Microcirculation in hemodynamic monitoring: Clinical parameters and their relevance. A review

Microcirculatory integrity is essential for maintaining tissue homeostasis. In critically ill patients, microcirculatory dysfunction is strongly associated with tissue hypoperfusion, multiple organ failure, and increased mortality, yet remains frequently undetected by conventional macrocirculatory parameters. This discrepancy has driven growing interest in identifying reliable bedside tools for microcirculatory assessment in intensive care settings.

To evaluate the prognostic and clinical utility of key microcirculatory monitoring parameters-including lactate, central venous oxygen saturation (SvcO₂), veno-arterial carbon dioxide difference (ΔPCO₂), and capillary refill time (CRT)-in adult critically ill patients.

A systematic review with narrative synthesis was conducted and reported in accordance with the PRISMA guidelines. The search encompassed publications from 2020-2024 in PubMed, Web of Science, ScienceDirect, and Cochrane Library. Studies involving adult ICU patients that assessed the relationship between microcirculatory parameters and clinical outcomes were selected. Out of 250 identified studies, 18 were included after screening, with their quality assessed using the Jadad and Newcastle-Ottawa scales. Methodological heterogeneity precluded meta-analysis.

A ΔPCO₂ >6 mmHg and CRT > 3 s were associated with higher mortality and organ dysfunction, although CRT showed limitations due to subjectivity. Lactate ≥4.1 mmol/L at 6 h was the best predictor (AUC = .845), despite low specificity from non-hypoxic causes. SDF microscopy demonstrated microvascular dysfunction as an independent predictor, though requiring standardization. CRT-guided resuscitation reduced fluid overload; parameter combination improved prognostic accuracy compared to isolated use. The utility of ΔPCO₂, CRT, and lactate depends on clinical context, timing of measurement, and an integrative approach; however, their physiological and methodological limitations - lack of standardised protocols, need for training, and technical constraints - challenge isolated interpretation, reinforcing the need for multimodal strategies and dynamic monitoring.

Integrating microcirculatory monitoring into standard hemodynamic assessment holds potential to improve individualized resuscitation strategies, minimize iatrogenic fluid burden, and enhance outcomes in critically ill patients.