Articles: general-anesthesia.
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J R Coll Surg Edinb · Oct 2001
ReviewHypoxia and surgical patients--prevention and treatment of an unnecessary cause of morbidity and mortality.
Hypoxia is a common phenomenon peri-operatively. Although mild hypoxaemia of short duration is likely to have little effect more severe and prolonged hypoxaemia can seriously affect surgical outcome. Rational use of oxygen therapy may limit these adverse effects.
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In order to provide optimum intracranial operating conditions for neurosurgery, anaesthetists must have a thorough understanding of brain physiology and how this is affected by pathology and anaesthetic drugs and techniques. This article discusses the current understanding of cerebral vascular physiology and how novel neuroanaesthetic drugs and techniques affect it.
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Approximately 1-2% of all anesthetized patients are morbidly obese (body mass index > 35 kg/m2). The perioperative mortality is significantly elevated (up to 20%) compared with lean patients. Morbidly obese patients are at high risk for cardiopulmonary dysfunction. Difficult airway management is reported in 13-20% of obese patients. Hypoxia is often observed due to faster desaturation during induction of anesthesia. After surgery, patients are endangered by a high incidence of obstructive sleep apnea syndrome (50%), pulmonary atelectasis (5%) and acute pulmonary embolism (5-12%). ⋯ Postoperative admission on an intensive care unit of morbidly obese patients is based upon concomitant diseases and surgical requirements. The main reason for admission is an inadequate pulmonary gas exchange. This interdisciplinary approach will reduce the risk of anesthesia and avoid complications in morbidly obese patients.
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Almost a century ago, Meyer and Overton discovered a linear relationship between the potency of anaesthetic agents to induce general anaesthesia and their ability to accumulate in olive oil. Similar correlations between anaesthetic potency and lipid solubility were later reported from investigations on various experimental model systems. However, exceptions to the Meyer-Overton correlation exist in all these systems, indicating that lipid solubility is an important, but not the sole determinant of anaesthetic action. ⋯ Unconsciousness, amnesia, analgesia, loss of sensory processing and the depression of spinal motor reflexes are important components. It was not realised until very recently that different molecular mechanisms might underlie these different components. These findings challenge traditional views, such as the assumption that one anaesthetic can be freely replaced by another.