Extracorporeal membrane oxygenation improves survival in a novel 24-hour pig model of severe acute respiratory distress syndrome

Indexación: Web of Science; Pub Med CentralExtracorporeal membrane oxygenation (ECMO) is increasingly being used to treat severe acute respiratory distress syndrome (ARDS). However, there is limited clinical evidence about how to optimize the technique. Experimental research can provide an alternative to fill the actual knowledge gap. The purpose of the present study was to develop and validate an animal model of acute lung injury (ALI) which resembled severe ARDS, and which could be successfully supported with ECMO. Eighteen pigs were randomly allocated into three groups: sham, ALI, and ALI + ECMO. ALI was induced by a double-hit consisting in repeated saline lavage followed by a 2-hour period of injurious ventilation. All animals were followed up to 24 hours while being ventilated with conventional ventilation (tidal volume 10 ml/kg). The lung injury model resulted in severe hypoxemia, increased airway pressures, pulmonary hypertension, and altered alveolar membrane barrier function, as indicated by an increased protein concentration in bronchoalveolar fluid, and increased wet/dry lung weight ratio. Histologic examination revealed severe diffuse alveolar damage, characteristic of ARDS. Veno-venous ECMO was started at the end of lung injury induction with a flow > 60 ml/kg/min resulting in rapid reversal of hypoxemia and pulmonary hypertension. Mortality was 0, 66.6 and 16.6% in the SHAM, ALI and ALI + ECMO groups, respectively (p < 0.05). This is a novel clinically relevant animal model that can be used to optimize the approach to ECMO and foster translational research in extracorporeal lung support.http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4931177

Effects of positive end-expiratory pressure on gastric mucosal perfusion in acute respiratory distress syndrome

INTRODUCTION: Positive end-expiratory pressure (PEEP) improves oxygenation and can prevent ventilator-induced lung injury in patients with acute respiratory distress syndrome (ARDS). Nevertheless, PEEP can also induce detrimental effects by its influence on the cardiovascular system. The purpose of this study was to assess the effects of PEEP on gastric mucosal perfusion while applying a protective ventilatory strategy in patients with ARDS. METHODS: Eight patients were included. A pressure–volume curve was traced and ideal PEEP, defined as lower inflection point + 2 cmH(2)O, was determined. Gastric tonometry was measured continuously (Tonocap). After baseline measurements, 10, 15 and 20 cmH(2)O PEEP and ideal PEEP were applied for 30 min each. By the end of each period, hemodynamic, CO(2 )gap (gastric minus arterial partial pressures), and ventilatory measurements were performed. RESULTS: PEEP had no effect on CO(2 )gap (median [range], baseline: 19 [2–30] mmHg; PEEP 10: 19 [0–40] mmHg; PEEP 15: 18 [0–39] mmHg; PEEP 20: 17 [4–39] mmHg; ideal PEEP: 19 [9–39] mmHg; P = 0.18). Cardiac index also remained unchanged (baseline: 4.6 [2.5–6.3] l min(-1 )m(-2); PEEP 10: 4.5 [2.5–6.9] l min(-1 )m(-2); PEEP 15: 4.3 [2–6.8] l min(-1 )m(-2); PEEP 20: 4.7 [2.4–6.2] l min(-1 )m(-2); ideal PEEP: 5.1 [2.1–6.3] l min(-1 )m(-2); P = 0.08). One patient did not complete the protocol because of hypotension. CONCLUSION: PEEP of 10–20 cmH(2)O does not affect gastric mucosal perfusion and is hemodynamically well tolerated in most patients with ARDS, including those receiving adrenergic drugs

Preliminary study of ventilation with 4 ml/kg tidal volume in acute respiratory distress syndrome: feasibility and effects on cyclic recruitment - derecruitment and hyperinflation

INTRODUCTION: Cyclic recruitment-derecruitment and overdistension contribute to ventilator-induced lung injury. Tidal volume (Vt) may influence both, cyclic recruitment-derecruitment and overdistension. The goal of this study was to determine if decreasing Vt from 6 to 4 ml/kg reduces cyclic recruitment-derecruitment and hyperinflation, and if it is possible to avoid severe hypercapnia. METHODS: Patients with pulmonary acute respiratory distress syndrome (ARDS) were included in a crossover study with two Vt levels: 6 and 4 ml/kg. The protocol had two parts: one bedside and other at the CT room. To avoid severe hypercapnia in the 4 ml/kg arm, we replaced the heat and moisture exchange filter by a heated humidifier, and respiratory rate was increased to keep minute ventilation constant. Data on lung mechanics and gas exchange were taken at baseline and after 30 minutes at each Vt (bedside). Thereafter, a dynamic CT (4 images/sec for 8 sec) was taken at each Vt at a fixed transverse region between the middle and lower third of the lungs. Afterward, CT images were analyzed and cyclic recruitment-derecruitment was determined as non-aerated tissue variation between inspiration and expiration, and hyperinflation as maximal hyperinflated tissue at end-inspiration, expressed as % of lung tissue weight. RESULTS: We analyzed 10 patients. Decreasing Vt from 6 to 4 ml/kg consistently decreased cyclic recruitment-derecruitment from 3.6 (2.5 to 5.7) % to 2.9 (0.9 to 4.7) % (P <0.01) and end-inspiratory hyperinflation from 0.7 (0.3 to 2.2) to 0.6 (0.2 to 1.7) % (P = 0.01). No patient developed severe respiratory acidosis or severe hypercapnia when decreasing Vt to 4 ml/kg (pH 7.29 (7.21 to 7.46); PaCO2 48 (26 to 51) mmHg). CONCLUSIONS: Decreasing Vt from 6 to 4 ml/kg reduces cyclic recruitment-derecruitment and hyperinflation. Severe respiratory acidosis may be effectively prevented by decreasing instrumental dead space and by increasing respiratory rate

Extracorporeal membrane oxygenation improves survival in a novel 24-hour pig model of severe acute respiratory distress syndrome

Centro de Medicina RegenerativaExtracorporeal membrane oxygenation (ECMO) is increasingly being used to treat severe acute respiratory distress syndrome (ARDS). However, there is limited clinical evidence about how to optimize the technique. Experimental research can provide an alternative to fill the actual knowledge gap. The purpose of the present study was to develop and validate an animal model of acute lung injury (ALI) which resembled severe ARDS, and which could be successfully supported with ECMO. Eighteen pigs were randomly allocated into three groups: sham, ALI, and ALI + ECMO. ALI was induced by a double-hit consisting in repeated saline lavage followed by a 2-hour period of injurious ventilation. All animals were followed up to 24 hours while being ventilated with conventional ventilation (tidal volume 10 ml/kg). The lung injury model resulted in severe hypoxemia, increased airway pressures, pulmonary hypertension, and altered alveolar membrane barrier function, as indicated by an increased protein concentration in bronchoalveolar fluid, and increased wet/dry lung weight ratio. Histologic examination revealed severe diffuse alveolar damage, characteristic of ARDS. Veno-venous ECMO was started at the end of lung injury induction with a flow > 60 ml/kg/min resulting in rapid reversal of hypoxemia and pulmonary hypertension. Mortality was 0, 66.6 and 16.6% in the SHAM, ALI and ALI + ECMO groups, respectively (p < 0.05). This is a novel clinically relevant animal model that can be used to optimize the approach to ECMO and foster translational research in extracorporeal lung support

Recomendaciones de la Sociedad Chilena de Medicina Intensiva para la analgesia, sedación, delírium y bloqueo neuromuscular en pacientes críticos médico-quirúrgicos adultos

Los pacientes críticos habitualmente desarrollan dolor y ansiedad debido a su condición clínica y/o por las intervenciones y procedimientos necesarios para su atención, por esta razón la administración de analgésicos e hipnóticos es frecuente en la UPC. El empleo de una estrategia apropiada para el uso de la analgesia y sedación ha demostrado mejorar los desenlaces clínicos. El uso de bloqueadores neuromusculares tiene el potencial de ofrecer beneficios a pacientes críticos bien seleccionados; no obstante, pueden asociarse a debilidad muscular adquirida en la UCI. El delírium tiene una alta incidencia en pacientes críticos sometidos a ventilación mecánica, y es un predictor independiente de resultados adversos a corto y largo plazo. Las estrategias de prevención y su identificación precoz pueden ofrecer una oportunidad para mejorar la evolución de los pacientes. En consideración a la trascendencia de este importante tópico, la Sociedad Chilena de Medicina Intensiva (SOCHIMI) se propuso desarrollar un documento operativo con sugerencias y recomendaciones prácticas aplicables a nuestra población. Estas sugerencias y recomendaciones se realizaron en base a un análisis estructurado de la evidencia disponible, otras guías publicadas sobre el tema y la experiencia de un grupo multidisciplinario de profesionales de los cuidados críticos.Critically ill patients usually develop pain and anxiety due to their clinical condition and the procedures necessary for their care, for this reason the administration of analgesics and hypnotics is frequent at the Intensive Care Unit (ICU). The use of an appropriate strategy for the use of analgesia and sedation has been shown to improve clinical outcomes. The use of neuromuscular blockers has the potential to offer benefits to well-selected critical patients; however, they can be associated with ICU acquired weakness. Delirium has a high incidence in critically ill patients on mechanical ventilation, and is an independent predictor of short and long-term adverse results. Prevention strategies and their early identification can offer an opportunity to improve the outcome of patients. In consideration of the importance of this topic, the “Sociedad Chilena de Medicina Intensiva (SOCHIMI)” has proposed to develop an operative document with suggestions and practical recommendations feasible to apply in our population. These suggestions and recommendations have been made based on a structured analysis of the available evidence, other published guidelines on the subject and the experience of a multidisciplinary group of critical care professionals.Versión publicada - versión final del edito

Analgesia, sedation, neuromuscular blockade and delirium management practices in Chilean intensive care units

The appropriate use of analgesia, sedation, neuromuscular blockade and the diagnosis and prevention of delirium (ASBD) are associated with better outcomes in critically ill patients at Intensive Care Unit (ICUs). Aim: To know the practices about analgesia, sedation, delirium, and neuromuscular blockade use among healthcare professionals working in adult ICUs in Chile. Material and Method: An electronic survey was sent to 812 professionals working in ICUs using a previously published instrument, which was adapted and authorized by the author. Results: We received 278 surveys. Fifty two percent of respondents were physicians, 34% nurses and 11% physical therapists. Their age ranged between 30 and 39 years in 43% and was over 50 years in 9%. Eighty four percent evaluated pain routinely, but only 26% use a validated scale. Sedation was routinely evaluated with a validated scale and 73% referred to have a protocol. Neuromuscular block is seldom used, and little monitoring occurs (43%). Delirium is routinely evaluated by 48% of respondents, usually using the CAM-ICU scale. Conclusions: There is a heterogeneous adherence to the ASBD recommended practices. The main gaps are in the assessment of pain, monitoring of neuromuscular blockade and diagnosis of delirium through validated instruments.Versión publicada - versión final del edito

Low spontaneous breathing effort during extracorporeal membrane oxygenation in a porcine model of severe acute respiratory distress síndrome

Background: A lung rest strategy is recommended during extracorporeal membrane oxygenation in severe acute respiratory distress syndrome (ARDS). However, spontaneous breathing modes are frequently used in this context. The impact of this approach may depend on the intensity of breathing efforts. The authors aimed to determine whether a low spontaneous breathing effort strategy increases lung injury, compared to a controlled near-apneic ventilation, in a porcine severe ARDS model assisted by extracorporeal membrane oxygenation. Methods: Twelve female pigs were subjected to lung injury by repeated lavages, followed by 2-h injurious ventilation. Thereafter, animals were connected to venovenous extracorporeal membrane oxygenation and during the first 3 h, ventilated with near-apneic ventilation (positive end-expiratory pressure, 10 cm H2O; driving pressure, 10 cm H2O; respiratory rate, 5/min). Then, animals were allocated into (1) near-apneic ventilation, which continued with the previous ventilatory settings; and (2) spontaneous breathing: neuromuscular blockers were stopped, sweep gas flow was decreased until regaining spontaneous efforts, and ventilation was switched to pressure support mode (pressure support, 10 cm H2O; positive end-expiratory pressure, 10 cm H2O). In both groups, sweep gas flow was adjusted to keep Paco(2)between 30 and 50 mmHg. Respiratory and hemodynamic as well as electric impedance tomography data were collected. After 24 h, animals were euthanized and lungs extracted for histologic tissue analysis. Results: Compared to near-apneic group, the spontaneous breathing group exhibited a higher respiratory rate (52 +/- 17vs.5 +/- 0 breaths/min; mean difference, 47; 95% CI, 34 to 59;P< 0.001), but similar tidal volume (2.3 +/- 0.8vs.2.8 +/- 0.4 ml/kg; mean difference, 0.6; 95% CI, -0.4 to 1.4;P= 0.983). Extracorporeal membrane oxygenation settings and gas exchange were similar between groups. Dorsal ventilation was higher in the spontaneous breathing group. No differences were observed regarding histologic lung injury. Conclusions: In an animal model of severe ARDS supported with extracorporeal membrane oxygenation, spontaneous breathing characterized by low-intensity efforts, high respiratory rates, and very low tidal volumes did not result in increased lung injury compared to controlled near-apneic ventilation.CONICYT (Santiago, Chile) through grants FONDECYT 1161556 1191709 CONICYT (Santiago, Chile) PFCHA/Doctorado Nacional 21181376 2117155

Epidemiology and patterns of tracheostomy practice in patients with acute respiratory distress syndrome in ICUs across 50 countries

Background: To better understand the epidemiology and patterns of tracheostomy practice for patients with acute respiratory distress syndrome (ARDS), we investigated the current usage of tracheostomy in patients with ARDS recruited into the Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure (LUNG-SAFE) study. Methods: This is a secondary analysis of LUNG-SAFE, an international, multicenter, prospective cohort study of patients receiving invasive or noninvasive ventilation in 50 countries spanning 5 continents. The study was carried out over 4 weeks consecutively in the winter of 2014, and 459 ICUs participated. We evaluated the clinical characteristics, management and outcomes of patients that received tracheostomy, in the cohort of patients that developed ARDS on day 1-2 of acute hypoxemic respiratory failure, and in a subsequent propensity-matched cohort. Results: Of the 2377 patients with ARDS that fulfilled the inclusion criteria, 309 (13.0%) underwent tracheostomy during their ICU stay. Patients from high-income European countries (n = 198/1263) more frequently underwent tracheostomy compared to patients from non-European high-income countries (n = 63/649) or patients from middle-income countries (n = 48/465). Only 86/309 (27.8%) underwent tracheostomy on or before day 7, while the median timing of tracheostomy was 14 (Q1-Q3, 7-21) days after onset of ARDS. In the subsample matched by propensity score, ICU and hospital stay were longer in patients with tracheostomy. While patients with tracheostomy had the highest survival probability, there was no difference in 60-day or 90-day mortality in either the patient subgroup that survived for at least 5 days in ICU, or in the propensity-matched subsample. Conclusions: Most patients that receive tracheostomy do so after the first week of critical illness. Tracheostomy may prolong patient survival but does not reduce 60-day or 90-day mortality

Individual and combined effects of chemical and mechanical power on postoperative pulmonary complications: a secondary analysis of the REPEAT study

Introduction: Intra-operative supplemental oxygen and mechanical ventilation expose the lungs to potentially injurious energy. This can be quantified as 'chemical power' and 'mechanical power', respectively. In this study, we sought to determine if intra-operative chemical and mechanical power, individually and/or in combination, are associated with postoperative pulmonary complications. Methods: Using an individual patient data analysis of three randomised clinical trials of intra-operative ventilation, we summarised intra-operative chemical and mechanical power using time-weighted averages. We evaluated the association between intra-operative chemical and mechanical power and a collapsed composite of postoperative pulmonary complications using multivariable logistic regression to estimate the odds ratios related to the effect of 1 J.min-1 increase in chemical or mechanical power with adjustment for demographic and intra-operative characteristics. We also included an interaction term to assess for potential synergistic effects of chemical and mechanical power on postoperative pulmonary complications. Results: Of 3837 patients recruited to three individual trials, 2492 with full datasets were included in the analysis. Intra-operative time-weighted average (SD) chemical power was 10.2 (3.9) J.min-1 and mechanical power was 10.5 (4.4) J.min-1. An increase of 1 J.min-1 in chemical power was associated with 8% higher odds of postoperative pulmonary complications (OR 1.08, 95%CI 1.05-1.10, p &lt; 0.001), while the same increase in mechanical power raised odds by 5% (OR 1.05, 95%CI 1.02-1.08, p = 0.003). We did not find evidence of a significant interaction between chemical and mechanical power (p = 0.40), suggestive of an additive rather than synergistic effect on postoperative pulmonary complications. Discussion: Both chemical and mechanical power are independently associated with postoperative pulmonary complications. Further work is required to determine causality

Hyperoxemia and excess oxygen use in early acute respiratory distress syndrome: insights from the LUNG SAFE study

Contains fulltext : 218568.pdf (publisher's version ) (Open Access)BACKGROUND: Concerns exist regarding the prevalence and impact of unnecessary oxygen use in patients with acute respiratory distress syndrome (ARDS). We examined this issue in patients with ARDS enrolled in the Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE (LUNG SAFE) study. METHODS: In this secondary analysis of the LUNG SAFE study, we wished to determine the prevalence and the outcomes associated with hyperoxemia on day 1, sustained hyperoxemia, and excessive oxygen use in patients with early ARDS. Patients who fulfilled criteria of ARDS on day 1 and day 2 of acute hypoxemic respiratory failure were categorized based on the presence of hyperoxemia (PaO2 > 100 mmHg) on day 1, sustained (i.e., present on day 1 and day 2) hyperoxemia, or excessive oxygen use (FIO2 >/= 0.60 during hyperoxemia). RESULTS: Of 2005 patients that met the inclusion criteria, 131 (6.5%) were hypoxemic (PaO2 < 55 mmHg), 607 (30%) had hyperoxemia on day 1, and 250 (12%) had sustained hyperoxemia. Excess FIO2 use occurred in 400 (66%) out of 607 patients with hyperoxemia. Excess FIO2 use decreased from day 1 to day 2 of ARDS, with most hyperoxemic patients on day 2 receiving relatively low FIO2. Multivariate analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FIO2 use and adverse clinical outcomes. Mortality was 42% in patients with excess FIO2 use, compared to 39% in a propensity-matched sample of normoxemic (PaO2 55-100 mmHg) patients (P = 0.47). CONCLUSIONS: Hyperoxemia and excess oxygen use are both prevalent in early ARDS but are most often non-sustained. No relationship was found between hyperoxemia or excessive oxygen use and patient outcome in this cohort. TRIAL REGISTRATION: LUNG-SAFE is registered with ClinicalTrials.gov, NCT02010073