Minerva anestesiologica
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Minerva anestesiologica · Jun 2006
ReviewVolumetric capnography in the mechanically ventilated patient.
Expiratory capnogram provides qualitative information on the waveform patterns associated with mechanical ventilation and quantitative estimation of expired CO2. Volumetric capnography simultaneously measures expired CO2 and tidal volume and allows identification of CO2 from 3 sequential lung compartments: apparatus and anatomic dead space, from progressive emptying of alveoli and alveolar gas. Lung heterogeneity creates regional differences in CO2 concentration and sequential emptying contributes to the rise of the alveolar plateau and to the steeper the expired CO2 slope. ⋯ Calculations derived from volumetric capnography are useful to suspect pulmonary embolism at the bedside. Alveolar dead space is large in acute lung injury and when the effect of positive end-expiratory pressure (PEEP) is to recruit collapsed lung units resulting in an improvement of oxygenation, alveolar dead space may decrease, whereas PEEP-induced overdistension tends to increase alveolar dead space. Finally, measurement of physiologic dead space and alveolar ejection volume at admission or the trend during the first 48 hours of mechanical ventilation might provide useful information on outcome of critically ill patients with acute lung injury or acute respiratory distress syndrome.
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Minerva anestesiologica · Jun 2006
Review Comparative StudyLow vs high positive end-expiratory pressure in the ventilatory management of acute lung injury.
Positive end-expiratory pressure (PEEP) has become an essential component of the care of many critically ill patients who require ventilatory support. The application of PEEP is expected to improve lung mechanics and gas exchange as it recruits lung volume. ⋯ Although the data from those animal studies and clinical trials could be seen as very convincing, there are insufficient data to propose an universal approach for the use of PEEP in patients with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). In this article I will review the basic mechanisms of PEEP and the current knowledge of the effects of PEEP on the evolution and outcome of ALI/ARDS.
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The recording of dead space will give information on how much of total ventilation that reaches both ventilated and perfused alveoli and thus allows gas exchange between alveoli and pulmonary blood. Realising that CO2 retention can be an effect not only of low total ventilation but also of increased dead space is one important information. Moreover, dead space will give insight into the matching of ventilation and perfusion. ⋯ However, both are subjected to potential errors that have to be considered to make a dead space recording meaningful. A correct measurement and calculation of the dead space will give valuable information on the ventilatory support of the critically ill patient and can also be a valuable diagnostic tool. It should therefore not be forgotten in the intensive care setting.
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Minerva anestesiologica · Jun 2006
ReviewMicrocirculatory recruitment maneuvers correct tissue CO2 abnormalities in sepsis.
The rises in tissue partial pressure of carbon dioxide have been observed in critically ill patients with shock and sepsis for a long time and have been proposed to be an earlier and more reliable marker of tissue hypoxia than traditional markers. However, the mechanisms leading to those increases, especially in sepsis and endotoxemia, are not well understood. Recent studies provided further data, supporting the idea that the origin of those increases in partial pressure of CO2 in sepsis as being caused by microcirculatory perfusion deficit resulting in mitochondrial depression by time. ⋯ Recent findings support the idea that the progression from early to severe sepsis is accompanied or possibly even caused by microcirculatory dysfunction, which leads to mitochondrial dysfunction by time. Therefore early identification of microcirculatory dysfunction and correction with microcirculatory recruitment maneuvers are needed to ensure adequate microcirculatory perfusion and tissue oxygenation. Microcirculatory imaging, such as SDF imaging technique, appears to be a very useful tool for this task and its combination together with other systemic and regional tissue oxygenation measurements may provide more information regarding the tissue oxygenation and will be a very promising tool for microcirculatory researchers and the management of critically ill patients at the bedside.
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Minerva anestesiologica · Jun 2006
ReviewPreoperative parental information and parents' presence at induction of anaesthesia.
Preoperative preparation of paediatric patients and their environment in order to prevent anxiety is an important issue in paediatric anaesthesia. Anxiety in paediatric patients may lead to immediate negative postoperative responses. When a child undergoes surgery, information about the child's anaesthesia must be provided to parents who are responsible for making informed choices about healthcare on their child's behalf. ⋯ The issue of parental presence during induction of anaesthesia has been a controversial topic for many years. Potential benefits from parental presence at induction include reducing or avoiding the fear and anxiety that might occur in both the child and its parents, reducing the need for preoperative sedatives, and improving the child's compliance even if other studies showed no effects on the anxiety and satisfaction level. The presence of other figures such as clowns in the operating room, together with one of the child's parents, is an effective intervention for managing child and parent anxiety during the preoperative period.