Microcirculatory imaging (MI) is used to monitor peripheral perfusion in critically ill or preterm neonates. This manuscript and video demonstrates the optimal approach for obtaining high-quality images.
Microcirculatory imaging (MI) is a relatively new research tool mainly used in the intensive care setting. MI provides a clear view of the smallest capillaries, arterioles and venules. The magnifying effect visualizes the flow pattern of erythrocytes through these vessels.
It’s non-invasive character makes it suitable to apply in (preterm) neonates, even in cardiorespiratory unstable patients. In adults and children, MI is mainly performed sublingually, but this is not possible in preterm infants as these cannot cooperate and the size of the probe is problematic. In preterm infants, MI is therefore performed transcutaneously. Their thin skin makes it possible to obtain high quality images of peripheral microcirculation.
In this manuscript we will demonstrate the method of transcutaneous MI in preterm infants. We will focus on the different techniques and provide tips to optimize image quality. The highlights of software settings, safety and offline analysis are also addressed.
Hemodynamic diagnostics in critically ill preterm neonates has always been difficult. Most diagnostic tools used in adults cannot be applied in these tiny preterm infants; and then there is a problem of the sensitivity of the outcome parameters. But most of all, these infants are so vulnerable, that the risks of diagnostic procedures do not outweigh the benefits. As a result, in the field of neonatology, hemodynamics has been neglected and therefore there is a lack of knowledge on this topic.
An interesting option for handling these problems might be visualizing the microcirculation. The introduction of handheld microscopes in the late 1990s made it possible to visualize the microcirculation in a non-invasive manner. Three generations of devices have been introduced: Orthogonal Polarization Spectral (OPS) imaging1, Sidestream Dark Field (SDF) imaging2, and Incident Dark Field (IDF) imaging3. They all use more or less the same technique in which green light with a specific wavelength (548nm) stroboscopic illuminates the microcirculation. The green light is absorbed by oxy- and deoxyhemoglobin and mostly reflected by the surrounding tissue. This property of green light therefore creates visible contrast. The reflected light passes a magnification lens and is projected on a camera sensor. Hereby it is possible to visualize the flowing red blood cells at a depth of approximately one millimeter of mucosal tissue or directly at solid organs.
Over the past 15 years, the microcirculation has been mainly studied in adults, especially in patients with septic shock4-6. These observational studies found that persistent microcirculatory alterations were associated with organ failure and mortality. This observation cannot be extrapolated directly to (preterm) infants however, as in the adults the microcirculation was measured sublingually. High quality images of the sublingual microcirculation cannot be obtained in preterm infants because they are unable to cooperate. In term infants the buccal microcirculation has been the area of interest7. Fortunately, in preterm infants the thin skin allows transcutaneous microcirculatory imaging. This approach has been applied in neonatal studies focusing on blood transfusion8, therapeutic hypothermia9 and hypotension10.
In this manuscript we present our protocol for transcutaneous microcirculatory imaging using Incident Dark Field imaging in preterm neonates. We will focus on different strategies to acquire the highest quality images. Technical details and differences between the SDF and IDF devices can be found elsewhere11.
I dette manuskriptet beskriver vi og demonstrere tilnærming for transkutan microcirculatory bildebehandling hos premature nyfødte. Visualisere denne metoden vil hjelpe forskere vinne to av de største utfordringene i forskningen: reproduserbarhet og tid og arbeidskrevende natur lære nye teknikker. Denne teknikk kan gi nyttig informasjon fra perifert mikrosirkulasjon i premature barn i en ikke-invasiv måte. Serielle målinger kan hjelpe klinikere evaluere effekten av terapeutiske intervensjoner. Mikrosirkulasjonen er…
The authors have nothing to disclose.
We thank J. Hagoort for reading and correcting the manuscript.
Cytocam | Braedius | http://www.braedius.com/magnoliaPublic/braedius/products.html | Other well known handheld microscopes to visualize the microcirculation are MicroScan (Microvision Medical) using SDF technique or the CytoScan (CytoMetrics) using OPS technique |
Disposable Lens Cover | Glycocheck | http://www.glycocheck.com/lenscovers.php | |
CCTools | Braedius | http://www.braedius.com/magnoliaPublic/braedius/products.html | Another well known offline analysis programme is AVA (Microvision medical). |