Anaesthesia
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Comparative Study
Comparison of acoustic and impedance methods with mask capnometry to assess respiration rate in obese patients recovering from general anaesthesia.
Respiratory depression, a potentially serious complication after general anaesthesia, can be detected promptly by close monitoring of both oxygen saturation and respiratory rate. Obese patients have morphological changes that may impair the reliability of monitoring devices. In this study, respiration rate was simultaneously recorded every second for up to 60 min using a computer in 30 adult obese patients (body mass index ≥ 35 kg.m(-2)), by three methods: acoustic; thoracic impedance; and capnometry via a facemask (Capnomask, reference method). ⋯ The proportion of respiration rate values obtained with the acoustic method and impedance that differed by at least 10% or 20% for more than 15 s were 11% vs. 23% and 2% vs. 6%, respectively (p = 0.0009 for both comparisons). The acoustic sensor was well tolerated, while the facemask was pulled off on several occasions by four (13%) agitated patients. In obese patients requiring close monitoring of respiration rate, the acoustic method may be more precise than thoracic impedance and better tolerated than capnometry with a facemask.
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Pulmonary hypertension is a complex disorder of the pulmonary vasculature that leads to increased peri-operative morbidity and mortality. Non-cardiac surgery constitutes a significant risk in patients with pulmonary hypertension. ⋯ A thorough understanding of the pathophysiology, the severity of the disease and its treatment modalities is required to deliver optimal peri-operative care. This review provides an evidence-based overview of the definition, classification, pathophysiology, diagnosis and treatment of pulmonary hypertension and focuses on the peri-operative management and treatment of pulmonary hypertensive crises in a non-cardiac setting.
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Recent research in the management of haemorrhage has led to several changes in clinical practice. Evidence is accumulating that point-of-care testing results in fewer transfusions, improved patient outcomes, and reduced hospital costs. ⋯ A change in philosophy is required, from performing testing only when there is an obvious bleeding problem, towards the concept of routinely monitoring high-risk patients throughout the surgical procedure. This informs clinical practice, establishes normal ranges for that population, identifies patients at risk and allows early identification and treatment of evolving coagulopathy.
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There has been an explosion of interest in the ability of tranexamic acid to reduce morbidity and mortality in surgical and traumatic bleeding. Tranexamic acid has been shown to reduce mortality due to traumatic bleeding by a third, without apparent safety issues. It is now clearly established that intravenous tranexamic acid reduces blood loss in patients with surgical bleeding and the need for transfusion. ⋯ However, clinical studies suggest that there is no increased efficacy in using a higher dose, and that a dose of 1 g intravenously in an adult patient has maximal efficacy, which is not increased by higher doses. The CRASH-2 trauma trial clearly showed no increase in thrombotic events after its use in trauma, indeed there was a significant reduction in myocardial infarction. However, trials of tranexamic acid in surgery have failed to adequately study its effects on the risk of postoperative venous and possible reduction in arterial thrombo-embolism, and this needs to be the subject of future research.
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There is a considerable difference between the mechanism of action of the lysine analogues, tranexamic acid and epsilon-aminocaproic acid, and the serine protease inhibitor aprotinin. Aprotinin acts to inactivate free plasmin, but with little effect on bound plasmin, whereas the lysine analogues are designed to prevent excessive plasmin formation by fitting into plasminogen's lysine-binding site to prevent the binding of plasminogen to fibrin. Aprotinin is associated with a reduction in bleeding and transfusion requirements following major surgery, and has a dose-response profile, compared with no dose-response effect in the one study investigating tranexamic acid in cardiac surgical patients. Following its withdrawal in 2007, which is explained in detail in this review, the regulators have now licensed aprotinin for myocardial revascularisation only, which is relatively low-risk for bleeding.