Pulmonary atelectasis: a pathogenic perioperative entity.
TL;DR: The authors discuss the effects and implications of atelectasis in the perioperative period and illustrate how preventive measures may impact outcome and the impact of atElectasis and its prevention in acute lung injury.
Abstract: Atelectasis occurs in the dependent parts of the lungs of most patients who are anesthetized. Development of atelectasis is associated with decreased lung compliance, impairment of oxygenation, increased pulmonary vascular resistance, and development of lung injury. The adverse effects of atelectasis persist into the postoperative period and can impact patient recovery. This review article focuses on the causes, nature, and diagnosis of atelectasis. The authors discuss the effects and implications of atelectasis in the perioperative period and illustrate how preventive measures may impact outcome. In addition, they examine the impact of atelectasis and its prevention in acute lung injury.
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TL;DR: The use of a lung-protective ventilation strategy in intermediate-risk and high-risk patients undergoing major abdominal surgery was associated with improved clinical outcomes and reduced health care utilization.
Abstract: The two intervention groups had similar characteristics at baseline. In the intention-to-treat analysis, the primary outcome occurred in 21 of 200 patients (10.5%) assigned to lung-protective ventilation, as compared with 55 of 200 (27.5%) assigned to nonprotective ventilation (relative risk, 0.40; 95% confidence interval [CI], 0.24 to 0.68; P = 0.001). Over the 7-day postoperative period, 10 patients (5.0%) assigned to lung-protective ventilation required noninvasive ventilation or intubation for acute respiratory failure, as compared with 34 (17.0%) assigned to nonprotective ventilation (relative risk, 0.29; 95% CI, 0.14 to 0.61; P = 0.001). The length of the hospital stay was shorter among patients receiving lung-protective ventilation than among those receiving nonprotective ventilation (mean difference, −2.45 days; 95% CI, −4.17 to −0.72; P = 0.006). CONCLUSIONS As compared with a practice of nonprotective mechanical ventilation, the use of a lung-protective ventilation strategy in intermediate-risk and high-risk patients undergoing major abdominal surgery was associated with improved clinical out comes and reduced health care utilization. (IMPROVE ClinicalTrials.gov number, NCT01282996.)
1,086 citations
TL;DR: The risk index based on seven objective, easily assessed factors has excellent discriminative ability and can be used to assess individual risk of PPC and focus further research on measures to improve patient care.
Abstract: Background: Current knowledge of the risk for postoperative pulmonary complications (PPCs) rests on studies that narrowly selected patients and procedures. Hypothesizing thatPPCoccurrencecouldbepredictedfromareducedsetof perioperative variables, we aimed to develop a predictive index for a broad surgical population. Methods: Patients undergoing surgical procedures given general, neuraxial, or regional anesthesia in 59 hospitals were randomly selected for this prospective, multicenter study. The main outcome was the development of at least one of the following:respiratoryinfection,respiratoryfailure,bronchospasm, atelectasis, pleural effusion, pneumothorax, or aspiration pneumonitis. The cohort was randomly divided into a development subsample to construct a logistic regression model and a validation subsample. A PPC predictive index was constructed. Results: Of 2,464 patients studied, 252 events were observed in 123 (5%). Thirty-day mortality was higher in patients with a PPC (19.5%; 95% [CI], 12.5–26.5%) than in those without a PPC (0.5%; 95% CI, 0.2–0.8%). Regression modeling identified seven independent risk factors: low preoperative arterial oxygen saturation, acute respiratory infectionduringthepreviousmonth,age,preoperativeanemia, upper abdominal or intrathoracic surgery, surgical duration of at least 2 h, and emergency surgery. The area under the receiver operating characteristic curve was 90% (95% CI, 85–94%) for the development subsample and 88% (95% CI, 84–93%) for the validation subsample. Conclusion: The risk index based on seven objective, easily assessed factors has excellent discriminative ability. The index can be used to assess individual risk of PPC and focus further research on measures to improve patient care.
905 citations
TL;DR: A strategy with a high level of positive end-expiratory pressure and recruitment manoeuvres during open abdominal surgery does not protect against postoperative pulmonary complications, and an intraoperative protective ventilation strategy should include a low tidal volume and low positiveEnd-expiration pressure, without recruitment manoeuvre.
516 citations
TL;DR: Practice Guidelines provide basic recommendations that are supported by a synthesis and analysis of the current literature, expert and practitioner opinion, open forum commentary, and clinical feasibility data that assist the practitioner and patient in making decisions about health care.
Abstract: P RACTICE Guidelines are systematically developed recommendations that assist the practitioner and patient in making decisions about health care. These recommendations may be adopted, modified, or rejected according to clinical needs and constraints, and are not intended to replace local institutional policies. In addition, Practice Guidelines developed by the American Society of Anesthesiologists (ASA) are not intended as standards or absolute requirements, and their use cannot guarantee any specific outcome. Practice Guidelines are subject to revision as warranted by the evolution of medical knowledge, technology, and practice. They provide basic recommendations that are supported by a synthesis and analysis of the current literature, expert and practitioner opinion, open forum commentary, and clinical feasibility data.
465 citations
TL;DR: The Difficult Airway Society has developed guidelines for the safe management of tracheal extubation in adult peri‐operative practice, and they emphasise the importance of planning and preparation and include practical techniques for use in clinical practice and recommendations for post‐extubation care.
Abstract: Tracheal extubation is a high‐risk phase of anaesthesia. The majority of problems that occur during extubation and emergence are of a minor nature, but a small and significant number may result in injury or death. The need for a strategy incorporating extubation is mentioned in several international airway management guidelines, but the subject is not discussed in detail, and the emphasis has been on extubation of the patient with a difficult airway. The Difficult Airway Society has developed guidelines for the safe management of tracheal extubation in adult peri‐operative practice. The guidelines discuss the problems arising during extubation and recovery and promote a strategic, stepwise approach to extubation. They emphasise the importance of planning and preparation, and include practical techniques for use in clinical practice and recommendations for post‐extubation care.
390 citations
References
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TL;DR: In patients with acute lung injury and the acute respiratory distress syndrome, mechanical ventilation with a lower tidal volume than is traditionally used results in decreased mortality and increases the number of days without ventilator use.
Abstract: Background Traditional approaches to mechanical ventilation use tidal volumes of 10 to 15 ml per kilogram of body weight and may cause stretch-induced lung injury in patients with acute lung injury and the acute respiratory distress syndrome. We therefore conducted a trial to determine whether ventilation with lower tidal volumes would improve the clinical outcomes in these patients. Methods Patients with acute lung injury and the acute respiratory distress syndrome were enrolled in a multicenter, randomized trial. The trial compared traditional ventilation treatment, which involved an initial tidal volume of 12 ml per kilogram of predicted body weight and an airway pressure measured after a 0.5-second pause at the end of inspiration (plateau pressure) of 50 cm of water or less, with ventilation with a lower tidal volume, which involved an initial tidal volume of 6 ml per kilogram of predicted body weight and a plateau pressure of 30 cm of water or less. The primary outcomes were death before a patient was discharged home and was breathing without assistance and the number of days without ventilator use from day 1 to day 28. Results The trial was stopped after the enrollment of 861 patients because mortality was lower in the group treated with lower tidal volumes than in the group treated with traditional tidal volumes (31.0 percent vs. 39.8 percent, P=0.007), and the number of days without ventilator use during the first 28 days after randomization was greater in this group (mean [+/-SD], 12+/-11 vs. 10+/-11; P=0.007). The mean tidal volumes on days 1 to 3 were 6.2+/-0.8 and 11.8+/-0.8 ml per kilogram of predicted body weight (P Conclusions In patients with acute lung injury and the acute respiratory distress syndrome, mechanical ventilation with a lower tidal volume than is traditionally used results in decreased mortality and increases the number of days without ventilator use.
11,028 citations
TL;DR: An overview of the definitions, clinical features, and epidemiology of the acute respiratory distress syndrome is provided and advances in the areas of pathogenesis, resolution, and treatment are discussed.
Abstract: The acute respiratory distress syndrome is a common, devastating clinical syndrome of acute lung injury that affects both medical and surgical patients. Since the last review of this syndrome appeared in the Journal, 1 more uniform definitions have been devised and important advances have occurred in the understanding of the epidemiology, natural history, and pathogenesis of the disease, leading to the design and testing of new treatment strategies. This article provides an overview of the definitions, clinical features, and epidemiology of the acute respiratory distress syndrome and discusses advances in the areas of pathogenesis, resolution, and treatment. Historical Perspective and Definitions . . .
5,002 citations
TL;DR: As compared with conventional ventilation, the protective strategy was associated with improved survival at 28 days, a higher rate of weaning from mechanical ventilation, and a lower rate of barotrauma in patients with the acute respiratory distress syndrome.
Abstract: Background In patients with the acute respiratory distress syndrome, massive alveolar collapse and cyclic lung reopening and overdistention during mechanical ventilation may perpetuate alveolar injury. We determined whether a ventilatory strategy designed to minimize such lung injuries could reduce not only pulmonary complications but also mortality at 28 days in patients with the acute respiratory distress syndrome. Methods We randomly assigned 53 patients with early acute respiratory distress syndrome (including 28 described previously), all of whom were receiving identical hemodynamic and general support, to conventional or protective mechanical ventilation. Conventional ventilation was based on the strategy of maintaining the lowest positive end-expiratory pressure (PEEP) for acceptable oxygenation, with a tidal volume of 12 ml per kilogram of body weight and normal arterial carbon dioxide levels (35 to 38 mm Hg). Protective ventilation involved end-expiratory pressures above the lower inflection poin...
3,323 citations
"Pulmonary atelectasis: a pathogenic..." refers methods in this paper
...Current literature indicates that intraoperative and postoperative lung recruitment improves intermediate physiologic outcomes (e.g., oxygenation, work of breathing); however, the benefits might have more significant implications for lung injury and ARDS....
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...In fact, distribution of ventilation is more uniform in anesthetized patients in the prone position, in particular where the abdomen is not supported.62 Prone positioning improves oxygenation in patients with ARDS.63 Animal models have also demonstrated the benefit of prone positioning after oleic acid–induced lung injury as well as a model of lung injury induced solely by mechanical forces.64,65 Prone positioning causes less extensive histologic injury and alters its distribution.64,65 Atelectasis is more prominent after cardiac surgery with cardiopulmonary bypass (CPB) than after other forms of surgery....
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...The ARDSnet study recommends the use of low tidal volume in patients with ARDS.95 Lower tidal volume reduces stretch-induced lung injury in patients with ARDS,96 and this approach is translated into improved patient survival.95,97 However, extrapolation of the low-tidal-volume approach to patients without lung injury (or ARDS) requires caution for two principal reasons....
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...Recruiting maneuvers were frequently used and consisted of continuous positive airway pressures of 35–40 cm H2O for 40 s followed by a return to previous PEEP levels.(159) Gattinoni et al....
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...The authors found that oleic acid injury did not produce collapse of dependent lung units in this model of ARDS.46 They proposed an alternative mechanism for the topographic variability in regional impedances and lung expansion after injury, which was liquid or foam in alveoli and conducting airways.46 Factors Modulating the Formation of Atelectasis It is important for clinicians to understand how atel- ectasis develops or worsens in the clinical context....
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TL;DR: This paper presents experimental evidence for Increased Vascular Transmural Pressure Evidence for Alterations in Alveolar–Capillary Permeability Contributions of the Static and Dynamic Lung Volume Components to Ventilator-induced Edema High-volume Lung Edema Low Lung Volume Injury.
Abstract: Introduction: Ventilator-induced Lung Injury: Not Only Air Leaks Ventilation-induced Pulmonary Edema and Related Findings: A Historical Perspective Ventilation-induced Pulmonary Edema: Hydrostatic or Permeability Edema? Experimental Evidence for Increased Vascular Transmural Pressure Evidence for Alterations in Alveolar–Capillary Permeability Contributions of the Static and Dynamic Lung Volume Components to Ventilator-induced Edema High-volume Lung Edema Low Lung Volume Injury Effects of High-volume Ventilation on Abnormal Lungs Effects of High-volume Ventilation on Injured Lungs Interaction between Severe Alveolar Flooding and Mechanical Ventilation Effects of Resting the Lung on Ventilator-induced Lung Injury Possible Mechanisms of Ventilation-induced Lung Injury Mechanisms of Increased Vascular Transmural Pressure Mechanisms of Altered Permeability Clinical Relevance
2,259 citations
TL;DR: Mechanical ventilation can induce a cytokine response that may be attenuated by a strategy to minimize overdistention and recruitment/derecruitment of the lung, and these physiological improvements are associated with improvements in clinical end points.
Abstract: ContextStudies have shown that an inflammatory response may be elicited by
mechanical ventilation used for recruitment or derecruitment of collapsed
lung units or to overdistend alveolar regions, and that a lung-protective
strategy may reduce this response.ObjectiveTo test the hypothesis that mechanical ventilation induces a pulmonary
and systemic cytokine response that can be minimized by limiting recruitment
or derecruitment and overdistention.Design and SettingRandomized controlled trial in the intensive care units of 2 European
hospitals from November 1995 to February 1998, with a 28-day follow-up.PatientsForty-four patients (mean [SD] age, 50 [18] years) with acute respiratory
distress syndrome were enrolled, 7 of whom were withdrawn due to adverse events.InterventionsAfter admission, volume-pressure curves were measured and bronchoalveolar
lavage and blood samples were obtained. Patients were randomized to either
the control group (n=19): tidal volume to obtain normal values of arterial
carbon dioxide tension (35-40 mm Hg) and positive end-expiratory pressure
(PEEP) producing the greatest improvement in arterial oxygen saturation without
worsening hemodynamics; or the lung-protective strategy group (n=18): tidal
volume and PEEP based on the volume-pressure curve. Measurements were repeated
24 to 30 and 36 to 40 hours after randomization.Main Outcome MeasuresPulmonary and systemic concentrations of inflammatory mediators approximately
36 hours after randomization.ResultsPhysiological characteristics and cytokine concentrations were similar
in both groups at randomization. There were significant differences (mean
[SD]) between the control and lung-protective strategy groups in tidal volume
(11.1 [1.3] vs 7.6 [1.1] mL/kg), end-inspiratory plateau pressures (31.0 [4.5]
vs 24.6 [2.4] cm H2O), and PEEP (6.5 [1.7] vs 14.8 [2.7] cm H2O) (P<.001). Patients in the control group
had an increase in bronchoalveolar lavage concentrations of interleukin (IL)
1β, IL-6, and IL-1 receptor agonist and in both bronchoalveolar lavage
and plasma concentrations of tumor necrosis factor (TNF) α, IL-6, and
TNF-α receptors over 36 hours (P<.05 for
all). Patients in the lung-protective strategy group had a reduction in bronchoalveolar
lavage concentrations of polymorphonuclear cells, TNF-α, IL-1β,
soluble TNF-α receptor 55, and IL-8, and in plasma and bronchoalveolar
lavage concentrations of IL-6, soluble TNF-α receptor 75, and IL-1 receptor
antagonist (P<.05). The concentration of the inflammatory
mediators 36 hours after randomization was significantly lower in the lung-protective
strategy group than in the control group (P<.05).ConclusionsMechanical ventilation can induce a cytokine response that may be attenuated
by a strategy to minimize overdistention and recruitment/derecruitment of
the lung. Whether these physiological improvements are associated with improvements
in clinical end points should be determined in future studies.
1,715 citations