26 de dezembro de 2013

Artigo recomendado: Designing and Implementing the Objective Structured Clinical Examination in Anesthesiology

Maya Jalbout Hastie, Jessica L. Spellman, Parwane P. Pagano, Jonathan Hastie, Brian J. Egan

Anesthesiology 2014; 120:196-203

ABSTRACT

Since its description in 1974, the Objective Structured Clinical Examination (OSCE) has gained popularity as an objective assessment tool of medical students, residents, and trainees. With the development of the anesthesiology residents’ milestones and the preparation for the Next Accreditation System, there is an increased interest in OSCE as an evaluation tool of the six core competencies and the corresponding milestones proposed by the Accreditation Council for Graduate Medical Education.

In this article the authors review the history of OSCE and its current application in medical education and in different medical and surgical specialties. They also review the use of OSCE by anesthesiology programs and certification boards in the United States and internationally. In addition, they discuss the psychometrics of test design and implementation with emphasis on reliability and validity measures as they relate to OSCE.

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20 de dezembro de 2013

Artigo recomendado: Cognitive Processes in Anesthesiology Decision Making

Marjorie Podraza Stiegler, Avery Tung

Anesthesiology 2014; 120:204-17

ABSTRACT

The quality and safety of health care are under increasing scrutiny. Recent studies suggest that medical errors, practice variability, and guideline noncompliance are common, and that cognitive error contributes significantly to delayed or incorrect diagnoses. These observations have increased interest in understanding decision-making psychology.

Many nonrational (i.e., not purely based in statistics) cognitive factors influence medical decisions and may lead to error. The most well-studied include heuristics, preferences for certainty, overconfidence, affective (emotional) influences, memory distortions, bias, and social forces such as fairness or blame.

Although the extent to which such cognitive processes play a role in anesthesia practice is unknown, anesthesia care frequently requires rapid, complex decisions that are most susceptible to decision errors. This review will examine current theories of human decision behavior, identify effects of nonrational cognitive processes on decision making, describe characteristic anesthesia decisions in this context, and suggest strategies to improve decision making.

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10 de dezembro de 2013

Artigo recomendado: Perioperative Metoprolol and Risk of Stroke after Noncardiac Surgery

George A. Mashour, Milad Sharifpour, Robert E. Freundlich, Kevin K. Tremper, Amy Shanks, Brahmajee K. Nallamothu, Phillip E. Vlisides, Adam Weightman, Lisa Matlen, Janna Merte, Sachin Kheterpal

Anesthesiology 2013; 119:1340-6

ABSTRACT

Background: Numerous risk factors have been identified for perioperative stroke, but there are conflicting data regarding the role of β adrenergic receptor blockade in general and metoprolol in particular.

Methods: The authors retrospectively screened 57,218 consecutive patients for radiologic evidence of stroke within 30 days after noncardiac procedures at a tertiary care university hospital. Incidence of perioperative stroke within 30 days of surgery and associated risk factors were assessed. Patients taking either metoprolol or atenolol were matched based on a number of risk factors for stroke. Parsimonious logistic regression was used to generate a preoperative risk model for perioperative stroke in the unmatched cohort.

Results: The incidence of perioperative stroke was 55 of 57,218 (0.09%). Preoperative metoprolol was associated with an approximately 4.2-fold increase in perioperative stroke (P < 0.001; 95% CI, 2.2–8.1). Analysis of matched cohorts revealed a significantly higher incidence of stroke in patients taking preoperative metoprolol compared with atenolol (P = 0.016). However, preoperative metoprolol was not an independent predictor of stroke in the entire cohort, which included patients who were not taking β blockers. The use of intraoperative metoprolol was associated with a 3.3-fold increase in perioperative stroke (P = 0.003; 95% CI, 1.4–7.8); no association was found for intraoperative esmolol or labetalol.

Conclusions: Routine use of preoperative metoprolol, but not atenolol, is associated with stroke after noncardiac surgery, even after adjusting for comorbidities. Intraoperative metoprolol but not esmolol or labetalol, is associated with increased risk of perioperative stroke. Drugs other than metoprolol should be considered during the perioperative period if β blockade is required.

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5 de dezembro de 2013

Artigo recomendado: Perioperative Organ Injury

Karsten Bartels, Jörn Karhausen, Eric T. Clambey, Almut Grenz, Holger K. Eltzschig

Anesthesiology 2013; 119:1474-89


ABSTRACT

Despite the fact that a surgical procedure may have been performed for the appropriate indication and in a technically perfect manner, patients are threatened by perioperative organ injury. For example, stroke, myocardial infarction, acute respiratory distress syndrome, acute kidney injury, or acute gut injury are among the most common causes for morbidity and mortality in surgical patients. In the current review, the authors discuss the pathogenesis of perioperative organ injury, and provide select examples for novel treatment concepts that have emerged over the past decade. Indeed, the authors are of the opinion that research to provide mechanistic insight into acute organ injury and identification of novel therapeutic approaches for the prevention or treatment of perioperative organ injury represent the most important opportunity to improve outcomes of anesthesia and surgery.

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26 de novembro de 2013

Artigo recomendado: Lidocaine Patch (5%) in Treatment of Persistent Inguinal Postherniorrhaphy Pain"

A Randomized, Double-blind, Placebo-controlled, Crossover Trial

Joakim M. Bischoff, Marian Petersen, Nurcan Üçeyler, Claudia Sommer, Henrik Kehlet, Mads U. Werner


Background: Evidence-based pharmacological treatment options for patients with persistent inguinal postherniorrhaphy pain are lacking.

Methods: Twenty-one male patients, with severe, unilateral, persistent inguinal postherniorrhaphy pain, participated in a randomized, double-blind, placebo-controlled crossover trial, receiving lidocaine patch (5%) and placebo patch treatments in periods of 14 days separated by a 14-day wash-out period. Pain intensities (at rest, during movement, and pressure evoked [Numerical Rating Scale]) were assessed before treatment and on the last 3 days of each treatment period. Patients were a priori divided into two subgroups based on quantitative sensory testing (+/− thermal “hyposensitivity”). Skin biopsies for intraepidermal nerve fiber density assessment were taken at baseline, and quantitative sensory testing was performed before and after each treatment period. The primary outcome was change in pain intensity assessed as the difference in summed pain intensity differences between lidocaine and placebo patch treatments.

Results: There was no difference in summed pain intensity differences between lidocaine and placebo patch treatments in all patients (mean difference 6.2% [95% CI = −6.6 to 18.9%]; P = 0.33) or in the two subgroups (+/− thermal “hyposensitivity”). The quantitative sensory testing (n = 21) demonstrated an increased pressure pain thresholds after lidocaine compared with placebo patch treatment. Baseline intraepidermal nerve fiber density (n = 21) was lower on the pain side compared with the nonpain side (−3.8 fibers per millimeter [95% CI = −6.1 to −1.4]; P = 0.003). One patient developed mild erythema in the groin during both treatments.

Conclusions: Lidocaine patch treatment did not reduce combined resting and dynamic pain ratings compared with placebo in patients with severe, persistent inguinal postherniorrhaphy pain.

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14 de novembro de 2013

Artigo recomendado: Nocturnal Intermittent Hypoxia Is Independently Associated with Pain in Subjects Suffering from Sleep-disordered Breathing

Anthony G . Doufas, L u Tian, Margaret Frances Davies, Simon C. Warby

Anesthesiology 2013; 119:1149-62

Background: On the basis of experimental and clinical evidence, the authors hypothesized that nocturnal hypoxemia would be associated with pain reports in subjects suffering from sleep-disordered breathing, independently of sleep fragmentation and inflammation.

Methods: After obtaining institutional approval and access to the Cleveland Family Study phenotype and genotype data, the authors used proportional odds regression to examine the association between arterial desaturation and four different types of pain, as well as their composite measure, sequentially adjusted for: (1) clinical characteristics and (2) sleep fragmentation and inflammation. The authors also examined the association of selected candidate single-nucleotide polymorphisms with pain reports.

Results: Decreased minimum nocturnal arterial saturation increased the odds for morning headache (adjusted odds ratio per SD = 1.36; 95% CI [1.08–1.71]; P = 0.009), headache disrupting sleep (1.29 [1.10–1.51]; P = 0.002), and chest pain while in bed (1.37 [1.10–1.70]; P = 0.004). A decrease in the minimum nocturnal saturation from 92 to 75% approximately doubled the odds for pain. One singlenucleotide polymorphism for the a 1 chain of collagen type XI (COL11A1–rs1676486) gene was significantly associated with headache disrupting sleep (odds ratio = 1.72 [1.01–2.94]; P = 0.038), pain disrupting sleep (odds ratio = 1.85 [1.04–3.28]; P = 0.018), and pain composite (odds ratio = 1.89 [1.14–3.14]; P = 0.001).

Conclusion: Nocturnal arterial desaturation may be associated with an increased pain in subjects with sleep-disordered breathing, independently of sleep fragmentation and inflammation.

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12 de novembro de 2013

Artigo recomendado: Epigenetic Regulation of Spinal CXCR2 Signaling in Incisional Hypersensitivity in Mice

Yuan Sun, Peyman Sahbaie, De-Yong Liang, Wen-Wu Li, Xiang-Qi Li, Xiao-You Shi, J. David Clark

Anesthesiology 2013; 119:1198-208

Background: The regulation of gene expression in nociceptive pathways contributes to the induction and maintenance of pain sensitization. Histone acetylation is a key epigenetic mechanism controlling chromatin structure and gene expression. Chemokine CC motif receptor 2 (CXCR2) is a proinflammatory receptor implicated in neuropathic and inflammatory pain and is known to be regulated by histone acetylation in some settings. The authors sought to investigate the role of histone acetylation on spinal CXCR2 signaling after incision.

Methods: Groups of 5–8 mice underwent hind paw incision. Suberoylanilide hydroxamic acid and anacardic acid were used to inhibit histone deacetylase and histone acetyltransferase, respectively. Behavioral measures of thermal and mechanical sensitization as well as hyperalgesic priming were used. Both message RNA quantification and chromatin immunoprecipitation analysis were used to study the regulation of CXCR2 and ligand expression. Finally, the selective CXCR2 antagonist SB225002 was administered intrathecally to reveal the function of spinal CXCR2 receptors after hind paw incision.

Results: Suberoylanilide hydroxamic acid significantly exacerbated mechanical sensitization after incision. Conversely, anacardic acid reduced incisional sensitization and also attenuated incision-induced hyperalgesic priming. Overall, acetylated histone H3 at lysine 9 was increased in spinal cord tissues after incision, and enhanced association of acetylated histone H3 at lysine 9 with the promoter regions of CXCR2 and keratinocyte-derived chemokine (CXCL1) was observed as well. Blocking CXCR2 reversed mechanical hypersensitivity after hind paw incision.

Conclusions: Histone modification is an important epigenetic mechanism regulating incision-induced nociceptive sensitization. The spinal CXCR2 signaling pathway is one epigenetically regulated pathway controlling early and latent sensitization after incision.

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8 de novembro de 2013

Artigo recomendado: Positive End-expiratory Pressure Influences Echocardiographic Measures of Diastolic Function

A Randomized, Crossover Study in Cardiac Surgery Patients

Peter Juhl-Olsen, Johan Fridolf Hermansen, Christian Alcaraz Frederiksen, Linda Aagaard Rasmussen, Carl-Johan Jakobsen, Erik Sloth

Background: Ultrasonography of the cardiovascular system is pivotal for hemodynamic assessment. Diastolic function is evaluated with a combination of tissue Doppler (e’ and a’) and pulsed Doppler (E and A) measures of transmitral- and mitral valve annuli velocities. However, accurate echocardiographic evaluation in the intensive care unit or perioperative setting is contingent on relative resistance to positive pressure ventilation and changes in preload. This study aimed to evaluate the effects of positive end-expiratory pressure (PEEP) and positioning on echocardiographic measures of diastolic function.

Methods: The study was a prospective, randomized, crossover study. Cardiac surgery patients with ejection fraction greater than 45% and averaged e’ of 9 or more were included. Postoperatively, anesthetized patients were randomized into six combinations of PEEP (0, 6, 12 cm H2O) and positions (horizontal, Trendelenburg). At each combination, e’ (primary endpoint), a’, E, and A were obtained with transesophageal echocardiography along with left ventricular area. Image analysis was performed blinded to the protocol.

Results: Thirty patients completed the study. PEEP decreased lateral e’ from 6.6 ± 3.6 to 5.3 ± 3.0 cm/s (P < 0.001) in the horizontal position and from 7.4 ± 4.2 to 6.5 ± 3.3 cm/s (P < 0.001) in Trendelenburg. Similar results were found for septal e’, a’ bilaterally and transmitral pulsed Doppler measures, and PEEP decreased left ventricular area. E/A, E/e’, and e’/a’ remained unaffected by PEEP and positioning.

Conclusions: When evaluating diastolic function by echocardiography, the levels of PEEP and its effect on ventricular area have to be taken into account. In addition, this study dissuades the use of E/e’ for tracking changes in left ventricular filling pressures in cardiac surgery patients.

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5 de novembro de 2013

Artigo recomendado: Perioperative Gabapentinoids

Choice of Agent, Dose, Timing, and Effects on Chronic Postsurgical Pain

Peter C. Schmidt, Gabriela Ruchelli, Sean C. Mackey, Ian R. Carroll

The gabapentinoids pregabalin and gabapentin are both indicated for the treatment of postherpetic neuralgia and as adjuvant therapy for seizure disorders. Pregabalin is additionally approved for the treatment of fibromyalgia and neuropathic pain associated with diabetes mellitus or spinal cord injury. There are now more than 100 clinical trials examining the use of gabapentin perioperatively to reduce postoperative pain and a smaller but growing number of clinical trials examining the efficacy of pregabalin. As a body of work, they support the conclusion that perioperative use of gabapentinoids reduces early postoperative pain and opioid use.1–3 This article describes how this body of work may inform a surgeon’s or anesthesiologist’s optimization of perioperative use of gabapentinoids, including choice of agent, dose, timing, and duration of therapy. In addition, we described the less clear data for and against gabapentinoid efficacy in preventing the emergence of chronic postsurgical pain.

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30 de setembro de 2013

Artigo recomendado: The Anesthesia in Abdominal Aortic Surgery (ABSENT) Study

A Prospective, Randomized, Controlled Trial Comparing Troponin T Release with Fentanyl–Sevoflurane and Propofol–Remifentanil Anesthesia in Major Vascular Surgery

Espen E. Lindholm, Erlend Aune, Camilla B. Norén, Ingebjørg Seljeflot, Thomas Hayes, Jan E. Otterstad, Knut A. Kirkeboen

ABSTRACT
Background: On the basis of data indicating that volatile anesthetics induce cardioprotection in cardiac surgery, current guidelines recommend volatile anesthetics for maintenance of general anesthesia during noncardiac surgery in hemodynamic stable patients at risk for perioperative myocardial ischemia. The aim of the current study was to compare increased troponin T (TnT) values in patients receiving sevoflurane-based anesthesia or total intravenous anesthesia in elective abdominal aortic surgery.

Methods: A prospective, randomized, open, parallel-group trial comparing sevoflurane-based anesthesia (group S) and total intravenous anesthesia (group T) with regard to cardioprotection in 193 patients scheduled for elective abdominal aortic surgery. Increased TnT level on the first postoperative day was the primary endpoint. Secondary endpoints were postoperative complications, nonfatal coronary events and mortality.

Results: On the first postoperative day increased TnT values (>13 ng/l) were found in 43 (44%) patients in group S versus 41 (43%) in group T (P = 0.999), with no significant differences in TnT levels between the groups at any time point. Although underpowered, the authors found no differences in postoperative complications, nonfatal coronary events or mortality between the groups.

Conclusions: In elective abdominal aortic surgery sevoflurane- based anesthesia did not reduce myocardial injury, evaluated by TnT release, compared with total intravenous anesthesia. These data indicate that potential cardioprotective effects of volatile anesthetics found in cardiac surgery are less obvious in major vascular surgery.

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27 de setembro de 2013

Artigo recomendado: Perioperative Auto-titrated Continuous Positive Airway Pressure Treatment in Surgical Patients with Obstructive Sleep Apnea

A Randomized Controlled Trial

Pu L iao, Quanwei L uo, isham E lsaid, Weimin Kang, Colin M. Shapiro, Frances Chung

Anesthesiology 2013; 119:837-47, Liao et al.

ABSTRACT

Background: Obstructive sleep apnea (OSA) may worsen postoperatively. The objective of this randomized open-label trial is to determine whether perioperative auto-titrated continuous positive airway pressure (APAP) treatment decreases postoperative apnea hypopnea index (AHI) and improves oxygenation in patients with moderate and severe OSA.

Methods: The consented patients with AHI of more than 15 events/h on preoperative polysomnography were randomized into the APAP or control group (receiving routine care). The APAP patients received APAP for 2 or 3 preoperative, and 5 postoperative nights. All patients were monitored with oximetry for 7 to 8 nights (N) and underwent polysomnography on postoperative N3. The primary outcome was AHI on the postoperative N3.

Results: One hundred seventy-seven OSA patients undergoing orthopedic and other surgeries were enrolled (APAP: 87 and control: 90). There was no difference between the two groups in baseline data. One hundred six patients (APAP: 40 and control: 66) did polysomnography on postoperative N3, and 100 patients (APAP: 39 and control: 61) completed the study. The compliance rate of APAP was 45%. The APAP usage was 2.4–4.6 h/night. In the APAP group, AHI decreased from preoperative baseline: 30.1 (22.1, 42.5) events/h (median [25th, 75th percentile]) to 3.0 (1.0, 12.5) events/h on postoperative N3 (P < 0.001), whereas, in the control group, AHI increased from 30.4 (23.2, 41.9) events/h to 31.9 (13.5, 50.2) events/h, P = 0.302. No significant change occurred in the central apnea index.

Conclusions: The trial showed the feasibility of perioperative APAP for OSA patients. Perioperative APAP treatment significantly reduced postoperative AHI and improved oxygen saturation in the patients with moderate and severe OSA.

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24 de setembro de 2013

Artigo recomendado: Risk Stratification Tools for Predicting Morbidity and Mortality in Adult Patients Undergoing Major Surgery

Qualitative Systematic Review

Suneetha Ramani Moonesinghe, Michael G. Mythen, Priya Das, Kathryn M. Rowan, Michael P. W. Grocott

Anesthesiology 2013; 119:959-81, Moonesinghe et al.

ABSTRACT
Risk stratification is essential for both clinical risk prediction and comparative audit. There are a variety of risk stratification tools available for use in major noncardiac surgery, but their discrimination and calibration have not previously been systematically reviewed in heterogeneous patient cohorts.

Embase, MEDLINE, and Web of Science were searched for studies published between January 1, 1980 and August 6, 2011 in adult patients undergoing major noncardiac, nonneurological surgery. Twenty-seven studies evaluating 34 risk stratification tools were identified which met inclusion criteria. The Portsmouth-Physiology and Operative Severity Score for the enUmeration of Mortality and the Surgical Risk Scale were demonstrated to be the most consistently accurate tools that have been validated in multiple studies; however, both have limitations. Future work should focus on further evaluation of these and other parsimonious risk predictors, including validation in international cohorts. There is also a need for studies examining the impact that the use of these tools has on clinical decision making and patient outcome.

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20 de setembro de 2013

Artigo recomendado: Relationship between Intraoperative Mean Arterial Pressure and Clinical Outcomes after Noncardiac Surgery

Toward an Empirical Definition of Hypotension

Michael Walsh, Philip J. Devereaux, Amit X. G arg, Andrea Kurz, Alparslan Turan, Reitze N. Rodseth, Jacek Cywinski, Lehana Thabane, Daniel I . S essler

Anesthesiology 2013; 119:507-15

ABSTRACT
Background: Intraoperative hypotension may contribute to postoperative acute kidney injury (AKI) and myocardial injury, but what blood pressures are unsafe is unclear. The authors evaluated the association between the intraoperativemean arterial pressure (MAP) and the risk of AKI and myocardial injury.

Methods: The authors obtained perioperative data for 33,330 noncardiac surgeries at the Cleveland Clinic, Ohio. The authors evaluated the association between intraoperative MAP from less than 55 to 75 mmHg and postoperative AKI and myocardial injury to determine the threshold of MAP where risk is increased. The authors then evaluated the association between the duration below this threshold and their outcomes adjusting for potential confounding variables.

Results: AKI and myocardial injury developed in 2,478 (7.4%) and 770 (2.3%) surgeries, respectively. The MAP threshold where the risk for both outcomes increased was less than 55 mmHg. Compared with never developing a MAP less than 55 mmHg, those with a MAP less than 55 mmHg for 1–5, 6–10, 11–20, and more than 20 min had graded increases in their risk of the two outcomes (AKI: 1.18 [95% CI, 1.06–1.31], 1.19 [1.03–1.39], 1.32 [1.11–1.56], and 1.51 [1.24–1.84], respectively; myocardial injury 1.30 [1.06–1.5], 1.47 [1.13–1.93], 1.79 [1.33–2.39], and 1.82 [1.31–2.55], respectively].

Conclusions: Even short durations of an intraoperative MAP less than 55 mmHg are associated with AKI and myocardial injury. Randomized trials are required to determine whether outcomes improve with interventions that maintain an intraoperative MAP of at least 55 mmHg.

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17 de setembro de 2013

Artigo recomendado: Oxytocin Pretreatment Attenuates Oxytocin-induced Contractions in Human Myometrium In Vitro

Mrinalini Balki, Magda Erik-Soussi, John Kingdom, Jose C. A. Carvalho

Anesthesiology 2013; 119:552-61; Balki et al.

ABSTRACT

Background: Oxytocin receptor desensitization has been shown to occur in humans at biomolecular level and in isolated rat myometrium; however, its effect on human myometrial contractility has not been demonstrated. The objective of this in vitro study was to investigate the contractile response of human pregnant myometrium to oxytocin after pretreatment with different concentrations of oxytocin for variable durations.

Methods: Myometrial samples were obtained from 62 women undergoing elective cesarean deliveries under regional anesthesia.The strips were pretreated with oxytocin 10−10, 10−8, 10−5 M, or physiological salt solution (control) for 2, 4, 6, or 12 h, followed by a dose–response testing with oxytocin 10−10 to 10−5 MAmplitude and frequency of contractions, motility index, and area under the curve during the dose–response period were recorded, analyzed with linear regression models, and compared among groups.

Results: Pretreatment with oxytocin , 10−5 and 10−8 M significantly reduced motility index (estimate [standard error]: −0.771 [0.270] square root units, P = 0.005 and −0.697 [0.293], P = 0.02, respectively) and area under the curve (−3.947 [1.909], P = 0.04 and −4.241 [2.189], P = 0.05, respectively) compared with control group, whereas pretreatment with oxytocin 10−10 M did not significantly attenuate contractions. Increase in duration of oxytocin pretreatment from 2 to 12 h significantly decreased amplitude (type 3 generalized estimating equation analysis: chi-square = 14.0; df = 3; P = 0.003), motility index (chi-square = 9.3; df = 3; P = 0.03), and area under the curve (chi-square = 10.5; df = 3; P = 0.02), but not the frequency of oxytocin-induced contractions.

Conclusion: Pretreatment with oxytocin decreases oxytocin-induced myometrial contractions in a concentration and time-dependent manner, likely as a function of the oxytocin receptor desensitization phenomenon.

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10 de setembro de 2013

Artigo recomendado: Prospective Randomized Crossover Study of a New Closed-loop Control System versus Pressure Support during Weaning from Mechanical Ventilation

Noémie Clavieras, Marc Wysocki, Yannael Coisel, Fabrice Galia, Matthieu Conseil, Gerald Chanques, Boris Jung, Jean-Michel Arnal, Stefan Matecki, Nicolas Molinari, Samir Jaber

Anesthesiology 2013; 119:631-41; Clavieras et al.

ABSTRACT
Background: Intellivent is a new full closed-loop controlled ventilation that automatically adjusts both ventilation and oxygenation parameters. The authors compared gas exchange and breathing pattern variability of Intellivent and pressure support ventilation (PSV).
Methods: In a prospective, randomized, single-blind design crossover study, 14 patients were ventilated during the weaning phase, with Intellivent or PSV, for two periods of 24 h in a randomized order. Arterial blood gases were obtained after 1, 8, 16, and 24 h with each mode. Ventilatory parameters were recorded continuously in a breath-by-breath basis during the two study periods. The primary endpoint was oxygenation, estimated by the calculation of the difference between the Pao2/Fioratio obtained after 24 h of ventilation and the Pao2/Fioratio obtained at baseline in each mode. The variability in the ventilatory parameters was also evaluated by the coefficient of variation (SD to mean ratio).
Results: There were no adverse events or safety issues requiring premature interruption of both modes. The Pao2/Fio2 (mean ± SD) ratio improved significantly from 245 ± 75 at baseline to 294 ± 123 (P = 0.03) after 24 h of Intellivent. The coefficient of variation of inspiratory pressure and positive end-expiratory pressure (median [interquartile range]) were significantly higher with Intellivent, 16 [11–21] and 15 [7–23]%, compared with 6 [5–7] and 7 [5–10]% in PSV. Inspiratory pressure, positive end-expiratory pressure, and Fio2 changes were adjusted significantly more often with Intellivent compared with PSV.
Conclusions: Compared with PSV, Intellivent during a 24-h period improved the Pao2/Fio2 ratio in parallel with more variability in the ventilatory support and more changes in ventilation settings.

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6 de setembro de 2013

Artigo recomendado: Different Propofol–Remifentanil or Sevoflurane–Remifentanil Bispectral Index Levels for Electrocorticographic Spike Identification during Epilepsy Surgery

Ashraf A. Dahaba, Jian Yin, Zhaoyang Xiao, Jing Su, Helmar Bornemann, Hailong Dong, Lize Xiong

Anesthesiology 2013; 119:582-92; Dahaba et al.

ABSTRACT

Background: Medical therapy, the cornerstone of managing epilepsy, still fails a substantial portion of patients. Little information is available regarding the potential impact of different bispectral index (BIS) levels on electrocorticographic spike identification for surgical epileptic foci resection.

Methods: Twenty-two intractable epilepsy subjects were randomly allocated to the propofol–remifentanil or sevoflurane–remifentanil groups, and were further randomized to four BIS85 (BIS 71–85), BIS70 (BIS 56–70), BIS55 (BIS 41–55), and BIS40 (BIS ≤40) sequence order.

Results: Two-way ANOVA revealed no differences between groups in spike frequency (P = 0.720), spike amplitude (P = 0.647), or number of spiking leads (P = 0.653). In the propofol and sevoflurane groups, decreasing BIS levels increased mean ± SD spike/min frequency (P < 0.001 and P < 0.001) at BIS85 (10 ± 12 and 10 ± 8), BIS70 (19 ± 17 and 17 ± 15), BIS55 (22 ± 17 and 18 ± 8), and BIS40 (25 ± 15 and 23 ± 17). Furthermore, in the propofol and sevoflurane groups, decreasing BIS levels increased spike microvolt amplitude (P = 0.006 and P = 0.009) at BIS85 (1,100 ± 400 and 750 ± 400), BIS70 (1,200 ± 460 and 850 ± 490), BIS55 (1,300 ± 560 and 940 ± 700), and BIS40 (1,400 ± 570 and 1,300 ± 700). Whereas, in the propofol and sevoflurane groups, there was no difference in the location or number of spiking leads (P = 0.057 and P = 0.109) at the four BIS levels. Compared with BIS85, spike frequency in the propofol and sevoflurane groups increased 100 and 170% at BIS70, 116 and 180% at BIS55, and 132 and 230% at BIS40. Compared with BIS85, spike amplitude increased 108 and 113% at BIS70, 121 and 125% at BIS55, and 128 and 170% at BIS40.

Conclusion: Decreasing BIS levels in the propofol and sevoflurane groups enhanced epileptogenic spike frequency and amplitude with the same location and number of spiking leads.

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3 de setembro de 2013

Artigo recomendado: Neuraxial Anesthesia in Parturients with Intracranial Pathology

A Comprehensive Review and Reassessment of Risk


Lisa R. Leffert, Lee H. Schwamm
Anesthesiology 2013; 119:703-18; L. R. Leffert and L. H. Schwamm

ABSTRACT

Parturients with intracranial lesions are often assumed to have increased intracranial pressure, even in the absence of clinical and radiographic signs. The risk of herniation after an inadvertent dural puncture is frequently cited as a contraindication to neuraxial anesthesia. This article reviews the relevant literature on the use of neuraxial anesthesia in parturients with known intracranial pathology, and proposes a framework and recommendations for assessing risk of neurologic deterioration, with epidural analgesia or anesthesia, or planned or inadvertent dural puncture. The authors illustrate these concepts with numerous case examples and provide guidance for the practicing anesthesiologist in determining the safety of neuraxial anesthesia.

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27 de agosto de 2013

Artigo recomendado: Effect of Intraoperative High Inspired Oxygen Fraction on Surgical Site Infection, Postoperative Nausea and Vomiting, and Pulmonary Function

Systematic Review and Meta-analysis of Randomized Controlled Trials

Frédérique Hovaguimian, Christopher Lysakowski, Nadia Elia, Martin R. Tramèr

Anesthesiology 2013; 119:303-16; Hovaguimian et al.


Background: Intraoperative high inspired oxygen fraction (Fio2) is thought to reduce the incidence of surgical site infection (SSI) and postoperative nausea and vomiting, and to promote postoperative atelectasis.

Methods: The authors searched for randomized trials (till September 2012) comparing intraoperative high with normal Fio2 in adults undergoing surgery with general anesthesia and reporting on SSI, nausea or vomiting, or pulmonary outcomes.

Results: The authors included 22 trials (7,001 patients) published in 26 reports. High Fio2 ranged from 80 to 100% (median, 80%); normal Fio2 ranged from 30 to 40% (median, 30%). In nine trials (5,103 patients, most received prophylactic antibiotics), the incidence of SSI decreased from 14.1% with normal Fio2 to 11.4% with high Fio2; risk ratio, 0.77 (95% CI, 0.59–1.00). After colorectal surgery, the incidence of SSI decreased from 19.3 to 15.2%; risk ratio, 0.78 (95% CI, 0.60–1.02). In 11 trials (2,293 patients), the incidence of nausea decreased from 24.8% with normal Fio2 to 19.5% with high Fio2; risk ratio, 0.79 (95% CI, 0.66–0.93). In patients receiving inhalational anesthetics without prophylactic antiemetics, high Fio2 provided a significant protective effect against both nausea and vomiting. Nine trials (3,698 patients) reported on pulmonary outcomes. The risk of atelectasis was not increased with high Fio2.

Conclusions: Intraoperative high Fio2 further decreases the risk of SSI in surgical patients receiving prophylactic antibiotics, has a weak beneficial effect on nausea, and does not increase the risk of postoperative atelectasis.

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23 de agosto de 2013

Artigo recomendado: Phrenic Nerve Function after Interscalene Block Revisited

Now, the Long View
Quinn H. Hogan
Anesthesiology 2013; 119:250-2, Quinn H. Hogan

Anesthesiologists are very good at immediate observation and intervention. For instance, hemodynamic disorders or inadequate ventilation are apparent to us in real time with customary vigilance and modern monitoring. Less evident are the delayed consequences of our actions. Only relatively recently we have become suspicious that volatile anesthetics might alter immunological function or neurological development months after administration. Similarly, in the realm of plexus and peripheral nerve blocks, we have long understood the immediate risks of injecting local anesthetic into the systemic circulation, which included vessel damage leading to bleeding, neural trauma, and anesthetization of unintended targets. Our focus of care is to avoid these immediate dangers. In contrast, delayed harm after blocks is less subject to our scrutiny. A case series reported in the current issue of Anesthesiology suggests that our attention should also extend into the long-term time frame regarding phrenic nerve function after interscalene blockade (ISB).

Acute loss of diaphragmatic activity after block of the phrenic nerve during ISB has been recognized as a predictable hazard since the landmark study by Urmey et al. in 1991. Now, Kaufman et al. report a series of 14 patients referred to them for treatment of chronic diaphragmatic paralysis that was clearly due to phrenic nerve damage after ISB. Few conclusions can be made from a case series with certainty, but their observations support several preliminary hypotheses.

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20 de agosto de 2013

Artigo recomendado: General Anesthesia with Sevoflurane Decreases Myocardial Blood Volume and Hyperemic Blood Flow in Healthy Humans

Carolien S. E. Bulte, Jeroen Slikkerveer, Otto Kamp, Martijn W. Heymans, Stephan A. Loer, Stefano F. de Marchi, Rolf Vogel, Christa Boer, R. Arthur Bouwman

Anesth Analg 2013;116:767–74

Background: Preservation of myocardial perfusion during general anesthesia is likely important in patients at risk for perioperative cardiac complications. Data related to the influence of general anesthesia on the normal myocardial circulation are limited. In this study, we investigated myocardial microcirculatory responses to pharmacological vasodilation and sympathetic stimulation during general anesthesia with sevoflurane in healthy humans immediately before surgical stimulation.

Methods: Six female and 7 male subjects (mean age 43 years, range 28–61) were studied at baseline while awake and during the administration of 1 minimum alveolar concentration sevoflurane. Using myocardial contrast echocardiography, myocardial blood flow (MBF) and microcirculatory  variables were assessed at rest, during adenosine-induced hyperemia, and after cold pressor test–induced sympathetic stimulation. MBF was calculated from the relative myocardial blood volume multiplied by its exchange frequency (ß) divided by myocardial tissue density (ρT), which was set at 1.05 g·mL-1.

Results: During sevoflurane anesthesia, MBF at rest was similar to baseline values (1.05 ± 0.28 vs 1.05 ± 0.32 mL·min-1·g-1; P = 0.98; 95% confidence interval [CI], -0.18 to 0.18). Myocardial blood volume decreased (P = 0.0044; 95% CI, 0.01–0.04) while its exchange frequency (ß) increased under sevoflurane anesthesia when compared with baseline. In contrast, hyperemic MBF was reduced during anesthesia compared with baseline (2.25 ± 0.5 vs 3.53 ± 0.7 mL·min-1·g-1; P = 0.0003; 95% CI, 0.72–1.84). Sympathetic stimulation during sevoflurane anesthesia resulted in a similar MBF compared to baseline (1.53 ± 0.53 and 1.55 ± 0.49 mL·min-1·g-1; P = 0.74; 95% CI, -0.47 to 0.35).

Conclusion: In otherwise healthy subjects who are not subjected to surgical stimulation, MBF at rest and after sympathetic stimulation is preserved during sevoflurane anesthesia despite a decrease in myocardial blood volume. However, sevoflurane anesthesia reduces hyperemic MBF, and thus MBF reserve, in these subjects.

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16 de agosto de 2013

Artigo recomendado: Conventional and Kilohertz-frequency Spinal Cord Stimulation Produces Intensity- and Frequency-dependent Inhibition of Mechanical Hypersensitivity in a Rat Model of Neuropathic Pain

Ronen Shechter, Fei Yang, Qian Xu, Yong-Kwan Cheong, Shao-Qiu He, Andrei Sdrulla, Alene F. Carteret, Paul W. Wacnik, Xinzhong Dong, Richard A. Meyer, Srinivasa N. Raja, Yun Guan

Anesthesiology 2013; 119:422-32, Shechter et al.

Background: Spinal cord stimulation (SCS) is a useful neuromodulatory technique for treatment of certain neuropathic pain conditions. However, the optimal stimulation parameters remain unclear.

Methods: In rats after L5 spinal nerve ligation, the authors compared the inhibitory effects on mechanical hypersensitivity from bipolar SCS of different intensities (20, 40, and 80% motor threshold) and frequencies (50, 1 kHz, and 10 kHz). The authors then compared the effects of 1 and 50 Hz dorsal column stimulation at high- and low-stimulus intensities on conduction properties of afferent Aα/β-fibers and spinal wide-dynamic–range neuronal excitability.

Results: Three consecutive daily SCS at different frequencies progressively inhibited mechanical hypersensitivity in an intensity-dependent manner. At 80% motor threshold, the ipsilateral paw withdrawal threshold (% preinjury) increased significantly from pre-SCS measures, beginning with the first day of SCS at the frequencies of 1 kHz (50.2 ± 5.7% from 23.9 ± 2.6%, n = 19, mean ± SEM) and 10 kHz (50.8 ± 4.4% from 27.9 ± 2.3%, n = 17), whereas it was significantly increased beginning on the second day in the 50 Hz group (38.9 ± 4.6% from 23.8 ± 2.1%, n = 17). At high intensity, both 1 and 50 Hz dorsal column stimulation reduced Aα/β-compound action potential size recorded at the sciatic nerve, but only 1 kHz stimulation was partially effective at the lower intensity. The number of actions potentials in C-fiber component of wide-dynamic–range neuronal response to windup-inducing stimulation was significantly decreased after 50 Hz (147.4 ± 23.6 from 228.1 ± 39.0, n = 13), but not 1 kHz (n = 15), dorsal column stimulation.

Conclusions: Kilohertz SCS attenuated mechanical hypersensitivity in a time course and amplitude that differed from conventional 50 Hz SCS, and may involve different peripheral and spinal segmental mechanisms.

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12 de agosto de 2013

Artigo recomendado: Acute Normovolemic Hemodilution in the Pig Is Associated with Renal Tissue Edema, Impaired Renal Microvascular Oxygenation, and Functional Loss

Franziska M. Konrad, Egbert G. Mik, Sander I. A. Bodmer, Bahar Ates, Henriëtte F. E. M. Willems, Karin Klingel, Hilde R. H. de Geus, Robert Jan Stolker, Tanja Johannes

Anesthesiology 2013; 119:256-69, Konrad et al.

Background: The authors investigated the impact of acute normovolemic hemodilution (ANH) on intrarenal oxygenation and its functional short-term consequences in pigs.

Methods: Renal microvascular oxygenation (μPo2) was measured in cortex, outer and inner medulla via three implanted optical fibers by oxygen-dependent quenching of phosphorescence. Besides systemic hemodynamics, renal function, histopathology, and hypoxia-inducible factor-1α expression were determined. ANH was performed in n = 18 pigs with either colloids (hydroxyethyl starch 6% 130/0.4) or crystalloids (full electrolyte solution), in three steps from a hematocrit of 30% at baseline to a hematocrit of 15% (H3).

Results: ANH with crystalloids decreased μPo2 in cortex and outer medulla approximately by 65% (P < 0.05) and in inner medulla by 30% (P < 0.05) from baseline to H3. In contrast, μPo2 remained unaltered during ANH with colloids. Furthermore, renal function decreased by approximately 45% from baseline to H3 (P < 0.05) only in the crystalloid group. Three times more volume of crystalloids was administered compared with the colloid group. Alterations in systemic and renal regional hemodynamics, oxygen delivery and oxygen consumption during ANH, gave no obvious explanation for the deterioration of μPo2 in the crystalloid group. However, ANH with crystalloids was associated with the highest formation of renal tissue edema and the highest expression of hypoxia-inducible factor-1α, which was mainly localized in distal convoluted tubules.

Conclusions: ANH to a hematocrit of 15% statistically significantly impaired μPo2 and renal function in the crystalloid group. Less tissue edema formation and an unimpaired renal μPo2 in the colloid group might account for a preserved renal function.

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9 de agosto de 2013

Case Scenario: Hypotonia in Infancy - Anesthetic Dilemma

Angela K. Saettele, Anshuman Sharma, David J. Murray

Anesthesiology 2013; 119:443-6, Saettele et al.


Infants with hypotonia of unknown etiology pose a unique challenge as many of the potential diagnoses have major, often conflicting, anesthetic management implications. The differential diagnosis of hypotonia is long and includes possibilities such as Duchenne muscular dystrophy, central core disease, and multiminicore disease. Intravenous anesthetic techniques are recommended because hyperkalemia or malignant hyperthermia is associated with the use of volatile anesthetics. However, the differential diagnosis of infants with hypotonia also includes mitochondrial disorders.

In children with mitochondrial disorders, an intravenous anesthetic technique that includes propofol could lead to metabolic decompensation because propofol alters mitochondrial electron transfer. This dilemma is often encountered when hypotonic infants require anesthesia for diagnostic tests such as magnetic resonance imaging and muscle biopsies for definitive diagnosis.

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5 de agosto de 2013

Artigo recomendado: Integration of Pain Score and Morphine Consumption in Analgesic Clinical Studies

Feng Dai, David G. Silverman,y Jacques E. Chelly, Jia Li, Inna Belfer and Li Qin

Dai et al, The Journal of Pain. 2013 by the American Pain Society

ABSTRACT

In pain clinical trials, the rescue analgesic medication such as patient-controlled analgesia morphine is often made available for patients for breakthrough pain. The patient-controlled analgesia morphine usage decreases the study agent’s effect on pain relative to placebo and introduces greater variability in attainment of pain scores. For assessment of analgesic efficacy, the isolated statistical analysis of pain score or morphine consumption as a surrogate marker for pain not only loses statistical efficiency but also may incur increased false-positive findings because of multiple testing. The aim of this article is to review the research to date for choices of statistical tests for pain or morphine consumption outcome, with a focus on systematically evaluating a means for collective analgesic assessment of pain and morphine consumption using an integrated outcome. A case example is illustrated for data visualization, statistical comparison, and effect size estimation using the new endpoint. Some implications for clinical practice and further research are discussed.
Perspective: This article provides statistical evidence to conclude that an integrated outcome of pain score and morphine consumption provides an efficient means for integrated analgesic assessment.

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2 de agosto de 2013

Artigo recomendado: Surgical Treatment of Permanent Diaphragm Paralysis after Interscalene Nerve Block for Shoulder Surgery

Matthew R. Kaufman, Andrew I. Elkwood, Michael I. Rose, Tushar Patel, Russell Ashinoff, Ryan Fields, David Brown

Anesthesiology 2013; 119:484-7, Kaufman et al.

Unilateral diaphragm paralysis after interscalene nerve block can result in respiratory disturbances that may have a substantial impact on quality of life and increased prevalence of respiratory infections. Several reports have estimated the incidence of transient diaphragm paralysis after routine interscalene blocks for shoulder surgery to be 100%, however, with modified local anesthetic dosing and ultrasound-guided needle placement, more recent data suggest this rate to be lower. Of greater concern is permanent diaphragm paralysis after interscalene nerve block for shoulder surgery. There are isolated reports in the literature regarding long-standing postprocedural diaphragm paralysis, yet the underlying causative mechanism has not been previously sought. Peripheral nerve injury may occur from a variety of mechanical causes, including: transection, piercing, stretching, thermal injury, and compression. Alternatively, a nonmechanical injury can result from the toxic or ischemic effects of pharmacologic agents, such as local anesthetics, epinephrine, or chemotherapeutic agents.

Phrenic nerve injury from many of these causes may be repaired using nerve-reconstruction techniques. We report our experience with 14 patients suffering permanent diaphragm paralysis after interscalene nerve blocks evaluated and treated between 2009 and 2012 at a tertiary referral center for peripheral nerve injuries with a catchment area that includes the entire United States. Parameters for review included: results of comprehensive evaluation, intraoperative findings during phrenic nerve surgery, and outcomes of surgical intervention (using our previously reported surgical treatment algorithm and outcomes study). Successful treatment of the paralyzed diaphragm was based on improvements on: sniff testing, spirometry, nerve conduction testing, electromyography, and patient reporting.

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