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      Functional Recovery of Chronic Ischemic Myocardium after Surgical Revascularization Correlates with Magnitude of Oxidative Metabolism

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          Background: The purpose of this study was to validate myocardial microdialysis measurements in patients after myocardial infarction with or without associated postoperative functional recovery in order to develop a highly sensitive tool for real-time in vivo detection of microcellular disorder during cardiac operations. Methods: In 20 patients undergoing coronary artery bypass grafting, microdialysis catheters were implanted into scar or hibernating segments detected by means of magnetic resonance imaging, and into a vital area of the right ventricle (control). Myocardial glucose, lactate and pyruvate were analyzed perioperatively. Myocardial ethanol washout was measured as a sign of recovered local blood flow. Results: After surgical revascularization, improvement of wall motion was found in all hibernating segments compared to the scar segments paralleling an increased glucose delivery to the tissue and increased myocardial tissue flow. The myocardial glucose/lactate ratio and pyruvate also showed significantly higher values. Microdialytic measurements of the viable segments were comparable with those of the right ventricle. Conclusions: Our results indicate that microdialysis measurements parallel magnetic resonance imaging findings in patients with revascularization of chronic ischemic myocardium with dyskinetic segments. The metabolism of those segments is characterized by a significantly increased tissue flow, an increased utilization of glucose and a better oxidative nutrition.

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          Most cited references 22

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          Lactate and shock state: the metabolic view.

           Bruno Levy (2006)
          The conventional view in severe sepsis or septic shock is that most of the lactate that accumulates in the circulation is due to cellular hypoxia and the onset of anaerobic glycolysis. A number of papers have suggested that lactate formation during sepsis is not due to hypoxia. I discuss this hypothesis and outline the recent advances in the understanding of lactate metabolism in shock. Numerous experimental data have demonstrated that stimulation of aerobic glycolysis - that is, glycolysis not attributable to oxygen deficiency - and glycogenolysis occurs not only in resting, well-oxygenated skeletal muscles but also during experimental haemorrhagic shock and experimental sepsis, and is closely linked to stimulation of sarcolemmal Na+/K+ -ATPase under epinephrine stimulation. A human study of hyperkinetic septic shock demonstrated that skeletal muscle is a leading source of lactate production by exaggerated aerobic glycolysis through Na+/K+ -ATPase stimulation. There is increasing evidence that sepsis is accompanied by a hypermetabolic state, with enhanced glycolysis and hyperlactataemia. This should not be rigorously interpreted as an indication of hypoxia. It now appears, at least in the hyperkinetic state, that increased lactate production and concentration as a result of hypoxia are often the exception rather than the rule.
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            Microdialysis--principles and applications for studies in animals and man.

             U Ungerstedt (1991)
            Microdialysis is a technique for sampling the chemistry of the individual tissues and organs of the body, and is applicable to both animal and human studies. The basic principle is to mimic the function of a capillary blood vessel by perfusing a thin dialysis tube implanted into the tissue with a physiological liquid. The perfusate is analysed chemically and reflects the composition of the extracellular fluid with time due to the diffusion of substances back and forth over the membrane. Microdialysis is thus a technique whereby substances may be both recovered from and supplied to a tissue. The most important features of microdialysis are as follows: it samples the extracellular fluid, which is the origin of all blood chemistry; it samples continuously for hours or days without withdrawing blood; and it purifies the sample and simplifies chemical analysis by excluding large molecules from the perfusate. However, the latter feature renders the technique unsuitable for sampling large molecules such as proteins. The technique has been extensively used in the neurosciences to monitor neurotransmitter release, and is now finding application in monitoring of the chemistry of peripheral tissues in both animal and human studies.
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              Clinical cerebral microdialysis: a methodological study.

              Clinical microdialysis enables monitoring of the cerebral extracellular chemistry of neurosurgical patients. Introduction of the technique into different hospitals' neurosurgical units has resulted in variations in the method of application. There are several variables to be considered, including length of the catheter membrane, type of perfusion fluid, flow rate of perfusion fluid, and on-line compared with delayed analysis of samples. The objects of this study were as follows: 1) to determine the effects of varying catheter characteristics on substance concentration; 2) to determine the relative recovery and true extracellular concentration by varying the flow rate and extrapolating to zero flow; and 3) to compare substance concentration obtained using a bedside enzyme analyzer with that of off-line high-performance liquid chromatography (HPLC). A specially designed bolt was used to conduct two adjacent microdialysis catheters into the frontal cortex of patients with head injury or poor-grade subarachnoid hemorrhage who were receiving ventilation. One reference catheter (10-mm membrane, perfused with Ringer's solution at 0.3 microl/minute) was constant for all studies. The other catheter was varied in terms of membrane length (10 mm or 30 mm), perfusion fluid (Ringer's solution or normal saline), and flow rate (0.1-1.5 microl/minute). The effect of freezing the samples on substance concentration was established by on-line analysis and then repeated analysis after storage at -70 degrees C for 3 months. Samples assayed with the bedside enzyme analyzer were reassessed using HPLC for the determination of glutamate concentrations. Two adjacent microdialysis catheters that were identical in membrane length, perfusion fluid, and flow rate showed equivalent results. Variations in perfusion fluid and freezing and thawing of samples did not result in differences in substance concentration. Catheter length had a significant impact on substance recovery. Variations in flow rate enabled the relative recovery to be calculated using a modification of the extrapolation-to-zero-flow method. The recovery was approximately 70% at 0.3 microl/minute and 30% at 1 microl/minute (10-mm membrane) for all analytes. Glutamate results obtained with the enzyme analyzer showed good correlation with those from HPLC.

                Author and article information

                S. Karger AG
                June 2008
                04 December 2007
                : 110
                : 3
                : 174-181
                Departments of aCardiac Surgery and bAnesthesiology, Schüchtermann-Klinik, Bad Rothenfelde, cDepartment of Anesthesiology, Herz Jesu Krankenhaus, Münster, dDepartment of Anesthesiology, University of Lübeck, Lübeck, and eInstitut für klinische Herz-Kreislaufforschung der Universität Witten-Herdecke, Dortmund, Germany; fDepartment of Cardiac Surgery, University of Insubria-Varese, Varese, Italy
                111927 Cardiology 2008;110:174–181
                © 2007 S. Karger AG, Basel

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                Page count
                Figures: 4, Tables: 1, References: 35, Pages: 8
                Original Research


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