The Baux Score Nomogram: Purpose and Application in Burn Patients
The Baux score nomogram is a clinical tool designed to quickly and accurately calculate mortality risk in burn patients without requiring electronic devices, providing critical prognostic information to guide treatment decisions and resource allocation.
What is the Baux Score?
The Baux score was originally defined as the sum of age in years and percent total body surface area (TBSA) burned to predict mortality after burn trauma. However, advances in burn care rendered this original score too pessimistic, leading to its revision 1.
Evolution of the Baux Score:
- Original Baux Score: Age + %TBSA burned
- Revised Baux Score: Age + %TBSA burned + 17*(Inhalation Injury, where 1=yes, 0=no)
The revised version accounts for inhalation injury, which adds the equivalent of 17 years (or 17% burn) to the mortality risk calculation 1.
Purpose of the Baux Score Nomogram
The nomogram for the Revised Baux Score serves several important purposes:
Mortality Prediction: Provides accurate mortality risk assessment with a high area under the curve (AUC) of 0.93 (CI 0.91-0.95) across diverse patient populations 2.
Clinical Accessibility: Enables calculations without electronic devices, which may be unavailable in certain clinical settings 3.
Speed and Accuracy: Offers quick assessment with high precision (bias of only -0.003 percentage points) 3.
Decision Support: Helps clinicians determine appropriate treatment intensity and resource allocation.
Triage Tool: Assists in patient prioritization during mass casualty incidents involving burns.
Clinical Application
When to Use the Baux Score:
- During initial assessment of burn patients
- When determining need for transfer to specialized burn centers
- For communicating severity between healthcare providers
- To inform discussions about prognosis with patients and families
How to Calculate:
- Accurately measure TBSA using the Lund-Browder chart (most accurate method) 4
- Note patient's age in years
- Determine presence/absence of inhalation injury
- Calculate Revised Baux Score: Age + %TBSA + 17*(inhalation injury)
- Use the nomogram to convert this score to mortality probability
Important Considerations and Limitations
Accuracy of TBSA Measurement
- The Lund-Browder chart is recommended as the most accurate method for TBSA quantification 4
- Wallace rule of nines significantly overestimates TBSA and is not suitable for children 4
- TBSA is often overestimated in 70-94% of cases, leading to excessive fluid resuscitation 4
Limitations of the Baux Score:
- Age Extremes: The Revised Baux equation has diminished predictive ability at both extremes of age 2
- Comorbidities: The Updated Charlson Comorbidity Index (CCI) is independently associated with mortality and should be considered alongside the Baux score 5
- Non-burn Deaths: Approximately 25% of burn patients who die with Baux scores <100 die from causes unrelated to their burns (primarily cerebrovascular, cardiovascular, or respiratory disease) 6
Integration with Burn Management
The Baux score should be used as part of a comprehensive burn management approach that includes:
- Appropriate fluid resuscitation based on accurate TBSA assessment
- Early consultation with burn specialists to determine need for transfer to specialized burn centers 4
- Consideration of telemedicine for initial assessment when direct specialist consultation is unavailable 4
- Monitoring for compartment syndrome in extremity injuries
- Appropriate wound care and pain management
Practical Implementation
The nomogram provides a low-cost, accessible tool that can be used:
- During initial assessment in emergency departments
- In pre-hospital settings where electronic devices may be limited
- To cross-check calculations made by other methods
- For rapid communication of mortality risk between providers
By incorporating the Baux score nomogram into burn assessment protocols, clinicians can make more informed decisions about patient care, resource allocation, and the need for specialized burn center care.