Clinical review: Clinical imaging of the sublingual microcirculation in the critically ill - where do we stand?

Abstract

A growing body of evidence exists associating depressed microcirculatory function and morbidity and mortality in a wide array of clinical scenarios. It has been suggested that volume replacement therapy using fluids and/or blood in combination with vasoactive agents to modulate macro- and microvascular perfusion might be essential for resuscitation of severely septic patients. Even after interventions effectively optimizing macrocirculatory hemodynamics, however, high mortality rates still persist in critically ill and especially in septic patients. Therefore, rather than limiting therapy to macrocirculatory targets alone, microcirculatory targets could be incorporated to potentially reduce mortality rates in these critically ill patients. In the present review we first provide a brief history of clinical imaging of the microcirculation and describe how microcirculatory imaging has been of prognostic value in intensive care patients. We then give an overview of therapies potentially improving the microcirculation in critically ill patients and propose a clinical trial aimed at demonstrating that therapy targeting improvement of the microcirculation results in improved organ function in patients with severe sepsis and septic shock. We end with some recent technological advances in clinical microcirculatory image acquisition and analysis.

International Study on Microcirculatory Shock Occurrence in Acutely Ill Patients*

“…Furthermore, by aiming for consensus between SDF researchers, we aimed to keep differences in analysis to a minimum. It must be mentioned, however, that although improved technology is forthcoming, the current need for detailed offline analysis is a severe impairment of the practical bedside applicability of this technique (55). Finally, the limited macrohemodynamic monitoring did not allow for an extensive evaluation of a possible relationship between S(c)vo 2 or cardiac output and microcirculatory variables.…”

The Microcirculation of the Septic Kidney

“…54 For renal microcirculation these techniques have been used in animal models. SDF imaging has been used in rat models to monitor renal cortical peritubular capillary blood flow.…”

The response of the microcirculation to cardiac surgery

“…The sublingual microcirculation is the site most commonly used at the bedside to visualize the microcirculation, and the use of this site to investigate the effects of disease and therapy on microcirculatory function is well established [15]. Three generations of handheld microscopes have been developed to monitor the sublingual microcirculation over the last 2 decades [16]. Owing to a number of shortcomings of the first and second generation devices, including limited clinical applicability, and the lack of direct computer control of the imaging modality essential for automatic analysis of the microcirculatory images for measurement of functional microcirculatory parameters, a third-generation device, the CytoCam-Incident-Dark-Field (IDF) device, was recently developed based on incident dark-field imaging [17,18 & ,19].…”