Acidosis induced by lactate, pyruvate, or HCl increases blood viscosity

The Effect of the Acid-Base Imbalance on the Shape and Structure of Red Blood Cells

Red blood cells respond to fluctuations in blood plasma pH by changing the rate of biochemical and physical processes that affect the specific functions of individual cells. This study aimed to analyze the effect of pH changes on red blood cell morphology and structure. The findings revealed that an increase or decrease in pH above or below the physiological level of pH 7.4 results in the transformation of discocytes into echinocytes and causes significant alterations in the membrane, including its roughness, cytoskeleton structure, and the cell's elastic modulus. Furthermore, the study shown a strong connection between critical acidosis and alkalosis with increased intracellular reactive oxygen species production.

Long-Term Maintenance of Normal Serum Vitamin B1 Levels Is Associated with Better Outcomes in Patients with Heart Failure

Deficiency of vitamin B1 (VB1), an essential micronutrient, causes heart failure (HF). A recent randomized controlled trial failed to show any improvement in HF prognosis after short-term VB1 supplementation. In the current study, we investigated the efficacy of long-term maintenance of normal blood VB1 levels in preventing adverse outcomes in patients with HF.This study included 88 consecutive patients with HF who received guideline-directed medical therapy at Arida Municipal Hospital. The patients were divided into 3 groups: a control group with normal VB1 levels and no VB1 supplementation (normal group, n = 25), and those presenting with VB1 deficiency, who either required short-term VB1 supplementation (short-term supplementation group, n = 25), or long-term maintenance of normal blood VB1 levels (long-term maintenance group, n = 38). The time to the first appearance of composite outcomes, including cardiovascular death and hospitalization for HF, was compared between the 3 groups.VB1 deficiency was observed in 63 (72%) patients. The Kaplan-Meier curve showed that the long-term maintenance group had better outcomes than the other 2 groups. In the multivariate analysis, long-term maintenance of normal blood VB1 levels and age were independent predictors of composite outcomes.VB1 deficiency is frequently observed, and the long-term maintenance of normal blood VB1 levels may result in better outcomes in patients with HF. Our results suggest that the detection of VB1 deficiency and long-term restoration of VB1 levels may be part of the overall therapeutic strategy for HF.

Hemorheological and Microcirculatory Relations of Acute Pancreatitis

Acute pancreatitis still means a serious challenge in clinical practice. Its pathomechanism is complex and has yet to be fully elucidated. Rheological properties of blood play an important role in tissue perfusion and show non-specific changes in acute pancreatitis. An increase in blood and plasma viscosity, impairment of red blood cell deformability, and enhanced red blood cell aggregation caused by metabolic, inflammatory, free radical-related changes and mechanical stress contribute to the deterioration of the blood flow in the large vessels and also in the microcirculation. Revealing the significance of these changes in acute pancreatitis may better explain the pathogenesis and optimize the therapy. In this review, we give an overview of the role of impaired microcirculation by changes in hemorheological properties in acute pancreatitis.

Alterations of Selected Hemorheological and Metabolic Parameters Induced by Physical Activity in Untrained Men and Sportsmen

Optimal tissue oxygen supply is essential for proper athletic performance and endurance. It also depends on perfusion, so on hemorheological properties and microcirculation. Regular exercise is beneficial to the rheological status, depending on its type, intensity, and duration. We aimed to investigate macro and microrheological changes due to short, high-intensity exercise in professional athletes (soccer and ice hockey players) and untrained individuals. The exercise was performed on a treadmill ergometer during a spiroergometry examination. Blood samples were taken before and after exercise to analyze lactate concentration, hematological parameters, blood and plasma viscosity, and red blood cell (RBC) deformability and aggregation. Leukocyte, RBC and platelet counts, and blood viscosity increased with exercise, by the largest magnitude in the untrained group. RBC deformability slightly impaired after exercise, but showed better values in ice hockey versus soccer players. RBC aggregation increased with exercise, dominantly in ice hockey players. Lactate increased mostly in soccer players, and the respiratory exchange rate was the lowest in ice hockey players. Overall, short, high-intensity exercise altered macro and microrheological parameters, mostly in the untrained group. Significant differences were found between the two sports. The data can be useful in training status monitoring, selection, and in revealing the causes of physical loading symptoms.

Hematological, Micro-Rheological, and Metabolic Changes Modulated by Local Ischemic Pre- and Post-Conditioning in Rat Limb Ischemia-Reperfusion

In trauma and orthopedic surgery, limb ischemia-reperfusion (I/R) remains a great challenge. The effect of preventive protocols, including surgical conditioning approaches, is still controversial. We aimed to examine the effects of local ischemic pre-conditioning (PreC) and post-conditioning (PostC) on limb I/R. Anesthetized rats were randomized into sham-operated (control), I/R (120-min limb ischemia with tourniquet), PreC, or PostC groups (3 × 10-min tourniquet ischemia, 10-min reperfusion intervals). Blood samples were taken before and just after the ischemia, and on the first postoperative week for testing hematological, micro-rheological (erythrocyte deformability and aggregation), and metabolic parameters. Histological samples were also taken. Erythrocyte count, hemoglobin, and hematocrit values decreased, while after a temporary decrease, platelet count increased in I/R groups. Erythrocyte deformability impairment and aggregation enhancement were seen after ischemia, more obviously in the PreC group, and less in PostC. Blood pH decreased in all I/R groups. The elevation of creatinine and lactate concentration was the largest in PostC group. Histology did not reveal important differences. In conclusion, limb I/R caused micro-rheological impairment with hematological and metabolic changes. Ischemic pre- and post-conditioning had additive changes in various manners. Post-conditioning showed better micro-rheological effects. However, by these parameters it cannot be decided which protocol is better.

Hemorheological and Microcirculatory Factors in Liver Ischemia-Reperfusion Injury-An Update on Pathophysiology, Molecular Mechanisms and Protective Strategies

Hepatic ischemia-reperfusion injury (IRI) is a multifactorial phenomenon which has been associated with adverse clinical outcomes. IRI related tissue damage is characterized by various chronological events depending on the experimental model or clinical setting. Despite the fact that IRI research has been in the spotlight of scientific interest for over three decades with a significant and continuous increase in publication activity over the years and the large number of pharmacological and surgical therapeutic attempts introduced, not many of these strategies have made their way into everyday clinical practice. Furthermore, the pathomechanism of hepatic IRI has not been fully elucidated yet. In the complex process of the IRI, flow properties of blood are not neglectable. Hemorheological factors play an important role in determining tissue perfusion and orchestrating mechanical shear stress-dependent endothelial functions. Antioxidant and anti-inflammatory agents, ischemic conditioning protocols, dynamic organ preservation techniques may improve rheological properties of the post-reperfusion hepatic blood flow and target endothelial cells, exerting a potent protection against hepatic IRI. In this review paper we give a comprehensive overview of microcirculatory, rheological and molecular–pathophysiological aspects of hepatic circulation in the context of IRI and hepatoprotective approaches.

Preventive measures for the critical postexercise period in sickle cell trait and disease

The immediate postexercise/physical activity period is critical for sickle cell trait (SCT) carriers and disease (SCD) patients. Exercise-related blood acidosis is known to trigger the cascade of HbS deoxygenation and polymerization, leading to red blood cell sickling and subsequent complications. Unfortunately, two facts worsen exercise-related blood acidosis during the initial postexercise period: First, blood lactate and H⁺ concentrations continue to increase for several minutes after exercise completion, exacerbating blood acidosis. Second, blood lactate concentration remains elevated and pH altered for 20-45 min during inactivity after intense exercise, keeping acid/base balance disturbed for a long period after exercise. Therefore, the risk of complications (including vasoocclusive crises and even sudden death) persists and even worsens several minutes after intense exercise completion in SCT carriers or SCD patients. Light physical activity following intense exercise (namely, active recovery) may, by accelerating lactate removal and acid/base balance restoration, reduce the risk of complications. Scientific evidence suggests that light exercise at or below the first lactate threshold is an appropriate strategy.

Erythrocytes as Biomarkers for Dementia: Analysis of Protein Content and Alpha-Synuclein

BACKGROUND

Discovering biomarkers for dementia is a pivotal step toward successful early diagnosis and treatment. Although plasma biomarkers have been explored, no consensus has been reached. Alpha-synuclein (AS), a 14 kDa synaptic protein associated with several neurodegenerative diseases, exists natively within erythrocytes (ERC). This protein is characteristic of Lewy body diseases, in which it aggregates into toxic Lewy bodies. As ERC are implicated in dementia, they are a potential target for future biomarkers.

OBJECTIVE

The aims of this study were to assess AS levels within ERC and whether AS can be used as a peripheral biomarker to differentiate between dementia and aged matched healthy control subjects.

METHODS

A total of 114 samples (60 aging controls, 36 Alzheimer's disease, 12 vascular dementia (VaD) and 6 dementia with Lewy bodies (DLB) subjects) were analyzed. We used Bradford assay to measure protein concentration, indirect ELISA to detect levels of AS, and immunoblotting to identify AS composition. Data were analyzed with nonparametric tests.

RESULTS

AS oligomers were present in dementia blood samples, whereas in controls, AS was largely monomeric. There was a significant increase in AS levels in DLB whole blood (p = 0.005; Kruskal-Wallis test), with a sensitivity and specificity of 100.0% and 93.9%. Protein concentrations in ERC isolated at pH 5.7 were significantly increased in dementia patients compared to controls (17.58 versus 40.33μg/ml; p≤0.005; Mann-Whitney test). In the VaD group, the protein concentration in the pH5.7 ERC fraction had sensitivity and specificity of 91.7% and 62.1%.

CONCLUSIONS

ERC protein concentration and AS levels have a potential for development of a novel diagnostic dementia blood test.

Age- and gender-related hemorheological alterations in intestinal ischemia-reperfusion in the rat

BACKGROUND

Intestinal ischemia-reperfusion (I/R) is a life-threatening clinical disorder. During I/R, the microrheological parameters of blood (red blood cell deformability and aggregation) worsen, which may contribute to microcirculatory deterioration. Age and gender also have a great influence on hemorheological parameters. We aimed to investigate the gender and age-related microrheological alterations during intestinal I/R.

MATERIALS AND METHODS

After the cannulation of the left femoral artery, median laparotomy was performed in Crl:WI rats under general anesthesia. In the young control animals there were no other interventions (female n = 7; male n = 7). In the young (female n = 7; male n = 7) and older I/R groups (female n = 6; male n = 6), the superior mesenteric artery was clipped for 30 min, and a 120-min reperfusion period was observed afterward. Blood samples were taken before and at the 30-min ischemia, in the 30th, 60th, and 120th min of the reperfusion. Hematological parameters, erythrocyte deformability, and aggregation were determined.

RESULTS

Hematocrit increased significantly in the younger female I/R group. Red blood cell count was higher in male and older animals. In case of white blood cell count, male animals had higher values compared with females. Platelet count elevated in the younger male and older female I/R animals. Red blood cell deformability worsened, mainly in the male and older I/R groups. Enhanced erythrocyte aggregation was seen in all groups, being more expressed in the female I/R groups.

CONCLUSIONS

Microrheological parameters show gender and age-related differences during intestinal I/R. These observations have importance in the planning and evaluation of experimental data.

Exercise-induced blood lactate increase does not change red blood cell deformability in cyclists

BACKGROUND

The effect of exercise-induced lactate production on red blood cell deformability and other blood rheological changes is controversial, given heavy-exercise induces biochemical processes (e.g., oxidative stress) known to perturb haemorheology. The aim of the present study was to examine the haemorheological response to a short-duration cycling protocol designed to increase blood lactate concentration, but of duration insufficient to induce significant oxidative stress.

METHODS

Male cyclists and triathletes (n = 6; 27±7 yr; body mass index: 23.7±3.0 kg/m²; peak oxygen uptake 4.02±0.51 L/min) performed unloaded (0 W), moderate-intensity, and heavy-intensity cycling. Blood was sampled at rest and during the final minute of each cycling bout. Blood chemistry, blood viscosity, red blood cell aggregation and red blood cell deformability were measured.

RESULTS

Blood lactate concentration increased significantly during heavy-intensity cycling, when compared with all other conditions. Methaemoglobin fraction did not change during any exercise bout when compared with rest. Blood viscosity at native haematocrit increased during heavy-intensity cycling at higher-shear rates when compared with rest, unloaded and moderate-intensity cycling. Heavy-intensity exercise increased the amplitude of red blood cell aggregation in native haematocrit samples when compared with all other conditions. Red blood cell deformability was not changed by exercise.

CONCLUSION

Acute exercise perturbs haemorheology in an intensity dose-response fashion; however, many of the haemorheological effects appear to be secondary to haemoconcentration, rather than increased lactate concentration.

Adverse influence of mixed acidemia on the biocompatibility of continuous veno-venous hemofiltration with respect to the lungs

Experimental data indicate that hypercapnic adidosis has anti-inflammatory effects. These anti-inflammatory effects may even be a beneficial property in case of low tidal volume ventilation with consecutive hypercapnic acidosis. It is unclear whether these anti-inflammatory effects predominate in critically ill patients who suffer from multiple pro- and anti-inflammatory insults like extracorporeal organ support (pro-inflammatory), metabolic acidosis (pro- and anti-inflammatory), as well as hypoxia (pro-inflammatory). Eighteen pigs were randomized into three groups, mechanically ventilated and connected to a continuous veno-venous hemofiltration (CVVH) as pro-inflammatory insult. A reference group with normal acid-base state obtained normoventilation; a normoxemic acidemia group obtained normoxemic, mixed acidemia due to infusion of lactic and hyperchloremic acid and low tidal volume ventilation, and in a hypoxemic acidemia group the mixed acidemia was paralleled by hypoxemia. Lung histology including pulmonary leukocyte invasion, blood gases, blood cell counts, and hemodynamics were examined. The histological examination of the lungs of acidemic pigs showed a suppressed invasion of leukocytes and thinner alveolar walls compared with normoventilated and with hypoxemic pigs. Enhanced congestion and alveolar red blood cells (RBCs) combined with an increase of the pulmonary artery pressure were observed in acidemic pigs in comparison with the reference group. Normoxemic acidemia reduced the pro-inflammatory reaction to the CVVH and mechanical ventilation in the ventilated lung areas in the form of pulmonary leukocyte invasion. However, this did not result in reduced scores for lung injury. Instead, an increased score for criteria which represent lung injury (congestion and alveolar RBCs) was observed in acidemic pigs.

Intravenous injection of mesenteric lymph produced during hemorrhagic shock decreases RBC deformability in the rat

OBJECTIVE

To test the hypothesis that gut-derived factors carried in trauma-hemorrhagic shock (T/HS) lymph are sufficient to induce red blood cells (RBC) injury, to investigate their potential mechanisms of action, and to define the time post-T/HS that these factors appear in the lymph.

METHODS

Mesenteric lymph collected from T/HS or trauma-sham shock (T/SS) rats over different time periods was injected intravenously into male rats at a rate of 1 mL/h for 3 hours. RBC deformability was measured using laser-assisted ektacytometer to calculate the elongation index. From the shear-stress elongation curve, the stress required for the erythrocytes to reach 50% of their maximal elongation was also determined. RBC deformability was measured before lymph infusion and at 1 hour and 3 hours after the initiation of lymph infusion. The effect of the lymph samples (5% v/v) was also determined in vitro by incubating naïve whole blood with the lymph samples. The potential role of T/HS lymph-induced RBC oxidant injury mediated by inducible nitric oxide synthase (iNOS)-generated oxidants and/or white blood cells (WBC) was investigated using iNOS inhibitors and WBC depletion, respectively. In all the in vivo studies, five to seven rats were studied per group.

RESULTS

The intravenous injection of T/HS lymph but not T/SS lymph caused in vivo RBC injury. The biological activity of T/HS lymph varied over time with the RBC-injurious factors being produced only during the first 3 hours postshock. The in vivo inhibition of iNOS did not prevent lymph-induced RBC injury. T/HS lymph incubated in vitro with naïve whole blood resulted in RBC injury, but this injury was not observed in blood depleted of WBC.

CONCLUSIONS

These results indicate that T/HS lymph produced during the initial 3-hour postshock period is sufficient to induce RBC injury in otherwise normal rats and that the lymph-induced RBC injury is not dependent on activation of the iNOS pathway but seems to require WBC.

Postischemic treatment with ethyl pyruvate prevents adenosine triphosphate depletion, ameliorates inflammation, and decreases thrombosis in a murine model of hind-limb ischemia and reperfusion

INTRODUCTION

Experiments were designed to investigate the effects of ethyl pyruvate (EP) in a murine model of hind-limb ischemia-reperfusion (IR) injury.

METHODS

C57BL6 mice underwent 90 minutes of unilateral ischemia followed by 24 hours of reperfusion using two treatment protocols. For the preischemic treatment (pre-I) protocol, mice (n=6) were given 300 mg/kg EP before ischemia, followed by 150 mg/kg of EP just before reperfusion and at 6 hours and 12 hours after reperfusion. In a postischemic treatment (post-I) protocol, mice (n=7) were treated with 300 mg/kg EP at the end of the ischemic period, then 15 minutes later, and 2 hours after reperfusion and 150 mg/kg of EP at 4 hours, 6 hours, 10 hours, 16 hours, and 22 hours after reperfusion. Controls mice for both protocols were treated with lactated Ringers alone at time intervals identical to EP. Skeletal muscle levels of adenosine triphosphate (ATP), interleukin-1β, keratinocyte chemoattractant protein, and thrombin antithrombin-3 complex were measured. Skeletal muscle architectural integrity was assessed microscopically.

RESULTS

ATP levels were higher in mice treated with EP compared with controls under the both treatment protocols (p=0.02). Interleukin-1β, keratinocyte chemoattractant protein, thrombin antithrombin-3 complex (p<0.05), and the percentage of injured fibers (p<0.0001) were significantly decreased in treated versus control mice under the both protocols.

CONCLUSION

Muscle fiber injury and markers of tissue thrombosis and inflammation were reduced, and ATP was preserved with EP in pre-I and post-I protocols. Further investigation of the efficacy of EP to modulate IR injury in a larger animal model of IR injury is warranted.

Competition of pyruvate with physiological substrates for oxidation by the heart: implications for studies with hyperpolarized [1-13C]pyruvate

Carbon 13 nuclear magnetic resonance (NMR) isotopomer analysis was used to measure the rates of oxidation of long-chain fatty acids, ketones, and pyruvate to determine the minimum pyruvate concentration ([pyruvate]) needed to suppress oxidation of these alternative substrates. Substrate mixtures were chosen to represent either the fed or fasted state. At physiological [pyruvate], fatty acids and ketones supplied the overwhelming majority of acetyl-CoA. Under conditions mimicking the fed state, 3 mM pyruvate provided approximately 80% of acetyl-CoA, but under fasting conditions 6 mM pyruvate contributed only 33% of acetyl-CoA. Higher [pyruvate], 10-25 mM, was associated with transient reduced cardiac output, but overall hemodynamic performance was unchanged after equilibration. These observations suggested that 3-6 mM pyruvate in the coronary arteries would be an appropriate target for studies with hyperpolarized [1-(13)C]pyruvate. However, the metabolic products of 3 mM hyperpolarized [1-(13)C]pyruvate could not be detected in the isolated heart during perfusion with a physiological mixture of substrates including 3% albumin. In the presence of albumin even at high concentrations of pyruvate, 20 mM, hyperpolarized H(13)CO(3)(-) could be detected only in the absence of competing substrates. Highly purified albumin (but not albumin from plasma) substantially reduced the longitudinal relaxation time of [1-(13)C]pyruvate. In conclusion, studies of cardiac metabolism using hyperpolarized [1-(13)C]pyruvate are sensitive to the effects of competing substrates on pyruvate oxidation.

Acid–base and electrolyte analysis in critically ill patients: are we ready for the new millennium?

PURPOSE OF REVIEW

Disorders of acid-base and electrolytes are commonly seen in critically ill patients. The presence of these disorders typically signals the development of an underlying pathology. These disturbances can be severe and are often associated with worse outcome. Indeed, metabolic acidosis is one of the ways we quantify organ failure. Although acid-base and electrolyte disorders may be a result of the underlying pathophysiology (eg, renal failure, respiratory failure, shock), they may also result from the way in which we manage critically ill patients.

RECENT FINDINGS

The application of the physical-chemical approach to acid-base analysis has led to recent developments in the identification and quantification and understanding of mechanisms for acid-base disorders commonly found in critically ill patients. Examples include a better understanding of the role of electrolytes (especially sodium and chloride) and weak acids in the pathophysiology of acid-base disorders, the implication of acid-base derangements on the inflammatory process and organ perfusion, and the importance of resuscitation fluid composition.

SUMMARY

By adopting a physical-chemical approach to acid-base analysis we are gaining insight to the complexities of acid-base disorders and how their treatments may affect outcome.