Supplemental perioperative oxygen to reduce the incidence of surgical wound infection

Background
Inadvertent perioperative hypothermia is a phenomenon that can occur as a result of the suppression of the central mechanisms of temperature regulation due to anaesthesia, and of prolonged exposure of large surfaces of skin to cold temperatures in operating rooms. Inadvertent perioperative hypothermia has been associated with clinical complications such as surgical site infection and wound-healing delay, increased bleeding or cardiovascular events. One of the most frequently used techniques to prevent inadvertent perioperative hypothermia is active body surface warming systems (ABSW), which generate heat mechanically (heating of air, water or gels) that is transferred to the patient via skin contact.

Objectives
To assess the effectiveness of pre- or intraoperative active body surface warming systems (ABSW), or both, to prevent perioperative complications from unintended hypothermia during surgery in adults.

Search methods
We searched the Cochrane Central Register of Controlled Trials (CENTRAL; Issue 9, 2015); MEDLINE (PubMed) (1964 to October 2015), EMBASE (Ovid) (1980 to October 2015), and CINAHL (Ovid) (1982 to October 2015).

Selection criteria
We included randomized controlled trials (RCTs) that compared an ABSW system aimed at maintaining normothermia perioperatively against a control or against any other ABSW system. Eligible studies also had to include relevant clinical outcomes other than measuring temperature alone.

Data collection and analysis
Several authors, by pairs, screened references and determined eligibility, extracted data, and assessed risks of bias. We resolved disagreements by discussion and consensus, with the collaboration of a third author.

Main results
We included 67 trials with 5438 participants that comprised 79 comparisons. Forty-five RCTs compared ABSW versus control, whereas 18 compared two different types of ABSW, and 10 compared two different techniques to administer the same type of ABSW. Forced-air warming (FAW) was by far the most studied intervention.

Trials varied widely regarding whether the interventions were applied alone or in combination with other active (based on a different mechanism of heat transfer) and/or passive methods of maintaining normothermia. The type of participants and surgical interventions, as well as anaesthesia management, co-interventions and the timing of outcome measurement, also varied widely. The risk of bias of included studies was largely unclear due to limitations in the reports. Most studies were open-label, due to the nature of the intervention and the fact that temperature was usually the principal outcome. Nevertheless, given that outcome measurement could have been conducted in a blinded manner, we rated the risk of detection and performance bias as high.

The comparison of ABSW versus control showed a reduction in the rate of surgical site infection (risk ratio (RR) 0.36, 95% confidence interval (CI) 0.20 to 0.66; 3 RCTs, 589 participants, low-quality evidence). Only one study at low risk of bias observed a beneficial effect with forced-air warming on major cardiovascular complications (RR 0.22, 95% CI 0.05 to 1.00; 1 RCT with 12 events, 300 participants, low-quality evidence) in people at high cardiovascular risk. We found no beneficial effect for mortality. ABSW also reduced blood loss during surgery but the magnitude of this effect seems to be irrelevant (MD -46.17 mL, 95% CI -82.74 to -9.59; I² = 78%; 20 studies, 1372 participants). The same conclusion applies to total fluids infused during surgery (MD -144.49 mL, 95% CI -221.57 to -67.40; I² = 73%; 24 studies, 1491 participants). These effects did not translate into a significant reduction in the number of participants being transfused or the average amount of blood transfused. ABSW was associated with a reduction in shivering (RR 0.39, 95% CI 0.28 to 0.54; 29 studies, 1922 participants) and in thermal comfort (standardized mean difference (SMD) 0.76, 95% CI 0.29 to 1.24; I² = 77%, 4 trials, 364 participants).

For the comparison between different types of ABSW system or modes of administration of a particular type of ABSW, we found no evidence for the superiority of any system in terms of clinical outcomes, except for extending systemic warming to the preoperative period in participants undergoing major abdominal surgery (one study at low risk of bias).

There were limited data on adverse effects (the most relevant being thermal burns). While some trials included a narrative report mentioning that no adverse effects were observed, the majority made no reference to it. Nothing so far suggests that ABSW involves a significant risk to patients.

Authors' conclusions
Forced-air warming seems to have a beneficial effect in terms of a lower rate of surgical site infection and complications, at least in those undergoing abdominal surgery, compared to not applying any active warming system. It also has a beneficial effect on major cardiovascular complications in people with substantial cardiovascular disease, although the evidence is limited to one study. It also improves patient's comfort, although we found high heterogeneity among trials. While the effect on blood loss is statistically significant, this difference does not translate to a significant reduction in transfusions. Again, we noted high heterogeneity among trials for this outcome. The clinical relevance of blood loss reduction is therefore questionable. The evidence for other types of ABSW is scant, although there is some evidence of a beneficial effect in the same direction on chills/shivering with electric or resistive-based heating systems. Some evidence suggests that extending systemic warming to the preoperative period could be more beneficial than limiting it only to during surgery. Nothing suggests that ABSW systems pose a significant risk to patients.

The difficulty in observing a clinically-relevant beneficial effect with ABSW in outcomes other than temperature may be explained by the fact that many studies applied concomitant procedures that are routinely in place as co-interventions to prevent hypothermia, whether passive or active warming systems based in other physiological mechanisms (e.g. irrigation fluid or gas warming), as well as a stricter control of temperature in the context of the study compared with usual practice. These may have had a beneficial effect on the participants in the control group, leading to an underestimation of the net benefit of ABSW.

Active body surface warming systems for preventing complications caused by inadvertent perioperative hypothermia in adults

Wound tissue oxygen tension predicts the risk of wound infection in surgical patients

The World Health Organization (WHO) and the Centre
for Disease Control and Prevention (CDC) recently published guidelines
for the prevention of surgical site infection. The WHO guidelines,
if implemented worldwide, could have an immense impact on our practices
and those of the CDC have implications for healthcare policy in
the United States. Our aim was to review the strategies for prevention of periprosthetic
joint infection in light of these and other recent guidelines. Cite this article: Bone Joint J 2017;99-B(4
Supple B):3–10.

Prevention of periprosthetic joint infection: new guidelines.

Background
Inadvertent perioperative hypothermia (a drop in core temperature to below 36°C) occurs because of interference with normal temperature regulation by anaesthetic drugs, exposure of skin for prolonged periods and receipt of large volumes of intravenous and irrigation fluids. If the temperature of these fluids is below core body temperature, they can cause significant heat loss. Warming intravenous and irrigation fluids to core body temperature or above might prevent some of this heat loss and subsequent hypothermia.

Objectives
To estimate the effectiveness of preoperative or intraoperative warming, or both, of intravenous and irrigation fluids in preventing perioperative hypothermia and its complications during surgery in adults.

Search methods
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2014, Issue 2), MEDLINE Ovid SP (1956 to 4 February 2014), EMBASE Ovid SP (1982 to 4 February 2014), the Institute for Scientific Information (ISI) Web of Science (1950 to 4 February 2014), Cumulative Index to Nursing and Allied Health Literature (CINAHL) EBSCOhost (1980 to 4 February 2014) and reference lists of identified articles. We also searched the Current Controlled Trials website and ClinicalTrials.gov.

Selection criteria
We included randomized controlled trials or quasi-randomized controlled trials comparing fluid warming methods versus standard care or versus other warming methods used to maintain normothermia.

Data collection and analysis
Two review authors independently extracted data from eligible trials and settled disputes with a third review author. We contacted study authors to ask for additional details when needed. We collected data on adverse events only if they were reported in the trials.

Main results
We included in this review 24 studies with a total of 1250 participants. The trials included various numbers and types of participants. Investigators used a range of methods to warm fluids to temperatures between 37°C and 41°C. We found that evidence was of moderate quality because descriptions of trial design were often unclear, resulting in high or unclear risk of bias due to inappropriate or unclear randomization and blinding procedures. These factors may have influenced results in some way. Our protocol specified the risk of hypothermia as the primary outcome; as no trials reported this, we decided to include data related to mean core temperature. The only secondary outcome reported in the trials that provided useable data was shivering. Evidence was unclear regarding the effects of fluid warming on bleeding. No data were reported on our other specified outcomes of cardiovascular complications, infection, pressure ulcers, bleeding, mortality, length of stay, unplanned intensive care admission and adverse events.

Researchers found that warmed intravenous fluids kept the core temperature of study participants about half a degree warmer than that of participants given room temperature intravenous fluids at 30, 60, 90 and 120 minutes, and at the end of surgery. Warmed intravenous fluids also further reduced the risk of shivering compared with room temperature intravenous fluids

Investigators reported no statistically significant differences in core body temperature or shivering between individuals given warmed and room temperature irrigation fluids.

Authors' conclusions
Warm intravenous fluids appear to keep patients warmer during surgery than room temperature fluids. It is unclear whether the actual differences in temperature are clinically meaningful, or if other benefits or harms are associated with the use of warmed fluids. It is also unclear if using fluid warming in addition to other warming methods confers any benefit, as a ceiling effect is likely when multiple methods of warming are used.

/pdf/warming-of-intravenous-and-irrigation-fluids-for-preventing-2fbcycytg5.pdf

Warming of intravenous and irrigation fluids for preventing inadvertent perioperative hypothermia

Background and aim of the work: Perioperative hypothermia is a frequent occurrence and can lead to several complications, which adversely affect the patient’s outcome, expecially in high risk patient. Nonetheless, central temperature is not frequently monitored in the clinical routine. The aim of this work is to make the point on complications, monitoring techniques, prevention and treatment of mild perioperative hypothermia. Methods: We reviewed literature on cardiovascular, haemorragic, infectious, and other clinical consequences of mild intraoperative hypothermia, epidemiology and techniques, of temperature monitoring and efficacy of different approaches for the prevention and treatment of mild hypothermia. Results: Cardiovascular, haemorragic and infectious complications are significantly more frequent in hypothermic than in normothermic patients. Elderly and high risk patients are more prone to develop perioperative hypotherma, and are more liable to hypothermia-related complications. The ideal monitoring site has to be chosen considering both the patients characteristics and surgical procedure. Once identified, hypothermia has to be treated and the most effective systems are represented by active forced-air skin warming system. Active prewarming during the preoperative period has been also demonstrated to be efficient in reducing the development of intraoperative hypothermia. Humidification and warming of inspired gases, and warming of intravenous fluids are useful techniques when used in a multimodal approach with active skin warming to maintain perioperative normothermia. Conclusions: All the patient undergoing surgery for more than 30 minutes should receive an accurate temperature monitoring and a correct management for the maintenance of normothermia. Reducing the incidence and severity of perioperative hypothermia has the potential for drastically reducing complication-related costs.

Clinical complications, monitoring and management of perioperative mild hypothermia: anesthesiological features.

The voice of COVID-19: Breath and cough recording classification with temporal decision trees and random forests


 Gas turbine trip is an operational event that arises when undesirable operating conditions are approached or exceeded, and predicting its onset is a largely unexplored area. The application of novel artificial intelligence methods to this problem is interesting both from the computer science and the engineering point of view, and the results may be relevant in both the academia and the industry. In this paper we consider data gathered from a fleet of Siemens industrial gas turbines in operation that include several thermodynamic variables observed during a long period of operation. To assess the possibility of predicting trip events, we first apply a new, systematic statistical analysis to identify the most important variables, then we use a novel machine learning technique known as temporal decision tree, which differ from canonical decision tree because it allows a native treatment of the temporal component, and has an elegant logical interpretation that eases the post-hoc validation of the results. Finally, we use the learned models to extract statistical rules. As a result, we are able to select the 5 most informative variables, build a predictive model with an average accuracy of 73%, and extract several rules. To our knowledge, this is the first attempt to use such an approach not only in the gas turbine field, but also in the whole industry domain.

Statistical Rule Extraction for Gas Turbine Trip Prediction

The study of the electroencephalogram signals recorded from subjects during an experience is a way to understand the brain processes that underlie their physical and emotional involvement. Such signals have the form of time series, and their analysis could benefit from applying techniques that are specific to this kind of data. Neuroaesthetics, as defined by Zeki in 1999, is the scientific approach to the study of aesthetic perceptions of art, music, or any other experience that can give rise to aesthetic judgments, such as liking or disliking a painting. Starting from a proprietary dataset of 248 trials from 16 subjects exposed to art paintings, using a real ecological context, this paper analyses the application of a novel symbolic machine learning technique, specifically designed to extract information from unstructured data and to express it in form of logical rules. Our purpose is to extract qualitative and quantitative logical rules, to relate the voltage at specific frequencies and in specific electrodes, and that, within the limits of the experiment, may help to understand the brain process that drives liking or disliking experiences in human subjects.

https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0287513&type=printable

Towards an objective theory of subjective liking: A first step in understanding the sense of beauty

The most iconic duality of machine learning models is symbolic learning versus functional learning. While functional learning is based on a numerical approach to knowledge extraction and modelling, the purpose of symbolic machine learning is to extract knowledge from data in such a form that it can be understood, discussed, modified, and applied by humans, as well as serve as the basis of artificial intelligence applications. The typical problems associated with machine learning are classification and rule extraction; while classification can be dealt with using both functional and symbolic learning, rule extraction is essentially symbolic. One element common to nearly all definitions and tools for rule extraction is that they are applied to static datasets and based on propositional logic; unfortunately, very often real-world applications give rise to non-static sets of data (e.g., temporal, spatial, graph-based data) and may require more-than-propositional expressive power. In order to extract association rules from non-static data, in this paper we propose a definition of modal association rules based on modal logic, and we study how a standard rule extraction algorithm such as APRIORI can be generalized to the modal case while keeping the properties of the canonical, non-modal case, namely, correctness and completeness.

Giovanni Pagliarini

Papers

Clinical complications, monitoring and management of perioperative mild hypothermia: anesthesiological features.

The voice of COVID-19: Breath and cough recording classification with temporal decision trees and random forests

Statistical Rule Extraction for Gas Turbine Trip Prediction

Towards an objective theory of subjective liking: A first step in understanding the sense of beauty

On Modal Logic Association Rule Mining