What is the classification of shock based on base deficit?

Classification of Shock Based on Base Deficit

Base deficit is a highly sensitive marker for the extent of shock and mortality, with a well-established classification system dividing shock into four categories: mild (-3 to -5 mEq/L), moderate (-6 to -9 mEq/L), severe (<-10 mEq/L), and normal/base excess (>0 mEq/L). 1

Base Deficit Classification System

The widely accepted classification of shock based on base deficit consists of four classes:

• Class I (Mild Shock): Base deficit -3 to -5 mEq/L 1

  • Associated with mild tissue hypoperfusion
  • Lower transfusion requirements
  • Mortality rate approximately 7-15% 2, 3

• Class II (Moderate Shock): Base deficit -6 to -9 mEq/L 1

  • Associated with moderate tissue hypoperfusion
  • Increased transfusion requirements
  • Higher risk of post-traumatic organ failure 1

• Class III (Severe Shock): Base deficit <-10 mEq/L 1

  • Associated with severe tissue hypoperfusion
  • High transfusion requirements
  • Mortality rate can exceed 50% 2, 3

• Class IV (Normal/Base Excess): Base deficit >0 mEq/L 1

  • Normal or alkalotic state
  • Better prognosis compared to other classes

Clinical Significance and Correlation

Base deficit has been established as a potent independent predictor of mortality in patients with traumatic-hemorrhagic shock 1:

• Significant correlation exists between admission base deficit and:

  • Transfusion requirements within the first 24 hours 1
  • Risk of post-traumatic organ failure 1
  • Mortality 1

• Base deficit is a better prognostic marker of death than arterial pH 1

• Base deficit is particularly sensitive for shock severity and mortality prediction in:

  • Adult trauma patients 1
  • Pediatric trauma patients 4
  • Elderly trauma patients (>55 years) 1

Alternative Classification System

More recent research has proposed a refined classification system based on larger patient datasets 3:

• Class I: Base deficit ≤2 mmol/L
• Class II: Base deficit >2.0 to 6.0 mmol/L
• Class III: Base deficit >6.0 to 10 mmol/L
• Class IV: Base deficit >10 mmol/L

This newer classification has demonstrated better discrimination of transfusion requirements, massive transfusion rates, and mortality compared to conventional ATLS classification of hypovolemic shock 3, 5.

Clinical Application

• Base deficit should be measured early and repeatedly to monitor shock progression and response to treatment 1

• Independent assessment of both base deficit and serum lactate is recommended, as these parameters do not strictly correlate with each other in severely injured patients 1

• In alcohol-associated trauma, base deficit may be a better predictor of prognosis than lactate, as alcohol itself can increase blood lactate levels 1, 6

• Base deficit measurements should be considered during initial trauma evaluation to identify hypovolemic shock and guide blood product administration 3, 5

Pitfalls and Considerations

• Clinicians should be aware that large volume resuscitation with 0.9% saline can cause hyperchloremic metabolic acidosis, potentially leading to a persistent base deficit that does not reflect ongoing shock 7

• Base deficit classification applies across different trauma populations, including those with traumatic brain injury 2

• Base deficit has been shown to be superior to vital signs in predicting outcomes in both adult and pediatric trauma patients 4, 3