Der Anaesthesist
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The perioperative risk for patients with pacemakers or implanted cardioverter/defibrillators (ICD) is mainly dependent on the underlying disease. However, severe to life-threatening complications of the implanted system can occur due to electromagnetic interference in the environment of the operation. These complications can be prevented or adequately treated by taking special precautions and measures. Even though the currently available data on the optimal perioperative management to pacemakers and ICDs is still unsatisfactory, the increasing clinical relevance of this topic was the reason for the formulation of recommendations by an interdisciplinary working group in Austria.
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Increasing specialization and growing mechanization in medicine have strongly supported the transfer of originally medical responsibilities to non-medical personnel. The enormous pressure of costs as a result of limited financial resources in the health system make the delegation of previously medical functions to cheaper non-medical ancillary staff expedient and the sometimes obvious lack of physicians also gains importance by the delegation of many activities away from medical staff. ⋯ The inclination towards risk of medical activities, the need of protection of the patient and the intellectual prerequisites required for carrying out the necessary measures define the limitations for the delegation of medical responsibilities to non-medical ancillary staff. These criteria demarcate by expert assessment the exclusively medical field of activity in a sufficiently exact and convincing manner.
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The force of cardiac contraction is strongly influenced by myocardial fibre length at the beginning of systole. Because the length of cardiac sarcomers and muscle fibres primarily depends on the end-diastolic ventricular volume, filling pressures a priori can only act as indirect parameters of cardiac preload. Central venous pressure (CVP) gives information on right ventricular end-diastolic pressure, which parallels changes in left ventricular end-diastolic pressure as long as ventricular function is not impaired. ⋯ Variables which more directly represent end-diastolic ventricular volume (e.g. intrathoracic blood volume or end-diastolic ventricular area) offer a higher validity as estimates of cardiac preload. Furthermore, dynamic parameters of ventricular preload, such as pulse pressure variation or stroke volume variation, seem to be more predictive of volume responsiveness in ventilated patients than CVP. These limitations, however, do not impair the importance of CVP as the downstream pressure of the systemic venous system.
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Values of intramural or even transmural central venous pressure (CVP) as well as values of pulmonary artery occluded pressure do not correlate with the values of measured circulating blood volume or with responsiveness to fluid challenge. The veins contain approximately 70% of the total blood volume and are 30 times more compliant than arteries, therefore, changes in blood volume within the veins are associated with relatively small changes in venous pressure. The main reason for a lack of correlation between CVP values and blood volume is that the body does everything possible to maintain homeostasis and adequate transmural CVP is a must for cardiovascular function. ⋯ Stressed volume determines MCFP and directly affects venous return and cardiac output whereas unstressed volume is a reserve of blood that can be mobilized into circulation when needed. Both stressed and unstressed volume cannot be adequately measured. Therefore, considering the complexity of the physiologic feedback and clinical picture, robust reflexes and homeostatic mechanisms, CVP is insufficient as a surrogate parameter for assessing the volume status.
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Biography Historical Article
[The 100th anniversary of the birthday of Virginia Apgar. In honor of the developer of the Apgar score].
The 7th of June 2009 marks the 100th anniversary of the birthday of the American anaesthesiologist Virginia Apgar. The Apgar score for evaluation of the newborn created by her in 1952 and later named after her is one of the most popular and most often used medical scoring systems.