Objective:

To raise methodological concerns regarding the composite definition of fluid responsiveness used by Tongyoo et al., particularly the reliance on MAP increase as a criterion.

Approach:

• Fluid Responsiveness Definition: Critique of the composite definition of fluid responsiveness used by Tongyoo et al., which includes MAP increase as a criterion.
• Conventional Understanding: Discussion on the conventional hemodynamic definition of fluid responsiveness focusing on cardiac output (CO) or cardiac index (CI).
• Physiological Considerations: Examination of the relationship between MAP and CO, highlighting that MAP increases may not indicate improved forward flow.
• Cohort Characteristics: Analysis of the cohort studied by Tongyoo et al., particularly the prevalence of septic shock and its impact on vascular tone.
• Recommendations for Further Analysis: Suggestion for sensitivity analysis and reporting of concomitant changes in noninvasive surrogates of cardiac output.

Key Findings:

• More than half of the responders in the study were classified based on MAP increase alone.
• Conventional definitions emphasize CO or CI as the reference for fluid responsiveness, not MAP.
• MAP changes may reflect vascular tone alterations rather than true preload-dependent flow improvements.
• Lack of data on systemic vascular resistance and vasoactive medications limits interpretation of MAP-only responses.

Interpretation:

The composite endpoint used by Tongyoo et al. may have implications for the classification of patients and the diagnostic performance metrics of the evaluated variables.

Limitations:

• Absence of systemic vascular resistance data before and after fluid challenge.
• Lack of detailed information on concurrent vasoactive medication changes.

Conclusion:

Further analysis is needed to assess the diagnostic performance of the investigated variables when fluid responsiveness is defined by conventional flow-based endpoints.

Sources:

• Tongyoo et al. Study
• CODEFIRE Consensus
• ESICM Guidelines
• Monnet et al. Study
• Ait-Hamou et al. Study