ACUTE RESPIRATORY DISTRESS SYNDROME Flashcards
Define acute respiratory distress syndrome (ARDS).
A severe, life-threatening medical condition characterized by a build up of fluid in the lungs leading to severe hypoxia and potentially atelectasis (collapsed lung). It is associated with pulmonary cytokine release, impaired endothelial barriers, loss of surfactant, and fibrotic changes.
What are some causes of ARDS? (Name 5)
Septic shock Hypovolemic shock Trauma Pneumonia Diabetic ketoacidosis Aspiration of vomit Lung transplant Drugs such as heroine, paraquat and aspirin Pregnancy Eclampsia Amniotic fluid embolus Acute liver failure Pancreatitis Malaria
What is the pathophysiology that underlies ARDS?
The triggering insult to the parenchyma usually results in an initial release of cytokines and other inflammatory mediators secreted by local epithelial and endothelial cells. Neutrophils and some T-lymphocytes quickly migrate into the inflamed lung parenchyma and contribute in the amplification of the phenomenon. The inflammation causes endothelial dysfunction, fluid extravasation from the capillaries and impaired drainage of fluid from the lungs. Dysfunction of type II pulmonary epithelial cells may also be present, with a concomitant reduction in surfactant production. Oedema and decreased surfactant production by type II pneumocytes may cause whole alveoli to collapse or to completely flood.
What are the criteria that must be met when diagnosing ARDS in a patient?
Lung injury of acute onset, within 1 week of an apparent clinical insult and with progression of respiratory symptoms
Bilateral opacities on chest imaging not explained by other pulmonary pathology (e.g. pleural effusion, pneumothorax, or nodules)
Respiratory failure not explained by heart failure or volume overload.
Decreased arterial PaO2/FiO2 ratio.
What measurement can be used to determine severity of ARDS? What are the different cut-offs?
PaO2/FiO2 ratio
Mild ARDS: 201 - 300 mmHg (≤ 39.9 kPa)
Moderate ARDS: 101 - 200 mmHg (≤ 26.6 kPa)
Severe ARDS: ≤ 100 mmHg (≤ 13.3 kPa)
What examples of trauma can lead to the development of ARDS?
Near drowning experience
Burns
Inhalation of smoke
Inhalation of other chemicals (some chemical warfare agents such as chlorine gas)
How would someone with suspected ARDS usually present? (Name 5 signs and symptoms)
History of recent trauma or infection Shortness of breath Increased breathing rate Low oxygen sats Low blood pressure Signs of organ failure Tachycardia Peripheral vasodilatation Fine inspiratory crackles Cyanosis
What tests would be needed to confirm a diagnosis of ARDS and find the underlying cause?
Arterial blood gas Blood tests, including FBC, U&E, LFT, CRP, amylase, clotting Blood and urine cultures Bronchoscopy Chest x-ray Sputum cultures and analysis
An echocardiogram is also needed to rule out congestive heart failure.
How would someone with ARDS be treated?
ARDS often needs to be treated in an intensive care unit (ICU).
The goal of treatment is to provide breathing support and treat the cause of ARDS. This may involve drugs to treat infections, reduce inflammation, and remove fluid from the lungs.
A ventilator is used to deliver high doses of oxygen and continued pressure (positive end-expiratory pressure, or PEEP) to the damaged lungs. Most patients need mechanical ventilation for which they need to be deeply sedated with medicines. During treatment, doctors and nurses make every effort to protect the lungs from further damage.
What is the mortality of ARDS?
50-70%
Prognosis depends on factors such as age and underlying cause of ARDS
Trauma - 38%
Pneumonia - 86%
