What are the classes of hemorrhagic shock?

From the Guidelines

Hemorrhagic shock is classified into four classes based on the amount of blood loss and associated physiological changes, as outlined in the most recent European guideline on management of major bleeding and coagulopathy following trauma: sixth edition 1.

Classification of Hemorrhagic Shock

The classes of hemorrhagic shock are defined as follows:

• Class I: up to 15% blood volume loss (about 750 mL in adults) with minimal clinical symptoms, normal vital signs, and slight anxiety.
• Class II: 15-30% blood volume loss (750-1500 mL), presenting with tachycardia, tachypnea, decreased pulse pressure, and mild anxiety.
• Class III: 30-40% blood volume loss (1500-2000 mL), characterized by marked tachycardia, tachypnea, hypotension, altered mental status, and decreased urine output.
• Class IV: more than 40% blood volume loss (>2000 mL), with profound hypotension, minimal or absent pulse, decreased consciousness, and negligible urine output.

Key Considerations

These classes are based on the American College of Surgeons Advanced Trauma Life Support classification of haemorrhage severity, which takes into account blood loss, pulse rate, blood pressure, pulse pressure, respiratory rate, urine output, and central nervous system status 1. The classification of hemorrhagic shock is crucial for guiding treatment, which escalates with severity, ranging from crystalloid fluid resuscitation in milder cases to immediate blood product transfusion, vasopressors, and surgical intervention in severe cases 1. Early recognition of shock class is essential for appropriate management, as delayed treatment can lead to irreversible organ damage and death due to inadequate tissue perfusion and cellular oxygen delivery.

From the Research

Classes of Hemorrhagic Shock

The classes of hemorrhagic shock can be categorized based on different criteria, including:

• The American College of Surgeons' classification, which categorizes shock into four classes:
  • Distributive
  • Obstructive
  • Cardiogenic
  • Hemorrhagic 2
• The Advanced Trauma Life Support (ATLS) classification, which categorizes hemorrhagic shock into four classes based on blood loss and clinical signs 3
• A base deficit-based classification, which categorizes hypovolemic shock into four classes based on base deficit (BD) levels:
  • Class I (BD≤2 mmol/l)
  • Class II (BD>2.0 to 6.0 mmol/l)
  • Class III (BD>6.0 to 10 mmol/l)
  • Class IV (BD>10 mmol/l) 4

Characteristics of Each Class

Each class of hemorrhagic shock has distinct characteristics, including:

• Increasing severity of blood loss and clinical signs
• Decreasing hemoglobin and prothrombin ratios
• Increasing amount of transfusions and fluid resuscitation required
• Increasing mortality rates 3, 4

Clinical Assessment and Management

The assessment and management of hemorrhagic shock involve:

• Early recognition and management of hemorrhage
• Correction of coagulopathies and homeostatic imbalances
• Expedient and definitive control of the source of bleeding
• Appropriate fluid resuscitation and blood transfusion 5, 6