ARDS UPDATE

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ARDS UPDATE : 

ARDS UPDATE MAGED ABULMAGD,MD critical care medicine, Cairo university EDIC ESICM member

The Inexact Definition for ARDS : 

The Inexact Definition for ARDS Contributes to difficulty in management ARDS and ALI consensus statement definitions Acute onset (not specified) Po2/FiO2 ratio <200 (300 for ALI) Bilateral infiltrates on chest radiograph (highly variable) PAWP<18 mm Hg or absence of clinical evidence of volume overload Bernard GR et al, Am J Resp Crit Care Med. 1994;149:818-824

Slide 6: 

Mediators Bacterial products Reactive oxygen intermediates Proinflammatory cytokines Activated neutrophils, macrophages, epithelium, endothelium, and platelets. Complements

Causes of Mortality in ARDS : 

Causes of Mortality in ARDS 1990

Slide 14: 

Depiction of the pathologic phases of acute lung injury/acute respiratory distress syndrome.

Pulmonary manifestations : 

Pulmonary manifestations Cyanosis due to hypoxemia Tachypnoea Dyspnoea due to work of breathing High-pitched crackles

etiology : 

etiology A direct (primary or pulmonary) injury to the lungs ----- 70-80%. An indirect (secondary or extra pulmonary) injury caused by systemic inflammation.

Slide 19: 

mortality closely related to number of organ systems involved; 15-30% for lung alone > 80% for three or more organs.

Diagnosis : 

Diagnosis medical history chest radiograph exclude LVF PaO2/FiO2 ratio low lung compliance

Slide 25: 

Bacteriological airway cultures should be taken when there is unexplained fever, increased sputum, new infiltrates on the chest radiograph or unexplained deterioration in oxygenation.

Slide 26: 

1. Lowering tidal volume to 6 ml/kg/PBW in a newly diagnosed ARDS patient 2. Use of steroids to treat fibroproliferation on day 5 of ARDS 3. Prone positioning in a patient with an arterial oxygen saturation of 89% and an FiO2 of 1.0 with a PEEP of 22 cm Hg 4. Insertion of a pulmonary artery catheter to guide therapy choice for the treatment of ARDS? Which one of the following has the least support for a management choice for the treatment of ARDS?

Slide 27: 

Infection and infection therapy After specimens for bacterial cultures have been taken, antibiotics should be given urgently when the cause of ARF is of infectious origin. Inappropriate and delayed antibiotic therapy is associated with increased mortality.

lung protective ventilatory strategy : 

lung protective ventilatory strategy The goal for ventilatory therapy in ARF is to provide an adequate gas exchange (usually PaO2 >60 mmHg, SaO2 >90% and pH 7.2-7.4) without causing additional iatrogenic damage to lungs and other organs.

Slide 30: 

861 patients with ALI and ARDS multicenter, randomized trial Tidal volume : 6 ml/kg vs 12 ml/kg Result : Mortality rate:31.0% vs 39.8% ( P=0.007) The number of days without ventilator use the first 28 days (mean 12 ±11 vs 10 ±11 ( P=0.007)

Recruitment : 

Recruitment The purpose is to apply an airway pressure high enough to open up major parts of the collapsed lung. However, it is not the airway pressure itself that is important but the transpulmonary pressure (airway pressure - pleural pressure).

Recruitment : 

Recruitment Among many different lung recruitment manoeuvres, none of them has been proven to be superior. The principle is to apply a high sustained airway pressure to open up collapsed parts of the lungs and then PEEP to prevent re-collapse.

Slide 34: 

An idealized and simplified depiction of the pressure volume curve of the injured lung during inflation, with the state of alveolar collapse and inflation.

Continuous positive airways pressure method : 

Continuous positive airways pressure method The ventilator mode is changed to continuous positive airways pressure (CPAP) and the pressure is increased to 45-55 cm H2O which is maintained for 20-30 sec after which the patient is ventilated with the normal settings and a PEEP of 18-20 cm H2O.

The ‘Lachmann’ method : 

The ‘Lachmann’ method The setting of the ventilator is changed to pressure control, I:E 1:1, rate 8-10/min, PEEP 20 cm H2O and the peak inspiratory pressure is slowly increased to 50-55 cm H2O. This type of ventilation is continued for about 2 min, after which the total inspiratory pressure is lowered to 30-35 cm H2O.

PEEP : 

The ideal level of PEEP is that which prevents derecruitment of the majority of alveoli, while causing minimal overdistension PEEP

PEEP : 

PEEP PEEP does not recruit collapsed lung alveoli, but may prevent the re-opened parts of the lungs from de-recruitment. Therefore, PEEP should ideally be set at a high level (about 18-20 cm H2O) immediately after a lung recruitment manoeuvre.

Complications from ventilatory support : 

Complications from ventilatory support Haemodynamic compromise  Infections including nosocomial pneumonia  Pressure and volume induced lung and organ injuries

Prone position : 

Prone position Pleural pressure is more homogenously distributed.  Oxygenation increases in 70% (60-95%) of patients . The response is more favourable in patients with extra-pulmonary ARDS.

Prone position : 

Prone position complications such as inadvertent removal of the endotracheal tube and intravascular catheters, nerve injuries and pressure sores on the forehead, eyes, thighs and chest regions might occur.

Pharmacological therapies : 

Pharmacological therapies Anti-inflammatory agents, antioxidants, immunotherapy for improving oxygenation have been tried. Prostaglandins, N-acetylcysteine, ketoconazole, ibuprofen, pentoxifylline, anti-endotoxin, inhaled nitric oxide (iNO), inhaled prostacyclin, almitrine, surfactant and corticosteroids have all been tried.

Pulmonary vasoactive drugs : 

Pulmonary vasoactive drugs Inhaled NO and inhaled prostacyclin act as selective pulmonary vasodilators.  Inhaled NO improves oxygenation in 60-70% of patients but with a limited duration of action. additive effects on oxygenation with combinations of inhaled NO, inhaled prostacyclin, and prone position.

Steroids : 

Steroids The use of smaller doses of steroids for an extended period has been proposed in the late phase of ARDS after day seven of mechanical ventilation. Further trials might answer whether steroids in this phase of ARDS are of clear benefit.

Are there any conditions with ARDS when steroids are indicated ? : 

Are there any conditions with ARDS when steroids are indicated ? ARDS secondary to pneumocystis carinii pneumonia, tuberculosis, vasculitis and bronchiolitis obliterans obstructing pneumonia (BOOP).

Surfactant : 

Surfactant In ARDS, surfactant function is inhibited and therefore surfactant therapy has been proposed. By administration of surfactant in aerosol or by intratracheal instillation, oxygenation and lung mechanics usually improve. Two randomised human trials have shown different results on outcome.

Fluid and nutritional support : 

Fluid and nutritional support A negative fluid balance without compromising tissue perfusion might improve oxygenation and outcome. Compared to cardiac patients, fluid removal is more resistant and takes longer time.

Haemodynamics : 

Haemodynamics The filling pressures may be elevated and may not reliably indicate the volume status of the heart. Administration of i.v. fluids is usually enough to counteract the influence on the cardiac filling by the positive airway pressure.

Haemodynamics : 

Haemodynamics The mean airway pressure is probably more important than PEEP or the peak airway pressure. The intermittent decrease in venous filling caused by the positive intrathoracic pressure produces a variation in systemic arterial pressure.

Slide 54: 

Thank you

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