Current Methods, Quality Control, and Translational Perspectives for Bedside Sublingual Microcirculation Monitoring in Critical Illness

Summary

This review examines current methods for bedside sublingual microcirculation monitoring, emphasizing acquisition quality, standardized reporting, validation, and clinical translation. It distinguishes established evidence from author-proposed concepts and outlines practical priorities for reproducibility, safety, and future clinical evaluation.

Abstract

Microcirculatory abnormalities may persist after blood pressure, cardiac output, and other systemic hemodynamic targets have been restored in critically ill patients. The sublingual mucosa provides an accessible site for repeated bedside assessment of the microcirculation, but routine clinical implementation remains limited by acquisition artifacts, operator dependence, image-analysis burden, variable measurement quality, and uncertain relationships with therapeutic decision-making. This narrative review aims to examine current methods for bedside sublingual microcirculation monitoring, evaluate their strengths and limitations, and identify practical priorities for translation into routine clinical practice. The review summarizes established and emerging measurement approaches for assessing vascular morphology, vessel density, blood-cell flow patterns, regional velocity-related signals, tissue oxygenation, and data quality, emphasizing that these complementary measurements are not interchangeable and require rigorous quality control. It further outlines standardized acquisition and reporting considerations, performance metrics, repeatability testing, analytical validation, and benchmark comparisons appropriate for different measurement domains. Finally, an author-proposed modular workflow is presented to illustrate a structured framework for sensing, quality control, data processing, and bedside reporting. This conceptual framework is intended to guide future technical development and clinical validation and does not represent a clinically validated device, diagnostic system, or treatment algorithm.

Introduction

Shock resuscitation is commonly guided by blood pressure, cardiac output, lactate, and other systemic variables. Although these measures are indispensable, they do not always indicate whether blood is reaching individual capillary beds effectively. In sepsis, endothelial injury, glycocalyx disruption, altered blood-cell interactions, and dysregulated vascular control can reduce perfused capillary density and produce heterogeneous blood flow^1,2. When systemic hemodynamics improve without a corresponding recovery in tissue perfusion, this dissociation is described as hemodynamic incoherence³