Catecholamine regulation of local lactate production in vivo in skeletal muscle and adipose tissue: role of -adrenoreceptor subtypes

Is ultrafiltration volume a predictor of postoperative acute kidney injury in patients undergoing cardiopulmonary bypass?

INTRODUCTION

Intraoperative ultrafiltration (UF) is a procedure used during cardiopulmonary bypass (CPB) to reduce haemodilution and prevent excessive blood transfusion. However, the effect of UF volume on acute kidney injury (AKI) is not well established, and the results are conflicting. Additionally, there are no set indications for applying UF during CPB.

METHODS

This retrospective study analysed 641 patients who underwent coronary artery bypass graft (CABG) surgery with CPB. Perioperative parameters were extracted from the patients' records, and the UF volume was recorded. Acute Kidney Injury Network classification was used to define AKI. Univariable and multivariable logistic regression models were used to predict AKI while controlling for confounding factors.

RESULTS

The study enrolled patients with a mean age of 58.8 ± 11.1 years, 39.2% of whom were female. AKI occurred in 22.5% of patients, with 16.1% (103) experiencing stage I and 6.4% (41) experiencing stage II. The results showed a significant association between UF volume and the risk of developing AKI, with higher UF volumes associated with a higher risk of AKI. In the multivariable analysis, the other predictors of AKI included age, lowest mean arterial pressure (MAP), and red blood cell (RBC) transfusion during CPB.

CONCLUSION

The predictors of postoperative AKI in coronary CABG patients were the volume of UF, age, MAP, and blood transfusion during CPB.

The role of lactate in cardiovascular diseases

Cardiovascular diseases pose a major threat worldwide. Common cardiovascular diseases include acute myocardial infarction (AMI), heart failure, atrial fibrillation (AF) and atherosclerosis. Glycolysis process often has changed during these cardiovascular diseases. Lactate, the end-product of glycolysis, has been overlooked in the past but has gradually been identified to play major biological functions in recent years. Similarly, the role of lactate in cardiovascular disease is gradually being recognized. Targeting lactate production, regulating lactate transport, and modulating circulating lactate levels may serve as potential strategies for the treatment of cardiovascular diseases in the future. The purpose of this review is to integrate relevant clinical and basic research on the role of lactate in the pathophysiological process of cardiovascular disease in recent years to clarify the important role of lactate in cardiovascular disease and to guide further studies exploring the role of lactate in cardiovascular and other diseases. Video Abstract.

Alterations to Kidney Physiology during Cardiopulmonary Bypass-A Narrative Review of the Literature and Practical Remarks

INTRODUCTION

According to different authors, cardiac surgery-associated acute kidney injury (CSA-AKI) incidence can be as high as 20-50%. This complication increases postoperative morbidity and mortality and impairs long-term kidney function in some patients. This review aims to summarize current knowledge regarding alterations to renal physiology during cardiopulmonary bypass (CPB) and to discuss possible nephroprotective strategies for cardiac surgeries. Relevant sections: Systemic and renal circulation, Vasoactive drugs, Fluid balance and Osmotic regulation and Inflammatory response.

CONCLUSIONS

Considering the available scientific evidence, it is concluded that adequate kidney perfusion and fluid balance are the most critical factors determining postoperative kidney function. By adequate perfusion, one should understand perfusion with proper oxygen delivery and sufficient perfusion pressure. Maintaining the fluid balance is imperative for a normal kidney filtration process, which is essential for preserving the intra- and postoperative kidney function.

FUTURE DIRECTIONS

The review of the available literature regarding kidney function during cardiac surgery revealed a need for a more holistic approach to this subject.

Impact of acute stress on murine metabolomics and metabolic flux

Plasma metabolite concentrations and labeling enrichments are common measures of organismal metabolism. In mice, blood is often collected by tail snip sampling. Here, we systematically examined the effect of such sampling, relative to gold-standard sampling from an in-dwelling arterial catheter, on plasma metabolomics and stable isotope tracing. We find marked differences between the arterial and tail circulating metabolome, which arise from two major factors: handling stress and sampling site, whose effects were deconvoluted by taking a second arterial sample immediately after tail snip. Pyruvate and lactate were the most stress-sensitive plasma metabolites, rising ~14 and ~5-fold. Both acute handling stress and adrenergic agonists induce extensive, immediate production of lactate, and modest production of many other circulating metabolites, and we provide a reference set of mouse circulatory turnover fluxes with noninvasive arterial sampling to avoid such artifacts. Even in the absence of stress, lactate remains the highest flux circulating metabolite on a molar basis, and most glucose flux into the TCA cycle in fasted mice flows through circulating lactate. Thus, lactate is both a central player in unstressed mammalian metabolism and strongly produced in response to acute stress.

The principle of 'brain energy on demand' and its predictive power for stress, sleep, stroke, obesity and diabetes

Does the brain actively draw energy from the body when needed? There are different schools of thought regarding energy metabolism. In this study, the various theoretical models are classified into one of two categories: (1) conceptualizations of the brain as being purely passively supplied, which we call 'P-models,' and (2) models understanding the brain as not only passively receiving energy but also actively procuring energy for itself on demand, which we call 'A-models.' One prominent example of such theories making use of an A-model is the selfish-brain theory. The ability to make predictions was compared between the A- and P-models. A-models were able to predict and coherently explain all data examined, which included stress, sleep, caloric restriction, stroke, type-1-diabetes mellitus, obesity, and type-2-diabetes, whereas the predictions of P-models failed in most cases. The strength of the evidence supporting A-models is based on the coherence of accurate predictions across a spectrum of metabolic states. The theory test conducted here speaks to a brain that pulls its energy from the body on-demand.

Insulin-stimulated adipocytes secrete lactate to promote endothelial fatty acid uptake and transport

Insulin stimulates adipose tissue to extract fatty acids from circulation and sequester them inside adipose cells. How fatty acids are transported across the capillary endothelial barrier, and how this process is regulated, remains unclear. We modeled the relationship of adipocytes and endothelial cells in vitro to test the role of insulin in fatty acid transport. Treatment of endothelial cells with insulin did not affect endothelial fatty acid uptake, but endothelial cells took up more fatty acids when exposed to medium conditioned by adipocytes treated with insulin. Manipulations of this conditioned medium indicated that the secreted factor is a small, hydrophilic, non-proteinaceous metabolite. Factor activity was correlated with lactate concentration, and inhibition of lactate production in adipocytes abolished the activity. Finally, lactate alone was sufficient to increase endothelial uptake of both free fatty acids and lipids liberated from chylomicrons, and to promote transendothelial transport, at physiologically relevant concentrations. Taken together, these data suggest that insulin drives adipocytes to secrete lactate, which then acts in a paracrine fashion to promote fatty acid uptake and transport across the neighboring endothelial barrier.

Fetoscopic insufflation of heated-humidified carbon dioxide during simulated spina bifida repair is safe under controlled anesthesia in the fetal lamb

OBJECTIVE

To assess the safety of Partial-Amniotic-Insufflation-of-heated-humidified-CO₂ (hPACI) during fetoscopic spina bifida repair (fSB-repair).

METHOD

A simulated fSB-repair through an exteriorized uterus under hPACI was performed in 100-day fetal lambs (term = 145 days) under a laboratory anesthesia protocol (n = 5; group 1) which is known to induce maternal-fetal acidosis and hypercapnia. Since these may not occur clinically, we applied a clinical anesthesia protocol (n = 5; group 2), keeping maternal parameters within physiological conditions, that is, controlled maternal arterial carbon dioxide (CO2) pressure (pCO₂  = 30 mmHg), blood pressure (≥67 mmHg), and temperature (37.1-39.8°C). Our superiority study used fetal pH as the primary outcome.

RESULTS

Compared to group 1, controlled anesthesia normalized fetal pH (7.23 ± 0.02 vs. 7.36 ± 0.02, p < 0.001), pCO₂ (70.0 ± 9.1 vs. 43.0 ± 1.0 mmHg, p = 0.011) and bicarbonate (27.8 ± 1.1 vs. 24.0 ± 0.9 mmol/L, p = 0.071) at baseline. It kept them within clinically acceptable limits (pH ≥ 7.23, pCO₂  ≤ 70 mmHg, bicarbonate ≤ 30 mm/L) for ≥120 min of hPACI as opposed to ≤30 min in group one. Fetal pO₂ and lactate were comparable between groups and generally within normal range. Fetal brain histology demonstrated fewer apoptotic cells and higher neuronal density in the prefrontal cortex in group two. There was no difference in fetal membrane inflammation, which was mild.

CONCLUSION

Fetoscopic insufflation of heated-humidified CO₂ during simulated fSB-repair through an exteriorized uterus can be done safely under controlled anesthesia.

Effects of dexmedetomidine, propofol, sevoflurane and S-ketamine on the human metabolome: A randomised trial using nuclear magnetic resonance spectroscopy

BACKGROUND

Pharmacometabolomics uses large-scale data capturing methods to uncover drug-induced shifts in the metabolic profile. The specific effects of anaesthetics on the human metabolome are largely unknown.

OBJECTIVE

We aimed to discover whether exposure to routinely used anaesthetics have an acute effect on the human metabolic profile.

DESIGN

Randomised, open-label, controlled, parallel group, phase IV clinical drug trial.

SETTING

The study was conducted at Turku PET Centre, University of Turku, Finland, 2016 to 2017.

PARTICIPANTS

One hundred and sixty healthy male volunteers were recruited. The metabolomic data of 159 were evaluable.

INTERVENTIONS

Volunteers were randomised to receive a 1-h exposure to equipotent doses (EC50 for verbal command) of dexmedetomidine (1.5 ng ml-1; n = 40), propofol (1.7 μg ml-1; n = 40), sevoflurane (0.9% end-tidal; n = 39), S-ketamine (0.75 μg ml-1; n = 20) or placebo (n = 20).

MAIN OUTCOME MEASURES

Metabolite subgroups of apolipoproteins and lipoproteins, cholesterol, glycerides and phospholipids, fatty acids, glycolysis, amino acids, ketone bodies, creatinine and albumin and the inflammatory marker GlycA, were analysed with nuclear magnetic resonance spectroscopy from arterial blood samples collected at baseline, after anaesthetic administration and 70 min postanaesthesia.

RESULTS

All metabolite subgroups were affected. Statistically significant changes vs. placebo were observed in 11.0, 41.3, 0.65 and 3.9% of the 155 analytes in the dexmedetomidine, propofol, sevoflurane and S-ketamine groups, respectively. Dexmedetomidine increased glucose, decreased ketone bodies and affected lipoproteins and apolipoproteins. Propofol altered lipoproteins, fatty acids, glycerides and phospholipids and slightly increased inflammatory marker glycoprotein acetylation. Sevoflurane was relatively inert. S-ketamine increased glucose and lactate, whereas branched chain amino acids and tyrosine decreased.

CONCLUSION

A 1-h exposure to moderate doses of routinely used anaesthetics led to significant and characteristic alterations in the metabolic profile. Dexmedetomidine-induced alterations mirror α2-adrenoceptor agonism. Propofol emulsion altered the lipid profile. The inertness of sevoflurane might prove useful in vulnerable patients. S-ketamine induced amino acid alterations might be linked to its suggested antidepressive properties.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02624401. URL: https://clinicaltrials.gov/ct2/show/NCT02624401.

Effectiveness of enteral ivabradine for heart rate control in septic shock: A randomised controlled trial

Persistent tachycardia in patients with septic shock predicts poor outcome. This study sought to investigate the effect of the cardiac pacemaker current inhibitor ivabradine on heart rate and cardio-circulatory function in patients with septic shock. After informed consent, 60 patients with septic shock and persistent tachycardia (heart rate >95 /minute) were prospectively randomly assigned to receive either standard therapy for septic shock (group S) or standard therapy along with enteral ivabradine (group I) for the initial 96 hours after enrolment. Primary outcome was the difference in heart rate between the two groups during the first 96 hours. Secondary outcomes included the effect of ivabradine on haemodynamic, oxygenation, myocardial function and organ function parameters, incidence of adverse events and 30-day overall survival. Heart rate was lower in group I compared to group S (median difference in area under the curve -25.6 (95% confidence intervals -31.4 to -15.9) /minute; P <0.001). Vasopressor requirements, blood lactate levels, Sequential Organ Failure Assessment scores and E/e' ratio were lower in group I compared to group S. Stroke volume index and ejection fraction were higher in group I while cardiac index and oxygen delivery parameters were maintained similar to group S. There was no difference in 30-day mortality or in the incidence of serious adverse events. Enteral ivabradine is effective in reducing heart rate, and improving haemodynamic parameters and cardiac function in patients with septic shock and persistent tachycardia, without increasing the incidence of adverse events.

Effects of Short-Term Golden Root Extract (Rhodiola rosea) Supplementation on Resistance Exercise Performance

The purpose of this study was to examine the effects of short-term Golden Root Extract (GRE; Rhodiola rosea) supplementation on blood lactate, catecholamines, and performance during repeated bench press exercise. Resistance-trained males (n = 10) participated in this study. In a double-blinded, crossover, counterbalanced study design, participants supplemented with either 1500 mg/day of GRE or placebo (PL; gluten-free cornstarch) for 3 days prior to experimentation. An additional 500 mg dose was ingested 30 min prior to exercise testing. During each exercise trial, participants completed 2 repetitions of bench press at 75% of one-repetition maximum (1RM) as explosively as possible. A linear position transducer was used to measure mean concentric velocity. After 5 min of rest, participants completed 3 sets × repetitions to failure (RTF) at 75% 1RM separated by 2 min of rest between each set. A capillary blood sample was obtained pre- (PRE) and immediately post- (POST) exercise to measure blood concentrations lactate (LA), epinephrine (EPI), and norepinephrine (NE). Mean concentric velocity was significantly higher with GRE when compared to PL (p = 0.046). However, total RTF were significantly lower with GRE versus PL (p < 0.001). Regardless of treatment, LA was significantly higher Post versus Pre (p < 0.001), but GRE resulted in greater Post values compared to PL (p = 0.049). EPI and NE increased in both conditions Pre to Post (p < 0.001). However, Pre NE was significantly higher with GRE versus PL (p = 0.008). Findings indicate that short-term GRE supplementation increases mean bench press velocity but decreases bench press repetition volume. Furthermore, GRE resulted in higher NE levels and blood lactate following exercise. Thus, supplementing with GRE may enhance explosive resistance training performance but may also impair upper body strength-endurance.

Irs2 deficiency alters hippocampus-associated behaviors during young adulthood

Type 2 diabetes mellitus (T2DM), characterized by hyperglycemia and insulin resistance, has been recognized as a risk factor for cognitive impairment and dementia, including Alzheimer's disease (AD). Insulin receptor substrate2 (IRS2) is a major component of the insulin/insulin-like growth factor-1 signaling pathway. Irs2 deletion leads to life-threatening T2DM, promoting premature death in male mice regardless of their genetic background. Here, we showed for the first time that young adult male mice lacking Irs2 on a C57BL/6J genetic background (Irs2^-/-/6J) survived in different experimental environments and displayed hippocampus-associated behavioral alterations. Young adult male Irs2^-/-/6J mice also exhibit aberrant alterations in energy and nutrient sensors, such as AMP-activated protein kinase (AMPK) and glucose transporter3 (GLUT3), and reduced core body temperature accompanied by abnormal change in the temperature sensor in the brain. These results suggest that Irs2 deficiency-induced impairments of brain energy metabolism and thermoregulation contribute to hippocampus-associated behavioral changes in young adult male mice.

Cardiopulmonary effects of an intravenous infusion of fentanyl in cats during isoflurane anesthesia and with concurrent acepromazine or dexmedetomidine administration during anesthetic recovery

OBJECTIVE

To determine the cardiopulmonary effects of IV administration of fentanyl to cats anesthetized with isoflurane and during anesthetic recovery with concurrent administration of acepromazine or dexmedetomidine.

ANIMALS

6 healthy adult cats.

PROCEDURES

Cats received an IV bolus (5 μg/kg) followed by an IV infusion (5 μg/kg/h) of fentanyl for 120 minutes during isoflurane anesthesia and for 30 minutes after discontinuing isoflurane. Cats were randomly assigned in a crossover study to receive acepromazine (0.05 mg/kg) or dexmedetomidine (2.5 μg/kg), IV, when isoflurane was discontinued. Cardiopulmonary data were obtained during anesthesia and for 30 minutes during the anesthetic recovery period.

RESULTS

The administration of fentanyl during isoflurane anesthesia resulted in a transient increase in arterial blood pressure, mean pulmonary artery pressure, and oxygen delivery. Compared with values during isoflurane anesthesia, administration of dexmedetomidine during anesthetic recovery resulted in significant decreases in cardiac index, stroke index, and oxygen delivery and significant increases in arterial, central venous, and mean pulmonary artery pressures; systemic vascular resistance index; and oxygen extraction ratio. Administration of acepromazine resulted in increases in heart rate, cardiac index, oxygen uptake, and oxygen extraction ratio. Oxygen extraction ratio did not differ between acepromazine and dexmedetomidine.

CONCLUSIONS AND CLINICAL RELEVANCE

Fentanyl transiently improved indices of cardiopulmonary performance when administered to healthy cats anesthetized with isoflurane. The cardiovascular effects of acepromazine and dexmedetomidine in healthy cats receiving fentanyl during recovery from isoflurane anesthesia differed, but measured cardiopulmonary parameters remained within acceptable limits.

Functional Autoreactive Anti-β2 Adrenergic Antibodies May Contribute to Insulin Resistance Profile in Patients with Chronic Chagas Disease

Potential activation of β2 adrenergic receptors (β2AR) by specific autoreactive antibodies (Abs) that arise during the host reaction to Trypanosoma cruzi, could contribute to the elevated prevalence of metabolic disturbances described in patients with chronic Chagas disease (CCD). This study aimed to determine the prevalence of anti-β2AR Abs in patients with CCD, as well as the correlation of these Abs with the presence of glucose and lipid metabolism disturbances, in order to explore their association with an insulin resistance profile. Additionally, we tested the functional effects of anti-β2AR Abs employing an in vitro bioassay with neuroendocrine cells expressing β2AR. A clinical and metabolic evaluation including an OGTT was performed in 80 CCD patients and 40 controls. Anti-β2AR Abs were measured by an in-house-developed ELISA, and the β2 adrenergic activity of affinity-purified IgG fractions from patient’ sera were assayed in CRE-Luc and POMCLuc transfected AtT-20 cells. A higher proportion of dysglycemia (72.5% vs. 37.5%; p = 0.001) was observed in the CCD group, accompanied by increased HOMA2-IR (p = 0.019), especially in subjects with Abs (+). Anti-β2AR Abs reactivity (7.01 (2.39–20.5); p = 0.0004) and age >50 years (3.83 (1.30–11.25); p = 0.014) resulted as relevant for IR prediction (AUC: 0.786). Concordantly, Abs (+) CCD patients showed elevated metabolic risk scores and an increased prevalence of atherogenic dyslipidemia (p = 0.040), as compared to Abs (−) patients and controls. On functional bioassays, Abs exerted specific and dose-dependent β2-agonist effects. Our findings suggest that anti-β2AR Abs may induce the activation of β2AR in other tissues besides the heart; furthermore, we show that in patients with CCD these Abs are associated with an insulin resistance profile and atherogenic dyslipidemia, providing biological plausibility to the hypothesis that adrenergic activation by anti-β2AR Abs could contribute to the pathogenesis of metabolic disturbances described in CCD patients, increasing their cardiovascular risk.

Brain More Resistant to Energy Restriction Than Body: A Systematic Review

The gluco-lipostatic theory and its modern variants assume that blood glucose and energy stores are controlled in closed-loop feedback processes. The Selfish Brain theory is based on the same assumptions, but additionally postulates that the brain, as an independent energy compartment, self-regulates its energy concentration with the highest priority. In some clinical situations these two theories make opposite predictions. To investigate one of these situations, namely caloric restriction, we formulated a hypothesis which, if confirmed, would match the predictions of the Selfish Brain theory—but not those of the gluco-lipostatic theory. Hypothesis: Calorie restriction causes minor mass (energy) changes in the brain as opposed to major changes in the body. We conducted a systematic review of caloric-restriction studies to test whether or not the evaluated studies confirmed this hypothesis. We identified 3,157 records, screened 2,804 works by title or abstract, and analyzed 232 by full text. According to strict selection criteria (set out in our PROSPERO preregistration, complying with PRISMA guidelines, and the pre-defined hypothesis-decision algorithm), 8 papers provided enough information to decide on the hypothesis: In animals, high-energy phosphates were measured by ³¹P-nuclear magnetic resonance, and organ and total body weights were measured by scales, while in humans organ sizes were determined by magnetic resonance imaging. All 8 decidable papers confirmed the hypothesis, none spoke against it. The evidence presented here clearly shows that the most accurate predictions are possible with a theory that regards the brain as independently self-regulating and as occupying a primary position in a hierarchically organized energy metabolism.

Time-weighted lactate as a predictor of adverse outcome in acute heart failure

Aims

The role of dynamic changes in lactate concentrations on prognosis in acute heart failure has been poorly investigated. The aim of this study was to explore the predictive value of 24 h time‐weighted lactate (LAC_TW) in patients with acute heart failure.

Methods and results

Ninety‐six consecutive acute heart failure patients presenting to the Emergency Department of San Paolo Hospital, Naples, Italy, were prospectively enrolled. Arterial blood lactate was measured at admission and during the following 24 h at random time intervals. LAC_TW was obtained by the sum of the average lactate values among consecutive time points multiplied by the intervals between consecutive time points and dividing the sum by the total time (24 h). The outcome was a composite of need of admission to the intensive care unit, hospitalization duration >7 days, or intra‐hospital death. Admission lactate, maximum measured lactate, and LAC_TW were collected. Univariate and multivariate Cox regression analysis was applied to determine the hazard ratio (HR) of developing the outcome. Forty‐three patients experienced the pre‐specified outcome. In sex‐adjusted and age‐adjusted multivariable analysis, LAC_TW predicted the outcome occurrence (HR: 1.51, 95% confidence interval: 1.24, 1.84, P < 0.001). Risk stratification analysis based on LAC_TW tertiles demonstrated a gradual increase in risk of developing the outcome (HR: 17.32, 95% confidence interval: 2.30, 130.23, P = 0.006) for the highest LAC_TW tertile.

Conclusions

In acute heart failure patients, 24 h LAC_TW had a significant independent predictive value for adverse intra‐hospital outcome. LAC_TW could be a useful index at identifying high‐risk patients who may require a more aggressive treatment during hospitalization.

Selective ß2-Adrenoceptor Agonists and Relevant Hyperlactatemia: Systematic Review and Meta-Analysis

Selective ß₂-agonists have been imputed as potential cause of l-hyperlactatemia since the 1970s. To document the prevalence of hyperlactatemia associated with selective ß₂-agonists and to investigate the predisposing factors, we searched for published articles until April 2019 pertaining to the interplay of administration of selective ß₂-agonists and circulating l-lactic acid in the Excerpta Medica, Web of Science, and the U.S. National Library of Medicine databases. Out of the 1834 initially retrieved records, 56 articles were included: 42 papers reporting individual cases, 2 observational studies, and 12 clinical trials. Forty-seven individual patients receiving a selective ß₂-agonist were found to have l-lactatemia ≥5.0 mmol/L, which decreased by ≥3.0 mmol/L or to ≤2.5 mmol/L after discontinuing (N = 24), reducing (N = 17) or without modifying the dosage of the selective ß₂-agonist (N = 6). Clinical trials found that l-lactic acid significantly increased in healthy volunteers administered a ß₂-agonist. l-lactatemia ≥5.0 mmol/L was observed in 103 (24%) out of 426 patients with asthma or preterm labor managed with a selective ß₂-agonist and was more common in patients with asthma (30%) than in premature labor (5.9%). A significant relationship was also noted between l-lactate level and intravenous albuterol dose or its circulating level. In conclusion, relevant l-hyperlactatemia is common on high dose treatment with a selective ß₂-agonist.

Hyperlactatemia and the Importance of Repeated Lactate Measurements in Critically Ill Patients

Objective

The aim of the study was to describe the prevalence of hyperlactatemia and emphasis on repeated lactate measurements in critically ill patients, and the associated mortality.

Materials and methods

The study included 70 patients admitted in the Medical Intensive Care Unit at the Clinical Center, University of Sarajevo, in a 6-month period (July - December 2015). The following data were obtained: age, gender, reason for admission, Simplified Acute Physiology Score II, Acute Physiology and Chronic Health Evaluation, lactate concentrations upon admission, after 24 and 48 hours, and outcome (discharge from hospital or death).

Results

Upon admission,hyperlactatemia was present in 91.4% patients with a mean concentration of lactate 4.13 ±1.21 mmol/L. Lactate concentration at 48 hours was independently associated within creased in-hospital mortality (P = 0.018).

Conclusion

Persistent hyperlactatemia is associated with adverse outcome in critically ill patients. Lactate concentration at 48 hours is independently associated within creased in-hospital mortality and it represents a statistically significant predictive marker of fatal outcomes of patients. Blood lactate concentrations > 2.25 mmol/L should be used by clinicians to identify patients at higher risk of death.

Is Exercise Training Appropriate for Patients With Advanced Heart Failure Receiving Continuous Inotropic Infusion? A Review

Exercise-based rehabilitation programs have been reported to have beneficial effects for patients with heart failure. However, there is little evidence about whether this is the case in patients with more severe heart failure. In particular, there is a question in the clinical setting whether patients with advanced heart failure and continuous inotropic infusion should be prescribed exercise training. In contrast, many studies conclude that prolonged immobility associated with heart failure profoundly impairs physical function and promotes muscle wasting that could further hasten the course of heart failure. By contrast, exercise training has various effects not only in improving exercise capacity but also on vascular function, skeletal muscle, and autonomic balance. In this review, we summarize the effectiveness and discuss methods of exercise training in patients with advanced heart failure receiving continuous inotropic agents such as dobutamine.

The value of blood lactate kinetics in critically ill patients: a systematic review

BACKGROUND

The time course of blood lactate levels could be helpful to assess a patient's response to therapy. Although the focus of published studies has been largely on septic patients, many other studies have reported serial blood lactate levels in different groups of acutely ill patients.

METHODS

We performed a systematic search of PubMed, Science Direct, and Embase until the end of February 2016 plus reference lists of relevant publications. We selected all observational and interventional studies that evaluated the capacity of serial blood lactate concentrations to predict outcome. There was no restriction based on language. We excluded studies in pediatric populations, experimental studies, and studies that did not report changes in lactate values or all-cause mortality rates. We separated studies according to the type of patients included. We collected data on the number of patients, timing of lactate measurements, minimum lactate level needed for inclusion if present, and suggested time interval for predictive use.

RESULTS

A total of 96 studies met our criteria: 14 in general ICU populations, five in general surgical ICU populations, five in patients post cardiac surgery, 14 in trauma patients, 39 in patients with sepsis, four in patients with cardiogenic shock, eight in patients after cardiac arrest, three in patients with respiratory failure, and four in other conditions. A decrease in lactate levels over time was consistently associated with lower mortality rates in all subgroups of patients. Most studies reported changes over 6, 12 or 24 hrs, fewer used shorter time intervals. Lactate kinetics did not appear very different in patients with sepsis and other types of patients. A few studies suggested that therapy could be guided by these measurements.

CONCLUSIONS

The observation of a better outcome associated with decreasing blood lactate concentrations was consistent throughout the clinical studies, and was not limited to septic patients. In all groups, the changes are relatively slow, so that lactate measurements every 1-2 hrs are probably sufficient in most acute conditions. The value of lactate kinetics appears to be valid regardless of the initial value.

Lactate kinetics and mitochondrial respiration in skeletal muscle of healthy humans under influence of adrenaline

Plasma lactate is widely used as a biomarker in critical illness. The aims of the present study were to elucidate the usefulness of a three-compartment model for muscle lactate kinetics in humans and to characterize the response to an exogenous adrenaline challenge. Repeated blood samples from artery and femoral vein together with blood flow measurements and muscle biopsies were obtained from healthy male volunteers (n=8) at baseline and during an adrenaline infusion. Concentrations of lactate and enrichment of [13C]lactate were measured and kinetics calculated. Mitochondrial activity, glycogen concentration, oxygen uptake and CO2 release were assessed. The adrenaline challenge increased plasma lactate 4-fold as a result of a greater increase in the rate of appearance (R(a)) than the increase in the rate of disappearance (R(d)). Leg muscle net release of lactate increased 3.5-fold, whereas intramuscular production had a high variation but did not change. Mitochondrial state 3 respiration increased by 30%. Glycogen concentration, oxygen uptake and CO2 production remained unchanged. In conclusion a three-compartment model gives additional information to the two-compartment model but, due to its larger variation and invasive muscle biopsy, it is less likely to become a regularly used tool in clinical research. Hyperlactataemia in response to adrenergic stimuli was driven by an elevated lactate release from skeletal muscle most probably due to a redirection of a high intramuscular turnover rather than an increased production.

Timing of caffeine ingestion alters postprandial metabolism in rats

OBJECTIVE

The association between caffeine intake and the risk for chronic diseases, namely type 2 diabetes, has not been consistent, and may be influenced by the timing of caffeine ingestion. The aim of this study was to investigate the acute effect of caffeine administered in different scenarios of meal ingestion on postprandial glycemic and lipidemic status, concomitant with changes in body glycogen stores.

METHODS

Forty overnight-fasted rats were randomly divided into five groups (meal-ingested, caffeine-administered, post-caffeine meal-ingested, co-caffeine meal-ingested, post-meal caffeine-administered), and tube-fed the appropriate intervention, then sacrificed 2 h later. Livers and gastrocnemius muscles were analyzed for glycogen content; blood samples were analyzed for glucose, insulin, triglycerides, and non-esterified fatty acid concentrations.

RESULTS

Postprandial plasma glucose concentrations were similar between groups, while significantly higher levels of insulin were witnessed following caffeine administration, irrespective of the timing of meal ingestion. Triglyceride concentrations were significantly lower in the caffeine-administered groups. Regarding glycogen status, although caffeine administration before meal ingestion reduced hepatic glycogen content, co- and post-meal caffeine administration failed to produce such an effect. Muscle glycogen content was not significantly affected by caffeine administration.

CONCLUSIONS

Caffeine administration seems to decrease insulin sensitivity as indicated by the sustenance of glucose status despite the presence of high insulin levels. The lower triglyceride levels in the presence of caffeine support the theory of retarded postprandial triglyceride absorption. Caffeine seems to play a biphasic role in glucose metabolism, as indicated by its ability to variably influence hepatic glycogen status.

Effects of dobutamine on systemic, regional and microcirculatory perfusion parameters in septic shock: a randomized, placebo-controlled, double-blind, crossover study

PURPOSE

The role of dobutamine during septic shock resuscitation is still controversial since most clinical studies have been uncontrolled and no physiological study has unequivocally demonstrated a beneficial effect on tissue perfusion. Our objective was to determine the potential benefits of dobutamine on hemodynamic, metabolic, peripheral, hepatosplanchnic and microcirculatory perfusion parameters during early septic shock resuscitation.

METHODS

We designed a randomized, controlled, double-blind, crossover study comparing the effects of 2.5-h infusion of dobutamine (5 mcg/kg/min fixed-dose) or placebo in 20 septic shock patients with cardiac index ≥2.5 l/min/m(2) and hyperlactatemia. Primary outcome was sublingual perfused microvascular density.

RESULTS

Despite an increasing cardiac index, heart rate and left ventricular ejection fraction, dobutamine had no effect on sublingual perfused vessel density [9.0 (7.9-10.1) vs. 9.1 n/mm (7.9-9.9); p = 0.24] or microvascular flow index [2.1 (1.8-2.5) vs. 2.1 (1.9-2.5); p = 0.73] compared to placebo. No differences between dobutamine and placebo were found for the lactate levels, mixed venous-arterial pCO2 gradient, thenar muscle oxygen saturation, capillary refill time or gastric-to-arterial pCO2 gradient. The indocyanine green plasma disappearance rate [14.4 (9.5-25.6) vs. 18.8 %/min (11.7-24.6); p = 0.03] and the recovery slope of thenar muscle oxygen saturation after a vascular occlusion test [2.1 (1.1-3.1) vs. 2.5 %/s (1.2-3.4); p = 0.01] were worse with dobutamine compared to placebo.

CONCLUSIONS

Dobutamine failed to improve sublingual microcirculatory, metabolic, hepatosplanchnic or peripheral perfusion parameters despite inducing a significant increase in systemic hemodynamic variables in septic shock patients without low cardiac output but with persistent hypoperfusion.

Peripheral adrenoceptors: the impetus behind glucose dysregulation and insulin resistance

It is now accepted that several pharmacological drug treatments trigger clinical manifestations of glucose dysregulation, such as hyperglycaemia, glucose intolerance and insulin resistance, in part through poorly understood mechanisms. Persistent sympathoadrenal activation is linked to glucose dysregulation and insulin resistance, both of which significantly increase the risk of emergent endocrinological disorders, including metabolic syndrome and type 2 diabetes mellitus. Through the use of targeted mutagenesis and pharmacological methods, preclinical and clinical research has confirmed physiological glucoregulatory roles for several peripheral α- and β-adrenoceptor subtypes. Adrenoceptor isoforms in the pancreas (α(2A) and β(2) ), skeletal muscle (α(1A) and β(2) ), liver (α(1A & B) and β(2) ) and adipose tissue (α(1A) and β(1 & 3) ) are convincing aetiological targets that account for both immediate and long-lasting alterations in blood glucose homeostasis. Because significant overlap exists between the therapeutic applications of numerous classes of drugs and their associated adverse side-effects, a better understanding of peripheral adrenoceptor-mediated glucose metabolism is thus warranted. Therefore, at the same time as providing a brief review of glucose homeostasis in the periphery, the present review addresses both functional and pathophysiological roles of the mammalian α(1) , α(2) , and β-adrenoceptor isoforms in whole-body glucose turnover. We highlight evidence relating to the clinical use of common adrenergic drugs and their impacts on glucose metabolism.

Hydroxocobalamin and epinephrine both improve survival in a swine model of cyanide-induced cardiac arrest

STUDY OBJECTIVE

To determine whether hydroxocobalamin will improve survival compared with epinephrine and saline solution controls in a model of cyanide-induced cardiac arrest.

METHODS

Forty-five swine (38 to 42 kg) were tracheally intubated, anesthetized, and central venous and arterial continuous cardiovascular monitoring catheters were inserted. Potassium cyanide was infused until cardiac arrest developed, defined as mean arterial pressure less than 30 mm Hg. Animals were treated with standardized mechanical chest compressions and were randomly assigned to receive one of 3 intravenous bolus therapies: hydroxocobalamin, epinephrine, or saline solution (control). All animals were monitored for 60 minutes after cardiac arrest. Additional epinephrine infusions were used in all arms of the study after return of spontaneous circulation for systolic blood pressure less than 90 mm Hg. A sample size of 15 animals per group was determined according to a power of 80%, a survival difference of 0.5, and an α of 0.05. Repeated-measure ANOVA was used to determine statistically significant changes between groups over time.

RESULTS

Baseline weight, time to arrest, and cyanide dose at cardiac arrest were similar in the 3 groups. Coronary perfusion pressures with chest compressions were greater than 15 mm Hg in both treatment groups indicating sufficient compression depth. Zero of 15 (95% confidence interval [CI] 0% to 25%) animals in the control group, 11 of 15 (73%; 95% CI 48% to 90%) in the hydroxocobalamin group, and 11 of 15 (73%; 95% CI 48% to 90%) in the epinephrine group survived to the conclusion of the study (P<.001). The proportion of animals with return of spontaneous circulation at 5 minutes was 4 of 15 (27%; 95% CI 10% to 52%), and that of return of spontaneous circulation at 10 minutes was 11 of 15 (73%; 95% CI 48% to 90%) in the 2 treatment groups. Additional epinephrine infusion after return of spontaneous circulation was administered for hypotension in 2 of 11 (18%; 95% CI 4% to 48%) hydroxocobalamin animals and in 11 of 11 (100%; 95% CI 70% to 100%) of the epinephrine animals (P<.001). At 60 minutes, serum lactate was significantly lower in the hydroxocobalamin group compared with the epinephrine group (4.9 [SD 2.2] versus 12.3 [SD 2.2] mmol/L), and the pH was significantly higher (7.34 [SD 0.03] versus 7.15 [SD 0.07]). Serial blood cyanide levels in the hydroxocobalamin group were also lower than that of the epinephrine group from cardiac arrest through the conclusion of the study.

CONCLUSION

Intravenous hydroxocobalamin and epinephrine both independently improved survival compared with saline solution control in our swine model of cyanide-induced cardiac arrest. Hydroxocobalamin improved mean arterial pressure and pH, decreased blood lactate and cyanide levels, and decreased the use of rescue epinephrine therapy compared with that in the epinephrine group.

Utilization of dietary glucose in the metabolic syndrome

This review is focused on the fate of dietary glucose under conditions of chronically high energy (largely fat) intake, evolving into the metabolic syndrome. We are adapted to carbohydrate-rich diets similar to those of our ancestors. Glucose is the main energy staple, but fats are our main energy reserves. Starvation drastically reduces glucose availability, forcing the body to shift to fatty acids as main energy substrate, sparing glucose and amino acids. We are not prepared for excess dietary energy, our main defenses being decreased food intake and increased energy expenditure, largely enhanced metabolic activity and thermogenesis. High lipid availability is a powerful factor decreasing glucose and amino acid oxidation. Present-day diets are often hyperenergetic, high on lipids, with abundant protein and limited amounts of starchy carbohydrates. Dietary lipids favor their metabolic processing, saving glucose, which additionally spares amino acids. The glucose excess elicits hyperinsulinemia, which may derive, in the end, into insulin resistance. The available systems of energy disposal could not cope with the excess of substrates, since they are geared for saving not for spendthrift, which results in an unbearable overload of the storage mechanisms. Adipose tissue is the last energy sink, it has to store the energy that cannot be used otherwise. However, adipose tissue growth also has limits, and the excess of energy induces inflammation, helped by the ineffective intervention of the immune system. However, even under this acute situation, the excess of glucose remains, favoring its final conversion to fat. The sum of inflammatory signals and deranged substrate handling induce most of the metabolic syndrome traits: insulin resistance, obesity, diabetes, liver steatosis, hyperlipidemia and their compounded combined effects. Thus, a maintained excess of energy in the diet may result in difficulties in the disposal of glucose, eliciting inflammation and the development of the metabolic syndrome.

Effects of adrenaline on lactate, glucose, lipid and protein metabolism in the placebo controlled bilaterally perfused human leg

AIM

Adrenaline has widespread metabolic actions, including stimulation of lipolysis and induction of insulin resistance and hyperlactatemia. Systemic adrenaline administration, however, generates a very complex hormonal and metabolic scenario. No studies employing regional, placebo controlled and adrenaline infusion exist. Our study was designed to test the hypothesis that local placebo controlled leg perfusion with adrenaline directly increases local lactate release, stimulates lipolysis, induces insulin resistance and leaves protein metabolism unaffected.

METHODS

  We studied seven healthy volunteers with bilateral femoral vein and artery catheters during 3-h basal and 3-h hyperinsulinemic (0.6 mU kg(-1) min(-1) ) euglycemic clamp conditions. One femoral artery was perfused with saline and the other with adrenaline (0.4 μg min m(-2) ). Lipid metabolism was quantified with [9,10-(3) H] palmitate and amino acid metabolism with (15) N-phenylalanine and lactate and glucose by raw arterio-venous differences.

RESULTS

  Femoral vein plasma adrenaline increased ≈eightfold in the perfused leg with unaltered blood flows. Adrenaline perfusion significantly increased local leg lactate release from 0.01 to 0.25 mmol min(-1) per leg, palmitate release in the basal state 11.5-16.9 μmol min(-1) per leg and during the clamp 2.62-8.44 μmol min(-1) per leg. Glucose uptake decreased during the clamp from ≈180 to 30 μmol min(-1) per leg. Phenylalanine kinetics was not affected by adrenaline.

CONCLUSION

  Adrenaline directly increases lactate release and lipolysis and inhibits insulin-stimulated glucose uptake in the perfused human leg. Adrenaline has no direct effects on peripheral amino acid metabolism. Adrenaline-induced lactate release from striated muscle may be an important mechanism underlying hyperlactatemia in the critically ill.

The β3-adrenergic agonist (BRL35135A) acutely increases oxygen consumption and plasma intermediate metabolites in sheep

There is evidence that an atypical adrenoreceptor subtype is involved in mediating some of the physiological effects of catecholamines, particularly in some adipose tissue sites. Therefore, three experiments were conducted to determine the metabolic and energetic responses to oral administration of the purported β3-agonist BRL35135A in ruminant lambs. The post-prandial increase in O2 consumption (0.109 versus 0.139 L/min) and CO2 production (0.102 versus 0.127 L/min) at 30 min after feeding was greater (P < 0.05) in the lambs receiving 5 mg of the BRL35135A. Treatment × time interactions over the period between –50 and 220 min indicate significant increases in plasma non-esterified fatty acids (P < 0.001), glucose (P < 0.001) and lactate (P = 0.024) in lambs consuming a single oral dose of 5 mg BRL35135A. In a subsequent experiment there were similar interactions over the period between –120 and 1440 min for non-esterified fatty acids (P < 0.001), glucose (P < 0.001) and lactate (P < 0.001) in lambs consuming a lower oral dose of 1 mg BRL35135A. The effects of BRL35135A on plasma non-esterified fatty acids (P = 0.95), glucose (P = 0.84) and lactate (P = 0.68) were not modified by the β1- and β2-adrenergic antagonist alprenolol suggesting that the effects were mediated via β3-adrenergic receptor subtypes. In conclusion, these experiments indicate that BRL35135A is acutely active in sheep when given with feed, as indicated by increases in respiratory gas exchange and plasma metabolite concentrations.

An implantable biochip to influence patient outcomes following trauma-induced hemorrhage

Following hemorrhage-causing injury, lactate levels rise and correlate with the severity of injury and are a surrogate of oxygen debt. Posttraumatic injury also includes hyperglycemia, with continuously elevated glucose levels leading to extensive tissue damage, septicemia, and multiple organ dysfunction syndrome. A temporary, implantable, integrated glucose and lactate biosensor and communications biochip for physiological status monitoring during hemorrhage and for intensive care unit stays has been developed. The dual responsive, amperometric biotransducer uses the microdisc electrode array format upon which were separately immobilized glucose oxidase and lactate oxidase within biorecognition layers, 1.0-5.0 μm thick, of 3 mol% tetraethyleneglycol diacrylate cross-linked p(HEMA-co-PEGMA-co-HMMA-co-SPA)-p(Py-co-PyBA) electroconductive hydrogels. The device was then coated with a bioactive hydrogel layer containing phosphoryl choline and polyethylene glycol pendant moieties [p(HEMA-co-PEGMA-co-HMMA-co-MPC)] for indwelling biocompatibility. In vitro cell proliferation and viability studies confirmed both polymers to be non-cytotoxic; however, PPy-based electroconductive hydrogels showed greater RMS 13 and PC12 proliferation compared to controls. The glucose and lactate biotransducers exhibited linear dynamic ranges of 0.10-13.0 mM glucose and 1.0-7.0 mM and response times (t(95)) of 50 and 35-40 s, respectively. Operational stability gave 80% of the initial biosensor response after 5 days of continuous operation at 37 °C. Preliminary in vivo studies in a Sprague-Dawley hemorrhage model showed tissue lactate levels to rise more rapidly than systematic lactate. The potential for an implantable biochip that supports telemetric reporting of intramuscular lactate and glucose levels allows the refinement of resuscitation approaches for civilian and combat trauma victims.

Prognostic value of admission serum lactate concentrations in intensive care unit patients

BACKGROUND

Although blood lactate concentrations have an established prognostic value in circulatory shock or after cardiac arrest, their relationship with morbidity and length of stay in general intensive care unit (ICU) populations has not been well defined.

METHODS

This study included all 433 patients (246 surgical and 187 medical) consecutively admitted to the Department of medico-surgical intensive care. Hyperlactataemia was defined as a serum lactate concentration > or = 2 mEq/l.

RESULTS

On admission, 195 patients (45%) had hyperlactataemia. Hyperlactataemic patients had higher Acute Physiology and Chronic Health Evaluation (APACHE) II (13.3 +/- 6.9 vs 10.0 +/- 5.2) and Sequential Organ Failure Assessment (SOFA) (5.3 +/- 3.3 vs 3.3 +/- 2.3) scores than patients with normal lactate concentrations (both p < 0.01). There was no overall difference in length of ICU stay (LOS) between the two groups but survivors in the hyperlactataemic group had a longer LOS than survivors in the normal lactate group, whereas hyperlactataemic non-survivors had a shorter LOS than normal lactate non-survivors. Mortality was 9% in patients with normal lactate concentrations and 23% in hyperlactataemic patients. The mortality rate increased with increasing lactate concentrations, from 17% in patients with lactate concentrations from 2-4 mEq/l to 64% in those with concentrations more than 8 mEq/l. Non-survivors had higher lactate concentrations than survivors on admission, and after 24 and 48 hours. Risk factors for developing hyperlactataemia that were present on admission were SOFA score > 5, mean arterial blood pressure less than 70 mmHg, blood sugar greater than 110 mg/dl, and current use of vasopressors.

CONCLUSIONS

Our study documents a direct relationship between the serum lactate level on ICU admission and not only the risk of death in ICU but also the length of ICU stay. Hyperlactataemic survivors have a longer LOS and non-survivors a shorter LOS than normal lactate survivors and non-survivors, respectively.

Muscle blood flow response to mental stress and adrenaline infusion in man: microdialysis ethanol technique compared to (133)Xe clearance and venous occlusion plethysmography

BACKGROUND AND AIM

Adrenaline, administered locally by microdialysis in skeletal muscle, causes vasoconstriction around the microdialysis catheter. This is contrary to the vasodilation that normally occurs when adrenaline is infused intravenously or intra-arterially. The hypothesis was tested that vasoconstriction, measured by microdialysis, would not occur with two interventions causing increased plasma levels of adrenaline, mental stress and intravenous adrenaline infusion (0.1 nmol kg(-1) min(-1)).

METHODS

Twenty-four men (27 +/- 1.6 years) underwent these interventions. Blood flow was determined by the microdialysis ethanol technique and (133)Xe clearance (gastrocnemius muscle, medial head) and by venous occlusion plethysmography (calf).

RESULTS

The ethanol outflow/inflow ratio, which is inversely related to blood flow, decreased to 92.0 +/- 3.4% of basal, P = 0.014 (mean +/- SEM, n = 16) during the mental stress test, but increased to 108.3 +/- 2.2% of basal, P = 0.001 (n = 16) during the adrenaline infusion. The latter increase was abolished when adrenaline was infused during alpha-receptor blockade by phentolamine. On the contrary, by (133)Xe clearance and venous occlusion plethysmography, blood flow increased during both interventions; 2.0-1.7-fold (mental stress) and 1.3-1.4-fold (adrenaline infusion), respectively, P<0.05.

CONCLUSION

Adrenaline causes vasoconstriction in skeletal muscle when blood flow is measured with the microdialysis ethanol technique, irrespective of the mode of administration. The discrepant blood flow result obtained with the microdialysis ethanol technique might, at least partly, be explained by differential diffusion properties of ethanol and (133)Xe. An additional or alternative explanation might be that an inserted microdialysis catheter shifts the balance of vasoconstrictor and vasodilator effects of adrenaline in skeletal muscle.

Assessment of sympathetic cardiovascular drive in human hypertension: achievements and perspectives

Methodological refinements in the assessment of human sympathetic cardiovascular drive have allowed throughout the years to better define the role of the sympathetic nervous system in the pathophysiology of hypertension. Earlier studies have provided evidence that indirect markers of adrenergic drive, such as plasma or urinary norepinephrine as well as heart rate, often display an increase in the hypertensive state. Direct recording of efferent postganglionic muscle sympathetic nerve traffic via microneurography and regional norepinephrine spillover technique have conclusively documented the occurrence of an adrenergic overdrive in hypertension, showing that the sympathetic activation is directly related to the severity of the hypertensive state and is widespread to different cardiovascular districts. The present review will focus on some major features of the "neuroadrenergic hypothesis of hypertension." In particular it will examine the mechanisms responsible for the adrenergic overdrive, the relationships between the sympathetic activation and the metabolic disarray of frequent detection in the hypertensive state, and the participation of neuroadrenergic factors at the development of the hypertension-related target organ damage. Further issues addressed will be the contribution of the hyperadrenergic state to the different patterns of the 24-hour blood pressure profile as well as to the day/night blood pressure variability described in the hypertensive state and the behavior of the sympathetic function in the hypertensive states complicated by the presence of other cardiovascular or metabolic disease. Finally, the clinical and therapeutic implications of the neuroadrenergic abnormalities occurring in hypertension, as well as the areas worthy of future research, will be highlighted.