Acute_Lung_Injury_ARDS_-_FINAL2

Acute_Lung_Injury_ARDS_-_FINAL2 - Acute Lung Injury and...

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Unformatted text preview: Acute Lung Injury and ARDS Acute Pierre Moine, MD, PhD Associate Professor of Anesthesiology Department of Anesthesiology Edward Abraham, MD Roger Sherman Mitchell Professor of Pulmonary and Critical Care Medicine Vice Chair, Department of Medicine Head, Division of Pulmonary Sciences and Critical Care Medicine University of Colorado Health Sciences Center Definitions Definitions The 1994 North American-European Consensus Conference (NAECC) criteria: • Onset - Acute and persistent • Radiographic criteria - Bilateral pulmonary infiltrates consistent with the presence of edema • Oxygenation criteria - Impaired oxygenation regardless of the PEEP concentration, with a Pao2/Fio2 ratio ≤ 300 torr (40 kPa) for ALI and ≤ 200 torr (27 kPa) for ARDS • Exclusion criteria - Clinical evidence of left atrial hypertension or a pulmonary-artery catheter occlusion pressure of ≥ 18 mm Hg. Bernard GR et al., Am J Respir Crit Care Med 1994 The 1994 NAECC Definition Limitations The Descriptive definition - Permits inclusion of a multiplicity of clinical entities ranging from autoimmune disorders to direct and indirect pulmonary injury Does not address the cause of lung injury Does not provide guidelines on how to define acute The radiological criteria are not sufficiently specific Does not account for the level of PEEP used, which affects the Pao2/Fio2 ratio Does not specify the presence of nonpulmonary organ system dysfunction at the time of diagnosis Does not include the different specific mechanistic pathways involved in producing lung injury Atabai K and Matthay MA, Thorax 2000 Abraham E et al., Crit Care Med 2000 The 1998 NAECC Updated Recommendations Recommendations 1. The collection of epidemiologic data should be based on the 1994 NAECC definitions. 2. The severity of ALI/ARDS should be assessed by the Lung Injury Score (LIS) or by the APACHE III or SAPS II scoring systems. 3. The factors that affect prognosis should be taken into account. The most important of these are incorporated into the GOCA stratification system. 4. It will be also useful to record: • • • • Information relating to etiology (at a minimum, direct or indirect cause) Mortality, including cause of death, and whether death was associated with withdrawal of care Presence of failure of other organs and other time-dependent covariates Follow-up information, including recovery of lung function and quality of life Artigas A et al., Am J Respir Crit Care Med 1998 Stratification System of Acute Lung Injury GOCA GOCA Letter Meaning O C A Definition 0 1 2 3 A B C D Pao2/Fio2 ≥ 301 Pao2/Fio2 200 -300 Pao2/Fio2 101 – 200 Pao2/Fio2 ≤ 100 Spontaneous breathing, no PEEP Assisted breathing, PEEP 0-5 cmH2O Assisted breathing, PEEP 6-10 cmH2O Assisted breathing, PEEP ≥ 10 cmH2O Organ failure A B C D Lung only Lung + 1 organ Lung + 2 organs Lung + ≥ 3 organs Cause 1 2 3 Unknown Direct lung injury Indirect lung injury 0 1 No coexisting disease that will cause death within 5 yr Coexisting disease that will cause death within 5 yr but not within 6 mo Coexisting disease that will cause death within 6 mo Gas exchange G Scale Gas exchange (to be combined with the numeric descriptor) Associated diseases 2 Artigas A, et al. Am J Respir Crit Care Med. 1998. Epidemiology Epidemiology NIH, 1972 - Incidence of ARDS in the United States: 75 cases per 105 person.years population (approximately 150,000 cases per year) International multi-center ALI/ARDS cohort studies, 1989 - 2002 • Incidence estimates of ALI/ARDS = 1.3 to 22 cases per 10 5 person.years ARDS Network Study (NAECC definitions), 2003 - Incidence of ALI/ARDS in the United States: 32 cases per 10 5 person.years (range 16 - 64) ARDS Network Study (NAECC definitions), 2003 - The average number of cases of ALI per ICU bed per year (2.2) varied significantly from site to site (range 0.7 - 5.8) Goss CH et al., ARDS Network, Crit Care Med 2003 Clinical Disorders Associated with the Development of ALI/ARDS Development Direct insult Common Indirect insult Common Aspiration pneumonia Pneumonia Less common Inhalation injury Pulmonary contusions Fat emboli Near drowning Reperfusion injury Sepsis Severe trauma Shock Less common Atabai K, Matthay MA. Thorax. 2000. Frutos-Vivar F, et al. Curr Opin Crit Care. 2004. Acute pancreatitis Cardiopulmonary bypass Transfusion-related TRALI Disseminated intravascular coagulation Burns Head injury Drug overdose Clinical Risk Factors Predictive of a Poor Outcome Outcome Independent predictors Independent repeatedly associated with higher mortality rates higher Severity of the illness (SAPS II and APACHE) Non-pulmonary organ dysfunction Comorbid diseases Sepsis Liver dysfunction/cirrhosis Advanced age Atabai K, Matthay MA. Thorax. 2000. Ware LB. Crit Care Med. 2005. Ferguson ND, et al. Crit Care Med. 2005. Other independent predictors Late ARDS (≥ 48 hours after MV initiation) or length of MV prior to ARDS Organ transplantation HIV infection Immunosuppression Active malignancy Oxygenation index (mean airway pressure x Fio2 x 100/Pao2) Mechanisms of lung injury Barotrauma Right ventricular dysfunction Fio2 (High Fio2) Pao2/Fio2<100 mmHg/Pao2/Fio2 on day 3 Dead-space fraction Lower levels of PEEP or no PEEP Late respiratory acidosis McCabe score Chronic alcoholism Plasma Biologic Markers Predictive of a Poor Outcome Predictive Acute inflammation Interleukin(IL)-6, IL-8 Endothelial injury von Willebrand factor antigen Epithelial type II cell molecules Surfactant protein-D Adhesion molecule Intercellular adhesion molecule-1 (ICAM-1) Neutrophil-endothelial interaction Soluble tumor necrosis factor receptors I and II (sTNFRI/II) Procoagulant activity Protein C Fibrinolytic activity Plasminogen activator inhibitor-1 Ware LB. Crit Care Med. 2005. Mortality from ARDS Mortality ARDS mortality rates - 31% to 74% The variability in the rates quoted is related to differences in the populations studied and in the precise definitions used. The main causes of death are nonrespiratory causes (i.e., die with, rather than of, ARDS). Respiratory failure has been reported as the cause of death in 9% to 16% of patients with ARDS. Early deaths (within 72 hours) are caused by the underlying illness or injury, whereas late deaths are caused by sepsis or multiorgan dysfunction. There is a controversy about the role of hypoxemia as a prognostic factor in adults. Nevertheless, in some studies, both Pao2/Fio2 ratio and Fio2 were variables independently associated to mortality. Frutos-Vivar F, et al. Curr Opin Crit Care. 2004. Vincent JL, et al. Crit Care Med. 2003. Ware LB. Crit Care Med. 2005. One-year Outcomes in Survivors of the Acute Respiratory Distress Syndrome Acute Persistent functional limitation • Extrapulmonary diseases (primarily): Muscle wasting and weakness (corticosteroid-induced and critical-illness-associated myopathy) Entrapment neuropathy Heterotopic ossification • Intrinsic pulmonary morbidity (5%): Bronchiolitis obliterans organizing pneumonia Bronchiolitis obliterans Herridge MS, et al. N Engl J Med. 2003. Ventilatory-based Strategies in the Management of ARDS/ALI the Positive-pressure Mechanical Ventilation Ventilation Currently, the only therapy that has been proven to be effective at reducing mortality in ALI/ARDS in a large, randomized, multi-center, controlled trial is a protective ventilatory strategy. Tidal volume and plateau pressure Ventilator-induced Lung Injury Ventilator-induced Conceptual Framework Lung injury from: • Overdistension/shear - > physical injury • Mechanotransduction - > “biotrauma” “volutrauma” • Repetitive opening/closing • Shear at open/collapsed lung interface “atelectrauma” Systemic inflammation and death from: • Systemic release of cytokines, endotoxin, bacteria, proteases Ventilator-induced Lung Injury Ventilator-induced Three different pathologic entities: • High-permeability type pulmonary edema • Mechanical over-inflation/distortion of lung structures • Lung inflammation “Biotrauma” Rouby JJ, et al. Anesthesiology. 2004. Ventilator-induced Lung Injury Ventilator-induced High-permeability type pulmonary edema • Main causative factor: End-inspiratory lung volume >> peak inspiratory pressure “volutrauma more appropriate than barotrauma” • Mechanisms altering the alveolar-capillary barrier permeability during MV involve: - Increased transmural vascular pressure Surfactant inactivation Mechanical distortion and disruption of endothelial cells Regional activation of inflammatory cells Rouby JJ, et al. Anesthesiology. 2004. Ricard JD, et al. Eur Respir J. 2003. Ventilator-induced Lung Injury Ventilator-induced Mechanical overinflation/distortion of lung structures • Emphysema-like lesions, lung cysts, and bronchiectasis • These lesions predominate in nondependent and caudal lung regions • The degree of overinflation is dependent on: - Tidal volume - Peak airway pressure - Duration of mechanical ventilation - Time exposed to an Fio2 > 0.6 Rouby JJ, et al. Anesthesiology. 2004. Ventilator-induced Lung Injury Ventilator-induced Lung inflammation “biotrauma” • Lung overinflation or overstretching produces regional and systemic inflammatoryresponse that may generate or amplify multiple-system organ failure. • Factors converting the shear stress applied to an injured lung into regional and systemic inflammation are still incompletely elucidated but could include: - Repetitive opening and collapse of atelectatic lung units - Surfactant alterations - Loss of alveolo-capillary barrier function - Bacterial translocation - Overinflation of health lung regions Rouby JJ, et al. Anesthesiology. 2004. Dreyfuss D, et al. Am J Respir Crit Care Med. 2003. Ventilator-induced Lung Injury Ventilator-induced Two primary mechanistic factors: • Overdistension of the alveoli by high transpulmonary pressures: volutrauma • Shear-stress forces produced by repetitive alveolar recruitment and derecruitment (collapse) Animal data so compelling that in early 1990s the SCCM and ACCP recommended reduction in tidal volume and limiting endexpiratory plateau pressure to < 35 cm H20 Tidal Volume Strategies in ARDS Tidal Traditional Approach High priority to traditional goals of acid-base balance and patient comfort Lower priority to lung protection Low Stretch Approach High priority to lung protection Lower priority to traditional goals of acid-base balance and comfort ARDS Net Study 01: Hypothesis ARDS In patients with ALI/ARDS, ventilation with reduced tidal volume will limit “volutrauma” and improve survival. “Lung-protective strategies” ARDS Network. N Engl J Med. 2000. ARDS Network Low VT Trial ARDS Patients with ALI/ARDS (NAECC definitions) of < 36 hours Ventilator procedures • Volume-assist-control mode • RCT of 6 vs. 12 ml/kg of predicted body weight PBW Tidal Volume (PBW/Measured body weight = 0.83) • Plateau pressure ≤ 30 vs. ≤ 50 cmH2O • Ventilator rate setting 6-35 (breaths/min) to achieve a pH goal of 7.3 to 7.45 • I/E ratio:1.1 to 1.3 • Oxygenation goal: PaO2 55 - 80 mmHg/SpO2 88 - 95% • Allowable combination of FiO2 and PEEP: FiO2 0.3 0.4 0.4 0.5 0.5 0.6 0.7 0.7 0.7 0.8 0.9 0.9 0.9 1.0 1.0 1.0 1.0 PEEP 5 5 8 8 10 10 10 12 14 14 14 16 18 18 20 22 24 The trial was stopped early after the fourth interim analysis (n = 861 for efficacy; p = 0.005 for the difference in mortality between groups) ARDS Network. N Engl J Med. 2000. ARDS Network: Improved Survival with Low VT Improved 1.0 Proportion of Patients 0.9 0.8 0.7 0.6 0.5 Lower tidal volumes Survival Discharge Traditional tidal values Survival Discharge 0.4 0.3 0.2 0.1 0.0 0 20 40 60 80 100 120 Days after Randomization ARDS Network. N Engl J Med. 2000. 140 160 180 ARDS Network: Main Outcome Variables Main Low Vt Traditional Vt p Value Death before discharge home and breathing without assistance (%) 31.0 39.8 0.007 Breathing without assistance by day 28 (%) 65.7 55.0 < 0.001 12 ± 11 10 ± 11 0.007 10 11 0.43 15 ± 11 12 ± 11 0.006 No. of ventilator-free days, days 1 to 28 Barotrauma, days 1 to 28 (%) No. of days without failure of nonpulmonary organs or systems, days 1 to 28 ARDS Network. N Engl J Med. 2000. Median Organ Failure Free Days Median Pulmonary = 6 ml/kg = 12 ml/kg CNS * Hepatic * Cardiovascular * Coagulation * Renal 0 7 14 Days 21 28 ARDS Network: Additional Findings ARDS In ALI and ARDS patients, 6 ml/kg PBW tidal volume ventilation strategy was associated with: • PaO2/FiO2 lower in 6 ml/kg low VT group • High RR prevented hypercapnia with minimal auto-PEEP (difference of median intrinsic PEEP between the groups was < 1 cm H2O) • No difference in their supportive care requirements (vasopressors-IV fluidsfluid balance-diuretics-sedation) • ~10% mortality reduction • Less organ failures • Lower blood IL-6 and IL-8 levels ARDS Network. N Engl J Med. 2000. Parsons PE, et al. Crit Care Med. 2005. Hough CL, et al. Crit Care Med. 2005. Cheng IW, et al. Crit Care Med. 2005. Ventilator-induced Lung Injury Ventilator-induced Two primary mechanistic factors: • Overdistension of the alveoli by high transpulmonary pressures • Shear-stress forces produced by repetitive alveolar recruitment and derecruitment (collapse) - Atelectrauma In animal models, the repetitive cycle of alveolar collapse and rerecruitment has been associated with worsening lung injury. The extent of this injury has been reduced in animals through the use of PEEP levels that prevent derecruitment at end-expiration. VT ~ 6 ml/kg PEEP ~13-16 VT~12 ml/kg PEEP ~9 Significant prognostic factors responsible of the ventilatory treatment effect: • • • APACHE II score Mean PEEP during the first 36 hours (with a protective effect) Driving pressures (PPLAT - PEEP) during the first 36 hours Amato M, et al. N Engl J Med. 1998. PEEP in ARDS How much is enough ? PEEP by avoiding repetitive opening and collapse of atelectatic lung units, could be protective against VILI High PEEP should make the mechanical ventilation less dangerous than low PEEP. The recruitment is obtained essentially at end-inspiration, and the lung is kept open by using PEEP to avoid end-expiratory collapse. PEEP, by preserving inspiratory recruitment and reestablishing end-expiratory lung volume, has been shown to prevent surfactant loss in the airways and avoid surface film collapse. Levy MM. N Engl J Med. 2004. Rouby JJ, et al. Am J Respir Crit Care Med. 2002. Gattinoni L, et al. Curr Opin Crit Care. 2005. PEEP in ARDS PEEP How much is enough ? “Optimal PEEP”: Allowing for a given ARDS an optimization of arterial oxygenation without introducing a risk of oxygen toxicity and VILI, while having the least detrimental effect on hemodynamics, oxygen delivery, and airway pressures. There has never been a consensus regarding the optimum level of PEEP for a given patient with ARDS. The potential for recruitment may largely vary among the ALI/ARDS population. PEEP may increase PaO2 without any lung recruitment because of a decrease in and/or a different distribution of pulmonary perfusion. Levy MM. N Engl J Med. 2004. Rouby JJ, et al. Am J Respir Crit Care Med. 2002. Gattinoni L, et al. Curr Opin Crit Care. 2005. NIH-NHLBI ARDS Network: Hypothesis NIH-NHLBI In patients with ALI/ARDS (NAECC definitions) of < 36 hours who receive mechanical ventilation with a VT of 6 ml/kg of PBW, higher PEEP may improve clinical outcomes. NHLBI ARDS Clinical Trials Network. N Engl J Med. 2004. NIH-NHLBI ARDS Network NIH-NHLBI Patients with ALI/ARDS (NAECC definitions) of < 36 hours Ventilator procedures • • • • • • • Volume-assist-control mode Tidal-volume goal: 6 ml/kg of predicted body weight PBW Plateau pressure ≤ 30 cm H2O Ventilator rate setting 6 - 35 (breaths/min) to achieve a pH goal of 7.3 if possible I/E ratio:1.1 to 1.3 Oxygenation goal: PaO2 55 - 80 mmHg/SpO2 88 - 95% Allowable combination of FiO2 and PEEP: Low PEEP FiO2 PEEP High PEEP FiO2 PEEP 0.3 5 0.3 12 0.4 5 0.3 14 0.4 8 0.4 14 0.5 8 0.4 16 0.5 10 0.5 16 0.6 0.7 0.7 0.7 0.8 0.9 0.9 0.9 1.0 10 10 12 14 14 14 16 18 18-24 0.5 0.5-0.8 0.8 0.9 1.0 18 20 22 22 22-24 • The trial was stopped early after the second interim analysis (n = 549 on the basis of the specified futility stopping rule). NHLBI ARDS Clinical Trials Network. N Engl J Med. 2004. NIH-NHLBI ARDS Network FiO2-PEEP Step Comparison FiO 24 20 16 PEEP 12 8 4 0 0.3 0.4 0.5 0.6 0.7 0.8 FIO2 0.9 1.0 NIH-NHLBI ARDS Network Cause of Lung Injury Cause Sepsis 22% Trauma 8% Aspiration 15% Pneumonia 40% Other 10% NHLBI ARDS Clinical Trials Network. N Engl J Med. 2004. Transfusion 5% NIH-NHLBI ARDS Network NIH-NHLBI Clinical Outcomes 1.0 Probability Lower PEEP, overall survival Higher PEEP, overall survival Lower PEEP, discharge 0.5 0.0 0 Higher PEEP, discharge 10 20 30 40 50 Days after Randomization NHLBI ARDS Clinical Trials Network. N Engl J Med. 2004. 60 NIH-NHLBI ARDS Network Main Outcome Variables Main Outcome LowerHigher-PEEP p value PEEP group group Death before discharge home (%) Unadjusted Adjusted for difference in baseline covariance 24.9 27.5 27.5 25.1 0.48 0.47 Breathing without assistance by day 28 (%) 72.8 72.3 0.89 No. of ventilator-free days from day 1 to day 28 14.5 ± 10.5 13.8 ± 10.6 0.50 No. of days not spent in ICU from day 1 to day 28 12.2 ± 10.4 12.3 ± 10.3 0.83 10 11 0.51 16 ± 11 16 ± 11 0.82 Barotrauma (%) No. of days without failure of circulatory, coagulation, hepatic, and renal organs from day 1 to day 28 NHLBI ARDS Clinical Trials Network. N Engl J Med. 2004. NIH-NHLBI ARDS Network NIH-NHLBI Additional Findings In ALI and ARDS patients, higher PEEP strategy was associated with: • • • • • • • PaO2/FiO2 higher the first seven days post randomization Plateau pressure higher the first three days post randomization VT lower the first three days post randomization No difference in RR, PaCO2, or pH No difference in mortality rate No difference in organ failures or barotrauma No difference in IL-6, ICAM-1, surfactant protein-D NHLBI ARDS Clinical Trials Network. N Engl J Med. 2004. Why is higher PEEP not better in this study? in Beneficial effects of higher PEEP counteracted by adverse effects? Recruitment maneuvers are needed? “Lower PEEP” (or lower tidal volume) was sufficient to protect against injury from “atelectrauma” (ventilation at low endexpiratory volumes)? NHLBI ARDS Clinical Trials Network. N Engl J Med. 2004. Lung Recruitment Lung First and foremost performed to provide an arterial oxygen saturation of 90% or greater at an Fio2 of less than 60% Recruitment of nonaerated lung units (open-lung concept) but risk of regional lung overinflation is a highly controversial issue The ARDS Lungs The Increase in lung density from alveolar edema and inflammation that predominates in cephalic parts of the lungs Loss of aeration (lung collapse) that predominates in caudal and dependent lung regions in patients lying supine • • • • External compression of caudal parts of the lungs by an enlarged heart (myocardial edema, hyperdynamic profile, and pulmonary hypertension-induced right ventricular dilatation) High pressure exerted by the abdominal content Accumulation of fluid in the pleural space Own increased weight (gravitation forces-weight of the edematous lung) Consolidated alveoli - Alveolar flooding: Fluid-filled alveoli (edema fluid or inflammatory cells) that predominates in caudal and dependent lung regions in patients lying supine The ARDS Lungs Vt External forces applied on the lower lobes at end inspiration and end expiration in a patient in the supine position and mechanically ventilated with positive end-expiratory pressure. aerated lung • Large blue arrows: Forces resulting from tidal ventilation Vt • Small blue arrows: Forces resulting from consolidated lung positive end-expiratory pressure (PEEP) • Green arrows: forces exerted by the abdominal content and the heart on the lung PEEP Rouby JJ, et al. Anesthesiology. 2004. The ARDS Lungs The ARDS Focal Patchy Diffuse Chest x-ray (zero PEEP) Focal heterogeneous loss of aeration in caudal and dependent lung region Bilateral and diffuse xray densities respecting lung apices Bilateral and diffuse hyperdensities “White lungs” Chest CT scan (zero PEEP) Loss of aeration Upper lobes normally aerated despite a regional excess of lung tissue – Lower lobes poorly or non aerated Lower lobes massively nonaerated – The loss of aeration involves partially the upper lobes Massive, diffuse and bilateral non- or poorly aerated lung regions – No normally aerated lung region Response to PEEP ± PEEP <10-12 cmH2O Risk of overinflation of the aerated lung regions ++++ Recruitment of non aerated lung unit Low potential for recruitment Rouby JJ, et al. Eur Respir J. 2003. Rouby JJ, et al. Anesthesiology. 2004. ++++ Lung recruitment curve Open lung concept ± High potential for recruitment The ARDS Lungs The Early phases of ARDS Direct insult of the lung Primary pulmonary ARDS “Indirect” insult of the lung Secondary extrapulmonary ARDS Pathologic changes Lung tissue consolidation Severe intra-alveolar damage (Edema, fibrin, collagen neutrophil aggregates, red cells) Microvascular congestion Interstitial edema Alveolar collapse Less severe alveolar damage End-expiratory lung volume EELV ↓↓↓ ↓↓↓ Static elastance of the total respiratory system Est,rs ↑↑↑↑ ↑↑↑↑ Static elastance of the chest wall Est,w / Static lung elastance Est,L ↑ / ↑↑↑ ↑↑ / ↑↑ Intra-abdominal pressure ↑ ↑↑↑ Response to PEEP Est,rs ↑↑↑ [Est,L >> Est,w] Stretching phenomena Est,rs ↓↓↓ [Est,L ≈ Est,w] Recruitment of previously closed alveolar spaces Lung recruitment ± ++++ Gattinoni L, et al. Am J Respir Crit Care Med. 1998. Respiratory Pressure/Volume (P/V) Curve Respiratory Healthy subject In normal healthy volunteers, the P/V curve explore the mechanical properties of the respiratory system (lung + chest wall) ARDS RV, Residual volume; FRC, Functional residual capacity; TLC, Total lung capacity; UIP, Upper inflection point; LIP, Lower inflection point. The critical opening pressure above which most of the collapsed units open up and may be recruited - CLIN Compliance of the intermediate, linear segment of the P/V curve Maggiore SS, et al. Eur Respir J. 2003. Rouby JJ, et al. Eur Respir J. 2003. Reinterpreting the Pressure/Volume Curve in ARDS Curve Measurement of the P/V curve in any given patient is not practical clinically. A single inflation P/V curve probably does not provide useful information to determine safe ventilator settings in ALI. The P/V curve for the whole lung is a composite of multiple regional P/V curves (considerable variation from the dependent to the nondependent lung; LIP from 50 to 30 cmH2O respectively). Kunst PW et al., Crit Care Med 2000 Recruitment Maneuvers (RMs) Recruitment Proposed for improving arterial oxygenation and enhancing alveolar recruitment All consisting of short-lasting increases in intrathoracic pressures • Vital capacity maneuver (inflation of the lungs up to 40 cm H 2O, maintained for 15 - 26 seconds) (Rothen HU. BJA. 1999; BJA 1993.) • Intermittent sighs (Pelosi P. Am J Respir Crit Care Med. 2003.) • Extended sighs (Lim CM. Crit Care Med. 2001.) • Intermittent increase of PEEP (Foti G. Intensive Care Med. 2000.) • Continuous positive airway pressure (CPAP) (Lapinsky SE. Intensive Care Med. 1999. Amato MB. N Engl J Med. 1998.) • Increasing the ventilatory pressures to a plateau pressure of 50 cm H 2O for 12 minutes (Marini JJ. Crit Care Med. 2004. Maggiore SM. Am J Respir Crit Care Med. 2003.) Lapinsky SE and Mehta S, Critical Care 2005 Recruitment Maneuvers (RMs) Recruitment Effective in improving arterial oxygenation only at low PEEP and small tidal volumes. When alveolar recruitment is optimized by increasing PEEP, recruitment maneuvers are either poorly effective or deleterious, inducing overinflation of the most compliant regions, hemodynamic instability, and an increase in pulmonary shunt resulting from the redistribution of pulmonary blood flow toward nonaerated lung regions. The effect of recruitment may not be sustained unless adequate PEEP is applied to prevent derecruitment. Many questions still need to be answered: • • • • • Optimal time to perform RMs (First hours after endotracheal intubation, early phase of ARDS, after endotracheal suctioning) How often they should be used Their durations The recommended ventilatory mode (CPAP, sighs, pressure controlled ventilation, short duration high PEEP level) The long-lasting effects of RMs on ABGs are contradictory. High-frequency Oscillatory Ventilation High-frequency Characterized by rapid oscillations of a reciprocating diaphragm, leading to high-respiratory cycle frequencies, usually between 3 and 9 Hz in adults, and very low VT. Ventilation in HFOV is primarily achieved by oscillations of the air around the set mean airway pressure mPaw. HFOV is conceptually very attractive, as it achieves many of the goal of lung-protective ventilation. • Constant mPaws: Maintains an “open lung” and optimizes lung recruitment • Lower VT than those achieved with controlled ventilation (CV), thus theoretically avoiding alveolar distension. • Expiration is active during HFOV: Prevents gas trapping • Higher mPaws (compared to CV): Leads to higher end-expiratory lung volumes and recruitment, then theoretically to improvements in oxygenation and, in turn, a reduction of FiO2. Chan KPW and Stewart TE, Crit Care Med 2005 High-frequency Oscillatory Ventilation High-frequency Observational studies have demonstrated that HFOV may improve oxygenation when used as a rescue modality in adult patients with severe ARDS failing CV. Preliminary data suggest that there may be a survival advantage. HFOV may be considered for patients with severe ARDS: • • • • FiO2 > 0.60 and/or SpO2 < 88% on CV with PEEP > 15 cm H2O, or Plateau pressures (Pplat) > 30 cmH2O, or Mean airway pressure ≥ 24 cm H2O, or Airway pressure release ventilation Phigh ≥ 35 cm H2O “Team approach” (attending physician, respiratory care team leader, respiratory care area manager, critical care nurse, ICU respiratory therapist) HFOV for adults with ARDS is still in its infancy and requires further evaluations. Higgins J et al., Crit Care Med 2005 Non-ventilatory-based Strategies in the Management of ARDS/ALI in Fluid and hemodynamic management Inhaled nitric oxide Prone position ventilation Steroids Other drug therapy Fluid and Hemodynamic Management Fluid Starling Equation Qf = Kf [(Pc- PIF) – s(pc – pIF)] - Kf capillary filtration coefficient - PIF interstitial hydrostatic pressure - pc capillary colloid osmotic pressure - Pc capillary hydrostatic pressure - s oncotic reflection coefficient - pIF interstitial colloid oncotic pressure Pathophysiology: • Increases in capillary hydrostatic pressure • Increased membrane permeability • Diminished oncotic pressure gradiant Clinical implications: • Reductions in pulmonary capillary hydrostatic pressure/pulmonary artery occlusion pressure – CVP • Hemodynamic monitoring to avoid tissue hypoperfusion • Fluid restriction/negative fluid balance • Diuretics • Combination therapy with colloids and furosemide? Lewis CA and Martin GS, Curr Opin Crit Care 2004 Klein Y, J Trauma 2004 Inhaled Nitric Oxide Inhaled Physiology of inhaled nitric oxide therapy • Selective pulmonary vasodilatation (decreases arterial and venous resistances) • Decreases pulmonary capillary pressure • Selective vasodilatation of ventilated lung areas • Bronchodilator action • Inhibition of neutrophil adhesion • Protects against tissue injury by neutrophil oxidants Steudel W, et al. Anesthesiology. 1999. Effects of Inhaled Nitric Oxide in Patients with Acute Respiratory Distress Syndrome: Results of a Randomized Phase II Trial Results In patients with documented ARDS, iNO at 1.25, 5, 20, 40, or 80 ppm: • Is associated with a significant improvement in oxygenation compared with placebo over the first four hours of treatment. An improvement in oxygenation index was observed over the first four days. • Acutely increased the PaO2 in 60% of the patients • The percentage of patients having an acute increase in PaO 2 and the magnitude of the change were similar in each of the inhaled NO dose groups. • Appears to be well tolerated in doses between 1.25 to 40 ppm. • Although these concentrations appear to be safe, it would be prudent to more closely monitor NO2 concentrations, and methemoglobin. • There are trends in decreasing the intensity of mechanical ventilation needed to maintain adequate oxygenation and improved patient benefit at 5 ppm inhaled NO. Dellinger RP et al., Crit Care Med 1998 Low-dose Inhaled Nitric Oxide in Patients with Acute Lung Injury: A Randomized Controlled Trial Randomized In patients with documented ARDS and severe acute lung injury (PaO2/FiO2 ≤ 250) but without sepsis or other organ system failure, iNO at 5 ppm: • Induces short-term improvements in oxygenation with a 20% increase in PaO2 that were maintained only during 24 - 48 hours. • Does not improve clinical outcomes or mortality These data do not support the routine use of inhaled nitric oxide in the treatment of acute lung injury or ARDS. Inhaled nitric oxide may be considered (Grade C recommendation) as a salvage therapy in acute lung injury or ARDS patients who continue to have life threatening hypoxemia despite optimization of conventional mechanical ventilator support. Taylor RW, et al. JAMA. 2004. Prone Positioning Prone Limits the expansion of cephalic and parasternal lung regions Relieves the cardia and abdominal compression exerted on the lower lobes Makes regional ventilation/perfusion ratios and chest elastance more uniform Facilitates drainage of secretions Potentiates the beneficial effect of recruitment maneuvers Prone Positioning Prone Absolute contraindications • • • • • Burns or open wounds on the face or ventral body surface Spinal instability Pelvic fractures Life-threatening circulatory shock Increased intracranial pressure Main complications • Facial and periorbital edema • Pressure sores • Accidental loss-displacement of the endotracheal tube, thoracic or abdominal drains, and central venous catheters • Airway obstruction • Hypotension • Arrythmias • Vomiting Prone Positioning Prone Improves arterial oxygenation in more than 70% of patients in early stage of ARDS (a decrease in FiO2 ≥ 20% is expected) No baseline features that differentiate between responders and non responders are known. After the patient back to the supine position, the oxygenation might return to the basal supine value, or remain elevated Does not increase survival at the end of the 10-day study period, at the time of discharge from the ICU, or at six months However in the most severely ill and hypoxemic patients with a Pao2/Fio2 ≤ 88 mmHg, a, SAPS II > 49, a high tidal volume > 12 ml/kg of PBW, or all three, it may reduce mortality and limit VILI. The optimum daily duration is not known. In clinical practice, the duration ranges between six and 12 hours/day. The optimum total duration and number of pronations depends on the effects on arterial oxygenation of supine repositioning Gattinoni L et al., N Engl J Med 2001 Slutsky AS. N Engl J Med 2001 Effect of Prone Positioning on the Survival of Patients with Acute Respiratory Failure of Enrollment: • Oxygenation criteria Pao2/Fio2 ≤ 200 with a PEEP ≥ 5 cm H2O Pao2/Fio2 ≤ 300 with a PEEP ≥ 10 cm H2O • Radiographic criteria Bilateral pulmonary infiltrates • Pulmonary-capillary wedge pressure ≤ 18 mm Hg or the absence of clinical evidence of left atrial hypertension. Treatment protocol: After randomization, prone group patients were continuously kept prone for at least six hours per day for period of 10 days. Gattinoni L, et al. N Engl J Med. 2001. a Effect of Prone Positioning on the Survival of Patients with Acute Respiratory Failure of Kaplan-Meier estimates of survival at six months Gattinoni L, et al. N Engl J Med. 2001. Effect of Prolonged Methylprednisolone in Unresolving ARDS in Rationale: Within seven days of the onset of ARDS, many patients exhibit a new phase of their disease marked by fibrotic lung disease or fibrosing alveolitis with alveolar collagen and fibronectin accumulation. Patient selection: Severe ARDS/ ≥ 7 days of mechanical ventilation with an LIS ≥ 2.5/No evidence of untreated infection Treatment protocol: Methylprednisolone • • • • • • Loading dose 2 mg/kg 2 mg/kg/24 hours from day 1 to day 14 1 mg/kg/24 hours from day 15 to day 21 0.5 mg/kg/24 hours from day 22 to day 28 0.25 mg/kg/24 hours on days 29 and 30 0.125 mg/kg/24 hours on day 31 and 32 In patients with unresolving ARDS, prolonged administration of methylprednisolone was associated with improvement in lung injury and MODS scores and reduced mortality. Meduri GU et al., JAMA 1998 Meduri JAMA Corticosteroid Therapy in ARDS: Corticosteroid Better late than never? High-dose corticosteroids in early ARDS • • • • Do not lessen the incidence of ARDS among patients at high risk Do not reverse lung injury in patients with early ARDS/worse recovery Have no effect on mortality/even increase mortality rate Significantly increase the incidence of infectious complications High-dose corticosteroids for unresolving ARDS of ≥ 7 days duration who do not have uncontrolled infection • There are several challenges associated with the interpretation of this trial. A large clinical trial is needed to clearly demonstrate a survival advantage that outweighs the potential risks. • Patient selection: Lack of clinical improvement rather than use of only the LIS • Aggressive search for and treatment of infectious complications is necessary. • Several questions remain: Timing, dosage, and duration of late steroid therapy in ARDS/Appropriate time window for corticosteroid administration, between early acute injury and established postagressive fibrosis. Kopp R et al., Intensive Care Med 2002 Brun-Buisson C and Brochard L, JAMA 1998 Other Drug Therapy Other Prostaglandin E1 (PGE1) (pulmonary vasodilatation and antiinflammatory effects on neutrophils/macrophages) Aerosolized prostacyclin (PGI2) (selective pulmonary vasodilatation of ventilated lung areas) Almitrine (selective pulmonary vasoconstrictor of nonventilated lung areas) Surfactant (prevents alveolar collapse and protects against intrapulmonary injury and infection) Antioxidants (protect the lung from free oxygen radical production) Partial liquid ventilation (recruitment of collapsed areas and antiinflammatory effect) Anti-inflammatory drugs (Ibuprofen - ketoconazole) No recommendation can be made for their use - Rescue modality in the patient with refractory hypoxia? Combination of different therapeutic approaches? therapeutic Combination of iNO and prone position (Papazian L, et al. Crit Care Med. 1998.) Combination of iNO and almitrine (Gallart L, et al. Am J Respir Crit Care Med. 1998.) Combination of prone position, iNO, and almitrine (Jolliet P, et al. Crit Care Med. 1997. Gillart T, et al. Can J Anaesth. 1998.) Combination of iNO and iv prostacycline (Kuhlen R, et al. Intensive Care Med. 1999.) Conclusions Conclusions Search for ventilatory “lung protective” strategies Positive pressure ventilation may injure the lung via several different mechanisms Alveolar distension “VOLUTRAUMA” Repeated closing and opening of collapsed alveolar units “ATELECTRAUMA” Lung inflammation “BIOTRAUMA” VILI Multiple organ dysfunction syndrome Oxygen toxicity Recommendations in Practice Recommendations Principle of precaution Limited VT 6 mL/kg PBW to avoid alveolar distension End-inspiratory plateau pressure < 30 - 32 cm H 2O Adequate end-expiratory lung volumes utilizing PEEP and higher mean airway pressures to minimize atelectrauma and improve oxygenation Consider recruitment maneuvers Avoid oxygen toxicity: FiO2 < 0.7 whenever possible Monitor hemodynamics, mechanics, and gas exchange Address deficits of intravascular volume Prioritize patient comfort and safety VILI: Remaining Questions Optimal tidal volume, Pplat, PEEP Role of recruitment maneuvers High-frequency ventilation Permissive hypercapnia Prone positioning ...
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Acute_Lung_Injury_ARDS_-_FINAL2 - Acute Lung Injury and...

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