Infusionstherapie und Transfusionsmedizin
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Bleeding is causally related to about 50% of postoperative deaths following liver resection. Main factors contributing to increased perioperative bleeding in liver surgery include surgical trauma, reduced activity of clotting factors and inhibitors due to impaired hepatic synthesis, low platelet count and poor platelet function as well as impaired clearance of activated clotting factors by the reticuloendothelial system of the liver (Kupffer cells). Hemostasis may be further impaired by transfusion of blood components, since citrate added for conservation is not adequately metabolized by the failing liver. ⋯ Thrombelastography is the leading method for diagnosis of hyperfibrinolysis, which can also be assessed by determination of D-dimer, fibrinogen and fibrin degradation products. Evaluation of primary hemostasis is frequently restricted to platelet count, which is only a rough parameter. In contrast, measurement of in vitro bleeding time and volume enables repeated quantification of platelet function in patients with impaired hemostasis.
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Infusionsther Transfusionsmed · Aug 1993
Comparative StudyPerioperative respiratory monitoring of oxygen transport.
Oximetry nowadays is understood as the in vitro measurement of O2 saturation (sO2, %) and hemoglobin (Hb) derivatives (%) using 4-7 wavelengths (CO- and Hem-oximeters). Pulse oximeters, using only 2 wavelengths, are designed for the continuous noninvasive measurement of the arterial partial O2 saturation (psO2, %) in vivo. Light-emitting diodes allow light to pass through the peripheral site of measurement with red and infrared light to enable a distinction between oxygenated and deoxygenated hemoglobin during a recorded pulse wave. ⋯ In the case of elevated methemoglobin (MetHb) concentrations, the situation is completely different. With increasing cMetHb, the psO2 is still the value required, but success depends on the concentration of MetHb: under normoxia psO2 is increasingly underestimated, whereas under hypoxia increasing overestimation must be anticipated. Provided there is a constant Hb concentration, knowledge of the initial sO2, and absence of the derivatives COHb and MetHb as well as of severe perfusion disorders, pulse oximetry is suitable for perioperative respiratory monitoring of oxygen transport.
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The pressure-volume diagram of the left ventricle is fundamental to understanding the mechanics of contraction and its modification by disease, drugs and anaesthetics. For monitoring patients perioperatively, we advocate variables derived from the pressure-volume diagram: cardiac output to monitor circulatory failure, pulmonary capillary wedge pressure to monitor the acute state of left ventricular filling and echocardiography to determine the chronicity and severity of chronic heart failure. Use of the pressure-volume diagram shows that whenever arterial pressure is raised by the use of vasoconstrictor agents, the flow of blood to the tissues is impaired. ⋯ In view of the prime need of the body tissues for blood flow, together with oxygen and substrates, it is advocated that vasoconstricting agents should not be used to maintain arterial pressure in the perioperative period. Plasma expansion and control of posture are preferred methods for maintaining the circulation. If circulatory failure continues in the presence of a high filling pressure of the left ventricle (wedge pressure), drugs combining positively inotropic and vasodilator properties are advocated.
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Monitoring of the anesthetized patient, the anesthesia machine, and the patient-machine interface is an essential component of anesthetic practice in order to prevent anesthetic-related injuries resulting from equipment failure or human error. While the optimal monitor to detect anesthetic problems (hypoxia, esophageal intubation, hemodynamic compromise, for example) is unclear at present, American standards require continuous presence of qualified personnel who evaluate patient oxygenation, ventilation, circulation, and temperature. A common monitoring array includes electrocardiogram, autosphygmomanometer, pulse plethysmography/oximetry, stethoscope, anesthetic gas analyzer, thermistor, and nerve stimulator. The role of emerging technologies, including transesophageal echocardiography, automated electrocardiographic analysis of ST segments, transcranial Doppler, and transcranial near infrared spectroscopy are discussed.
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Infusionsther Transfusionsmed · Jun 1993
[Transfusion-induced virus infections: how great is the risk?].
The risk of infection by blood transfusions contaminated with the human immunodeficiency virus (HIV) and/or the hepatitis C virus (HCV) was dramatically reduced after the introduction of blood donor screening using specific and sensitive 2nd- or 3rd-generation enzyme immunoassays for virus antibody detection. In addition, donors selection provides the greatest safety. The strategy for safe blood supply includes medical examination and self-exclusion of donors. ⋯ The overall risk of HIV infection ranges from 1 in 500,000 to 1 in 3 million and that of a transfusion-associated HCV infection from 1 in 20,000 to 1 in 40,000 per transfused blood unit. From the observed virus load among German blood donors, the transfusion-associated mortality was calculated to be 1 in 260,000 per transfused blood unit. Implications are discussed resulting from this low risk of HIV and/or HCV infection by blood transfusions.