Anaesthesia
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Observational Study
The effect of coughing at extubation on oxygenation in the post-anaesthesia care unit.
We prospectively studied 84 patients to investigate whether there is a relationship between coughing during emergence and tracheal extubation, and impaired oxygenation in the post-anaesthesia care unit. Our primary outcome measure was a change in the alveolar-arterial oxygen partial pressure gradient ((A-a)DO2 ) between time A (during general anaesthesia) and time B (1 h after extubation). ⋯ An overall linear regression model was not predictive for the observed change (adjusted R(2) = 0.01, p = 0.31) and nor were any of the individual predictors studied, including subjective cough score (p = 0.33), number of coughs (p = 0.95) and duration of coughing (p = 0.39). Despite the abnormal cough that occurs while tracheally intubated, we have been unable to demonstrate that coughing at extubation is associated with impaired oxygenation in the immediate postoperative period.
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Randomized Controlled Trial
The effects of Patent Blue dye on peripheral and cerebral oxyhaemoglobin saturations.
We measured the effect of Patent Blue dye on oxyhaemoglobin saturations after injection into breast tissue: 40 women had anaesthesia for breast surgery maintained with sevoflurane or propofol (20 randomly allocated to each). Saturations were recorded with a digital pulse oximeter, in arterial blood samples and with a cerebral tissue oximeter before dye injection and 10, 20, 30, 40, 50, 60, 75, 90, 105 and 120 min afterwards. ⋯ The falsely reduced oximeter readings persisted for at least 2 h. The mean (SD) intra-operative digital pulse oxyhaemoglobin readings were lower with sevoflurane than propofol, 97.8 (1.2) % and 98.8 (1.0) %, respectively, p < 0.0001.
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Preconditioning has been shown to reduce myocardial damage caused by ischaemia-reperfusion injury peri-operatively. Volatile anaesthetic agents have the potential to provide myocardial protection by anaesthetic preconditioning and, in addition, they also mediate renal and cerebral protection. A number of proof-of-concept trials have confirmed that the experimental evidence can be translated into clinical practice with regard to postoperative markers of myocardial injury; however, this effect has not been ubiquitous. ⋯ Data from recent meta-analyses in cardiac anaesthesia are also not conclusive regarding intra-operative volatile anaesthesia. These inconclusive clinical results have led to great variability currently in the type of anaesthetic agent used during cardiac surgery. This review summarises experimentally proposed mechanisms of anaesthetic preconditioning, and assesses randomised controlled clinical trials in cardiac anaesthesia that have been aimed at translating experimental results into the clinical setting.