Sublingual Microvascular Perfusion Research Articles

Microcirculation-guided resuscitation in sepsis: the next frontier?

Microcirculatory dysfunction plays a key role in the pathogenesis of tissue dysoxia and organ failure in sepsis. Sublingual videomicroscopy techniques enable the real-time non-invasive assessment of microvascular blood flow. Alterations in sublingual microvascular perfusion were detected during sepsis and are associated with poor outcome. More importantly, sublingual videomicroscopy allowed to explore the effects of commonly applied resuscitative treatments in septic shock, such as fluids, vasopressors and inotropes, and showed that the optimization of macro-hemodynamic parameters may not be accompanied by an improvement in microvascular perfusion. This loss of "hemodynamic coherence," i.e., the concordance between the response of the macrocirculation and the microcirculation, advocates for the integration of microvascular monitoring in the management of septic patients. Nonetheless, important barriers remain for a widespread use of sublingual videomicroscopy in the clinical practice. In this review, we discuss the actual limitations of this technique and future developments that may allow an easier and faster evaluation of the microcirculation at the bedside, and propose a role for sublingual microvascular monitoring in guiding and titrating resuscitative therapies in sepsis.

Association of Preoperative Basal Inflammatory State, Measured by Plasma suPAR Levels, with Intraoperative Sublingual Microvascular Perfusion in Patients Undergoing Major Non-Cardiac Surgery.

It remains unknown whether chronic systemic inflammation is associated with impaired microvascular perfusion during surgery. We evaluated the association between the preoperative basal inflammatory state, measured by plasma soluble urokinase-type plasminogen activator receptor (suPAR) levels, and intraoperative sublingual microcirculatory variables in patients undergoing major non-cardiac surgery. Plasma suPAR levels were determined in 100 non-cardiac surgery patients using the suPARnostic® quick triage lateral flow assay. We assessed sublingual microcirculation before surgical incision and every 30 min during surgery using Sidestream Darkfield (SDF+) imaging and determined the De Backer score, the Consensus Proportion of Perfused Vessels (Consensus PPV), and the Consensus PPV (small). Elevated suPAR levels were associated with lower intraoperative De Backer score, Consensus PPV, and Consensus PPV (small). For each ng mL−1 increase in suPAR, De Backer score, Consensus PPV, and Consensus PPV (small) decreased by 0.7 mm−1, 2.5%, and 2.8%, respectively, compared to baseline. In contrast, CRP was not significantly correlated with De Backer score (r = −0.034, p = 0.36), Consensus PPV (r = −0.014, p = 0.72) or Consensus PPV Small (r = −0.037, p = 0.32). Postoperative De Backer score did not change significantly from baseline (5.95 ± 3.21 vs. 5.89 ± 3.36, p = 0.404), while postoperative Consensus PPV (83.49 ± 11.5 vs. 81.15 ± 11.8, p < 0.001) and Consensus PPV (small) (80.87 ± 13.4 vs. 78.72 ± 13, p < 0.001) decreased significantly from baseline. In conclusion, elevated preoperative suPAR levels were associated with intraoperative impairment of sublingual microvascular perfusion in patients undergoing elective major non-cardiac surgery.

Endothelial glycocalyx integrity and microvascular perfusion are associated with novel echocardiographic markers and carotid intima-media thickness in patients with psoriasis

Abstract Background/Introduction Psoriasis has been associated with vascular and myocardial dysfunction through mechanisms of inflammation and oxidative stress. Purpose We aimed to evaluate sublingual microvascular perfusion and glycocalyx barrier properties in psoriasis patients, as well as their correlation with coronary microcirculatory function and markers of myocardial deformation and atherosclerosis (carotid intima-media thickness, cIMT). Methods We examined 297 patients with psoriasis and 150 controls, adjusted for age, sex, and atherosclerotic risk factors. Perfusion boundary region (PBR), a marker of glycocalyx barrier function, was measured non-invasively in sublingual microvessels with a diameter ranging from 5–25μm using a dedicated camera (Sidestream Dark Field imaging, Microscan, GlycoCheck). Increased PBR indicates reduced glycocalyx thickness. Indexes of microvascular perfusion, including red blood cell (RBC) filling percentage and functional microvascular density, were also calculated. We measured coronary flow reserve (CFR), cIMT and markers of myocardial deformation by speckle tracking imaging utilizing echocardiography [peak twisting, the percentage changes between peak twisting, and untwisting at mitral valve opening (%dpTw-UtwMVO), at peak (%dpTw-UtwPEF), and the end of early LV diastolic filling (%dpTw-UtwEDF)]. Results Psoriasis patients had higher PBR5–25 compared to controls (2.13±0.29 versus 1.78±0.25μm, p&amp;lt;0.05). There was an inverse association of PBR5–25 with perfused microvascular density (r=−0.42, p&amp;lt;0.001) and RBC fraction (r=−0.80, p&amp;lt;0.001). In psoriatic population, PBR5–25 was inversely correlated to CFR (r=−0.30, p=0.045). Increased values of PBR5–9 were associated with reduced untwisting at the end of the mitral inflow E wave (r=−0.24, p=0.006) and reduced %dpTw-UtwMVO (r=−0.35, p&amp;lt;0.001). Furthermore, decreased RBC filling percentage and perfused microvascular density were related to worse LV longitudinal strain and increased cIMT (p&amp;lt;0.05). Finally, a positive correlation between perfused microvascular density and %dpTw-UtwMVO was observed in patients with psoriasis (p&amp;lt;0.05). Conclusion Endothelial glycocalyx thickness is reduced in patients with psoriasis and is associated with impaired coronary and myocardial function, and vascular atherosclerosis. Funding Acknowledgement Type of funding sources: None.

Association of endothelial glycocalyx integrity and microvascular perfusion with novel echocardiographic markers and carotid intima-media thickness in patients with psoriasis

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Psoriasis has been associated with vascular and myocardial dysfunction through mechanisms of inflammation and oxidative stress. Purpose We aimed to evaluate sublingual microvascular perfusion and glycocalyx barrier properties in psoriasis patients, as well as their correlation with coronary microcirculatory function, markers of myocardial deformation and atherosclerosis (carotid intima-media thickness, IMT). Methods We examined 241 patients with psoriasis and 160 controls, adjusted for age, sex, BMI, smoking, LV mass, heart rate, hyperlipidemia, and office SBP. Perfusion boundary region (PBR), a marker of glycocalyx barrier function, was measured non-invasively in sublingual microvessels with a diameter ranging from 5-25 µm using a dedicated camera (Side field dark imaging, Micrsoscan, Nedelrands). Increased PBR indicates reduced glycocalyx thickness. Indexes of microvascular perfusion, including red blood cell (RBC) filling percentage and functional microvascular density, were also calculated. We measured coronary flow reserve (CFR), carotid IMT and markers of myocardial deformation by speckle tracking imaging utilizing echocardiography [peak twisting, the percentage changes between peak twisting, and untwisting at mitral valve opening (%dpTw – UtwMVO), at peak (%dpTw – UtwPEF), and the end of early LV diastolic filling (%dpTw – UtwEDF)]. Results Psoriasis patients had higher PBR (PBR5-25: 2.131 ± 0.296 vs. 1.769 ± 0.306; PBR5-9: 1.183 ± 0.150 vs. 1.051 ± 0.132; PBR10-19: 2.318 ± 0.581 vs. 1.993 ± 0.365; PBR20-25: 2.650 ± 0.461 vs. 2.269 ± 0.492, all p &amp;lt; 0.05) and impaired LV twisting-untwisting markers compared to controls (pTw: 14.8 ± 7.8 vs. 13.9 ± 3.5; UtwMVO: 10.3 ± 7.3 vs. 9 ± 4.3; %dpTw – UtwMVO: 31 ± 4.1 vs. 38 ± 7; pTwVel: 105 ± 83 vs. 89 ± 21; pUtwVel: -100 ± 53 vs. -93 ± 31, all p &amp;lt; 0.05). In psoriatic population, levels of PBR5-25 and PBR10-19 were inversely correlated to CFR (r=-0.15 and r=-0.17). The first one was also reversely related to peak LV untwisting at aortic valve closure (r=-0.14). Increased levels of PBR5-9 were associated with reduced untwisting at end of the mitral inflow E wave (UtwEDF, r=-0.13) and reduced percentage difference between peak twisting and untwisting at MVO (%dpTw-UntwMVO) (r=-0.15). Furthermore, decreased RBC filling percentage and perfused microvascular density were related to worse LV longitudinal strain (4-chamber) (r=-0.15), and increased IMT (r=-0.14). Finally, a positive correlation between perfused microvascular density and %dpTw-UntwMVO was observed in patients with psoriasis (r = 0.14). All correlations were statistically significant (p &amp;lt; 0.05). Conclusion Endothelial glycocalyx thickness is reduced in patients with psoriasis and is associated with impaired coronary and myocardial function, and vascular atherosclerosis.

Noninvasive sublingual microvascular imaging reveals sex-specific reduction in glycocalyx barrier properties in patients with coronary artery disease.

BackgroundRisk factors for coronary artery disease (CAD) have been associated with endothelial dysfunction and degradation of the endothelial glycocalyx. This study was designed to compare sublingual microvascular perfusion and glycocalyx barrier properties in CAD patients and controls using noninvasive side stream darkfield imaging.MethodsImaging of the sublingual microvasculature was performed in 52 case subjects (CAD confirmed by left heart catheterization) and 63 controls (low Framingham risk score). Red blood cell (RBC) filling percentage and functional microvascular density, measures of microvascular perfusion, and perfused boundary region (PBR), an index of glycocalyx barrier function, were measured in microvessels with a diameter ranging from 5–25 µm.ResultsRBC filling percentage was lower in patients with CAD compared to controls (p < .001). Functional microvascular density did not differ between groups. The overall PBR was marginally greater in the CAD group compared to the control group (p = .08). PBR did not differ between male CAD cases and controls (p = .17). However, PBR was greater in females with CAD compared with female controls (p = .04), indicating reduced glycocalyx barrier function. This difference became more pronounced after adjusting for potential confounders.ConclusionsOur data suggest that patients with CAD are characterized by a reduction in percentage of time microvessels are occupied by RBCs. In addition, CAD is significantly associated with impaired sublingual microvascular glycocalyx barrier function in women but not men. More research is needed to determine the significance of peripheral microvascular dysfunction in the pathophysiology of CAD, and how this may differ by sex.

IgM-enriched immunoglobulins (Pentaglobin) may improve the microcirculation in sepsis: a pilot randomized trial

BackgroundPolyclonal or IgM-enriched immunoglobulins may be beneficial during sepsis as an adjuvant immunomodulatory therapy. We aimed to test whether the infusion of IgM-enriched immunoglobulins improves microvascular perfusion during sepsis.MethodsSingle-centre, randomized, double-blind, placebo-controlled phase II trial including adult patients with a diagnosis of sepsis or septic shock for less than 24 h. Patients received an intravenous infusion of 250 mg/kg (5 mL/kg) per day of IgM-enriched immunoglobulins (Pentaglobin, n = 10) for 72 h or placebo (NaCl 0.9%, n = 9). At baseline and after 24 and 72 h of infusion, the sublingual microcirculation was assessed with Incident Dark Field videomicroscopy. Thenar near-infrared spectroscopy (NIRS) was applied with a vascular occlusion test to assess tissue oxygenation and microvascular reactivity. Levels of interleukin (IL) 1-beta, IL-6, IL-8, IL-10 and tumour necrosis factor alpha were measured in the serum.ResultsThe perfused vessel density (PVD) for small vessels (diameter < 20 micron) increased in the Pentaglobin group (from 21.7 ± 4.7 to 25.5 ± 5.1 mm/mm2) and decreased in the placebo group (from 25 ± 5.8 to 20.7 ± 4.1 mm/mm2, p for interaction < 0.001, two-way analysis of variance). The absolute between-group difference at 72 h was 4.77 (standard error 2.34), p = 0.140. The microvascular flow index for small vessels increased at 24 h in the Pentaglobin group (from 2.68 [2.38–2.78] to 2.93 [2.82–3], p < 0.01) and decreased at 72 h in the placebo group (from 2.83 [2.60–2.97] to 2.67 [2.48–2.73], p < 0.05). Changes in general parameters, cytokines and NIRS-derived parameters were similar between the two groups, except for IL-6 and IL-10 that significantly decreased at 72 h only in the Pentaglobin group.ConclusionsA 72-h infusion of IgM-enriched immunoglobulins (Pentaglobin) in patients with sepsis or septic shock may be associated with an increase in sublingual microvascular perfusion. Further studies are needed to confirm our findings.Trial registration NCT02655133, www.ClinicalTrials.gov, date of registration 7th January 2016, https://www.clinicaltrials.gov/ct2/show/NCT02655133.

Imaging sublingual microcirculatory perfusion in pediatric patients receiving procedural sedation with propofol: A pilot study.

ObjectiveProcedural sedation with propofol is widely used in the pediatric population. A well‐known side effect of propofol is a decrease in peripheral vascular resistance resulting in hypotension, but little is known about the effects on microcirculation in humans. We aimed to evaluate the effects of propofol on the sublingual microcirculatory perfusion by continuous video imaging in pediatric patients undergoing procedural sedation.MethodsPatients admitted to the Pediatric Intensive Care Unit for procedural sedation were recruited. Oral microcirculation was measured employing a continuous monitoring strategy with incident dark‐field illumination imaging. Measurements were obtained before and 3 minutes after propofol induction. Total and perfused vessel densities, proportion of perfused vessels, microvascular flow index, blood vessel diameter (Øbv), and systemic hemodynamics were analyzed.ResultsContinuous measurements were achieved in seven patients. Three minutes after propofol induction mean arterial pressure decreased (P = 0.028) and total and perfused vessel densities increased by 12% (P = 0.018) and 16% (P = 0.018), respectively. MFI was unaltered and mean Øbv increased but not significantly.ConclusionsPropofol induction induces a reduction in mean arterial pressure and a rise in sublingual microvascular perfusion. The observed effects of propofol on the sublingual microcirculation may be due to a decrease in microvascular resistance.

Sublingual microvascular perfusion is altered during normobaric and hyperbaric hyperoxia

Hyperoxia and hyperbaric oxygen therapy can restore oxygen tensions in tissues distressed by ischemic injury and poor vascularization and is believed to also yield angiogenesis and regulate tissue perfusion. The aim of this study was to develop a model in which hyperoxia-driven microvascular changes could be quantified and to test the hypothesis that microcirculatory responses to both normobaric (NB) and hyperbaric (HB) hyperoxic maneuvers are reversible. Sublingual mucosa microcirculation vessel density, proportion of perfused vessels, vessel diameters, microvascular flow index, macrohemodynamic, and blood gas parameters were examined in male rabbits breathing sequential O2/air mixtures of 21%, 55%, 100%, and return to 21% during NB (1.0bar) and HB (2.5bar) conditions. The results indicate that NB hyperoxia (55% and 100%) produced significant decreases in microvascular density and vascular diameters (p<0.01 and p<0.05, respectively) accompanied by significant increases in systolic and mean arterial blood pressure (p<0.05, respectively) with no changes in blood flow indices when compared to NB normoxia. HB normoxia/hyperoxia resulted in significant decreases in microvascular density (p<0.05), a transient rise in systolic blood pressure at 55% (p<0.01), and no changes in blood vessel diameter and blood flow indices when compared to NB hyperoxia. All microcirculation parameters reverted back to normal values upon return to NB normoxia. We conclude that NB/HB hyperoxia-driven changes elicit reversible physiological control of sublingual mucosa blood perfusion in the presence of steady cardiovascular function and that the absence of microvascular vasoconstriction during HB conditions suggests a beneficial mechanism associated with maintaining peak tissue perfusion states.

Evaluation of Microvascular Perfusion and Resuscitation after Severe Injury

Achieving adequate perfusion is a key goal of treatment in severe trauma; however, tissue perfusion has classically been measured by indirect means. Direct visualization of capillary flow has been applied in sepsis, but application of this technology to the trauma population has been limited. The purpose of this investigation was to compare the efficacy of standard indirect measures of perfusion to direct imaging of the sublingual microcirculatory flow during trauma resuscitation. Patients with injury severity scores >15 were serially examined using a handheld sidestream dark-field video microscope. In addition, measurements were also made from healthy volunteers. The De Backer score, a morphometric capillary density score, and total vessel density (TVD) as cumulative vessel area within the image, were calculated using Automated Vascular Analysis (AVA3.0) software. These indices were compared against clinical and laboratory parameters of organ function and systemic metabolic status as well as mortality. Twenty severely injured patients had lower TVD (X = 14.6 ± 0.22 vs 17.66 ± 0.51) and De Backer scores (X = 9.62 ± 0.16 vs 11.55 ± 0.37) compared with healthy controls. These scores best correlated with serum lactate (TVD R(2) = 0.525, De Backer R(2) = 0.576, P < 0.05). Mean arterial pressure, heart rate, oxygen saturation, pH, bicarbonate, base deficit, hematocrit, and coagulation parameters correlated poorly with both TVD and De Backer score. Direct measurement of sublingual microvascular perfusion is technically feasible in trauma patients, and seems to provide real-time assessment of microcirculatory perfusion. This study suggests that in severe trauma, many indirect measurements of perfusion do not correlate with microvascular perfusion. However, visualized perfusion deficiencies do reflect a shift toward anaerobic metabolism.

Administration of tetrahydrobiopterin improves the microcirculation and outcome in an ovine model of septic shock*

Supplementation with tetrahydrobiopterin, a nitric oxide synthase cofactor, may reduce microvascular endothelial dysfunction in severe sepsis. We studied whether tetrahydrobiopterin administration exerts beneficial effects in an ovine septic shock model. Randomized animal study. University hospital animal research laboratory. Fourteen adult female sheep. Fecal peritonitis was induced, and the sheep were randomized to receive tetrahydrobiopterin (n=7), given intravenously as 20 mg/kg boluses at 4 and 12 hrs after sepsis induction, or placebo (n=7). All animals were fluid resuscitated. The experiment was continued until death or for a maximum of 30 hrs. In addition to standard hemodynamic assessment, the sublingual microcirculation was evaluated using sidestream dark-field videomicroscopy. The first bolus of tetrahydrobiopterin blunted the increase in heart rate and cardiac index seen in the control group without affecting mean arterial pressure, and the second bolus of tetrahydrobiopterin prevented the decreases in cardiac index and mean arterial pressure. The reduction in mixed venous blood oxygen saturation and the increase in blood lactate seen in the control group were also delayed. Tetrahydrobiopterin significantly attenuated the deterioration in perfused small vessel proportion and density, microvascular flow index, and the increase in microvascular heterogeneity observed in the control group. Tetrahydrobiopterin was associated with better preserved lung compliance and PaO2/FIO2 ratio, which were associated with a lower lung wet/dry weight ratio at the end of the study. Median survival time was significantly prolonged in the tetrahydrobiopterin group (25.0 vs. 17.8 hrs, p<.01). In this clinically relevant model of sepsis, tetrahydrobiopterin supplementation attenuated the impairment in sublingual microvascular perfusion and permeability, which was accompanied by better preserved gas exchange, renal flow and urine output, and prolonged survival.

Electrical Cardioversion for Atrial Fibrillation Improves Microvascular Flow Independent of Blood Pressure Changes

This study tested the hypothesis that there is a discrepancy between global hemodynamic parameters and microvascular flow in patients before and after successful elective electrical cardioversion (ECV) for atrial fibrillation (AF). Prospective observational study. Preanesthesia holding area in a teaching hospital. Adult patients who underwent successful elective ECV for AF. ECV. Routine measurements of heart rate and noninvasive blood pressure were recorded and the sublingual microcirculation was visualized by sidestream darkfield imaging before and after the conversion of AF to sinus rhythm by elective ECV. The conversion to sinus rhythm significantly improved the microvascular flow index for smaller and larger microvessels. For smaller microvessels, perfused vessel density did not reach significance after conversion to sinus rhythm, whereas the proportion of perfused vessels was significantly larger and indices of heterogeneity for microvascular flow index decreased significantly. No correlation could be identified for the changes in mean blood pressure, perfused vessel density, and microvascular flow index for smaller microvessels. Successful ECV in patients with AF improves indices of sublingual microvascular perfusion. This change has no clear relation to the change in blood pressure and cannot be predicted from it. It may be prudent not to rely solely on global hemodynamic parameters to assess end-organ perfusion in this setting.

Microvascular Response to Red Blood Cell Transfusion in Trauma Patients

Trauma patients are often transfused allogeneic red blood cells (RBCs) in an effort to augment tissue oxygen delivery. However, the effect of RBC transfusion on microvascular perfusion in this patient population is not well understood. To this end, we investigated the effect of RBC transfusion on sublingual microvascular perfusion in trauma patients. Sublingual microcirculation was imaged at bedside with a sidestream dark-field illumination microscope before and after transfusion of one RBC unit in hemodynamically stable, anemic trauma patients. The perfused proportion of capillaries (PPC) before and after transfusion was determined, and the percent change in capillary perfusion following transfusion (ΔPPC) calculated. Sublingual microcirculation was observed in 30 patients. Mean age was 47 (SD, 21) years, mean Injury Severity Score was 29 (SD, 16), and mean pretransfusion hemoglobin was 7.5 (SD, 0.9) g/dL. No patients had a mean arterial pressure of less than 65 mmHg (mean, 89 [SD, 17] mmHg) or lactate of greater than 2.5 mmol/L (mean, 1.1 [SD, 0.3] mmol/L). Following transfusion, ΔPPC ranged from +68% to -36% and was found to inversely correlate significantly with pretransfusion PPC (Spearman r = -0.63, P = 0.0002). Pretransfusion PPC may be selectively deranged in otherwise stable trauma patients. Patients with relatively altered baseline PPC tend to demonstrate improvement in perfusion following transfusion, whereas those with relatively normal perfusion at baseline tend to demonstrate either no change or, in fact, a decline in PPC. Bedside sublingual imaging may have the potential to detect subtle perfusion defects and ultimately inform clinical decision making with respect to transfusion.

Sublingual tissue perfusion improves during emergency treatment of acute decompensated heart failure

ObjectivesThe aim of this study was to measure sublingual perfused capillary density (PCD) to assess sublingual microvascular perfusion during emergency department (ED) treatment of acute decompensated heart failure (ADHF). MethodsThis prospective, observational study enrolled ED patients with ADHF, measuring pre- and post-ED treatment PCD. Sidestream dark-field imaging was analyzed by 3 investigators blinded to patient identifiers and time points. Patient demographics, ADHF etiology, serum brain natriuretic peptide, and hemoglobin were measured along with a visual analogue scale (VAS), which assessed patient baseline characteristics and response to ED treatment. A paired t test analyzed changes in PCD, mean arterial pressure (MAP), and patient assessment. Interrater variability was assessed with an intraclass correlation coefficient (ICC), with a P value <.05 considered significant for all testing. ResultsThirty-six patients were enrolled with a mean time between pretreatment and posttreatment PCD (±SD) of 138 ± 59 minutes and a hospital length of stay of 4.0 ± 4.1 days. During this time, PCD increased (difference, 1.3 mm/mm2; 95% confidence interval, 0.4-2.1; P = .004), as did the MAP (P = .002), patient VAS score (P < .001), and observer VAS score (P < .001). There was no correlation between the change in PCD and time (R2 = .016, P = .47), MAP (R2 = .013, P = .54), or VAS scores. The ICC was 0.954. ConclusionsSublingual tissue perfusion is diminished in ADHF but increases with treatment. It may represent a quantitative way to evaluate ADHF in the ED setting.

Changes in Microvascular Blood Flow during Coupled Plasma Filtration and Adsorption

A 51-year-old man with septic shock underwent three consecutive sessions of coupled plasma filtration-adsorption each lasting 12 hours. Sublingual microvascular perfusion was assessed using the orthogonal polarisation spectral imaging technique at three different times: immediate pre-coupled plasma filtration-adsorption phase, two hours following commencement and two hours after its termination. The video images of the sublingual microcirculation were analysed by an investigator blinded to the time of image acquisition. The De Backer's score was calculated. During the coupled plasma filtration-adsorption, the number of perfused vessels increased compared with the pre-coupled plasma filtration-adsorption period, but decreased again after its termination. It is arguable that the elimination of septic mediators during the procedure could account for the observed variations.

Changes in the volume status of haemodialysis patients are reflected in sublingual microvascular perfusion

After the introduction of sidestream darkfield imaging (SDF) of the microcirculation, it has become clear that in sepsis, microcirculatory alterations can exist in the absence of systemic haemodynamic abnormalities. However, it is unclear whether this phenomenon also occurs in the treatment of end-stage kidney disease (ESKD) where alterations in the volume status of patients occur during dialysis. We tested the hypothesis that volume changes during dialysis directly affect the perfusion of the microcirculation in a group of adult haemodialysis patients. Secondly, we evaluated microcirculatory response to autotransfusion using the Trendelenburg position (TP). Patients who were on chronic intermittent haemodialysis were assessed for sublingual microvascular flow by SDF imaging pre- and post-TP, performed before and after ultrafiltration (UF). Sublingual microvascular flow was estimated using a semi-quantitative microvascular flow index (MFI) in small (diameter <25 microm, which includes capillaries), medium (25-50 microm) and large-sized (50-100 microm) microvessels (no flow: 0, intermittent flow: 1, sluggish flow: 2 and continuous flow: 3). Changes were evaluated with the non-parametric paired Wilcoxon test. P < 0.05 was judged to indicate a significant difference. Thirty-nine adult patients took part in the study. The underlying diseases causing ESKD were predominantly hypertension (HT, n = 10), diabetes mellitus (DM, n = 7) or both (n = 3). At the start of UF, microvascular flow did not change significantly by TP. After completion of UF, MFI had decreased significantly in all types of microvessels (P < 0.001). After UF (median volume extraction 2.49l), MFI was lower than that at the start of UF and increased in most patients after TP (P < 0.001) in all categories of vessels. Changes were most prominent in the smallest microvessels. Sublingual microvascular perfusion is reduced by UF and can be restored temporarily using autotransfusion by TP due to increased venous return. SDF imaging is able to detect these volume changes. SDF imaging and TP could become a useful bedside tool to evaluate the patient's (microvascular) volume status and response to therapy in dialysis or intradialytic hypotension.

Low‐dose nitroglycerin improves microcirculation in hospitalized patients with acute heart failure

Impaired tissue perfusion is often observed in patients with acute heart failure. We tested whether low-dose nitroglycerin (NTG) improves microcirculatory perfusion in patients admitted for acute heart failure. In 20 acute heart failure patients, NTG was given as intravenous infusion at a fixed dose of 33 microg/min. Using Sidestream Dark Field (SDF) imaging, sublingual microvascular perfusion was evaluated before (T0, average of two baseline measurements) and 15 min after initiation of NTG (T1). In a subgroup of seven patients, SDF measurements were repeated after NTG had been stopped for 20 min. Capillaries were defined as microvessels with a diameter of <20 microm. Perfused capillary density (PCD) was determined as the parameter of tissue perfusion. Values are expressed as median and interquartile range (P25; P75). The median age of the subjects was 60 (52; 73) years, and 65% were male. Patients were stable before starting NTG. Nitroglycerin decreased central venous pressure [17 (13; 19) mmHg at T0 vs. 16 (13; 17) mmHg at T1, P = 0.03] and pulmonary capillary wedge pressure [23 (18; 31) mmHg at T0 vs. 19 (16; 25) mmHg at T1, P = 0.03]. It increased PCD [10.7 (9.9; 12.5) mm mm(-2) at T0 vs. 12.4 (11.4; 13.6) mm mm(-2) at T1, P = 0.01]. After cessation of NTG, PCD returned to baseline values (P = 0.04). Low-dose NTG significantly reduces cardiac filling pressures and improves microvascular perfusion in patients admitted for acute heart failure.

Impaired sublingual microvascular perfusion during surgery with cardiopulmonary bypass: A pilot study

Complications after cardiac surgery may involve multiple organ failure, which carries a high mortality. Development of multiple organ failure may be related to impaired microcirculatory perfusion as a result of systemic inflammation. Microcirculatory blood flow alterations have been associated with impaired outcome. We investigated whether these alterations occurred before, during, and after coronary artery bypass grafting. We observed 25 consecutive patients who underwent elective coronary artery bypass grafting with cardiopulmonary bypass. The sublingual microcirculation was investigated using side-stream dark-field imaging. Side-stream dark-field imaging was performed before (baseline), during, and after surgery. Microvascular blood flow was estimated with a semiquantitative microvascular flow index in small, medium, and large microvessels. Changes in microvascular flow were tested with Wilcoxon signed rank test. Median microvascular flow index of medium blood vessels decreased after starting cardiopulmonary bypass relative to that after anesthetic induction (2.6, interquartile range 1.6-3.0, vs 3.0, interquartile range 2.8-3.0, P = .02). There was a trend toward decreased microvascular flow index of small and large vessels relative to baseline (P = .08 and P = .05, respectively). Decreases in microvascular flow index occurred irrespective of changes in systemic blood pressure. After each patient's return to the intensive care unit, microvascular flow index increased and normalized in all microvessels. For the first time, sublingual microvascular blood flow alterations have been observed during cardiopulmonary bypass-assisted coronary artery bypass grafting.

Monitoring efficacy of red blood cell transfusion in sepsis by sublingual microvascular perfusion: A tongue speaks without words*

Critical Care Medicine: July 2007 - Volume 35 - Issue 7 - p 1773-1774 doi: 10.1097/01.CCM.0000269396.54140.22

Microvascular response to red blood cell transfusion in patients with severe sepsis*

Microvascular alterations may play a role in the development of multiple organ failure in severe sepsis. The effects of red blood cell transfusions on microvascular perfusion are not well defined. We investigated the effects of red blood cell transfusion on sublingual microvascular perfusion in patients with sepsis. Prospective, observational study. A 31-bed, medical-surgical intensive care unit of a university hospital. Thirty-five patients with severe sepsis requiring red blood cell transfusions. Transfusion of one to two units of leukocyte-reduced red blood cells. The sublingual microcirculation was assessed with an Orthogonal Polarization Spectral device before and 1 hr after red blood cell transfusion. Red blood cell transfusions increased hemoglobin concentration from 7.1 (25th-75th percentile, 6.7-7.6) to 8.1 (7.5-8.6) g/dL (p < .01), mean arterial pressure from 75 (69-89) to 82 (75-90) mm Hg (p < .01), and oxygen delivery from 349 (278-392) to 391 (273-473) mL/min.M (p < .001). Microvascular perfusion was not significantly altered by transfusion, but there was considerable interindividual variation. The change in capillary perfusion after transfusion correlated with baseline capillary perfusion (Spearman-rho = -.49; p = .003). Capillary perfusion was significantly lower at baseline in patients who increased their capillary perfusion by >8% compared with those who did not (57 [52-64] vs. 75 [70-79]; p < .01), while hemodynamic and global oxygen transport variables were similar in the two groups. Red blood cell storage time had no influence on the microvascular response to red blood cell transfusion. The sublingual microcirculation is globally unaltered by red blood cell transfusion in septic patients; however, it can improve in patients with altered capillary perfusion at baseline.

Effects of autotransfusion on sublingual microvascular perfusion in hemodialysis patients before and after ultrafiltration

Effects of autotransfusion on sublingual microvascular perfusion in hemodialysis patients before and after ultrafiltration