The effects of dobutamine on microcirculatory alterations in patients with septic shock are independent of its systemic effects*

Prognostic value of serum lactate level for mortality in patients with acute kidney injury

BACKGROUND

Serum lactate is associated with mortality in diverse kinds of patients. This study aimed to investigate whether serum lactate level may independently predict mortality in acute kidney injury (AKI) patients.

METHODS

A total of 4461 AKI patients were collected from the Medical Information Mart for Intensive Care (MIMIC III) database and followed up for 365 days. According to serum lactate tertiles, participants were divided into three groups (Q1-Q3) by: Q1 ≤ 1.60 mg/dl, Q2 = 1.61-2.70 mg/dl, and Q3 ≥ 2.71 mg/dl. We calculated the hazard ratio (HR) and 95% confidence intervals (Cls) for mortality across each tertile of lactate by using the Q1 as reference and constructed four models to adjust for the HR of mortality.

RESULTS

Nonsurvivors had significantly higher lactate compared with patients in the survival group. Mortality rate gradually elevated with the increase in serum lactate level (Q1: 29.30%, Q2: 33.40%, Q3: 37.40%). When compared with Q1 after adjustment of all confounders, the HRs of Q3 still was 1.20 (95% Cl 1.05-1.37).

CONCLUSIONS

This study demonstrated that high serum lactate levels were an independent predictor of mortality in AKI patients.

Lactate dynamics in paediatric patients with severe sepsis: insights from a prospective cohort study

BACKGROUND

Sepsis is an infection-related systemic inflammatory response that often leads to elevated lactate levels. Monitoring lactate levels during severe sepsis is vital for influencing clinical outcomes. The aim of this study was to assess the association between plasma lactate levels and mortality in children with severe sepsis or septic shock.

METHODS

The current prospective study was conducted in the PICU of University Children's Hospital. The International Paediatric Sepsis Consensus Conference criteria for Definitions of Sepsis and Organ Failure in 2005 were used to diagnose patients with sepsis. We measured plasma lactate levels upon admission (Lac H0) and 6 h later (Lac H6). The static indices included the absolute lactate values (Lac H0 and Lac H6), while the dynamic indices included the delta-lactate level (ΔLac) and the 6-hour lactate clearance. The 6-hour lactate clearance was calculated using the following formula: [(Lac H0-Lac H6)100/Lac H0]. ΔLac was calculated as the difference between the Lac H0 and Lac H6 levels. Patient survival or death after a PICU stay was the primary outcome.

RESULTS

A total of 46 patients were included in this study: 25 had septic shock, and 21 had severe sepsis. The mortality rate was 54.3%. The Lac H0 did not significantly differ between survivors and nonsurvivors. In contrast, the survivors had significantly lower Lac H6 levels, higher ΔLac levels, and higher 6-hour lactate clearance rates than nonsurvivors. Lactate clearance rates below 10%, 20%, and 30% were significantly associated with mortality. The best cut-off values for the lactate clearance rate and Lac H6 for the prediction of mortality in the PICU were < 10% and ≥ 4 mmol/L, respectively. Patients with higher Lac H6 levels and lower lactate clearance rates had significantly higher PICU mortality based on Kaplan-Meier survival curve analysis.

CONCLUSIONS

This study highlights the significance of lactate level trends over time for the prediction of mortality in the PICU in patients with severe sepsis or septic shock. Elevated lactate levels and decreased lactate clearance six hours after hospitalisation are associated with a higher mortality rate.

The Effects of Dobutamine in Septic Shock: An Updated Narrative Review of Clinical and Experimental Studies

The key objective in the hemodynamic treatment of septic shock is the optimization of tissue perfusion and oxygenation. This is usually achieved by the utilization of fluids, vasopressors, and inotropes. Dobutamine is the inotrope most commonly recommended and used for this purpose. Despite the fact that dobutamine was introduced almost half a century ago in the treatment of septic shock, and there is widespread use of the drug, several aspects of its pharmacodynamics remain poorly understood. In normal subjects, dobutamine increases contractility and lacks a direct effect on vascular tone. This results in augmented cardiac output and blood pressure, with reflex reduction in systemic vascular resistance. In septic shock, some experimental and clinical research suggest beneficial effects on systemic and regional perfusion. Nevertheless, other studies found heterogeneous and unpredictable effects with frequent side effects. In this narrative review, we discuss the pharmacodynamic characteristics of dobutamine and its physiologic actions in different settings, with special reference to septic shock. We discuss studies showing that dobutamine frequently induces tachycardia and vasodilation, without positive actions on contractility. Since untoward effects are often found and therapeutic benefits are occasional, its profile of efficacy and safety seems low. Therefore, we recommend that the use of dobutamine in septic shock should be cautious. Before a final decision about its prescription, efficacy, and tolerance should be evaluated throughout a short period with narrow monitoring of its wanted and side effects.

Towards the personalization of septic shock resuscitation: the fundamentals of ANDROMEDA-SHOCK-2 trial

Septic shock is a highly lethal and prevalent disease. Progressive circulatory dysfunction leads to tissue hypoperfusion and hypoxia, eventually evolving to multiorgan dysfunction and death. Prompt resuscitation may revert these pathogenic mechanisms, restoring oxygen delivery and organ function. High heterogeneity exists among the determinants of circulatory dysfunction in septic shock, and current algorithms provide a stepwise and standardized approach to conduct resuscitation. This review provides the pathophysiological and clinical rationale behind ANDROMEDA-SHOCK-2, an ongoing multicenter randomized controlled trial that aims to compare a personalized resuscitation strategy based on clinical phenotyping and peripheral perfusion assessment, versus standard of care, in early septic shock resuscitation.

The microcirculation in perioperative medicine: a narrative review

The microcirculation describes the network of the smallest vessels in our cardiovascular system. On a microcirculatory level, oxygen delivery is determined by the flow of oxygen-carrying red blood cells in a given single capillary (capillary red blood cell flow) and the density of the capillary network in a given tissue volume (capillary vessel density). Handheld vital videomicroscopy enables visualisation of the capillary bed on the surface of organs and tissues but currently is only used for research. Measurements are generally possible on all organ surfaces but are most often performed in the sublingual area. In patients presenting for elective surgery, the sublingual microcirculation is usually intact and functional. Induction of general anaesthesia slightly decreases capillary red blood cell flow and increases capillary vessel density. During elective, even major, noncardiac surgery, the sublingual microcirculation is preserved and remains functional, presumably because elective noncardiac surgery is scheduled trauma and haemodynamic alterations are immediately treated by anaesthesiologists, usually restoring the macrocirculation before the microcirculation is substantially impaired. Additionally, surgery is regional trauma and thus likely causes regional, rather than systemic, impairment of the microcirculation. Whether or not the sublingual microcirculation is impaired after noncardiac surgery remains a subject of ongoing research. Similarly, it remains unclear if cardiac surgery, especially with cardiopulmonary bypass, impairs the sublingual microcirculation. The effects of therapeutic interventions specifically targeting the microcirculation remain to be elucidated and tested. Future research should focus on further improving microcirculation monitoring methods and investigating how regional microcirculation monitoring can inform clinical decision-making and treatment.

Clinical evaluation of peripheral tissue perfusion as a predictor of mortality in sepsis and septic shock in the intensive care unit: Systematic review and meta-analysis

OBJECTIVE

To determine the diagnostic performance of the clinical evaluation of peripheral tissue perfusion in the prediction of mortality.

DESIGN

Systematic review and meta-analysis.

SETTING

Intensive care unit.

PATIENTS AND PARTICIPANTS

Patients with sepsis and septic shock.

INTERVENTIONS

Studies of patients with sepsis and/or septic shock that associated clinical monitoring of tissue perfusion with mortality were included. A systematic review was performed by searching the PubMed/MEDLINE, Cochrane Library, SCOPUS, and OVID databases.

MAIN VARIABLES OF INTEREST

The risk of bias was assessed with the QUADAS-2 tool. Sensitivity and specificity were calculated to evaluate the predictive accuracy for mortality. Review Manager software version 5.4 was used to draw the forest plot graphs, and Stata version 15.1 was used to build the hierarchical summary receiver operating characteristic model.

RESULTS

Thirteen studies were included, with a total of 1667 patients and 17 analyses. Two articles evaluated the temperature gradient, four evaluated the capillary refill time, and seven evaluated the mottling in the skin. In most studies, the outcome was mortality at 14 or 28 days. The pooled sensitivity of the included studies was 70%, specificity 75.9% (95% CI, 61.6%-86.2%), diagnostic odds ratio 7.41 (95% CI, 3.91-14.04), and positive and negative likelihood ratios 2.91 (95% CI, 1.80-4.72) and 0.39 (95% CI, 0.30-0.51), respectively.

CONCLUSIONS

Clinical evaluation of tissue perfusion at the bedside is a useful tool, with moderate sensitivity and specificity, to identify patients with a higher risk of death among those with sepsis and septic shock.

REGISTRATION

PROSPERO CRD42019134351.

Intraoperative intravenous infusion of lidocaine increases total and small vessel densities of sublingual microcirculation: a randomized prospective pilot study

OBJECTIVE

Multiple organ failure can occur as a result of postoperative complications. Research has indicated that the underlying mechanism of organ dysfunction is a microcirculation disorder. Because of its antioxidant and anti-inflammatory properties, lidocaine has the potential to improve microvascular blood flow. This study was performed to assess the effect of intraoperative intravenous lidocaine infusion on the microcirculation and determine the incidence of postoperative complications.

METHODS

In this prospective randomized double-blind pilot study, 12 patients scheduled for abdominal surgery were randomly allocated to receive an intraoperative infusion of either 1% lidocaine or the same volume of 0.9% sodium chloride solution. The microcirculation was monitored using sidestream dark-field imaging and the vascular occlusion test combined with near-infrared spectroscopy.

RESULTS

Lidocaine significantly increased the total vascular density and small vessel density after 2 hours of infusion, with preservation of 99% to 100% of the capillary perfusion in both groups. No patients developed organ failure.

CONCLUSIONS

An increase in vessel density may be beneficial in major abdominal surgeries because it is associated with better tissue perfusion and oxygen delivery. However, this finding requires further investigation in patients with increased surgical risk. Overall, this study indicates that lidocaine has potential to improve microvascular perfusion.Research Registry number: 9549 (https://www.researchregistry.com/browse-the-registry#home/registrationdetails/650ffd27b3f547002bd7635f/).

Microcirculation and Mitochondria: The Critical Unit

Critical illness is often accompanied by a hemodynamic imbalance between macrocirculation and microcirculation, as well as mitochondrial dysfunction. Microcirculatory disorders lead to abnormalities in the supply of oxygen to tissue cells, while mitochondrial dysfunction leads to abnormal energy metabolism and impaired tissue oxygen utilization, making these conditions important pathogenic factors of critical illness. At the same time, there is a close relationship between the microcirculation and mitochondria. We introduce here the concept of a "critical unit", with two core components: microcirculation, which mainly comprises the microvascular network and endothelial cells, especially the endothelial glycocalyx; and mitochondria, which are mainly involved in energy metabolism but perform other non-negligible functions. This review also introduces several techniques and devices that can be utilized for the real-time synchronous monitoring of the microcirculation and mitochondria, and thus critical unit monitoring. Finally, we put forward the concepts and strategies of critical unit-guided treatment.

Transfusion increased skin blood flow when initially low in volume-resuscitated patients without acute bleeding

Background

Alterations in skin blood flow is a marker of inadequate tissue perfusion in critically ill patients after initial resuscitation. The effects of red blood cell transfusions (RBCT) on skin perfusion are not described in this setting. We evaluated the effects of red blood cell transfusions on skin tissue perfusion in critically ill patients without acute bleeding after initial resuscitation.

Methods

A prospective observational study included 175 non-bleeding adult patients after fluid resuscitation requiring red blood cell transfusions. Using laser Doppler, we measured finger skin blood flow (SBF) at skin basal temperature (SBFBT), together with mean arterial pressure (MAP), heart rate (HR), hemoglobin (Hb), central venous pressure (CVP), lactate, and central or mixed venous oxygen saturation before and 1 h after RBCT. SBF responders were those with a 20% increase in SBFBT after RBCT.

Results

Overall, SBFBT did not significantly change after RBCT [from 79.8 (4.3-479.4) to 83.4 (4.9-561.6); p = 0.67]. A relative increase equal to or more than 20% in SBFBT after RBCT (SBF responders) was observed in 77/175 of RBCT (44%). SBF responders had significantly lower SBFBT [41.3 (4.3-279.3) vs. 136.3 (6.5-479.4) perfusion units; p < 0.01], mixed or central venous oxygen saturation (62.5 ± 9.2 vs. 67.3% ± 12.0%; p < 0.01) and CVP (8.3 ± 5.1 vs. 10.3 ± 5.6 mmHg; p = 0.03) at baseline than non-responders. SBFBT increased in responders [from 41.3 (4.3-279.3) to 93.1 (9.8-561.6) perfusion units; p < 0.01], and decreased in the non-responders [from 136.3 (6.5-479.4) to 80.0 (4.9-540.8) perfusion units; p < 0.01] after RBCT. Pre-transfusion SBFBT was independently associated with a 20% increase in SBFBT after RBCT. Baseline SBFBT had an area under receiver operator characteristic of 0.73 (95% CI, 0.68-0.83) to predict SBFBT increase; A SBFBT of 73.0 perfusion units (PU) had a sensitivity of 71.4% and a specificity of 70.4% to predict SBFBT increase after RBCT. No significant differences in SBFBT were observed after RBCT in different subgroup analyses.

Conclusion

The skin blood flow is globally unaltered by red blood cell transfusions in non-bleeding critically ill patients after initial resuscitation. However, a lower SBFBT at baseline was associated with a relative increase in skin tissue perfusion after RBCT.

Microcirculation-guided resuscitation in sepsis: the next frontier?

Microcirculatory dysfunction plays a key role in the pathogenesis of tissue dysoxia and organ failure in sepsis. Sublingual videomicroscopy techniques enable the real-time non-invasive assessment of microvascular blood flow. Alterations in sublingual microvascular perfusion were detected during sepsis and are associated with poor outcome. More importantly, sublingual videomicroscopy allowed to explore the effects of commonly applied resuscitative treatments in septic shock, such as fluids, vasopressors and inotropes, and showed that the optimization of macro-hemodynamic parameters may not be accompanied by an improvement in microvascular perfusion. This loss of "hemodynamic coherence," i.e., the concordance between the response of the macrocirculation and the microcirculation, advocates for the integration of microvascular monitoring in the management of septic patients. Nonetheless, important barriers remain for a widespread use of sublingual videomicroscopy in the clinical practice. In this review, we discuss the actual limitations of this technique and future developments that may allow an easier and faster evaluation of the microcirculation at the bedside, and propose a role for sublingual microvascular monitoring in guiding and titrating resuscitative therapies in sepsis.

Use of CO2-Derived Variables in Cardiac Intensive Care Unit: Pathophysiology and Clinical Implications

Shock is a life-threatening condition, and its timely recognition is essential for adequate management. Pediatric patients with congenital heart disease admitted to a cardiac intensive care unit (CICU) after surgical corrections are particularly at risk of low cardiac output syndrome (LCOS) and shock. Blood lactate levels and venous oxygen saturation (ScVO₂) are usually used as shock biomarkers to monitor the efficacy of resuscitation efforts, but they are plagued by some limitations. Carbon dioxide (CO₂)-derived parameters, namely veno-arterial CO₂ difference (ΔCCO₂) and the VCO₂/VO₂ ratio, may represent a potentially valuable addition as sensitive biomarkers to assess tissue perfusion and cellular oxygenation and may represent a valuable addition in shock monitoring. These variables have been mostly studied in the adult population, with a strong association between ΔCCO₂ or VCO₂/VO₂ ratio and mortality. In children, particularly in CICU, few studies looked at these parameters, while they reported promising results on the use of CO₂-derived indices for patients' management after cardiac surgeries. This review focuses on the physiological and pathophysiological determinants of ΔCCO₂ and VCO₂/VO₂ ratio while summarizing the actual state of knowledge on the use of CO₂-derived indices as hemodynamical markers in CICU.

Novelties in the evaluation of microcirculation in septic shock

Microvascular alterations were first described in critically ill patients about 20 years ago. These alterations are characterized by a decrease in vascular density and presence of non-perfused capillaries close to well-perfused vessels. In addition, heterogeneity in microvascular perfusion is a key finding in sepsis. In this narrative review, we report our actual understanding of microvascular alterations, their role in the development of organ dysfunction, and the implications for outcome. Herein, we discuss the state of the potential therapeutic interventions and the potential impact of novel therapies. We also discuss how recent technologic development may affect the evaluation of microvascular perfusion.

New Hydrogels Based on Agarose/Phytagel and Peptides

Short aromatic peptide derivatives, i.e., peptides or amino acids modified with aromatic groups, such as 9-fluorenylmethoxycarbonyl (Fmoc), can self-assemble into extracellular matrix-like hydrogels due to their nanofibrillar architecture. Among different types of amino acids, lysine (Lys) and glycine (Gly) are involved in multiple physiological processes, being key factors in the proper growth of cells, carnitine production, and collagen formation. The authors have previously successfully presented the possibility of obtaining supramolecular gels based on Fmoc-Lys-Fmoc and short peptides such as Fmoc-Gly-Gly-Gly in order to use them as a substrate for cell cultures. This paper investigates how the introduction of a gelling polymer can influence the properties of the network as well as the compatibility of the resulting materials with different cell types. A series of hydrogel compositions consisting of combinations of Fmoc-Lys-Fmoc and Fmoc-Gly-Gly-Gly with Agarose and Phytagel are thus obtained. All compositions form structured gels as shown by rheological studies and scanning electron microscopy. Fourier transform infrared spectroscopy analysis evidences the formation of H-bonds between the polysaccharides and amino acids or short peptides. Moreover, all gels exhibit good cell viability on fibroblasts as demonstrated by a live-dead staining test and good in vivo biocompatibility, which highlights the great potential of these biomaterials for biomedical applications.

Lactic Acidosis Related to Pharmacotherapy and Human Diseases

Lactic acidosis represents one of the most common conditions that can compromise the health of intensive care unit (ICU) patients, increasing the mortality of patients with high levels of Lactate who do not receive a proper treatment within the first 6 h of hospitalization. There are two enantiomers of lactic acid: L-lactic acid (when the concentration increases, it can lead to a state of severe acidemia risking cardiovascular collapse, causing an increase in mortality in ICU patients) and D lactic acid (produced in the human organism by microbiota and its production increases during some pathological status). Generally, increased levels of serum lactic acid could be due to numerous factors, including hypoxia (caused for example by septic/cardiogenic/hypovolemic or obstructive shock), specific pathologies (e.g., liver disease), use of some drugs (e.g., metformin), presence of toxins, and trauma. Since the underlying cause could be fatal for the ICU patient, it is important to understand the root of this clinical status with a view to correct it and prevent the risk of a poor clinical outcome. Prevention and early treatment are the keys to control the negative clinical consequences. The aim of this review is to revise the scientific literature for further confirmation about the importance of early identification of acidotic statuses and to underline how an early diagnosis can prevent the worst clinical outcome, especially for ICU patients who are more fragile compared to the general population.

Hemodynamic effects and tolerance of dobutamine for myocardial dysfunction during septic shock: An observational multicenter prospective echocardiographic study

Background

The role of dobutamine during septic shock resuscitation is still controversial.

Methods

The aim of this prospective multicentre study was to comprehensively characterize the hemodynamic response of septic shock patients with systolic myocardial dysfunction to incremental doses of dobutamine (0, 5, 10, and 15 μg/kg/min).

Results

Thirty two patients were included in three centers. Dobutamine significantly increased contractility indices of both ventricles [crude and afterload-adjusted left ventricular (LV) ejection fraction, global LV longitudinal peak systolic strain, tissue Doppler peak systolic wave at mitral and tricuspid lateral annulus, and tricuspid annular plane excursion) as well as global function indices (stroke volume and cardiac index) and diastolic function (increased e' and decreased E/e' ratio at lateral mitral annulus). Dobutamine also induced a significant decrease in arterial pressure and cardiac afterload indices (effective arterial elastance, systemic vascular resistance and diastolic shock index). Oxygen transport, oxygen consumption and carbon dioxide production all increased with dobutamine, without change in the respiratory quotient or lactate. Dobutamine was discontinued for poor tolerance in a majority of patients (n = 21, 66%) at any dose and half of patients (n = 15, 47%) at low-dose (5 μg/kg/min). Poor tolerance to low-dose dobutamine was more frequent in case of acidosis, was associated with lower vasopressor-free days and survival at day-14.

Conclusion

In patients with septic myocardial dysfunction, dobutamine induced an overall improvement of echocardiographic parameters of diastolic and systolic function, but was poorly tolerated in nearly two thirds of patients, with worsening vasoplegia. Patients with severe acidosis seemed to have a worse response to dobutamine.

Venoarterial extracorporeal membrane oxygenation flow or dobutamine to improve microcirculation during ECMO for refractory cardiogenic shock

PURPOSE

Venoarterial extracorporeal membrane oxygenation (VA ECMO) effectively supports refractory cardiogenic shock (rCS), and sustains macro- and microcirculations. We investigated the respective impact of increasing VA ECMO flow or dobutamine dose on microcirculation in stabilized VA ECMO-treated patients with rCS.

METHODS

In this prospective interventional study, we included consecutive intubated patients, with ECMO-supported rCS and hemodynamic stability, able to tolerate stepwise incremental dobutamine doses (from 5 to 20 gamma/kg/min) or ECMO flows (progressive increase by 25% above baseline ECMO flow. Baseline was defined as the lowest VA ECMO flow and dobutamine 5 μg/kg/min (DOBU₅) to maintain mean arterial pressure (MAP) ≥ 65 mmHg. Macro- and microcirculations were evaluated after 30 min at each level.

RESULTS

Fourteen patients were included. Macro- and microcirculations were assessed 2 [2-5] days post-ECMO onset. Dobutamine-dose increments did not modify any microcirculation parameters. Only the De Backer score tended to be reduced (p = 0.08) by ECMO-flow increments whereas other microcirculation parameters were not affected. These findings did not differ between patients successfully weaned-off ECMO (n = 6) or not.

CONCLUSIONS

When macrocirculation has already been restored in patients with ECMO-supported rCS, increasing dobutamine (above 5 μg/kg/min) or ECMO flow did not further improve microcirculation.

Basic mechanisms in cardiogenic shock: part 1-definition and pathophysiology

Cardiogenic shock mortality rates remain high despite significant advances in cardiovascular medicine and the widespread uptake of mechanical circulatory support systems. Except for early invasive angiography and percutaneous coronary intervention of the infarct-related artery, the most widely used therapeutic measures are based on low-quality evidence. The grim prognosis and lack of high-quality data warrant further action. Part 1 of this two-part educational review defines cardiogenic shock and discusses current treatment strategies. In addition, we summarize current knowledge on basic mechanisms in the pathophysiology of cardiogenic shock, focusing on inflammation and microvascular disturbances, which may ultimately be translated into diagnostic or therapeutic approaches to improve the outcome of our patients.

Endothelial Activation and Microcirculatory Disorders in Sepsis

The vascular endothelium is crucial for the maintenance of vascular homeostasis. Moreover, in sepsis, endothelial cells can acquire new properties and actively participate in the host's response. If endothelial activation is mostly necessary and efficient in eliminating a pathogen, an exaggerated and maladaptive reaction leads to severe microcirculatory damage. The microcirculatory disorders in sepsis are well known to be associated with poor outcome. Better recognition of microcirculatory alteration is therefore essential to identify patients with the worse outcomes and to guide therapeutic interventions. In this review, we will discuss the main features of endothelial activation and dysfunction in sepsis, its assessment at the bedside, and the main advances in microcirculatory resuscitation.

A novel non-invasive method of measuring microcirculatory perfusion and blood velocity in infants: a pilot study

Current haemodynamic monitoring is mainly aimed at the macrocirculation. Multiple studies have demonstrated the importance of the microcirculation in relation to the patient’s condition and impact of treatment strategies. However, continuous monitoring of the microcirculation is not yet possible in the neonatal field. A novel dynamic light scattering (DLS) sensor technology for continuous monitoring of the microcirculation was investigated in the neonatal population. Thirty-one haemodynamically stable infants were included. Sequential measurements at the forehead, upper extremity, thorax, abdomen and lower extremity were conducted with the DLS sensor. For analyses stable measurements were selected. The DLS parameters, total blood flow (TBF) and relative blood velocity (RBV), were compared between measurement locations. Changes in relative haemodynamic indices (relHIs), indicating the distribution of blood flow in the microcirculatory blood vessels, were associated with heart rate decelerations. Measurements performed at the forehead had significantly lower TBF levels, compared to measurements at other locations. Early changes in relHIs around a heart rate deceleration were recorded a median (IQR) of 22.0 (13.5–27.0) s before the onset. Measurement of the currently unavailable parameters TBF, RBV and relHIs is possible with DLS technology. Validation of the DLS technology is needed for clinical implementation.

[Vasoactive drugs in the treatment of septic shock]

Septic shock is a high mortality complication frequently associated with sepsis. Early initiation of vasopressor treatment, even before completion of initial fluid resuscitation, is a determining factor in prognosis. In this sense, norepinephrine continues to be the drug of first choice, although there is increasing evidence of benefit combining it with other non-adrenergic drugs, such as vasopressin, instead of escalating norepinephrine doses. The pathophysiology of septic shock is multifactorial, and sometimes is associated with a situation of myocardial dysfunction that contributes to hemodynamic instability. It is essential to identify this situation since it worsens the prognosis and may benefit from combined treatment with inotropic drugs. There are novel vasoactive agents under study, more selective than the classic ones that in a next future could help to design more individualized and precise treatments. In the present work, the current knowledge about vasoactive drugs and their use in the management of septic shock is summarized according to the most recent scientific evidence.

Advances in Microcirculatory Assessment: A Game Changer in Sepsis Management or the Latest Fad?!

Gupta R, Ray S. Advances in Microcirculatory Assessment: A Game Changer in Sepsis Management or the Latest Fad? Indian J Crit Care Med 2022;26(3):261–263.

Microcirculation during surgery

Throughout the long history of surgery, there has been great advancement in the hemodynamic management of surgical patients. Traditionally, hemodynamic management has focused on macrocirculatory monitoring and intervention to maintain appropriate oxygen delivery. However, even after optimization of macro-hemodynamic parameters, microcirculatory dysfunction, which is related to higher postoperative complications, occurs in some patients. Although the clinical significance of microcirculatory dysfunction has been well reported, little is known about interventions to recover microcirculation and prevent microcirculatory dysfunction. This may be at least partly caused by the fact that the feasibility of monitoring tools to evaluate microcirculation is still insufficient for use in routine clinical practice. However, considering recent advancements in these research fields, with more popular use of microcirculation monitoring and more clinical trials, clinicians may better understand and manage microcirculation in surgical patients in the future. In this review, we describe currently available methods for microcirculatory evaluation. The current knowledge on the clinical relevance of microcirculatory alterations has been summarized based on previous studies in various clinical settings. In the latter part, pharmacological and clinical interventions to improve or restore microcirculation are also presented.

Association between dose of catecholamines and markers of organ injury early after out-of-hospital cardiac arrest

BACKGROUND

Catecholamines are recommended as first-line drugs to treat hemodynamic instability after out-of-hospital cardiac arrest (OHCA). The benefit-to-risk ratio of catecholamines is dose dependent, however, their effect on metabolism and organ function early after OHCA has not been investigated.

METHODS

The Post-Cardiac Arrest Syndrome (PCAS) pilot study was a prospective, observational, multicenter study. The primary outcomes of this analysis were association between norepinephrine/cumulative catecholamines doses and neuron specific enolase (NSE)/lactate concentration over the first 72 hours after resuscitation. The association was adjusted for proven OHCA mortality predictors and verified with propensity score matching (PSM).

RESULTS

Overall 148 consecutive OHCA patients; aged 18-91 (62.9 ± 15.27), 41 (27.7%) being female, were included. Increasing norepinephrine and cumulative catecholamines doses were significantly associated with higher NSE concentration on admission (r = 0.477, p < 0.001; r = 0.418, p < 0.001) and at 24 hours after OHCA (r = 0.339, p < 0.01; r = 0.441, p < 0.001) as well as with higher lactate concentration on admission (r = 0.404, p < 0.001; r = 0.280, p < 0.01), at 24 hours (r = 0.476, p < 0.00; r = 0.487, p < 0.001) and 48 hours (r = 0.433, p < 0.01; r = 0.318, p = 0.01) after OHCA. The associations remained significant up to 48 hours in non-survivors after PSM.

CONCLUSIONS

Increasing the dose of catecholamines is associated with higher lactate and NSE concentration, which may suggest their importance for tissue oxygen delivery, anaerobic metabolism, and organ function early after OHCA.

[The role of the microcirculation in the pathogenesis of organ dysfunction]

The microcirculation includes all blood and lymph vessels with a diameter < 100 µm. Microcirculatory dysfunction is common in critically ill patients and is closely associated with both the severity of (multi-)organ dysfunction and mortality. The nature and extent of microcirculatory dysfunction differ depending on the underlying disease and are most pronounced in patients with systemic inflammation (e. g. sepsis), specific infections (e. g. malaria, dengue) or thrombocytopenia-associated multiple organ failure. This manuscript provides an overview of the pathophysiology, monitoring and therapy of microcirculatory dysfunction in the critically ill patient.

Current practice and evolving concepts in septic shock resuscitation

Clinical and pathophysiological understanding of septic shock has progressed exponentially in the previous decades, translating into a steady decrease in septic shock-related morbidity and mortality. Even though large randomized, controlled trials have addressed fundamental aspects of septic shock resuscitation, many questions still exist. In this review, we will describe the current standards of septic shock resuscitation, but the emphasis will be placed on evolving concepts in different domains such as clinical resuscitation targets, adequate use of fluids and vasoactive drugs, refractory shock, and the use of extracorporeal therapies. Multiple research opportunities remain open, and collaborative endeavors should be performed to fill in these gaps.

Lactate Clearance Is Associated With Improved Survival in Cardiogenic Shock: A Systematic Review and Meta-Analysis of Prognostic Factor Studies

OBJECTIVE

Elevated blood lactate levels are strongly associated with mortality in patients with cardiogenic shock. Recent evidence suggests that the degree and rate at which blood lactate levels decrease after the initiation of treatment may be equally important in patient prognosis. We performed a systematic review and meta-analysis to evaluate the usefulness of lactate clearance as a prognostic factor in cardiogenic shock.

METHODS AND RESULTS

We performed searches of Ovid MEDLINE, Elsevier EMBASE, EBM Reviews-Cochrane Central Register of Controlled Trials, and Web of Science to identify studies comparing lactate clearance between survivors and nonsurvivors at one or more timepoints. Both prospective and retrospective studies were eligible for inclusion. Two study investigators independently screened, extracted data, and assessed the quality of all included studies. Twelve studies were included in the meta-analysis. The median lactate clearance at 6-8 hours was 21.9% (interquartile range [IQR] 14.6%-42.1%) in survivors and 0.6% (IQR -3.7% to 14.6%) in nonsurvivors. At 24 hours, the median lactate clearance was 60.7% (IQR 58.1%-76.3%) and 40.3% (IQR 30.2%-55.8%) in survivors and nonsurvivors, respectively. Accordingly, the pooled mean difference in lactate clearance between survivors and nonsurvivors at 6-8 hours was 17.3% (95% CI 11.6%-23.1%, P < .001) at 6-8 hours and 27.9% (95% CI 14.1%-41.7%, P < .001) at 24 hours.

CONCLUSIONS

Survivors had significantly greater lactate clearance at 6-8 hours and at 24 hours compared with nonsurvivors, suggesting that lactate clearance is an important prognostic marker in cardiogenic shock.

Is the Sympathetic System Detrimental in the Setting of Septic Shock, with Antihypertensive Agents as a Counterintuitive Approach? A Clinical Proposition

Mortality in the setting of septic shock varies between 20% and 100%. Refractory septic shock leads to early circulatory failure and carries the worst prognosis. The pathophysiology is poorly understood despite studies of the microcirculatory defects and the immuno-paralysis. The acute circulatory distress is treated with volume expansion, administration of vasopressors (usually noradrenaline: NA), and inotropes. Ventilation and anti-infectious strategy shall not be discussed here. When circulation is considered, the literature is segregated between interventions directed to the systemic circulation vs. interventions directed to the micro-circulation. Our thesis is that, after stabilization of the acute cardioventilatory distress, the prolonged sympathetic hyperactivity is detrimental in the setting of septic shock. Our hypothesis is that the sympathetic hyperactivity observed in septic shock being normalized towards baseline activity will improve the microcirculation by recoupling the capillaries and the systemic circulation. Therefore, counterintuitively, antihypertensive agents such as beta-blockers or alpha-2 adrenergic agonists (clonidine, dexmedetomidine) are useful. They would reduce the noradrenaline requirements. Adjuncts (vitamins, steroids, NO donors/inhibitors, etc.) proposed to normalize the sepsis-evoked vasodilation are not reviewed. This itemized approach (systemic vs. microcirculation) requires physiological and epidemiological studies to look for reduced mortality.

Addition of admission lactate levels to Baux score improves mortality prediction in severe burns

Risk adjustment and mortality prediction models are central in optimising care and for benchmarking purposes. In the burn setting, the Baux score and its derivatives have been the mainstay for predictions of mortality from burns. Other well-known measures to predict mortality stem from the ICU setting, where, for example, the Simplified Acute Physiology Score (SAPS 3) models have been found to be instrumental. Other attempts to further improve the prediction of outcome have been based on the following variables at admission: Sequential Organ Failure Assessment (_aSOFA) score, determinations of _aLactate or Neutrophil to Lymphocyte Ratio (_aNLR). The aim of the present study was to examine if estimated mortality rate (EMR, SAPS 3), _aSOFA, _aLactate, and _aNLR can, either alone or in conjunction with the others, improve the mortality prediction beyond that of the effects of age and percentage total body surface area (TBSA%) burned among patients with severe burns who need critical care. This is a retrospective, explorative, single centre, registry study based on prospectively gathered data. The study included 222 patients with median (25th–75th centiles) age of 55.0 (38.0 to 69.0) years, TBSA% burned was 24.5 (13.0 to 37.2) and crude mortality was 17%. As anticipated highest predicting power was obtained with age and TBSA% with an AUC at 0.906 (95% CI 0.857 to 0.955) as compared with EMR, _aSOFA, _aLactate and _aNLR. The largest effect was seen thereafter by adding _aLactate to the model, increasing AUC to 0.938 (0.898 to 0.979) (p < 0.001). Whereafter, adding EMR, _aSOFA, and _aNLR, separately or in combinations, only marginally improved the prediction power. This study shows that the prediction model with age and TBSA% may be improved by adding _aLactate, despite the fact that _aLactate levels were only moderately increased. Thereafter, adding EMR, _aSOFA or _aNLR only marginally affected the mortality prediction.

Unfractionated Heparin Improves the Intestinal Microcirculation in a Canine Septic Shock Model

Background

Alterations of microcirculation are associated with organ hypoperfusion and high mortality in septic shock. This study is aimed at investigating the effects of unfractionated heparin (UFH) on intestinal microcirculatory perfusion and systemic circulation in a septic shock model.

Methods

Twenty-four beagle dogs were randomly allocated into four groups: (a) sham group: healthy controls, (b) shock group: septic shock induced by Escherichia coli, (c) basic therapy group: septic shock animals treated with antibiotics and 10 ml/kg/h saline, and (d) heparin group: septic shock animals treated with basic therapy plus UFH. Hemodynamic variables were measured within 24 h after E. coli administration. The intestinal microcirculation was simultaneously investigated with a sidestream dark-field imaging technique. Additionally, the function of vital organs was evaluated at 12 h postadministration (T12).

Results

E. coli induced a progressive septic shock in which the mean arterial pressure (MAP) decreased and lactate levels sharply increased, accompanied by deteriorated microvessel perfusion. While basic therapy partially improved the microvascular flow index and the perfused microvessel density in the jejunal villi, UFH significantly restored major microcirculation variables at T12. Physiological variables, including MAP, urine output, and lactate levels, were improved by UFH, whereas some hemodynamic indices were not affected by UFH. With respect to organ function, UFH increased the platelet count and decreased the creatinine level.

Conclusions

UFH improves microcirculatory perfusion of the small intestine independently of the changes in systemic hemodynamic variables in a canine model of septic shock, thereby improving coagulation and renal function.

Monitoring skin blood flow to rapidly identify alterations in tissue perfusion during fluid removal using continuous veno-venous hemofiltration in patients with circulatory shock

Background

Continuous veno-venous hemofiltration (CVVH) can be used to reduce fluid overload and tissue edema, but excessive fluid removal may impair tissue perfusion. Skin blood flow (SBF) alters rapidly in shock, so its measurement may be useful to help monitor tissue perfusion.

Methods

In a prospective, observational study in a 35-bed department of intensive care, all patients with shock who required fluid removal with CVVH were considered for inclusion. SBF was measured on the index finger using skin laser Doppler (Periflux 5000, Perimed, Järfälla, Sweden) for 3 min at baseline (before starting fluid removal, T0), and 1, 3 and 6 h after starting fluid removal. The same fluid removal rate was maintained throughout the study period. Patients were grouped according to absence (Group A) or presence (Group B) of altered tissue perfusion, defined as a 10% increase in blood lactate from T0 to T6 with the T6 lactate ≥ 1.5 mmol/l. Receiver operating characteristic curves were constructed and areas under the curve (AUROC) calculated to identify variables predictive of altered tissue perfusion. Data are reported as medians [25th–75th percentiles].

Results

We studied 42 patients (31 septic shock, 11 cardiogenic shock); median SOFA score at inclusion was 9 [8–12]. At T0, there were no significant differences in hemodynamic variables, norepinephrine dose, lactate concentration, ScvO₂ or ultrafiltration rate between groups A and B. Cardiac index and MAP did not change over time, but SBF decreased in both groups (p < 0.05) throughout the study period. The baseline SBF was lower (58[35–118] vs 119[57–178] perfusion units [PU], p = 0.03) and the decrease in SBF from T0 to T1 (ΔSBF%) higher (53[39–63] vs 21[12–24]%, p = 0.01) in group B than in group A. Baseline SBF and ΔSBF% predicted altered tissue perfusion with AUROCs of 0.83 and 0.96, respectively, with cut-offs for SBF of ≤ 57 PU (sensitivity 78%, specificity 87%) and ∆SBF% of ≥ 45% (sensitivity 92%, specificity 99%).

Conclusion

Baseline SBF and its early reduction after initiation of fluid removal using CVVH can predict worsened tissue perfusion, reflected by an increase in blood lactate levels.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00847-z.

Sweat the small stuff: The human microvasculature and heart disease

Traditionally thought of primarily as the predominant regulator of myocardial perfusion, it is becoming more accepted that the human coronary microvasculature also exerts a more direct influence on the surrounding myocardium. Coronary microvascular dysfunction (CMD) not only precedes large artery atherosclerosis, but is associated with other cardiovascular diseases such as heart failure with preserved ejection fraction and hypertrophic cardiomyopathy. It is also highly predictive of cardiovascular events in patients with or without atherosclerotic cardiovascular disease. This review focuses on this recent paradigm shift and delves into the clinical consequences of CMD. Concepts of how resistance arterioles contribute to disease will be discussed, highlighting how the microvasculature may serve as a potential target for novel therapies and interventions. Finally, both invasive and non-invasive methods with which to assess the coronary microvasculature both for diagnostic and risk stratification purposes will be reviewed.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Septic shock: a microcirculation disease

PURPOSE OF REVIEW

The aim of this study was to discuss the implication of microvascular dysfunction in septic shock.

RECENT FINDINGS

Resuscitation of sepsis has focused on systemic haemodynamics and, more recently, on peripheral perfusion indices. However, central microvascular perfusion is altered in sepsis and these alterations often persist despite normalization of various macro haemodynamic resuscitative goals. Endothelial dysfunction is a key element in sepsis pathophysiology. It is responsible for the sepsis-induced hypotension. In addition, endothelial dysfunction is also implicated involved in the activation of inflammation and coagulation processes leading to amplification of the septic response and development of organ dysfunction. It also promotes an increase in permeability, mostly at venular side, and impairs microvascular perfusion and hence tissue oxygenation.Microvascular alterations are characterized by heterogeneity in blood flow distribution, with adequately perfused areas in close vicinity to not perfused areas, thus characterizing the distributive nature of septic shock. Such microvascular alterations have profound implications, as these are associated with organ dysfunction and unfavourable outcomes. Also, the response to therapy is highly variable and cannot be predicted by systemic hemodynamic assessment and hence cannot be detected by classical haemodynamic tools.

SUMMARY

Microcirculation is a key element in the pathophysiology of sepsis. Even if microcirculation-targeted therapy is not yet ready for the prime time, understanding the processes implicated in microvascular dysfunction is important to prevent chasing systemic hemodynamic variables when this does not contribute to improve tissue perfusion.

Serum lactate level predicts 6-months mortality in patients with hepatitis B virus-related decompensated cirrhosis: a retrospective study

The prediction of prognosis is an important part of management in hepatitis B virus (HBV)-related decompensated cirrhosis patients with high long-term mortality. Lactate is a known predictor of outcome in critically ill patients. The aim of this study was to assess the prognostic value of lactate in HBV-related decompensated cirrhosis patients. We performed a single-centre, observational, retrospective study of 405 HBV-related decompensated cirrhosis patients. Individuals were evaluated within 24 h after admission and the primary outcome was evaluated at 6-months. Multivariable analyses were used to determine whether lactate was independently associated with the prognosis of HBV-related decompensated cirrhosis patients. The area under the ROC (AUROC) was calculated to assess the predictive accuracy compared with existing scores. Serum lactate level was significantly higher in non-surviving patients than in surviving patients. Multivariable analyses demonstrated that lactate was an independent risk factor of 6-months mortality (odds ratio: 2.076, P < 0.001). Receiver operating characteristic (ROC) curves were drawn to evaluate the discriminative ability of lactate for 6-months mortality (AUROC: 0.716, P < 0.001). Based on our patient cohort, the new scores (Model For End-Stage Liver Disease (MELD) + lactate score, Child–Pugh + lactate score) had good accuracy for predicting 6-months mortality (AUROC = 0.769, P < 0.001; AUROC = 0.766, P < 0.001). Additionally, the performance of the new scores was superior to those of existing scores (all P < 0.001). Serum lactate at admission may be useful for predicting 6-months mortality in HBV-related decompensated cirrhosis patients, and the predictive value of the MELD score and Child–Pugh score was improved by adjusting lactate. Serum lactate should be part of the rapid diagnosis and initiation of therapy to improve clinical outcome.

Biochemical markers for clinical monitoring of tissue perfusion

The assessment and monitoring of the tissue perfusion is extremely important in critical conditions involving circulatory shock. There is a wide range of established methods for the assessment of cardiac output as a surrogate of oxygen delivery to the peripheral tissues. However, the evaluation of whether particular oxygen delivery is sufficient to ensure cellular metabolic demands is more challenging. In recent years, specific biochemical parameters have been described to indicate the status between tissue oxygen demands and supply. In this review, the authors summarize the application of some of these biochemical markers, including mixed venous oxygen saturation (S_vO₂), lactate, central venous–arterial carbon dioxide difference (PCO₂ gap), and PCO₂ gap/central arterial-to-venous oxygen difference (C_a–vO₂) for hemodynamic assessment of tissue perfusion. The thorough monitoring of the adequacy of tissue perfusion and oxygen supply in critical conditions is essential for the selection of the most appropriate therapeutic strategy and it is associated with improved clinical outcomes.

Monitoring Microcirculation: Utility and Barriers - A Point-of-View Review

Microcirculation is a particular organ of the cardiovascular system. The goal of this narrative review is a critical reappraisal of the present knowledge of microcirculation monitoring, mainly focused on the videomicroscopic evaluation of sublingual microcirculation in critically ill patients. We discuss the technological developments in handheld videomicroscopy, which have resulted in adequate tools for the bedside monitoring of microcirculation. By means of these techniques, a large body of evidence has been acquired about the role of microcirculation in the pathophysiological mechanisms of shock, especially septic shock. We review the characteristics of sublingual microcirculation in septic shock, which mainly consist in a decrease in the perfused vascular density secondary to a reduction in the proportion of perfused vessels along with a high heterogeneity in perfusion. Even in patients with high cardiac output, red blood cell velocity is decreased. Thus, hyperdynamic flow is absent in the septic microcirculation. We also discuss the dissociation between microcirculation and systemic hemodynamics, particularly after shock resuscitation, and the different behavior among microvascular beds. In addition, we briefly comment the effects of some treatments on microcirculation. Despite the fact that sublingual microcirculation arises as a valuable goal for the resuscitation in critically ill patients, significant barriers remain present for its clinical application. Most of them are related to difficulties in video acquisition and analysis. We comprehensively analyzed these shortcomings. Unfortunately, a simpler approach, such as the central venous minus arterial PCO₂ difference, is a misleading surrogate for sublingual microcirculation. As conclusion, the monitoring of sublingual microcirculation is an appealing method for monitoring critically ill patients. Nevertheless, the lack of controlled studies showing benefits in terms of outcome, as well as technical limitations for its clinical implementation, render this technique mainly as a research tool.

Automated quantification of tissue red blood cell perfusion as a new resuscitation target

PURPOSE OF REVIEW

Identification of insufficient tissue perfusion is fundamental to recognizing circulatory shock in critically ill patients, and the primary target to restore adequate oxygen delivery. However, the concept of tissue perfusion remains ill-defined and out-of-reach for clinicians as point-of-care resuscitation target. Even though handheld vital microscopy (HVM) provides the technical prerequisites to collect information on tissue perfusion in the sublingual microcirculation, challenges in image analysis prevent quantification of tissue perfusion and manual analysis steps prohibit point-of-care application. The present review aims to discuss recent advances in algorithm-based HVM analysis and the physiological basis of tissue perfusion-based resuscitation parameters.

RECENT FINDINGS

Advanced computer vision algorithm such as MicroTools independently quantify microcirculatory diffusion and convection capacity by HVM and provide direct insight into tissue perfusion, leading to our formulation a functional parameter, tissue red blood cell (RBC) perfusion (tRBCp). Its definition is discussed in terms of the physiology of oxygen transport to the tissue and its expected effect as a point-of-care resuscitation target. Further refinements to microcirculatory monitoring include multiwavelength HVM techniques and maximal recruitable microcirculatory diffusion and convection capacity.

SUMMARY

tRBCp as measured using algorithm-based HVM analysis with an automated software called MicroTools, represents a promising candidate to assess microcirculatory delivery of oxygen for microcirculation-based resuscitation in critically ill patients at the point-of-care.

Mean core to peripheral temperature difference and mean lactate levels in first 6 hours of hospitalisation as two indicators of prognosis: an observational cohort study

Background

To study mean core to peripheral temperature difference (CPTD) and the mean lactate levels over the first 6 h of admission to hospital, as indicators of prognosis in critically ill children.

Methods

A prospective observational study in a tertiary level Pediatrics ICU in Delhi, India. Seventy eight paediatric patients from 1 month to 12 years were studied. Children with physical trauma, post-surgical patients and patients with peripheral vascular disease were excluded. Core temperature (skin over temporal artery) to peripheral temperature (big toe) difference was measured repeatedly every minute over 6 h and mean of temperature difference was calculated. Pediatric Risk of Mortality (PRISM) II, lactate clearance and mean lactate levels during that time were also studied. In-hospital mortality was used as the outcome measure.

Results

Mean temperature difference

During the first 6 h after admission the mean temperature difference was 9.37 ± 2 °C in those who died and 3.71 ± 2.27 °C in those who survived (p < 0.0001). The area under the receiver operating curve (AUROC) was 0.953 (p < 0.0001). The comparable AUROC of PRISM II was 0.999 (p < 0.0001).

Mean Lactate

Mean lactate level in the first 6 h was 7.1 ± 2.02 mg/dl in those who died compared to 2.86 ± 0.87 mg/dl in those who survived (p < 0.0001). The AUROC curve for mean lactate was 0.989 (95% CI = 0.933 to 0.999; p < 0.0001). AUROC for the lactate clearance was 0.682 (p = 0.0214).

Conclusions

The mean core to peripheral temperature difference over the first 6 h is an easy-to-use and non-invasive method that is useful to predict mortality in children admitted to the Pediatric ICU. The mean lactate during the first 6 h of Pediatric ICU admission is a better index of prognosis than the lactate clearance over the same time period. They may be used as components of a scoring system to predict mortality.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-020-02418-w.

Cardio-centric hemodynamic management improves spinal cord oxygenation and mitigates hemorrhage in acute spinal cord injury

Chronic high-thoracic and cervical spinal cord injury (SCI) results in a complex phenotype of cardiovascular consequences, including impaired left ventricular (LV) contractility. Here, we aim to determine whether such dysfunction manifests immediately post-injury, and if so, whether correcting impaired contractility can improve spinal cord oxygenation (SCO₂), blood flow (SCBF) and metabolism. Using a porcine model of T2 SCI, we assess LV end-systolic elastance (contractility) via invasive pressure-volume catheterization, monitor intraparenchymal SCO₂ and SCBF with fiberoptic oxygen sensors and laser-Doppler flowmetry, respectively, and quantify spinal cord metabolites with microdialysis. We demonstrate that high-thoracic SCI acutely impairs cardiac contractility and substantially reduces SCO₂ and SCBF within the first hours post-injury. Utilizing the same model, we next show that augmenting LV contractility with the β-agonist dobutamine increases SCO₂ and SCBF more effectively than vasopressor therapy, whilst also mitigating increased anaerobic metabolism and hemorrhage in the injured cord. Finally, in pigs with T2 SCI survived for 12 weeks post-injury, we confirm that acute hemodynamic management with dobutamine appears to preserve cardiac function and improve hemodynamic outcomes in the chronic setting. Our data support that cardio-centric hemodynamic management represents an advantageous alternative to the current clinical standard of vasopressor therapy for acute traumatic SCI.

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

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

Microcirculation vs. Mitochondria-What to Target?

Circulatory shock is associated with marked disturbances of the macro- and microcirculation and flow heterogeneities. Furthermore, a lack of tissue adenosine trisphosphate (ATP) and mitochondrial dysfunction are directly associated with organ failure and poor patient outcome. While it remains unclear if microcirculation-targeted resuscitation strategies can even abolish shock-induced flow heterogeneity, mitochondrial dysfunction and subsequently diminished ATP production could still lead to organ dysfunction and failure even if microcirculatory function is restored or maintained. Preserved mitochondrial function is clearly associated with better patient outcome. This review elucidates the role of the microcirculation and mitochondria during circulatory shock and patient management and will give a viewpoint on the advantages and disadvantages of tailoring resuscitation to microvascular or mitochondrial targets.

Heart Dysfunction in Sepsis

Cardiac involvement during sepsis frequently occurs. A series of molecules induces a set of changes at the cellular level that result in the malfunction of the myocardium. The understanding of these molecular alterations has simultaneously promoted the implementation of diagnostic strategies that are much more precise and allowed the advance of the therapeutics. The heart is a vital organ for survival. Its well-being ensures the adequate supply of essential elements for organs and tissues.

Manipulating the Microcirculation in Sepsis - the Impact of Vasoactive Medications on Microcirculatory Blood Flow: A Systematic Review

BACKGROUND

Sepsis is life-threatening organ dysfunction because of a dysregulated host response to infection. Disturbed microvascular blood flow is associated with excess mortality and is a potential future target for interventions. This review addresses the evidence for pharmacological manipulation of the microcirculation in sepsis assessed by techniques that evaluate the sublingual microvasculature.

METHODS

Systematic review using a published protocol. Eligibility criteria were studies of septic patients published from January 2000 to February 2018. Interventions were drugs aimed at improving perfusion. Outcome was improvement in microvascular flow using orthogonal polarization spectral, sidestream dark field, or incident dark field imaging (Grades of Recommendation, Assessment, Development, and Evaluation criteria used).

RESULTS

Two thousand six hundred and six articles were screened and 22 included. (6 randomized controlled trials, 12 interventional, 3 observational, and 1 pilot, n = 572 participants). Multiple measurement techniques were described, including: automated analyses, subjective, and composite scoring systems. Norepinephrine was not found to improve microvascular flow (low-grade evidence, n = 6 studies); except in chronic hypertension (low, n = 1 study). Addition of arginine vasopressin or terlipressin to norepinephrine maintained flow while decreasing norepinephrine requirements (high, n = 2 studies). Neither dobutamine nor glyceryl trinitrate consistently improved flow (low, n = 6 studies). A single study (n = 40 participants) demonstrated improved flow with levosimendan (high). In a risk of bias assessment 16/16 interventional, pilot and observational studies were found to be high risk.

CONCLUSIONS

There is no robust evidence to date that any one agent can reproducibly lead to improved microvascular flow. Furthermore, no study demonstrated outcome benefit of one therapeutic agent over another. Updated consensus guidelines could improve comparable reporting of measurements and reduce bias, to enable meaningful comparisons around the effects of individual pharmacological agents.

Assessment of sublingual microcirculation in critically ill patients: consensus and debate

The main concern in shock and resuscitation is whether the microcirculation can carry adequate oxygen to the tissues and remove waste. Identification of an intact coherence between macro- and microcirculation during states of shock and resuscitation shows a functioning regulatory mechanism. However, loss of hemodynamic coherence between the macro and microcirculation can be encountered frequently in sepsis, cardiogenic shock, or any hemodynamically compromised patient. This loss of hemodynamic coherence results in an improvement in macrohemodynamic parameters following resuscitation without a parallel improvement in microcirculation resulting in tissue hypoxia and tissue compromise. Hand-held vital microscopes (HVMs) can visualize the microcirculation and help to diagnose the nature of microcirculatory shock. Although treatment with the sole aim of recruiting the microcirculation is as yet not realized, interventions can be tailored to the needs of the patient while monitoring sublingual microcirculation. With the help of the newly introduced software, called MicroTools, we believe sublingual microcirculation monitoring and diagnosis will be an essential point-of-care tool in managing shock patients.

Optimal target in septic shock resuscitation

Septic shock presents a high risk of morbidity and mortality. Through therapeutic strategies, such as fluid administration and vasoactive agents, clinicians intend to rapidly restore tissue perfusion. Nonetheless, these interventions have narrow therapeutic margins. Adequate perfusion monitoring is paramount to avoid progressive hypoperfusion or detrimental over-resuscitation. During early stages of septic shock, macrohemodynamic derangements, such as hypovolemia and decreased cardiac output (CO) tend to predominate. However, during late septic shock, endothelial and coagulation dysfunction induce severe alterations of the microcirculation, making it more difficult to achieve tissue reperfusion. Multiple perfusion variables have been described in the literature, from bedside clinical examination to complex laboratory tests. Moreover, all of them present inherent flaws and limitations. After the ANDROMEDA-SHOCK trial, there is evidence that capillary refill time (CRT) is an interesting resuscitation target, due to its rapid kinetics and correlation with deep hypoperfusion markers. New concepts such as hemodynamic coherence and flow responsiveness may be used at the bedside to select the best treatment strategies at any time-point. A multimodal perfusion monitoring and an integrated analysis with macrohemodynamic parameters is mandatory to optimize the resuscitation of septic shock patients.

Inodilators in septic shock: should these be used?

Septic shock involves a complex interaction between abnormal vasodilation, relative and/or absolute hypovolemia, myocardial dysfunction, and altered blood flow distribution to the tissues. Fluid administration, vasopressor support and inotropes, represent fundamental pieces of quantitative resuscitation protocols directed to assist the restoration of impaired tissue perfusion during septic shock. Indeed, current recommendations on sepsis management include the use of inotropes in the case of myocardial dysfunction, as suggested by a low cardiac output, increased filling pressures, or persisting signals of tissue hypoperfusion despite an adequate correction of intravascular volume and mean arterial pressure by fluid administration and vasopressor support. Evidence supporting the use of inotropes in sepsis and septic shock is mainly based on physiological studies. Most of them suggest a beneficial effect of inotropes on macro hemodynamics especially when sepsis coexists with myocardial dysfunction; others, however, have demonstrated variable results on regional splanchnic circulation, while others suggest favorable effects on microvascular distribution independently of its impact on cardiac output. Conversely, impact of inodilators on clinical outcomes in this context has been more controversial. Use of dobutamine has not been consistently related with more favorable clinical results, while systematic administration of levosimendan in sepsis do not prevent the development of multiorgan dysfunction, even in patients with evidence of myocardial dysfunction. Nevertheless, a recent metanalysis of clinical studies suggests that cardiovascular support regimens based on inodilators in sepsis and septic shock could provide some beneficial effect on mortality, while other one corroborated such effect on mortality specially in patients with proved lower cardiac output. Thus, using or not inotropes during sepsis and septic shock remains as controversy matter that deserves more research efforts.

Lymphatic flow modulation as adjunct therapy for septic shock

The lymphatic system is an important component of human health and is critical in maintaining microcirculatory flow and immune system homeostasis. During septic shock, increased capillary permeability results in excess filtration of intravascular fluid and solutes producing interstitial edema with subsequent hydrostatic and oncotic gradient breakdown. The accumulation of interstitial fluid results in impaired solute exchange, leukocyte signaling, and aberrancy in capillary flow. Modulation of lymphatic flow during times of interstitial volume overload such as septic shock may decrease interstitial volume resulting in improved perfusion, decreased end-organ damage, and contribute to disease resolution. Multiple studies in both humans and animals have shown nitric oxide to be a potent modulator of lymphatic function. The present study suggests a hypothetical adjunct therapy for patients with septic shock through the use of phosphodiesterase inhibitors, which may improve microcirculatory flow by decreasing interstitial fluid volume via increased lymphatic fluid drainage.

Bedside prediction of intradialytic hemodynamic instability in critically ill patients: the SOCRATE study

BACKGROUND

Despite improvements in intermittent hemodialysis management, intradialytic hemodynamic instability (IHI) remains a common issue that could account for increased mortality and delayed renal recovery. However, predictive factors of IHI remain poorly explored. The objective of this study was to evaluate the relationship between baseline macrohemodynamic, tissue hypoperfusion parameters and IHI occurrence.

METHODS

Prospective observational study conducted in a 18-bed medical ICU of a tertiary teaching hospital. Cardiovascular SOFA score, index capillary refill time (CRT) and lactate level were measured just before (T0) consecutive intermittent hemodialysis sessions performed for AKI. The occurrence of IHI requiring a therapeutic intervention was recorded.

RESULTS

Two hundred eleven sessions, corresponding to 72 (34%) first sessions and 139 (66%) later sessions, were included. As IHI mostly occurred during first sessions (43% vs 12%, P < 0.0001), following analyses were performed on the 72 first sessions. At T0, cardiovascular SOFA score ≥1 (87% vs 51%, P = 0.0021) was more frequent before IHI sessions, as well as index CRT ≥ 3 s (55% vs 15%, P = 0.0004), and hyperlactatemia > 2 mmol/L (68% vs 29%, P = 0.0018). Moreover, the occurrence of IHI increased with the number of macrohemodynamic and tissue perfusion impaired parameters, named SOCRATE score (cardiovascular SOFA, index CRT and lactATE): 10% (95% CI [3%, 30%]), 33% (95% CI [15%, 58%]), 55% (95% CI [35%, 73%]) and 80% (95% CI [55%, 93%]) for 0, 1, 2 and 3 parameters, respectively (AUC = 0.79 [0.69-0.89], P < 0.0001). These results were confirmed by analyzing the 139 later sessions included in the study.

CONCLUSIONS

The SOCRATE score based on 3 easy-to-use bedside parameters correlates with the risk of IHI. By improving risk stratification of IHI, this score could help clinicians to manage intermittent hemodialysis initiation in critically ill AKI patients.

Is microcirculatory assessment ready for regular use in clinical practice?

PURPOSE OF REVIEW

The present review discusses the current role of microcirculatory assessment in the hemodynamic monitoring of critically ill patients.

RECENT FINDINGS

Videomicroscopic techniques have demonstrated that microvascular perfusion is altered in critically ill patients, and especially in sepsis. These alterations are associated with organ dysfunction and poor outcome. Handheld microscopes can easily be applied on the sublingual area of critically ill patients. Among the specific limitations of these techniques, the most important is that these can mostly investigate the sublingual microcirculation. The representativity of the sublingual area may be questioned, especially as some areas may sometimes be more affected than the sublingual area. Also, evaluation of the sublingual area may be difficult in nonintubated hypoxemic patients. Alternative techniques include vasoreactivity tests using either transient occlusion or performing a thermal challenge. These techniques evaluate the maximal dilatory properties of the microcirculation but do not really evaluate the actual microvascular perfusion. Focusing on the glycocalyx may be another option, especially with biomarkers of glycocalyx degradation and shedding. Evaluation of the glycocalyx is still largely experimental, with different tools still in investigation and lack of therapeutic target. Venoarterial differences in PCO2 are inversely related with microvascular perfusion, and can thus be used as surrogate for microcirculation assessment. Several limitations prevent the regular use in clinical practice. The first is the difficult use of some of these techniques outside research teams, whereas nurse-driven measurements are probably desired. The second important limitation for daily practice use is the lack of uniformly defined endpoint. The final limitation is that therapeutic interventions affecting the microcirculation are not straightforward.

SUMMARY

Clinical and biological surrogates of microcirculatory assessment can be used at bedside. The role of microvideoscopic techniques is still hampered by the lack of clearly defined targets as well as interventions specifically targeting the microcirculation.