Microvascular Flow Index Research Articles

Microvascular function in healthy volunteers; a comparison of manually and automatically derived measurements

Microcirculatory dysfunction plays a significant role in the pathophysiology of critical illness, including sepsis, haemorrhage and cardiogenic shock. Studies have used video microscopic measurements of the sublingual microcirculation in acute illness, but the clinical utility of these techniques are limited by the need for time-consuming analysis that precludes near-patient data interpretation. The newest video microscopes use Incident Dark Field (IDF) illumination technology (see below) with automated analysis. However the automated analysis has not been validated and there are no data on normal ranges in healthy individuals. This limits the potential application of IDF video microscopy for microcirculation research. This study aims to examine the feasibility and accuracy of measurement of sublingual microvascular function in the awake individual establish the summary statistics of different sublingual microvascular measurements and compare these measurements in three age groups; 18–34 yrs, 35–54 yrs and over 54 yrs. Additionally, this study will correlate the automatically derived measurements of microcirculatory function in comparison to the current gold-standard of manual analysis. An observational study of 150 healthy volunteers, which will include the recording of basic physiological data, medical and drug history, followed by an assessment of the sublingual microvascular bed using CytoCam incident dark field microscopy to measure total vessel density (TVD), perfused vessel density (PVD), and microvascular flow index (MFI). Analysis using current gold standard manual analysis with automated analysis using CytoCam Tool 1.7 (Braedius Medical BV) Analysis plan: (a.) Computation of summary statistics of TVD, PVD, and MFI to determine normal ranges for both manual and automated analysis methods at the population level as well as age-related subgroup level (18-34 yrs, 35-54 yrs and 55 yrs and over). (b.) Estimation of correlation between automatically and manually derived values of TVD, PVD, and MFI within each subject. (c.) Comparison of mean TVD, PVD, and MFI between the age-related subgroup (18-34yrs, 35-54 yrs and 55 yrs and over). Progress: This study has currently recruited 91 of 150 subjects. The procedure of measurement has been found to be well tolerated, with no subjects withdrawing from the study once enrolled. Further, it has been possible, following 2 days of intense work, to train a further member of the team to make reliable, high quality recordings, demonstrating the scope for training those new to the technique to use it in the clinical setting. We look forward to producing full results in the near future.

Effects of açaí and cilostazol on skin microcirculation and viability of TRAM flaps in hamsters

BackgroundTissue necrosis caused by insufficient perfusion is a major complication in flap transfer. This study evaluated whether treatment with cilostazol or hydroalcoholic extract of seeds of Euterpe oleracea Mart. (açaí) protects the transverse rectus abdominis myocutaneous (TRAM) flap against ischemic damage in hamsters. Materials and methodsFifty-four hamsters were divided into three oral treatment groups: placebo, açaí, or cilostazol. Caudally based, unipedicled TRAM flaps were raised, sutured back, classified into four vascular zones (I-IV), and evaluated for tissue viability, capillary blood flow (CBF), perfused vessel density (PVD), and microvascular flow index (MFI) by orthogonal polarization spectral imaging at three time points: immediately postoperatively (IPO), 24 h postoperatively (24hPO), and 7 d postoperatively (7POD). ResultsComparing to placebo, açaí increased PVD at IPO and açaí and cilostazol increased CBF and PVD at 24hPO in zone I; cilostazol increased CBF, PVD, and MFI at IPO, and CBF at 24hPO in zone II; açaí and cilostazol increased CBF at all time points and PVD and MFI at IPO and 24hPO in zone III; cilostazol increased CBF at IPO and 7POD, açaí increased CBF at 7POD, and both increased PVD and MFI at all time points in zone IV; and açaí and cilostazol increased the percentage of viable area in zones III and IV. ConclusionsAçaí and cilostazol treatments had a protective effect against ischemic damage to TRAM flaps in hamsters, improving microvascular blood flow and increasing the survival of flap zones contralateral to the vascular pedicle (zones III and IV).

Sidestream Dark Field Imaging of the Microcirculation to Assess Preeclampsia Microvascular Dysfunction.

BackgroundDevelopment of predictive models of preeclampsia has only yielded modest results. We hypothesized that impaired indices of microcirculatory function could be detected using sidestream dark field imaging. The objective of this study was to examine microvascular function in women at high risk for preeclampsia at mid-gestation.MethodsWomen between 16 and 22 weeks of gestation were screened for eligibility. Patients were recruited if they met eligibility criteria indicating high risk for preeclampsia. Investigators performed non-invasive sidestream dark field imaging of the sublingual microcirculation. Images were analyzed to determine microcirculatory parameters (microvascular flow index, perfused vessel density, total vessel density, and proportion of perfused vessels). After delivery, charts were reviewed to determine if they developed gestational hypertension, preeclampsia or severe preeclampsia.ResultsTwelve of 66 participants (18.2%) developed preeclampsia or severe preeclampsia during the course of their pregnancy. Microvascular flow index was not significantly different between participants with normal pregnancies and participants with preeclampsia or severe preeclampsia (2.75 ± 0.38 vs. 2.80 ± 0.34, respectively; P = 0.459). Similarly, there were no significant differences between groups in the remaining microcirculatory parameters.ConclusionsSidestream dark field imaging of the sublingual microcirculation may remain an appropriate tool to identify women at risk for preeclampsia, albeit later in pregnancy.

Preliminary clinical evaluation of automated analysis of the sublingual microcirculation in the assessment of patients with septic shock: Comparison of automated versus semi-automated software.

The outcome of patients in septic shock has been shown to be related to changes within the microcirculation. Modern imaging technologies are available to generate high resolution video recordings of the microcirculation in humans. However, evaluation of the microcirculation is not yet implemented in the routine clinical monitoring of critically ill patients. This is mainly due to large amount of time and user interaction required by the current video analysis software. The aim of this study was to validate a newly developed automated method (CCTools®) for microcirculatory analysis of sublingual capillary perfusion in septic patients in comparison to standard semi-automated software (AVA3®). 204 videos from 47 patients were recorded using incident dark field (IDF) imaging. Total vessel density (TVD), proportion of perfused vessels (PPV), perfused vessel density (PVD), microvascular flow index (MFI) and heterogeneity index (HI) were measured using AVA3® and CCTools®. Significant differences between the numeric results obtained by the two different software packages were observed. The values for TVD, PVD and MFI were statistically related though. The automated software technique successes to show septic shock induced microcirculation alterations in near real time. However, we found wide degrees of agreement between AVA3® and CCTools® values due to several technical factors that should be considered in the future studies.

Mildly elevated lactate levels are associated with microcirculatory flow abnormalities and increased mortality: a microSOAP post hoc analysis

BackgroundMildly elevated lactate levels (i.e., 1–2 mmol/L) are increasingly recognized as a prognostic finding in critically ill patients. One of several possible underlying mechanisms, microcirculatory dysfunction, can be assessed at the bedside using sublingual direct in vivo microscopy. We aimed to evaluate the association between relative hyperlactatemia, microcirculatory flow, and outcome.MethodsThis study was a predefined subanalysis of a multicenter international point prevalence study on microcirculatory flow abnormalities, the Microcirculatory Shock Occurrence in Acutely ill Patients (microSOAP). Microcirculatory flow abnormalities were assessed with sidestream dark-field imaging. Abnormal microcirculatory flow was defined as a microvascular flow index (MFI) < 2.6. MFI is a semiquantitative score ranging from 0 (no flow) to 3 (continuous flow). Associations between microcirculatory flow abnormalities, single-spot lactate measurements, and outcome were analyzed.ResultsIn 338 of 501 patients, lactate levels were available. For this substudy, all 257 patients with lactate levels ≤ 2 mmol/L (median [IQR] 1.04 [0.80–1.40] mmol/L) were included. Crude ICU mortality increased with each lactate quartile. In a multivariable analysis, a lactate level > 1.5 mmol/L was independently associated with a MFI < 2.6 (OR 2.5, 95% CI 1.1–5.7, P = 0.027).ConclusionsIn a heterogeneous ICU population, a single-spot mildly elevated lactate level (even within the reference range) was independently associated with increased mortality and microvascular flow abnormalities. In vivo microscopy of the microcirculation may be helpful in discriminating between flow- and non-flow-related causes of mildly elevated lactate levels.Trial registrationClinicalTrials.gov, NCT01179243. Registered on August 3, 2010.

Experience of Sublingual Microcirculation Evaluation in Adults Patients with Severe Dengue

BackgroundSevere microcirculatory changes are involved in the pathophysiological mechanisms that lead to irreversible final stages of dengue shock. We report our experience of the evaluation of sublingual microcirculation in adult patients with severe dengueMethodsAdults patients with severe dengue (by WHO 2009 criteria) were included. Dengue diagnostics was made by positive serology for IgM / IgG, antigen NS1 or PCR. Sublingual Microcirculation (SM) was evaluated by Sidestream Dark Field imaging. Microvascular flow index (MFI), proportion of small-perfused vessels (%SVP), heterogeneity index (HI) and Total Vascular Density were calculated. All patients received Fluids Challenge (FC) at hospital admission.ResultsSM was assessed in 10 patients. The median age was 65 years [IQR: 34–70], 60% were male. Eight patients were admitted to the ICU, of which 63% required invasive ventilatory and vasoactive support. One patient died. After the fluid challenge, the median of the %SVP was 94 [IR: 97 – 77], the median of the MFI was 2.82 [IR: 2, 85 – 2, 14]. There were not significant differences in %SVP and MFI among the patients who survived. In the deceased patient, the %SVP with continuous flow was 59, 18% and the MFI was 1, 45; these values were significantly decreased compared with patients who survived. A significant negative correlation between hematocrit and %SVP, and MFI was found.ConclusionInitial fluid challenge, that identifies and treats volume depletion, could correct microcirculation abnormalities evaluated by SDF imaging. However, in the patient who did not respond to this challenge, significant alterations of the MFI and the %SVP were evidenced. There is a need for more studies to improve our understanding of the role of microcirculation evaluation in these patients.Disclosures All authors: No reported disclosures.

Increased microcirculatory heterogeneity in patients with obstructive sleep apnea.

IntroductionObstructive sleep apnea (OSA) is the most common form of sleep disordered breathing and has been associated with major cardiovascular comorbidities. We hypothesized that the microcirculation is impaired in patients with OSA and that the magnitude of impairment correlates to OSA severity.MethodsSubjects were consecutive patients scheduled for routine diagnostic polysomnography (PSG). OSA was defined by paradoxical rib cage movements together with abdominal excursions and by the apnea-hypopnea index (AHI) (events/hour; no apnea AHI<5; mild apnea 5≤AHI<15; moderate apnea 15≤AHI<30; severe apnea AHI ≥30). Sidestream darkfield imaging was used to assess the sublingual microcirculation. Recordings of sublingual microcirculation (5 random sites) were performed before and after overnight PSG. Data are summarized as mean (±SD); p values <0.05 were considered statistically significant.ResultsThirty-three consecutive patients were included. OSA was diagnosed in 16 subjects (4 moderate, 12 severe). There was no significant difference in microcirculation between subjects with moderate OSA and without OSA. However, compared to subjects without OSA, subjects with severe OSA (AHI≥30) showed a significant decrease of microvascular flow index (-0.07±0.17 vs. 0.08±0.14; p = 0.02) and increase of microvascular flow index heterogeneity (0.06±0.15 vs. -0.06±0.11; p = 0.02) overnight. Multiple regression analysis (adjusted for age and gender) showed both decrease of flow and increase of flow heterogeneity associated with AHI (b = -0.41; F = 1.8; p = 0.04 and b = 0.43; F = 1.9; p = 0.03, respectively).ConclusionAcute overnight microcirculatory changes are observed in subjects with severe OSA characterized by decreased flow and increased flow heterogeneity.

An observational study of microcirculation in dialysis patients and kidney transplant recipients.

Microcirculatory dysfunction contributes to acute and chronic kidney diseases. To the best of our knowledge, no study has compared differences in microcirculation among healthy volunteers, dialysis patients and kidney transplant recipients. Sublingual microcirculation was examined using sidestream dark field imaging and was compared among 90 healthy volunteers, 40 dialysis patients and 40 kidney transplant recipients. The gender effect on microcirculation and the correlations among the microcirculation parameters, age, body mass index, heart rate and blood pressure were analysed. Total small vessel density, perfused small vessel density and the proportion of perfused small vessels were lower in the dialysis patients than in the healthy volunteers and kidney transplant recipients [total small vessel density; healthy volunteers vs. dialysis patients vs. kidney transplant recipients, 25·2 (2·3) vs. 22·8 (2·6) vs. 24·2 (2·9) mm/mm2 , P < 0·001]. Systolic blood pressure showed a weak negative correlation with the microvascular flow index scores in the healthy volunteers. By contrast, systolic blood pressure, diastolic blood pressure and mean arterial pressure showed weak positive correlations with proportion of perfused small vessels and the microvascular flow index scores in the dialysis patients. Microcirculatory dysfunction is noted in dialysis patients, and this alteration is ameliorated in KT recipients. The positive correlation between blood pressure and microcirculation in dialysis patients suggests that additional studies should investigate the optimal goal of blood pressure management for dialysis patients.

Oral Nitrate Increases Microvascular Reactivity and the Number of Visible Perfused Microvessels in Healthy Volunteers

Nitric oxide (NO) plays an important role in controlling microcirculatory function, but the effects of exogenous administration of nitrate (NO₃^-) on the microcirculation have not been well studied. We evaluated whether NO₃^- could influence the microvascular response to hypoxia in 17 healthy volunteers. We used a vascular occlusion test (VOT) to assess the response of near-infrared spectroscopy-derived indexes to hypoxic stress before and 2 h 15 min after oral administration of 800 mg potassium nitrate. We also monitored changes in the sublingual microcirculation using side-stream dark-field (SDF) video microscopy. The descending (7.3 [6.8-8.1] to 8.2 [7.9-9.8] %/min, p = 0.01) and ascending (201 [180-233] to 240 [197-285] %/min, p = 0.01) thenar oxygen saturation (StO₂) slopes were significantly greater during VOT after nitrate administration than before. Sublingual SDF measurements showed increases in the total number of visible perfused vessels (i.e., from 14.1 [13.2-15.5] to 16.3 [15.4-16.7] vessels/mm, p < 0.01) and in the number of visible perfused small vessels (i.e., from 12.2 [11.5-13.7] to 14.2 [13.5-15.3] vessels/mm, p < 0.01) after nitrate administration but no changes in the microvascular flow index or in the proportion of visible perfused vessels, which were already maximal at baseline. Oral administration of nitrate therefore significantly influenced the response to a hypoxic challenge, increasing the number of visible perfused vessels and thus possibly limiting the O₂ diffusion distance.

High Versus Low Blood-Pressure Target in Experimental Ischemic Prolonged Cardiac Arrest Treated with Extra Corporeal Life Support.

There is currently no recommendation for the mean arterial pressure target in the particular setting of Extracorporeal Cardiopulmonary Resuscitation (ECPR) in the first hours following cardiogenic shock complicated by cardiac arrest. This study aimed to assess the effects of two different levels of mean arterial pressure on macrocirculatory, microcirculatory, and metabolic functions. Randomized animal study. University research laboratory. Ventricular fibrillation was induced in 14 male pigs by surgical ligature of the interventricular coronary artery. After 20 min of cardiopulmonary resuscitation, Extracorporeal Life Support (ECLS) was initiated to restore circulatory flow. Thereafter, animals were randomly allocated to a high mean arterial pressure group (High-MAP, 80-85 mm Hg) or to a standard mean arterial pressure group (Standard-MAP, 65-70 mm Hg). Assessments conducted at baseline, immediately following and 6 h after ECLS initiation were focused on lactate evolution, amount of infused fluid, and microcirculatory parameters. There was no significant difference between the two groups at the time of ECLS initiation and at 6 h with regard to lactate levels (High-MAP vs. Standard-MAP: 8.8 [6.7-12.9] vs. 9.6 [9.1-9.8] mmol·l, P = 0.779 and 8.9 [4.3-11.1] vs. 3.3 [2.4-11] mmol·l, P = 0.603). Infused fluid volume did not significantly differ between the two groups (4,000 [3,500-12,000] vs. 5,000 [2,500-18,000] mL, P = 0.977). There was also no significant difference between the two groups regarding renal and liver functions, and sublingual capillary microvascular flow index assessed by Sidestream Dark Field imaging. Compared with a standard mean arterial pressure regimen, targeting a high mean arterial pressure in the first hours of an experimental ECPR model did not result in any hemodynamic improvement nor in a decrease in the amount of infused fluid.

Effects of Mild Hypothermia on Cerebral Large and Small Microvessels Blood Flow in a Porcine Model of Cardiac Arrest.

The effect of mild hypothermia (MH) on microcirculation after resuscitation from cardiac arrest is controversial. The aim of this study was to determine whether MH improves or aggravates the disturbance of cerebral microcirculation. Twenty domestic male pigs were randomized into the MH group (n=8), non-hypothermia (NH) group (n=8) or sham operation group (n=4). In the MH group, the animals were initiated rapid intravascular cooling at 1h after return of spontaneous circulation (ROSC) from 8min ventricular fibrillation, and the core temperature was reduced to 33°C for 12h and then rewarmed to 37°C. In the NH group, animals did not receive hypothermia treatment after ROSC. In the sham operation group, the same surgical procedure was performed, but without inducing ventricular fibrillation and hypothermia treatment. The cerebral microvascular flow index (MFI) of large microvessel (diameter>20μm) and small microvessel (diameter<20μm) was measured after ROSC. Cerebral oxygen extraction ratio, internal jugular venous-artery lactate difference, and CO2 difference were also calculated. Cerebral MFI dramatically reduced after ROSC, and MH further aggravated the decrease in MFI of small microvessel compared with NH (p<0.05). Internal jugular venous-arterial lactate difference and CO2 difference, and oxygen extraction ratio were all significantly increased after ROSC. MH significantly decreased the values compared with NH (p<0.05). MH decreases cerebral small microvessel blood flow and cerebral metabolism after ROSC compared with NH. However, the total effect is that cerebral oxygen supply-demand relationship is improved during hypothermia.

Changes of small intestinal villi microcirculation in sidestream dark-field imaging with different target blood pressure in rabbits during endotoxin shock

Changes of small intestine villus microcirculation perfusion in sidestream dark-field (SDF) imaging in the rabbits during endotoxic shock after fluid resuscitation with different target mean arterial pressure (MAP), and evaluation of feasibility of monitoring small intestine villus microcirculation by SDF were studied. Sixty standard New Zealand white rabbits were randomly divided into two groups: low target MAP group (group A, n = 30) and high target MAP group (group B, n = 30). Fistula operation of ileum was made in vitro, and lipopolysaccharide (LPS, 2 mg/kg) was injected to establish endotoxic shock model. Group A was administered with the lower dose fluid resuscitation (lactated Ringer solution, 20 mL×kg-1×h-1) for target MAP of 65 mmHg (1 mmHg = 0.133 kPa); group B was administered with the higher dose fluid resuscitation (lactated Ringer solution, 30 mL×kg-1×h-1) for MAP of 80 mmHg. Continuous norepinephrine intravenous injection (0.5-1.0 μg×kg-1×min-1) was administered only after fluid therapy couldn't reach the target MAP. The changes of small intestine villus microcirculation perfusion indexes such as vessels per villus (VV), proportion of perfused villi (PPV), microvascular flow index (MFI), borders of villus score (BVS), vessels villus score (VVS) were continuously observed and recorded before the shock, during the shock and after fluid resuscitation using SDF imaging. The differences of microcirculation perfusion were compared between two groups using the specific parameter evaluation system to determine severity of villi microcirculation and injury scores at different stages. VV and borders of villus were clear and contact before shock in two groups. After shock, VV, PPV were significantly decreased in both two groups, the borders of villus were destroyed, MFI, BVS, VVS and the total score of villi injury microcirculation were obviously and severely decreased. Partial blood flow of villous capillaries after fluid resuscitation was recovered in two groups, but the perfusion of some region was un-balanced with the outworn borders of villus. VV were rose as compared before and after fluid resuscitation in groups A and B (vessels: 1.21±0.22 vs. 0.81±0.12, 1.54±0.28 vs. 0.79±0.13), and PPV [(31±4)% vs. (12±2)%, (38±5)% vs. (13±3)%], MFI (1.55±0.09 vs. 1.09±0.03, 1.97±0.11 vs. 1.05±0.03), VVS (points: 1.22±0.08 vs. 0.89±0.02, 2.06±0.15 vs. 0.90±0.02) and the sum of MFI, BVS, VVS (3.70±0.19 vs. 2.85±0.07, 5.01±0.29 vs. 2.88±0.08) were significant rose (all P < 0.05). The recovery of group B was better than that of group A, and the injury score was reduced. But BVS were not increased in both groups compared with before and after shock (points: 0.93±0.05 vs. 0.87±0.03, 0.98±0.09 vs. 0.93±0.05, both P > 0.05). For the small intestine villus microcirculation perfusion, the higher target MAP (80 mmHg) after fluid resuscitation or/and vasoconstrictor drugs usage were probably better than the relatively lower target MAP (65 mmHg) during endotoxic shock. SDF imaging is a very promising technique for intestinal villi microcirculatory visualization and assessment.

Evaluation of sublingual microcirculation in a paediatric intensive care unit: prospective observational study about its feasibility and utility

BackgroundEvaluation of the microcirculation in critically ill patients is usually done by means of indirect parameters. The aim of our study was to evaluate the functional state of the microcirculation by direct visualization of sublingual microcirculation using Sidestream Dark Field Imaging, to determine the correlation between these findings and other parameters that are commonly used in the clinical practice and to assess the applicability of the systematic use of this technique in critically ill children.MethodsA prospective observational study was carried out in a Pediatric Intensive Care Unit (PICU) of a tertiary referral hospital. All patients admitted to the PICU during a three-month period were included in the study after obtaining the informed consent from the patient. Systematic evaluation of sublingual microcirculation was done in these patients (Total Vessel Density, Proportion of Perfused Vessels, Perfused Vessel Density, De Backer Score, Microvascular Flow Index, Heterogeneity Index) within the first day of admission (T1) and between the second and third day of admission (T2). Other clinical, hemodynamic, and biochemical parameters were measured and registered simultaneously. When the evaluation of the microcirculation was not feasible, the reason was registered. Descriptive analysis of our findings are expressed as means, medians, standard deviations and interquartile ranges. Mann–Whitney-Wilcoxon and Fisher tests were used to compare variables between patients with and without evaluation of the microcirculation. Pearson Correlation Coefficient (ρ) was used to evaluate the correlation between microcirculatory parameters and other clinical parameters.ResultsOne hundred fine patients were included during the study period. Evaluation of the microcirculation was feasible in 18 patients (17.1%). 95.2% of them were intubated. The main reason for not evaluating microcirculation was the presence of respiratory difficulty or the absence of collaboration (95.1% on T1 and 68.9% on T2). Evaluated patients had a higher prevalence of intubation and ECMO at admission (72.2% vs. 14.9% and 16.6% vs. 1.1%, respectively), and longer median duration of mechanical ventilation (0 vs. 6.5 days), vasoactive drugs (0 vs. 3.5 days) and length of stay (3 vs. 16.5 days) than non-evaluated patients. There was a moderate correlation between microcirculatory parameters and systolic arterial pressure, central venous pressure, serum lactate and other biochemical parameters used for motoring critically ill children.ConclusionsSystematic evaluation of microcirculation in critically ill children is not feasible in the unstable critically ill patient, but it is feasible in stable critically ill children. Microcirculatory parameters show a moderate correlation with other parameters that are usually monitored in critically ill children.

Physiological role of erythrocyte nitric oxide.

Nitric oxide (NO) produced by endothelial cells interacts with erythrocyte through band 3 protein, being scavenged by haemoglobin. A signal transduction mechanism involving protein Gi and protein band 3 stimulates erythrocyte NO efflux when acetylcholine (ACh) binds to erythrocyte membrane acetylcholinesterase. Binding of normal plasma fibrinogen (Fib) levels, to erythrocyte membrane CD47 decreases the NO efflux. When high Fib concentration and ACh were present the efflux of NO from erythrocytes was normalized. The increased NO efflux from erythrocytes in presence of high Fib concentration and band 3 phosphorylation is reinforced in the presence of 4N1K an agonist peptide of CD47. When both Fib and 4N1K are present the NO efflux from erythrocytes is higher or not affected according lower or high levels of cAMP. Erythrocyte NO efflux in patients with systemic lupus erythematous and rheumatoid attrite was significantly negative associated with carotid intima-media thickness. In patients with amyotrophic lateral sclerosis erythrocyte NO content is preserved and an inverse association between respiratory function and NO efflux from the erythrocyte was verified. Sepsis patients before dead at 24 h showed higher efflux of NO from erythrocytes that worsening the blood sub lingual microcirculation observed by high unequal blood flow and high microvascular flow index. The in vivo animal models either of inflammation or of hypertension evidenced that the NO efflux from erythrocyte decrease as a compensatory mechanism. All studies conducted since 2000 where we demonstrated the existence NO inside the erythrocyte by fluorescence microscopy, and after their signaling pathway needs more development translational research for news therapeutics and further application in not invasive therapy to vascular inflammatory diseases.

Ability and efficiency of an automatic analysis software to measure microvascular parameters

Analysis of the microcirculation is currently performed offline, is time consuming and operator dependent. The aim of this study was to assess the ability and efficiency of the automatic analysis software CytoCamTools 1.7.12 (CC) to measure microvascular parameters in comparison with Automated Vascular Analysis (AVA) software 3.2. 22 patients admitted to the cardiothoracic intensive care unit following cardiac surgery were prospectively enrolled. Sublingual microcirculatory videos were analysed using AVA and CC software. The total vessel density (TVD) for small vessels, perfused vessel density (PVD) and proportion of perfused vessels (PPV) were calculated. Blood flow was assessed using the microvascular flow index (MFI) for AVA software and the averaged perfused speed indicator (APSI) for the CC software. The duration of the analysis was also recorded. Eighty-four videos from 22 patients were analysed. The bias between TVD-CC and TVD-AVA was 2.20mm/mm2 (95% CI 1.37-3.03) with limits of agreement (LOA) of -4.39 (95% CI -5.66 to -3.16) and 8.79 (95% CI 7.50-10.01)mm/mm2. The percentage error (PE) for TVD was ±32.2%. TVD was positively correlated between CC and AVA (r=0.74, p<0.001). The bias between PVD-CC and PVD-AVA was 6.54mm/mm2 (95% CI 5.60-7.48) with LOA of -4.25 (95% CI -8.48 to -0.02) and 17.34 (95% CI 13.11-21.57)mm/mm2. The PE for PVD was ±61.2%. PVD was positively correlated between CC and AVA (r=0.66, p<0.001). The median PPV-AVA was significantly higher than the median PPV-CC [97.39% (95.25, 100%) vs. 81.65% (61.97, 88.99), p<0.0001]. MFI categories cannot estimate or predict APSI values (p=0.45). The time required for the analysis was shorter with CC than with AVA system [2'42″ (2'12″, 3'31″) vs. 16'12″ (13'38″, 17'57″), p<0.001]. TVD is comparable between the two softwares, although faster with CC software. The values for PVD and PPV are not interchangeable given the different approach to assess microcirculatory flow.

Microcirculatory changes in children undergoing cardiac surgery: a prospective observational study

BackgroundThe effects of cardiac surgery on the microcirculation of children are unknown. The aim of this study was to assess the microcirculatory changes in children undergoing surgery for correction of congenital heart disease. MethodsWe used a videomicroscope (Sidestream Dark Field, SDF) in a convenience sample of 24 children <five yr old. Total vascular density (TVD, vessels mm−2), microvascular flow index (MFI, arbitrary units), proportion of perfused small vessels (PPV, percentage), and perfused vessel density (PVD) were obtained after induction of anaesthesia (T1), at the end of the surgical procedure (T2), after intensive care unit (ICU) admission (T3), and at six h (T4) and 12h (T5) after ICU admission. ResultsMicrocirculatory variables did not significantly change over time. Haemodynamic parameters and microcirculatory variables were not correlated. In a subanalysis conducted for cyanotic (n=7) and acyanotic (n=17) children, repeated measures ANOVA showed a significant interaction between time and the presence of cyanosis for PPV (P=0.03), TVD (P=0.03), and PVD (P=0.03). Weak inverse correlations were found between storage time of transfused red blood cell (RBCs) and MFI at T3 (r=−0.63, P=0.01) and T4 (r=−0.53, P=0.03). ConclusionsMicrocirculatory variables have a different time-related trend in cyanotic and acyanotic children undergoing cardiac surgery. The storage time of transfused RBCs seems to negatively impact the microcirculation. Further and larger studies are warranted to prove the potential implications of this study.

Conjunctival microcirculatory blood flow is altered but not abolished in brain dead patients: a prospective observational study.

BackgroundThe conjunctival microcirculation has potential as a window to cerebral perfusion due to related blood supply, close anatomical proximity and easy accessibility for microcirculatory imaging technique, such as sidestream dark field (SDF) imaging. Our study aims to evaluate conjunctival and sublingual microcirculation in brain dead patients and to compare it with healthy volunteers in two diametrically opposed conditions: full stop versus normal arterial blood supply to the brain.MethodsIn a prospective observational study we analyzed conjunctival and sublingual microcirculation using SDF imaging in brain dead patients after reaching systemic hemodynamic targets to optimize perfusion of donor organs, and in healthy volunteers. All brain death diagnoses were confirmed by cerebral angiography. Microcirculatory images were obtained and analyzed using standardized published recommendations. Study registered at ClinicalTrials.gov, number NCT02483273.ResultsEleven brain dead patients and eleven apparently healthy controls were enrolled in the study. Microvascular flow index (MFI) of small vessels was significantly lower in brain dead patients in comparison to healthy controls in ocular conjunctiva (2.7 [2.4–2.9] vs. 3.0 [2.9–3.0], p = 0.01) and in sublingual mucosa (2.8 [2.6–2.9] vs. 3.0 [2.9–3.0], p = 0.02). Total vessel density (TVD) and perfused vessel density (PVD) of small vessels were significantly lower in brain dead patients in comparison to healthy controls in ocular conjunctiva (10.2 [6.6–14.8] vs. 18.0 [18.0–25.4] mm/mm2, p = 0.001 and 5.0 [3.5–7.3] vs. 10.9 [10.9–13.5] 1/mm, p = 0.001), but not in sublingual mucosa.ConclusionIn comparison to healthy controls brain dead patients had a significant reduction in conjunctival microvascular blood flow and density. However, the presence of conjunctival flow in case general cerebral flow is completely absent makes it impossible to use the conjunctival microcirculation as a substitute for brain flow, and further research should focus on the link between the ocular microcirculation, intracranial pressure and alternative ocular circulation.

Microcirculatory blood flow during cardiac arrest and cardiopulmonary resuscitation does not correlate with global hemodynamics: an experimental study.

BackgroundCurrent research highlights the role of microcirculatory disorders in post-cardiac arrest patients. Affected microcirculation shows not only dissociation from systemic hemodynamics but also strong connection to outcome of these patients. However, only few studies evaluated microcirculation directly during cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). The aim of our experimental study in a porcine model was to describe sublingual microcirculatory changes during CA and CPR using recent videomicroscopic technology and provide a comparison to parameters of global hemodynamics.MethodsCardiac arrest was induced in 18 female pigs (50 ± 3 kg). After 3 min without treatment, 5 min of mechanical CPR followed. Continuous hemodynamic monitoring including systemic blood pressure and carotid blood flow was performed and blood lactate was measured at the end of baseline and CPR. Sublingual microcirculation was assessed by the Sidestream Dark Field (SDF) technology during baseline, CA and CPR. Following microcirculatory parameters were assessed off-line separately for capillaries (≤20 µm) and other vessels: total and perfused vessel density (TVD, PVD), proportion of perfused vessels (PPV), microvascular flow index (MFI) and heterogeneity index (HI).ResultsIn comparison to baseline the CA small vessel microcirculation was only partially preserved: TVD 15.64 (13.59–18.48) significantly decreased to 12.51 (10.57–13.98) mm/mm2, PVD 15.57 (13.56–17.80) to 5.53 (4.17–6.60) mm/mm2, PPV 99.64 (98.05–100.00) to 38.97 (27.60–46.29) %, MFI 3.00 (3.00–3.08) to 1.29 (1.08–1.58) and HI increased from 0.08 (0.00–0.23) to 1.5 (0.71–2.00), p = 0.0003 for TVD and <0.0001 for others, respectively. Microcirculation during ongoing CPR in small vessels reached 59–85 % of the baseline values: TVD 13.33 (12.11–15.11) mm/mm2, PVD 9.34 (7.34–11.52) mm/mm2, PPV 72.34 (54.31–87.87) %, MFI 2.04 (1.58–2.42), HI 0.65 (0.41–1.07). The correlation between microcirculation and global hemodynamic parameters as well as to lactate was only weak to moderate (i.e. Spearman’s ρ 0.02–0.51) and after adjustment for multiple correlations it was non-significant.ConclusionsSublingual microcirculatory parameters did not correlate with global hemodynamic parameters during simulated porcine model of CA and CPR. SDF imaging provides additional information about tissue perfusion in the course of CPR.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-016-0934-5) contains supplementary material, which is available to authorized users.

Analysis of microcirculation measurements by novice users trained by a standardized interactive tutorial: An inter-observer variability study.

Excessive time for analysis may impede microcirculatory studies with large amounts of video data. Engaging more personnel in the analyses seems to be a rational approach in that scenario and could shorten the time-interval between capturing images and obtaining results. Our hypothesis was that novice users would be able to determine standard microcirculatory parameters using a semi-automated software with an acceptable degree of variability after participating in a standardized interactive training session. 14 volunteers were included in the study. All volunteers analyzed separately the same sample video after the training. The kappa statistic was calculated for the primary outcome parameter microvascular flow index (MFI) within small and large vessels and indicated a fair level of agreement in the results of the novice users. A standardized interactive tutorial can be useful to teach microcirculatory analysis in previously untrained subjects.

Sidestream dark field imaging of the serosal microcirculation during gastrointestinal surgery.

The study aimed to describe the serosal microcirculation of the human bowel using sidestream dark field imaging, a microscopic technique using polarized light to visualize erythrocytes through capillaries. We also compared its feasibility to the current practice of sublingual microcirculatory assessment. In 17 patients sidestream dark field measurements were performed during gastrointestinal surgery. Microcirculatory parameters like microvascular flow index (MFI), proportion of perfused vessels (PPV), perfused vessel density (PVD) and total vessel density (TVD) were determined for every patient, sublingually and on the bowel serosa. Sixty measurements were done on the bowel of which eight (13%) were excluded, five owing to too much bowel peristalsis and three because of pressure artefacts. Image stability was in favour of sublingual measurements [pixel loss per image, bowel 145 (95% CI 126-164) vs sublingual 55 (95% CI 41-68); P < 0.001] and time to acquire a stable image [bowel 96 s (95% CI 63-129) vs. sublingual 46 s (95% CI 29-64); P = 0.013]. No difference in the MFI was observed [bowel 2.9 (interquartile range 2.87-2.95) vs sublingual 3.0 (interquartile range 2.91-3.0); P = 0.081]. There was a difference in the PPV [bowel 95% (95% CI 94-96) vs sublingual 97% (95% CI 97-99); P < 0.001], PVD [bowel 12.9 mm/mm2 (95% CI 11.1-14.8) vs sublingual 17.4 mm/mm2 (95% CI 15.6-19.1); P = 0.003] and the TVD [bowel 13.6 mm/mm2 (95% CI 11.6-15.6) vs sublingual 17.7 mm/mm2 (95% CI 16.0-19.4); P = 0.008]. Sidestream dark field imaging is a very promising technique for bowel microcirculatory visualization and assessment. It is comparable to sublingual assessment and the analysis produces a similar outcome with slightly differing anatomical features.