Anaesthesia
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Clinical Trial
A noninvasive method for evaluating the effect of thoracotomy on shunt and ventilation perfusion inequality.
A new noninvasive method was used to evaluate gas exchange in 12 patients undergoing thoracotomy for a variety of surgical procedures. A plot of inspired oxygen partial pressure versus oxygen saturation was analysed to calculate the independent contribution of shunt and intermediate ventilation/perfusion ratio which occurs during general anaesthesia for thoracotomy. A model based on the inspired to arterial oxygen difference involving the shunt equation was used to show how the relationship between inspired oxygen partial pressure and oxygen saturation could be used to derive two parameters of oxygen exchange, the virtual shunt and an index of low ventilation/perfusion ratio. ⋯ Thoracotomy caused a mean increase in shunt from 13.8% to 20.8% and a worsening ventilation/perfusion ratio from 0.5 to 0.2, the magnitude of which depended on the underlying pathology. In two patients, the ventilation/perfusion ratio decreased to less than 0.1. The method enables the prediction of oxygen saturation at different inspired oxygen partial pressures and allows the two components of gas exchange to be isolated using simple routine measurements of inspired oxygen and pulse oximetry.
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The Oxyvent is an anaesthetic machine designed specifically for use in the developing world and difficult situations. It is made up of four components, each of which has, in its own right, already proved to be of great value in difficult situations. These are the drawover system, the Penlon Manley Multivent Ventilator, the DeVilbiss Oxygen Concentrator and the air compressor. ⋯ The Oxyvent can be used to provide anaesthesia in the absence of electricity or oxygen or both. It is simple, robust and easily serviceable. It is versatile and can be used both as an anaesthetic machine in the operating theatre and as a ventilator in an intensive care unit.
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When volatile anaesthetics are used in a closed breathing system it is usually assumed that inflow of anaesthetic to the system matches uptake by the patient. Early laboratory reports on the interactions between sevoflurane and soda lime cast doubt on that assumption. We have measured the loss of sevoflurane, desflurane and isoflurane from a closed breathing system and found no differences of consequences.
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Splanchnic ischaemia is thought to be of central importance in the development of multi-organ failure and hence death in critically ill patients. It has been suggested that the arterial to gastric intramucosal pH gradient and the difference in partial pressure of carbon dioxide between gastric mucosa and arterial blood are more sensitive markers of splanchnic ischaemia than gastric intramucosal pH itself and thus should be predictors of mortality in the critically ill. We studied 62 critically ill patients within 6 h of admission to the intensive care unit and found no significant difference at 0, 12 or 24 h after admission to the study in either the arterial to gastric intramucosal pH gradient or the difference in partial pressure of carbon dioxide between gastric mucosa and arterial blood between survivors and nonsurvivors. We conclude that in contrast to gastric intramucosal pH neither the arterial to gastric intramucosal pH gradient nor the difference in partial pressure of carbon dioxide between gastric mucosa and arterial blood distinguish survivors from nonsurvivors.
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An 11-year-old boy suffered an inadvertent dural puncture during placement of an epidural catheter for postoperative analgesia. He developed symptoms of mild headache only, but severe and protracted orthostatic nausea and dizziness, which eventually resolved completely following epidural blood patch. ⋯ The reported incidence of headache following dural puncture in children is low. It may be that the manifestations are different from those of adults and that the true incidence of symptoms related to leakage of cerebrospinal fluid is higher in children than currently recognised.