The endothelial glycocalyx comprises a complex layer of membrane-bound proteoglycans, secreted glycosaminoglycans, glycoproteins, glycolipids and bound plasma proteins such as albumin and antithrombin associated with the endothelial surface The glycocalyx plays an important role in vascular homeostasis, regulating vascular permeability and cell adhesion, and acts as a mechanosensor for hemodynamic shear stresses; it also has antithrombotic and anti-inflammatory functions Plasma proteins such as albumin are physiologically bound within the glycocalyx, thus contributing to stability of the layer Albumin is the major determinant of plasma colloid osmotic pressure In addition, albumin transports sphingosine-1-phosphate which has protective endothelial effects, acts as a free radical scavenger, and has immunomodulatory and anti-inflammatory effects This review examines the physiological function of the endothelial glycocalyx and the role of human albumin in preserving glycocalyx integrity and the microcirculation

/pdf/role-of-albumin-in-the-preservation-of-endothelial-2g01ofb1kt.pdf

Role of albumin in the preservation of endothelial glycocalyx integrity and the microcirculation: a review

Bedside functional hemodynamic assessment has gained in popularity in the last years to overcome the limitations of static or dynamic indexes in predicting fluid responsiveness. The aim of this systematic review and metanalysis of studies is to investigate the reliability of the functional hemodynamic tests (FHTs) used to assess fluid responsiveness in adult patients in the intensive care unit (ICU) and operating room (OR). MEDLINE, EMBASE, and Cochrane databases were screened for relevant articles using a FHT, with the exception of the passive leg raising. The QUADAS-2 scale was used to assess the risk of bias of the included studies. In-between study heterogeneity was assessed through the I2 indicator. Bias assessment graphs were plotted, and Egger’s regression analysis was used to evaluate the publication bias. The metanalysis determined the pooled area under the receiving operating characteristic (ROC) curve, sensitivity, specificity, and threshold for two FHTs: the end-expiratory occlusion test (EEOT) and the mini-fluid challenge (FC). After text selection, 21 studies met the inclusion criteria, 7 performed in the OR, and 14 in the ICU between 2005 and 2018. The search included 805 patients and 870 FCs with a median (IQR) of 39 (25–50) patients and 41 (30–52) FCs per study. The median fluid responsiveness was 54% (45–59). Ten studies (47.6%) adopted a gray zone analysis of the ROC curve, and a median (IQR) of 20% (15–51) of the enrolled patients was included in the gray zone. The pooled area under the ROC curve for the end-expiratory occlusion test (EEOT) was 0.96 (95%CI 0.92–1.00). The pooled sensitivity and specificity were 0.86 (95%CI 0.74–0.94) and 0.91 (95%CI 0.85–0.95), respectively, with a best threshold of 5% (4.0–8.0%). The pooled area under the ROC curve for the mini-FC was 0.91 (95%CI 0.85–0.97). The pooled sensitivity and specificity were 0.82 (95%CI 0.76–0.88) and 0.83 (95%CI 0.77–0.89), respectively, with a best threshold of 5% (3.0–7.0%). The EEOT and the mini-FC reliably predict fluid responsiveness in the ICU and OR. Other FHTs have been tested insofar in heterogeneous clinical settings and, despite promising results, warrant further investigations.

/pdf/functional-hemodynamic-tests-a-systematic-review-and-a-44r3mokj83.pdf

Functional hemodynamic tests: a systematic review and a metanalysis on the reliability of the end-expiratory occlusion test and of the mini-fluid challenge in predicting fluid responsiveness

Purpose of reviewIn the field of prediction of fluid responsiveness, the most recent studies have focused on validating new tests, on clarifying the limitations of older ones, and better defining their modalities.Recent findingsThe limitations of pulse pressure/stroke volume variations are numerous,

Assessment of fluid responsiveness: recent advances.

Fluid administration is the first-line therapy in patients with acute circulatory failure. The main goal of fluid administration is to increase the cardiac output and ultimately the oxygen delivery. Nevertheless, the decision to administer fluids or not should be carefully considered, since half of critically ill patients are fluid unresponsive, and the deleterious effects of fluid overload clearly documented. Thus, except at the initial phase of hypovolemic or septic shock, where hypovolemia is constant and most of the patients responsive to the initial fluid resuscitation, it is of importance to test fluid responsiveness before administering fluids in critically ill patients. The static markers of cardiac preload cannot reliably predict fluid responsiveness, although they have been used for decades. To address this issue, some dynamic tests have been developed over the past years. All these tests consist in measuring the changes in cardiac output in response to the transient changes in cardiac preload that they induced. Most of these tests are based on the heart-lung interactions. The pulse pressure or stroke volume respiratory variations were first described, following by the respiratory variations of the vena cava diameter or of the internal jugular vein diameter. Nevertheless, all these tests are reliable only under strict conditions limiting their use in many clinical situations. Other tests such as passive leg raising or end-expiratory occlusion act as an internal volume challenge. To reliably predict fluid responsiveness, physicians must choose among these different dynamic tests, depending on their respective limitations and on the cardiac output monitoring technique which is used. In this review, we will summarize the most recent findings regarding the prediction of fluid responsiveness in ventilated patients.

/pdf/prediction-of-fluid-responsiveness-in-ventilated-patients-4qsy4ls32t.pdf

Prediction of fluid responsiveness in ventilated patients.

Cardiogenic shock is the clinical expression of circulatory failure, as a consequence of left, right or biventricular dysfunction. Cardiogenic shock is also defined as a state of critical end-organ hypoperfusion due to primary cardiac dysfunction [1–3]. Cardiogenic shock is not simply a decrease in cardiac contractile function, but also a multiorgan dysfunction syndrome involving the entire circulatory system, often complicated by a systemic inflammatory response syndrome with severe cellular and metabolic abnormalities [4]. The clinical presentation of cardiogenic shock varies from hemodynamic abnormalities of pre-shock to mild shock, progressing to more profound shock and finally refractory shock, which invariably is associated with high mortality rates. Additional insults can occur, such as arrhythmias, vasodilation, ischemia and infection, acutely changing the trajectory of the disease [5]. The contemporary management of cardiogenic shock involves early diagnosis and directed therapy to optimize oxygen delivery and tissue perfusion.

/pdf/mechanical-circulatory-support-devices-for-cardiogenic-shock-5gkib6a9o2.pdf

Mechanical Circulatory Support Devices for Cardiogenic Shock: State of the Art.

The fluid challenge is considered the gold standard for diagnosis of fluid responsiveness. The objective of this study was to describe the fluid challenge techniques reported in fluid responsiveness studies and to assess the difference in the proportion of ‘responders,’ (PR) depending on the type of fluid, volume, duration of infusion and timing of assessment. Searches of MEDLINE and Embase were performed for studies using the fluid challenge as a test of cardiac preload with a description of the technique, a reported definition of fluid responsiveness and PR. The primary outcome was the mean PR, depending on volume of fluid, type of fluids, rate of infusion and time of assessment. A total of 85 studies (3601 patients) were included in the analysis. The PR were 54.4% (95% CI 46.9–62.7) where 500 ml was administered (p = 0.71). The PR was not affected by type of fluid. The PR was similar among patients administered a fluid challenge for 10 minutes after the fluid challenge. The proportions of responders were 53.9%, 57.7% and 52.3%, respectively (p = 0.47). The PR decreases with a long infusion time. A standard technique for fluid challenge is desirable.

https://link.springer.com/content/pdf/10.1186/s13054-017-1796-9.pdf

What is the impact of the fluid challenge technique on diagnosis of fluid responsiveness? A systematic review and meta-analysis

Shock is defined as a state in which the circulation is unable to deliver sufficient oxygen to meet the demands of the tissues, resulting in cellular dysoxia and organ failure. In this process, the factors that govern the circulation at a haemodynamic level and oxygen delivery at a microcirculatory level play a major role. This manuscript aims to review the blood flow regulation from macro- and micro-haemodynamic point of view and to discuss new potential therapeutic approaches for cardiovascular instability in patients in cardiovascular shock. Despite the recent advances in haemodynamics, the mechanisms that control the vascular resistance and the venous return are not fully understood in critically ill patients. The physical properties of the vascular wall, as well as the role of the mean systemic filling pressure are topics that require further research. However, the haemodynamics do not totally explain the physiopathology of cellular dysoxia, and several factors such as inflammatory changes at the microcirculatory level can modify vascular resistance and tissue perfusion. Cellular vasoactive mediators and endothelial and glucocalix damage are also involved in microcirculatory impairment. All the levels of the circulatory system must be taken into account. Evaluation of microcirculation may help one to detect under-diagnosed shock, and together with classic haemodynamics, guide one towards the appropriate therapy. Restoration of classic haemodynamic parameters is essential but not sufficient to detect and treat patients in cardiovascular shock.

/pdf/from-cardiac-output-to-blood-flow-auto-regulation-in-shock-2im4fw0lda.pdf

From cardiac output to blood flow auto-regulation in shock

Common ICU procedures

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What is the impact of the fluid challenge technique on diagnosis of fluid responsiveness? A systematic review and meta-analysis

From cardiac output to blood flow auto-regulation in shock

Common ICU procedures