Perioperative use of beta-blockers

Perioperative beta-blocker therapy has been considered a mainstay of perioperative cardioprotection in patients with or at risk of coronary artery diseases. However, current recommendations for perioperative beta blockade are based mainly on the findings of trials with inadequate methodology and data analysis. The recently published results of the first adequately powered large controlled randomized trial on the efficacy and safety of perioperative beta-blocker therapy confirmed the benefit of such therapy on the perioperative incidence of non-fatal myocardial infarctions. However, such a benefit occurred at the expense of increased total mortality and increased incidence of stroke, negating any beneficial effect. A subsequently published meta-analysis confirmed, in large part, these findings. Given these recent publications, most of the current recommendations for perioperative beta-blocker therapy are no longer supported by evidence, therefore respective revision is needed

Изменение характеристик потока в мультициклоне при различной установке циклонных элементов

В работе представлены результаты численного моделирования потоков в корпусемультициклона, в двух моделях расположения циклонных элементов. Целью работы является возможность оптимизации расположения входов полуулиточных патрубков циклонных элементов в батарейном циклоне по первой и второй моделям. Они позволяют также более точно учесть гидравлическое сопротивление аппарата при определении наиболее эффективного расположения циклонных элементов.The paper presents the results of numerical simulation of flows in the case of multicyclone, in two models of the location of the cyclone elements. The aim of this work is the possibility of optimizing the location of entrances palowitch nozzles cyclone elements in the battery cyclone the first and second models. They also allow for a more accurate account of the hydraulic resistance of the device when determining the most effective location of cyclonic elements

Expiratory automatic endotracheal tube compensation reduces dynamic hyperinflation in a physical lung model

INTRODUCTION: The effect of expiratory endotracheal tube (ETT) resistance on dynamic lung inflation is unknown. We hypothesized that ETT resistance causes dynamic lung hyperinflation by impeding lung emptying. We further hypothesized that compensation for expiratory ETT resistance by automatic tube compensation (ATC) attenuates dynamic lung hyperinflation. METHODS: A ventilator equipped with the original ATC mode and operating in a pressure-targeted mode was connected to a physical lung model that consists of four equally sized glass bottles filled with copper wool. Inspiratory pressure, peak expiratory flow, trapped lung volume and intrinsic positive end-expiratory pressure (PEEP) were assessed at combinations of four inner ETT diameters (7.0, 7.5, 8.0 and 8.5 mm), four respiratory rates (15, 20, 25 and 30/minute), three inspiratory pressures (3.0, 4.5 and 6.0 cmH2O) and four lung compliances (113, 86, 58 and 28 ml/cmH2O). Intrinsic PEEP was measured at the end of an expiratory hold manoeuvre. RESULTS: At a given test lung compliance, inspiratory pressure and ETT size, increasing respiratory rates from 15 to 30/minutes had the following effects: inspiratory tidal volume and peak expiratory flow were decreased by means of 25% (range 0% to 51%) and 11% (8% to 12%), respectively; and trapped lung volume and intrinsic PEEP were increased by means of 25% (0% to 51%) and 26% (5% to 45%), respectively (all P < 0.025). At otherwise identical baseline conditions, introduction of expiratory ATC significantly attenuated (P < 0.025), by approximately 50%, the respiratory rate-dependent decreases in inspiratory tidal volume and the increases in trapped lung volume and intrinsic PEEP. CONCLUSIONS: In a lung model of pressure-targeted ventilation, expiratory ETT resistance caused dynamic lung hyperinflation during increases in respiratory rates, thereby reducing inspiratory tidal volume. Expiratory ATC attenuated these adverse effects

Problems of subgroup analysis in randomized controlled trial

Multiple subgroup analyses of the same data increase the risk of generating false positive findings. All outcomes and planned subgroup analyses should thus be prespecified and described in the original trial registry. When outcome changes during an ongoing trial seem justifiable, publications must disclose and explain such changes

&quot;We Hear What You Are Saying, but…&quot; Competing Interests

We read with interest as Ramsingh et al. 1 described their study comparing the efficacy of point-of-care ultrasound versus auscultation by using a stethoscope in determining proper endotracheal/bronchial positioning. We have used ultrasound to answer questions about endotracheal tube placement, possible pneumothorax, and difficult airway anatomy-all of which have been well-described by Kristensen. 2 Clearly, ultrasound offers advantages in very specific situations. We applaud the authors for describing a new technique in confirming the laterality of bronchial intubation. The authors rightly recognize the limitations of their study, especially the fact that auscultation and ultrasound were compared in isolation. In the actual clinical setting of other monitors including capnography, peak airway pressures, observation of chest excursion, and endotracheal tube humidification, it is hard to imagine that the addition of ultrasonography offers any significant advancement in patient safety for the following reasons: first, the authors state that the technique is &quot;quick,&quot; which is then defined as &quot;less than 4 min.&quot; In terms of airway management, 4 min strikes us as a long time. Depending on habitus and other pulmonary pathologies, the safe apneic time of a given patient may preclude ultrasound examination. Second, ultrasound is expensive, and availability is a legitimate concern. Even though we are employed in a large academic center that has many portable ultrasounds, the demand frequently exceeds the supply of devices. Third, compared to a stethoscope, ultrasounds are currently more cumbersome, breakable, and energy-source dependent. Fourth, ultrasounds do not fill every role our stethoscopes play; for example, they cannot diagnose bronchospasm or flash pulmonary edema. In summary, while we respect the application of this technology, we do not yet see how it can be a point-of-care intubations, and in only two patients, the tip of the ETT was between 2 and 3 cm proximal to the carina (0.65%). In the control group, there were seven endobronchial intubations (2.7%); in eight patients, the tip of the ETT was less than 2 cm proximal to the carina (3.0%); and in 20 patients, the tip of the ETT was between 2 and 3 cm proximal to the carina (7.6%). In a prospective randomized trial, chest auscultation, observation and palpation of chest movements, and check of the ETT tube insertion depth on the centimeter scale basis were used for detecting or excluding endobronchial intubation. 1 Importantly, the test results were independent of the anesthesiologist&apos;s experience. Noteworthy, had the 21/23-cm rule been followed, not a single patient would have been endobronchially intubated. However, it would have resulted in a shorter than the recommended safety distance of 2.5 cm between the distal end of the ETT and the carina in 24 of 118 women (20%) and 7 of 42 men (18%). If a 20/22-instead of the 21/23-cm rule had been used, the recommended safety distance would have been achieved in 108 of 118 (92%) women and in all 42 men. The shortest correct intubation depth was 19 cm in 10 women with an average height of 157 cm and a body mass index of 28.4 kg/ m 2 . These findings suggest that in general, using the 20/22-cm rule (with the possible exception of using 19 cm in small women with a higher body mass index) might be safer than using the &quot;traditional&quot; 21/23-cm rule. The overall evidence suggests that the 21/23-cm method (possibly to be replaced by the 20/22-cm method) allows rapid and reliable assessment of the likelihood of endobronchial intubation without the need for advanced clinical experience and for additional technical equipment and specialized training. The practicing clinician should be aware of a &quot;low-tech&quot; alternative method of assessing the likelihood of endobronchial intubation of equal sensitivity and specificity as the ultrasound method but without its limitations. When next investigating the effectiveness of a technique in assessing the ETT position, it might be more appropriate to choose the 21/23-cm method as the &quot;accepted&quot; standard for comparison rather than chest auscultation