Der Anaesthesist
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The optimal methods of prophylaxis and therapy of postoperative respiratory complications in surgical patients are still open to discussion. In spite of numerous recent clinical investigations, there is still no specific and universally acceptable therapeutic concept. In our department, we identify patients at risk of pulmonary complications by adequate screening, i.e. medical history, physical examination, chest X-ray, and spirometry. ⋯ This process continues to some extent until, normally, a deep breath recruits the alveoli. Sighs to the limit of total lung capacity or oscillations of the expiratory baseline ought to be responsible for this effect in healthy humans; the same purpose is intended in incentive spirometry. For this therapy, it is mandatory that the central airways are not occluded by mucus and that the patient is able to breath volumes exceeding his normal tidal volume.(ABSTRACT TRUNCATED AT 250 WORDS)
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Various animals models and several different methods are used in cardiopulmonary resuscitation (CPR) research. The animals used most frequently are dogs and pigs, but in each species thorax configurations, which might be an important factor in the mechanism of blood flow during CPR, are at great variance. The influence of anesthetics on cardiopulmonary and cerebral functions during and following resuscitation are largely unknown, and accordingly there is great variance in the techniques employed by individual researchers. ⋯ Thorax compressions are characterized by frequency, direction (sagittal, transversal), technique (mechanical, manual), relationship of time between compression and relaxation (50:50, 40:60), and depth of compression (power used, esophageal pressure, arterial blood pressure). Effects of CPR techniques are demonstrated during CPR by cardiovascular parameters. In addition to recording of blood pressure and blood flow, examination of regional perfusion rates using radioactive microsphere techniques is common. 24-h surveillance and extensive neurological tests are carried out during recovery following CPR.
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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)
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In 60%-90% of cases head injury is a part of multisystem trauma and of very decisive importance for the post-traumatic prognosis. Hypoxia, hypercarbia, and hypotension increase the primary lesion and cause secondary brain damage. Therefore, emergency measures must be directed to the essentials of sustaining vital functions, i.e. intubation/ventilation/oxygenation and stabilization of the circulatory system. ⋯ Anesthesia in patients with severe head injury must involve only those techniques that do not further increase an already elevated intracranial pressure. As inhalational anesthetics, including nitrous oxide, elevate the intracranial pressure to varying extents due to cerebral vasodilation with a concomitant rise in intracranial blood volume, these substances have to be avoided whenever raised intracranial pressure cannot be excluded. Narcotics, benzodiazepines, small dosages of barbiturates, and long-lasting muscle relaxants can be regarded as useful.