1. Principles of Damage Control Resuscitation

Damage control resuscitation (DCR) is a comprehensive strategy that combines early, balanced transfusion with antifibrinolytic therapy. The primary goal is to interrupt the vicious cycle of bleeding, which is classically described by the “lethal triad” of hypothermia, acidosis, and coagulopathy. More recently, this concept has evolved into the “lethal diamond,” incorporating hypocalcemia as a critical fourth component.

Historically, trauma resuscitation was dominated by large-volume crystalloid infusions, which often exacerbated coagulopathy and inflammation. Landmark clinical trials have driven a paradigm shift toward hemostatic resuscitation, using blood components in ratios that approximate whole blood. The PROPPR trial demonstrated that a 1:1:1 ratio of plasma, platelets, and packed red blood cells (RBCs) significantly reduced death from hemorrhage compared to a 1:1:2 ratio. Concurrently, the CRASH-2 trial established that early administration of tranexamic acid (TXA) within three hours of injury reduced all-cause mortality without increasing the risk of thrombotic events.

Key Points

• Initiate balanced component transfusion and TXA early (ideally within one hour, but no later than three hours post-injury) to mimic whole blood and mitigate premature clot breakdown (fibrinolysis).
• Proactively monitor and correct each component of the lethal diamond: maintain core temperature >35°C, correct acidosis (pH >7.25), and maintain ionized calcium levels ≥0.9 mmol/L.

2. Massive Transfusion Protocols (MTP)

Massive Transfusion Protocols (MTPs) are standardized, institution-specific systems designed to facilitate the rapid and coordinated delivery of blood products in fixed ratios. The primary purpose of an MTP is to stabilize a hemorrhaging patient by preemptively treating coagulopathy, minimizing delays, and preventing the over-transfusion of crystalloids or isolated RBCs.

Ratio-Based Therapy and Activation

Modern MTPs advocate for a ratio-based approach, aiming for a 1:1:1 balance of plasma, platelets, and RBCs. This strategy provides superior hemorrhage control and should be initiated as early as possible, ideally within 30 minutes of the patient’s arrival. Activation criteria are designed to identify patients at high risk for requiring massive transfusion and may include a combination of clinical and laboratory findings:

• Mechanism: Penetrating torso injury
• Hemodynamics: Systolic blood pressure (SBP) < 90 mm Hg; Heart rate (HR) > 120 bpm
• Metabolic State: Base deficit > 6 mEq/L
• Imaging: Positive Focused Assessment with Sonography for Trauma (FAST) exam
• Early Transfusion Need: Requirement of ≥4 units of RBCs within the first hour

Logistical Components

Effective MTPs rely on robust logistical support, including automated electronic alerts to the blood bank, pre-filled coolers with balanced components, readily available large-bore intravenous or intraosseous access, and dedicated equipment like blood warmers and rapid infusion devices.

3. Antifibrinolytic Therapy

Tranexamic acid (TXA) is a synthetic lysine analogue that acts as a potent antifibrinolytic agent. It functions by competitively blocking the lysine-binding sites on plasminogen, thereby preventing its conversion to plasmin. This action stabilizes existing fibrin clots and prevents their premature degradation, a condition known as hyperfibrinolysis, which is common after severe trauma.

Indications, Dosing, and Timing

Early administration of TXA is crucial for its efficacy in reducing death from bleeding. The standard dosing regimen is a 1-gram intravenous (IV) loading dose administered over 10 minutes, followed by a 1-gram infusion over the subsequent 8 hours.

• Optimal Window: The greatest benefit is observed when TXA is given within one hour of injury.
• Firm Cutoff: It should be administered no later than three hours post-injury, as later administration may be ineffective or potentially harmful.

Safety Profile

In major trauma populations, the use of TXA has not been associated with a significant increase in adverse thrombotic events such as myocardial infarction, stroke, deep vein thrombosis (DVT), or pulmonary embolism (PE). While caution is warranted in patients with a known high risk for thrombosis, routine dose reduction is not currently recommended.

4. Fibrinogen Replacement

Fibrinogen is a critical clotting factor that is often the first to be depleted to critically low levels during massive hemorrhage. Maintaining an adequate fibrinogen level is essential for forming stable clots. The therapeutic target during active bleeding is to maintain a plasma fibrinogen level of at least 100–150 mg/dL, with some guidelines advocating for a higher target of 200 mg/dL.

Replacement Options

• Cryoprecipitate: This is a pooled plasma product rich in fibrinogen, Factor VIII, Factor XIII, and von Willebrand factor. Each unit of cryoprecipitate typically raises the plasma fibrinogen level by approximately 5–10 mg/dL. A common starting dose is one unit per 5–10 kg of body weight.
• Fibrinogen Concentrate: This is a lyophilized, pathogen-reduced product that provides a standardized dose of fibrinogen in a low-volume formulation. It is typically available in 1-gram vials, and the dose is calculated based on weight (25–50 mg/kg).

Regardless of the product used, it is vital to recheck fibrinogen levels every 30–60 minutes during active, ongoing hemorrhage to guide further replacement therapy.

5. Factor and Anticoagulant Reversal

The presence of pre-existing anticoagulation significantly complicates the management of traumatic hemorrhage. Rapid reversal of these agents is a key component of DCR.

• 4-Factor Prothrombin Complex Concentrate (PCC): This is the agent of choice for reversing Vitamin K antagonists (e.g., warfarin). It provides a balanced concentration of factors II, VII, IX, and X in a small volume that can be infused quickly. The dose is typically 25–50 IU/kg based on the initial INR and patient weight. It may also be used as a second-line therapy for refractory coagulopathy in patients not on anticoagulants.
• Vitamin K: Should be co-administered (5–10 mg IV) with PCC for warfarin reversal to sustain factor synthesis.
• Direct Oral Anticoagulants (DOACs): Specific reversal agents should be used when available. These include idarucizumab for dabigatran and andexanet alfa for apixaban and rivaroxaban.
• Recombinant Factor VIIa (rFVIIa): This is considered a salvage therapy only due to its high cost and significant thrombotic risk. Its use should be reserved for life-threatening hemorrhage that is refractory to all other measures, and only after correcting hypothermia, acidosis, hypocalcemia, and thrombocytopenia.

6. Calcium and Metabolic Support

Hypocalcemia is a common and under-recognized component of the lethal diamond. Citrate, the anticoagulant used in stored blood products, chelates ionized calcium in the recipient’s circulation. Since ionized calcium is a necessary cofactor for multiple steps in the coagulation cascade and is essential for myocardial contractility, its depletion worsens both coagulopathy and shock.

Supplementation Strategy

The goal is to maintain an ionized calcium level of ≥0.9 mmol/L. This can be achieved through two main strategies:

• Empiric Regimen: Administer 1 gram of calcium chloride (10 mL of a 10% solution) or 3 grams of calcium gluconate after every 4 to 6 units of RBCs transfused.
• Guided Therapy: Use point-of-care blood gas analyzers to frequently measure ionized calcium and guide supplementation directly.

In addition to calcium, aggressive management of hypothermia with active warming measures and correction of metabolic acidosis are crucial to support the enzymatic function of the coagulation cascade.

7. Goal-Directed, Viscoelastic-Guided Therapy

While fixed-ratio MTPs are excellent for initial resuscitation, viscoelastic hemostatic assays (VHA) like Thromboelastography (TEG) and Rotational Thromboelastometry (ROTEM) offer a more sophisticated, goal-directed approach. These point-of-care tests provide a real-time, holistic assessment of the entire clotting process, from initiation and clot strengthening to fibrinolysis.

Interpreting Key Parameters

VHA allows clinicians to tailor transfusion therapy to the patient’s specific coagulopathic defect, moving beyond fixed ratios once the initial hemorrhage is controlled.

8. Special Populations and Dose Adjustments

While the core principles of DCR apply broadly, certain patient populations require specific considerations and dosing adjustments.

• Renal Replacement Therapy (RRT): Patients on RRT may have altered drug clearance and baseline coagulopathies. Use factor concentrates like fibrinogen and PCC with caution, and monitor clotting parameters and ionized calcium closely.
• Traumatic Brain Injury (TBI): Preventing hypotension and hypoxia is paramount. Early balanced transfusion is critical to maintain cerebral perfusion pressure. The role of TXA is of particular interest due to its potential to reduce intracranial hemorrhage expansion.
• Pediatrics: All dosing is strictly weight-based. Children have a smaller circulating blood volume and may require higher plasma-to-RBC ratios. Monitor vigilantly for signs of volume overload.

9. Pharmacoeconomics and Operational Considerations

Implementing a modern DCR program requires significant investment in products, equipment, and training. Understanding the relative costs is essential for resource allocation and protocol development. While viscoelastic testing involves an upfront cost for equipment, it can lead to overall savings by reducing the total number of blood products transfused.

Beyond product costs, operational readiness requires investment in rapid infusion pumps, blood warmers, and VHA consoles. Ensuring formulary access to factor concentrates and specific reversal agents is critical for accelerating care and improving outcomes.

10. Clinical Pearls and Pitfalls

Common Pitfalls to Avoid

• Over-transfusion: Failing to de-escalate the MTP when bleeding slows. Reassess the patient frequently (every 15–30 minutes) using clinical signs, hemoglobin, lactate, and VHA to guide termination of the protocol.
• Failure to Recognize Non-Responders: A patient with persistent hypotension, worsening base deficit, or persistent tachycardia despite aggressive resuscitation is a non-responder. This signals a need for prompt surgical or interventional radiology re-evaluation to find and control the source of bleeding.