Blood viscosity and circulatory shock

Machine learning-based model for predicting the esophagogastric variceal bleeding risk in liver cirrhosis patients

BACKGROUND

Liver cirrhosis patients are at risk for esophagogastric variceal bleeding (EGVB). Herein, we aimed to estimate the EGVB risk in patients with liver cirrhosis using an artificial neural network (ANN).

METHODS

We included 999 liver cirrhosis patients hospitalized at the Beijing Ditan Hospital, Capital Medical University in the training cohort and 101 patients from Shuguang Hospital in the validation cohort. The factors independently affecting EGVB occurrence were determined via univariate analysis and used to develop an ANN model.

RESULTS

The 1-year cumulative EGVB incidence rates were 11.9 and 11.9% in the training and validation groups, respectively. A total of 12 independent risk factors, including gender, drinking and smoking history, decompensation, ascites, location and size of varices, alanine aminotransferase (ALT), γ-glutamyl transferase (GGT), hematocrit (HCT) and neutrophil-lymphocyte ratio (NLR) levels as well as red blood cell (RBC) count were evaluated and used to establish the ANN model, which estimated the 1-year EGVB risk. The ANN model had an area under the curve (AUC) of 0.959, which was significantly higher than the AUC for the North Italian Endoscopic Club (NIEC) (0.669) and revised North Italian Endoscopic Club (Rev-NIEC) indices (0.725) (all P <  0.001). Decision curve analyses revealed improved net benefits of the ANN compared to the NIEC and Rev-NIEC indices.

CONCLUSIONS

The ANN model accurately predicted the 1-year risk for EGVB in liver cirrhosis patients and might be used as a basis for risk-based EGVB surveillance strategies.

A novel prognostic model for predicting the risk of first variceal hemorrhage in patients with HBV-related cirrhosis

Background

Variceal hemorrhage (VH) is a life-threatening complication of cirrhosis. An accurate VH risk evaluation is critical to determine appropriate prevention strategies. We aimed to develop an individualized prediction model to predict the risk of first VH in hepatitis B virus (HBV)-related cirrhotic patients.

Methods

A nomogram was developed based on a retrospective analysis of 527 consecutive HBV-related cirrhotic patients with gastroesophageal varices (GEVs). The nomogram evaluation was performed using the area under the receiver operating characteristic curve (AUC), concordance index (C-index), calibration plot, and decision curve analysis (DCA). The results were verified using an external cohort (n = 187).

Results

We developed a nomogram based on clinical and endoscopic features, including the size of varices, red wale marks, ascites, spleen thickness, γ-glutamyltransferase, and hematocrit. The C-index of the nomogram in the derivation and validation cohort was 0.806 and 0.820, respectively, and the calibration plot fitted well. Compared with those of the North Italian Endoscopic Club (NIEC) and revised NIEC indexes, the AUC (derivation cohort: 0.822 vs. 0.653 vs. 0.713; validation cohort: 0.846 vs. 0.685 vs. 0.747) and DCA curves of this nomogram were better. Further, based on the risk scores, patients were classified into low-, medium-, and high-risk groups, and significant differences were noted in VH incidence among the three risk groups (P <0.001 for each cohort).

Conclusions

An effective individualized nomogram to predict the risk of first VH in HBV-related GEV patients was established, which can assist clinicians in developing more appropriate prevention strategies.

The optimal hematocrit

Nearly 15 million units of packed red blood cells and whole blood are transfused annually in the United States alone. Until recently, the major risks from blood transfusion were thought to be transmission of viral infections, and overall, blood transfusion was believed by most providers to be safe. A safe hemoglobin threshold above which red cell transfusion is clearly unnecessary has not been established. This article addresses the numerous problems that surround the use and consequences of blood transfusion, such as hemoglobin and hematocrit levels, oxygenation, storage time, immunomodulation, infection, and anemia. The relevant literature is comprehensively reviewed.

Neuraminidase alters red blood cells in sepsis

OBJECTIVE

To investigate the influence of neuraminidase, an enzyme that cleaves sialic acid from the red blood cell (RBC) membrane, on RBC shape and biochemistry in critically ill patients.

DESIGN

Prospective, observational study and in vitro laboratory study.

SETTING

A 31-bed medico-surgical department of intensive care and a university-affiliated cell biology laboratory.

SUBJECTS

Acutely ill patients with and without sepsis and healthy volunteers.

INTERVENTIONS

Blood sampling in volunteers.

MEASUREMENTS AND MAIN RESULTS

Neuraminidase activity was measured using a fluorescent assay. RBC shape was assessed by the second coefficient of dissymmetry of Pearson using a flow cytometry technique at 25 degrees C. Intraerythrocytic 2,3-diphosphoglycerate and lactate contents were also measured. Neuraminidase activity was significantly higher in septic patients compared with nonseptic patients and healthy volunteers (5.42 [4.85-6.00] vs. 4.53 [4.23-5.23] and 1.26 [0.83-1.83] mU/mL; all p < 0.05). Neuraminidase treatment modified the RBC shape in vitro in a dose-response fashion, and most of these alterations were present after 10 hours of incubation. Incubation of RBCs with phosphatidylinositol phospholipase C modified RBC shape and increased sialic acid concentrations in the supernatant, suggesting a leakage of neuraminidase from the RBC membrane. Alterations in shape were associated with increased 2,3-diphosphoglycerate (0.46 +/- 0.25 vs. 0.19 +/- 0.05 mumol/mL; p = 0.006) and lactate content (0.81 +/- 0.07 vs. 0.66 +/- 0.05 mmoL/L; p = 0.002).

CONCLUSIONS

In sepsis, desialylation under the influence of increased neuraminidase activity may contribute to the alterations in RBC rheology. Inhibition of neuraminidase may represent a new therapeutic option to ameliorate RBC rheology and perhaps oxygen delivery to the cells.

Hemorheology in patients with liver cirrhosis: special emphasis on its relation to severity of esophageal variceal bleeding

BACKGROUND

Patients with decreased blood viscosity are supposed to have a higher risk of bleeding and increased severity of bleeding (severity of bleeding proportional to transmural pressure x area of variceal tear/blood viscosity). However, the hemorheological factors have never been assessed in patients with esophageal variceal bleeding. Therefore, the purpose of the present study was to examine the hemorheological factors in liver cirrhotic patients with special emphasis on the outcome of variceal bleeding.

METHODS

Forty-two liver cirrhosis patients with variceal bleeding and another 44 matched patients without bleeding were enrolled. The hemorheological and hemostatic factors of their peripheral blood were examined. The clinical course was under careful surveillance.

RESULTS

Patients with poor hepatic reserve (Child B + C vs A) had lower whole blood viscosity (4.34 +/- 0.56 mPa.s vs 5.06 +/- 1.35 mPa.s, P < 0.05), lower hematocrit levels (32.86 +/- 5.97% vs 36.62 +/- 5.44%, P < 0.05), lower platelet counts (79.7 +/- 47.6 x 10(3)/mL vs 108.0 +/- 71.2 x 10(3)/mL, P < 0.05) and prolonged prothrombin time (2.88 +/- 2.33 s vs 1.27 +/- 1.37 s, P < 0.05). Patients with bleeding (vs non-bleeding group) had lower hematocrit levels (31.44 +/- 5.75% vs 36.57 +/- 5.19%, P < 0.01) and lower fibrinogen levels (226.7 +/- 92.7 mg/dL vs 286.4 +/- 111.8 mg/dL, P < 0.05). Patients with bleeding with shock had worse liver cirrhosis (Child A/B/C = 0/5/4 vs 11/18/4, P < 0.05), lower whole blood viscosity (4.01 +/- 0.17 mPa.s vs 4.57 +/- 0.76 mPa.s, P < 0.05), reduced erythrocyte aggregability (2.94 +/- 0.41 vs 3.54 +/- 0.61, P < 0.001), and lower platelet counts (56.22 +/- 17.05 x 10(3)/mL vs 88.87 +/- 38.12 x 10(3)/mL, P < 0.001). The Child-Pugh grade and erythrocyte aggregability were two independent factors associated with bleeding shock.

CONCLUSIONS

Whole blood viscosity, hematocrit levels and platelet counts were lower in patients with advanced liver cirrhosis. Advanced liver cirrhosis and reduced erythrocyte aggregability were independent factors for hypovolemic shock in cirrhotic patients with esophageal variceal bleeding. However, the causal relationship between hemorheology and bleeding needs to be clarified in further studies.

Red blood cell rheology in sepsis

Changes in red blood cell (RBC) function can contribute to alterations in microcirculatory blood flow and cellular dysoxia in sepsis. Decreases in RBC and neutrophil deformability impair the passage of these cells through the microcirculation. While the role of leukocytes has been the focus of many studies in sepsis, the role of erythrocyte rheological alterations in this syndrome has only recently been investigated. RBC rheology can be influenced by many factors, including alterations in intracellular calcium and adenosine triphosphate (ATP) concentrations, the effects of nitric oxide, a decrease in some RBC membrane components such as sialic acid, and an increase in others such as 2,3 diphosphoglycerate. Other factors include interactions with white blood cells and their products (reactive oxygen species), or the effects of temperature variations. Understanding the mechanisms of altered RBC rheology in sepsis, and the effects on blood flow and oxygen transport, may lead to improved patient management and reductions in morbidity and mortality.

Sepsis/septic shock: participation of the microcirculation: an abbreviated review

OBJECTIVE

An overview of the importance of understanding mechanisms occurring in the microcirculation during septic and endotoxic shock. The thesis of the paper is to place emphasis on this important vascular network to ultimately benefit the patient.

DATA SOURCES

Early descriptions of vascular reactions to endotoxin which suggest that the microcirculation is a major site of attack during shock. More recent studies were sought out and examined as to their possible impacts on the microcirculation.

STUDY SELECTION

Early comprehensive studies concerning vascular reactions in the microcirculation during shock were selected. Subsequent studies identified from the mainstream scientific medical literature describe the actions of blood, cells, and the emerging significant role of the vascular endothelium among other factors. A consensus view is identified, pointing to the causes of a malfunctioning microcirculation during shock.

DATA EXTRACTION

Data gathered from reports in the mainstream, well-established basic and clinical literature, from reviews and forum reports, from studies by well-established investigators, and from more recent reports of excellent quality.

DATA SYNTHESIS

The microcirculation undergoes massive alterations during sepsis/septic shock. There are numerous changes, including slowing of capillary blood flow due to depressed perfusion pressure as a result of systemic pressure reduction and local arteriolar constriction. Observations suggest that the microcirculation is shut off early in severe sepsis, allowing the effects of hypoperfusion and attacks by microorganisms to prevail in their destructive capabilities. Widespread capillary dilation may ultimately occur. However, with blood flow diverted through some arteriovenous channels, important areas of capillary exchange are bypassed. Decreased capillary blood flow during shock results from failure to allow normal passage of cellular elements, including erythrocytes and neutrophils. This defect occurs, in part, because of decreased perfusion pressure, decreased deformability of red and white cells, constricted arterioles, circulating obstructive fragments (including hemoglobin), and plugging of microvessels with "sludge." Other factors are adherence of cells to capillary and venular epithelial membranes creating increased resistance to flow, loss of fluid through abnormal transcapillary exchange, differential vascular resistance changes between various beds (e.g., intestinal vs. muscle), and the relative absence of regulatory neurohumoral control of small vessel segments of the circulation. During sepsis/septic shock, endothelial cells are reported to modulate vascular tone, control local blood flow, influence the rate of leakage of fluids and plasma proteins into tissues, modulate the accumulation and extravasation of white cells into tissues, and influence white cell activation. As a result of the predominance of many destructive factors, a subsequent round of tissue damage may occur. Because of prolonged capillary vascular stasis, deficient flow, and factors released from injured cells, the microcirculation becomes a trap for uncontrolled bacterial growth enhanced by sustained hypoxemia, acidosis and toxemia. These events may combine to contribute to the loss of normal cell integrity and death of the host.

CONCLUSIONS

The purpose of this review is to draw the readers' attention to the growing list of adverse factors occurring in the microcirculation during sepsis/septic shock. A further aim is to point to the realization of the complexity of factors which may contribute to the importance of a well-functioning microcirculation.

Triage of critically ill patients: an overview of interventions

The recognition of tissue hypoxia or cumulative oxygen debt is of fundamental importance for triage and resuscitation of critically ill patients during the ¿golden hour¿ in the emergency department (ED). The measurement of central venous blood oxygen saturation, plasma lactate concentration, cardiac output, systemic oxygen transport and use, and non-vital organ oxygenation and function can enhance the detection of systemic and regional hypoperfusion and tissue hypoxia. Systemic and organ-specific oxygenation indices may guide the choice of therapy to optimize resuscitation of the macrocirculation and microcirculation in critically ill ED patients.

An argument for colloid resuscitation for shock

A focused review of the physiologic mechanisms of colloid and crystalloid fluid resuscitations for acute critical illness is presented. This review suggests that postresuscitation plasma volume, cardiac output, left ventricular mechanical performance, and global and microcirculatory O2 supplies are more favorable with colloid therapy. Conversely, crystalloid may adversely affect microcirculatory blood flow and resultant O2 supply and use by ischemic tissues in shock. Poor relief of global and regional hypoxia may persist in critically ill patients after resuscitation with crystalloid.

Evaluation, treatment, and transport of pediatric patients with shock

Early recognition and correct treatment of shock remain the most important keys to preventing the death and disability frequently caused by this condition in children. The pediatrician plays a vital role in this process and in referral of the patient for transport to tertiary care centers, where shock is best managed. The transport environment creates special challenges in initial stabilization and ongoing treatment of shock. Discussion centers on clinical clues to recognition, on simple measures available to increase tissue oxygenation, and on the issues of pretransport and transport treatment. Support of airway and breathing, vascular access, and correct fluid therapy remain the cornerstones of successful treatment.

Blood rheology in the endotoxin-administered rabbits

The effects of endotoxin on blood rheology were studied in rabbits. Non-treated six rabbits (Group A) were used to obtain control data. Thirteen rabbits who were administered 0.1 mg of endotoxin three times at intervals of 3 days were divided into two groups; seven rabbits (Group B) were injected with 1 ml saline solution as the vehicle for endotoxin at 7 days after the final administration of endotoxin, while the remaining six rabbits (Group C) were administered endotoxin at 0.2 mg/kg on the same day. Blood was sampled from the femoral artery 120 min after the final treatment. Blood viscosity was measured at a shear rate of 150 s-1 at 37 degrees C using a cone-plate viscometer. The passage time for a 5% red blood cell suspension and that for plasma were determined by filtration; the former represents erythrocyte deformability while the latter is related to plasma fluidity. The hematocrit, whole blood viscosity and erythrocyte deformability did not show significant differences among these three groups. The ratio of hematocrit to whole blood viscosity is considered to be an index of oxygen delivery from the hemorheologic point. This index did not show significant difference either. A good correlation was observed between whole blood viscosity and hematocrit in Group A, but not in the endotoxin-treated groups. The plasma fluidity was lower in Groups B and C than in Group A. These data indicate that plasma fluidity and the hematocrit-viscosity relationship are affected in endotoxin-treated rabbits, although blood viscosity, erythrocyte deformability and oxygen delivery hardly changed.

Relation between blood viscosity and hematocrit in rabbits subjected to repeated treatment with endotoxin

Blood rheology was studied in rabbits repeatedly treated with endotoxin at a dose of 0.1 mg administered 3 times, at intervals of 3 days. On the 7th day after the last endotoxin injection, blood was sampled 3 times from the femoral artery under anesthesia using pentobarbital sodium. Blood viscosity was determined at a shear rate of 150 s-1 at 37 degrees C using a cone-plate viscometer. Plasma fluidity was determined using the filtration method. Hematocrit and whole blood viscosity showed no significant differences between the untreated rabbits (Group A) and rabbits treated with endotoxin (Group B). Plasma fluidity was significantly lowered in Group B. Whole blood viscosity correlated well with hematocrit in Group A, but there was no correlation in Group B. The ratio of hematocrit to whole blood viscosity, which is considered to be the index of oxygen delivery from the blood rheological point of view, indicated no significant difference between the two groups. The optimal hematocrit to oxygen delivery, however, was higher in Group B than in Group A. These data suggest that the high hematocrit rather becomes an advantage to oxygen delivery in endotoxicosis because the hematocrit-viscosity relation is disturbed.