bài giảng dành cho sinh viên y khoa, bác sĩ, sau đại học , ĐH Y DƯỢC TP HCM
ARDS Acute respiratory distress syndrome • Shock lung • Da Nang Lung • Traumatic wet lung ĐỊNH NGHĨA Acute lung injury — Acute lung injury (ALI) • Acute onset • Bilateral infiltrates consistent with pulmonary edema • A ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen (PaO2/FiO2) 201 and 300 mmHg, regardless of the level of positive end-expiratory pressure (PEEP) The PaO2 is measured in mmHg and the FiO2 is expressed as a decimal between 0.21 and 1.00 • No clinical evidence for an elevated left atrial pressure If measured, the pulmonary capillary wedge pressure is 18 mmHg or less Definitions - Acute respiratory distress syndrome — The definition of ARDS is the same as ALI except that the hypoxemia is worse (PaO2/FiO2 ≤ 200 mmHg), regardless of the level of PEEP PaO2/FiO2 versus SpO2/FiO2 - To address this issue, use of the pulse oximetric saturation (SpO2)/FiO2 ratio as a substitute was studied • SpO2/FiO2 ratio of 235 PaO2/FiO2 ratio of 200 • SpO2/FiO2 ratio of 315 PaO2/FiO2 ratio of 300 • SpO2/FiO2 ratio of 201 PaO2/FiO2 ratio of 200, SpO2/FiO2 ratio of 263 PaO2/FiO2 ratio of 300 - These findings suggest that the SpO2/FiO2 ratio may be helpful when arterial blood cannot be obtained, although the PaO2/FiO2 ratio is preferred when available Clinical Disorders Associated with the Development of ALI/ARDS Direct insult Common Indirect insult Common Aspiration pneumonia Pneumonia Sepsis Severe trauma Shock Less common Inhalation injury Pulmonary contusions Fat emboli Near drowning Reperfusion injury 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 The Problem: Lung Injury Davis et al., J Peds 1993;123:35 Noninfectious Pneumonia 14% Cardiac Arrest 12% Infectious Pneumonia 28% Trauma 5% Septic Syndrome 32% Etiology In Children Transfusion-related lung injury (TRALI) - ALI occurring during or within six hours after a transfusion • Anti-granulocyte antibodies • Granulocyte Priming: his theory contends that biologically active substances, such as lipids and cytokines contained within the transfusions, have the ability to prime the activity of granulocytes in the pulmonary vasculature, contributing to increased vascular permeability • Two event hypothesis Other Drug Therapy Prostaglandin E1 (PGE1) (pulmonary vasodilatation inflammatory effects on neutrophils/macrophages) and anti- Aerosolized prostacyclin (PGI2) (selective pulmonary vasodilatation of ventilated lung areas) Almitrine (selective pulmonary vasoconstrictor of nonventilated lung areas) Surfactant (prevents alveolar collapse intrapulmonary injury and infection) and protects against 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? Prone Positioning in ARDS Prone Positioning in ARDS - Theory: let gravity improve matching perfusion to better ventilated areas - Improvement immediate - Uncertain effect on outcome Prone Positioning in Adult ARDS - Randomized trial - Standard therapy vs standard + prone positioning - Improved oxygenation - No difference in mortality, time on ventilator, complications Gattinoni et al., NEJM, 2001 Prone Positioning Limits the expansion of cephalic and parasternal lung regions Relieves the cardia and abdominal compression exerted on the lower lobes Makes regional ventilation/perfusion elastance more uniform ratios and chest Facilitates drainage of secretions Potentiates the beneficial effect of recruitment maneuvers Prone Positioning Absolute contraindications Burns or open wounds on the face or ventral body surface Spinal instability Pelvic fractures Life-threatening circulatory shock Increased intracranial pressure Prone Positioning 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 - Corticosteroids have not been proven to increase survival among all patients with fibroproliferative ARDS However, the effect of corticosteroids may be related to the duration of disease prior to the initiation of therapy and the dose used - Additional studies are necessary to determine whether there is a role for corticosteroids in the management of ARDS Pharmacologic Approaches to ARDS: Randomized Trials Glucocorticoids - acute - no benefit - fibrosing alveolitis - lowered mortality, small study Surfactant - possible benefit in children Inhaled NO - no benefit Partial liquid ventilation - no benefit Recommendations in Practice Principle of precaution Limited VT mL/kg PBW to avoid alveolar distension End-inspiratory plateau pressure < 30 - 32 cm H2O Adequte 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 BROCHARD & BROWER & STEWART & AMATO 1.1 CUMMULATIVE SURVIVAL 1.0 P < 0.0001 PPLAT < 23 23 27 27 33 PPLAT > 33 n = 341 ( Adjusted for APACHE & pH & PEEP ) 0.0 10 20 30 40 DAYS AFTER ENTRY 50 60 BROCHARD & BROWER & STEWART & AMATO RELATIVE RISK OF DEATH 15 20 25 30 35 PLATEAU PRESSURES (cmH2O) 40 45 Thank you! ... theory contends that biologically active substances, such as lipids and cytokines contained within the transfusions, have the ability to prime the activity of granulocytes in the pulmonary vasculature,... lung compliance - Pulmonary hypertension ARDS exudative and fibrotic phases PROGNOSIS - death during the initial three days was usually due to the underlying cause of the ARDS [63] - Later, most... increased vascular permeability • Two event hypothesis ARDS mechanism of lung injury - Activation of inflammatory mediators and cellular components resulting in damage to capillary endothelial and alveolar