Minerva anestesiologica
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Minerva anestesiologica · May 2000
ReviewTime to reconsider the pre-oxygenation during induction of anaesthesia.
Atelectasis is a frequent finding in paralysed and mechanically ventilated patients. Atelectasis, causing shunt, impairs oxygenation and could contribute to postoperative pulmonary complications. Pre-oxygenation used during anaesthesia induction causes atelectasis. A lowering of oxygen fraction from 100% to 80% does not shorten the safety time of apnoea period, particularly useful for a difficult intubation, but it reduces drastically the atelectasis incidence.
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Sevoflurane and Desflurane are relatively new halogenated agents which make induction and control of depth of anaesthesia easier, recovery rapid and of good quality and they have less side-effects and toxicity. In children sevoflurane could replace halothane because it provides smooth and rapid induction with less cardiovascular depression and arrhythmias. Desflurane is not used because of its pungent odour. In adults sevoflurane could be preferred to desflurane because it allows rapid induction and laryngeal mask insertion or tracheal intubation without myorelaxants, a similar time of recovery, no clinical evidence for renal and hepatic toxicity, no more costs for anaesthesia for a lower MAC.
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Minerva anestesiologica · May 2000
ReviewCytopathic hypoxia. A concept to explain organ dysfunction in sepsis.
The most common cause of death in patients with sepsis is the multiple organ dysfunction syndrome (MODS). One important factor underlying the pathogenesis of MODS may be sepsis-induced alterations in cellular energy metabolism due to acquired intrinsic derangements in cellular respiration, a phenomenon that might be called "cytopathic hypoxia". A number of different biochemical mechanisms have been postulated to account for cytopathic hypoxia in sepsis, including reversible inhibition of cytochrome oxidase by nitric oxide, irreversible inhibition of one or more mitochondrial respiratory complexes by peroxynitrite, and activation of the nuclear enzyme, poly-(ADP-ribosyl)-polymerase.
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It is well established that general anesthesia, with or without paralysis, causes profound changes in respiratory function. From a clinical point of view, the more important consequence of this impairment is a decreased efficiency of gas exchange, with a decreased blood oxygenation. The main reason of this respiratory embarrassment is the intraoperative occurrence of atelectasis, mainly in the dependent lung regions. ⋯ As the anesthesia-induced atelectasis are also present in the postoperative period, this ventilatory approach may also be used to prevent this condition. In obese patients PEEP seems to have a major effectiveness than in normal subjects, with an improvement of lung volumes, respiratory mechanics, gas exchange and an occurrence of recruitment. However, further studies are necessary to define optimal value of PEEP and tidal volume for different types of patients.