Lactate, blood, monitoring

Lactate is an important marker compound in many biomedical, food and beverage applications. Blood lactate is monitored in exercise control and sports medicine, and D-lactate is an indicator of bacterial activity in wine fermentation [59,60,63]. Lactate produced from anaerobic respiration of cattle muscle subsequent to slaughter has been investigated as an indicator of meat freshness [62],... 

Ex vivo blood monitoring experiments with human volunteers were performed by placing a device comprising two glucose and two lactate sensors into the sampling line of a double lumen catheter. Venous blood was continuously withdrawn and in line heparinized with a dilution of less then 5 %. 

MANAGING LACTIC ACIDOSIS. When taking metformin, the patient is at risk for lactic acidosis. The nurse monitors die patient for symptoms of lactic acidosis, which include unexplained hyperventilation, myalgia, malaise, gastrointestinal symptoms, or unusual somnolence If the patient experiences these symptoms, the nurse should contact the primary care provider at once. Elevated blood lactate levels of greater than 5 mmol/L are associated with lactic acidosis and should be reported immediately. Once a patient s diabetes is stabilized on metformin therapy, the adverse GI reactions that often occur at the beginning of such therapy are unlikely to be related to the drug therapy. A later occurrence of GI symptoms is more likely to be related to lactic acidosis or other serious disease. 

Monitor the following serial laboratories for comparison to baseline values every 6 hours in the first 24 hours and daily thereafter until normalized sodium, serum creatinine, blood urea nitrogen, serum lactate, glucose, bilirubin, hemoglobin, hematocrit, platelets, prothrombin time, partial thromboplastin time, arterial blood gases, and pH. 

Similarly, monitoring the amount of mtDNA, usually via the mtDNA nuDNA ratio [72], provides a more sensitive index of diminishing mitochondrial biomass and much of this work focuses on peripheral blood samples because they are readily available. In fibroblasts treated with ddC for 4 weeks, mtDNA dropped by 80% within the first week and the lactate/pymvate ratio lagged behind, but was pathologically elevated after 3 weeks. A 4-week wash-out treatment then showed that mtDNA returned to 90% of the initial value within 3 weeks and lactate/pyruvate ratio gradually normalized over 4 weeks. It bears reiteration in this context that... 

Routine monitoring of lactate is not recommended, since lactate concentrations do not correlate with symptoms and patients may have asymptomatic lactatemia. Furthermore, technical difficulties in blood collection and processing, and the lack of a standardized definition of lactic acidosis for patients taking NRTIs, prevent any routine monitoring recommendations in the absence of symptoms. In addition, it is possible that NRTIs also cause other forms of mitochondrial dysfunction. 

An example of an enzyme which has different isoenzyme forms is lactate dehydrogenase (LDH) which catalyzes the reversible conversion of pyruvate into lactate in the presence of the coenzyme NADH (see above). LDH is a tetramer of two different types of subunits, called H and M, which have small differences in amino acid sequence. The two subunits can combine randomly with each other, forming five isoenzymes that have the compositions H4, H3M, H2M2, HM3 and M4. The five isoenzymes can be resolved electrophoretically (see Topic B8). M subunits predominate in skeletal muscle and liver, whereas H subunits predominate in the heart. H4 and H3M isoenzymes are found predominantly in the heart and red blood cells H2M2 is found predominantly in the brain and kidney while HM3 and M4 are found predominantly in the liver and skeletal muscle. Thus, the isoenzyme pattern is characteristic of a particular tissue, a factor which is of immense diagnostic importance in medicine. Myocardial infarction, infectious hepatitis and muscle diseases involve cell death of the affected tissue, with release of the cell contents into the blood. As LDH is a soluble, cytosolic protein it is readily released in these conditions. Under normal circumstances there is little LDH in the blood. Therefore the pattern of LDH isoenzymes in the blood is indicative of the tissue that released the isoenzymes and so can be used to diagnose a condition, such as a myocardial infarction, and to monitor the progress of treatment. 

Metabolic blood parameters are assayed in anesthetized male rats using a modified method of glucose clamp studies in rodents (Terrettaz and Jeanrenaud 1983). Four to 6 rats per group (vehicle control and one dose of the candidate compound) are used. Rats are anesthetized with an intraperitoneal injection of pentobarbital sodium (60 mg/kg), tracheotomized, and one jugular vein per rat is cannulated for intravenous infusion the other vein is prepared for collection of blood samples. Anesthesia is maintained for up to 7 hours by subcutaneous infusion of pentobarbital sodium (adjusted to the anesthetic depth of the individual animal about 24 mg/kg/h). Body temperature is monitored with a rectal probe thermometer, and temperature is maintained at 37 °C by means of a heated surgical table. Blood samples for glucose analysis (10 il) are obtained from the tip of the tail every 15 minutes, and for lactate analysis (20 p.1) every... 

Laboratory tests indicated for the ongoing monitoring of shock include electrolytes and renal function tests (blood urea nitrogen, serum creatinine) complete blood count to assess possible infection, 02-carrying capacity of the blood, and ongoing bleeding PT and aPTT to assess clotting ability and lactate concentration and base deficit to detect inadequate tissue perfusion. 

Parkin MC, Hopwood SE, Jones DA, Hashemi P, Landolt H, Fabricius M, Lauritzen M, Boutelle MG, Strong AJ. Dynamic changes in brain glucose and lactate in pericontusional areas of the human cerebral cortex, monitored with rapid sampling on-line microdialysis relationship with depolarisation-like events. J. Cereb. Blood Flow. 2005 25 402-413. 

A different lactate biosensor was proposed by Pfeiffer et al. [152], who used an enzyme sandwich membrane that was commercially available for whole blood lactate analysers. The membrane was inserted into a flow cell connected to a microdialysis probe. This membrane showed a significant day-to-day variation in sensitivity ( 50%), but no trend in sensitivity decrease. The problem of rejecting interference has not been completely solved by this system. However, the continuous monitoring of subcutaneous lactate was feasible at least in small rodents, and results were consistent with liquid chromatographic measurements performed on dialysate samples collected during the in vivo experiment. 

The most important and most studied applications of enzyme biosensors are to detect and monitor blood glucose, followed by lactate, because of the medical applications of such sensors. Thus, by initially detailing the development of glucose biosensors we can better understand and trace the general development of enzyme biosensors containing polymeric electron transfer systems. 

Grimvall E, Rylander L, Nilsson-Ehle P, et al. 1997. Monitoring of polychlorinated biphenyls in human blood plasma Methodological developments and influence of age, lactation, and fish consumption. Arch Environ Contam Toxicol 32 329-336. 

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