Understanding the Nuanced Concept of Hemodynamic Incoherence and Its Underlying Physiology

Area of Science:

• Physiology
• Critical Care Medicine
• Hemodynamics

Background:

• Hemodynamic incoherence is defined as a dissociation between normalized macrocirculation and impaired tissue perfusion.
• This phenomenon is not physiologically uniform, necessitating a clearer distinction between its underlying causes.

Purpose of the Study:

• To propose a conceptual distinction between two forms of macro-microcirculatory incoherence.
• To provide a framework for understanding the distinct pathophysiological mechanisms of tissue malperfusion.

Main Methods:

• Conceptual analysis based on the four-interface model of circulation.
• Distinguishing between primary microcirculatory dysfunction and secondary impairment due to systemic hemodynamic constraints.

Main Results:

• Type 1 incoherence: Primary microcirculatory dysfunction causing heterogeneous capillary perfusion despite adequate macrocirculation (e.g., sepsis).
• Type 2 incoherence: Secondary microcirculatory impairment due to systemic factors like vasoconstriction, low cardiac output, or venous congestion.
• The four-interface model explains these as failures of energy transfer across hemodynamic domains.

Conclusions:

• Recognizing distinct forms of hemodynamic incoherence improves physiologic interpretation of shock.
• Differentiating these mechanisms aids in avoiding conflation of distinct pathophysiological processes.
• This distinction is crucial for individualizing therapeutic interventions for tissue malperfusion phenotypes.