Reference range and variability of Laser-Doppler-Fluxmetry

Mikrozirkulationsstörungen der Haut: Microcirculation disorders of the skin

Veränderungen in der Mikrozirkulation der Haut sind ein häufig beobachtetes Begleitphänomen vieler Erkrankungen, weit über das Spektrum dermatologischer Krankheiten hinausreichend. Nicht alle dieser Veränderungen haben einen Krankheitswert, viele treten temporär auf, ohne schwerwiegende Folgen zu verursachen. Dies trifft für viele inflammatorische Erkrankungen wie die Psoriasis vulgaris oder das atopische Ekzem zu.

Daneben gibt es aber auch Erkrankungen, bei denen funktionell und morphologisch erkennbare Mikroangiopathien zu schwerwiegenden Krankheitsfolgen führen. Eine der wichtigsten Erkrankungen in diesem Zusammenhang ist die systemische Sklerose, eine autoimmune Systemerkrankung mit multiplen Organmanifestationen. Hier sind die Untersuchungen der kutanen Mikrozirkulation sowohl in der Erstdiagnose als auch in der Prognose‐ und Verlaufsbeurteilung von weitreichender Bedeutung.

Auch bei Erkrankungen der peripheren Hämodynamik wie der peripheren arteriellen Verschlusskrankheit (pAVK) und der chronisch venösen Insuffizienz (CVI) spielt das Verständnis von Mikrozirkulationsstörungen eine wichtige Rolle für die Therapie und die Erfolgskontrolle therapeutischer Interventionen.

Microcirculation disorders of the skin

Changes in the microcirculation of the skin are a frequently observed accompanying phenomenon of many diseases, far beyond the spectrum of dermatological diseases. Not all of these changes are pathological, many are transient and have no serious consequences. This is true for many inflammatory diseases such as psoriasis vulgaris or atopic eczema. However, there are also diseases in which functionally and morphologically recognizable microangiopathies lead to severe disease consequences. One of the most important diseases in this context is systemic sclerosis, an autoimmune systemic disease with multiple organ manifestations. Investigations of the cutaneous microcirculation are of great importance for the initial diagnosis as well as for prognosis and assessment of disease progression. In peripheral hemodynamic disorders such as peripheral arterial disease (PAD) and chronic venous insufficiency (CVI), understanding microcirculatory disturbances also plays an important role in therapy and in monitoring the success of therapeutic interventions.

An observational study of microcirculation among healthy individuals by age and sex

OBJECTIVE

This study measured normal ranges of microcirculatory parameters in healthy individuals and investigated differences in parameters by age and sex.

METHODS

Participants were enrolled into three groups with equal numbers of male and female: young (20-39 years), middle-aged (40-59 years), and elderly (60-79 years). Sublingual microcirculation images were obtained using the incident dark field (IDF).

RESULTS

A total of 75 female and 75 male healthy individuals were enrolled. The elderly group had a higher TVD (26.5 [2] vs. 25.2 [1.8]; p = 0.019) and a lower PPV (97 [2] vs. 98 [3]; p = 0.03) than did the young group. In the elderly group, systolic blood pressure (SBP) and mean arterial pressure (MAP) were moderately and positively correlated with MFI score (r = 0.407, p < 0.05, and r = 0.403, p < 0.05, respectively). The female participants had a lower MFI score than did the male participants (2.9 [2.8-3] vs. 3.0 [2.9-3]; p = 0.015).

CONCLUSIONS

This study revealed the range of microcirculatory parameters between different ages and sexes in healthy individuals. We found that blood pressure levels were correlated with microcirculatory parameters, especially in elders and female.

Skin microvascular reactivity in patients with diabetic retinopathy

AIMS

Early detection of microangiopathic complications of diabetes mellitus (DM) is necessary to analyze the patient's condition and prevent disease progression. The study was aimed to investigate the relationship between the presence of retinopathy and decreased reactivity of the microcirculatory bed in patients with diabetes.

METHODS

The study involved 130 subjects: healthy volunteers (n = 48), DM patients without retinopathy (n = 53) and with retinopathy (n = 29). Skin microvascular reactivity was assessed on the forearm using laser Doppler flowmetry with a local heating test combined with occlusion.

RESULTS

The slope of local thermal hyperemia curve (Slope-120) and other parameters of microvascular reactivity showed difference in pairwise comparisons between the groups. Slope-120 had the highest sensitivity (0.759) and specificity (0.717) in detection of diabetic retinopathy. The decrease of Slope-120 was associated with retinopathy (odds ratio (OR) - 8.3 (2.9-24.1), p < 0.001), even after adjusting for other factors (OR - 11.0 (1.6-77.2), p = 0.016).

CONCLUSIONS

Thus, assessment of skin microvascular reactivity may be a useful test for detecting signs of microangiopathic complications and for screening patients in risk group. Decreased microvascular reactivity has been shown to be prospective as an independent indicator of retinopathy in type 1 DM.

Impact of skeletonized harvesting of the internal thoracic artery on intrasternal microcirculation considering preparation quality

OBJECTIVES

Previous studies have demonstrated the impact of internal thoracic artery (ITA) harvesting on microcirculation in parasternal tissues. However, the impact of skeletonized ITA harvesting on intrasternal microcirculation is unknown. Intraskeletal tissue perfusion has been proven to be crucial for deep wound healing. Furthermore, the impact of different levels of surgical preparation quality on intrasternal microcirculation has not been investigated yet.

METHODS

Sternal microcirculation (sLDP) was monitored with a novel Laser Doppler Perfusion needle probe, while the ITA was skeletonized in a pig model. To mimic different levels of preparation quality, satellite veins were either coagulated or not during preparation. To show the effect of ideally avoiding any surgical manipulation on sLDP, the ITA was clipped in a third sham-harvested group.

RESULTS

sLDP was reduced highly significant to 71 [standard deviation (SD): 9]% (P < 0.001) after skeletonized harvesting of the ITA. Coagulation of the satellite veins as a detrimental surgical factor resulted in a significantly stronger reduction of sLDP to 56 (SD: 11)% (P < 0.05) compared to sLDP with non-coagulated satellite veins. ITA clipping reduced sLDP highly significant to 71 (SD: 8)% (P < 0.001) in the sham-operated group.

CONCLUSIONS

ITA harvesting markedly impairs microcirculation of the sternum but remains unavoidable when coronary artery bypass grafting should be performed. Nevertheless, excessive surgical damage and coagulation of satellite veins is avoidable and should be reduced to a minimum to minimize the risk of deep sternal wound healing complications.

Current methods for the assessment of skin microcirculation: Part 1

Microcirculation accounts for about 99% of blood vessels in adults and mediates between the arterial and venous parts of the cardiovascular system, both structurally and functionally. Skin microcirculation consists of two vascular plexuses: superficial and deep. Microcirculation includes vessels with a diameter of less than 150 μm, i.e. arteries, small veins, lymphatic vessels and arteriovenous anastomoses, which build the microcirculation unit. Skin microcirculation may be affected both in systemic pathologies and specific skin disorders. Several non-invasive techniques are available to assess the skin microcirculation. The clinical value is recognised for capillaroscopy and videocapillaroscopy, laser Doppler flowmetry thermography and transcutaneous oxygen measurement. The list of methods that may be used in clinical research also includes: photoplethysmography, orthogonal spectral polarization, near infrared spectroscopy and tissue reflectance spectrophotometry and optical coherence tomography.