathy

Blood Component Ratios

• The PROPPR trial (landmark RCT) compared 1:1:1 vs 2:1:1 (PRBCs:FFP:Platelets). No mortality difference at 24 hours or 30 days, but fewer patients in the 1:1:1 group died of exsanguination at 24 hours.
• Current recommendation: 1:1:1 ratio until evidence supports otherwise.
• Minimize crystalloids to <1 L to avoid dilutional coagulopathy.

Initial Management Steps

1. Large-bore IV access - two peripheral IVs (14-16 gauge) or wide-bore central access
2. Activate MTP - notify blood bank immediately
3. Tranexamic acid (TXA) - 2g IV bolus as soon as possible (especially in trauma); significantly reduces mortality when given early
4. O-negative uncrossmatched blood - if group unknown; switch to group-specific as soon as possible; Rh(D)-negative preferred in females of childbearing potential
5. Warm all blood products - use in-line fluid warmers; target temperature >35°C
6. Target parameters:
   • Hb 70-90 g/L
   • INR <1.8
   • Platelets >50 × 10⁹/L
   • Fibrinogen >1.5 g/L
   • Ionized Calcium >1.15 mmol/L
7. Coagulation monitoring - PT, APTT, fibrinogen; TEG/ROTEM may guide goal-directed therapy
8. Cryoprecipitate - for fibrinogen replacement when fibrinogen <1.5 g/L
9. Cell salvage - useful in anticipated massive surgical blood loss
10. Damage Control Surgery - hemorrhage control before definitive repair

Laboratory-Driven vs Fixed-Ratio Approach

• Fixed ratio (empiric): Used during active bleeding when labs lag behind clinical reality
• Lab-driven (goal-directed): FFP if PT/APTT >1.5× normal; platelets if <50,000; used post-MTP stabilization
• TEG/ROTEM alters transfusion patterns but its superiority over standard coagulation tests remains under study

COMPLICATIONS OF MASSIVE BLOOD TRANSFUSION

1. Hypothermia

• Most common early complication
• Stored blood is at 4°C; large volumes cause core temperature drop
• Hypothermia reduces clotting factor activity and platelet function, worsening coagulopathy
• Management: Blood warmers, warming blankets, warm IV fluids, maintain core temp >35°C

2. Coagulopathy (Dilutional + Consumptive)

• Dilutional: Replacement of blood volume with PRBCs and crystalloid dilutes clotting factors and platelets
• Consumptive: DIC, burns, brain injury, sepsis, hyperthermia cause factor consumption
• Manifests as prolonged PT/APTT, low fibrinogen, thrombocytopenia, elevated D-dimers
• Management: FFP, platelets, cryoprecipitate guided by labs/TEG

3. Metabolic Acidosis

• Common from hypoperfusion and tissue hypoxia
• Citrate from banked blood bags (citrate-phosphate-dextrose-adenine solution) is normally metabolized by the liver to bicarbonate
• Rapid infusion or reduced hepatic perfusion overwhelms this pathway → worsening metabolic acidosis
• Sodium bicarbonate administration is not routinely recommended; optimize oxygen delivery instead

4. Hypocalcemia (Citrate Toxicity)

• Each blood bag contains ~3g citrate; a healthy adult metabolizes this in 5 minutes
• Hypoperfusion or hypothermia slows citrate metabolism → unmetabolized citrate chelates calcium and magnesium
• Results in hypocalcemia + hypomagnesemia
• Hypocalcemia causes myocardial depression (manifests earlier than coagulopathy)
• Hypotension not responding to fluids is a key sign
• Management: Calcium supplementation (IV calcium gluconate or calcium chloride) in most MBT cases

5. Hyperkalemia

• Stored blood undergoes hemolysis over time, releasing intracellular K⁺ into the storage medium
• Older blood has higher extracellular K⁺ levels
• Risk increases with rapid, large-volume transfusion and in renal impairment
• Can cause fatal cardiac arrhythmias

6. Transfusion-Related Acute Lung Injury (TRALI)

• See detailed 5-mark answer below

7. Transfusion-Associated Circulatory Overload (TACO)

• Volume overload leading to pulmonary edema
• Especially in patients with CHF, hypertension, or chronic kidney disease
• Key differentiator from TRALI: responds rapidly to diuretics, elevated BNP, elevated pulmonary capillary wedge pressure (PCWP)

8. Hemolytic Transfusion Reaction

• ABO mismatched transfusion is the most significant adverse event in emergencies - can be life-threatening
• Caused by errors in patient/sample identification
• Prevention: strict bedside identification checks before each unit

9. Disseminated Intravascular Coagulation (DIC)

• Systemic coagulation activation leading to simultaneous thrombosis and hemorrhage
• Triggered by tissue injury, shock, fat emboli
• Managed with FFP, cryoprecipitate, platelets; treat underlying cause

10. Metabolic Alkalosis (Late)

• Paradoxically, once liver perfusion is restored, the large citrate load is converted to bicarbonate
• Can result in late metabolic alkalosis

11. Immunosuppression / Infections

• Transfusion-related immunomodulation (TRIM) increases susceptibility to sepsis and nosocomial infections

12. Late Complications

• Respiratory failure / ARDS
• SIRS
• Sepsis
• Thrombotic complications

Post-MTP Monitoring

TRALI - 5 Marks Answer

Transfusion-Related Acute Lung Injury (TRALI)

Definition

• It is currently the most common cause of transfusion-related fatality
• Incidence: approximately 1 in 5,000 transfusions
• Causes ~15% of fatal transfusion reactions
• Mortality: 5-10% overall

Pathophysiology / Mechanism

• First hit (Recipient priming): The patient's pulmonary vasculature is already primed by systemic inflammatory conditions (surgery, sepsis, trauma, massive transfusion itself) → neutrophils are sequestered in the pulmonary microvasculature
• Second hit (Donor-derived): Transfused plasma containing anti-HLA class I antibodies, anti-HLA class II antibodies, or antigranulocyte antibodies targets recipient granulocytes → antibody-antigen interaction activates neutrophils → release of proteases, oxidants, and inflammatory mediators → capillary leak → non-cardiogenic pulmonary edema

Risk Factors

• Multiparous female donors (sensitized to HLA antigens through pregnancy) - highest risk donors
• Plasma-containing blood components pose the greatest risk: platelets > FFP > PRBCs

• Hematologic malignancy patients (induction chemotherapy)
• Cardiac bypass surgery
• Massive transfusion
• Sepsis, trauma

Diagnostic Criteria (Clinical Diagnosis - No Specific Confirmatory Test)

1. Acute onset - during transfusion or within 6 hours of completion
2. Hypoxemia - PaO₂/FiO₂ ratio <300 mmHg, or O₂ saturation <90% on room air
3. Bilateral pulmonary infiltrates on chest X-ray (bilateral "fluffy" opacities resembling pulmonary edema)
4. No pre-existing ALI before transfusion
5. No evidence of circulatory overload (PCWP not elevated, no response to diuretics)
6. No other competing cause of ALI

Clinical Presentation

• Tachypnea, dyspnea, cyanosis
• Fever (in ~75% of cases)
• Hypotension (vasodilatory, non-cardiogenic)
• Hypoxemia requiring supplemental oxygen
• Bilateral diffuse fluffy infiltrates on CXR within 6 hours of transfusion

Differential Diagnosis

Management

1. Immediately stop the transfusion - notify blood bank
2. Oxygen supplementation - high-flow O₂; intubation and mechanical ventilation if required (ARDS-like management: lung-protective ventilation with low tidal volumes 6 mL/kg)
3. Supportive care - vasopressors for hypotension
4. NO diuretics (unlike TACO - diuretics worsen hypotension in TRALI)
5. No specific antidote - treatment is purely supportive
6. Investigate donor plasma for anti-HLA/antigranulocyte antibodies
7. Defer multiparous female donors from plasma donation (preventive strategy)

Prevention

• Male-only plasma donation policies (significantly reduce TRALI incidence)
• Deferral of multiparous female plasma donors
• Leukoreduction of blood products
• Minimize unnecessary plasma-containing transfusions
• Solvent/detergent-treated pooled plasma reduces antibody concentration