Kidney perfusion in critical illness: between the macrocirculation and the microcirculation.

Area of Science:

• Critical Care Medicine
• Nephrology
• Hemodynamics

Background:

• Acute kidney injury (AKI) is a significant challenge in critical care, associated with high morbidity and mortality.
• Current hemodynamic monitoring for AKI often relies on central measurements that poorly correlate with kidney hemodynamics.

Purpose of the Study:

• To review existing and emerging tools for integrating macrocirculatory and microcirculatory perspectives in AKI management.
• To highlight strategies for better understanding and preventing AKI through advanced monitoring.

Main Methods:

• Review of current hemodynamic monitoring techniques and their limitations in AKI.
• Discussion of advanced bedside ultrasound (CEUS, high-frame-rate, super-resolution) for renal microcirculation assessment.
• Inclusion of urinary partial oxygen pressure monitoring for medullary hypoxia detection.

Main Results:

• Central hemodynamic measurements inadequately reflect kidney hemodynamics.
• Contrast-enhanced ultrasound (CEUS) reveals impaired renal perfusion despite adequate systemic flow.
• Emerging ultrasound techniques and urinary oxygen monitoring offer detailed insights into renal microcirculation and hypoxia.

Conclusions:

• Multimodal hemodynamic monitoring can identify treatable AKI sub-phenotypes and guide precision therapies.
• Integrating macrocirculatory and microcirculatory data is crucial for optimizing AKI management.
• Future trials should include mechanistic endpoints from both circulatory domains to enhance patient outcomes.