Microvascular alterations in patients with acute severe heart failure and cardiogenic shock

Non-variceal upper gastrointestinal bleeding

Non-variceal upper gastrointestinal bleeding (NVUGIB) is bleeding that develops in the oesophagus, stomach or proximal duodenum. Peptic ulcers, caused by Helicobacter pylori infection or use of NSAIDs and low-dose aspirin (LDA), are the most common cause. Although the incidence and mortality associated with NVUGIB have been decreasing owing to considerable advances in the prevention and management of NVUGIB over the past 20 years, it remains a common clinical problem with an annual incidence of ∼67 per 100,000 individuals in the United States in 2012. NVUGIB is a medical emergency, and mortality is in the range ∼1-5%. After resuscitation and initial assessment, early (within 24 hours) diagnostic and therapeutic endoscopy together with intragastric pH control with proton pump inhibitors (PPIs) form the basis of treatment. With a growing ageing population treated with antiplatelet and/or anticoagulant medications, the clinical management of NVUGIB is complex as the risk between gastrointestinal bleeding events and adverse cardiovascular events needs to be balanced. The best clinical approach includes identification of risk factors and prevention of bleeding; available strategies include continuous treatment with PPIs or H. pylori eradication in those at increased risk of developing NVUGIB. Treatment with PPIs and/or use of cyclooxygenase-2-selective NSAIDs should be implemented in those patients at risk of NVUGIB who need NSAIDs and/or LDA.

Sublingual functional capillary rarefaction in chronic heart failure

BACKGROUND AND OBJECTIVE

Microcirculatory changes contribute to clinical symptoms and disease progression in chronic heart failure (CHF). A depression of coronary flow reserve is associated with a lower myocardial capillary density in biopsies. We hypothesized that changes in cardiac microcirculation might also be reflected by a systemic reduction in capillaries and visualized by sublingual videomicroscopy. The aim was to study in vivo capillary density and glycocalyx dimensions in patients with CHF vs healthy controls.

METHODS

Fifty patients with ischaemic and nonischaemic CHF and standard treatment were compared to 35 healthy age-matched subjects in a prospective cross-sectional study. Sublingual microcirculation was visualized using a sidestream darkfield videomicroscope. Functional and perfused total capillary densities were compared between patients and controls. A reduced glycocalyx thickness was measured by an increased perfused boundary region (PBR).

RESULTS

Median functional and total perfused capillary densities were 30% and 45% lower in patients with CHF (both P < .001). Intake of oral vitamin K antagonists was associated with significantly lower capillary densities (P < .05), but not independent of NT-proBNP. Dimensions of the glycocalyx were marginally lower in CHF patients than in healthy controls (<7% difference). However, PBR correlated significantly with inflammation markers (fibrinogen: r = .58; C-reactive protein: r = .42), platelet counts (r = .36) and inversely with measures of liver/renal function such as bilirubin (r = -.38) or estimated glomerular filtration rate (r = -.34) in CHF patients.

CONCLUSION

CHF patients have got a markedly lower functional and total perfused capillary density in sublingual microvasculature when compared to controls, indicating a systemic decrease in microcirculation.

Reduction of vascular leakage by imatinib is associated with preserved microcirculatory perfusion and reduced renal injury markers in a rat model of cardiopulmonary bypass

BACKGROUND

Cardiopulmonary bypass during cardiac surgery leads to impaired microcirculatory perfusion. We hypothesized that vascular leakage is an important contributor to microcirculatory dysfunction. Imatinib, a tyrosine kinase inhibitor, has been shown to reduce vascular leakage in septic mice. We investigated whether prevention of vascular leakage using imatinib preserves microcirculatory perfusion and reduces organ injury markers in a rat model of cardiopulmonary bypass.

METHODS

Male Wistar rats underwent cardiopulmonary bypass after treatment with imatinib or vehicle (n=8 per group). Cremaster muscle microcirculatory perfusion and quadriceps microvascular oxygen saturation were measured using intravital microscopy and reflectance spectroscopy. Evans Blue extravasation was determined in separate experiments. Organ injury markers were determined in plasma, intestine, kidney, and lungs.

RESULTS

The onset of cardiopulmonary bypass decreased the number of perfused microvessels by 40% in the control group [9.4 (8.6-10.6) to 5.7 (4.8-6.2) per microscope field; P<0.001 vs baseline], whereas this reduction was not seen in the imatinib group. In the control group, the number of perfused capillaries remained low throughout the experiment, whilst perfusion remained normal after imatinib administration. Microvascular oxygen saturation was less impaired after imatinib treatment compared with controls. Imatinib reduced vascular leakage and decreased fluid resuscitation compared with control [3 (3-6) vs 12 ml (7-16); P=0.024]. Plasma neutrophil-gelatinase-associated-lipocalin concentrations were reduced by imatinib.

CONCLUSIONS

Prevention of endothelial barrier dysfunction using imatinib preserved microcirculatory perfusion and oxygenation during and after cardiopulmonary bypass. Moreover, imatinib-induced protection of endothelial barrier integrity reduced fluid-resuscitation requirements and attenuated renal and pulmonary injury markers.

Detailing the cardiovascular profile in shock patients

Evaluation of the cardiovascular profile of critically ill patients is one of the most important actions performed in critically ill patients. It allows recognition that the patient is in shock and characterization of the type of circulatory failure. This step is crucial to initiate supportive interventions and to cure the cause responsible for the development of shock. Evaluation of tissue perfusion allows identification of the patient insufficiently resuscitated and also to trigger therapeutic interventions. Monitoring tissue perfusion can be achieved by lactate, venoarterial gradients in PCO₂, and central venous or mixed venous oxygen saturation. Ultimately, monitoring the microcirculation may help not only to identify alterations in tissue perfusion but also to identify the type of alterations: diffuse decrease in microvascular perfusion versus heterogeneity in the alterations, as in sepsis, with well perfused areas in close vicinity to poorly perfused areas. Regarding supportive therapy, a step-by-step approach is suggested, with fluid optimization followed by vasoactive support to preserve perfusion pressure and global and regional blood flows. The different variables should be integrated into decision and management pathways, and therapies adapted accordingly.

Hemorrhagic Shock and the Microvasculature

The microvasculature plays a central role in the pathophysiology of hemorrhagic shock and is also involved in arguably all therapeutic attempts to reverse or minimize the adverse consequences of shock. Microvascular studies specific to hemorrhagic shock were reviewed and broadly grouped depending on whether data were obtained on animal or human subjects. Dedicated sections were assigned to microcirculatory changes in specific organs, and major categories of pathophysiological alterations and mechanisms such as oxygen distribution, ischemia, inflammation, glycocalyx changes, vasomotion, endothelial dysfunction, and coagulopathy as well as biomarkers and some therapeutic strategies. Innovative experimental methods were also reviewed for quantitative microcirculatory assessment as it pertains to changes during hemorrhagic shock. The text and figures include representative quantitative microvascular data obtained in various organs and tissues such as skin, muscle, lung, liver, brain, heart, kidney, pancreas, intestines, and mesentery from various species including mice, rats, hamsters, sheep, swine, bats, and humans. Based on reviewed findings, a new integrative conceptual model is presented that includes about 100 systemic and local factors linked to microvessels in hemorrhagic shock. The combination of systemic measures with the understanding of these processes at the microvascular level is fundamental to further develop targeted and personalized interventions that will reduce tissue injury, organ dysfunction, and ultimately mortality due to hemorrhagic shock. Published 2018. Compr Physiol 8:61-101, 2018.

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.

Functional evaluation of sublingual microcirculation indicates successful weaning from VA-ECMO in cardiogenic shock

Background

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is increasingly adopted for the treatment of cardiogenic shock (CS). However, a marker of successful weaning remains largely unknown. Our hypothesis was that successful weaning is associated with sustained microcirculatory function during ECMO flow reduction. Therefore, we sought to test the usefulness of microcirculatory imaging in the same sublingual spot, using incident dark field (IDF) imaging in assessing successful weaning from VA-ECMO and compare IDF imaging with echocardiographic parameters.

Methods

Weaning was performed by decreasing the VA-ECMO flow to 50% (F₅₀) from the baseline. The endpoint of the study was successful VA-ECMO explantation within 48 hours after weaning. The response of sublingual microcirculation to a weaning attempt (WA) was evaluated. Microcirculation was measured in one sublingual area (single spot (ss)) using CytoCam IDF imaging during WA. Total vessel density (TVDss) and perfused vessel density (PVDss) of the sublingual area were evaluated before and during 50% flow reduction (TVDss_F50, PVDss_F50) after a WA and compared to conventional echocardiographic parameters as indicators of the success or failure of the WA.

Results

Patients (n = 13) aged 49 ± 18 years, who received VA-ECMO for the treatment of refractory CS due to pulmonary embolism (n = 5), post cardiotomy (n = 3), acute coronary syndrome (n = 2), myocarditis (n = 2) and drug intoxication (n = 1), were included. TVDss_F50 (21.9 vs 12.9 mm/mm², p = 0.001), PVDss_F50 (19.7 vs 12.4 mm/mm², p = 0.01) and aortic velocity–time integral (VTI) at 50% flow reduction (VTI_F50) were higher in patients successfully weaned vs not successfully weaned. The area under the curve (AUC) was 0.99 vs 0.93 vs 0.85 for TVDss_F50 (small vessels) >12.2 mm/mm², left ventricular ejection fraction (LVEF) >15% and aortic VTI >11 cm. Likewise, the AUC was 0.91 vs 0.93 vs 0.85 for the PVDss_F50 (all vessels) >14.8 mm/mm², LVEF >15% and aortic VTI >11 cm.

Conclusion

This study identified sublingual microcirculation as a novel potential marker for identifying successful weaning from VA-ECMO. Sustained values of TVDss_F50 and PVDss_F50 were found to be specific and sensitive indicators of successful weaning from VA-ECMO as compared to echocardiographic parameters.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1855-2) contains supplementary material, which is available to authorized users.

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

Background

Mildly elevated lactate levels (i.e., 1–2 mmol/L) are increasingly recognized as a prognostic finding in critically ill patients. One of several possible underlying mechanisms, microcirculatory dysfunction, can be assessed at the bedside using sublingual direct in vivo microscopy. We aimed to evaluate the association between relative hyperlactatemia, microcirculatory flow, and outcome.

Methods

This study was a predefined subanalysis of a multicenter international point prevalence study on microcirculatory flow abnormalities, the Microcirculatory Shock Occurrence in Acutely ill Patients (microSOAP). Microcirculatory flow abnormalities were assessed with sidestream dark-field imaging. Abnormal microcirculatory flow was defined as a microvascular flow index (MFI) < 2.6. MFI is a semiquantitative score ranging from 0 (no flow) to 3 (continuous flow). Associations between microcirculatory flow abnormalities, single-spot lactate measurements, and outcome were analyzed.

Results

In 338 of 501 patients, lactate levels were available. For this substudy, all 257 patients with lactate levels ≤ 2 mmol/L (median [IQR] 1.04 [0.80–1.40] mmol/L) were included. Crude ICU mortality increased with each lactate quartile. In a multivariable analysis, a lactate level > 1.5 mmol/L was independently associated with a MFI < 2.6 (OR 2.5, 95% CI 1.1–5.7, P = 0.027).

Conclusions

In a heterogeneous ICU population, a single-spot mildly elevated lactate level (even within the reference range) was independently associated with increased mortality and microvascular flow abnormalities. In vivo microscopy of the microcirculation may be helpful in discriminating between flow- and non-flow-related causes of mildly elevated lactate levels.

Trial registration

ClinicalTrials.gov, NCT01179243. Registered on August 3, 2010.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1842-7) contains supplementary material, which is available to authorized users.

Microvascular perfusion in cardiac arrest: a review of microcirculatory imaging studies

Cardiac arrest represents a leading cause of mortality and morbidity in developed countries. Extracorporeal cardiopulmonary resuscitation (ECPR) increases the chances for a beneficial outcome in victims of refractory cardiac arrest. However, ECPR and post-cardiac arrest care are affected by high mortality rates due to multi-organ failure syndrome, which is closely related to microcirculatory disorders. Therefore, microcirculation represents a key target for therapeutic interventions in post-cardiac arrest patients. However, the evaluation of tissue microcirculatory perfusion is still demanding to perform. Novel videomicroscopic technologies (Orthogonal polarization spectral, Sidestream dark field and Incident dark field imaging) might offer a promising way to perform bedside microcirculatory assessment and therapy monitoring. This review aims to summarise the recent body of knowledge on videomicroscopic imaging in a cardiac arrest setting and to discuss the impact of extracorporeal reperfusion and other therapeutic modalities on microcirculation.

Differences between healthy adults and patients with type 2 diabetes mellitus in reactivity of toe microcirculation by ultrasound combined with a warm bath test

The aim of this study was to explore the feasibility and clinical value of ultrasound combined with a warm bath test in assessing the differences in reactivity of toe microcirculation between healthy adults and patients with type 2 diabetes mellitus (T2DM).A total of 56 T2DM patients were recruited as case group, whereas 50 healthy volunteers were enrolled as control group.Fasting blood glucose, glycated hemoglobin, total cholesterol, triglyceride, low-density lipoprotein cholesterol in T2DM group were significantly higher than in control group. Under stationary condition, peak systolic velocity (PSV), end-diastolic velocity (EDV), and mean velocity (MV) were lower, but pulsatility index (PI) and resistance index (RI) were higher in patients with T2DM than in controls both in dorsalis pedis artery (DPA) and plantar digital artery (PDA). On response to the warm test, PSV, EDV, and MV increased and PI and RI decreased both in DPA and PDA in these 2 groups. Moreover, the change rate in PSV, EDV, MV, PI, and RI of PDA was significantly lower in T2DM group than in control group.Color Doppler combined with a warm bath test may be used as a new method in evaluating the differences in reactivity of distal limb microvascular between healthy adults and patients with T2DM.

Assessment of endothelial cell function and physiological microcirculatory reserve by video microscopy using a topical acetylcholine and nitroglycerin challenge

BACKGROUND

Assessment of the microcirculation is a promising target for the hemodynamic management of critically ill patients. However, just as the sole reliance on macrocirculatory parameters, single static parameters of the microcirculation may not represent a sufficient guide. Our hypothesis was that by serial topical application of acetylcholine (ACH) and nitroglycerin (NG), the sublingual microcirculation can be challenged to determine its endothelial cell-dependent and smooth muscle-dependent physiological reserve capacity.

METHODS

In 41 healthy subjects, sublingual capillary microscopy was performed before and after topical application of ACH and NG. Total vessel density (TVD) was assessed in parallel using manual computer-assisted image analysis as well as a fully automated analysis pathway utilizing a newly developed computer algorithm. Flow velocity was assessed using space-time diagrams of the venules as well as the algorithm-based calculation of an average perfused speed indicator (APSI).

RESULTS

No change in all measured parameters was detected after sublingual topical application of ACH. Sublingual topical application of NG however led to an increase in TVD, space-time diagram-derived venular flow velocity and APSI. No difference was detected in heart rate, blood pressure, and cardiac output as measured by echocardiography, as well as in plasma nitric oxide metabolite content before and after the topical application of ACH and NG.

CONCLUSIONS

In healthy subjects, the sublingual microcirculatory physiological reserve can be assessed non-invasively by topical application of nitroglycerin without affecting systemic circulation.

Lactate levels and hemodynamic coherence in acute circulatory failure

In this review, the relationship between changes in macrohemodynamics during the development and treatment of acute circulatory failure is discussed in the context of coherence with microcirculation and changes in lactate. In models of circulatory failure, coherence between changes in macrocirculatory and microcirculatory perfusion and coherence with subsequent changes in lactate levels are more or less preserved. However, in patients, particularly those with septic shock, these relationships are much less clear. As many factors influence the effect of circulatory failure and infection on microcirculation and on lactate levels, this should not be surprising. Resuscitation should therefore aim at adequate tissue perfusion where systemic hemodynamics, microcirculatory perfusion parameters, and lactate levels should be used in their relevant context. This results in treating the individual patient as an n = 1 experiment.

Hemodynamic coherence in sepsis

Microvascular alterations are a hallmark of sepsis and play a crucial role in its pathophysiology. Such alterations are the result of overwhelming inflammation, which negatively affects all the components of the microcirculation. As the severity of microvascular alterations is associated with organ dysfunction and mortality, several strategies have been tested for improving microcirculation. Nevertheless, they are mainly based on the conventional manipulation of systemic hemodynamics to increase the total flow to the organs and tissues. Other therapeutic interventions are still being investigated. In this review, we discuss the pathophysiology of septic microcirculatory dysfunction and its implications for possible treatments.

The response of the microcirculation to mechanical support of the heart in critical illness

Critical illness associated with cardiac pump failure results in reduced tissue perfusion in all organs and occurs in various conditions such as sepsis, cardiogenic shock, and heart failure. Mechanical circulatory support (MCS) devices can be used to maintain organ perfusion in patients with cardiogenic shock and decompensated chronic heart failure. However, correction of global hemodynamic parameters by MCS does not always cause a parallel improvement in microcirculatory perfusion and oxygenation of the organ systems, a condition referred to as a loss of hemodynamic coherence between macro- and microcirculation (MC). In this paper, we review the literature describing hemodynamic coherence or loss occurring during MCS of the heart. By using Embase, Medline Cochrane, Web of Science, and Google Scholar, we analyzed the literature on the response of MC and macrocirculation to MCS of the heart in critical illness. The characteristics of patients, MCS devices, and micro- and macrocirculatory parameters were very heterogenic. Short-term MCS studies (78%) described the effects of intra-aortic balloon pumps (IABPs) on the MC and macrocirculation. Improvement in MC, observed by handheld microscopy (orthogonal polarization spectral (OPS), sidestream dark-field (SDF), and Cytocam IDF imaging) in line with restored macrocirculation was found in 44% and 40% of the studies of short- and long-term MCS, respectively. In only 6 of 14 studies, hemodynamic coherence was described. It is concluded that more studies using direct visualization of the MC in short- and long-term MCS by handheld microscopy are needed, preferably randomized controlled studies, to identify the presence and clinical significance of hemodynamic coherence. It is anticipated that these further studies can enable to better identify patients who will benefit from treatment by mechanical heart support to ensure adequate organ perfusion.

Microcirculatory assessment of patients under VA-ECMO

Background

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is an effective technique for providing emergency mechanical circulatory support for patients with cardiogenic shock. VA-ECMO enables a rapid restoration of global systemic organ perfusion, but it has not been found to always show a parallel improvement in the microcirculation. We hypothesized in this study that the response of the microcirculation to the initiation of VA-ECMO might identify patients with increased chances of intensive care unit (ICU) survival.

Methods

Twenty-four patients were included in this study. Sublingual microcirculation measurements were performed using the CytoCam-IDF (incident dark field) imaging device. Microcirculatory measurements were performed at baseline, after VA-ECMO insertion (T1), 48–72 h after initiation of VA-ECMO (T2), 5–6 days after (T3), 9–10 days after (T4), and within 24 h of VA-ECMO removal.

Results

Of the 24 patients included in the study population, 15 survived and 9 died while on VA-ECMO. There was no significant difference between the systemic global hemodynamic variables at initiation of VA-ECMO between the survivors and non-survivors. There was, however, a significant difference in the microcirculatory parameters of both small and large vessels at all time points between the survivors and non-survivors. Perfused vessel density (PVD) at baseline (survivor versus non-survivor, 19.21 versus 13.78 mm/mm², p = 0.001) was able to predict ICU survival on initiation of VA-ECMO; the area under the receiver operating characteristic curve (ROC) was 0.908 (95 % confidence interval 0.772–1.0).

Conclusion

PVD of the sublingual microcirculation at initiation of VA-ECMO can be used to predict ICU mortality in patients with cardiogenic shock.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1519-7) contains supplementary material, which is available to authorized users.

Impact of microcirculatory video quality on the evaluation of sublingual microcirculation in critically ill patients

We aimed to assess the impact of image quality on microcirculatory evaluation with sidestream dark-field (SDF) videomicroscopy in critically ill patients and explore factors associated with low video quality. This was a retrospective analysis of a single-centre prospective observational study. Videos of the sublingual microcirculation were recorded using SDF videomicroscopy in 100 adult patients within 12 h from admittance to the intensive care unit and every 24 h until discharge/death. Parameters of vessel density and perfusion were calculated offline for small vessels. For all videos, a quality score (-12 = unacceptable, 1 = suboptimal, 2 = optimal) was assigned for brightness, focus, content, stability, pressure and duration. Videos with a total score ≤8 were deemed as unacceptable. A total of 2455 videos (853 triplets) was analysed. Quality was acceptable in 56 % of videos. Lower quality was associated with worse microvascular density and perfusion. Unreliable triplets (≥1 unacceptable or missing video, 65 % of total) showed lower vessel density, worse perfusion and higher flow heterogeneity as compared to reliable triplets (p < 0.001). Quality was higher among triplets collected by an extensively-experienced investigator or in patients receiving sedation or mechanical ventilation. Perfused vessel density was higher in patients with Glasgow Coma Scale (GCS) ≤8 (18.9 ± 4.5 vs. 17.0 ± 3.9 mm/mm² in those with GCS >8, p < 0.001) or requiring mechanical ventilation (18.0 ± 4.5 vs. 17.2 ± 3.8 mm/mm² in not mechanically ventilated patients, p = 0.059). We concluded that SDF video quality depends on both the operator's experience and patient's cooperation. Low-quality videos may produce spurious data, leading to an overestimation of microvascular alterations.

Cardiogenic Shock: Failure of Oxygen Delivery and Oxygen Utilization

Cardiogenic shock remains a highly lethal condition. Conventional therapy including revascularization and mechanical circulatory support aims to improve cardiac output and oxygen delivery, but increasing basic and clinical observations indicate wider circulatory and cellular abnormalities, particularly at the advanced stages of shock. Progressive cardiogenic shock is associated with microcirculatory and cellular abnormalities. Cardiogenic shock is initially characterized by a failure to maintain global oxygen delivery; however, progressive cardiogenic shock is associated with the release of pro-inflammatory cytokines, derangement of the regulation of regional blood flow, microcirculatory abnormalities, and cellular dysoxia. These abnormalities are analogous to septic shock and may not be reversed by increase in oxygen delivery, even to supranormal levels. Earlier mechanical circulatory support in cardiogenic shock may limit the development of microcirculatory and cellular abnormalities.

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

Background

The conjunctival microcirculation has potential as a window to cerebral perfusion due to related blood supply, close anatomical proximity and easy accessibility for microcirculatory imaging technique, such as sidestream dark field (SDF) imaging. Our study aims to evaluate conjunctival and sublingual microcirculation in brain dead patients and to compare it with healthy volunteers in two diametrically opposed conditions: full stop versus normal arterial blood supply to the brain.

Methods

In a prospective observational study we analyzed conjunctival and sublingual microcirculation using SDF imaging in brain dead patients after reaching systemic hemodynamic targets to optimize perfusion of donor organs, and in healthy volunteers. All brain death diagnoses were confirmed by cerebral angiography. Microcirculatory images were obtained and analyzed using standardized published recommendations. Study registered at ClinicalTrials.gov, number NCT02483273.

Results

Eleven brain dead patients and eleven apparently healthy controls were enrolled in the study. Microvascular flow index (MFI) of small vessels was significantly lower in brain dead patients in comparison to healthy controls in ocular conjunctiva (2.7 [2.4–2.9] vs. 3.0 [2.9–3.0], p = 0.01) and in sublingual mucosa (2.8 [2.6–2.9] vs. 3.0 [2.9–3.0], p = 0.02). Total vessel density (TVD) and perfused vessel density (PVD) of small vessels were significantly lower in brain dead patients in comparison to healthy controls in ocular conjunctiva (10.2 [6.6–14.8] vs. 18.0 [18.0–25.4] mm/mm², p = 0.001 and 5.0 [3.5–7.3] vs. 10.9 [10.9–13.5] 1/mm, p = 0.001), but not in sublingual mucosa.

Conclusion

In comparison to healthy controls brain dead patients had a significant reduction in conjunctival microvascular blood flow and density. However, the presence of conjunctival flow in case general cerebral flow is completely absent makes it impossible to use the conjunctival microcirculation as a substitute for brain flow, and further research should focus on the link between the ocular microcirculation, intracranial pressure and alternative ocular circulation.

Evaluation of the microcirculation in critically ill patients

Adequate monitoring of patients on intensive care units is of highest priority to provide optimal treatment and to detect patients at risk. Within recent years the microcirculation became more and more attention due to its central importance for the outcome of patients. Microcirculatory disorders may include capillary flow disturbances as well as changes in the density of perfused vessels. In the clinical setting, the most often used parameter to detect alterations in the microcirculation is serum lactate. Since this parameter is characterized by major limitations, other strategies including non-invasive methods to quantify microvascular perfusion have been developed. A successful surveillance of the microcirculation in the individual patient may guide diagnostic and treatment strategies in order to optimize organ perfusion and oxygenation, subsequently leading to an individualized therapy. Intravital microscopy has been used to stratify patients at risk and to predict patients' outcome. The aim of this review is to evaluate clinical correlates of microcirculatory disorders as well as giving an overview of newer diagnostic devices that may directly or indirectly evaluate the microcirculation and are available for use in critically ill patients.

Hemodynamic management of septic shock: is it time for "individualized goal-directed hemodynamic therapy" and for specifically targeting the microcirculation?

Septic shock is a life-threatening condition in both critically ill medical patients and surgical patients during the perioperative phase. In septic shock, specific alterations in global cardiovascular dynamics (i.e., the macrocirculation) and in the microcirculatory blood flow (i.e., the microcirculation) have been described. However, the presence and degree of microcirculatory failure are in part independent from systemic macrohemodynamic variables. Macrocirculatory and microcirculatory failure can independently induce organ dysfunction. We review current diagnostic and therapeutic approaches for the assessment and optimization of both the macrocirculation and the microcirculation in septic shock. There are various technologies for the determination of macrocirculatory hemodynamic variables. We discuss the data on early goal-directed therapy for the resuscitation of the macrocirculation. In addition, we describe the concept of "individualized goal-directed hemodynamic therapy." Technologies to assess the local microcirculation are also available. However, adequate resuscitation goals for the optimization of the microcirculation still need to be defined. At present, we are not ready to specifically monitor and target the microcirculation in clinical routine outside studies. In the future, concepts for an integrative approach for individualized hemodynamic management of the macrocirculation and in parallel the microcirculation might constitute a huge opportunity to define additional resuscitation end points in septic shock.

Effects of Shenfu injection on macrocirculation and microcirculation during cardiopulmonary resuscitation

AIM OF THE STUDY

To examine the effects of Shenfu injection (SFI) on macrocirculation and microcirculation during ventricular fibrillation (VF) and cardiopulmonary resuscitation (CPR).

MATERIALS AND METHODS

Sixteen female Landrace pigs were used in this study. After anesthesia, coronary perfusion pressure (CPP) was measured, and then the abdominal cavity was opened to observe the mesenteric microcirculation with the aid of sidestream dark field imaging. Following the guidelines, we determined microvascular flow index, perfused vessel density and proportion of perfused vessels both for large (diameter>20 μm) and small (diameter<20 μm) microvessels. SFI (1 ml/kg) or saline was given by vein injection at 1h before inducing VF. CPR was initiated after 4 min VF.

RESULTS

The shocks and duration of CPR were less in the SFI group compared with saline group. As the occurrence of VF, the CPP suddenly dropped to near zero, and cannot be measured in the both groups. However, there was greater CPP during CPR and at 1h after return of spontaneous circulation in the SFI group than saline group. Compared with saline, SFI significantly improved the microcirculation parameters of large and small microvessels during VF and CPR.

CONCLUSIONS

SFI can improve the microvascular blood flow and CPP during VF and CPR, and reduce the shocks and duration of CPR.

Serelaxin for the treatment of acute heart failure: a review with a focus on end-organ protection

Acute heart failure (AHF) is a complex clinical syndrome characterized by fluid overload and haemodynamic abnormalities (short-term clinical consequences) and the development of end-organ damage (long-term consequences). Current therapies for the treatment of AHF, such as loop diuretics and vasodilators, help to relieve haemodynamic imbalance and congestion, but have not been shown to prevent (and may even contribute to) end-organ damage, or to provide long-term clinical benefit. Serelaxin is the recombinant form of human relaxin-2, a naturally occurring hormone involved in mediating haemodynamic changes during pregnancy. Preclinical and clinical studies have investigated the effects mediated by serelaxin and the suitability of this agent for the treatment of patients with AHF. Data suggest that serelaxin acts via multiple pathways to improve haemodynamics at the vascular, cardiac, and renal level and provide effective congestion relief. In addition, this novel agent may protect the heart, kidneys, and liver from damage by inhibiting inflammation, oxidative stress, cell death, and tissue fibrosis, and stimulating angiogenesis. Serelaxin may therefore improve both short- and long-term outcomes in patients with AHF. In this review, we examine the unique mechanisms underlying the potential benefits of serelaxin for the treatment of AHF, in particular, those involved in mediating end-organ protection.

Clinical Features and outcomes in adults with cardiogenic shock supported by extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) is an increasingly used supportive measure for patients with refractory cardiogenic shock (CS). Despite its increasing use, there remain minimal data regarding which patients with refractory CS are most likely to benefit from ECMO. We retrospectively studied all patients (n = 123) who underwent initiation of ECMO for CS from February 2009 to September 2014 at a single center. Baseline patient characteristics, including demographics, co-morbid illness, cause of CS, available laboratory values, and patient outcomes were analyzed. Overall, 69 patients (56%) were weaned from ECMO, with 48 patients (39%) surviving to discharge. Survivors were younger (50 vs 60 years; p ≤0.0001), had a lower rate of previous smoking (27 vs 56%; p = 0.01) and chronic kidney disease (2% vs 13%; p = 0.03), and had lower lactate measured soon after ECMO initiation (3.1 vs 10.2 mmol/l; p = 0.01). Patients with pulmonary embolism (odds ratio 8.0, 95% confidence interval 2.00 to 31.99; p = 0.01) and acute cardiomyopathy (odds ratio 7.5, 95% confidence interval 1.69 to 33.27; p = 0.01) had a higher rate of survival than acute myocardial infarction, chronic cardiomyopathy, and miscellaneous etiologies compared to postcardiotomy CS as a referent. In conclusion, survival after ECMO initiation differs based on underlying cause of CS. Survival may be lower in older patients and those with early evidence of persistent hypoperfusion after initiation of ECMO for CS.

Microvascular reactivity and clinical outcomes in cardiac surgery

Introduction

Microvascular reactivity is decreased in patients with septic shock; this is associated with worse clinical outcomes. The objectives of the present study were to investigate microvascular reactivity in cardiac surgery patients and to assess any association with clinical outcomes.

Methods

We retrospectively analyzed a prospectively collected registry. In total, 254 consecutive adult patients undergoing cardiac and thoracic aortic surgeries from January 2013 through May 2014 were analyzed. We performed a vascular occlusion test (VOT) by using near-infrared spectroscopy to measure microvascular reactivity. VOT was performed three times per patient: prior to the induction of anesthesia, at the end of surgery, and on postoperative day 1. The primary endpoint was a composite of major adverse complications, including death, myocardial infarction, acute kidney injury, acute respiratory distress syndrome, and persistent cardiogenic shock.

Results

VOT recovery slope decreased during the surgery. VOT recovery slope on postoperative day 1 was significantly lower in patients with composite complications than those without (3.1 ± 1.6 versus 4.0 ± 1.5 %/s, P = 0.001), although conventional hemodynamic values, such as cardiac output and blood pressure, did not differ between the groups. On multivariable regression and linear analyses, low VOT recovery slope on postoperative day 1 was associated with increases of composite complications (odds ratio 0.742; 95 % confidence interval (CI) 0.584 to 0.943; P = 0.015) and hospital length of stay (regression coefficient (B) −1.276; 95 % CI −2.440 to −0.112; P = 0.032).

Conclusion

Microvascular reactivity largely recovered on postoperative day 1 in the patients without composite complications, but this restoration was attenuated in patients with composite complications.

Trial registration

ClinicalTrials.gov NCT01713192. Registered 22 October 2012.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-1025-3) contains supplementary material, which is available to authorized users.

Haemodialysis Impairs the Human Microcirculation Independent from Macrohemodynamic Parameters

Hemodynamic changes during haemodialysis are common. Often these changes are associated with symptoms that are thought to be the result of reduced microcirculatory blood flow and oxygen delivery. The microcirculatory effect of hemodialysis is scarcely researched, though of possible influence on patient outcome. New techniques have become available to visualise and analyse microvascular blood flow. We performed an observational study using Sidestream Dark Field imaging, a microscopic technique using polarised light to visualise erythrocytes passing through sublingual capillaries, to analyse the effect of haemodyalisis on central microvascular blood flow. We showed that there is a substantial impairment of microvascular blood flow and a discrepancy between micro- and macro-vascular parameters.

Effects of hypertonic saline and mannitol on cortical cerebral microcirculation in a rabbit craniotomy model

Background

Hyperosmolar solutions have been used in neurosurgery to modify brain bulk and prevent neurological deterioration. The aim of this animal study was to compare the short-term effects of equivolemic, equiosmolar solutions of mannitol and hypertonic saline (HTS) on cerebral cortical microcirculation in a rabbit craniotomy model.

Methods

Rabbits (weight, 2.0–3.0 kg) were anesthetized, ventilated mechanically, and subjected to a craniotomy. The animals were allocated randomly to receive a 3.75 ml/kg intravenous infusion of either 3.2 % HTS (group HTS, n = 8) or 20 % mannitol (group MTL, n = 8). Microcirculation in the cerebral cortex was evaluated using sidestream dark-field (SDF) imaging before and 20 min after the end of the 15-min HTS infusion. Global hemodynamic data were recorded, and blood samples for laboratory analysis were obtained at the time of SDF image recording.

Results

No differences in the microcirculatory parameters were observed between the groups before the use of osmotherapy. After osmotherapy, lower proportions of perfused small vessel density (P = 0.0474), perfused vessel density (P = 0.0457), and microvascular flow index (P = 0.0207) were observed in the MTL group compared with those in the HTS group.

Conclusions

Our findings suggest that an equivolemic, equiosmolar HTS solution better preserves perfusion of cortical brain microcirculation compared to MTL in a rabbit craniotomy model.

Microvascular obstruction and endothelial activation are independently associated with the clinical manifestations of severe falciparum malaria in adults: an observational study

BACKGROUND

Microvascular obstruction and endothelial dysfunction have both been linked to tissue hypoperfusion in falciparum malaria, but their relative contributions to the disease's pathogenesis and outcome are unknown.

METHODS

Microvascular blood flow was quantified in adults with severe falciparum malaria on their admission to hospital; plasma biomarkers of endothelial function were measured simultaneously. The relationship between these indices and the patients' clinical findings and in-hospital course was examined.

RESULTS

Microvascular obstruction was observed in 119/142 (84 %) patients; a median (interquartile range (IQR)) of 14.9 % (6.6-34.9 %) of capillaries were obstructed in patients that died versus 8.3 % (1.7-26.6 %) in survivors (P = 0.039). The proportion of obstructed capillaries correlated with the estimated parasite biomass (rs = 0.25, P = 0.004) and with plasma lactate (rs = 0.38, P <0.0001), the strongest predictor of death in the series. Plasma angiopoietin-2 (Ang-2) concentrations were markedly elevated suggesting widespread endothelial activation; the median (IQR) Ang-2 concentration was 21.9 ng/mL (13.4-29.4 ng/mL) in patients that died versus 14.9 ng/mL (9.8-29.3 ng/mL) in survivors (P = 0.035). Ang-2 concentrations correlated with estimated parasite biomass (rs = 0.35, P <0.001) and plasma lactate (rs = 0.37, P <0.0001). Microvascular obstruction and Ang-2 concentrations were not significantly correlated with each other (rs = 0.17, P = 0.06), but were independently associated with plasma lactate (P <0.001 and P = 0.002, respectively).

CONCLUSIONS

Microvascular obstruction and systemic endothelial activation are independently associated with plasma lactate, the strongest predictor of death in adults with falciparum malaria. This supports the hypothesis that the two processes make an independent contribution to the pathogenesis and clinical manifestations of the disease.

Are there new approaches for diagnosis, therapy guidance and outcome prediction of sepsis?

Beside many efforts to improve outcome, sepsis is still one of the most frequent causes of death in critically ill patients. It is the most common condition with high mortality in intensive care units. The complexity of the septic syndrome comprises immunological aspects - i.e., sepsis induced immunosuppression - but is not restricted to this fact in modern concepts. So far, exact mechanisms and variables determining outcome and mortality stay unclear. Since there is no typical risk profile, early diagnosis and risk stratification remain difficult, which hinders rapid and effective treatment initiation. Due to the heterogeneous nature of sepsis, potential therapy options should be adapted to the individual. Biomarkers like C-reactive protein and procalcitonin are routinely used as complementary tools in clinical decision-making. Beyond the acute phase proteins, a wide bunch of promising substances and non-laboratory tools with potential diagnostic and prognostic value is under intensive investigation. So far, clinical decision just based on biomarker assessment is not yet feasible. However, biomarkers should be considered as a complementary approach.

International study on microcirculatory shock occurrence in acutely ill patients

OBJECTIVES

Microcirculatory alterations are associated with adverse outcome in subsets of critically ill patients. The prevalence and significance of microcirculatory alterations in the general ICU population are unknown. We studied the prevalence of microcirculatory alterations in a heterogeneous ICU population and its predictive value in an integrative model of macro- and microcirculatory variables.

DESIGN

Multicenter observational point prevalence study.

SETTING

The Microcirculatory Shock Occurrence in Acutely ill Patients study was conducted in 36 ICUs worldwide.

PATIENTS

A heterogeneous ICU population consisting of 501 patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographic, hemodynamic, and laboratory data were collected in all ICU patients who were 18 years old or older. Sublingual Sidestream Dark Field imaging was performed to determine the prevalence of an abnormal capillary microvascular flow index (< 2.6) and its additional value in predicting hospital mortality. In 501 patients with a median Acute Physiology and Chronic Health Evaluation II score of 15 (10-21), a Sequential Organ Failure Assessment score of 5 (2-8), and a hospital mortality of 28.4%, 17% exhibited an abnormal capillary microvascular flow index. Tachycardia (heart rate > 90 beats/min) (odds ratio, 2.71; 95% CI, 1.67-4.39; p < 0.001), mean arterial pressure (odds ratio, 0.979; 95% CI, 0.963-0.996; p = 0.013), vasopressor use (odds ratio, 1.84; 95% CI, 1.11-3.07; p = 0.019), and lactate level more than 1.5 mEq/L (odds ratio, 2.15; 95% CI, 1.28-3.62; p = 0.004) were independent risk factors for hospital mortality, but not abnormal microvascular flow index. In reference to microvascular flow index, a significant interaction was observed with tachycardia. In patients with tachycardia, the presence of an abnormal microvascular flow index was an independent, additive predictor for in-hospital mortality (odds ratio, 3.24; 95% CI, 1.30-8.06; p = 0.011). This was not true for nontachycardic patients nor for the total group of patients.

CONCLUSIONS

In a heterogeneous ICU population, an abnormal microvascular flow index was present in 17% of patients. This was not associated with mortality. However, in patients with tachycardia, an abnormal microvascular flow index was independently associated with an increased risk of hospital death.

Assessment of microcirculatory perfusion in healthy anesthetized cats undergoing ovariohysterectomy using sidestream dark field microscopy

OBJECTIVE

To: (1) determine the feasibility of using sidestream dark field microscopy (SDM) to measure microcirculatory parameters in healthy, anesthetized cats and (2) determine if surgical tissue manipulation and anesthesia time alter these parameters during ovariohysterectomy.

DESIGN

Prospective observational study.

SETTING

University teaching hospital.

ANIMALS

Eighteen healthy female cats.

INTERVENTIONS

Sublingual mucosa microcirculatory videos were obtained under general anesthesia preoperatively, intraoperatively, and postoperatively using an SDM device in healthy cats presenting for ovariohysterectomy. At each video acquisition point, macrovascular parameters (heart rate, blood pressure, pulse oximetry, end-tidal CO2) were recorded. Vascular analysis software was used to calculate standard microcirculatory parameters. Multivariate analysis was performed to compare microvascular and macrovascular parameters, as well as correlation with the effect of surgical manipulation and time under anesthesia.

MEASUREMENTS AND MAIN RESULTS

Twelve of 18 cats were included in final video analysis; 6 were removed for poor video quality. Values for total vessel density (TVD, 47.7 ± 8.39 mm/mm(2)), proportion of perfused vessels (PPV, 88.2 ± 5.95%), perfused vessel density (PVD, 43.0 ± 9.00 mm/mm(2)), microcirculatory flow index (MFI, 2.33 ± 0.33) were determined preoperatively. There were no significant changes in TVD, PPV, and PVD across intervention points. The MFI increased significantly from preoperative to intra- and postoperative data collection points. No correlation between microcirculatory parameters and length of anesthesia or macrocirculatory values was found.

CONCLUSIONS AND CLINICAL RELEVANCE

This study demonstrated that SDM can be utilized to obtain sublingual microvascular parameters in healthy, anesthetized cats. Limitations include difficulty in obtaining high quality images, presumed need for general anesthesia, and need for off-line video analysis. This technology has potential as a tool in experimental and clinical monitoring of microcirculatory changes in felines.

Anemia and Transfusion in Critical Care

Objective:

The objective of this report is to review the physiology and management of anemia in critical care. Selected publications on physiology and transfusion related to anemia and critical care, including the modern randomized trials of conservative versus liberal transfusion policy, were used. Anemia is compensated and tolerated in most critically ill patients as long as oxygen delivery is at least twice oxygen consumption. There are risks to blood transfusion which can be minimized by blood banking practice. The availability of cultured red cells may allow correction of anemia without significant risk. The benefit of transfusion in anemia must be weighted against the risk in any specific patient.

Conclusion and Recommendation:

In a criticially ill patient, anemia should be managed to avoid oxygen supply dependency (oxygen delivery less than twice comsumption) and to maintain moderate oxygen delivery reserve (DO2/VO2 > 3).

Prolonged observation time reveals temporal fluctuations in the sublingual microcirculation in pigs given arginine vasopressin

Intravital videomicroscopy of sublingual microcirculation is used to monitor critically ill patients. Existing guidelines suggest averaging handheld video recordings of ∼20 s in duration from five areas. We assessed whether an extended observation time may provide additional information on the microcirculation. Pigs (n = 8) under general anesthesia were divided between two groups, one with manually held camera, in which microcirculation was assessed continuously for 1 min in five areas, and one with a fixed camera, in which the observation time was extended to 10 min in a single area. The microcirculation was challenged by infusing arginine vasopressin (AVP). In the fixed group, ischemic acute heart failure was induced by left coronary microembolization, and the AVP infusion was repeated. All recordings were divided into 20-s sequences, and the small-vessel microvascular flow index (MFI) was scored and averaged for each measurement point. When administering 0.003, 0.006, and 0.012 IU·kg(-1)·min(-1) of AVP, we observed that the small-vessel MFI in the fixed 10-min group was significantly reduced (2.03 ± 0.38, 0.98 ± 0.18, and 0.48 ± 0.11) compared with both the initial 20 s (2.77 ± 0.04, 2.06 ± 0.04, and 1.74 ± 0.06; P < 0.05) and the 1-min total (2.63 ± 0.09, 1.70 ± 0.07, and 1.33 ± 0.16; P < 0.05) in the handheld group. In acute heart failure, the cardiac output decreased to half of the preischemic values. Interestingly, the small-vessel MFI was more affected by the administration of 0.001 and 0.003 IU·kg(-1)·min(-1) of AVP in acute heart failure (1.62 ± 0.60 and 1.16 ± 0.38) compared with preischemic values (2.86 ± 0.09 and 2.03 ± 0.38; P < 0.05). In conclusion, a prolonged recording time reveals temporal heterogeneity that may impact the assessment of microcirculatory function.

Cytocam-IDF (incident dark field illumination) imaging for bedside monitoring of the microcirculation

Background

Orthogonal polarized spectral (OPS) and sidestream dark field (SDF) imaging video microscope devices were introduced for observation of the microcirculation but, due to technical limitations, have remained as research tools. Recently, a novel handheld microscope based on incident dark field illumination (IDF) has been introduced for clinical use. The Cytocam-IDF imaging device consists of a pen-like probe incorporating IDF illumination with a set of high-resolution lenses projecting images on to a computer controlled image sensor synchronized with very short pulsed illumination light. This study was performed to validate Cytocam-IDF imaging by comparison to SDF imaging in volunteers.

Methods

This study is a prospective, observational study. The subjects consist of 25 volunteers.

Results

Sublingual microcirculation was evaluated using both techniques. The main result was that Cytocam-IDF imaging provided better quality images and was able to detect 30% more capillaries than SDF imaging (total vessels density Cytocam-IDF: 21.60 ± 4.30 mm/mm² vs SDF: 16.35 ± 2.78 mm/mm², p < 0.0001). Comparison of the images showed increased contrast, sharpness, and image quality of both venules and capillaries.

Conclusions

Cytocam-IDF imaging detected more capillaries and provided better image quality than SDF imaging. It is concluded that Cytocam-IDF imaging may provide a new improved imaging modality for clinical assessment of microcirculatory alterations.

Electronic supplementary material

The online version of this article (doi:10.1186/s40635-015-0040-7) contains supplementary material, which is available to authorized users.

Sublingual microcirculation in pulmonary arterial hypertension

RATIONALE

Pulmonary arterial hypertension (PAH) is a pulmonary vasculopathy that leads to failure of the right ventricle and premature death.

OBJECTIVES

To determine whether the sublingual microcirculation is affected in patients with PAH compared with healthy age- and sex-matched control subjects.

METHODS

Using the CapiScope Handheld Video Capillaroscope we measured the sublingual microvasculature density, flow index, tortuosity, and curvature. Videos were acquired immediately after right heart catheterization, and determinations were made off-line by investigators blinded to the group assignment or hemodynamics.

MEASUREMENTS AND MAIN RESULTS

In this cross-sectional pilot study, we included 26 patients with PAH (age, mean ± SD, 56.7 ± 10 yr; 77% women) and 14 healthy control subjects (age, 53.1 ± 12 yr; 71% women). Sublingual microvasculature flow index was lower (2 ± 0.66 vs. 2.7 ± 0.37, P < 0.001) with higher heterogeneity index (0.63 ± 0.63 vs. 0.25 ± 0.25, P = 0.04) in patients with PAH than control subjects. Microvasculature density was similar between the groups, but tortuosity was more pronounced in patients than control subjects (tort 0: 45 ± 19 vs. 23.6 ± 12, P = 0.001 and tort 1: 0.2 ± 0.16 vs. 0.06 ± 0.04, P < 0.001).

CONCLUSIONS

Patients with PAH showed lower sublingual microvasculature flow index and higher tortuosity compared with healthy age- and sex-matched control subjects. Further investigations are needed to assess whether this methodology can provide information on disease prognosis and/or response to therapy in this condition.

Incidence and impact of skin mottling over the knee and its duration on outcome in critically ill patients

PURPOSE

Skin mottling is frequent and can be associated with an increased mortality rate in ICU patients with septic shock. Its overall incidence in ICU and its impact on outcome is unknown. We aimed to assess the incidence of skin mottling over the knee among all critically ill patients admitted in ICU and its role on their outcome.

METHODS

An observational study over a 1-year period in a 15-bed medical ICU of a teaching hospital. Skin mottling over the knee was prospectively and qualitatively assessed by trained nurses.

RESULTS

Incidence of skin mottling was 29% (230 of 791 patients) in overall, and 49% (32 of 65 patients) in the subset of patients admitted for septic shock. Skin mottling was present on the day on admission in 65% of patients and persisted more than 6 h in 59% of cases. In-ICU mortality was 8% in patients without mottling, 30% in patients with short skin mottling and 40% in patients with persistent skin mottling (p < 0.01 between all groups). In the overall population, skin mottling over the knee was associated with in-ICU mortality independently from SAPS II (aOR 3.29 [95% CI, 2.08-5.19], p < 0.0001). Among patients with skin mottling over the knee, persistence of skin mottling remained associated with increased in-ICU mortality independently of organ dysfunctions at the mottling onset (OR 2.77 [95% CI, 1.34-5.72], p = 0.004).

CONCLUSIONS

Skin mottling is frequent in the general population of patients admitted in ICU. Occurrence and persistence of skin mottling are independently associated with in-ICU mortality.

Consensus on circulatory shock and hemodynamic monitoring. Task force of the European Society of Intensive Care Medicine

OBJECTIVE

Circulatory shock is a life-threatening syndrome resulting in multiorgan failure and a high mortality rate. The aim of this consensus is to provide support to the bedside clinician regarding the diagnosis, management and monitoring of shock.

METHODS

The European Society of Intensive Care Medicine invited 12 experts to form a Task Force to update a previous consensus (Antonelli et al.: Intensive Care Med 33:575-590, 2007). The same five questions addressed in the earlier consensus were used as the outline for the literature search and review, with the aim of the Task Force to produce statements based on the available literature and evidence. These questions were: (1) What are the epidemiologic and pathophysiologic features of shock in the intensive care unit? (2) Should we monitor preload and fluid responsiveness in shock? (3) How and when should we monitor stroke volume or cardiac output in shock? (4) What markers of the regional and microcirculation can be monitored, and how can cellular function be assessed in shock? (5) What is the evidence for using hemodynamic monitoring to direct therapy in shock? Four types of statements were used: definition, recommendation, best practice and statement of fact.

RESULTS

Forty-four statements were made. The main new statements include: (1) statements on individualizing blood pressure targets; (2) statements on the assessment and prediction of fluid responsiveness; (3) statements on the use of echocardiography and hemodynamic monitoring.

CONCLUSIONS

This consensus provides 44 statements that can be used at the bedside to diagnose, treat and monitor patients with shock.

Normobaric hyperoxia alters the microcirculation in healthy volunteers

The use of high concentrations of inhaled oxygen has been associated with adverse effects but recent data suggest a potential therapeutic role of normobaric hyperoxia (NH) in sepsis and cerebral ischemia. Hyperoxia may induce vasoconstriction and alter endothelial function, so we evaluated its effects on the microcirculation in 40 healthy adult volunteers using side-stream dark field (SDF) video-microscopy on the sublingual area and near-infrared spectroscopy (NIRS) on the thenar eminence. In a first group of volunteers (n=18), measurements were taken every 30 min: at baseline in air, during NH (close to 100% oxygen via a non-rebreathing mask) and during recovery in air. In a second group (n=22), NIRS measurements were taken in NH or ambient air on two separate days to prevent any potential influence of repeated NIRS measurements. NH significantly decreased the proportion of perfused vessels (PPV) from 92% to 66%, perfused vessel density (PVD) from 11.0 to 7.3 vessels/mm, perfused small vessel density (PSVD) from 9.0 to 5.8 vessels/mm and microvascular flow index (MFI) from 2.8 to 2.0, and increased PPV heterogeneity from 7.5% to 30.4%. Thirty minutes after return to air, PPV, PVD, PSVD and MFI remained partially altered. During NH, NIRS descending slope and NIRS muscle oxygen consumption (VO2) decreased from 8.5 to 7.9%/s and 127 to 103 units, respectively, in the first group and from 10.7 to 9.4%/s and 150 to 115 units in the second group. NH, therefore, alters the microcirculation in healthy subjects, decreasing capillary perfusion and VO2 and increasing the heterogeneity of the perfusion.

Microcirculatory effects of intravenous fluid administration in anesthetized dogs undergoing elective ovariohysterectomy

OBJECTIVE

To assess the microcirculatory effects of IV fluid administration in healthy anesthetized dogs undergoing elective ovariohysterectomy.

ANIMALS

49 client-owned dogs.

PROCEDURES

Dogs were sedated, and anesthesia was induced with propofol and diazepam and maintained with isoflurane in oxygen. Dogs received lactated Ringer's solution (LRS) IV at rates of 0, 10, or 20 mL/kg/h. Videomicroscopy was used to assess and record effects of LRS administration on microcirculation in the buccal mucosa. Measurements of microcirculatory (total vessel density, proportion of perfused vessels, microcirculatory flow index, and perfused vessel density by vessel size [< 20 μm, ≥ 20 μm, and all diameters]) and other physiologic variables (heart rate, Doppler-measured blood pressure, oxygen saturation as measured by pulse oximetry, capillary refill time, and body temperature) were compared among groups at baseline (immediately after anesthetic induction), 30 and 60 minutes afterward, and overall.

RESULTS

Neither the proportion of perfused vessels nor microcirculatory flow index varied among treatment groups at any time point, regardless of vessel size. For vessels < 20 μm in diameter and for all vessels combined, total and perfused vessel density were similar among groups. For vessels ≥ 20 μm in diameter, total vessel density was significantly greater in the 20 mL/kg/h group than in other groups, and perfused vessel density was significantly greater in the 20 mL/kg/h group than in the 0 mL/kg/h group, when all time points were considered. Other physiologic variables were similar among groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Total and perfused vessel density of vessels ≥ 20 μm in diameter (mostly venules) were greatest in dogs that received 20 mL of LRS/kg/h. Further research is required to evaluate clinical importance of these findings.