Der Anaesthesist
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Intraocular surgery is performed under local or general anesthesia. The indications for these procedures are often dependent on local circumstances. On the one hand, the optimal conditions for operations under general anesthesia, on the other, the negligible stress of local anesthesia, especially for the elderly, are emphasized. To clarify this question, perioperative anxiety behavior and postoperative pain were investigated in geriatric patients undergoing ophthalmic surgery. ⋯ The scores of state and trait anxiety behavior are comparable to a normal geriatric population, even if normal data cannot always be applied to clinical situations.(ABSTRACT TRUNCATED AT 250 WORDS)
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Understanding the mismatching of ventilation and perfusion (VA/Q) is of special interest in the intensive care setting because - given a stable cardiac output and a given inspiratory oxygen fraction - it allows one to explain certain essential respiratory problems in critically ill patients, namely hypoxemia and hypercarbia. Several different methods are available today for the evaluation VA/Q mismatching. Analysis of the PCO2 and PO2 in arterial and mixed venous blood and mixed expired gas yields information about the quality and the degree of the mismatching present. ⋯ The multiple inert gas elimination technique permits virtually continuous ventilation-perfusion distributions to be described over the whole range of VA/Q ratios and has contributed to explaining the pathophysiological mechanisms in various pulmonary diseases. This method, however, is technically very complex and hence will remain a sophisticated investigational tool. Scintigraphic approaches allow the description of regional topographic VA/Q distributions, but their application is still difficult in the intensive care setting.
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The main task of the cardiorespiratory system is to deliver enough oxygen (O2) to meet the metabolic requirements of the body. Of all metabolic substrates, O2 has the highest percentage of extraction at 25%, and O2-reserves are therefore exhausted within a few minutes. Arterial O2-content and cardiac output (CO) are the determinants of O2-delivery (DO2). ⋯ Routinely measured hemodynamic parameters such as heart rate, systemic arterial pressure, etc. only poorly reflect O2-transport to the tissues. O2-consumption (VO2), the best mirror of the actual metabolic activities of the tissues, can be measured either noninvasively by the difference between inspiratory and expiratory O2-concentrations in connection with minute ventilation or invasively using arterial-venous O2-content difference and CO, which requires pulmonary artery catheterization. VO2 determination by respiratory gas analysis is very difficult at a high or changing FiO2.(ABSTRACT TRUNCATED AT 250 WORDS)