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Objective: To study the impact of a standardized postoperative anesthesia visit on 30-day mortality in medium to high-risk elective surgical patients. Background: Postoperative complications are the leading cause of perioperative morbidity and mortality. Although modified early warning scores (MEWS) were instituted to monitor vital functions and improve postoperative outcome, we hypothesized that complementary anesthesia expertise is needed to adequately identify early deterioration. Methods: In a prospective, multicenter, stepped-wedge cluster randomized interventional study in 9 academic and nonacademic hospitals in the Netherlands, we studied the impact of adding standardized postoperative anesthesia visits on day 1 and 3 to routine use of MEWS in 5473 patients undergoing elective noncardiac surgery. Primary outcome was 30-day mortality. Secondary outcomes included: incidence of postoperative complications, length of hospital stay, and intensive care unit admission. Results: Patients were enrolled between October 2016 and August 2018. Informed consent was obtained from 5473 patients of which 5190 were eligible for statistical analyses, 2490 in the control and 2700 in the intervention group. Thirty-day mortality was 0.56% (n = 14) in the control and 0.44% (n = 12) in the intervention group (odds ratio 0.74, 95% Confidence interval 0.34–1.62). Incidence of postoperative complications did not differ between groups except for renal complications which was higher in the control group (1.7% (n = 41) vs 1.0% (n = 27), P = 0.014). Median length of hospital stay did not differ significantly between groups. During the postanesthesia visits, for 16% (n = 437) and 11% (n = 293) of patients recommendations were given on day 1 and 3, respectively, of which 67% (n = 293) and 69% (n = 202) were followed up. Conclusions: The combination of MEWS and a postoperative anesthesia visit did not reduce 30-day mortality. Whether a postoperative anesthesia visit with strong adherence to the recommendations provided and in a high-risk population might have a stronger impact on postoperative mortality remains to be determined. Trial Registration: Netherlands Trial Registration, NTR5506/ NL5249, https://www.trialregister.nl/trial/5249. [ABSTRACT FROM AUTHOR]

Objective: To study the effects of intra-abdominal pressure on the quality of recovery and innate cytokine production capacity after laparoscopic colorectal surgery within the enhanced recovery after surgery program. Background: There is increasing evidence for the safety and advantages of low-pressure pneumoperitoneum facilitated by deep neuromuscular blockade (NMB). Nonetheless, there is a weak understanding of the relationship between clinical outcomes, surgical injury, postoperative immune dysfunction, and infectious complications. Methods: Randomized controlled trial of 178 patients treated at standard-pressure pneumoperitoneum (12 mm Hg) with moderate NMB (train-of-four 1–2) or low pressure (8 mm Hg) facilitated by deep NMB (posttetanic count 1–2). The primary outcome was the quality of recovery (Quality of Recovery 40 questionnaire) on a postoperative day 1 (POD1). The primary outcome of the immune substudy (n=100) was ex vivo tumor necrosis factor α production capacity upon endotoxin stimulation on POD1. Results: Quality of Recovery 40 score on POD1 was significantly higher at 167 versus 159 [mean difference (MD): 8.3 points; 95% confidence interval (CI): 2.5, 14.1; P =0.005] and the decline in cytokine production capacity was significantly less for tumor necrosis factor α and interleukin-6 (MD: −172 pg/mL; 95% CI: −316, −27; P =0.021 and MD: −1282 pg/mL; 95% CI: −2505, −59; P =0.040, respectively) for patients operated at low pressure. Low pressure was associated with reduced surgical site hypoxia and inflammation markers and circulating damage-associated molecular patterns, with a less impaired early postoperative ex vivo cytokine production capacity. At low pressure, patients reported lower acute pain scores and developed significantly less 30-day infectious complications. Conclusions: Low intra-abdominal pressure during laparoscopic colorectal surgery is safe, improves the postoperative quality of recovery and preserves innate immune homeostasis, and forms a valuable addition to future enhanced recovery after surgery programs. [ABSTRACT FROM AUTHOR]

BACKGROUND Shared decision-making (SDM) and decision-support tools have attracted broad support in healthcare as they improve medical decision-making. Experts disagree on how these can help patients evaluate their present situation and possible outcomes of therapy, and how they might reduce decisional conflict. Little is known about their implementation, especially in anaesthesiology. OBJECTIVE To obtain a more fundamental understanding of pre-operative SDM and evaluate the use of a decision-support tool for postoperative analgesia after major thoracic and abdominal surgery. DESIGN A qualitative study with semistructured, in-depth interviews of patients and professionals. SETTING Patient recruitment took place at the Radboud University Medical Centre in Nijmegen and the Canisius Wilhelmina Hospital in Nijmegen, a nonacademic teaching centre. Professionals of the Radboud University Medical Centre were invited to participate in the interviews. PARTICIPANTS Interviews were performed with 10 individual patients and two focus groups both consisting of eight different professionals. MAIN OUTCOME MEASURES To gain insight into the provision of pre-operative information, decision-making processes and the clarity and usability of a prototype decision-support tool. RESULTS Professionals seemed to provide their patients with information directed towards the application of epidural analgesia, providing little attention to its negative effects. For many patients, the information was not tailored to their needs. Patients' involvement in decision-making was minimal, but they did not feel a need for more involvement. They were positive about the decision-support tool, although they indicated that it would not have influenced their treatment decision. Professionals expressed their doubt about the capacity of their patients to fully understand the decisions involved and about the clinical usability of the decision-support tool, because patients might misinterpret the information provided. CONCLUSION The results of this study suggest that both patients and professionals did not adhere to some 'self-evident' principles of SDM when postoperative analgesia after major thoracic and abdominal surgery was discussed. [ABSTRACT FROM AUTHOR]

Background: Working in anaesthesia is stressful, but also satisfying. Work-related stress can have a negative impact on mental health, whereas work-related satisfaction protects against these harmful effects.Objective(s): How work stress and satisfaction are experienced may be related to personality. Our aim was to study the relationship between personality and perception of work in a sample of Dutch anaesthesiologists.Design: Questionnaire survey.Setting: Data were collected in the Netherlands from July 2012 until December 2012.Participants: We sent electronic questionnaires to all 1955 practising resident and consultant members of the Dutch Anaesthesia Society. Of those, 655 (33.5%) were returned and could be used for analysis.Main Outcome Measures: The questionnaires assessed general work-related stress and satisfaction and anaesthesia-specific stress. A factor analysis was performed on the stress and satisfaction questionnaires. Personality traits were assessed using the Big Five Inventory. To identify personality profiles, a cluster analysis was performed on the Big Five Inventory. Scores of the extracted factors contributing to job stress and satisfaction were compared between the profiles we identified.Results: Our analysis extracted six factors concerning general job stress. Of those, the emotionally difficult caseload contributed the most to job stress. The analysis also extracted four factors concerning general job satisfaction. Good relationships with patients and their families and being appreciated by colleagues contributed the most to satisfaction. The cluster analysis resulted in two distinct personality profiles: a distressed profile (n = 215) and a resilient profile (n = 440). General and anaesthesia-specific job stress was significantly higher and job satisfaction was significantly lower in the distressed profile, compared with the resilient profile. Experience of the emotionally difficult caseload did not differ between the two profiles CONCLUSION: Personality profiles were found to be related to anaesthesiologists' experience of work-related stress and satisfaction. One-third of the anaesthesiologists in our sample were categorised as distressed and are at risk of developing work-related mental health problems. [ABSTRACT FROM AUTHOR]

Hypoxia and immunity are highly intertwined at clinical, cellular, and molecular levels. The prevention of tissue hypoxia and modulation of systemic inflammation are cornerstones of daily practice in the intensive care unit. Potentially, immunologic effects of hypoxia may contribute to outcome and represent possible therapeutic targets. Hypoxia and activation of downstream signaling pathways result in enhanced innate immune responses, aimed to augment pathogen clearance. On the other hand, hypoxia also exerts antiinflammatory and tissue-protective effects in lymphocytes and other tissues. Although human data on the net immunologic effects of hypoxia and pharmacologic modulation of downstream pathways are limited, preclinical data support the concept of tailoring the immune response through modulation of the oxygen status or pharmacologic modulation of hypoxia-signaling pathways in critically ill patients. [ABSTRACT FROM AUTHOR]

Background: The practice of anaesthesia comes with stress. If the demands of a stressful job exceed the resources of an individual, that person may develop burnout. Burnout poses a threat to the mental and physical health of the anaesthesiologist and therefore also to patient safety.Objectives: Individual differences in stress appraisal (perceived demands) are an important factor in the risk of developing burnout. To explore this possible relationship, we assessed the prevalence of psychological distress and burnout in the Dutch anaesthesiologist population and investigated the influence of personality traits.Design: Survey study.Setting: Data were collected in the Netherlands from July 2012 until December 2012.Participants: We sent electronic surveys to all 1955 practising resident and consultant members of the Dutch Anaesthesia Society. Of these, 655 (33.5%) were returned and could be used for analysis.Main Outcome Measures: Psychological distress, burnout and general personality traits were assessed using validated Dutch versions of the General Health Questionnaire (cut-off point ≥2), the Maslach Burnout Inventory and the Big Five Inventory. Sociodemographic variables and personality traits were entered into regression models as predictors for burnout and psychological distress.Results: Respectively, psychological distress and burnout were prevalent in 39.4 and 18% of all respondents. The prevalence of burnout was significantly different in resident and consultant anaesthesiologists: 11.3% vs. 19.8% (χ 5.4; P < 0.02). The most important personality trait influencing psychological distress and burnout was neuroticism: adjusted odds ratio 6.22 (95% confidence interval 4.35 to 8.90) and 6.40 (95% confidence interval 3.98 to 10.3), respectively.Conclusion: The results of this study show that psychological distress and burnout have a high prevalence in residents and consultant anaesthesiologists and that both are strongly related to personality traits, especially the trait of neuroticism. This suggests that strategies to address the problem of burnout would do well to focus on competence in coping skills and staying resilient. Personality traits could be taken into consideration during the selection of residents. In future longitudinal studies the question of how personal and situational factors interact in the development of burnout should be addressed. [ABSTRACT FROM AUTHOR]

3-Hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitors (statins) are effective in the primary and secondary prevention of cardiovascular events. Although originally developed to improve lipid profile, statins have demonstrated a surplus of beneficial pleiotropic effects, including improved endothelial function, reduced inflammation, and increased tolerance to ischemia-reperfusion injury. In preclinical studies, increased ecto-5'-nucleotidase activity, the key enzyme in extracellular adenosine formation, plays an important role in these effects. Because human data are absent, we explored the effects of rosuvastatin on ecto-5'-nucleotidase activity and the clinical relevance of increased extracellular adenosine during ischemia in humans in vivo. The forearm vasodilator responses to 3 increasing periods of forearm ischemia (2, 5, and 13 minutes) were determined during placebo and caffeine (an adenosine receptor antagonist) infusion into the brachial artery. At the end of an 8-day treatment period with rosuvastatin (20 mg per day), this whole procedure was repeated. During both experiments, ecto-5'-nucleotidase activity was determined. Vasodilator responses are expressed as the percentage increase in forearm blood flow ratio from baseline. Rosuvastatin increased ecto-5'-nucleotidase activity by 49±17% and enhanced the vasodilator response after 2, 5, and 13 minutes of ischemia in the absence (146±19, 330±26, and 987±133 to 312±77, 566±107, and 1533±267) but not in the presence of caffeine (98±25, 264±54, and 727±111 versus 95±19, 205±34, and 530±62). Rosuvastatin increases extracellular formation of adenosine in humans in vivo probably by enhancing ecto-5'-nucleotidase activity. This action results in the improvement of reactive hyperemia and may further enhance the clinical benefit of statins, in particular in conditions of ischemia. [ABSTRACT FROM AUTHOR]

Danger-associated molecular patterns (DAMPs) that are released by injured, threatened, or dead cells, or that originate from the extracellular matrix, influence the immune system. This is of great relevance in critically ill patients, in whom trauma or surgery-related cell damage, hypoxia, ischemia, and infections can result in extensive release of DAMPs. As many patients at the intensive care unit suffer from immune system-related complications, DAMPs could serve as markers for the prognosis of these patients and represent possible therapeutic targets. In the present review, we provide an overview of several well known DAMPs (high-mobility group box 1, heat-shock proteins, s100 proteins, nucleic acids, and hyaluronan) and their effects on the immune system. Furthermore, we discuss the role of DAMPs as markers or therapeutic targets in several conditions frequently encountered in critically ill patients, such as sepsis, trauma, ventilator-induced lung injury, and cardiac arrest.

Both the initial trauma and the subsequent hemodynamic instability may contribute to intestinal damage, which is of great importance in (immunological) posttrauma complications. This study assesses intestinal damage using the biomarker intestinal Fatty Acid Binding Protein (iFABP) in trauma patients during the first days of their hospital admission and the risk factors involved. Plasma iFABP levels were measured in blood samples obtained from adult multiple trauma patients (n = 93) at the trauma scene by the Helicopter Emergency Medical Services, at arrival at the emergency department (ED), and at days 1, 3, 5, 7, 10, and 14 after trauma and related to injury severity and hemodynamic parameters. Plasma iFABP concentrations showed highest levels immediately after trauma at time points Helicopter Emergency Medical Services and ED. Nonsurvivors demonstrated higher iFABP levels at the ED compared with survivors. Furthermore, iFABP values at the ED correlated with Injury Severity Scores, and patients suffering from abdominal trauma demonstrated significantly higher iFABP concentrations in comparison with patients with other types of trauma or healthy controls. Also, patients presenting with a mean arterial pressure (MAP) less than 70 mmHg at the ED demonstrated significantly higher plasma iFABP concentrations in comparison with patients with a normal (70-99 mmHg) or high (>100 mmHg) MAP or healthy controls. Finally, patients with a low hemoglobin (Hb) (<80% of reference value) displayed significantly higher iFABP concentrations in comparison with patients with a normal Hb or healthy controls. Plasma iFABP levels, indicative of intestinal injury, are increased immediately after trauma in patients with abdominal trauma, low MAP, or low Hb and are related to the severity of the trauma. As intestinal injury is suggested to be related to late complications, such as multiorgan dysfunction syndrome or sepsis in trauma patients, strategies to prevent intestinal damage after trauma could be of benefit to these patients.

Background: Mechanical ventilation induces diaphragm muscle atrophy, which plays a key role in difficult weaning from mechanical ventilation. The signaling pathways involved in ventilator-induced diaphragm atrophy are poorly understood. The current study investigated the role of Toll-like receptor 4 signaling in the development of ventilator-induced diaphragm atrophy., Methods: Unventilated animals were selected for control: wild-type (n = 6) and Toll-like receptor 4 deficient mice (n = 6). Mechanical ventilation (8 h): wild-type (n = 8) and Toll-like receptor 4 deficient (n = 7) mice.Myosin heavy chain content, proinflammatory cytokines, proteolytic activity of the ubiquitin-proteasome pathway, caspase-3 activity, and autophagy were measured in the diaphragm., Results: Mechanical ventilation reduced myosin content by approximately 50% in diaphragms of wild-type mice (P less than 0.05). In contrast, ventilation of Toll-like receptor 4 deficient mice did not significantly affect diaphragm myosin content. Likewise, mechanical ventilation significantly increased interleukin-6 and keratinocyte-derived chemokine in the diaphragm of wild-type mice, but not in ventilated Toll-like receptor 4 deficient mice. Mechanical ventilation increased diaphragmatic muscle atrophy factor box transcription in both wild-type and Toll-like receptor 4 deficient mice. Other components of the ubiquitin-proteasome pathway and caspase-3 activity were not affected by ventilation of either wild-type mice or Toll-like receptor 4 deficient mice. Mechanical ventilation induced autophagy in diaphragms of ventilated wild-type mice, but not Toll-like receptor 4 deficient mice., Conclusion: Toll-like receptor 4 signaling plays an important role in the development of ventilator-induced diaphragm atrophy, most likely through increased expression of cytokines and activation of lysosomal autophagy.

Introduction: The interaction between neutrophils and activated endothelium is essential for the development of multiple organ dysfunction in patients with hemorrhagic shock (HS). Mechanical ventilation frequently is used in patients with HS. The authors sought to investigate the consequences of mechanical ventilation of mice subjected to HS on microvascular endothelial activation in the lung and kidney., Methods: Anesthetized wild type C57BL/6 male mice were subjected to controlled hemorrhage; subgroups of mice were mechanically ventilated during the HS insult. To study the effect of acute hypoxia on the mice, the animals were housed in hypoxic cages. Gene expression levels was assessed by quantitative real-time polymerase chain reaction. Protein expression was assessed by immunohistochemistry and enzyme-linked immunosorbent assay., Results: Ninety minutes after the shock induction, a vascular bed-specific, heterogeneous proinflammatory endothelial activation represented by E-selectin, vascular cell adhesion molecule 1, and intercellular adhesion molecule 1 expression was seen in kidney and lung. No differences in adhesion molecules between the spontaneously breathing and mechanically ventilated mice were found. Concentrations of the proinflammatory cytokines chemokine (C-X-C motif) ligand 1 (11.0-fold) and interleukin-6 (21.7-fold) were increased after 90 min of HS. Two hours of 6% oxygen did not induce the expression of E-selectin, vascular cell adhesion molecule 1, and intercellular adhesion molecule 1 in the kidneys and the lung., Conclusions: Hemorrhagic shock leads to an early and reversible proinflammatory endothelial activation in kidney and lung. HS-induced endothelial activation is not changed by mechanical ventilation during the shock phase. Hypoxia alone does not lead to endothelial activation. The observed proinflammatory endothelial activation is mostly ischemia- or reperfusion-dependent and not related to hypoxia.

Background: Mechanical ventilation (MV) can induce lung injury. Proinflammatory cytokines have been shown to play an important role in the development of ventilator-induced lung injury. Previously, the authors have shown a role for Toll-like receptor 4 signaling. The current study aims to investigate the role of Toll/interleukin-1 receptor domain-containing adapter-inducing interferon-beta (TRIF), a protein downstream of Toll-like receptors, in the development of the inflammatory response after MV in healthy mice., Methods: Wild-type C57BL6 and TRIF mutant mice were mechanically ventilated for 4 h. Lung tissue and plasma was used to investigate changes in cytokine profile, leukocyte influx, and nuclear factor-kappaB activity. In addition, experiments were performed to assess the role of TRIF in changes in cardiopulmonary physiology after MV., Results: MV significantly increased messenger RNA expression of interleukin (IL)-1beta in wild-type mice, but not in TRIF mutant mice. In lung homogenates, MV increased levels of IL-1alpha, IL-1beta, and keratinocyte-derived chemokine in wild-type mice. In contrast, in TRIF mutant mice, only a minor increase in IL-1beta and keratinocyte-derived chemokine was found after MV. Nuclear factor-kappaB activity after MV was significantly lower in TRIF mutant mice compared with wild-type mice. In plasma, MV increased levels of IL-6 and keratinocyte-derived chemokine. In TRIF mutant mice, no increase of IL-6 was found after MV, and the increase in keratinocyte-derived chemokine appeared less pronounced. TRIF deletion did not affect cardiopulmonary physiology after MV., Conclusions: The current study supports a prominent role for TRIF in the development of the pulmonary and systemic inflammatory response after MV.

Background: To evaluate the use of the bone injection gun to obtain vascular access in the prehospital setting by an Helicopter-Transported Emergency Medical Team., Methods: Prospective descriptive study to assess the frequency and success rate of the use of the bone injection gun in prehospital care by a Helicopter-Transported Emergency Medical Team., Results: In 40 of 780 (5.1%) patients, an attempt was made to obtain intraosseous access with the bone injection gun. Intraosseous access was attempted more often in children than in adults (p < 0.01). The success rate was 71% (10 out of 14) in children <16 years and 73% (19 out of 26) in adults (p = 1.0). There were no complications to the health care providers involved and no unwanted sequels to the patients involved., Conclusions: The bone injection gun is an effective and safe device for the resuscitation of patients in a prehospital setting. It seems to be equivalent in success rate as intraosseous needles in children, but it seems to be more successful in adults.

Objective: Statins may increase extracellular adenosine formation from adenosine monophosphate by enhancing ecto-5'-nucleotidase activity. This theory was tested in humans using dipyridamole-induced vasodilation as a read-out for local adenosine formation. Dipyridamole inhibits the transport of extracellular adenosine into the cytosol resulting in increased extracellular adenosine and subsequent vasodilation. In addition, we studied the effect of statin therapy in a forearm model of ischemia-reperfusion injury., Methods and Results: Volunteers randomly received rosuvastatin or placebo in a double-blind parallel design (n=21). The forearm vasodilator response to intraarterial dipyridamole was determined in the absence and presence of the adenosine antagonist caffeine. During a separate visit the vasodilator response to nitroprusside and adenosine was established. In addition, healthy men were randomly divided in 3 groups to receive either placebo (n=10), rosuvastatin (n=22), or rosuvastatin combined with intravenous caffeine (n=12). Subsequently, volunteers performed forearm ischemic exercise. At reperfusion, Tc-99m-labeled annexin A5 was infused intravenously and scintigraphic images were acquired, providing an early marker of cell injury. Rosuvastatin treatment significantly increased the vasodilator response to dipyridamole, which was prevented by caffeine. Rosuvastatin did not influence the response to either sodium nitroprusside or adenosine indicating a specific interaction between rosuvastatin and dipyridamole, which does not result from an effect of rosuvastatin on adenosine clearance nor adenosine-receptor affinity or efficacy. Rosuvastatin increased tolerance to ischemia-reperfusion injury, which was attenuated by caffeine., Conclusions: Rosuvastatin increases extracellular adenosine formation, which provides protection against ischemia-reperfusion injury in humans in vivo. Therefore, statins and dipyridamole may interact synergistically.

Introduction: Continuous noninvasive arterial blood pressure can be measured in finger arteries using an inflatable finger cuff (FINAP) with a special device and has proven to be feasible and reliable in adults. We studied prototype pediatric finger cuffs and pediatric software to compare this blood pressure measurement with intraarterially measured blood pressure (IAP) in critically ill children., Methods: We included sedated and mechanically ventilated children admitted to our pediatric intensive care unit. We performed simultaneous arterial blood pressure measurements during a relatively stable hemodynamic period and compared FINAP, IAP, and the noninvasive blood pressure oscillometric technique. We also compared IAP to a reconstruction of brachial pressure from finger pressure., Results: Thirty-five children between 2 and 22 kg body weight were included. In total, 152 attempts to record a FINAP pressure were performed of which 4.6% were unsuccessful. When comparing FINAP to IAP, bias was -16.2, -7.7, and -10.2 mm Hg for systolic arterial blood pressure, diastolic arterial blood pressure, and mean arterial blood pressure. Limits of agreement (LOA) were respectively 26.1%, 30.1%, and 22.6%. When reconstruction of brachial pressure from finger pressure was compared to IAP, these results were -11.8, 0.6, and -0.9 mm Hg for bias and 21.7%, 8.9%, and 8.9% for LOA. When noninvasive blood pressure oscillometric technique was compared to IAP, the results were: -6.8, -0.9, and -3.8 mm Hg for bias and 18.2%, 38.6%, and 22.1% for LOA., Conclusion: Beta type continuous noninvasive arterial blood pressure monitoring using a finger cuff with brachial arterial waveform reconstruction seems reliable in hemodynamically stable critically ill children.

Background: Mechanical ventilation (MV) can induce ventilator-induced lung injury. A role for proinflammatory pathways has been proposed. The current studies analyzed the roles of Toll-like receptor (TLR) 4 and TLR2 involvement in the inflammatory response after MV in the healthy lung., Methods: Wild-type (WT) C57BL6, TLR4 knockout (KO), and TLR2 KO mice were mechanically ventilated for 4 h. Bronchoalveolar lavage fluid was analyzed for presence of endogenous ligands. Lung homogenates were used to investigate changes in TLR4 and TLR2 expression. Cytokines were measured in lung homogenate and plasma, and leukocytes were counted in lung tissue., Results: MV significantly increased endogenous ligands for TLR4 in bronchoalveolar lavage fluid and relative messenger RNA expression of TLR4 and TLR2 in lung tissue. In lung homogenates, MV in WT mice increased levels of keratinocyte-derived chemokine, interleukin (IL)-1alpha, and IL-1beta. In TLR4 KO mice, MV increased IL-1alpha but not IL-1beta, and the increase in keratinocyte-derived chemokine was less pronounced. In plasma, MV in WT mice increased levels of IL-6, keratinocyte-derived chemokine, and tumor necrosis factor alpha. In TLR4 KO mice, MV did not increase levels of IL-6 or tumor necrosis factor alpha, and the response of keratinocyte-derived chemokine was less pronounced. MV in TLR2 KO mice did not result in different cytokine levels compared with WT mice. In WT and TLR2 KO mice, but not in TLR4 KO mice, MV increased the number of pulmonary leukocytes., Conclusions: The current study supports a role for TLR4 in the inflammatory reaction after short-term MV in healthy lungs. Increasing the understanding of the innate immune response to MV may lead to future treatment advances in ventilator-induced lung injury, in which TLR4 may serve as a therapeutic target.

Background: Mechanical ventilation (MV) may activate the innate immune system, causing the release of cytokines. The resulting proinflammatory state is a risk factor for ventilator-induced lung injury. Cytokine increase results from direct cellular injury but may also result from cyclic stretch alone as demonstrated in vitro: mechanotransduction. To study mechanotransduction in vivo, the authors used an animal MV model with clinically relevant ventilator settings, avoiding alveolar damage., Methods: Healthy C57BL6 mice (n = 82) were ventilated (tidal volume, 8 ml/kg; positive end-expiratory pressure, 4 cm H2O; fraction of inspired oxygen, 0.4) for 30, 60, 120, and 240 min. Assigned animals were allowed to recover for 2 days after MV. Both pulmonary tissue and plasma interleukin (IL)-1alpha, IL-1beta, tumor necrosis factor alpha, IL-6, IL-10, and keratinocyte-derived chemokine levels were measured. Histopathologic appearance of lung tissue was analyzed by light microscopy and electron microscopy., Results: In lung tissue, all measured cytokines and keratinocyte-derived chemokine levels increased progressively with MV duration. Light microscopy showed increased leukocyte influx but no signs of alveolar leakage or albumin deposition. Electron microscopy revealed intact epithelial cell and basement membranes with sporadically minimal signs of partial endothelial detachment. In plasma, increased levels of IL-1alpha, tumor necrosis factor alpha, IL-6, and keratinocyte-derived chemokine were measured after MV. In the recovery animals, cytokine levels had normalized and no histologic alterations could be found., Conclusions: Mechanical ventilation induces reversible cytokine increase and leukocyte influx with preserved tissue integrity. This model offers opportunities to study the pathophysiologic mechanisms behind ventilator-induced lung injury and the contribution of MV to the "multiple-hit" concept.