Der Anaesthesist
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Comparative Study
[Organ blood supply and oxygenation during limited isovolemic hemodilution with 6% HES 200/0.62 and 6% Dextran 70].
Oxygen delivery (systemic oxygen transport) is directly dependent upon cardiac output and oxygen content of the blood. The rheology of blood, however, represents a co-determinant of oxygen delivery. It has recently been argued that the increase in plasma viscosity occurring under hemodilution with dextran could be detrimental to blood flow and, hence, tissue oxygenation. ⋯ Systemic oxygen transport was not affected by plasma viscosity changes, but is primarily determined by systemic hct. Local surface tissue oxygenation on skeletal muscle and liver was not impaired, but rather improved during hemodilution despite raised plasma viscosity. Of the rheological factors influencing oxygen delivery, hct thus plays the predominant role while plasma viscosity is of minor importance.
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Comparative Study
[Inspiratory and expiratory resistance of 8 semi-closed circle systems].
The resistance of a circle system is an important factor that determines the respiratory effort of the patient. The inspiratory and expiratory resistances were measured in eight semi-closed circle systems used in Europe: Dräger Cicero, Dräger 8 ISO, Dräger AV1, Ohmeda Modulus II Plus, Gambro Engström Elsa, Siemens Servo Ventilator 900 D with circle system 985, Siemens Ventilator 710, and Megamed 700A with circle system 219. The measurements were all performed in the position "spontaneous breathing" according to a new proposal of the CEN (Comité Européen de Normalisation). ⋯ The expiratory resistance was also determined by using intermittent flows. The results differed, as the expiratory gas flow can be influenced by the falling or rising ventilator bellows. The authors conclude that considerable differences exist between various breathing systems and that not all systems can be recommended for use in patients with limited breathing force, such as small children.
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As a result of human activities the ozone layer in the stratosphere, which is necessary for life on earth, has changed. The main causes of ozone destruction are chlorofluorcarbons (CFCs) 11 and 12. Recently, caring anesthetists have wondered if and to what degree N2O and popular potent inhalation anesthetics may also contribute to ozone loss. ⋯ On the other hand, the worldwide production of inhalation anesthetics is said to be only 2,000 tons. In view of the experimental calculations and the low worldwide production, the small greenhouse effect, the shorter lifespan in the troposphere, and the low potential for ozone destruction, the negative effects of medically used N2O and inhalation anesthetics on the ozone layer seem negligible. All in all, the inhalation anesthetics are considered to be responsible for only 0.0005% of the ozone destruction at present.