Acta anaesthesiologica Scandinavica. Supplementum
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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.
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Many anaesthetic drugs and adjuvants can cause the release of histamine by chemical (anaphylactoid) or immunologic (anaphylactic) mechanisms. While both types of reactions can be clinically indistinguishable, they are mechanistically different. In anaphylactoid reactions, only preformed mediators are released, of which histamine may be the most clinically important. ⋯ Anaphylactoid reactions may occur commonly under anaesthesia in response to many drugs, including induction agents, some opiates, plasma expanders, and curariform relaxants. Anaphylactic reactions are far less common than anaphylactoid reactions, but they nevertheless represent more than half of the life-threatening reactions that occur in anaesthetic practice. Muscle relaxants are the most frequently implicated class of drugs; suxamethonium is the most common agent implicated in anaphylactic reactions during anaesthesia, but even drugs without apparent chemical histamine release (i.e., vecuronium) are frequently implicated in anaphylactic reactions.