Acta anaesthesiologica Scandinavica. Supplementum
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Acta Anaesthesiol Scand Suppl · Jan 1995
ReviewPermissive hypercapnia in ARDS and its effect on tissue oxygenation.
Many experimental studies have shown that mechanical ventilation with high tidal volumes (Vt) or with a low end-expiratory volume allowing repeated end-expiratory collapse, can result in acute parenchymal lung injury and probably an inflammatory response. Low volume ventilation with permissive hypercapnia has been used in an attempt to avoid such injury in ARDS. Such management can affect oxygenation in many complex ways. ⋯ Limited clinical studies suggest that tissue oxygenation is usually unchanged or improved during permissive hypercapnia with increased CO, reduced arterio-venous O2 content difference and reduced blood lactate concentration. However, acute hypercapnia per se can reduce lactate production. Further studies are required of this complex issue.
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Acta Anaesthesiol Scand Suppl · Jan 1995
Notes on the apparent discordance of pulse oximetry and multi-wavelength haemoglobin photometry.
Multi-wavelength photometers, blood gas analysers and pulse oximeters are widely used to measure various oxygen-related quantities. The definitions of these quantities are not always correct. This paper gives insight in the various definitions for oxygen quantities. ⋯ The influence of fetal haemoglobin is insignificant in the neonatal use of pulse oximetry, in the range of 75% to 100% arterial oxygen saturation. However, a pulse oximeter underestimates the arterial oxygen saturation at the 25% level with 5%, if the pulse oximeter has been calibrated in human adults. Such a low level of arterial oxygen saturation can be present in the fetus during labor.
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Acta Anaesthesiol Scand Suppl · Jan 1995
Comparative Study Clinical TrialAdministration of 51W89 by infusion--a comparison with atracurium--preliminary communication.
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Acta Anaesthesiol Scand Suppl · Jan 1995
Oxygen and acid-base parameters of arterial and mixed venous blood, relevant versus redundant.
A complete pH and blood gas analysis of arterial and mixed venous blood may comprise more than forty different quantities. We have selected sixteen, including patient temperature. The arterial oxygen tension group includes the oxygen tension, fraction of oxygen in inspired air, and fraction of mixed venous blood in the arterial (total physiological veno-arterial shunting). ⋯ The mixed venous group includes mixed venous oxygen tension, and, when measured, cardiac output, and oxygen consumption rate. The acid-base status includes blood pH, arterial carbon dioxide tension, and extracellular base excess. Other quantities such as haemoglobin oxygen saturation, respiratory index, total oxygen concentration (oxygen content), oxygen extraction fraction, oxygen delivery, and several others, provide no essential additional clinical information and are therefore redundant.
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Acta Anaesthesiol Scand Suppl · Jan 1995
ReviewQuantifying pulmonary oxygen transfer deficits in critically ill patients.
The clinical picture describing oxygen transfer deficits in literature is complicated by inconsistent terminology, and a weak perception of the influence total errors of measured and estimated values have on clinical decision-making. Clinical and analytical terminology: Terms like hypoxia, hypoxaemia and tissue hypoxia in clinical literature are often used synonymously. In present terminology, arterial hypoxia (pO2(a)) is considered to be based on measurements of oxygen tension in arterial blood. ⋯ A calculated shunt of 20-29% may be life threatening in a patient with limited cardiovascular function. A calculated shunt greater than 30% usually requires significant cardiopulmonary support. The necessity of sampling mixed-venous blood seems to be the most limiting factor for a widespread clinical use of shunt calculations.