Recent advances in bedside microcirculation assessment in critically ill patients

Abstract

Parameters related to macrocirculation, such as the mean arterial pressure, central venous pressure, cardiac output, mixed venous saturation and central oxygen saturation, are commonly used in the hemodynamic assessment of critically ill patients. However, several studies have shown that there is a dissociation between these parameters and the state of microcirculation in this group of patients. Techniques that allow direct viewing of the microcirculation are not completely disseminated, nor are they incorporated into the clinical management of patients in shock. The numerous techniques developed for microcirculation assessment include clinical assessment (e.g., peripheral perfusion index and temperature gradient), laser Doppler flowmetry, tissue oxygen assessment electrodes, videomicroscopy (orthogonal polarization spectral imaging, sidestream dark field imaging or incident dark field illumination) and near infrared spectroscopy. In the near future, the monitoring and optimization of tissue perfusion by direct viewing and microcirculation assessment may become a goal to be achieved in the hemodynamic resuscitation of critically ill patients.

Perioperative Quality Initiative (POQI) consensus statement on fundamental concepts in perioperative fluid management: fluid responsiveness and venous capacitance

“…As noted above, dysfunction at these levels may develop or persist despite the appearance of normal macrocirculatory parameters, and devices to characterize the microcirculation and cellular function are not routinely available for clinical use. The microcirculation may be assessed directly using tools such as intravital microscopy or laser Doppler flowmetry, or indirectly using tissue oximetry and near infrared spectroscopy (Tafner et al, 2017). Clinical examination (e.g., examination of capillary refill time or assessing for skin mottling) may also give important clues about the adequacy of perfusion in the microcirculation (Hernandez et al, 2019).…”

Peripheral perfusion index predicting early hypoperfusion, reflecting lactate clearance rate and length of ICU stay in surgical patients: an observational study

“…It is measured using pulse co-oximetry technology which is characterized by being real-time and noninvasive. PPI is defined as "the ratio of pulsatile blood flow to the non-pulsatile blood flow", mirroring the strength of blood flow and quality of perfusion at sensor site, reflecting perfusion state of the body part [7,8]. In contrast to lactate value, it's real-time and easy to monitor [8].…”

“…PPI is defined as "the ratio of pulsatile blood flow to the non-pulsatile blood flow", mirroring the strength of blood flow and quality of perfusion at sensor site, reflecting perfusion state of the body part [7,8]. In contrast to lactate value, it's real-time and easy to monitor [8]. Besides, as a reflection of perfusion state, PPI may be a predictor of slower lactate clearance rate (LCR), indicating hypoperfusion in advance.…”

Effects of Fluids on the Macro- and Microcirculations

“…These parameters can be used to monitor the effects of fluid on the microcirculation [ 32 ]. Due to the limited availability of monitoring equipment and the need for offline analysis of images acquired, at present microcirculation measurement remains primarily a research tool [ 33 ].…”