British journal of anaesthesia
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Comparative Study Clinical Trial Controlled Clinical Trial
Predicting outcome after cardiac surgery: comparison of global haemodynamic and tonometric variables.
To compare how outcome can be predicted from global haemodynamic compared with regional perfusion-related variables (gastric intramucosal pH (pHi) and intramucosal-arterial PCO2 difference (delta PCO2)), we measured global haemodynamics, gastric pHi and delta PCO2 in 68 haemodynamically compromised patients after cardiac surgery on admission to the intensive care unit (ICU) and 12 h later. Overall mortality rate in the ICU was 19.1%. ⋯ Our data showed that global, routinely monitored, haemodynamic variables are better early predictors of outcome after cardiac surgery than regional, tonometric variables. This conclusion does not support hypoperfusion of the gastrointestinal tract as an early determinant of outcome after cardiac surgery.
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We have compared three treatment strategies, that aim to prevent repetitive alveolar collapse, for their effect on gas exchange, lung mechanics, lung injury, protein transfer into the alveoli and surfactant system, in a model of acute lung injury. In adult rats, the lungs were ventilated mechanically with 100% oxygen and a PEEP of 6 cm H2O, and acute lung injury was induced by repeated lung lavage to obtain a PaO2 value < 13 kPa. Animals were then allocated randomly (n = 12 in each group) to receive exogenous surfactant therapy, ventilation with high PEEP (18 cm H2O), partial liquid ventilation or ventilation with low PEEP (8 cm H2O) (ventilated controls). ⋯ Conversion of active to non-active surfactant components increased significantly in the partial liquid ventilation group and in the group ventilated with high PEEP. In the surfactant group and partial liquid ventilation groups, less lung injury was found compared with the ventilated control group and the group ventilated with high PEEP. We conclude that although all three strategies improved PaO2 to > 50 kPa, the impact on protein transfer into the alveoli, surfactant system and lung injury differed markedly.
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Randomized Controlled Trial Clinical Trial
A low concentration of nitrous oxide reduces dyspnoea produced by a combination of hypercapnia and severe elastic load.
We have measured how a low concentration of nitrous oxide affected respiratory sensation and ventilation. Severe dyspnoea was induced in nine normal subjects by a combination of hypercapnia and inspiratory elastic load (50 cm H2O litre-1). Subjects were asked to rate their sensation of respiratory discomfort using a visual analogue scale (VAS) while breathing either 20% nitrous oxide or 20% nitrogen gas mixture. ⋯ Inhalation of 20% nitrous oxide reduced the sensation of respiratory discomfort from a median VAS score of 6.5 (range 5.0-8.1) before inhalation to 3.6 (2.4-5.9) during inhalation (P < 0.05). There was no significant change in minute ventilation but tidal volume increased during inhalation of 20% nitrogen did not alter VAS scores or ventilatory variables. We found that a low concentration of nitrous oxide greatly alleviated the intensity of dyspnoea without changing respiratory load compensation.
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The aim of this study was to identify a possible relationship between haemodynamic variables, auditory evoked potentials (AEP) and inspired fraction of isoflurane (ISOFl). Two different models (isoflurane and mean arterial pressure) were identified using the fuzzy inductive reasoning (FIR) methodology. A fuzzy model is able to identify non-linear and linear components of a causal relationship by means of optimization of information content of available data. ⋯ The FIR methodology identified those variables among the input variables (MAP, HR, CO2ET, DAI or ISOFl) that had the highest causal relation with the output variables (ISOFl and MAP). The variables with highest causal relation constitute the ISOFl and MAP models. The isoflurane model predicted the given anaesthetic dose with a mean error of 12.1 (SD 10.0)% and the mean arterial pressure model predicted MAP with a mean error of 8.5 (7.8)%.