1. Clinical Classification of Shock

Early bedside assessment using ATLS shock classes and the Shock Index expedites recognition of hemodynamic compromise. These tools provide a rapid, physiology-based framework for initial triage before laboratory data are available.

ATLS Classes of Hemorrhagic Shock

Limitations: It’s crucial to recognize that elderly patients, those on beta-blockers, or well-conditioned athletes may not manifest classic tachycardic responses. Compensatory mechanisms vary widely among individuals.

Shock Index (SI)

The Shock Index (SI), calculated as Heart Rate divided by Systolic Blood Pressure (HR/SBP), is a more sensitive marker of early shock than vital signs alone. An SI >0.9 suggests significant hemodynamic decompensation and correlates with higher transfusion requirements and mortality. Variants like the Modified SI (HR/MAP) and Age-Shock Index (Age x SI) further refine risk stratification.

2. Traditional Laboratory Markers

While clinical assessment is primary, laboratory markers quantify the extent of coagulopathy and shock. However, their turnaround time can delay targeted therapy, highlighting the need for faster point-of-care alternatives.

• PT/INR & aPTT: An INR >1.5 or aPTT >60 seconds signals significant coagulation factor deficiency. A major limitation is the 30–45 minute turnaround time and their inability to assess platelet function or fibrinolysis.
• Fibrinogen & Platelets: These are the critical substrates for clot formation. A fibrinogen level <150 mg/dL is a hallmark of acute trauma-induced coagulopathy (TIC). A platelet count <100×10⁹/L increases bleeding risk, and transfusion is typically indicated for counts <50×10⁹/L in the setting of active hemorrhage.
• Lactate & Base Deficit: These are markers of global tissue hypoperfusion. A lactate >4 mmol/L or a base deficit more negative than –6 mEq/L are strongly correlated with shock severity and mortality.

3. Point-of-Care Viscoelastic Testing (TEG/ROTEM)

Viscoelastic tests like Thromboelastography (TEG) and Rotational Thromboelastometry (ROTEM) provide a rapid, holistic assessment of the entire clotting cascade. They analyze clot kinetics, strength, and fibrinolysis in whole blood, enabling real-time, goal-directed component therapy.

Core Parameters and Actions

Indications & Controversies: These tests are most valuable in patients with active, uncontrolled hemorrhage where coagulopathy is suspected. Their use in massive transfusion protocols (MTPs) has been shown to reduce the administration of unnecessary blood products. However, variability between devices, a lack of universally accepted thresholds, and the need for operator training remain limitations.

4. Clinical Scoring Tools

Simple, validated bedside scores like the ABC score are designed to rapidly identify patients who are likely to require massive transfusion, allowing for protocol activation before definitive lab results are back.

The ABC Score

The Assessment of Blood Consumption (ABC) score assigns one point for each of the following four criteria present on arrival:

• Assessment: Penetrating mechanism of injury
• Blood Pressure: Systolic BP ≤90 mmHg
• Cardiac Rate: Heart Rate ≥120 bpm
• FAST Exam: Positive Focused Assessment with Sonography for Trauma

A score of 2 or more is highly predictive of the need for massive transfusion, with a reported sensitivity of ~75% and specificity of ~85%. However, its performance may be reduced in patients with bradycardia or in geriatric populations. Therefore, it should be supplemented with clinical judgment and physiologic trends.

5. Triggers for Massive Transfusion Protocol (MTP) Activation

The decision to activate an MTP should be based on a harmonized assessment of clinical scores, laboratory values, and viscoelastic findings to avoid both over- and under-transfusion.

6. Integration of Data to Guide Initial Management

Effective management of hemorrhagic shock relies on a seamless integration of rapid triage, point-of-care diagnostics, and evolving laboratory data to guide a balanced resuscitation strategy.

The Resuscitation Workflow

The initial approach should follow a rapid, tiered sequence: use the ABC score and Shock Index to make an initial decision on MTP activation and empirical 1:1:1 component therapy. Simultaneously, obtain point-of-care (POC) lactate and viscoelastic tests. The results of these POC tests should guide the first hour of resuscitation, allowing for a shift from empirical to goal-directed therapy. Central laboratory results are then used to refine targets and guide ongoing management after initial hemostasis is achieved.

Future Directions

The field is moving towards greater standardization of viscoelastic thresholds and the development of machine-learning models that can predict coagulopathy and transfusion needs even earlier. Research into novel biomarkers of endothelial injury and coagulation is ongoing, promising a more personalized approach to trauma resuscitation in the future.