Microcirculatory Dysfunction in Sepsis

New Insights into the Fluid Management in Patients with Septic Shock

The importance of fluid resuscitation therapy during the early stages of sepsis management is a well-established principle. Current Surviving Sepsis Campaign (SSC) guidelines recommend the early administration of intravenous crystalloid fluids for sepsis-related hypotension or hyperlactatemia due to tissue hypoperfusion, within the first 3 h of resuscitation and suggest using balanced solutions (BSs) instead of normal saline (NS) for the management of patients with sepsis or septic shock. Studies comparing BS versus NS administration in septic patients have demonstrated that BSs are associated with better outcomes including decreased mortality. After initial resuscitation, fluid administration has to be judicious in order to avoid fluid overload, which has been associated with increased mortality, prolonged mechanical ventilation, and worsening of acute kidney injury. The "one size fits all" approach may be "convenient" but it should be avoided. Personalized fluid management, based on patient-specific hemodynamic indices, provides the foundations for better patient outcomes in the future. Although there is a consensus on the need for adequate fluid therapy in sepsis, the type, the amount of administered fluids, and the ideal fluid resuscitation strategy remain elusive. Well-designed large randomized controlled trials are certainly needed to compare fluid choices specifically in the septic patient, as there is currently limited evidence of low quality. This review aims to summarize the physiologic principles and current scientific evidence regarding fluid management in patients with sepsis, as well as to provide a comprehensive overview of the latest data on the optimal fluid administration strategy in sepsis.

The Therapeutic Effects of Curcumin in Early Septic Acute Kidney Injury: An Experimental Study

PURPOSE

Sepsis is the leading condition associated with acute kidney injury (AKI) in the hospital and intensive care unit (ICU), sepsis-induced AKI (S-AKI) is strongly associated with poor clinical outcomes. Curcumin possesses an ability to ameliorate renal injury from ischemia-reperfusion, but it is still unknown whether they have the ability to reduce S-AKI. The aim of this study was to investigate the protective effects of curcumin on S-AKI and to assess its therapeutic potential on renal function, inflammatory response, and microcirculatory perfusion.

METHODS

Male Sprague-Dawley (SD) rats underwent cecal ligation and puncture (CLP) to induce S-AKI and immediately received vehicle (CLP group) or curcumin (CLP+Cur group) after surgery. At 12 and 24h after surgery, serum indexes, inflammatory factors, cardiac output (CO), renal blood flow and microcirculatory flow were measured.

RESULTS

Serum levels of creatinine (Scr), cystatin C (CysC), IL-6 and TNF-α were significantly lower in the CLP+Cur group than those in the CLP group (P < 0.05). Treatment with curcumin improved renal microcirculation at 24h by measurement of contrast enhanced ultrasound (CEUS) quantitative parameters [peak intensity (PI); half of descending time (DT/2); area under curve (AUC); P < 0.05]. In histopathological analysis, treatment with curcumin reduced damage caused by CLP.

CONCLUSION

Curcumin can alleviate S-AKI in rats by improving renal microcirculatory perfusion and reducing inflammatory response. Curcumin may be a potential novel therapeutic agent for the prevention or reduction of S-AKI.

Multiple cerebral hemorrhages in sepsis-disseminated intravascular coagulation versus septic embolism: An image report

Background:

Septic emboli are commonly attributed to infective endocarditis and can present with a variety of symptoms including altered mental status and focal neurological deficits. Here, we reviewed images of septic emboli with hemorrhagic conversion in a patient with sepsis and a psoas abscess. We aim to show the classical image findings in septic embolism to brain, which is sparsely described in literature and the report differentiates the septic embolism from disseminated intravascular coagulation which can present with almost identical image findings.

Case Description:

A 53-year-old male patient who was operated on for a right inguinal hernia developed a postoperative wound infection 2 weeks after surgery and was started on IV antibiotics. Despite medical management, his infection did not improve, prompting a computed tomography (CT) scan which revealed a psoas abscess. The abscess was drained, and antibiotics continued. A few days later, he developed altered sensorium prompting a head CT which revealed septic emboli and hemorrhage at the gray-white junction. Cultures grew multidrug-resistant Escherichia coli; the patient was treated with IV tigecycline and improved over the following 4 weeks.

Conclusion:

In patients with a known ongoing infectious process with hemodynamic stability who develop altered mental status in the setting of a normal coagulation profile, D-dimer, positive blood cultures, and absent signs of multiorgan failure, a diagnosis of septic emboli should be entertained. Although CT can reveal macrobleeds, MRI is more sensitive in confirming cerebral microbleeds. Thus, patients in sepsis with unexplained altered sensorium should undergo an MRI of the brain to rule out septic emboli and microbleeds.

Effects of impaired microvascular flow regulation on metabolism-perfusion matching and organ function

Impaired tissue oxygen delivery is a major cause of organ damage and failure in critically ill patients, which can occur even when systemic parameters, including cardiac output and arterial hemoglobin saturation, are close to normal. This review addresses oxygen transport mechanisms at the microcirculatory scale, and how hypoxia may occur in spite of adequate convective oxygen supply. The structure of the microcirculation is intrinsically heterogeneous, with wide variations in vessel diameters and flow pathway lengths, and consequently also in blood flow rates and oxygen levels. The dynamic processes of structural adaptation and flow regulation continually adjust microvessel diameters to compensate for heterogeneity, redistributing flow according to metabolic needs to ensure adequate tissue oxygenation. A key role in flow regulation is played by conducted responses, which are generated and propagated by endothelial cells and signal upstream arterioles to dilate in response to local hypoxia. Several pathophysiological conditions can impair local flow regulation, causing hypoxia and tissue damage leading to organ failure. Therapeutic measures targeted to systemic parameters may not address or may even worsen tissue oxygenation at the microvascular level. Restoration of tissue oxygenation in critically ill patients may depend on restoration of endothelial cell function, including conducted responses.

Dihydromyricetin improves vascular hyporesponsiveness in experimental sepsis via attenuating the over-excited MaxiK and KATP channels

CONTEXT

Dihydromyricetin (DMY) has oxidation resistance, anti-inflammatory and free radical scavenging capabilities. The preventive effects of DMY for vascular hyporeactivity remain unclear.

OBJECTIVE

This study investigates the preventive effects of DMY in vascular hyporeactivity.

MATERIALS AND METHODS

The experimental sepsis was induced by transvenous administration of lipopolysaccharide (LPS) to Sprague-Dawley (SD) rats. DMY-treated rats received daily administration of DMY, 5 μg/kg dissolved in DMSO through the tail vein for 7 days. The invasive mean arterial pressure (MAP) of the caudal ventral artery was measured. Dose-response curves for norepinephrine (NE, doses from 10^-9 to 10^-6M) were obtained in isolated thoracic aorta in a cumulative manner. The function of MaxiK and K_ATP channels were investigated using whole-cell patch clamp recording. The Elisa was adopted to measure the serum concentration of NO, MDA, 3-NT, IL-1β and TNF-α.

RESULTS

The increased MAP in septic rats induced by vasopressor agents was smaller than that in control rats. However, the % of increased MAP induced by vasopressor agents was raised by DMY injection (NE: 20.4 ± 8.495 vs. 15.16 ± 5.195%; AVP: 14.05 ± 2.459 vs. 9.583 ± 2.982%, p < 0.05). The vascular hyporesponsiveness to NE (10^-6M) in vitro. was increased by 51% in LPS + DMY group compared with that in LPS + Con group (2.74 ± 0.81 vs. 1.82 ± 0.92 g, p < 0.05). Charybdotoxin (a potent MaxiK channel blocker) and glibenclamide (a K_ATP channel blocker) pretreatment, instead of 4-aminopyridine (4-AP) and BaCl₂, could diminish the DMY-induced improvement of vasoconstrictor hyporeactivity (ChTX: 73.2 ± 11.8 vs. 71.8 ± 13.5%; Glib: 63.1 ± 12.5 vs. 58.1 ± 13.7%, p > 0.05). DMY blunted the highly sensitized MaxiK and K_ATP channels of arterial smooth muscle cells isolated from the thoracic aorta of LPS rats. DMY decreased the serum level of NO, MDA, IL-1β and TNF-α, which had increased in LPS rats.

DISCUSSION AND CONCLUSIONS

Our results indicate that DMY administration ameliorated the impaired contractility of the rat aorta in experimental sepsis. Such an effect is mediated by normalization of the over-excited MaxiK and K_ATP, channels possibly via oxidative stress inhibition.

Effect of continuous renal-replacement therapy on paraoxonase-1-related variables in patients with acute renal failure caused by septic shock

BACKGROUND

Acute renal failure in patients with sepsis is associated with high mortality. Studies have highlighted alterations in serum paraoxonase-1 in severe infections. However, the published literature has no insight into the clinical evolution of these parameters in patients with sepsis and acute renal failure treated with extra-renal depuration techniques.

METHODS

We studied 25 patients with sepsis and acute renal failure who were treated with continuous renal-replacement therapy. Blood for laboratory analyses was collected at days 0, 1, 2, 5, 7, and 10. We measured serum paraoxonase-1 activity and concentration, lipid profile, aminotransferase activities, pH, and lactate, urea, creatinine and C-reactive protein concentrations. Values were compared with those of 50 healthy individuals.

RESULTS

Patients with sepsis and acute renal failure had lower serum paraoxonase-1 activity, lower high-density lipoprotein cholesterol concentrations, and higher serum paraoxonase-1 concentrations than the control group. We found a significant inverse correlation between serum paraoxonase-1 concentrations and the Acute Physiology And Chronic Health Evaluation II score in survivors as well as non-survivors, and a significant inverse correlation between serum paraoxonase-1 concentrations and the Sequential Organ Failure Assessment score only in survivors. Extra-renal depuration techniques produced a further increase in this enzyme related to the duration of treatment, and to serum urea concentration.

CONCLUSION

Our results show an inverse relationship between the concentration of paraoxonase-1 and the disease severity of patients with renal failure caused by septic shock. These results highlight relationships between paraoxonase-1 and infectious diseases and sepsis, with insights into potential clinical evolution of treatment.

Effects and influencing factors on hemorheological variables taken into consideration in surgical pathophysiology research

In surgical pathophysiology ischemia-reperfusion, inflammatory processes, sepsis, vascular interventions, tissue trauma, shock, all mean conditions in which hemorheological parameters show alterations. Despite of numerous clinical and experimental studies, the in vivo hemorheology is not completely understood yet, and several fundamental questions still need to be answered. Investigating these issues, experimental surgical models are important, in point of view of the translational research as well. In this paper we aimed to make an attempt on summarizing the possible factors and conditions that might have an effect on hemorheological results in experimental surgical studies. Hemorheological parameters show alterations in surgical pathophysiological processes in a complex way. However, the changes are dominantly non-specific. Standardized experimental conditions, related to the experimental animal (species, animal welfare) anesthesia-medications, operation, sampling and, if applicable, conditions of the postoperative period, are inevitable for a safe assessment of valuable (hemorheological) results. Parallel investigations - such as microcirculatory monitoring, imaging techniques, other laboratory methods, histomorphology- have great importance, together with individual analysis of changes, for a better understanding of the changes and for comparability with clinical results.

Pathophysiology of the cardio-renal syndromes types 1-5: An uptodate

According to the recent definition proposed by the Consensus conference on Acute Dialysis Quality Initiative Group, the term cardio-renal syndrome (CRS) has been used to define different clinical conditions in which heart and kidney dysfunction overlap. Type 1 CRS (acute cardio- renal syndrome) is characterized by acute worsening of cardiac function leading to AKI (5, 6) in the setting of active cardiac disease such as ADHF, while type - 2 CRS occurs in a setting of chronic heart disease. Type 3 CRS is closely link to acute kidney injury (AKI), while type 4 represent cardiovascular involvement in chronic kidney disese (CKD) patients. Type 5 CRS represent cardiac and renal involvement in several diseases such as sepsis, hepato - renal syndrome and immune - mediated diseases.

Fluid Resuscitation in Severe Sepsis

Since its original description in 1832, fluid resuscitation has become the cornerstone of early and aggressive treatment of severe sepsis and septic shock. However, questions remain about optimal fluid composition, dose, and rate of administration for critically ill patients. This article reviews pertinent physiology of the circulatory system, pathogenesis of septic shock, and phases of sepsis resuscitation, and then focuses on the type, rate, and amount of fluid administration for severe sepsis and septic shock, so providers can choose the right fluid, for the right patient, at the right time.

Early hemorheological changes in a porcine model of intravenously given E. coli induced fulminant sepsis

The pathophysiology of hemorheological and microcirculatory disturbances in septic process -mostly during the early hours- still not clarified in all the details, yet. In anesthetized pigs living E. coli (ATCC 25922 strain) was administered intravenously with an increasing concentration and the animals were observed for 8 hours. Before the intervention and in every 2 hours arterial (cannulated femoral artery) and venous (cannulated external jugular vein) blood samples were collected for hemorheological laboratory tests: blood and plasma viscosity, ESR, leukocyte anti-sedimentation rate, erythrocyte deformability (together with osmoscan parameters) and erythrocyte aggregation (using light-transmission and laser back-scattering methods) Control animals were stable over the 8-hour anesthesia, while septic animals died by the 6th hours in a fulminant sepsis. Over the experimental period, the tendency of impairment in erythrocyte deformability (together with osmotic gradient ektacytometry parameters) and the controversial decreasing of erythrocyte aggregation values (declining all aggregation index values, elongating t1/2) were well detected in this porcine model during the early hours (4- 6) of fulminant sepsis. The in vitro effect of these bacteria on erythrocytes' micro-rheological parameter was similar: decreasing red blood cell deformability and lowering aggregation. Further studies are needed to clarify the early micro-rheological changes of bacteremia and the developing sepsis.

Microcirculatory dysfunction and tissue oxygenation in critical illness

Severe sepsis is defined by organ failure, often of the kidneys, heart, and brain. It has been proposed that inadequate delivery of oxygen, or insufficient extraction of oxygen in tissue, may explain organ failure. Despite adequate maintenance of systemic oxygen delivery in septic patients, their morbidity and mortality remain high.

The assumption that tissue oxygenation can be preserved by maintaining its blood supply follows from physiological models that only apply to tissue with uniformly perfused capillaries. In sepsis, the microcirculation is profoundly disturbed, and the blood supply of individual organs may therefore no longer reflect their access to oxygen.

We review how capillary flow patterns affect oxygen extraction efficacy in tissue, and how the regulation of tissue blood flow must be adjusted to meet the metabolic needs of the tissue as capillary flows become disturbed as observed in critical illness. Using the brain, heart, and kidney as examples, we discuss whether disturbed capillary flow patterns might explain the apparent mismatch between organ blood flow and organ function in sepsis. Finally, we discuss diagnostic means of detecting capillary flow disturbance in animal models and in critically ill patients, and address therapeutic strategies that might improve tissue oxygenation by modifying capillary flow patterns.

Systemic and renal oxidative stress in the pathogenesis of hypertension: modulation of long-term control of arterial blood pressure by resveratrol

Hypertension affects over 25% of the global population and is associated with grave and often fatal complications that affect many organ systems. Although great advancements have been made in the clinical assessment and treatment of hypertension, the cause of hypertension in over 90% of these patients is unknown, which hampers the development of targeted and more effective treatment. The etiology of hypertension involves multiple pathological processes and organ systems, however one unifying feature of all of these contributing factors is oxidative stress. Once the body's natural anti-oxidant defense mechanisms are overwhelmed, reactive oxygen species (ROS) begin to accumulate in the tissues. ROS play important roles in normal regulation of many physiological processes, however in excess they are detrimental and cause widespread cell and tissue damage as well as derangements in many physiological processes. Thus, control of oxidative stress has become an attractive target for pharmacotherapy to prevent and manage hypertension. Resveratrol (trans-3,5,4'-Trihydroxystilbene) is a naturally occurring polyphenol which has anti-oxidant effects in vivo. Many studies have shown anti-hypertensive effects of resveratrol in different pre-clinical models of hypertension, via a multitude of mechanisms that include its function as an anti-oxidant. However, results have been mixed and in some cases resveratrol has no effect on blood pressure. This may be due to the heavy emphasis on peripheral vasodilator effects of resveratrol and virtually no investigation of its potential renal effects. This is particularly troubling in the arena of hypertension, where it is well known and accepted that the kidney plays an essential role in the long term regulation of arterial pressure and a vital role in the initiation, development and maintenance of chronic hypertension. It is thus the focus of this review to discuss the potential of resveratrol as an anti-hypertensive treatment via amelioration of oxidative stress within the framework of the fundamental physiological principles of long term regulation of arterial blood pressure.

Cardiorenal syndrome

Cardiorenal syndrome (CRS) includes a broad spectrum of diseases within which both the heart and kidneys are involved, acutely or chronically. An effective classification of CRS in 2008 essentially divides CRS in two main groups, cardiorenal and renocardiac CRS, based on primum movens of disease (cardiac or renal); both cardiorenal and renocardiac CRS are then divided into acute and chronic, according to onset of disease. The fifth type of CRS integrates all cardiorenal involvement induced by systemic disease. This article addresses the pathophysiology, diagnosis, treatment, and outcomes of the 5 distinct types of CRS.

Vasoplegia in septic shock: do we really fight the right enemy?

Vasoplegia is a key factor for the death of patients with septic shock in intensive care unit owing to persistent and irreversible hypotension. Impairment of vascular reactivity has been attributed to a combination of endothelial injury, arginine-vasopressin system dysfunction, release of other vasodilatory inflammatory mediators, and muscle hyperpolarizaton. Nitric oxide induced by a Ca(+2) independent isoform of nitric oxide synthase has been suggested to play an important role in sepsis-induced vasoplegia. However, inhibition of nitric oxide synthase only partially restores the endotoxin-induced vascular hyporeactivity. The aim of this review is to discuss in detail the recent suggested alternative mechanisms of vasoplegia and to briefly outline the current therapeutic strategies and the novel therapeutic options based on those mechanisms.

Rolipram improves renal perfusion and function during sepsis in the mouse

Microcirculatory dysfunction is correlated with increased mortality among septic patients and is believed to be a major contributor to the development of acute kidney injury (AKI). Rolipram, a selective phosphodiesterase 4 (PDE4) inhibitor, has been shown to reduce microvascular permeability and in the kidney, increase renal blood flow (RBF). This led us to investigate its potential to improve the renal microcirculation and preserve renal function during sepsis using a murine cecal ligation and puncture (CLP) model to induce sepsis. Rolipram, tested at doses of 0.3-10 mg/kg i.p., acutely restored capillary perfusion in a bell-shaped dose-response effect with 1 mg/kg being the lowest most efficacious dose. This dose also acutely increased RBF despite transiently decreasing mean arterial pressure. Rolipram also reduced renal microvascular permeability. It is noteworthy that delayed treatment with rolipram at 6 hours after CLP restored the renal microcirculation, reduced blood urea nitrogen and serum creatinine, and increased glomerular filtration rate at 18 hours. However, delayed treatment with rolipram did not reduce serum nitrate/nitrite levels, a marker of nitric oxide production, nor reactive nitrogen species generation in renal tubules. These data show that restoring the microcirculation with rolipram, even with delayed treatment, is enough to improve renal function during sepsis despite the generation of oxidants and suggest that PDE4 inhibitors should be evaluated further for their ability to treat septic-induced AKI.

Early neurovascular uncoupling in the brain during community acquired pneumonia

INTRODUCTION

Sepsis leads to microcirculatory dysfunction and therefore a disturbed neurovascular coupling in the brain. To investigate if the dysfunction is also present in less severe inflammatory diseases we studied the neurovascular coupling in patients suffering from community acquired pneumonia.

METHODS

Patients were investigated in the acute phase of pneumonia and after recovery. The neurovascular coupling was investigated with a simultaneous electroencephalogram (EEG)-Doppler technique applying a visual stimulation paradigm. Resting EEG frequencies, visual evoked potentials as well as resting and stimulated hemodynamic responses were obtained. Disease severity was characterized by laboratory and cognitive parameters as well as related scoring systems. Data were compared to a control group.

RESULTS

Whereas visually evoked potentials (VEP) remained stable a significant slowing and therefore uncoupling of the hemodynamic responses were found in the acute phase of pneumonia (Rate time: control group: 3.6 ± 2.5 vs. acute pneumonia: 1.6 ± 2.4 s; P < 0.0005). In the initial investigation, patients who deteriorated showed a decreased hemodynamic response as compared with those who recovered (gain: recovered: 15% ± 4% vs. deteriorated: 9% ± 3%, P < 0.05; control: 14% ± 5%). After recovery the coupling normalized.

CONCLUSIONS

Our study underlines the role of an early microcirculatory dysfunction in inflammatory syndromes that become evident in pre-septic conditions with a gradual decline according to disease severity.

Effects of anti-inflammatory vagus nerve stimulation on the cerebral microcirculation in endotoxinemic rats

BACKGROUND

In sepsis syndromes the severity of the inflammation triggers microvascular dysfunction and early organ failure. We studied the effects of anti-inflammatory vagus nerve stimulation on the cerebral microcirculatory integrity in an endotoxinemic rat model.

METHODS

In both control and endotoxinemic (5 mg/kg lipopolysaccharide i.v.) rats, the effect of cervical bilateral vagotomy with or without left-sided distal vagus nerve stimulation were compared to non-vagotomized, nonstimulated group (sham). Neurovascular coupling was analyzed by electrical forepaw stimulation, EEG, and cortical laser-Doppler flow recording. Resting cerebral blood flow, evoked potentials and hemodynamic responses, were obtained over a period of 4.5 hours. Regulation of the nitric oxide system (iNOS expression and nitrite/nitrate measurements), cytokines (IFN-γ, TNF-α, IL-6, IL-10), hypoxic and apoptosis signaling molecules (HIF-2α, Bax) were measured at the end of experiments.

RESULTS

In endotoxinemic rats, vagus nerve stimulation tended to increase anti-inflammatory cytokine levels and resulted in a stabile hemodynamic response (28 ± 13%; versus baseline). Vagotomized animals incurred a pro-inflammatory response (7 ± 4%; P < 0.0001 versus baseline) and produced more HIF-2α than vagotomized vagus nerve stimulated (VNS) animals. Evoked potential amplitudes were stabilized in VNS (15 ± 7 μV; n.s. versus baseline) as compared to vagotomised rats (8 ± 5 μV; P < 0.001 versus baseline). However, no effects were observed on apoptosis markers or nitric oxide levels.

CONCLUSIONS

Vagus nerve stimulation in endotoxinemic rats had a positive effect on neurovascular coupling and stabilized evoked potentials.

Activated protein C induces endoplasmic reticulum stress and attenuates lipopolysaccharide-induced apoptosis mediated by glycogen synthase kinase-3β

This study investigated the relationship between antiapoptotic activities induced by activated protein C and endoplasmic reticulum stress. In this study, it was observed that activated protein C elicited a rise in glucose-regulated protein 78 and glycogen synthase kinase-3β and inhibited apoptosis in human umbilical vein endothelial cells induced by lipopolysaccharide. Calcium inhibition did not alter the antiapoptotic effect of activated protein C. The antiapoptotic efficiency of activated protein C was reduced in human umbilical vein endothelial cells following treatment with glycogen synthase kinase-3β-siRNA. In summary, activated protein C induced endoplasmic reticulum stress and attenuated lipopolysaccharide-induced human umbilical vein endothelial cell apoptosis mediated by glycogen synthase kinase-3β.

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.

Pharmacological targets in the renal peritubular microenvironment: implications for therapy for sepsis-induced acute kidney injury

One of the most frequent and serious complications to develop in septic patients is acute kidney injury (AKI), a disorder characterized by a rapid failure of the kidneys to adequately filter the blood, regulate ion and water balance, and generate urine. AKI greatly worsens the already poor prognosis of sepsis and increases cost of care. To date, therapies have been mostly supportive; consequently there has been little change in the mortality rates over the last decade. This is due, at least in part, to the delay in establishing clinical evidence of an infection and the associated presence of the systemic inflammatory response syndrome and thus, a delay in initiating therapy. A second reason is a lack of understanding regarding the mechanisms leading to renal injury, which has hindered the development of more targeted therapies. In this review, we summarize recent studies, which have examined the development of renal injury during sepsis and propose how changes in the peritubular capillary microenvironment lead to and then perpetuate microcirculatory failure and tubular epithelial cell injury. We also discuss a number of potential therapeutic targets in the renal peritubular microenvironment, which may prevent or lessen injury and/or promote recovery.

Experimental Endotoxemia Induces Leukocyte Adherence and Plasma Extravasation Within the Rat Pial Microcirculation

Disturbance of capillary perfusions due to leukocyte adhesion, disseminated intravascular coagulation, tissue edema is critical components in the pathophysiology of sepsis. Alterations in brain microcirculation during sepsis are not clearly understood. The aim of this study is to gain an improved understanding of alterations through direct visualization of brain microcirculations in an experimental endotoxemia using intravital microscopy (IVM). Endotoxemia was induced in Lewis rats with Lipopolysaccharide (LPS, 15 mg/kg i.v.). The dura mater was removed via a cranial window to expose the pial vessels on the brain surface. Using fluorescence dyes, plasma extravasation of pial venous vessels and leukocyte-endothelial interaction were visualized by intravital microscopy 4 h after LPS administration. Plasma cytokine levels of IL1-β, IL-6, IFN-γ, TNF-α and KC/GRO were evaluated after IVM. A significant plasma extravasation of the pial venous vessels was found in endotoxemia rats compared to control animals. In addition, a significantly increased number of leukocytes adherent to the pial venous endothelium was observed in septic animals. Endotoxemia also induced a significant elevation of plasma cytokine levels of IL1-β, IL-6, IFN-γ, TNF-α and KC/GRO. Endotoxemia increased permeability in the brain pial vessels accompanied by an increase of leukocyte-endothelium interactions and an increase of inflammatory cytokines in the plasma.

Endothelial dysfunction assessed by brachial artery ultrasound in severe sepsis and septic shock

PURPOSE

Noninvasive evaluation of endothelial function may be accomplished by ultrasound assessment of flow-mediated vasodilation (FMD) of the brachial artery. This study aims to investigate the role of FMD analysis on intrahospital prognosis of patients with sepsis.

METHODS

Adult patients admitted to the intensive care unit with severe sepsis or septic shock were consecutively included. Brachial artery FMD was measured upon admission, after 24 and 72 hours. A group of apparently healthy subjects paired for sex and age was used as controls. Patients were followed up to discharge or death.

RESULTS

We studied 42 patients (mean age, 51 ± 19 years) with sepsis predominantly of abdominal or respiratory etiology (75%). Acute Physiology And Chronic Health Evaluation II risk score was 23 ± 7, and intrahospital mortality rate was 33%. Flow-mediated vasodilation in septic patients was significantly lower than in healthy controls (1.5 ± 7% vs 6 ± 4%, P < .001). Most of the nonsurvivors (86%) showed a decline in sequential FMD analyses, whereas only 43% of survivors showed a reduction of FMD (P = .01). In nonsurvivors, FMD was significantly lower 72 hours after sepsis onset (-3.3% ± 10% vs 5.2% ± 4%; P < .05; time-group interaction P value = .03).

CONCLUSIONS

Brachial FMD is altered in septic patients with hemodynamic instability, and its deterioration may be an early marker of unfavorable prognosis.

Primary outcomes for resuscitation science studies: a consensus statement from the American Heart Association

BACKGROUND AND PURPOSE

The guidelines presented in this consensus statement are intended to serve researchers, clinicians, reviewers, and regulators in the selection of the most appropriate primary outcome for a clinical trial of cardiac arrest therapies. The American Heart Association guidelines for the treatment of cardiac arrest depend on high-quality clinical trials, which depend on the selection of a meaningful primary outcome. Because this selection process has been the subject of much controversy, a consensus conference was convened with national and international experts, the National Institutes of Health, and the US Food and Drug Administration.

METHODS

The Research Working Group of the American Heart Association Emergency Cardiovascular Care Committee nominated subject leaders, conference attendees, and writing group members on the basis of their expertise in clinical trials and a diverse perspective of cardiovascular and neurological outcomes (see the online-only Data Supplement). Approval was obtained from the Emergency Cardiovascular Care Committee and the American Heart Association Manuscript Oversight Committee. Preconference position papers were circulated for review; the conference was held; and postconference consensus documents were circulated for review and comments were invited from experts, conference attendees, and writing group members. Discussions focused on (1) when after cardiac arrest the measurement time point should occur; (2) what cardiovascular, neurological, and other physiology should be assessed; and (3) the costs associated with various end points. The final document underwent extensive revision and peer review by the Emergency Cardiovascular Care Committee, the American Heart Association Science Advisory and Coordinating Committee, and oversight committees.

RESULTS

There was consensus that no single primary outcome is appropriate for all studies of cardiac arrest. The best outcome measure is the pairing of a time point and physiological condition that will best answer the question under study. Conference participants were asked to assign an outcome to each of 4 hypothetical cases; however, there was not complete agreement on an ideal outcome measure even after extensive discussion and debate. There was general consensus that it is appropriate for earlier studies to enroll fewer patients and to use earlier time points such as return of spontaneous circulation, simple "alive versus dead," hospital mortality, or a hemodynamic parameter. For larger studies, a longer time point after arrest should be considered because neurological assessments fluctuate for at least 90 days after arrest. For large trials designed to have a major impact on public health policy, longer-term end points such as 90 days coupled with neurocognitive and quality-of-life assessments should be considered, as should the additional costs of this approach. For studies that will require regulatory oversight, early discussions with regulatory agencies are strongly advised. For neurological assessment of post-cardiac arrest patients, researchers may wish to use the Cerebral Performance Categories or modified Rankin Scale for global outcomes.

CONCLUSIONS

Although there is no single recommended outcome measure for trials of cardiac arrest care, the simple Cerebral Performance Categories or modified Rankin Scale after 90 days provides a reasonable outcome parameter for many trials. The lack of an easy-to-administer neurological functional outcome measure that is well validated in post-cardiac arrest patients is a major limitation to the field and should be a high priority for future development.

Resveratrol improves renal microcirculation, protects the tubular epithelium, and prolongs survival in a mouse model of sepsis-induced acute kidney injury

The mortality rate of patients who develop acute kidney injury during sepsis nearly doubles. The effectiveness of therapy is hampered because it is usually initiated only after the onset of symptoms. As renal microvascular failure during sepsis is correlated with the generation of reactive nitrogen species, the therapeutic potential of resveratrol, a polyphenol vasodilator that is also capable of scavenging reactive nitrogen species, was investigated using the cecal ligation and puncture (CLP) murine model of sepsis-induced acute kidney injury. Resveratrol when given at 5.5 h following CLP reversed the decline in cortical capillary perfusion, assessed by intravital microscopy, at 6 h in a dose-dependent manner. Resveratrol produced the greatest improvement in capillary perfusion and increased renal blood flow and the glomerular filtration rate without raising systemic pressure. A single dose at 6 h after CLP was unable to improve renal microcirculation assessed at 18 h; however, a second dose at 12 h significantly improved microcirculation and decreased the levels of reactive nitrogen species in tubules, while improving renal function. Moreover, resveratrol given at 6, 12, and 18 h significantly improved survival. Hence, resveratrol may have a dual mechanism of action to restore the renal microcirculation and scavenge reactive nitrogen species, thus protecting the tubular epithelium even when administered after the onset of sepsis.

The microcirculatory response to compensated hypovolemia in a lower body negative pressure model

The objective of the present study was to test the hypothesis that controlled, adequately compensated, central hypovolemia in subjects with intact autoregulation would be associated with decreased peripheral microcirculatory diffusion and convection properties and, consequently, decreased tissue oxygen carrying capacity and tissue oxygenation. Furthermore, we evaluated the impact of hypovolemia-induced microcirculatory alterations on resting tissue oxygen consumption. To this end, 24 subjects were subjected to a progressive lower body negative pressure (LBNP) protocol of which 14 reached the end of the protocol. At baseline and at LBNP=-60 mm Hg, sidestream dark field (SDF) images of the sublingual microcirculation were acquired to measure microvascular density and perfusion; thenar and forearm tissue hemoglobin content (THI) and tissue oxygenation (StO2) were recorded using near-infrared spectroscopy (NIRS); and a vascular occlusion test (VOT) was performed to assess resting tissue oxygen consumption rate. SDF images were analyzed for total vessel density (TVD), perfused vessel density (PVD), the microvascular flow index (MFI), and flow heterogeneity (MFIhetero). We found that application of LBNP resulted in: 1) a significantly decreased microvascular density (PVD) and perfusion (MFI and MFIhetero); 2) a significantly decreased THI and StO2; and 3) an unaltered resting tissue oxygen consumption rate. In conclusion, using SDF imaging in combination with NIRS we showed that controlled, adequately compensated, central hypovolemia in subjects with intact autoregulation is associated with decreased microcirculatory diffusion (PVD) and convection (MFI and MFIhetero) properties and, consequently, decreased tissue oxygen carrying capacity (THI) and tissue oxygenation (StO2). Furthermore, using a VOT we found that resting tissue oxygen consumption was maintained under conditions of adequately compensated central hypovolemia.