La Revue du praticien
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La Revue du praticien · Nov 1990
[Tissue oxygenation during recovery from anesthesia. Value and measurement].
The measurement of tissue oxygen concentrations in the intensive care unit is important for the management of patients, especially those in shock. In daily practice, right heart catheterization with continuous monitoring of the oxygen saturation of mixed venous blood provided means of evaluating the principal parameters of oxygenation (transport, consumption and extraction), and of analyzing therapeutic interventions. The finding of an oxygen debt implies an appropriate therapeutic response designed to balance oxygen supplies with peripheral oxygen demand.
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Arterial concentration of CO2 (PaCO2) is dependent of pulmonary excretion. When this excretion is lower than cellular production respiratory acid-basis occurs: rise in PaCO2 which lowers pH and produces secondary increases in bicarbonate (HCO3-) plasma concentration. Respiratory alkalosis, generated by a CO2 pulmonary excretion greater than metabolic production is characterized by a fall in PaCO2 which raises pH and induces secondary reduction of plasmatic HCO3- concentration. Attention to the possibility of serious hypoxemia, cause or consequence, should always be regarded and treated in respiratory acid-base disorders.
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The various techniques of cochlear implantation are described. Implants may be divided into mono- and multi-electrode and into intra- and extra-cochlear. Cochlear implants are indicated only in patients with total or deep bilateral deafness with residual fibres still functioning in the acoustic nerves. Intra-cochlear multi-electrode implants are the most sophisticated ones and usually provide better performances than those observed with mono-electrode implants.
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Recent advances in epidemiology, virology and molecular biology have made it possible: 1) to isolate and characterize the hepatitis C and D viruses (and soon the virus of hepatitis E); 2) to develop vaccines against hepatitis A and recombinant vaccines against hepatitis B; and 3) to obtain a better understanding of the modes of transmission of the viruses and, consequently, to devise and offer an efficient prophylaxis.
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Relations between endometriosis and infertility are complex and difficult to establish. Numerous theories have been suggested, but none of them has proved conclusive. As always in case of endometriosis, medical and surgical treatments are open to discussion. The right time for medically assisted procreation is obvious in patients with tubal obstruction but in the others it varies according to age, duration of infertility and previous treatments.