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PubMedDate not supplied

Bicarbonate versus lactate buffer in peritoneal dialysis solutions: the beneficial effect on RBC metabolism.

OBJECTIVE: Using the erythrocyte as a model for other kinds of cells not directly exposed to peritoneal dialysis (PD) solutions, we investigated the tolerance of the cell metabolism to lactate and bicarbonate buffers. DESIGN: We studied, in vivo (in two groups of 5 PD patients each) and in vitro, the Embden-Meyerhof pathway (EMP) because it represents a potential target for the unphysiological effects of lactate or bicarbonate buffers. The EMP is the main glucose-utilizing route in the red blood cell (RBC), producing energy and reducing power. METHODS: The enzymatic activities of the key steps in the glycolytic pathway and the energy charge (EC), determined by the levels of phosphorylated adenine nucleotides, were investigated spectrophotometrically and by high performance liquid chromatography (HPLC) in two groups of patients undergoing lactate (L-group) and bicarbonate (B-group) PD, respectively. The in vitro effects of both bicarbonate and lactate buffers on some EMP enzyme activities and energy production were determined. Cellular pH (pHi) was also investigated. RESULTS: The B-group showed an EC value near the control levels, while in the L-group a significantly lower EC value was observed (t-test: p < 0.05 vs both B-group and controls). The key enzymes in the EMP, and in particular hexokinase, were higher in the L-versus B-group (p < 0.03 for the comparison of the Hk mean values). As demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, the bound form of glyceraldehyde-3-phosphate dehydrogenase (G-3-PD), an inactive form of this EMP enzyme, was significantly higher in the L-group with respect to the B-group (p < 0.004). In the in vitro experiments, high lactate concentrations acutely inhibited the key enzymatic steps of glycolysis, producing a significant decrease in glucose consumption and adenosine triphosphate production. These effects were not observed when bicarbonate was used in the incubations. Both in vivo and in vitro lactate, but not bicarbonate, induce a significant drop in pHi (p < 0.05). Decreased levels of pHi like those observed in the lactate-incubated RBC were demonstrated to be able to inhibit G-3-PD activity (25 +/- 2%) here used as an indicator of the actual decrease in pH. CONCLUSION: This study provides evidence for a damaging action of lactate with respect to bicarbonate buffer on the RBC metabolism. This condition was demonstrated observing a cell energy depletion, which coincides in vitro with an acute EMP impairment; the lactate accumulation together with the consequent lowering of pHi seem to be responsible for this effect, which was not observed when bicarbonate was used instead of lactate.

Adenine Nucleotides↗
PubMed1997

Association between lactation length and sow reproductive performance and longevity.

OBJECTIVE: To determine whether lactation length was associated with reproductive performance or longevity of sows. DESIGN: Cohort study. SAMPLE POPULATION: Data collected between 1986 and 1992 for sows in 15 breeding herds in Minnesota and Iowa. PROCEDURE: Sows were grouped into 4 genetic line categories according to their sources and 6 parity categories (1, 2, 3, 4, 5 or 6, and > or = 7). Multivariate regression analysis of reproductive performance was conducted, using the general linear model procedure Logistic regression was conducted with a dichotomous response variable for sow longevity (ie, removal from or retention in the herds). Odds ratios were obtained from estimated coefficients of the regression. RESULTS: Herd, genetic line, parity, year, month, and lactation length were significant in statistical models for litter (eg, number of live pigs/litter) and interval (eg, weaning-to-mating interval) traits. Interactions between lactation length and year, lactation length and genetic line, lactation length and parity, and lactation length and genetic line and parity were also significant. Sows removed from herds had a significantly shorter lactation length than did sows of the same parity that were retained in the herds. Sows that had shorter lactation lengths were at higher risk of being removed from the herds than were those that had longer lactation lengths. CLINICAL IMPLICATIONS: Lactation length is associated with reproductive performance and longevity, but genetic line and parity play a role as well. Thus, attention should be paid to genetic lines and parity of sows in the herd when implementing an early weaning production practice.

Animals↗
PubMedDate not supplied

[The effect of lactation during the reproductive age on bone mass in postmenopause].

One of the factors of the reproductive status which affects bone mass of women in the generative period is duration of lactation. The aim of this study was to establish if duration of lactation affects bone mass of postmenopausal women. 81 women up to 5 years of menopause were examined. They were divided into two groups in regard to lactation duration. The first group consisted of those who breast-fed for up to 12 months, while the second group consisted of those who had breast-fed longer than 12 months. In all examined women lumbar bone mineral density was measured using photon absorptiometry. No statistically significant difference was established in the lumbar bone mineral density in the examined groups (0.902 +/- 0.104 g/cm2 to 0.915 +/- 0.127 g/cm2; p < 0.30). In order to eliminate the protective effects of obesity on bone mass all examinees were divided into 4 subgroups: a) nonobese women with up to 12 months of lactation; b) nonobese women with lactation longer than 12 months. c) obese women with up to 12 months of lactation and d) obese women with lactation longer than 12 months. Lumbar bone mineral density of nonobese women, no matter the duration of lactation, did not statistically significantly differ (0.892 +/- 0.107 g/cm2 to 0.900 +/- 0.116 g/cm2; p < 0.40). No statistically significant difference in regard to lumbar bone mineral density was established in the group of obese women, no matter the duration of lactation (0.912 +/- 0.103 g/cm2 to 0.930 +/- 0.139 g/cm2; p < 0.30). The obtained results reveal that bone mass reduction is reversible in the postpartal period and that duration of lactation does not affect bone mass in the postmenopausal period.

Absorptiometry, Photon↗
PubMed1996

Intracoronary papaverine induced myocardial lactate production in patients with angiographically normal coronary arteries.

Although intracoronary papaverine has been widely used for the measurement of coronary flow reserve, little is known concerning whether papaverine may produce deleterious metabolic changes in humans. We investigated the effect of papaverine on lactate metabolism in 28 patients with normal coronary arteries. We continuously monitored phasic coronary flow velocity in the proximal left anterior descending coronary artery using Doppler guidewire. We also obtained paired samples of arterial and coronary sinus blood for the measurement of lactate at control and at 1 min after administration of 10 mg of intracoronary papaverine. There were no serious side effects during papaverine infusion. Sixteen patients showed ST-T abnormalities after papaverine. The QTc interval increased from 450 +/- 42 msec to 571 +/- 58 msec (P < 0.001). Average peak velocity increased significantly (% increase: 198.5 +/- 87.8%, range: 27.8-374.1%) after papaverine. Although intracoronary papaverine produced no significant change in arterial lactate levels (8.5 +/- 4.0-8.8 +/- 5.0 mg/ml), it induced a significant increase in coronary sinus lactate levels (5.4 +/- 3.2-15.3 +/- 8.2 mg/ml, P < 0.001). Lactate extraction ratio decreased significantly (36.4 +/- 18.4--82.2 +/- 58.4%, P < 0.001), and all patients showed net lactate production (-3.9--198.0%) after papaverine. There was weak but significant correlation between lactate extraction ratio after papaverine and coronary flow reserve (R2 = 0.15, P < 0.05). There was no correlation between lactate extraction ratio and QTc interval after papaverine. The mean value of lactate extraction ratio was not different in patients with ST-T abnormalities induced by papaverine compared to those without. These results demonstrate that intracoronary papaverine induces myocardial lactate production irrespective of the degree of coronary flow reserve and electrocardiographic changes in patients with normal coronary arteries. A safer and more reliable agent is needed for the measurement of coronary flow reserve.

Adult↗
PubMed2001

Effect of exogenous lactate on rat glioma metabolism.

Glioma-bearing rats were infused intravenously with a solution containing either [3-(13)C]lactate or both glucose and [3-(13)C]lactate for 20 min or 1 hr. Perchloric acid extracts of healthy and tumoral brain tissues were prepared and analyzed by (13)C- and (1)H-observed (13)C-edited nuclear magnetic resonance (NMR) spectroscopy to determine (13)C-label incorporation into brain tissue and glioma metabolites. Moreover, (13)C enrichments in blood lactate and glucose were determined from (1)H-NMR spectra. In the nontumoral tissue, (13)C labeling of amino acids indicated that [3-(13)C]lactate entered the brain and was metabolized. There was no labeling difference between the contralateral and the ipsilateral hemispheres. Lactate metabolism appeared more specifically neuronal, in agreement with our previous results obtained with normal rat brain (Bouzier et al. [2000] J. Neurochem. 75:480-486). In the glioma tissue, comparison of Ala C3, Glu C4, and Gln C4 labeling indicated that the contributions of blood glutamine and tricarboxylic acid (TCA) cycle to glutamate labeling were about 80% and 20%, respectively, after 1 hr of [3-(13)C]lactate infusion. In contrast, these contributions were about 10% and 90%, respectively, when [1-(13)C]glucose was infused in the absence of lactate. This indicated a major effect of the exogenous lactate on glioma metabolism, which may be due to the following process: The high blood lactate level might hinder the drain of glycolytic lactate produced inside the glioma and thus generate a change in redox potential such that the tumor cells are unable to restore it with oxidative phosphorylation. Thereafter, the high NADH level might inhibit glycolysis and the TCA cycle, and glutamine could become the major carbon source for glutamate labeling.

Animals↗
PubMed1996

Initial postoperative serum lactate levels predict survival in children after open heart surgery.

OBJECTIVE: To evaluate the relationship between postoperative serum lactate levels and outcome in children undergoing open heart surgery. DESIGN: Prospective, noninterventional study. SETTING: Pediatric intensive care unit (PICU) of a university hospital. PATIENTS: 41 nonconsecutive children who had had cardiopulmonary bypass for repair of congenital heart disease. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Serum lactate levels were measured on admission to the PICU immediately after open heart surgery. Lactate levels were correlated with bypass and cross clamp times, estimated intraoperative blood loss, lowest temperature on bypass, admission Pediatric Risk of Mortality score, anion gap, and measures of postoperative morbidity. Mean lactate levels on admission to the PICU were 6.86 +/- 0.79 mmol/l for nonsurvivors (n = 7) and 2.38 +/- 0.13 mmol/l for survivors (n = 34) (p < 0.0001), and 4.87 +/- 0.7 mmol/l and 2.35 +/- 0.19 mmol/l, for patients with (n = 11) and without (n = 30) multiple organ system failure, respectively (p < 0.0001). Admission lactate levels correlated with all measurements of postoperative morbidity. A serum lactate level of greater than 4.2 mmol/l had a positive predictive value of 100% and a negative predictive value of 97% for postoperative death. CONCLUSIONS: Initial postoperative serum lactate levels after pediatric open heart surgery may be predictive of outcome. Lactate levels are also higher in patients who go on to develop multiple organ system failure. Elevated postoperative lactate levels may reflect intraoperative tissue hypoperfusion, and measures aimed at increasing oxygen delivery, with normalization of lactate, may improve patient outcome.

Adolescent↗
PubMed1999

Alternative schemes of butyrate production in Butyrivibrio fibrisolvens and their relationship to acetate utilization, lactate production, and phylogeny.

Butyrivibrio fibrisolvens strains D1 and A38 produced little lactate, but strain 49 converted as much as 75% of its glucose to lactate. Strain 49 had tenfold more lactate dehydrogenase activity than strains D1 or A38, this activity was stimulated by fructose 1,6-bisphosphate, and had a pH optimum of 6.25. A role for fructose 1,6-bisphosphate or pH regulation of lactate production in strain 49 was, however, contradicted by the observations that very low concentrations (< 0.2 mM) of fructose 1,6-bisphosphate gave maximal activity, and continuous cultures did not produce additional lactate when the pH was decreased. The lactate production of strain 49 was clearly inhibited by the presence of acetate in the growth medium. When strain 49 was supplemented with as little as 5 mM acetate, lactate production decreased dramatically, and most of the glucose was converted to butyrate. Strain 49 did not possess butyrate kinase activity, but it had a butyryl-CoA/acetate CoA transferase that converted butyryl-CoA directly to butyrate, using acetate as an acceptor. The transferase had a low affinity for acetate (K(m) of 5 mM), and this characteristic explained the acetate stimulation of growth and butyrate formation. Strains D1 and A38 had butyrate kinase but not butyryl-CoA/acetate CoA transferase, and it appeared that this difference could explain the lack of acetate stimulation and lactate production. Based on these results, it is unlikely that B. fibrisolvens would ever contribute significantly to the pool of ruminal lactate. Since relatives of strain 49 (strains Nor37, PI-7, VV1, and OB156, based on 16S rRNA sequence analysis) all had the same method of butyrate production, it appeared that butyryl-CoA/acetate CoA transferase might be a phylogenetic characteristic. We obtained a culture of strain B835 (NCDO 2398) that produced large amounts of lactate and had butyryl-CoA/acetate CoA transferase activity, but this strain had previously been grouped with strains A38 and D1 based on 16S rRNA sequence analysis. Our strain B835 had a 16S rRNA sequence unique from the one currently deposited in GenBank, and had high sequence similarity with strains 49 and Nor37 rather than with strains A38 or D1.

Acetates↗
PubMed2005

Elevated lactate as an early marker of brain injury in inflicted traumatic brain injury.

BACKGROUND: Traumatic brain injury is a major cause of disability and death in the pediatric population. The metabolic and neurochemical abnormalities that underlie traumatic brain injury remain poorly understood, but hypoxia-ischemic injury might play an important role. OBJECTIVE: This study evaluated children with inflicted traumatic brain injury using magnetic resonance spectroscopy (MRS). We postulated that children with hypoxic-ischemic injury indicated by elevated lactate in the acute phase of injury will have worse early neurological status and short-term clinical outcomes than those without lactate upon MRS. MATERIALS AND METHODS: This prospective study employed proton MRS to sample bilaterally the frontal lobes and the parasagittal cortex within the parietal and occipital lobes of 11 patients with inflicted traumatic brain injury who were undergoing a clinical MRI examination. Patients' measured clinical course while hospitalized included initial neurological evaluation, presence of seizure activity, need for admission to the pediatric intensive care unit (PICU), number of days hospitalized, presence of retinal hemorrhages and presence of bone fractures. Measurement of outcome was determined using the Pediatric Overall Performance Category Scale (POPCS; 1=good performance; 6=death). RESULTS: Four children demonstrated elevated lactate and diminished N-acetyl aspartate (a neuronal marker) within several regions, indicating global ischemic injury (lactate-positive global group). These four children all had seizure activity and abnormal initial neurological examinations and required admission to the PICU. The mean POPCS for this group was 3.25. In four other children, lactate was detected within at least one region, indicating a focal ischemic injury (lactate-positive focal group); two of these children had seizure activity, and two had an abnormal initial neurological examination. The mean POPCS score was 1.5 for this group. The remaining three children had no evidence of lactate upon MRS (lactate-negative group). These children did not have seizure activity, did not require admission to the PICU, nor did they have initial abnormal neurological examinations. The mean POPCS score was 1.3 for this group. SUMMARY: Patients with inflicted traumatic brain injury and evidence of hypoxic-ischemic injury as indicated by elevated lactate on MRS tend to have worse early neurological status and early outcome scores. Lactate levels as sampled by MRS might predict early clinical outcome in inflicted traumatic brain injury.

Aspartic Acid↗
PubMed2001

Blood lactate exchange and removal abilities after relative high-intensity exercise: effects of training in normoxia and hypoxia.

The effects of 4 weeks of endurance training in conditions of normoxia or hypoxia on muscle characteristics and blood lactate responses after a 5-min constant-load exercise (CLE) at 90% of the power corresponding to the maximal oxygen uptake were examined at sea-level in 13 sedentary subjects. Five subjects trained in normobaric hypoxia (HT group, fraction of oxygen in inspired gas = 13.2%), and eight subjects trained in normoxia at the same relative work rates (NT group). The blood lactate recovery curves from the CLE were fitted to a biexponential time function: La(t) = La(0) + A1(1 - e- gamma 1.t) + A2(1 - e- gamma 2.t), where the velocity constants gamma 1 and gamma 2 denote the lactate exchange and removal abilities, respectively, A1 and A2 are concentration parameters that describe the amplitudes of concentration variations in the space represented by the arterial blood, La(t) is the lactate concentration at time t, and La(0) is the lactate concentration at the beginning of recovery from CLE. Before training, the two groups displayed the same muscle characteristics, blood lactate kinetics after CLE, and gamma 1 and gamma 2 values. Training modified their muscle characteristics, blood lactate kinetics and the parameters of the fits in the same direction, and proportions among the HT and the NT subjects. Endurance training increased significantly the capillary density (by 31%), citrate synthase activity (by 48%) and H isozyme proportion of lactate dehydrogenase (by 24%), and gamma 1 (by 68%) and gamma 2 (by 47%) values. It was concluded that (1) endurance training improves the lactate exchange and removal abilities estimated during recovery from exercises performed at the same relative work rate, and (2) training in normobaric hypoxia results in similar effects on lactate exchange and removal abilities to training in normoxia performed at the same relative work rates. These results, which were obtained non-invasively in vivo in humans during recovery from CLE, are comparable to those obtained in vitro or by invasive methods during exercise and subsequent recovery.

Adult↗
PubMed1998

Noninvasive skeletal muscle lactate detection between periods of intense exercise in humans.

We investigated whether localized 1H nuclear magnetic resonance spectroscopy (NMRS) using stimulated echoes (STEAM) with a long mixing time (t(m)) allowed the suppression of the fat signal and detection of lactate in skeletal muscle. The 1H NMRS sequence was first validated in three isolated and perfused rabbit biceps brachii muscles. Spectra were obtained on a wide-bore spectrometer using a dual-tuned probe (1H and 31P). Death was simulated by ceasing the muscle perfusion, which allowed post-mortem changes to be followed. During and after the simulated death, changes in levels of pH and in content of energy-rich compounds were observed with 31P NMRS. Our results showed an inverse linear relationship between pH and lactate in each of the three rabbits (r = 0.93, P < 0.001; r = 0.92, P < 0.01; r = 0.89, P < 0.01) and a decrease in phosphocreatine and concomitant increase in lactate. We then investigated whether this sequence allowed repeated detection of lactate in human soleus muscle during the recovery between periods of intense exercise (force-velocity test, F-v test). Seven subjects mean age 25.1 (SEM 0.8) years participated in this study. Soleus muscle lactate was detected at rest and for 3 min 30 s of the 5-min recovery between periods using a 2.35-T 40-cm bore magnet spectrometer. Arm venous plasma lactate concentration was measured at rest, during the F-v test when the subject stopped pedalling (S1), and at the end of each 5-min recovery between periods (S2). Results showed that the venous plasma lactate concentration at S1 and S2 increased significantly from the beginning of the F-v test to peak anaerobic power (W(an,peak)) (P < 0.001). The spectra showed that muscle lactate resonance intensity rose markedly when W(an,peak) was achieved. The muscle lactate resonance intensity plotted as a percentage of the resting value increased significantly at W(an,peak) compared with submaximal braking forces (P < 0.05). We concluded from these results that localized 1H NMRS using STEAM with a long t(m) allows suppression of the fat signal and repeated detection of lactate on isolated perfused skeletal muscle in animals and between periods of intense exercise in humans.

Adult↗
PubMed1989

Relationships between fertility, peak milk yields and lactational persistency in dairy cows.

Peak milk yield, lactational persistency and conception rates were studied using 5928 lactation records of high milk-producing cows at three California dairies. Log-linear analysis was used to study relationships between peak milk yield, lactational persistency, dairy of origin, lactation number and conception rates in 3850 completed lactations. Cows with peak milk yields greater than the median (38.2 kg milk per day) were less likely to have conceived in one or two breedings than cows with peak milk yields lower than or equal to the median. Cows with a higher than median (0.755) lactational persistency were less likely to have conceived in one or two breedings than cows with a lactational persistency lower than or equal to the median. Dairy of origin had a significant effect on the probability of conceiving in one or two breedings. Cows in the first lactation were more likely than those in subsequent lactations to conceive in one or two breedings. This retrospective study demonstrated that subfertility is associated with high peak lactational yields in high milk-producing California cows.

Journal Article↗
PubMed2005

Serum lactate as a predictor of mortality in emergency department patients with infection.

STUDY OBJECTIVE: Little is known about risk-stratification biomarkers in emergency department (ED) patients with suspected infection, and lactate is a biologically plausible candidate. We determine whether a serum venous lactate is associated with an increased risk of death in ED patients with infection. METHODS: This was a prospective cohort study in an urban, academic medical center with 50,000 annual ED visits. A total of 1,278 consecutive patient visits met enrollment criteria between July 24, 2003, and March 24, 2004, and all patients were enrolled. Inclusion criteria were age 18 years or older, serum lactate level obtained, and admission to the hospital with an infection-related diagnosis. The main outcome measure was all-cause 28-day inhospital mortality and death within 3 days of presentation. RESULTS: Among 1,278 patient visits, there were 105 (8.2%) deaths during hospitalization, with 55 (4.3%) of 1,278 deaths occurring in the first 3 days. Mortality rates increased as lactate increased: 43 (4.9%) of 877 of patients with a lactate level between 0 and 2.5 mmol/L died, 24 (9.0%) of 267 patients with a lactate level between 2.5 and 4.0 mmol/L died, and 38 (28.4%) of 134 patients with a lactate level greater than or equal to 4.0 mmol/L died. Lactate level greater than or equal to 4.0 mmol/L was 36% (95% confidence interval [CI] 27% to 45%) sensitive and 92% (95% CI 90% to 93%) specific for any death; it was 55% (95% CI 41% to 68%) sensitive and 91% (95% CI 90% to 93%) specific for death within 3 days. CONCLUSION: In this cohort of ED patients with signs and symptoms suggestive of infection, our results support serum venous lactate level as a promising risk-stratification tool. Multicenter validation, as well as comparison of the lactate level with clinical predictors, needs to be done before widespread implementation.

Adult↗
PubMed2005

Patterns of lactate values after congenital heart surgery and timing of cardiopulmonary support.

BACKGROUND: We sought to determine if postoperative serial lactate determinations follow predictable patterns that could be useful in directing management, especially the initiation of postoperative mechanical cardiopulmonary support (CPS). METHODS: Eight patients undergoing CPS in a 2-year period and 147 patients not requiring postoperative CPS in 6 months of that period were stratified into 6 categories based on short-term risk for mortality (1 being the lowest risk). Lactate values for the first 48 hours postoperatively were retrospectively analyzed. RESULTS: Survivors not requiring CPS in category 6 (n = 16) followed a distinct pattern different from those of categories 1 through 4 (n = 128). Review of postoperative CPS survivors (n = 4) indicated that CPS was initiated electively without cardiac arrest in all 4, and lactate values showed a downward trend within 12 hours of initiation in all cases (mean lactate, 10.12 +/- 1.88 mmol/L; range, 1.4 to 16 mmol/L; mean initiation time, 16.5 hours postoperatively). Three fourths of the CPS nonsurvivors suffered cardiac arrest before CPS and showed rising lactate values despite support (mean lactate, 11.95 +/- 1.37 mmol/L; range, 1.6 to 18.6 mmol/L; mean initiation time, 21.25 hours postoperatively). Indications for initiation of CPS in patients with elevated lactate values were reviewed. Two thirds of patients who died without CPS had preterminal cardiac arrest. CONCLUSIONS: We have defined the normal pattern of postoperative lactate values in our institution. These data suggest that an abnormal lactate pattern may be useful in determining the timing of CPS initiation in hemodynamically stable patients with high or rising lactate values, before cardiac arrest or end organ damage.

Cardiopulmonary Resuscitation↗
PubMed2006

Lactate uptake by skeletal bone in anoxic turtles, Trachemys scripta.

Previous studies have shown that freshwater turtle shells can accumulate lactate during periods of anoxic submergence. Our objective in this study was to determine lactate uptake in other parts of the turtle's skeleton. We measured lactate concentration of 7 skeletal elements and 4 shell samples of red-eared slider turtles, Trachemys scripta, in control animals (N=12) and in animals following submergence for 4-5 days in N(2)-equilibrated water at 10 degrees C (N=8). We also collected blood samples and measured blood pH, PCO(2), and PO(2), and plasma lactate. Contralateral bone samples from 6 control turtles were analyzed for % water and mineral composition; bone from the other 6 were equilibrated with lactate solution in vitro. Anoxic submergence resulted in a combined respiratory/non-respiratory (lactic) acidosis and plasma lactate of 45.6+/-2.5 mmol l(-1). Shell and skeletal lactates all increased significantly in the anoxic animals (30.1-43.9 mmol kg(-1)) with limb bones having the highest levels and skull the least. Skeletal samples equilibrated in lactate solution in vitro for 2 days accumulated lactate in similar fashion with limb bones, except for fibula, higher, and skull significantly less than other bones. We conclude that the entire skeleton of the red-eared slider, like its shell, sequesters lactate and contributes thereby to lactic acid buffering.

Acidosis, Respiratory↗
PubMed2005

[Value of fetal scalp lactate sampling during labour: a comparative study with scalp pH].

OBJECTIVE: To evaluate the validity and the feasibility of fetal scalp lactate sampling during labour in the assessment of non reassuring fetal status. PATIENTS AND METHOD: A prospective observational study was conducted on 129 fetal scalp blood samplings. Scalp lactate measurements were compared to scalp pH (gold standard procedure), neonatal cord blood gas (pH and lactates) and Apgar score. Pathological values taken were for scalp lactates>5 mmol/l, scalp pH<7.20, cord arterial pH<7.10, cord arterial lactates>6,35 mmol/l, and Apgar score<7 at one and five minutes. All measurements were performed using the Rapid Lab 860 device from Bayer. RESULTS: Scalp lactate correlated significantly with scalp pH (R=-0.54, P=0.001), with umbilical artery pH (R=-0.46, P=0,01), with umbilical artery lactate (P=0.49, P=0.01), but with neither Apgar score at one minute (R=-0.21, ns) nor at 5 minutes (R=-0.11, ns). Scalp lactate at a cut-off value of 5 mmol/l had the same predictive values than scalp pH at 7.20 to predict neonatal acidosis. Sampling failure with scalp lactate was inferior to 1 vs 18% for scalp pH. DISCUSSION AND CONCLUSION: The measurement of lactate in fetal blood scalp seems correlated to the fetal scalp pH. It may be an attractive alternative to pH analysis and a useful tool for monitoring fetal asphyxia, especially with the advent of handheld devices requiring small sample volumes.

Adolescent↗
PubMed2000

Outcome with high blood lactate levels during cardiopulmonary bypass in adult cardiac operation.

BACKGROUND: High blood lactate levels during cardiopulmonary bypass (CPB) are associated with tissue hypoperfusion and may contribute to postoperative complications or death. The objective of this study was to determine an association between blood lactate levels during CPB and perioperative morbidity and mortality. METHODS: We reviewed 1,376 patients who underwent cardiac operation with CPB. Patients with abnormal preoperative blood lactate levels were excluded (n = 101). Blood lactate concentration during CPB, clinical data, and perioperative events were recorded. RESULTS: Peak blood lactate levels of 4.0 mmol/L or higher during CPB were present in 227 patients (18.0%). Postoperative mortality was higher in this group than in the patients who had peak blood lactate levels of less than 4.0 mmol/L during CPB (11.0% versus 1.4%; p < 0.001, relative risk [RR] = 9.0). Postoperative hemodynamic instability occurred in 29.5% of patients with elevated levels of lactate during CPB compared with 10.9% of patients with lower lactate levels (p < 0.001, RR = 3.4). Overall, major postoperative complications occurred in 43.2% and 21.8% of patients in each group, respectively (p < 0.001, RR = 2.7). Logistic regression analysis revealed that peak blood lactate levels of 4.0 mmol/L or higher during CPB were strongly associated with postoperative mortality (p = 0.0001) and morbidity (p = 0.013). CONCLUSIONS: Blood lactate concentration of 4.0 mmol/L or higher during CPB identifies a subgroup of patients with increased risk of postoperative morbidity and mortality.

Adult↗
PubMed1999

Preferential inhibition of lactate oxidation relative to glucose oxidation in the rat heart following diabetes.

OBJECTIVE: Alterations in myocardial metabolism occur early after the onset of diabetes suggesting that they may play a role in the development of cardiac dysfunction. Inhibition of myocardial pyruvate dehydrogenase (PDH), glucose transport and glycolysis have all been reported following diabetes. In vivo lactate is also a potential source of energy for the heart and its oxidation should not be affected by changes in glucose transport and glycolysis. Therefore, the objective of this study, was to test the hypothesis that following diabetes the inhibition of glucose oxidation would be greater than the inhibition of lactate oxidation. METHODS: Hearts from control and one-week-old diabetic rats were perfused with [1-13C]glucose (11 mmol/l) alone, [1-13C]glucose plus lactate (0.5 mmol/l) or glucose plus [3-13C]lactate (0.5 or 1.0 mmol/l) as substrates. Glucose and lactate oxidation rates were determined by combining 13C-NMR glutamate isotopomer analysis of tissue extracts with measurements of oxygen consumption. RESULTS: In diabetic hearts perfused with glucose alone, glucose oxidation was decreased compared to controls (0.31 +/- 0.08 vs. 0.71 +/- 0.11 mumoles/min/g wet weight; p < 0.05). Surprisingly, in hearts perfused with glucose plus 0.5 mmol/l lactate, there was no difference in glucose oxidation between control and diabetic groups (0.20 +/- 0.05 vs. 0.16 +/- 0.04 mumoles/min/g wet weight respectively). However, under these conditions lactate oxidation was markedly reduced in the diabetic group (0.89 +/- 0.18 vs. 0.24 +/- 0.05 mumoles/min/g wet weight; p < 0.05). At 1.0 mmol/l lactate oxidation was still significantly depressed in the diabetic group. CONCLUSION: There was a greater decrease in lactate oxidation relative to glucose oxidation in hearts from diabetic animals. These results demonstrate that diabetes leads to a specific inhibition of lactate oxidation independent of its effects on pyruvate dehydrogenase.

Analysis of Variance↗
PubMed2003

Cotransport of H+, lactate, and H2O in porcine retinal pigment epithelial cells.

The retinal pigment epithelium (RPE) of the eye transports water and lactate ions in the direction from retina to choroid. The water transport is important in maintenance of retinal adhesion and the transport of lactate ions serves to regulate the lactate levels and pH of the subretinal space. This study investigates by means of a non-invasive technique the mechanism of coupling between transport of H(+), lactate ion, and water in the monocarboxylate transporter (MCT1) located in the apical (retinal) membrane of a mammalian RPE. Primary cultures of porcine RPE cells were grown to confluence and placed in a perfusion chamber in which the solution facing the retinal membrane could be changed rapidly. Two types of experiments were performed: Changes in cell water volume were measured by self-quenching of the fluorescent dye Calcein, and changes in intracellular pH were measured ratiometrically using the fluorescent dye BCECF. In lactate-free solutions, mannitol addition to the retinal bath caused intracellular acidification and cell shrinkage, given by a single osmotic water permeability of 1.2+/-0.1 x 10(-4)cmsec(-1) (osmoll(-1))(-1). In solutions containing 50 mmoll(-1) lactate, however, the mannitol-induced cell shrinkage was faster and the cells alkalinized. These effects were not linear functions of the magnitude of the imposed osmotic gradients: Both volume effects and changes in intracellular pH showed apparent saturation with increasing gradients. Abrupt isosmotic replacement of Cl(-) with lactate in the concentration range from 3 to 50 mmoll(-1) caused an immediate cell swelling as well as an immediate intracellular acidification; both effects showed apparent saturation with increasing lactate concentration. The K(m) values were: 11+/-2 mmoll(-1) for the water fluxes and 13+/-4 mmoll(-1) for the H(+) and lactate fluxes. The data suggest that H(2)O is cotransported along with H(+) and lactate ions in MCT1 localized to the retinal membrane. The study emphasizes the importance of this cotransporter in the maintenance of water homeostasis and pH in the subretinal space of a mammalian tissue and supports our previous study performed by an invasive technique in an amphibian tissue.

Animals↗