The article presents the findings of microscopic and electrochemical studies of size-dependent gold particles electrooxidation. Gold particles were immobilized on the surface of carbon-containing ...screen-printed electrodes. The experiment demonstrated that the transition from macroparticles to nanoparticles caused a shift of the maximum current potential of gold oxidation into the area with more negative potentials. A decrease in particle size resulted in an increase in the electrochemical activity of metal. A positive correlation between experimental and calculated curves confirms a mathematical model (
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) and correctness of the calculations. Measured parameters of voltammograms, in particular, maximum current potential, can be used to describe the electrochemical activity and energy properties of nanoparticles.
Objective To investigate the effects of ventilatory mode, injectate temperature, and clinical situation on the precision of cardiac output measurements. Design Randomized, prospective observational ...study. Setting Single university hospital. Participants Forty patients undergoing planned cardiac surgery, receiving a pulmonary artery catheter according to institutional routine. Interventions Cardiac output was measured at 4 predefined time points during the perioperative patient course, twice during controlled and twice during spontaneous ventilation, using 2 blocks of 8 measurement replications with cold and tepid injectate in random order. Measurements and Main Results The data were analyzed using a hierarchical linear mixed model. Clinical precision was determined as half the width of the 95% confidence interval for the underlying true value. The single-measurement precision measured in 2 different clinical situations for each temperature/ventilation combination was 8% to 10%, 11% to 13%, 13% to 15%, and 23% to 24% in controlled ventilation with cold injectate, controlled ventilation with tepid injectate, spontaneous breathing with cold injectate, and spontaneous breathing with tepid injectate, respectively. Tables are provided for the number of replications needed to achieve a certain precision and for how to identify significant changes in cardiac output. Conclusions Clinical precision of cardiac output measurements is reduced significantly during spontaneous relative to controlled ventilation. The differences in precision between repeated measurement series within the temperature/ventilation combinations indicate influence of other situation-specific factors not related to ventilatory mode. Compared with tepid injectate in patients breathing spontaneously, the precision is 3-fold better with cold injectate and controlled ventilation.
Objective To assess the effect of coronary artery bypass grafting with cardiopulmonary bypass on muscle perfusion, oxygen extraction, and lactate release during postoperative rest and exercise. ...Design Prospective observational study. Setting University hospital. Participants Patients undergoing planned coronary artery bypass grafting. Intervention Knee-extensor exercise before and after coronary artery bypass grafting. Measurements and Main Results Femoral artery blood flow was measured with ultrasound. Femoral vein blood and arterial blood were sampled at rest and during light exercise and were analyzed for hemoglobin, lactate, oxygen saturation, and oxygen partial pressure. Fourteen patients were tested before and after surgery. The arterial lactate concentrations were increased after surgery, both at rest and during light exercise. Resting arterial lactate increased from 0.65 (0.5-0.8) to 1.0 (0.9-1.3) mmol/L (p = 0.01) (median and interquartile range). Furthermore, lactate was released from the leg even during postoperative rest, and the release of lactate was increased during postoperative exercise. There were no significant differences between the preoperative and postoperative femoral artery blood flow. Femoral vein oxygen partial pressure was reduced significantly after surgery, indicating reduced muscle cell oxygen partial pressure. Conclusions The patients had elevated anaerobic metabolism in skeletal muscle after surgery to compensate for anemia. Lactate was released from the leg into the general circulation during postoperative rest and exercise. The postoperatively reduced hemoglobin concentration of 11.4 mg/dL (10.6-12.3) resulted in increased anaerobic metabolism and release of lactate from skeletal muscle. The authors concluded that coronary artery bypass grafting patients are susceptible to anaerobic metabolism even with maintained peripheral blood flow.
The study's objective was to evaluate a novel two-dimensional ultrasound imaging modality termed "blood flow imaging" (BFI) for intraoperative assessment of blood flow patterns in coronary ...anastomoses. The BFI modality extends color Doppler imaging (CDI) with information on flow direction and velocity that is not limited by angle dependency or aliasing artifacts.
Intraoperative ultrasound recordings of patent left internal mammary artery-left anterior descending anastomoses were acquired from an experimental porcine model (N = 9). Three independent observers randomly evaluated CDI and BFI cineloops with regard to different assessments of flow direction and velocity. Further, a selection of technical problems that might occur in clinical practice was induced in three pigs to investigate the resulting flow patterns.
The BFI modality was found to provide an improved visual assessment of blood flow patterns in the left internal mammary artery-left anterior descending anastomosis compared with CDI.
The modality may therefore increase the certainty and efficiency of flow evaluation for intraoperative quality control in coronary surgery.
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