The heterogeneity of the microcirculation in critical illness

Restoring microcirculatory perfusion in a preclinical model of severe hemorrhagic shock: The role of microcirculatory function

BACKGROUND

No reflow in capillaries (no reflow) is the lack of tissue perfusion that occurs once central hemodynamics are restored. This prevents oxygen transfer and debt repayment to vital tissues after shock resuscitation. Since metabolic swelling of cells and tissues can cause no reflow, it is a target for study in shock. We hypothesize no reflow secondary to metabolic cell swelling causes the problem not addressed by current strategies that increase central hemodynamics alone.

METHODS

Anesthetized swine were bled until plasma lactate reached 7.5 mM to 9 mM. Intravenous low volume resuscitation solutions were administered (6.8 mL/kg over 5 minutes) consisting of; (1) lactated Ringer (LR), (2) autologous whole blood, (3) high-dose vitamin C (200 mg/kg), or (4) 10% PEG-20k, a polymer-based cell impermeant that corrects metabolic cell swelling. Outcomes were macrohemodynamics (MAP), plasma lactate, capillary flow in the gut and tongue mucosa using orthogonal polarization spectral imaging (OPSI), and survival to 4 hours.

RESULTS

All PEG-20k resuscitated swine survived 240 minutes with MAP above 60 mm Hg compared with 50% and 0% of the whole blood and LR groups, respectively. The vitamin C group died at just over 2 hours with MAPs below 40 and high lactate. The LR swine only survived 30 minutes and died with low MAP and high lactate. Capillary flow positively correlated ( p < 0.05) with survival and MAP. Sublingual OPSI correlated with intestinal OPSI and OPSI was validated with a histological technique.

DISCUSSION

Targeting micro-hemodynamics in resuscitation may be more important than macrohemodynamics. Fixing both is optimal. Sublingual OPSI is clinically achievable to assess micro-hemodynamic status. Targeting tissue cell swelling that occurs during ATP depletion in shock using optimized osmotically active cell impermeants in crystalloid low volume resuscitation solutions improves perfusion in shocked tissues, which leverages a primary mechanism of injury.

Manipulation of Nitric Oxide Levels via a Modified Hydroxyethyl Starch Molecule

INTRODUCTION

Although the improving effect of nitric oxide (NO) donors has experimentally been demonstrated in shock, there are still no NO donor medications clinically available. Thiol-nitrosothiol-hydroxyethyl starch (S-NO-HES) is a novel molecule consisting of NO coupled to a thiolated derivative of hydroxyethyl starch (HES). It was aimed to assess the ability of S-NO-HES to serve as an NO donor under a variety of in vitro simulated physiologic conditions, which might be the first step to qualify this molecule as a novel type of NO donor-fluid.

METHODS

We studied the effect of temperature on NO-releasing properties of S-NO-HES in blood, at 34°C, 37°C, and 41°C. Ascorbic acid (Asc) and amylase were also tested in a medium environment. In addition, we evaluated the activity of S-NO-HES in the isolated aortic ring and Langendorff-perfused heart setup.

RESULTS

The NO release property of S-NO-HES was found at any temperature. Asc led to a significant increase in the production of NO compared to S-NO-HES incubation (P < 0.05). The addition of amylase together with Asc to the medium further increased the release of NO (P < 0.05). S-NO-HES exerted significant vasodilatory effects on phenylephrine precontracted aortic rings that were dose-dependent (P < 0.01). Furthermore, S-NO-HES significantly increased the heart rate and additionally reduced the duration of the cardiac action potential, as indicated by a reduction of QTc-B values (P < 0.01).

CONCLUSIONS

We demonstrated for the first time that the S-NO-HES molecule exhibited its NO-releasing effects. The effectiveness of this new NO donor to substitute NO deficiency under septic conditions or in other indications needs to be studied.

[Evaluation of the duration of fixation of adhesive products in the treatment of traumatic lesions of the oral mucosa]

OBJECTIVE

The purpose of this study was to evaluate the duration of fixation of adhesive films in the treatment of traumatic lesions of the oral mucosa.

MATERIAL AND METHODS

The patients were divided into 2 groups. In the first group, the affected area was covered with an adhesive film with solcoseryl, in the second group with a film with vitamin E. The film was glued to the affected area according to the instructions, the time of gluing was recorded, patients were warned about the need to notify researchers via messengers or SMS messages about the time of peeling or resorption of the film. The evaluation was carried out by the method of variation statistics (Student's t-test for independent samples).

RESULTS

The retention time of the film in the oral cavity was expressed in minutes, the average value in group 1 was 48.4±9.19, in group 2 - 127.70±49.07. Thus, the fixation of the film with vitamin E was longer than the films with solcoseryl (p=0.000180).

CONCLUSION

Both films provided sufficient protective effect during the retention period. However, in clinical situations where a longer barrier protective effect to the damaged oral mucosa surface is required, it is advisable to use a vitamin E healing patch.

Topical nitroglycerin to detect reversible microcirculatory dysfunction in patients with circulatory shock after cardiovascular surgery: an observational study

Persistent abnormalities in microcirculatory function are associated with poor clinical outcomes in patients with circulatory shock. We sought to identify patients with acutely reversible microcirculatory dysfunction using a low-dose topical nitroglycerin solution and handheld videomicroscopy during circulatory shock after cardiac surgery. Forty subjects were enrolled for the study, including 20 preoperative control and 20 post-operative patients with shock. To test whether microcirculatory dysfunction is acutely reversible during shock, the sublingual microcirculation was imaged with incident dark field microscopy before and after the application of 0.1 mL of a 1% nitroglycerin solution (1 mg/mL). Compared to the control group, patients with shock had a higher microcirculation heterogeneity index (MHI 0.33 vs. 0.12, p < 0.001) and a lower microvascular flow index (MFI 2.57 vs. 2.91, p < 0.001), total vessel density (TVD 22.47 vs. 25.90 mm/mm2, p = 0.005), proportion of perfused vessels (PPV 90.76 vs. 95.89%, p < 0.001) and perfused vessel density (PVD 20.44 vs. 24.81 mm/mm2, p < 0.001). After the nitroglycerin challenge, patients with shock had an increase in MFI (2.57 vs. 2.97, p < 0.001), TVD (22.47 vs. 27.51 mm/mm2, p < 0.009), PPV (90.76 vs. 95.91%, p < 0.001), PVD (20.44 vs. 26.41 mm/mm2, p < 0.001), venular RBC velocity (402.2 vs. 693.9 µm/s, p < 0.0004), and a decrease in MHI (0.33 vs. 0.04, p < 0.001. Thirteen of 20 patients showed a pharmacodynamic response, defined as an increase in PVD > 1.8 SD from shock baseline. Hemodynamics and vasoactive doses did not change during the 30-min study period. Our findings suggest a topical nitroglycerin challenge with handheld videomicroscopy can safely assess for localized recruitment of the microcirculatory blood flow in patients with circulatory shock and may be a useful test to identify nitroglycerin responsiveness.

Protocol for the MicroRESUS study: The impact of circulatory shock and resuscitation on microcirculatory function and mitochondrial respiration after cardiovascular surgery

Background

Despite current resuscitation strategies, circulatory shock and organ injury after cardiac surgery occur in 25–40% of patients. Goal-directed resuscitation after cardiac surgery has generated significant interest, but clinical practice to normalize hemodynamic variables including mean arterial pressure, cardiac filling pressures, and cardiac output may not reverse microcirculation abnormalities and do not address cellular dysoxia. Recent advances in technology have made it possible to measure critical components of oxygen delivery and oxygen utilization systems in live human tissues and blood cells. The MicroRESUS study will be the first study to measure microcirculatory and mitochondrial function in patients with circulatory shock and link these findings with clinical outcomes.

Methods and analysis

This will be a prospective, observational study that includes patients undergoing elective cardiovascular surgery with cardiopulmonary bypass (CPB). Microcirculation will be quantified with sublingual incident dark field videomicroscopy. Mitochondrial respiration will be measured by performing a substrate–uncoupler–inhibitor titration protocol with high resolution respirometry on peripheral blood mononuclear cells at baseline and serial timepoints during resuscitation and at recovery as a possible liquid biomarker. Plasma samples will be preserved for future analysis to examine endothelial injury and other mechanisms of microcirculatory dysfunction. Thirty-day ventilator and vasopressor-free days (VVFDs) will be measured as a primary outcome, along with sequential organ failure assessment scores, and other clinical parameters to determine if changes in microcirculation and mitochondrial respiration are more strongly associated with clinical outcomes compared to traditional resuscitation targets.

Discussion

This will be the first prospective study to examine both microcirculatory and mitochondrial function in human patients with circulatory shock undergoing cardiac bypass and address a key mechanistic knowledge gap in the cardiovascular literature. The results of this study will direct future research efforts and therapeutic development for patients with shock.

Sub-therapeutic vasopressin but not therapeutic vasopressin improves gastrointestinal microcirculation in septic rats: A randomized, placebo-controlled, blinded trial

INTRODUCTION

Sepsis impairs gastrointestinal microcirculation and it is hypothesized that this might increase patient's mortality. Sub-therapeutic vasopressin improves gastric microcirculation under physiologic conditions whereas a therapeutic dosing regimen seems to be rather detrimental. However, the effects of sub-therapeutic vasopressin on gastrointestinal microcirculation in sepsis are largely unknown. Therefore, we conducted this trial to investigate the effect of sub-therapeutic as well as therapeutic vasopressin on gastrointestinal microcirculation in sepsis.

METHODS

40 male Wistar rats were randomized into 4 groups. Colon ascendens stent peritonitis (CASP)-surgery was performed to establish mild or moderate sepsis. 24 hours after surgery, animals received either vasopressin with increasing dosages every 30 min (6.75, 13.5 (sub-therapeutic), 27 mU · kg-1 · h-1 (therapeutic)) or vehicle. Microcirculatory oxygenation (μHBO2) of the colon was recorded for 90 min using tissue reflectance spectrophotometry. Intestinal microcirculatory perfusion (total vessel density (TVD; mm/mm2) and perfused vessel density (PVD; mm/mm2)) were measured using incident dark field-Imaging at baseline and after 60 min.

RESULTS

In mild as well as in moderate septic animals with vehicle-infusion intestinal μHbO2, TVD and PVD remained constant. In contrast, in moderate sepsis, sub-therapeutic vasopressin with 13.5 mU · kg-1 · h-1 elevated intestinal μHBO2 (+ 6.1 ± 5.3%; p < 0.05 vs. baseline) and TVD (+ 5.2 ± 3.0 mm/mm2; p < 0.05 vs. baseline). μHBO2, TVD and PVD were significantly increased compared to moderate sepsis alone. However, therapeutic vasopressin did not change intestinal microcirculation. In mild septic animals sub-therapeutic as well as therapeutic vasopressin had no relevant effect on gastrointestinal microcirculation. Systemic blood pressure remained constant in all groups.

CONCLUSION

Sub-therapeutic vasopressin improves gastrointestinal microcirculatory oxygenation in moderate sepsis without altering systemic blood pressure. This protective effect seems to be mediated by an enhanced microcirculatory perfusion and thereby increased oxygen supply. In contrast, therapeutic vasopressin did not show this beneficial effect.

Catecholaminergic Vasopressors Reduce Toll-Like Receptor Agonist-Induced Microvascular Endothelial Cell Permeability But Not Cytokine Production

Supplemental Digital Content is available in the text.

OBJECTIVES:

Catecholaminergic vasopressors are the cornerstone of circulatory shock management. Nevertheless, catecholamines have problematic side effects, arousing a growing interest in noncatecholaminergic agents such as vasopressin or angiotensin-II. However, their respective effects on sepsis-associated microvascular endothelial dysfunction such as permeability or inflammation remain elusive. We investigated the role of catecholamines and other vasopressors on Toll-like receptor agonists-induced microvascular endothelial permeability and inflammation.

SETTING:

University research laboratory/cell research.

SUBJECTS:

Human pulmonary microvascular endothelial cells from multiple donors.

INTERVENTION:

Confluent monolayers of human pulmonary microvascular endothelial cells were treated with Toll-like receptor agonists (lipopolysaccharide, Poly[I:C], or tripalmitoyl-S-glyceryl cysteine) in the presence or absence of epinephrine, norepinephrine, vasopressin, and angiotensin-II. Permeability was inferred from transendothelial resistance, measured using electrical cell impedance sensing, where decreased transendothelial resistance is consistent with increased permeability. Cell-cell junction molecule expression was assessed via immunofluorescence microscopy and flow cytometry. We quantified cytokines in supernatants of Toll-like receptor agonist-treated human pulmonary microvascular endothelial cells.

MEASUREMENTS AND MAIN RESULTS:

Epinephrine and norepinephrine both ameliorate lipopolysaccharide, polyinosinic:polycytidylic acid, or tripalmitoyl-S-glyceryl cysteine–induced reductions in transendothelial resistance, a surrogate for endothelial permeability. In contrast, the noncatecholaminergic agents, vasopressin, and angiotensin-II did not affect Toll-like receptor agonists-induced reductions in transendothelial resistance. β1- and β2-adrenergic receptor antagonists reduced the effects of the catecholamines on transendothelial resistance, whereas α-adrenergic receptor antagonists did not. We observed that epinephrine and norepinephrine induced actin cytoskeletal rearrangement and normalized the membrane expression of proteins involved with adherens-junctions (vascular endothelial-cadherin) and tight-junctions (zona occludens-1). Despite having a substantial effect on endothelial permeability, epinephrine and norepinephrine did not affect human pulmonary microvascular endothelial cell survival or production of interleukin-8, interleukin-6, or monocyte chemoattractant protein-1 (CCL-2) induced by Toll-like receptor agonists, suggesting that these functions are regulated separately from permeability.

CONCLUSIONS:

Our findings demonstrate that treatment with epinephrine or norepinephrine strongly reduces endothelial permeability induced by agonists of multiple Toll-like receptors (Toll-like receptor-2, Toll-like receptor-3, Toll-like receptor-4) in vitro. Our studies suggest that both β1- and β2-adrenergic receptors mediate the stabilizing effects of epinephrine and norepinephrine on the endothelial barrier.

Low Microcirculatory Perfused Vessel Density and High Heterogeneity are Associated With Increased Intensity and Duration of Lactic Acidosis After Cardiac Surgery with Cardiopulmonary Bypass

INTRODUCTION

Lactic acidosis after cardiac surgery with cardiopulmonary bypass is common and associated with an increase in postoperative morbidity and mortality. A number of potential causes for an elevated lactate after cardiopulmonary bypass include cellular hypoxia, impaired tissue perfusion, ischemic-reperfusion injury, aerobic glycolysis, catecholamine infusions, and systemic inflammatory response after exposure to the artificial cardiopulmonary bypass circuit. Our goal was to examine the relationship between early abnormalities in microcirculatory convective blood flow and diffusive capacity and lactate kinetics during early resuscitation in the intensive care unit. We hypothesized that patients with impaired microcirculation after cardiac surgery would have a more severe postoperative hyperlactatemia, represented by the lactate time-integral of an arterial blood lactate concentration greater than 2.0 mmol/L.

METHODS

We measured sublingual microcirculation using incident darkfield video microscopy in 50 subjects on intensive care unit admission after cardiac surgery. Serial measurements of systemic hemodynamics, blood gas, lactate, and catecholamine infusions were recorded each hour for the first 6 h after surgery. Lactate area under the curve (AUC) was calculated over the first 6 h. The lactate AUC was compared between subjects with normal and low perfused vessel density (PVD < 18 mm/mm2), high microcirculatory heterogeneity index (MHI > 0.4), and low vessel-by-vessel microvascular flow index (MFIv < 2.6).

RESULTS

Thirteen (26%) patients had a low postoperative PVD, 20 patients (40%) had a high MHI, and 26 (52%) patients had a low MFIv. Patients with low perfused vessel density had higher lactate AUC compared with subjects with a normal PVD (22.3 [9.4-31.0] vs. 2.6 [0-8.8]; P < 0.0001). Patients with high microcirculatory heterogeneity had a higher lactate AUC compared with those with a normal MHI (2.5 [0.1-8.2] vs. 13.1 [3.7-31.1]; P < 0.001). We did not find a difference in lactate AUC when comparing high and low MFIv.

CONCLUSION

Low perfused vessel density and high microcirculatory heterogeneity are associated with an increased intensity and duration of lactic acidosis after cardiac surgery with cardiopulmonary bypass.

Levosimendan Ameliorates Post-Resuscitation Acute Intestinal Microcirculation Dysfunction Partly Independent of Its Effects on Systemic Circulation: A Pilot Study On Cardiac Arrest In A Rat Model

BACKGROUND

Cardiac arrest (CA) is recognized as a life-threatening disease; however, the initial resuscitation success rate has increased due to advances in clinical treatment. Levosimendan has shown potential benefits in CA patients. However, its exact function on intestinal and systemic circulation in CA or post-cardiac arrest syndrome (PCAS) remained unclear. This study preliminarily investigated the link between dynamic changes in intestine and systemic hemodynamics post-resuscitation after levosimendan administration.

METHODS

Twenty-five rats were randomized into three groups: 1) sham control group (n = 5), 2) levosimendan group (n = 10), and 3) vehicle group (n = 10). Intestinal microcirculation was observed using a sidestream dark-field imaging device at baseline and each hour of the return of spontaneous circulation (≤6 h). Systemic hemodynamics, serum indicators of cardiac injury, and tissue perfusion/metabolism were measured by echo-cardiography, a biological signal acquisition system, and an enzyme-linked immunosorbent assay (ELISA), respectively.

RESULTS

Myocardial injury and global and intestinal perfusion/metabolism were significantly improved by levosimendan treatment. There was no statistically significant difference in the mean arterial pressure values between the vehicle and levosimendan groups (P > 0.05). The intestinal and systemic circulation measurements showed poor correlation (Pearson r-value of variable combinations in the levosimendan group was much less than 0.75; P < 0.01, levosimendan vs. vehicle group).

CONCLUSIONS

Levosimendan significantly reduced the cardiac injury and corrected the metabolic status in an experimental rat model of ventricular fibrillation (VF) induced CA and CPR. Levosimendan may ameliorate PCAS-induced intestinal microcirculation dysfunction, partly independent of its effects on macrocirculation.

Effect of Pravastatin Pretreatment and Hypercapnia on Intestinal Microvascular Oxygenation and Blood Flow During Sepsis

INTRODUCTION

In septic patients, adequate microvascular oxygenation (μHBO2) of the intestine is vital for their outcome. Recent studies suggest that statins can ameliorate septic microcirculation in a variety of tissues. However, the effect on intestinal microvascular oxygenation and blood flow is largely unknown. Furthermore, there are indications that statin therapy might not be beneficial in the presence of hypercapnia, as observed in septic acute respiratory distress syndrome (ARDS) patients. Therefore, the present study explores the effect of pravastatin with and without additional moderate acute hypercapnia on intestinal microvascular oxygenation and blood flow in experimental sepsis.

METHODS

Forty male Wistar rats were randomized into four groups. Half of the animals received 0.2 mg • kg pravastatin s.c., the other half received the same volume as vehicle (NaCl 0.9%). After 18 h, colon ascendens stent peritonitis surgery was conducted in all animals to induce sepsis. Twenty-four hours after surgery, baseline was established and the animals were subjected to either 120 min of normocapnic (pCO2 40 ± 6 mm Hg) or moderate hypercapnic (pCO2 72 ± 10 mm Hg) ventilation. Microcirculatory oxygenation (μHBO2) and perfusion (μflow) of the colon were continuously recorded using tissue reflectance spectrophotometry and laser Doppler, respectively.

RESULTS

In normocapnic septic animals μHBO2 decreased over time (-8.4 ± 8.7%; P < 0.05 vs. baseline), whereas after pravastatin pretreatment μHBO2 remained constant (-1.9 ± 5.7% vs. baseline). However, in hypercapnic septic animals pretreated with pravastatin μHBO2 declined significantly over time (-8.9 ± 11.8%; P < 0.05 vs. baseline) and was significantly lower compared with normocapnic pravastatin-pretreated animals. μflow did not change over time in any group.

CONCLUSION

Pravastatin pretreatment ameliorates the intestinal microvascular oxygenation in sepsis and thus seems to prevent intestinal hypoxia. Furthermore, we demonstrated that additional hypercapnia abolishes this effect, indicating why septic ARDS patients might not benefit from pravastatin therapy.

Endothelial Responses in Sepsis

Endothelial cells (ECs) are vascular, nonconventional immune cells that play a major role in the systemic response after bacterial infection to limit its dissemination. Triggered by exposure to pathogens, microbial toxins, or endogenous danger signals, EC responses are polymorphous, heterogeneous, and multifaceted. During sepsis, ECs shift toward a proapoptotic, proinflammatory, proadhesive, and procoagulant phenotype. In addition, glycocalyx damage and vascular tone dysfunction impair microcirculatory blood flow, leading to organ injury and, potentially, life-threatening organ failure. This review aims to cover the current understanding of the EC adaptive or maladaptive response to acute inflammation or bacterial infection based on compelling recent basic research and therapeutic clinical trials targeting microvascular and endothelial alterations during septic shock.

Monitoring peripheral perfusion in sepsis associated acute kidney injury: Analysis of mortality

Microcirculatory disorders have been consistently linked to the pathophysiology of sepsis. One of the major organs affected is the kidneys, resulting in sepsis-associated acute kidney injury (SA-AKI) that correlates considerably with mortality. However, the potential role of clinical assessment of peripheral perfusion as a possible tool for SA-AKI management has not been established. To address this gap, the purpose of this study was to investigate the prevalence of peripheral hypoperfusion in SA-AKI, its association with mortality, and fluid balance. This observational cohort study enrolled consecutive septic patients in the Intensive Care Unit. After fluid resuscitation, peripheral perfusion was evaluated using the capillary filling time (CRT) and peripheral perfusion index (PI) techniques. The AKI was defined based on both serum creatinine and urine output criteria. One hundred and forty-one patients were included, 28 (19%) in the non-SA-AKI group, and 113 (81%) in the SA-AKI group. The study revealed higher peripheral hypoperfusion rates in the SA-AKI group using the CRT (OR 3.6; 95% CI 1.35-9.55; p < 0.05). However, this result lost significance after multivariate adjustment. Perfusion abnormalities in the SA-AKI group diagnosed by both CRT (RR 1.96; 95% CI 1.25-3.08) and PI (RR 1.98; 95% CI 1.37-2.86) methods were associated to higher rates of 28-day mortality (p < 0.01). The PI's temporal analysis showed a high predictive value for death over the first 72 h (p < 0.01). A weak correlation between PI values and the fluid balance was found over the first 24 h (r = - 0.20; p < 0.05). In conclusion, peripheral perfusion was not different intrinsically between patients with or without SA-AKI. The presence of peripheral hypoperfusion in the SA-AKI group has appeared to be a prognostic marker for mortality. This evaluation maintained its predictive value over the first 72 hours. The fluid balance possibly negatively influences peripheral perfusion in the SA-AKI.

Alterations of cerebral microcirculation in peritumoral edema: feasibility of in vivo sidestream dark-field imaging in intracranial meningiomas

Background

Intracranial meningiomas display a variable amount of peritumoral brain edema (PTBE), which can significantly impact perioperative morbidity. The role of microcirculatory disturbances in the pathogenesis of PTBE is still debated. The aim of this study was to microscopically demonstrate and intraoperatively quantify, for the first time, the alterations to microcirculation in PTBE using sidestream dark-field (SDF) imaging.

Methods

Adult patients with WHO grade I meningiomas were recruited over a 9-month period and divided into 2 groups depending on the absence (NE group) or the presence (E group) of PTBE. In vivo intraoperative microcirculation imaging was performed in the peritumoral area before and after microsurgical resection.

Results

Six patients were included in the NE group and 6 in the E group. At the baseline in the NE group, there was a minor decrease in microcirculatory parameters compared to normal reference values, which was probably due to the mass effect. In contrast, microcirculatory parameters in the E group were significantly altered, affecting both vessel density and blood flow values, with a drop of approximately 50% of normal values. Surgical resection resulted in a quasi-normalization of microcirculation parameters in the NE group, whereas in the E group, even if all parameters statistically significantly improved, post-resection values remained considerably inferior to those of the normal reference pattern.

Conclusion

Our study confirmed significant alterations of microcirculatory parameters in PTBE in meningiomas. Further in vivo SDF imaging studies may explore the possible correlation between the severity of these microcirculatory alterations and the postoperative neurological outcome.

Organ dysfunction in cirrhosis: a mechanism involving the microcirculation

INTRODUCTION

Microcirculation is essential for adequate tissue perfusion and organ function. Microcirculatory changes may occur in cirrhosis, inducing loss of multiorgan function. The aim was to evaluate preliver transplantation and postliver transplantation aspects of multiorgan function, microcirculation, inflammatory, and endothelial biomarkers and survival in a controlled study including cirrhotic outpatients.

PATIENTS AND METHODS

We accessed functional capillary density (FCD) and red blood cell acceleration (RBCA) by nailfold videocapillaroscopy. Inflammatory and endothelial biomarkers [interleukin-6 (IL-6), soluble intercellular adhesion molecule-1, endothelin-1, and tumor necrosis factor-α] were analyzed. Cerebral and renal functions were assessed to represent organ dysfunction and regression analyses were carried out. Receiver operating characteristic curves were constructed and survival Kaplan-Meier analysis was carried out.

RESULTS

Fifty-four patients and 18 controls were included. Inflammatory and endothelial markers increased in advanced disease. FCD was reduced and RBCA was progressively lower according to disease severity. RBCA correlated inversely with inflammatory and endothelial biomarkers, and directly with renal function. The presence of hepatic encephalopathy correlated inversely with RBCA and directly with IL-6 and endothelin-1. In multivariate analysis, RBCA was an independent factor for organ dysfunction. The area under the receiver operating chartacteristic curve for IL-6 for survival was 0.74 (0.59-0.89), P=0.05. Transplant-free survival was 97.5% for values under 5.78 ng/ml (IL-6 best cutoff) and 83.9% above 5.78 ng/ml, log-rank=0.018. Eleven patients underwent transplantation, with an overall improvement in microcirculatory function.

CONCLUSION

Our results suggest a mechanism of organ damage in cirrhosis, where microcirculatory dysfunction could be correlated to inflammatory and endothelial biomarkers, and loss of multiorgan function. IL-6 seems to be an important survival marker of inflammation. Liver transplantation improved microcirculatory dysfunction, corroborating this hypothesis.

Hyperoxia does not affect oxygen delivery in healthy volunteers while causing a decrease in sublingual perfusion

Objective

To determine the human dose‐response relationship between a stepwise increase in arterial oxygen tension and its associated changes in DO₂ and sublingual microcirculatory perfusion.

Methods

Fifteen healthy volunteers breathed increasing oxygen fractions for 10 minutes to reach arterial oxygen tensions of baseline (breathing air), 20, 40, 60 kPa, and max kPa (breathing oxygen). Systemic hemodynamics were measured continuously by the volume‐clamp method. At the end of each period, the sublingual microcirculation was assessed by SDF.

Results

Systemic DO₂ was unchanged throughout the study (P_slope = .8). PVD decreased in a sigmoidal fashion (max −15% while breathing oxygen, SD18, P_slope = .001). CI decreased linearly (max −10%, SD10, P_slope < .001) due to a reduction in HR (max −10%, SD7, P_slope = .009). There were no changes in stroke volume or MAP. Most changes became apparent above an arterial oxygen tension of 20 kPa.

Conclusions

In healthy volunteers, supraphysiological arterial oxygen tensions have no effect on systemic DO₂. Sublingual microcirculatory PVD decreased in a dose‐dependent fashion. All hemodynamic changes appear negligible up to an arterial oxygen tension of 20 kPa.

Feasibility of optical coherence tomography angiography to assess changes in retinal microcirculation in ovine haemorrhagic shock

BACKGROUND

This study aimed to investigate the feasibility of optical coherence tomography angiography (OCT-A) for quantitative analysis of flow density to assess changes in retinal perfusion in an experimental model of haemorrhagic shock.

METHODS

Haemorrhagic shock was induced in five healthy, anaesthetized sheep by stepwise blood withdrawal of 3 × 10 ml∙kg- 1 body weight. OCT-A imaging of retinal perfusion was performed using an OCT device. Incident dark-field illumination microscopy videos were obtained for the evaluation of conjunctival microcirculation. Haemodynamic variables and flow density data in the OCT angiogram were analysed before and during progressive haemorrhage resulting in haemorrhagic shock as well as after fluid resuscitation with 10 ml∙kg- 1 body weight of balanced hydroxyethyl starch solution (6% HES 130/0.4). Videos of the conjunctival microcirculation were recorded at baseline, in haemorrhagic shock, and after resuscitation. Data are presented as median with interquartile range. Comparisons between time points were made using Friedman's test and the degree of correlation between two variables was expressed as Spearman's rank correlation coefficient.

RESULTS

Mean arterial pressure and cardiac index (CI) decreased and lactate concentration increased after induction of shock, and haemodynamics recovered after resuscitation. The flow density in the superficial retinal OCT angiogram decreased significantly after shock induction (baseline 44.7% (40.3; 50.5) vs haemorrhagic shock 34.5% (32.8; 40.4); P = 0.027) and recovered after fluid resuscitation (46.9% (41.7; 50.7) vs haemorrhagic shock; P = 0.027). The proportion of perfused vessels of the conjunctival microcirculation showed similar changes. The flow density measured using OCT-A correlated with the conjunctival microcirculation (perfused vessel density: Spearman's rank correlation coefficient ρ = 0.750, P = 0.001) and haemodynamic parameters (CI: ρ = 0.693, P < 0.001).

CONCLUSIONS

Retinal flow density, measured using OCT-A, significantly decreased in shock and recovered after fluid therapy in an experimental model of haemorrhagic shock. OCT-A is feasible to assess changes in retinal perfusion in haemorrhagic shock and fluid resuscitation.

The impact of endotoxin on jejunal tissue oxygenation

OBJECTIVE

We examined the effects of systemic ETX on jejunal mucoal microcirculatory parameters in anesthetized pigs.

METHODS

Jejunal mucosal tissue PO₂ was measured employing Clark-type surface oxygen electrodes. Oxygen saturation of jejunal microvascular hemoglobin was determined by tissue reflectance spectrophotometry. Jejunal microcirculatory blood flow was assessed by laser Doppler flowmetry. Microvascular conductance and rhythmical oscillation of the tissue PO₂ were calculated. Systemic hemodynamic variables, mesenteric venous and systemic acid base and blood gas variables, and lactate measurements were recorded. Measurements were taken at BL and after Escherichia coli LPS administration in 20 minutes intervals for 110 minutes.

RESULTS

ETX infusion led to a significant (P<.05) decrease of PO₂ muc (from 24±4 to 8±4 mm Hg) and microvascular HbO₂ (from 41±13 to 24±12%). Microcirculatory conductivity increased in ETX animals, microvascular blood flow remained unchanged (PU; from 228±45 to 232±58). ETX induced an increase in oscillation frequency of mucosal tissue oxygenation.

CONCLUSIONS

Endotoxinemia resulted in a significant depression of mucosal tissue oxygenation despite a constant microcirculatory blood flow. This impairment of tissue oxygenation resulted in an increase in the vasomotion pattern in a futile attempt to counteract the undersupply of oxygen to the jejunal tissue.

Review article: the role of the microcirculation in liver cirrhosis

BACKGROUND

Intrahepatic microvascular derangements and microcirculatory dysfunction are key in the development of liver cirrhosis and its associated complications. While much has been documented relating to cirrhosis and the dysfunction of the microcirculation in the liver parenchyma, far less is known about the state of the extrahepatic microcirculation and the role this may have in the pathogenesis of multiple organ failure in end stage liver cirrhosis.

AIM

To provide an update on the role of the microcirculation in the pathophysiology of cirrhosis and its associated complications and briefly discuss some of the imaging techniques which may be used to directly investigate the microcirculation.

METHODS

A Medline literature search was conducted using the following search terms: 'cirrhosis', 'microcirculation', 'circulation', 'systemic', 'inflammation', 'peripheral', 'hepatorenal' and 'hepatopulmonary'.

RESULTS

Significant heterogeneous microvascular alterations exist in patients with cirrhosis. Data suggest that the systemic inflammation, associated with advanced cirrhosis, induces microcirculatory dysregulation and contributes to haemodynamic derangement. The resultant vasoconstriction and hypoperfusion in the systemic extrahepatic microvasculature, is likely to be instrumental in the pathophysiology of organ failure in decompensated cirrhosis, however the mechanistic action of vasoactive agents used to correct the circulatory disturbance of advanced cirrhosis is poorly understood.

CONCLUSIONS

Further research into the role of the microcirculation in patients with liver cirrhosis, will improve physicians understanding of the pathophysiology of cirrhosis, and may provide a platform for real time evaluation of an individual's microcirculatory response to vasoactive mediators, thus guiding their therapy.

Branko Furst's Radical Alternative: Is the Heart Moved by the Blood, Rather Than Vice Versa?

We examine key evidence against the standard cardiac function model and describe Branco Furst's alternative model with its implications for therapy and further exploration.

Regulation of angiopoietin-2 secretion from human pulmonary microvascular endothelial cells

INTRODUCTION

Sepsis is characterized by dysregulated systemic inflammation and cytokine storm. Angiopoietin-2 (Ang-2) is known to closely correlate with severity of sepsis-related acute lung injury and mortality. The aim of this study was to clarify the mechanisms involved in Ang-2 secretion to better understand the pathophysiology of sepsis.

MATERIALS AND METHODS

The concentration of Ang-2 was assessed in culture medium of pulmonary microvascular endothelial cells in the presence or absence of Gram-positive bacteria cell wall components [lipoteichoic acid (LTA) and peptidoglycan (PGN)] stimulation at different time points ranging from 15 minutes to 24 hours. Constitutive and LTA-PGN-stimulated Ang-2 level changes were also assessed after cells were pretreated with different pathway inhibitors for 1 hour.

RESULTS

Two distinctive mechanisms of Ang-2 secretion, constitutive and stimulated secretion, were identified. Constitutive secretion resulted in slow but continuous increase in Ang-2 in culture medium over time. It was regulated by 3'5'-cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA)-Ca²⁺ and nitric oxide (NO)-3'5'-cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG)-Ca²⁺ pathways and partially regulated by N-ethyl-maleimide-sensitive factor-Ca²⁺ pathways. LTA-PGN stimulation caused rapid and potent increase followed by gradual decrease of Ang-2. It was partially regulated by both Ral A-phospholipase D and NSF-Ca²⁺ pathways.

CONCLUSIONS

We demonstrated characteristics and involved pathways for two distinctive secretory mechanisms, constitutive and stimulated, of Ang-2 in pulmonary microvascular endothelial cells. Considering the close correlation of Ang-2 with sepsis outcomes, our findings provide a better understanding of an important mechanism associated with sepsis pathophysiology and identify possible therapeutic targets to improve outcomes in the potentially lethal disease.

The Correlation Between Arterial Lactate and Venous Lactate in Patients With Sepsis and Septic Shock

BACKGROUND

Applying peripheral venous lactate instead of arterial lactate in clinical practice is questionable because of deviation between both values. We aimed to find the relationship between the arterial lactate and the peripheral venous lactate before reasoned that the venous lactate could be used in substitution to the arterial lactate in sepsis.

METHODS

We conducted a prospective, cross-sectional study at a university hospital. The patients with sepsis in ICU who required lactate level monitoring were enrolled in this research. The correlation and agreement between arterial lactate (A-LACT) and peripheral venous lactate (V-LACT) were the primary outcomes.

RESULTS

A total of 63 paired samples were collected. The A-LACT and V-LACT were strongly correlated ( r = .934, P < .0001, r² = .873). The regression equation was A-LACT = (0.934 × V-LACT) - 0.236. The mean difference between V-LACT and A-LACT was 0.66 ± 1.53 mmol/L. The 95% limits of agreement were between -3.66 and 2.33 mmol/L. The V-LACT ≥ 4 mmol/L can predict A-LACT level ≥ 4 mmol/L with 87.5% sensitivity and 91.5% specificity, and the area under receiver operating characteristic curve was 0.948.

CONCLUSION

The present study demonstrated a strong correlation between A-LACT and V-LACT, but an agreement between both parameters was poor. We suggest not to use the V-LACT in substitution to the A-LACT in sepsis regarding the absolute value and clearance rate, but the V-LACT ≥ 4.5 mmol/L may be used for predicting the A-LACT ≥ 4 mmol/L.

Endothelial and Microcirculatory Function and Dysfunction in Sepsis

The microcirculation is a series of arterioles, capillaries, and venules that performs essential functions of oxygen and nutrient delivery, customized to the unique physiologic needs of the supplied organ. The homeostatic microcirculatory response to infection can become harmful if overactive and/or dysregulated. Pathologic microcirculatory dysfunction can be directly visualized by intravital microscopy or indirectly measured via detection of circulating biomarkers. Although several treatments have been shown to protect the microcirculation during sepsis, they have not improved patient outcomes when applied indiscriminately. Future outcomes-oriented studies are needed to test sepsis therapeutics when personalized to a patient's microcirculatory dysfunction.

Effects of early hemodynamic resuscitation on left ventricular performance and microcirculatory function during endotoxic shock

Background

Microcirculation and macrohemodynamics are severely compromised during septic shock. However, the relationship between these two compartments needs to be further investigated. We hypothesized that early resuscitation restores left ventricular (LV) performance and microcirculatory function but fails to prevent metabolic disorders. We studied the effects of an early resuscitation protocol (ERP) on LV pressure/volume loops-derived parameters, sublingual microcirculation, and metabolic alterations during endotoxic shock.

Methods

Twenty-five pigs were randomized into three groups: LPS group: Escherichia coli lipopolysaccharide (LPS); ERP group: LPS + ERP based on volume expansion, dobutamine, and noradrenaline infusion; Sham group. LV pressure/volume-derived parameters, systemic hemodynamics, sublingual microcirculation, and metabolic profile were assessed at baseline and after completing the resuscitation protocol.

Results

LPS significantly decreased LV end-diastolic volume, myocardial contractility, stroke work, and cardiac index (CI). Early resuscitation preserved preload, and myocardial contractility, increased CI and heart rate (p < .05). LPS severely diminished sublingual microvascular flow index (MFI), perfused vascular density (PVD), and the proportion of perfused vessels (PPV), while increased the heterogeneity flow index (HFI) (p < .05). Despite MFI was relatively preserved, MVD, PVD, and HFI were significantly impaired after resuscitation (p < .05). The macro- and microcirculatory changes were associated with increased lactic acidosis and mixed venous O₂ saturation when compared to baseline values (p < .05). The scatter plot between mean arterial pressure (MAP) and MFI showed a biphasic relationship, suggesting that the values were within the limits of microvascular autoregulation when MAP was above 71 ± 6 mm Hg (R² = 0.63).

Conclusions

Early hemodynamic resuscitation was effective to restore macrohemodynamia and myocardial contractility. Despite MAP and MFI were relatively preserved, the persistent microvascular dysfunction could explain metabolic disorders. The relationship between micro- and systemic hemodynamia and their impact on cellular function and metabolism needs to be further studied during endotoxic shock.

Electronic supplementary material

The online version of this article (doi:10.1186/s40635-015-0049-y) contains supplementary material, which is available to authorized users.

A new device for continuous assessment of gut perfusion: proof of concept on a porcine model of septic shock

INTRODUCTION

We evaluate an innovative device consisting of an enteral feeding tube equipped with a photoplethysmography (PPG) sensor in contact with the duodenal mucosa. This study aims to determine if the PPG signal, composed of a continuous (PDC) and a pulsatile part (PAC), is a reliable method to assess gut perfusion in a porcine model of septic shock.

METHOD

Fourteen piglets were anesthetized and mechanically ventilated. They were randomly assigned to two groups: the nonseptic (NS) group received an infusion of Ringer's lactate solution (RL) alone, the septic (S) group received in addition a suspension of live Pseudomonas aeruginosa. Heart rate (HR), pulse oximetry (SpO2), mean arterial pressure (MAP), cardiac index (CI) and serum lactates were recorded and gut microcirculation (GM) was monitored with a laser Doppler probe applied on the duodenal serosa. PDC and PAC were given by the PPG probe inserted in the duodenum. Data was collected every 15 minutes (t0, t15…) during 150 minutes (t150). After administration of the bacteria suspension (t0), resuscitation maneuvers were performed following a defined algorithm. GM PAC, and PDC were expressed as variation from baseline (GMvar, PACvar, PDCvar). Analysis of variance (ANOVA) with repeated measures was performed to compare hemodynamic variables, with Bonferroni correction as post hoc analysis on t0, t60 and t150.

RESULTS

One piglet was withdrawn from analysis due to a defective probe. S group (six piglets) received resuscitation therapy while NS group (seven piglets) did not. A significant group effect was found for the all parameters except HR. Post hoc analysis found a significant decrease for GM and PAC at t60. The correlation between PAC, PDC and microcirculatory parameters were as follows: rPACvar-GMvar = 0.496, P <0.001, rPDCvar-GMvar = 0.244; P = 0.002. In the septic group, correlations were as follows: rPAC-lactate = -0.772, P <0.001; rPDC-lactate = -0.681, P <0.01). At the onset of shock, a decrease of PAC, PDC and GM occurred before the alteration of MAP.

CONCLUSIONS

PAC and PDC decreased at the onset of shock and were correlated with GM and lactate. These results confirm that PPG signal reliably reflects the early perfusion alteration of the gut. Further studies should assess the clinical use of this device.

Deeper penetration of erythrocytes into the endothelial glycocalyx is associated with impaired microvascular perfusion

Changes in endothelial glycocalyx are one of the earliest changes in development of cardiovascular disease. The endothelial glycocalyx is both an important biological modifier of interactions between flowing blood and the vessel wall, and a determinant of organ perfusion. We hypothesize that deeper penetration of erythrocytes into the glycocalyx is associated with reduced microvascular perfusion. The population-based prospective cohort study (the Netherlands Epidemiology of Obesity [NEO] study) includes 6,673 middle-aged individuals (oversampling of overweight and obese individuals). Within this cohort, we have imaged the sublingual microvasculature of 915 participants using sidestream darkfield (SDF) imaging together with a recently developed automated acquisition and analysis approach. Presence of RBC (as a marker of microvascular perfusion) and perfused boundary region (PBR), a marker for endothelial glycocalyx barrier properties for RBC accessibility, were assessed in vessels between 5 and 25 µm RBC column width. A wide range of variability in PBR measurements, with a mean PBR of 2.14 µm (range: 1.43–2.86 µm), was observed. Linear regression analysis showed a marked association between PBR and microvascular perfusion, reflected by RBC filling percentage (regression coefficient β: −0.034; 95% confidence interval: −0.037 to −0.031). We conclude that microvascular beds with a thick (“healthy”) glycocalyx (low PBR), reflects efficient perfusion of the microvascular bed. In contrast, a thin (“risk”) glycocalyx (high PBR) is associated with a less efficient and defective microvascular perfusion.

The microcirculation is preserved in emergency department low-acuity sepsis patients without hypotension

OBJECTIVES

Microcirculatory dysfunction plays an important role in sepsis pathophysiology. Previous studies using sidestream dark-field (SDF) imaging have demonstrated microcirculatory flow abnormalities in patients with septic shock; however, the microcirculation is relatively unstudied in lower-acuity sepsis patients. The hypothesis was that patients with sepsis, but without hypotension, will demonstrate signs of flow abnormalities compared to noninfected control patients.

METHODS

This was a prospective, observational study in a convenience sample of patients with sepsis and noninfected controls, conducted in three urban, tertiary care emergency departments (EDs) in the United States. Sepsis was defined as suspected infection plus two or more systemic inflammatory response syndrome (SIRS) criteria; those with hypotension were excluded. Noninfected controls were ED patients without infection and without SIRS criteria. SDF imaging was obtained in all study patients during ED evaluation. Recommended microcirculatory flow parameters were measured, and the difference in these measures between sepsis patients and noninfected controls were calculated. The authors also correlated microcirculatory flow parameters with patient variables, including serum lactate.

RESULTS

A total of 106 patients were enrolled: 63 with sepsis and 43 noninfected controls. There were no differences in microcirculatory flow scores between sepsis patients and noninfected controls. Median microvascular flow index (MFI; with interquartile range [IQR] was 3.00 (IQR = 2.73 to 3.00) in sepsis patients versus 2.93 (IQR = 2.73 to 3.00) in control patients (p = 0.33), and mean proportion of perfused small vessels (PPV) was 91.5% (95% CI = 89.7% to 93.3%) versus 91.8% (95% CI = 89.7% to 93.9%), with a mean difference of 0.3% (95% CI = -2.5% to 3.1%; p = 0.84). Similarly, there were no significant differences in total vessel density, perfused vessel density, or heterogeneity index (HI). In the subset of infected patients for whom serum lactates were obtained (n % 37), MFI and PPV were negatively correlated with elevated serum lactate values: r = -0.32, p = 0.04; and r = -0.44, p < 0.01, respectively.

CONCLUSIONS

Measureable microcirculatory flow abnormalities were not observed in patients with early sepsis in the absence of hypotension. However, microcirculatory abnormalities were correlated with elevated serum lactate in normotensive sepsis patients, supporting the notion that impaired microcirculatory flow is coupled with cellular distress.

Confocal laser endomicroscopy reliably detects sepsis-related and treatment-associated changes in intestinal mucosal microcirculation

BACKGROUND

Microcirculatory alterations play a central role in the pathophysiology of sepsis. We investigated probe-based confocal laser endomicroscopy (pCLE) to assess alterations in mucosal microcirculatory perfusion in vivo in a porcine model of septic shock and in patients fulfilling consensus criteria for severe sepsis.

METHODS

Septic shock was induced using a faecal peritonitis model in anaesthetized, mechanically ventilated pigs. Mucosal microcirculation was assessed using pCLE in the stomach, duodenum, terminal ileum, and rectum. Duodenal microcirculation was further evaluated in 10 patients with severe sepsis and in 8 healthy controls to quantify capillary diameter, capillary length, and functional capillary density (FCD).

RESULTS

In the animal model, FCD was markedly decreased in duodenal (P<0.001), ileal (P<0.001), gastric (P<0.001), and rectal mucosa (P<0.005) 4 h after induction of sepsis. After volume therapy, FCD partially recovered to 90.0% (duodenum), 94.4% (ileum), 95.4% (gastric), and 97% (rectum) of baseline values, indicating decoupling of microvascular and macrovascular flow. In septic patients, the mean capillary diameter (P<0.01) and FCD (P<0.05) in duodenal mucosa were decreased compared with healthy controls.

CONCLUSIONS

pCLE reliably detected and quantified microcirculatory alterations in the gastrointestinal mucosa in a porcine model of sepsis and in patients with severe sepsis. Our data suggest that pCLE is a promising tool to assess the efficacy of therapeutic interventions on mucosal microcirculation in real-time, even in the clinical context.

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

OBJECTIVES

The 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).

METHODS

This 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.

RESULTS

Thirty-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/mm(2); 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 (R(2) = .016, P = .47), MAP (R(2) = .013, P = .54), or VAS scores. The ICC was 0.954.

CONCLUSIONS

Sublingual tissue perfusion is diminished in ADHF but increases with treatment. It may represent a quantitative way to evaluate ADHF in the ED setting.

Bladder mucosal CO2 compared with gastric mucosal CO2 as a marker for low perfusion states in septic shock

Recent reports indicate the possible role of bladder CO(2) as a marker of low perfusion states. To test this hypothesis, shock was induced in six beagle dogs with 1 mg/kg of E. coli lipopolysaccharide, gastric CO(2) (CO(2)-G) was measured with a continuous monitor, and a pulmonary catheter was inserted in the bladder to measure CO(2) (CO(2)-B). Levels of CO(2)-B were found to be lower than those of CO(2)-G, with a mean difference of 36.8 mmHg (P < 0.001), and correlation between both measurements was poor (r(2) = 0.16). Even when the correlation between CO(2)-G and ΔCO(2)-G was narrow (r(2) = 0.86), this was not the case for the relationship between CO(2)-B and ΔCO(2)-B (r(2) = 0.29). Finally, the correlation between CO(2)-G and base deficit was good (r(2) = 0.45), which was not the case with the CO(2)-B correlation (r(2) = 0.03). In our experience, bladder CO(2) does not correlate to hemodynamic parameters and does not substitute gastric CO(2) for detection of low perfusion states.

Effects of different leukocyte subpopulations and flow conditions on leukocyte accumulation during reperfusion

BACKGROUND/AIMS

The study examined the interdependent effects of shear stress and different leukocyte subpopulations on endothelial cell activation and cell interactions during low flow and reperfusion.

METHODS

Human umbilical venous endothelial cells were perfused with either neutrophils or monocytes at different shear stress (2-0.25 dyn/cm(2)) and adhesion was quantified by microscopy. Effects of adherent neutrophils and monocytes on endothelial cell adhesion molecule expression were analyzed by flow cytometry after 4-hour static coincubation. After coincubation, the cocultures were reperfused with labeled neutrophils at 2 dyn/cm(2) and their adhesion was quantified selectively. For the control, endothelium monocultures with and without lipopolysaccharide activation were used.

RESULTS

At 2 dyn/cm(2), adhesion did not exceed baseline levels on nonactivated endothelium. Decreasing shear stress to 0.25 dyn/cm(2) largely increased the adhesion of both leukocyte subpopulations, similar to the effect of lipopolysaccharide at 2 dyn/cm(2). However, only adherent monocytes increased adhesion molecule expression, whereas neutrophils had no effect. As a functional consequence, adherent monocytes largely increased neutrophil adhesion during reperfusion, whereas adherent neutrophils did not.

CONCLUSION

Compromised shear stress is an autonomous trigger of leukocyte adhesion even in the absence of additional activators. Exceeding this immediate effect, adherent monocytes induce further endothelial activation and enhance further neutrophil adhesion during reperfusion.

Ophthalmic lesions in neonatal foals evaluated for nonophthalmic disease at referral hospitals

OBJECTIVE

To determine types and frequency of ophthalmic lesions detected in neonatal foals evaluated for nonophthalmic disease at 3 veterinary referral hospitals and to investigate associations between systemic and ophthalmic diseases in these foals.

DESIGN

Prospective cross-sectional study.

ANIMALS

70 foals < 30 days old.

PROCEDURES

Complete ophthalmic examinations were performed. Signalment, clinical signs, mentation during ophthalmic examination, results of clinicopathologic tests, and diagnosis of systemic disease were recorded. Descriptive data analysis including a χ(2) test for associations was performed.

RESULTS

Most foals (39/70 [55.7%]) with systemic disease had ≥ 1 ophthalmic lesion detected. Of the 39 foals with ophthalmic disease, 24 (61.5%) had potentially vision-threatening lesions. Clinically important abnormalities included conjunctival hyperemia or episcleral injection (30/70 [42.9%]), uveitis (18/70 [25.7%]), ulcerative keratitis (13/70 [18.6%]), nonulcerative keratitis (10/70 [14.3%]), entropion (8/70 [11.4%]), retinal hemorrhage (8/70 [11.4%]), and cataract (6/70 [8.6%]). Foals with sepsis were significantly more likely to have uveitis than were those without sepsis. Foals with sepsis and uveitis were also significantly less likely to survive to discharge than were foals that had sepsis without uveitis. Acquired ophthalmic disease (detected in 37/70 [52.9%] foals) was significantly more common than congenital ophthalmic disease (detected in 9/70 [12.9%]).

CONCLUSIONS AND CLINICAL RELEVANCE

Ophthalmic lesions were detected in 55.7% of neonatal foals with systemic disease. Acquired ophthalmic disease was more commonly detected than congenital ophthalmic disease. Foals with sepsis were more likely to have uveitis than were foals without sepsis. A complete ophthalmic examination is indicated in neonatal foals evaluated for systemic disease.

Physiopathology of the cochlear microcirculation

Normal blood supply to the cochlea is critically important for establishing the endocochlear potential and sustaining production of endolymph. Abnormal cochlear microcirculation has long been considered an etiologic factor in noise-induced hearing loss, age-related hearing loss (presbycusis), sudden hearing loss or vestibular function, and Meniere's disease. Knowledge of the mechanisms underlying the pathophysiology of cochlear microcirculation is of fundamental clinical importance. A better understanding of cochlear blood flow (CoBF) will enable more effective management of hearing disorders resulting from aberrant blood flow. This review focuses on recent discoveries and findings related to the physiopathology of the cochlear microvasculature.

Goal-directed therapy in small animal critical illness

Monitoring critically ill patients can be a daunting task even for experienced clinicians. Goal-directed therapy is a technique involving intensive monitoring and aggressive management of hemodynamics in patients with high risk of morbidity and mortality. The aim of goal-directed therapy is to ensure adequate tissue oxygenation and survival. This article reviews commonly used diagnostics in critical care medicine and what the information gathered signifies and discusses clinical decision making on the basis of diagnostic test results. One example is early goal-directed therapy for severe sepsis and septic shock. The components and application of goals in early goal-directed therapy are discussed.

Effect of percutaneous transluminal angioplasty on tissue oxygenation in ischemic diabetic feet

Percutaneous transluminal angioplasty (PTA) has been performed as an alternative to bypass surgery for improving tissue oxygenation in ischemic diabetic feet because the former is less invasive than the latter. The purpose of this study was to evaluate the effect of PTA on tissue oxygenation in ischemic diabetic feet. This study included 29 ischemic diabetic feet, as determined by a transcutaneous oxygen pressure (TcPO(2) )<30 mmHg. The PTA was carried out in 29 limbs. The PTA procedure was considered successful, acceptable, and failed when residual stenosis was<30%, between 30 and 50%, and>50%, respectively. For evaluation of tissue oxygenation, the foot TcPO(2) was measured before PTA and weekly for 6 weeks after PTA. Immediately after PTA, 26 feet were evaluated as being successful and the remaining three as acceptable. Before PTA, the average foot TcPO(2) was 12.7 ± 8.9 mmHg. The TcPO(2) values were increased to 43.6 ± 24.1, 51.0 ± 22.6, 58.3 ± 23.0, 61.3 ± 24.2, 59.0 ± 22.2, and 53.8 ± 21.0 mmHg 1, 2, 3, 4, 5, and 6 weeks after PTA, respectively (p<0.01). The PTA procedure significantly increases tissue oxygenation in ischemic diabetic feet. The maximal level of tissue oxygenation was measured on the fourth week following PTA.

Withdrawing intra-aortic balloon pump support paradoxically improves microvascular flow

INTRODUCTION

The Intra-Aortic Balloon Pump (IABP) is frequently used to mechanically support the heart. There is evidence that IABP improves microvascular flow during cardiogenic shock but its influence on the human microcirculation in patients deemed ready for discontinuing IABP support has not yet been studied. Therefore we used sidestream dark field imaging (SDF) to test our hypothesis that human microcirculation remains unaltered with or without IABP support in patients clinically ready for discontinuation of mechanical support.

METHODS

We studied 15 ICU patients on IABP therapy. Measurements were performed after the clinical decision was made to remove the balloon catheter. We recorded global hemodynamic parameters and performed venous oximetry during maximal IABP support (1:1) and 10 minutes after temporarily stopping the IABP therapy. At both time points, we also recorded video clips of the sublingual microcirculation. From these we determined indices of microvascular perfusion including perfused vessel density (PVD) and microvascular flow index (MFI).

RESULTS

Ceasing IABP support lowered mean arterial pressure (74 ± 8 to 71 ± 10 mmHg; P = 0.048) and increased diastolic pressure (43 ± 10 to 53 ± 9 mmHg; P = 0.0002). However, at the level of the microcirculation we found an increase of PVD of small vessels <20 μm (5.47 ± 1.76 to 6.63 ± 1.90; P = 0.0039). PVD for vessels >20 μm and MFI for both small and large vessels were unaltered. During the procedure global oxygenation parameters (ScvO2/SvO2) remained unchanged.

CONCLUSIONS

In patients deemed ready for discontinuing IABP support according to current practice, SDF imaging showed an increase of microcirculatory flow of small vessels after ceasing IABP therapy. This observation may indicate that IABP impairs microvascular perfusion in recovered patients, although this warrants confirmation.

Measurements of microvascular perfusion in healthy anesthetized dogs using orthogonal polarization spectral imaging

OBJECTIVE

To determine normal microvascular assessment parameters for healthy, anesthetized dogs.

DESIGN

Prospective investigational descriptive study.

SETTING

University Teaching Hospital.

ANIMALS

Fifteen client-owned, systemically healthy dogs that were undergoing general anesthesia for an elective procedure.

INTERVENTIONS

A sidestream dark-field videomicroscope probe was placed in the mouth at the mucogingival junction above the canine tooth and 3 video recordings of the microcirculation were made for later analysis by 2 independent, blinded reviewers.

MEASUREMENTS AND MAIN RESULTS

The videos were analyzed to determine the total vessel density, proportion of perfused vessels, microcirculatory flow index, and perfused vessel density. A range of values for these indices were obtained and reported.

CONCLUSIONS

The microcirculation of normal dogs is readily observable using the videomicroscope and recorded video segments can be used to determine microcirculatory measurements. These values may prove useful for comparison in future studies that examine canine microcirculatory parameters.

Functional echocardiography; from physiology to treatment

Functional echocardiography (fECHO) is the bedside use of ultrasound to longitudinally assess myocardial function, systemic and pulmonary blood flow, and intra and extracardiac shunts. This review will focus on fECHO as a tool for the clinician to assess the hemodynamic condition of sick neonates and describe situations where fECHO can help determine a pathophysiological choice for cardiovascular support. The very low birth weight infant with hypotension during the first 24h of life, assessment and monitoring of the ductus arteriosus, assessment and response to treatment of infants with pulmonary hypertension, the infant with perinatal asphyxia and the infant with sepsis and cardiovascular compromise are reviewed. Close cooperation with pediatric cardiology, proper logistics and training programs are mandatory to achieve a 24h a day fECHO service run by bedside clinicians.