Elevated Blood Lactate Concentration Research Articles

Mitochondrial DNA m.3243A>G mutation in ethambutol-induced optic neuropathy: A case report

A 35-year-old man with maternally inherited diabetes presented with blurring of vision in both eyes for 6 months. He previously received antituberculous therapy including ethambutol (EMB) for 2 years. Temporal disc pallor and central scotomas were noticed in both eyes. P100 latency was delayed in visual evoked potential bilaterally. In addition, an elevated blood lactate concentration was observed. Interestingly, although EMB's potential optic neuropathy toxicity was our first consideration, a m.3243A>G mutation of mitochondrial DNA was found in the blood. Herein, we reported a young patient carrying a novel Leber's hereditary optic neuropathy mutation who developed EMB-induced optic neuropathy.

Extracorporeal life support in cardiotoxicant poisoning-A narrative review.

Extracorporeal life support (ECLS) improves circulation in life-threatening cardiac dysfunction or arrest patients. Its benefits in drug-induced cardiovascular complications are debated. Indications and outcomes are poorly established. We performed a narrative review discussing ECLS indications, timing and results in cardiotoxicant-poisoned patients. The review was focused on antiarrhythmic drugs and aluminium phosphide. Literature analysis was limited to the past 30 years in adults. Most reports were single cases and retrospective except one prospective case series of limited size, two of them controlled. ECLS indications and timing were at the discretion of physicians in charge but mostly included persistent cardiovascular failure despite elevated doses of inotropic/vasopressor support associated with elevated blood lactate concentrations (usually, >5mmol/L) and collapsed left ventricular ejection fraction (LVEF; usually, ≤40%). Survival improved using ECLS versus standard care in one study. Survival was ~80% if ECLS was implemented in refractory cardiovascular failure and 25%-66% if implemented in cardiac arrest. In two controlled studies, survival of ECLS-treated aluminium phosphide-poisoned patients was improved versus standard care, if implemented in the presence of systolic blood pressure ≤80 mmHg despite inotropic/vasopressor treatment, arterial pH ≤ 7.0 and LVEF ≤ 40%. Despite low-to-moderate level of evidence, ECLS seems effective to improve survival in selected cardiotoxicant-poisoned patients. Selection criteria need clarification.

Effects of lactate administration on hypertrophy and mTOR signaling activation in mouse skeletal muscle.

Lactate is a metabolic product of glycolysis and has recently been shown to act as a signaling molecule that induces adaptations in oxidative metabolism. In this study, we investigated whether lactate administration enhanced muscle hypertrophy and protein synthesis responses during resistance exercise in animal models. We used male ICR mice (7–8 weeks old) were used for chronic (mechanical overload induced by synergist ablation: [OL]) and acute (high‐intensity muscle contraction by electrical stimulation: [ES]) resistance exercise models. The animals were intraperitoneally administrated a single dose of sodium lactate (1 g/kg of body weight) in the ES study, and once a day for 14 consecutive days in the OL study. Two weeks of mechanical overload increased plantaris muscle wet weight (main effect of OL: p < 0.05) and fiber cross‐sectional area (main effect of OL: p < 0.05), but those were not affected by lactate administration. Following the acute resistance exercise by ES, protein synthesis and phosphorylation of p70 S6 kinase and ribosomal protein S6, which are downstream molecules in the anabolic signaling cascade, were increased (main effect of ES: p < 0.05), but lactate administration had no effect. This study demonstrated that exogenous lactate administration has little effect on the muscle hypertrophic response during resistance exercise using acute ES and chronic OL models. Our results do not support the hypothesis that elevated blood lactate concentration induces protein synthesis responses in skeletal muscle.

Incorporating estuarine-angler behaviour and delayed blood sampling into the rapid assessment of catch-and release angling on the iconic dusky kob Argyrosomus japonicus

Argyrosomus japonicus is arguably South Africa’s most important estuarine recreational and small-scale fishery species. Although juvenile A. japonicus predominate in estuarine environments, where catch-and-release angling is common, limited C&R studies have taken place. The aim of this study was to use angler-behaviour to robustly examine the physiological stress response, reflex impairment and short-term (12–36-hour) survival of A. japonicus following C&R angling. Observations of estuarine recreational angling informed three air exposure treatments based on minimum (10 s), mean (75 s) and maximum (240 s) observed times, for use in a controlled angling experiment. Based on a prior laboratory study, blood sampling was delayed 30–40 min post-capture to allow for peak accumulations of lactate and glucose. Long air exposure (240 s) predicted significantly higher blood glucose concentrations (ANOVA, p = 0.03) than short (10 s) exposure. Similarly, both long (p = 0.01) and moderate (75 s; p = 0.01) air exposure significantly predicted elevated blood lactate concentrations, when compared with short exposure. In terms of physical impairment, long air exposure (240 s) had a significant negative influence on the reflex response (cumulative link model, p = 0.01) of A. japonicus. An observed short-term mortality of 7.7% was primarily attributed to hooking injury. To reduce significant physiological and physical stress, it is proposed that anglers should aim to reduce air exposure times to below the observed mean of 75 s, and ideally to 10 s. For relevant and meaningful future C&R studies, we propound the incorporation of angler behavioural assessments, and the investigation of physiological stress responses, prior to designing field studies.

Blood Lactate Level Evolution during Lung Transplantation

<h3>Purpose</h3> Lactic acidosis has been recently propose as independently associated with longer intubation times and length of stay in lung transplantation(1). However, there is no data on the association between elevated blood lactate concentration (BLC) and grade 3 primary graft dysfunction at day 3 after lung transplantation (PGD3). The purpose of the study was to investigate the profile of BLC during double-lung transplantation and it association with PGD3. <h3>Methods</h3> We performed a retrospective observational study of all bilateral lung transplantations at the Foch Hospital from January 2012 to December 2019, excluding those on bridge-to-transplantation, under cardiopulmonary bypass, and multiple-organ transplantation. BLC was measured at every key time of the invention: initially, at every pulmonary artery clamping or declamping, and at end-surgery stage. The ethical committee of the French Society of Anesthesia and Critical Care (SFAR) approved the study. The evolution of intraoperative BLC was evaluated with a paired T-test with Holm correction to compare lactate. AUC was constructed to determine Sp and Se. The optimal threshold of lactates variable used for separation of PGD3 was calculated using the Youden-index. <h3>Results</h3> Over 478 patients were included, 83 (17.3%) had a PGD3. BLC evolution during surgery is illustrated in figure 1. The median of BLC at end-surgery was 2 [1.5 - 3.1] and 3.3 [2.4 - 4.9] mmol/L in no PGD3 and PGD3 groups respectively, p = 0.02. BLC kinetic illustrated by its variability was the best predictive factor of PGD3 (AUC=0.84, Se=77.03, Sp=79.82%). <h3>Conclusion</h3> Hyperlactatemia reflects anaerobic metabolism during peroperative hemodynamic unstable conditions and poor oxygen exchange after implantation of the grafts. Blood lactate variability during surgery is associated with PGD3.1. Worrell SG, et al. Is Lactic Acidosis After Lung Transplantation Associated With Worse Outcomes The Annals of Thoracic Surgery. 2020 Aug;110(2):434-40.

Effects of Exercise Sequence and Velocity Loss Threshold During Resistance Training on Following Endurance and Strength Performance During Concurrent Training.

This study aimed to analyze the response to 4 concurrent training interventions differing in the training sequence and in the velocity loss (VL) threshold during strength training (20% vs 40%) on following endurance and strength performance. A randomized crossover research design was used. Sixteen trained men performed 4 training interventions consisting of endurance training (ET) followed by resistance training (RT), with 20% and 40% VL, respectively (ET + RT20 and ET + RT40), and RT with 20% and 40% VL, respectively, followed by ET (RT20 + ET and RT40 + ET). The ET consisted of running for 10 minutes at 90% of maximal aerobic velocity. The RT consisted of 3 squat sets with 60% of 1-repetition maximum. A 5-minute rest was given between exercises. The oxygen uptake throughout the ET and repetition velocity during RT were recorded. The blood lactate concentration, vertical jump, and squat velocity were measured at preexercise and after the endurance and strength exercises. The RT40 + ET protocol showed an impaired running time along with higher ventilatory equivalents compared with those protocols that performed the ET without previous fatigue. No significant differences were observed in the repetitions per set performed for a given VL threshold, regardless of the exercise sequence. The protocols consisting of 40%VL induced greater reductions in jump height and squat velocity, along with elevated blood lactate concentration. A high VL magnitude (40%VL) induced higher metabolic and mechanical stress, as well as greater residual fatigue, on the following ET performance.

Body temperature and physical performance responses are not maintained at the time of pitch-entry when typical substitute-specific match-day practices are adopted before simulated soccer match-play

ObjectivesTo profile performance and physiological responses to typical patterns of match-day activity for second-half soccer substitutes. DesignDescriptive. MethodsFollowing a warm-up, 13 male team sports players underwent ∼85min of rest, punctuated with five min rewarm-ups at ∼25, ∼50, and ∼70min, before ∼30min of simulated soccer match-play. Countermovement jump performance (jump height, peak power output), alongside 15m sprints, were assessed post-warm-up, and pre- and post-simulated match-play. Core temperature, heart rate, ratings of perceived exertion, and blood glucose and lactate concentrations were measured throughout. ResultsWarm-up-induced core temperature elevations (∼2.3%, +0.85°C; p<0.001) were maintained until after the first rewarm-up. Thereafter, core temperature was reduced from post-warm-up values until pre-simulated match-play (∼1.6%, −0.60°C; p<0.001), where values were similar to pre-warm-up (37.07±0.24°C, p=0.981). Simulated match-play increased core temperature progressively (p≤0.05) but values remained lower than post-warm-up (∼5min; p=0.002) until ∼10min into exercise. From post-warm-up to pre-simulated match-play, sprint times (∼3.9%, +0.10s, p=0.003), jump height (∼9.4%, −3.1cm; p=0.017), and peak power output (∼7.2%, −296W; p<0.001) worsened. Despite increased ratings of perceived exertion and elevated blood lactate concentrations (p≤0.05), sprint times were maintained throughout exercise, whereas peak power increased (∼7.8%, +294W; p=0.006) pre- to post-exercise. ConclusionsAt the point of simulated pitch-entry, body temperature and physical performance responses were not maintained from warm-up cessation despite typical substitute-specific match-day practices being employed in thermoneutral conditions. Evidence of performance-limiting fatigue was absent during ∼30min of simulated match-play. These data question the efficacy of practices typically implemented by substitutes before pitch-entry.

Effect of post-exercise lactate administration on glycogen repletion and signaling activation in different types of mouse skeletal muscle.

Lactate is not merely a metabolic intermediate that serves as an oxidizable and glyconeogenic substrate, but it is also a potential signaling molecule. The objectives of this study were to investigate whether lactate administration enhances post-exercise glycogen repletion in association with cellular signaling activation in different types of skeletal muscle. Eight-week-old male ICR mice performed treadmill running (20 m/min for 60 min) following overnight fasting (16 h). Immediately after the exercise, animals received an intraperitoneal injection of phosphate-buffered saline or sodium lactate (equivalent to 1 g/kg body weight), followed by oral ingestion of water or glucose (2 g/kg body weight). At 60 min of recovery, glucose ingestion enhanced glycogen content in the soleus, plantaris, and gastrocnemius muscles. In addition, lactate injection additively increased glycogen content in the plantaris and gastrocnemius muscles, but not in the soleus muscle. Nevertheless, lactate administration did not significantly alter protein levels related to glucose uptake and oxidation in the plantaris muscle, but enhanced phosphorylation of TBC1D1, a distal protein regulating GLUT4 translocation, was observed in the soleus muscle. Muscle FBP2 protein content was significantly higher in the plantaris and gastrocnemius muscles than in the soleus muscle, whereas MCT1 protein content was significantly higher in the soleus muscle than in the plantaris and gastrocnemius muscles. The current findings suggest that an elevated blood lactate concentration and post-exercise glucose ingestion additively enhance glycogen recovery in glycolytic phenotype muscles. This appears to be associated with glyconeogenic protein content, but not with enhanced glucose uptake, attenuated glucose oxidation, or lactate transport protein.

Responses of a coral reef shark acutely exposed to ocean acidification conditions

Anthropogenic ocean acidification (OA) is a threat to coral reef fishes, but few studies have investigated responses of high-trophic-level predators, including sharks. We tested the effects of 72-hr exposure to OA-relevant elevated partial pressures of carbon dioxide (pCO2) on oxygen uptake rates, acid–base status, and haematology of newborn tropical blacktip reef sharks (Carcharhinus melanopterus). Acute exposure to end-of-century pCO2 levels resulted in elevated haematocrit (i.e. stress or compensation of oxygen uptake rates) and blood lactate concentrations (i.e. prolonged recovery) in the newborns. Conversely, whole blood and mean corpuscular haemoglobin concentrations, blood pH, estimates of standard and maximum metabolic rates, and aerobic scope remained unaffected. Taken together, newborn blacktip reef sharks appear physiologically robust to end-of-century pCO2 levels, but less so than other, previously investigated, tropical carpet sharks. Our results suggest peak fluctuating pCO2 levels in coral reef lagoons could still physiologically affect newborn reef sharks, but studies assessing the effects of long-term exposure and in combination with other anthropogenic stressors are needed.

90 Transient severe mitral regurgitation caused by an exclusively dopamine secreting paraganglioma

Abstract INTRODUCTION A 93 year old woman presented to the hospital because of severe dyspnea with a sudden onset. Her medical history was positive for a sick sinus syndrome for which she received a DDD pacemaker in 2014. Furthermore an intra-abdominal paraganglioma (PGL) was discovered a year earlier which was treated conservatively because of her age and lack of symptoms. On physical examination, a sinus rhythm of 88 bpm (pacemaker rhythm) and oxygen saturation of 80% was noted. Blood pressure was 66/38 mmHg. An urgent blood gas analysis showed an elevated blood lactate concentration of 5.5 mmol/l. Her signs and symptoms were compatible with a cardiogenic shock. Transthoracic echocardiography (TTE) revealed a notable hyperdynamic left ventricular (LV) function and a severe mitral regurgitation (MR) (ERO 0,7 cm2), based on restriction and tenting of both the anterior and posterior mitral leaflet with a systolic pulmonary artery pressure (PAPs) of 70mmHg + CVP. Because of her age and a written declaration of will, only a supportive therapy with oxygen and morphine was given. After 45minutes however, the patient suddenly and completely recuperated. Her vital signs stabilized with a blood pressure of 110/60 mmHg and oxygen saturation of 95%. A second TTE showed only a mild MR without any restriction of the mitral leaflets and a normalized PAPs of 30mmHg +CVP. The patient was hospitalized for further investigation. COURSE DURING HOSPITALIZATION During the next 48 hours, four similar episodes with acute dyspnea and signs and symptoms of cardiogenic shock were documented. Each time, TTE revealed a hyperdynamic LV function with a severe MR, based on tenting of both mitral valve leaflets. These episodes always terminated spontaneously with only a mild residual MR afterwards. An angiography was performed and showed no coronary lesions. DIFFERENTIAL DIAGNOSIS Because of the paroxysmal episodes, documentation of a hyperdynamic LV function with severe hypotension and the known PGL, a 24h urine collection was performed. The results demonstrated a markedly elevated urine dopamine concentration (5300 µg/l) with normal concentrations of adrenaline (3.5 µg/l) and noradrenaline (64.3 µg/l). 3-Methoxytyramine, the metabolite of dopamine, was also highly elevated (4700 µg/l). As such, the diagnosis of a dopamine producing PGL was made. The patient refused any treatment and she went home in a palliative setting. CONCLUSION Dopamine-secreting PGL is a very rare entity without a classic clinical presentation. This is the first case report showing a severe MR with cardiogenic shock, leading to the diagnosis of a dopamine secreting PGL. The mechanism of the MR is still unclear, but strain measurements did show an exacerbation of the RV pacing induced dyssynchrony during the episodes of shock, hypothesizing that dopamine release exacerbated the pacing induced asynchrony of the papillary muscles, leading to a functional MR.

Effects of lactate administration on mitochondrial enzyme activity and monocarboxylate transporters in mouse skeletal muscle.

Growing evidence shows that lactate is not merely an intermediate metabolite, but also a potential signaling molecule. However, whether daily lactate administration induces physiological adaptations in skeletal muscle remains to be elucidated. In this study, we first investigated the effects of daily lactate administration (equivalent to 1 g/kg of body weight) for 3 weeks on mitochondrial adaptations in skeletal muscle. We demonstrated that 3‐week lactate administration increased mitochondrial enzyme activity (citrate synthase, 3‐hydroxyacyl CoA dehydrogenase, and cytochrome c oxidase) in the plantaris muscle, but not in the soleus muscle. MCT1 and MCT4 protein contents were not different after 3‐week lactate administration. Next, we examined whether lactate administration enhances training‐induced adaptations in skeletal muscle. Lactate administration prior to endurance exercise training (treadmill running, 20 m/min, 60 min/day), which increased blood lactate concentration during exercise, enhanced training‐induced mitochondrial enzyme activity in the skeletal muscle after 3 weeks. MCT protein content and blood lactate removal were not different after 3‐week lactate administration with exercise training compared to exercise training alone. In a single bout experiment, lactate administration did not change the phosphorylation state of AMPK, ACC, p38 MAPK, and CaMKII in skeletal muscle. Our results suggest that lactate can be a key factor for exercise‐induced mitochondrial adaptations, and that the efficacy of high‐intensity training is, at least partly, attributed to elevated blood lactate concentration.

An equation to predict the maximal lactate steady state from ramp-incremental exercise test data in cycling

ObjectivesThe maximal lactate steady state (MLSS) represents the highest exercise intensity at which an elevated blood lactate concentration ([Lac]b) is stabilized above resting values. MLSS quantifies the boundary between the heavy-to-very-heavy intensity domains but its determination is not widely performed due to the number of trials required. DesignThis study aimed to: (i) develop a mathematical equation capable of predicting MLSS using variables measured during a single ramp-incremental cycling test and (ii) test the accuracy of the optimized mathematical equation. MethodsThe predictive MLSS equation was determined by stepwise backward regression analysis of twelve independent variables measured in sixty individuals who had previously performed ramp-incremental exercise and in whom MLSS was known (MLSSobs). Next, twenty-nine different individuals were prospectively recruited to test the accuracy of the equation. These participants performed ramp-incremental exercise to exhaustion and two-to-three 30-min constant-power output cycling bouts with [Lac]b sampled at regular intervals for determination of MLSSobs. Predicted MLSS (MLSSpred) and MLSSobs in both phases of the study were compared by paired t-test, major-axis regression and Bland–Altman analysis. ResultsThe predictor variables of MLSS were: respiratory compensation point (Wkg−1), peak oxygen uptake (V˙O2peak) (mlkg−1min−1) and body mass (kg). MLSSpred was highly correlated with MLSSobs (r=0.93; p<0.01). When this equation was tested on the independent group, MLSSpred was not different from MLSSobs (234±43 vs. 234±44W; SEE 4.8W; r=0.99; p<0.01). ConclusionsThese data support the validity of the predictive MLSS equation. We advocate its use as a time-efficient alternative to traditional MLSS testing in cycling.

Assessment of Metabolic Flexibility by Means of Measuring Blood Lactate, Fat, and Carbohydrate Oxidation Responses to Exercise in Professional Endurance Athletes and Less-Fit Individuals.

Increased muscle mitochondrial mass is characteristic of elite professional endurance athletes (PAs), whereas increased blood lactate levels (lactatemia) at the same absolute submaximal exercise intensities and decreased mitochondrial oxidative capacity are characteristics of individuals with low aerobic power. In contrast to PAs, patients with metabolic syndrome (MtS) are characterized by a decreased capacity to oxidize lipids and by early transition from fat to carbohydrate oxidation (FATox/CHOox), as well as elevated blood lactate concentration [La-] as exercise power output (PO) increases, a condition termed 'metabolic inflexibility'. The aim of this study was to assess metabolic flexibility across populations with different metabolic characteristics. We used indirect calorimetry and [La-] measurements to study the metabolic responses to exercise in PAs, moderately active individuals (MAs), and MtS individuals. FATox was significantly higher in PAs than MAs and patients with MtS (p<0.01), while [La-] was significantly lower in PAs compared with MAs and patients with MtS. FATox and [La-] were inversely correlated in all three groups (PA: r=-0.97, p<0.01; MA: r=-0.98, p<0.01; MtS: r=-0.92, p<0.01). The correlation between FATox and [La-] for all data points corresponding to all populations studied was r=-0.76 (p<0.01). Blood lactate accumulation is negatively correlated with FATox and positively correlated with CHOox during exercise across populations with widely ranging metabolic capabilities. Because both lactate and fatty acids are mitochondrial substrates, we believe that measurements of [La-] and FATox rate during exercise provide an indirect method to assess metabolic flexibility and oxidative capacity across individuals of widely different metabolic capabilities.

Metabolic and cardiovascular responses during voluntary pedaling exercise with electrical muscle stimulation.

We aimed to test the effect of additional electrical muscle stimulation (EMS) during moderate-intensity voluntary pedaling exercise on metabolic and cardiovascular responses. Eleven healthy male subjects performed moderate-intensity pedaling exercise at a constant workload (80% of ventilatory threshold) for 20 min while EMS was applied to thigh muscles from 5 to 10 min and from 15 to 20 min during the exercise. A significantly higher oxygen uptake (VO₂), heart rate, and respiratory gas exchange ratio were observed during the exercise periods with EMS despite the constant workload. These changes were accompanied by an elevated blood lactate concentration, suggesting the existence of additional fast-twitch motor unit (MU) recruitment during the exercise with EMS. Our data suggest that the use of intermittent EMS during a constant load exercise mimics the high-intensity interval training, possibly due to additional fast-twitch MU recruitment and co-contractions of the quadriceps and hamstrings muscles, leading to higher anaerobic metabolism and a lower mechanical efficiency.

Resuscitation of patients with septic shock: please “mind the gap”!

Resuscitation of patients with septic shock: please “mind the gap”!

Effect Of Two Sampling Sites On Resting Blood Lactate Concentration

Lactate has been used to evaluate exercise intensity and physiological performance. Most research has utilized rest times prior to exercise from 5 minutes to as long as 30 minutes before initial blood samples were obtained. However, blood lactate concentration differs between sample sites and inactive muscle serves as a passive sink for lactate disposal during exercise. Therefore, it is unclear if these phenomena are present when measuring resting blood lactate concentration. PURPOSE: To determine the effect of two different sampling sites on resting blood lactate concentrations. METHODS: Twenty nine (13 males, 16 females) subjects volunteered to participate in the study. After anthopometric data was collected, subjects assumed a supine position. The ring finger of the non-dominant hand and great toe on the ipsilateral side were prepped for blood sampling. After laying supine for 5 minutes, 50 μl blood samples in heperanized capillary tubes were obtained from each site simultaneously. Samples were immediately analyzed using two YSI 1500 Sport lactate analyzers. Samples were collected and analyzed every 5 minutes for the duration. RESULTS: The mean + SD for the finger at each sample time were 1.95+1.19, 1.76+1.13, 1.54+.94, 1.33+.76,.96+.47,.93+.45. The mean + SD for the toe at each sample time were 1.28+.48, 1.03+.45, 1.01+.48,.92+.37,.88+.33,.92+.33. All three analyses were significant (p < 0.05) with the sample site X sample time interaction, sample time main effect, and sample site main effect being reported, respectively: p = 0.004, p = 0.000, and p = 0.001. Post-hoc paired t-tests on computed mean differences between sample sites for each time revealed differences (p < 0.05) between several time intervals. Further analysis also revealed differences (p < 0.05) in the sample site main effect at each time. CONCLUSION: Based on these findings, if true baseline lactate concentrations are needed, then at least 20 minutes of rest is required to negate an elevated blood lactate concentration caused by activities of daily living. As well, if multiple sampling sites are utilized, then subjects need to rest for at least 20 minutes to allow blood lactate concentrations between sites to equilibrate.

Lactate infusion at rest increases BDNF blood concentration in humans

Studies in humans use blood lactate to determine the degree of the exercise intensity, suggesting that exercise with elevated blood lactate concentrations results in increased BDNF plasma concentrations. However, it is not clear if lactate per se or rather other mechanisms are responsible for changes in blood BDNF concentrations. The lactate clamp method at rest is an appropriate method to examine physiological responses of lactate on the human organism without the effects of exercise. Eight male sport students placed in a sitting position received intravenous infusions with a 4 molar sodium-lactate solution in an incremental design starting with an infusion rate of 0.01 ml/kgBW/min for the first three minutes, which was increased every three minutes by 0.01 ml/kgBW/min up to 0.08 ml/kg/min in the 24th minute. All together each subject received 4.2 mmol of infusion. Venous blood samples were taken before and immediately after the infusion as well as in the 24th and the 60th min after the infusion period and analysed for BDNF. Blood gases and capillary blood lactate (La) were analysed before the test, every three minutes directly before increasing the infusion rate, at the end of the infusion and in the post infusions period until the 12th min and after 24 and 60 min. BDNF and La increased significantly after the infusion and reached baseline values at the end of the experiment ( p < 0.05, p < 0.01, respectively). pH and hydrogen ions increased from the beginning until the end of the infusion period ( p < 0.01). This data suggest that blood lactate is involved in the regulation of BDNF blood concentrations.

Lactate response to short term exercise with elevated starting levels

A model that describes the blood lactate concentration (BLC) dynamics [BLC(t)] of a Wingate Anaerobic Test (WAnT) as a function of (a) BLC at the start of exercise (BLC(0)), (b) extra-vascular increase in lactate (A), (c) two corresponding velocity constants of appearance (k (1)) and disappearance (k (2)) of lactate into and out of the blood requires that BLC(0) is equal to resting BLC (BLC(rest)). We developed a model that considers an elevated BLC(0). 19 males performed WAnTs with warm-ups increasing (p < 0.001) BLC(0). The goodness of each individual fit improved (p < 0.05) if the difference between BLC(rest) and BLC(0) (DeltaBLC) was higher than 1.0 mmol l(-1). All differences between old and new model (p < 0.05) in A, k (1) and k (2) were interrelated with and increased with DeltaBLC (p < 0.05). The new model well describes BLC(t) and prevents substantial errors concerning lactate generation and dynamics if BLC(0) is elevated by more than 1.0 mmol l(-1).

Biomechanically Influenced Differences in O2 Extraction in Diagonal Skiing

This study aimed to determine whether the differences in oxygen extraction and lactate concentration in arms and legs during cross-country skiing are related to muscle activation or force production and how these differences are influenced by a reduction in exercise intensity. Nine well-trained male cross-country skiers (age = 22 +/- 3 yr, V˙O2max = 5.3 +/- 0.3 L min(-1) and 69 +/- 3 mL kg(-1) min(-1)) performed diagonal skiing on a treadmill for 3 min at 90% followed by 6 min at 70% of V˙O2max. During the final minute of each workload, arterial, femoral, and subclavian venous blood was collected for determination of blood gases, pH, and lactate. EMG was recorded from six upper- and lower-body muscles, and leg and pole forces were measured. Cardiorespiratory variables were monitored continuously. Oxygen extraction in the legs was higher than that in the arms at both 90% and 70% of V˙O2max (92% +/- 3% vs 85% +/- 6%, P < 0.05 and 90% +/- 3% vs 78% +/- 8%, P < 0.001). This reduction with decreased workload was more pronounced in the arms (-9.8% +/- 7.7% vs -3.2% +/- 3.2%, P < 0.01). EMG(RMS) for the arms was higher, and pole ground contact time was greater than the corresponding values for the legs (both P < 0.01). At both intensities, the blood lactate concentration was higher in the subclavian than that in the femoral vein but was lowered more in the subclavian vein when intensity was reduced (all P < 0.001). The higher muscle activation (percentage of maximal voluntary isometric contraction) in the arms and the longer ground contact time of the poles than the legs contribute to the lower oxygen extraction and elevated blood lactate concentration in the arms in diagonal skiing. The better lactate recovery in the arms than that in the legs is aided by greater reductions in muscle activation and pole force when exercise intensity is reduced.

Perinatal palliative care or termination of pregnancy after prenatal diagnosis of lethal fetal abnormality

Moderate to severe encephalopathy developed in 28 (33%) and 10 (11.9%) infants, respectively; all with severe encephalopathy died. First postnatal blood lactate concentrations, measured at a median (IQR) age of 65 min (38–119 min), ranged from 0.5 to 42.7 mmol/l. All infants with first lactate of <12 mmol/l survived but 24% of those with values above this died. Median (IQR) first postnatal blood lactate concentration was significantly higher among infants with moderate to severe encephalopathy than among those with no or mild encephalopathy [19 (14.6–22) vs. 8.4 (5.22–12.5); p<0.0001]. Blood lactate concentration showed similar discriminating ability for prediction of moderate to severe encephalopathy as the first postnatal pH or base excess [area under ROC curve – 0.88 (S.E.=0.04), 0.78 (S.E.=0.06) and 0.82 (S.E.=0.06), respectively}. The sensitivity, specificity, positive and negative predictive values of first postnatal blood lactate concentration of ≥12 mmol/l for moderate to severe encephalopathy were 92%, 67%, 58% and 95%, respectively, the corresponding values for a composite predictor (5-min Apgar score≤5, or pH<7.0, or base excess≤−16 mmol/l) being 93%, 39%, 43% and 92%, respectively. Lactate concentration of ≥12 mmol/l correctly classified 75% of infants compared to 57% when the composite predictor was present. Conclusions: Elevated blood lactate concentration during the first 3 h after birth is a significant predictor of moderate to severe encephalopathy, similar to that reported by Shah et al. [1]. The relationship between early hyperlactatemia and long-term neurodevelopmental outcome remains to be determined. Reference [1] Shah S, et al. J Perinatol 2004;24:16–20.