ARDS: Case Presentation for Mr. James

• Acute Respiratory Distress Syndrome (ARDS) is the topic.

Case Presentation of Mr. James

• Mr. James, a 40-year-old male, arrives at the ER with fever, cough, and and shortness of breath.
• He denies any sick contacts and recent travel history.
• He has no prior hospital admissions.
• Symptoms started 3 days prior.
• Shortness of breath is worsening, especially on exertion.
• Mr. James is a non-smoker working in a marketing company.
• Patient complains of feeling very tired and low energy.
• He is taking OTC acetaminophen and cough suppressant with no improvement.
• Vital signs: HR 110, BP 90/60, RR 30/min, T° 39°C, Sat 89% on room air.
• Patient appears confused.
• Accessory muscle use and coarse crackles noted in the right mid-lung zone.
• Low JVP with normal heart sounds and no murmurs.
• No pedal edema and normal extremities.
• CBC results include: Hgb 135g/L, WBC 13, Plt 210, Na 140, Cl 101, HCO3 24, K 4.5, Cr 95.
• Arterial Blood Gas (ABG) results: pH 7.45, PaO2 58mmHg, PaCO2mmHg 35, HCO3 24mEq/L.
• Further tests ordered: blood, urine, sputum cultures, and NP swab to look for bacterial and viral infection.
• CXR shows RML pneumonia taken 3 hours prior.
• Patient is started on Ceftriaxone and Azithromycin for community-acquired pneumonia.
• Admitted to the hospital based on a Community-Acquired Pneumonia CRB-65 score of 3.
• After a few hours, the nurse calls to report the patient is getting worse with RR of 40 and Sats of 90% on 100% FiO2.
• Patient is intubated for presumed Acute Respiratory Distress Syndrome.

Assessing an Unstable Patient

• Assess the patient's airway to ensure it is patent and without obstruction.
• Assess the patient's breathing to determine spontaneous breathing and hypoxia.
• Assess the patient's circulation to check for a pulse and hypotension.

The Berlin Definition of ARDS

• Timing: Within 1 week of a known clinical insult of new/worsening respiratory symptoms.
• Chest Imaging: Bilateral opacities not fully explained by effusions, lobar/lung collapse, or nodules on chest x-ray or CT scan.
• Origin of Edema: Respiratory failure not fully explained by cardiac failure or fluid overload. Objective assessments such as echocardiography should exclude hydrostatic edema if no risk factor present.
• Mild: 200 < PaO2/FiO2 ≤ 300 with PEEP or CPAP ≥ 5cmH2O. Non-invasive delivery possible here.
• Moderate: 100 < PaO2/FiO2 ≤ 200 with PEEP ≥ 5 cmH2O.
• Severe: PaO2/FiO2 ≤ 100 with PEEP ≥ 5 cmH2O.
• For altitude >1000 m, correction calculation: PaO2/FiO2 × (barometric pressure/760)

Common Causes of ARDS

• Parenchymal: Pneumonia, aspiration, trauma to the chest (contusions), transfusion, drowning.
• Extra-parenchymal: Sepsis, pancreatitis, drugs-induced ARDS, nitrofurantoin, bleomycin, extra-thoracic trauma.

Physiological Abnormalities in ARDS

• Impaired Gas Exchange: V/Q mismatch, physiological shunt, increased dead space.
• Pulmonary Hypertension: Hypoxic vasoconstriction, vascular compression, and airway collapse.
• Decreased Lung Compliance: More stiffness from non-aerated lung.

Management of ARDS

• Principles: Restore "normal" physiology, adjust ventilation to achieve "normal" blood gases.
• Ventilator-associated lung injury (VALI) Includes: Gross barotrauma (e.g., pneumothorax). It is uncommon, easy to detect, and treat (e.g., chest tube drainage)
• Ventilator-associated lung injury (VALI): Prevent barotrauma, volutrauma, atelectrauma and biotrauma.
• Prevent over-distension, prevent under-inflation and open the lung when possible.
• Prevent oxygen toxicity.
• Titrate to Sats >88%
• Administer analgesia, sedation, and paralysis.
• Decrease metabolism and O₂-consumption of respiratory muscles.
• Treat fever, anxiety, and pain facilitate.
• Facilitate safe ventilation to prevent lung injury.

Managing Unstable and Hypoxic Patients

• Always call for help.
• Remember ABC's: Airway, Breathing, Circulation.
• Monitor and get investigations like CXR and ABG in addition to routine bloodwork.
• Sedation and Paralysis, Lung-protective ventilation, and Minimize pressure to avoid further injury.
• Use FiO2, Recruitment Maneuvers ad PEEP to improve V/Q matching and shunt, increasing O2.
• Consider proning.

Diagnostic Criteria of ARDS

• Respiratory symptoms beginning within 1 week of a known clinical insult.
• Bilateral opacities on chest X-ray or CT scan, consistent with pulmonary edema.
• Respiratory failure not solely due to cardiac failure or fluid overload
• Impaired oxygenation with PaO2/FiO2 ratio <300 with a PEEP >5cm H₂O.