Functional Capillary Density Research Articles

Influence of Topically Applied Antimicrobial Agents on Muscular Microcirculation

Bacterial infections cause major complications in wound healing. Local antiseptics are used for daily wound care; however, their potential toxic effects on the vasculature have not yet been thoroughly investigated. The aim of this study was to assess the effects of antiseptics on microcirculation. Investigations were performed on a standardized cremaster muscle model on rats (n = 60). The arteriolar diameter and functional capillary density (FCD) were investigated using transillumination microscopy before and 60 and 120 minutes after application of each of the following antimicrobial agents: alcohol, hydrogen peroxide, imipenem, octenidine dihydrochloride, polyhexanide, and ethacridine lactate. Although polyhexanide caused a significant arteriolar dilatation (106.25 ± 3.23 vs. 88.54 ± 6.74 μm [baseline value]) and increase of FCD compared with baseline value (12.65 ± 0.82 vs. 9.10 ± 0.50 n/0.22 mm), alcohol led to a significant decrease of both parameters (90.63 ± 10.80 vs. 52.09 ± 7.69 and 5.35 ± 0.54 vs. 1.68 ± 0.48) and was the only agent that caused arteriolar thrombosis. The FCD also increased significantly after treatment with hydrogen peroxide (10.55 ± 0.33 vs. 12.30 ± 0.48) and octenidine (6.82 ± 0.63 vs. 12.32 ± 0.63). However, no positive effect on arteriolar diameter could be found. Ethacridine lactate and imipenem did not impact either parameter. In addition to reducing bacteria, an antiseptic should be nontoxic, especially to the microcirculation. Polyhexanide seems to have a positive influence on vessel diameter and capillary density, whereas alcohol reduces both parameters. If the antimicrobial efficacy is comparable, the antiseptic with less toxic effects should be chosen, especially in critically perfused wounds.

Valsartan-induced improvement in insulin sensitivity is not paralleled by changes in microvascular function in individuals with impaired glucose metabolism

Individuals with impaired glucose metabolism (IGM) are at high risk of developing type 2 diabetes (T2DM). The renin-angiotensin system (RAS) is activated in insulin-resistant states and its inhibition resulted in delayed onset of T2DM. The underlying mechanisms may include improvement in microvascular structure and function, which may increase glucose and insulin delivery to insulin-sensitive tissues. We hypothesized that functional and structural capillary density is impaired in insulin-resistant individuals with IGM and that treatment with the angiotensin-receptor blocker valsartan (VAL) will improve insulin sensitivity and microvascular function. In this randomized controlled trial, individuals with IGM (n = 48) underwent a hyperinsulinaemic-euglycaemic clamp to assess insulin sensitivity (M-value) and capillaroscopy to examine baseline skin capillary density (BCD), capillary density after arterial occlusion (PRH) and capillary density during venous occlusion (VEN) before and after 26 weeks of VAL or placebo (PLB). Sixteen BMI-matched individuals with normal glucose metabolism (NGM) served as controls. Individuals with IGM were more insulin resistant (P < 0.001) and had impaired microvascular function compared with those with NGM (all P < 0.01). Univariate associations were found for microvascular function (BCD, PRH, VEN) and M-value (all P < 0.005). The relations were independent of age, sex and BMI. VAL improved insulin sensitivity (P = 0.034) and lowered blood pressure as compared with PLB, whereas microvascular function remained unchanged. In insulin-resistant individuals with IGM, impaired functional and structural capillary density was inversely associated with insulin sensitivity. VAL improved insulin sensitivity without affecting the functional and structural capillary density, indicating that other mechanisms may be stronger determinants in the VAL-mediated insulin-sensitizing effect.

Effect of Suspending Viscosity on Red Blood Cell Dynamics and Blood Flows in Microvessels

To obtain a better understanding of the beneficial effect of high plasma viscosity observed in hemodilution and resuscitation experiments, we conducted a computational study to investigate the suspending viscosity effect on red blood cell (RBC) dynamics and blood flow behaviors in microvessels. For single RBCs in simple shear or channel flows, RBCs appear more flexible as indicated by the tank-treading motion in shear flows and the strong transverse migration in channel flows. For the multiple RBC flows in straight channels, our results indicate no significant change with the suspending viscosity in stable flow structure and hemorheologic behaviors, under both constant flow and forcing conditions. However, due to the increase in apparent cell deformability in a more viscous medium, the cell-free layer (CFL) can be established in a shorter distance along the channel. Considering the multilevel bifurcated structure of the microvascular network, this change in CFL development distance may affect the phase skimming and RBC separation processes at the downstream bifurcation, and therefore the microcirculation performance in the tissue. This may suggest a possible mechanism for the high functional capillary density associated with a high suspending viscosity observed in experiments.

Small-Volume Resuscitation From Hemorrhagic Shock Using High-Molecular-Weight Tense-State Polymerized Hemoglobins

The objective of this study was to determine the role of plasma oxygen carrying capacity during resuscitation from hemorrhagic shock (HS). Hemodynamic responses to small-volume resuscitation from HS with hypertonic saline followed by infusion of ultrahigh-molecular-weight tense-state polymerized hemoglobins (PolyHbs) were studied in the hamster window chamber model. HS was induced by withdrawing 50% of the blood volume (BV), and hypovolemic state was maintained for 1 hour. Resuscitation was implemented by infusion of hypertonic saline (3.5% of BV) followed by 10% of BV infusion of polymerized human Hb (PolyHbhum, P50=49 mm Hg), polymerized bovine Hb (PolyHbbov, P50=40 mm Hg), or human serum albumin (HSA), all at 10 g/dL. Resuscitation was monitored over 90 minutes. PolyHbhum elicited higher arterial pressure, produced vasoconstriction, and decreased perfusion. In contrast, PolyHbbov and HSA exhibited lower blood pressure and partially restored perfusion and functional capillary density compared with PolyHbhum. Blood gas parameters showed a pronounced recovery after resuscitation with PolyHbbov compared with both PolyHbhum and HSA. Tissue PO2 was significantly improved in the PolyHbbov group, showing that the moderate increase in P50 of PolyHbbov compared with hamster blood (P50=32 mm Hg) was beneficial during resuscitation. However, an excessive increase in oxygen release between the central and peripheral circulation, as induced by PolyHbhum produced vasoconstriction and hypoperfusion, limiting the benefits of additional oxygen carrying capacity. Appropriately engineered PolyHb will enhance/reinstate oxygenation, without hypertension or vasoconstriction, to be used in situations where blood transfusion is not logistically feasible.

Organic grape juice intake improves functional capillary density and postocclusive reactive hyperemia in triathletes

OBJECTIVE:The aim of this study was to evaluate the effect of organic grape juice intake on biochemical variables and microcirculatory parameters in triathlon athletes.INTRODUCTION:The physiological stress that is imposed by a strenuous sport, such as a triathlon, together with an insufficient amount of antioxidants in the diet may cause oxidative imbalance and endothelial dysfunction.METHODS:Ten adult male triathletes participated in this study. A venous blood sample was drawn before (baseline) and after 20 days of organic grape juice intake (300 ml/day). Serum insulin, plasma glucose and uric acid levels, the total content of polyphenols, and the erythrocyte superoxide dismutase activity were determined. The functional microcirculatory parameters (the functional capillary density, red blood cell velocity at baseline and peak levels, and time required to reach the peak red blood cell velocity during postocclusive reactive hyperemia after a one-min arterial occlusion) were evaluated using nailfold videocapillaroscopy.RESULTS:Compared with baseline levels, the peak levels of serum insulin (p = 0.02), plasma uric acid (p = 0.04), the functional capillary density (p = 0.003), and the red blood cell velocity (p<0.001) increased, whereas the plasma glucose level (p<0.001), erythrocyte superoxide dismutase activity (p = 0.04), and time required to reach red blood cell velocity during postocclusive reactive hyperemia (p = 0.04) decreased after organic grape juice intake.CONCLUSION:Our data showed that organic grape juice intake improved glucose homeostasis, antioxidant capacity, and microvascular function, which may be due to its high concentration of polyphenols. These results indicate that organic grape juice has a positive effect in endurance athletes.

High fat diet induces central obesity, insulin resistance and microvascular dysfunction in hamsters

Microvascular dysfunction is an early finding in obesity possibly related to co-morbidities like diabetes and hypertension. Therefore we have investigated changes on microvascular function, body composition, glucose and insulin tolerance tests (GTT and ITT) on male hamsters fed either with high fat (HFD, n=20) or standard (Control, n=21) diet during 16weeks. Total body fat and protein content were determined by carcass analysis, aorta eNOS and iNOS expression by immunoblotting assay and mean blood pressure (MAP) and heart rate (HR) by an arterial catheter. Microvascular reactivity in response to acetylcholine and sodium nitroprusside, functional capillary density (FCD), capillary recruitment induced by a hyperinsulinemic status and macromolecular permeability after 30min ischemia was assessed on either cheek pouch or cremaster muscle preparations. Compared to Control, HFD animals have shown increased visceral fat (6.0±0.8 vs. 13.8±0.6g/100g BW), impaired endothelial dependent vasodilatation, decreased FCD (11.3±1.3 vs. 6.8±1.2/field) and capillary recruitment during hyperinsulinemia and increased macromolecular permeability after ischemia/reperfusion (86.4±5.2 vs.105.2±5.1leaks/cm2), iNOS expression and insulin resistance. MAP, HR, endothelial independent vasodilatation and eNOS expression were not different between groups. Our results have shown that HFD elicits an increase on visceral fat deposition, microvascular dysfunction and insulin resistance in hamsters.

Improved Resuscitation From Hemorrhagic Shock With Ringer's Lactate With Increased Viscosity in the Hamster Window Chamber Model

Infusion of large volume of fluid is practiced in the treatment of hemorrhagic shock although resuscitation with small fluid volumes reduces the risks associated with fluid overload. We explored the hypothesis that reduced Ringer's lactate (RL) volume restoration in hemorrhage is significantly improved by increasing its viscosity, leading to improved microvascular conditions. Awake hamsters were subjected to a hemorrhage of 50% of blood volume followed by a shock period of 1 hour. They were resuscitated with conventional RL (n = 6) or with RL whose viscosity was increased by the addition of 0.3% alginate (RL-HV) (n = 6). In both cases, the volume infused was 200% of shed blood. After resuscitation, blood and plasma viscosities were 1.9 cp ± 0.18 cp and 1.0 cp ± 0.03 cp in RL and 2.5 cp ± 0.34 cp and 1.6 cp ± 0.05 cp in RL-HV. Mean arterial pressure was lower than baseline in RL. Arteriolar diameter and arteriolar and venular flow were significantly higher in RL-HV. Functional capillary density was significantly higher in RL-HV than RL. After 90 minutes of resuscitation, functional capillary density was lower than baseline in RL, whereas it was maintained in RL-HV. Arteriolar PO₂ was higher in RL-HV than RL. Microcirculation O₂ delivery and tissue PO₂ were significantly higher in RL-HV. Increasing blood and plasma viscosities in resuscitation from hemorrhagic shock with increased viscosity RL improves microvascular hemodynamics and oxygenation parameters.

Evaluation of the effects of gender and estradiol treatment on the intestinal microcirculation during experimental sepsis

Intestinal barrier dysfunction plays an important role in sepsis. Females may tolerate sepsis better than males, which could be due to the relative resistance of the female intestine to gut injury and inflammation when subjected to sepsis.In this study the intestinal microcirculation was investigated in 50 female and 40 male rats divided in to 9 groups of 10 animals. Male and female rats were subjected to sham CASP (colon ascendens stent peritonitis). We induced experimental sepsis (CASP) in another two groups of male and female rats. The role of the estradiol treatment was evaluated both in male and ovariectomized female rats. Female rats were subjected to sham ovariectomy 3weeks before sham CASP. Male and ovariectomized female rats were treated with estradiol (10mg/kg estradiol in rizinus oil immediately and 12h following CASP). Another two groups of male and ovariectomized female rats received placebo oil treatment. To evaluate the effects of gender and estradiol treatment on the microvascular perfusion during sepsis, intravital microscopy was performed twenty-four hours after sham CASP or CASP surgery, which permits the in vivo determination of leukocyte–endothelial cell interaction (rolling leukocytes and adherent leukocytes) and the measurement of functional capillary density (FCD), which served as the measure of quality of microvascular perfusion.We found that there was gender difference mainly in the leukocyte endothelial interaction rather than the functional capillary density (FCD), in which male showed significant increases (P<0.05) both in the leukocyte adhesion and rolling leukocytes in submucosal venules (V1 and V3) in comparison to female rats. (Leukocyte adhesion: V1 107.1±49.2n/mm2; V3 112.3±68.1n/mm2) (Rolling leukocytes:V1 16.2±10.3n/min; V3 8.4±8.2n/min). In addition estradiol replacement in ovariectomized female and male rats induced significant decreases (P<0.05) in the leukocyte adhesion and rolling (V1 and V3) with a significant increase in the muscular FCD in comparison to the corresponding placebo treated groups. (Leukocyte adhesion: V1 60±31n/mm2; V3 78.11±37.6n/mm2) (Rolling leukocytes: V1 13.4±8.9n/min; V3 5.8±7.4n/min) (Longitudinal muscular FCD (cm/cm2): in ovariectomized female rats 107.1±12.2; in male rats 106.2±15.3) (Circular muscular FCD (cm/cm2): in ovariectomized female rats: 84.8±14.2; in male rats: 86.1±15.3).We conclude that gender difference in the leukocyte endothelial interaction could explain the resistance of female intestine to injury, and that estradiol treatment could improve the intestinal microcirculation through its effects on the leukocyte endothelial interaction and the FCD both in male and ovariectomized female rats.

Influence of antiseptics on microcirculation after neuronal and receptor blockade

The topical application of the antiseptics octenidine and polyhexanide on wounds seems to improve microcirculation. These two antiseptics were tested in combination with neuronal inhibition and sympathethic receptor blockade to verify these findings, explore the influence of β blockers on these microcirculative effects, and find out the principle of operation. Investigations were carried out on a standardised cremaster muscle model in rats (n = 66). The tested antiseptics, octenidine and polyhexanide were investigated alone (n = 12) and in combination with bupivacaine (n = 12), metoprolol (n = 12), phentolamine (n = 12) and surgical denervation (n = 12). Physiological saline was used for control (n = 6). The arteriolar diameter and functional capillary density (FCD) were investigated via trans-illumination microscopy before, as well as 60 and 120 minutes after application. Polyhexanide caused a significant increase in arteriolar diameter (86·5 ± 3·8 µm versus 100·0 ± 3·6 µm) and, like octenidine (7·2 ± 0·7 n/0·22 mm(2) versus 11·6 ± 0·6 n/0·22 mm(2) ), in FCD (9·2 ± 0·5 versus 12·6 ± 0·9) as well. When the antiseptics are used in combination with bupivacaine, metoprolol, phentolamine or surgical sympathectomy, these effects were eliminated or inverted. Assessing the results of the different blockades in combination with polyhexanide, we surmise that the antiseptic polyhexanide acts on the microcirculation mainly by blocking α receptors. This study shows that polyhexanide and octenidine improve muscular perfusion. Interestingly, the benefit of polyhexanide and octenidine on muscular perfusion is eliminated when the antiseptics are combined with other vasoactive agents, especially β blockers.

Vasoactive hemoglobin solution improves survival in hemodilution followed by hemorrhagic shock*

To compare survival after exchange transfusion followed by hemorrhage using: 1) the vasoactive, oxygen-carrying, bovine hemoglobin-based blood substitute Oxyglobin (Biopure, 12.9 g hemoglobin/dL); and 2) the hydroxyethyl starch plasma expander Hextend (high molecular weight and low degree of substitution, 6%). Comparison between treatments. Laboratory. Awake hamster chamber window model. Fifty percent blood volume exchange transfusion followed by a 60% hemorrhage over 1 hr, followed by 1 hr of observation. Measurement of blood gases, mean arterial blood pressure, functional capillary density, arteriolar and venular diameter, and Po2 tension distribution. Survival with Oxyglobin was 100% and only 50% for the Hextend group. Vasoconstriction was evident in the microcirculation. Mean arterial pressure was higher in the Oxyglobin group. Functional capillary density was significantly reduced, although to a lesser extent by Oxyglobin. There was no difference in microvascular Po2 distribution after 1 hr of shock between groups. Higher mean arterial pressure during the initial stages of hemorrhage could be due to vasoconstriction in the Oxyglobin group as compared to the Hextend group. It is concluded that the pressor effect due to a vasoactive oxygen carrier may be beneficial in maintaining perfusion in conditions of severe hemodilution followed by hypovolemia.

Brazil nuts intake improves lipid profile, oxidative stress and microvascular function in obese adolescents: a randomized controlled trial.

BackgroundObesity is a chronic disease associated to an inflammatory process resulting in oxidative stress that leads to morpho-functional microvascular damage that could be improved by some dietary interventions. In this study, the intake of Brazil nuts (Bertholletia excelsa), composed of bioactive substances like selenium, α- e γ- tocopherol, folate and polyunsaturated fatty acids, have been investigated on antioxidant capacity, lipid and metabolic profiles and nutritive skin microcirculation in obese adolescents.MethodsObese female adolescents (n = 17), 15.4 ± 2.0 years and BMI of 35.6 ± 3.3 kg/m2, were randomized 1:1 in two groups with the diet supplemented either with Brazil nuts [BNG, n = 08, 15-25 g/day (equivalent to 3 to 5 units/day)] or placebo [PG (lactose), n = 09, one capsule/day] and followed for 16 weeks. Anthropometry, metabolic-lipid profiles, oxidative stress and morphological (capillary diameters) and functional [functional capillary density, red blood cell velocity (RBCV) at baseline and peak (RBCVmax) and time (TRBCVmax) to reach it during post-occlusive reactive hyperemia, after 1 min arterial occlusion] microvascular variables were assessed by nailfold videocapillaroscopy at baseline (T0) and after intervention (T1).ResultsT0 characteristics were similar between groups. At T1, BNG (intra-group variation) had increased selenium levels (p = 0.02), RBCV (p = 0.03) and RBCVmax (p = 0.03) and reduced total (TC) (p = 0.02) and LDL-cholesterol (p = 0.02). Compared to PG, Brazil nuts intake reduced TC (p = 0.003), triglycerides (p = 0.05) and LDL-ox (p = 0.02) and increased RBCV (p = 0.03).ConclusionBrazil nuts intake improved the lipid profile and microvascular function in obese adolescents, possibly due to its high level of unsaturated fatty acids and bioactive substances.Trial RegistrationClinical Trials.gov NCT00937599

In vitro and in vivo evaluation of the anti-angiogenic actions of 4-hydroxybenzyl alcohol.

4-Hydroxybenzyl alcohol (HBA) is a phenolic plant compound, which has been shown to influence many cellular mechanisms. In the present study, we analysed in vitro and in vivo the anti-angiogenic actions of this pleiotropic agent. Migration and protein expression of HBA- and vehicle-treated endothelial-like eEND2 cells was assessed by cell migration assay and Western blot analyses. HBA action on vascular sprouting was analysed in an aortic ring assay. In vivo anti-angiogenic actions of HBA were studied in the dorsal skinfold chamber model of endometriosis in mice. Western blot analyses demonstrated that HBA inhibited proliferation of eEND2 cells, as indicated by down-regulation of proliferating cell nuclear antigen expression, and reduced expression of vascular endothelial growth factor and matrix metalloproteinase 9. HBA suppressed the migration of eEND2 cells, accompanied by inhibition of actin filament reorganization, revealed by fluorescence staining of the cytoskeleton. In addition, HBA reduced vascular sprouting in the aortic ring assay. Finally, we found, in the dorsal skinfold chamber model in vivo using intravital fluorescence microscopy, that HBA inhibited the vascularization of developing endometriotic lesions, as indicated by a decreased functional capillary density of lesions in HBA-treated mice and a reduced lesion size, compared with control animals. HBA targets several angiogenic mechanisms and therefore represents a promising anti-angiogenic agent for the treatment of angiogenic diseases, such as endometriosis.

Microvascular response to metabolic and pressure challenge in the human coronary circulation

In vivo observations of microcirculatory behavior during autoregulation and adaptation to varying myocardial oxygen demand are scarce in the human coronary system. This study assessed microvascular reactions to controlled metabolic and pressure provocation [bicycle exercise and external counterpulsation (ECP)]. In 20 healthy subjects, quantitative myocardial contrast echocardiography and arterial applanation tonometry were performed during increasing ECP levels, as well as before and during bicycle exercise. Myocardial blood flow (MBF; ml·min(-1)·g(-1)), the relative blood volume (rBV; ml/ml), the coronary vascular resistance index (CVRI; dyn·s·cm(-5)/g), the pressure-work index (PWI), and the pressure-rate product (mmHg/min) were assessed. MBF remained unchanged during ECP (1.08 ± 0.44 at baseline to 0.92 ± 0.38 at high-level ECP). Bicycle exercise led to an increase in MBF from 1.03 ± 0.39 to 3.42 ± 1.11 (P < 0.001). The rBV remained unchanged during ECP, whereas it increased under exercise from 0.13 ± 0.033 to 0.22 ± 0.07 (P < 0.001). The CVRI showed a marked increase under ECP from 7.40 ± 3.38 to 11.05 ± 5.43 and significantly dropped under exercise from 7.40 ± 2.78 to 2.21 ± 0.87 (both P < 0.001). There was a significant correlation between PWI and MBF in the pooled exercise data (slope: +0.162). During ECP, the relationship remained similar (slope: +0.153). Whereas physical exercise decreases coronary vascular resistance and induces considerable functional capillary recruitment, diastolic pressure transients up to 140 mmHg trigger arteriolar vasoconstriction, keeping MBF and functional capillary density constant. Demand-supply matching was maintained over the entire ECP pressure range.

Sublingual Microvascular Changes in Patients With Cerebral Small Vessel Disease

It is unknown whether changes in cerebral small vessel disease (SVD) are limited to the brain or part of a generalized vascular disorder. We examined the sublingual microcirculation of 10 healthy controls, 10 patients with large vessel disease, and 8 with SVD, with side-stream dark field imaging. We analyzed 146 video fragments masked to the origin of the videos. Imaging software measured the functional capillary density per tissue surface unit. We scored the percentage of blood vessels with abnormal flow (abnormal flow index) and the presence of extravascular erythrocyte material as presumed evidence of past microbleeds or obliterated vessels. Functional capillary density differed between the 3 groups (SVD, large vessel disease, and controls; means, 14.8, 17.0, and 16.1 mm/mm2; P=0.01). Abnormal flow was more frequent in SVD patients compared with large vessel disease patients and controls (medians, 10.5%, 6.1%, 5.5%; P=0.04). Extravascular erythrocyte material was almost exclusively present in patients with SVD (P=0.004). We found evidence of pathological changes in the sublingual microcirculation in patients with cerebral small vessel disease, which suggests that cerebral SVD is part of a generalized vascular disorder.

N-acetylcysteine attenuates leukocytic inflammation and microvascular perfusion failure in critically ischemic random pattern flaps

Introduction Microcirculatory dysfunction causes ischemia resulting in tissue necrosis. N-acetylcysteine (NAC) has been shown capable of protecting tissue from ischemic necrosis. However, the mechanism of action of NAC is yet not fully understood. Objective Herein, we studied whether NAC is capable of attenuating microvascular perfusion failure in critically ischemic musculo-cutaneous tissue. Material and methods A laterally based skin flap was elevated in the dorsum of C57BL/6 mice and fixed into a dorsal skinfold chamber. Arteriolar perfusion, functional capillary density, leukocytic inflammation, apoptotic cell death, and non-perfused tissue area were repetitively analyzed over 10 days by intravital fluorescence microscopy. Treatment with either 100 mg/kg NAC or saline (control) was started 30 min before surgery and was continued until day 10 after flap elevation. Results Surgery induced leukocytic inflammation, microvascular perfusion failure, apoptosis, and tissue perfusion failure. NAC was capable of significantly attenuating the area of non-perfused tissue. This was associated by a marked arteriolar dilation and an increased capillary perfusion. NAC further reduced the ischemia-associated leukocytic response and significantly attenuated apoptotic cell death in all areas of the flap. Conclusion NAC is effective to attenuate leukocytic inflammation and microvascular perfusion failure in critically ischemic tissue. Thus, NAC treatment may represent a promising approach to improve the outcome of ischemically endangered flap tissue.

Delaying Blood Transfusion in Experimental Acute Anemia with a Perfluorocarbon Emulsion

To avoid unnecessary blood transfusions, physiologic transfusion triggers, rather than exclusively hemoglobin-based transfusion triggers, have been suggested. The objective of this study was to determine systemic and microvascular effects of using a perfluorocarbon-based oxygen carrier (PFCOC) to maintain perfusion and oxygenation during extreme anemia. The hamster (weight, 55-65 g) window chamber model was used. Two isovolemic hemodilution steps were performed using hydroxyethyl starch, 10%, at normoxic conditions to a hematocrit of 19% (hemoglobin, 5.5 g/dl), the point at which the transfusion trigger was reached. Two additional hemodilution exchanges using the PFCOC (Oxycyte) and increasing the fraction of inspired oxygen to 1.0 were performed to reduce the hematocrit to 11% (hemoglobin, 3.8 g/dl) and 6% (hemoglobin, 2.0 g/dl), respectively. No control group was used in the study because this concentration of hemodilution is lethal with conventional plasma expanders. Systemic parameters, microvascular perfusion, functional capillary density, and oxygen tensions across the microvascular network were measured. At 6% hematocrit, the PFCOC maintained mean arterial pressure, cardiac output, systemic oxygen delivery, and oxygen consumption. As hematocrit was decreased from 11% to 6%, functional capillary density, calculated microvascular oxygen delivery, and oxygen consumption decreased; and the oxygen extraction ratio was close to 100%. Peripheral tissue oxygenation was not predicted by systemic oxygenation. The PFCOC, in conjunction with hyperoxia, was able to sustain organ function and partially provide systemic oxygenation during extreme anemia during the observation period. The PFCOC can work as a bridge until erythrocytes are available for transfusion or when additional oxygen is required, despite the possible limitations in peripheral tissue oxygenation.

TISSUE OXIDATIVE METABOLISM AFTER EXTREME HEMODILUTION WITH PEG CONJUGATED HEMOGLOBIN

NADH fluorometry was used as a non‐invasive technique to monitor changes in the energy state of intact tissue in the hamster window chamber model. Acute moderate isovolemic hemodilution was induced by two isovolemic hemodilution steps using 6% dextran 70kDa to 18% hematocrit (Hct). The protocol continued with an exchange transfusion to reduce erythrocytes to 75% of baseline (11% Hct) using either polyethylene glycol (PEG) maleimide conjugated hemoglobin 4 g/dl (PEG‐Hb) or a dextran (Dex70, 6 g/dl dextran 70 kDa). Systemic parameters, microvascular perfusion, functional capillary density, intravascular and interstitial oxygen tensions and intracellular NADH fluorescence were monitored. Blood pressure after extreme hemodilution was statistically significantly reduced for Dex70 when compared to PEG‐Hb. While microvascular blood flows were not different, the functional capillary density was significantly higher for PEG‐Hb compared to Dex70. Intravascular PO2 for PEG‐Hb was higher in arterioles compared to Dex70, but not different for either tissue or venular PO2. Cellular energy metabolism in the tissues was improved with PEG‐Hb. Hhemodilution to 18% Hct brings tissue oxygen delivery to the verge of inadequacy. Extreme hemodilution to 11% Hct produces tissue and anoxia, and high oxygen affinity PEG‐Hb (P50: 4 mmHg) and partially decreases anaerobic metabolism.

Nitric oxide prevents cardiovascular collapse during shock

This study investigated the systemic and microvascular hemodynamic changes after severe hemorrhage. Nitric oxide (NO) availability was increased by administration of NO releasing nanoparticles (NO‐nps). Hemodynamic responses to hemorrhagic shock were studied in the hamster window chamber. Acute hemorrhage was induced by arterial controlled bleeding of 50% of blood volume, and the resulting hemodynamic parameters were followed over 90 min. Exogenous NO was administered in the form of NO‐nps (5 mg/kg suspended in 50 μl saline) 10 min following induced hemorrhage. Control groups received equal dose of NO free nanoparticles (Control‐nps) and Vehicle solution (50 μl saline). Animals treated with NO‐nps partially maintained systemic and microvascular function during hypovolemic shock compared to animals treated with Control‐nps or the Vehicle. The continuous NO released by the NO‐nps reverted arteriolar vasoconstriction, partially recovered both functional capillary density and microvascular blood flows. Additionally, NO supplementation prevented cardiac decompensation. Paradoxically, peripheral vasodilation induced by the NO‐nps did not decrease blood pressure or vascular resistance. NO‐nps promoted intravascular pressure redistribution, increased blood flow and prevented ischemia. Therefore, NO released from NO‐nps can ultimately increase survivability and reduce shock sequelae.

Capillary rarefaction in advanced chronic kidney disease is associated with high phosphorus and bicarbonate levels

In patients with chronic kidney disease (CKD), disorders of mineral metabolism are associated with vascular calcifications and mortality. Microvascular dysfunction, by affecting flow resistance and tissue perfusion, may explain the cardiovascular sequelae of CKD-associated disorders of mineral metabolism. We investigated whether advanced CKD is associated with a decrease in the functional and structural number of capillaries in skin and subsequently whether capillary rarefaction is related to mineral metabolism. Capillary density was measured by nailfold microscopy in 19 predialysis and 35 CKD Stage 5 (CKD5) patients and 19 controls. In CKD patients, calcium, phosphorus, parathyroid hormone, 25-hydroxyvitaminD3 (25vitD3) and 1,25-dihydroxyvitaminD3 (1,25vitD3) were analysed as well. Capillary density at baseline was 42 ± 15/mm(2) in predialysis patients, 45 ± 17/mm(2) in CKD5 patients and 56 ± 20/mm(2) in controls (patients versus controls, respectively, P < 0.05 and P = 0.05). Absolute capillary recruitment during post-occlusive reactive hyperaemia was 17 ± 7/mm(2), 14 ± 6/mm(2) and 23 ± 8/mm(2), respectively (P < 0.05 for both patients and controls). Capillary density during venous occlusion was 59 ± 20/mm(2), 59 ± 21/mm(2) and 77 ± 21/mm(2), respectively (P < 0.05 for both patients and controls). In multiple regression analysis, both serum phosphorus and bicarbonate values were independently and inversely associated with capillary density at baseline (r(2) of model = 19%) as well as during venous occlusion (r(2) of model = 28%). Furthermore, both serum phosphorus and bicarbonate were inversely and female gender positively correlated with capillary density during recruitment (r(2) of model = 37%). Advanced CKD is characterized by an impaired functional and structural capillary density in skin, which is related to both high phosphorus and bicarbonate values.

Sublingual and muscular microcirculatory alterations after cardiac arrest: A pilot study

Aims of the study Post-cardiac arrest resuscitated patients often develop a “sepsis-like” syndrome, which may be associated with organ dysfunction. Impaired microcirculatory blood flow is thought to play a key role in sepsis-induced organ failure; however, few data are available on the microcirculation after cardiac arrest. We investigated microvascular density and reactivity in the early phase following cardiac arrest. Methods We prospectively evaluated the sublingual microcirculation in 10 patients admitted to the intensive care unit (ICU) after cardiac arrest using a Sidestream Dark Field device. Thenar oxygen saturation (StO 2) was also measured using a tissue spectrometer and a vaso-occlusive test was performed by rapid inflation of a pneumatic cuff around the arm to evaluate the StO 2 reperfusion rate, reflecting microvascular reactivity. In all patients, measurements were performed within the first 12 h after admission (T1) and 24–48 h thereafter (T2). Results There was a significant increase in functional capillary density (FCD, 7.2 ± 1.9–10.0 ± 1.4 N/mm, p = 0.001), in the proportion of small perfused vessels (PSPV, 76 ± 13–92 ± 3%, p = 0.004) and in the mean microvascular flow index (MFI, 2.1 ± 0.5–2.8 ± 0.2, p = 0.003) at T2 compared to T1. FCD and PSPV were significantly correlated to body temperature, but not to cardiac output or mean arterial pressure. The StO 2 reperfusion rate did not change over the study period and showed considerable inter-individual variability. Conclusions The early post-resuscitation phase is characterised by significant abnormalities in microvascular density and flow, which return to normal within 48 h after cardiac arrest. These changes may be influenced by body temperature. Microvascular reactivity is impaired after cardiac arrest.