Acute respiratory distress syndrome resident survival guide

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ayokunle Olubaniyi, M.B,B.S [2]

Causes

Life Threatening Causes

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.

Management

Characterize the symptoms: ❑ Chest pain ❑ Cough ❑ Cyanosis ❑ Diaphoresis ❑ Dyspnea ❑ Fever ❑ Hypotension ❑ Tachycardia ❑ Tachypnea

Patient evaluation: ❑ Obtain a detailed history: ♦ Age ♦ History of heart disease ♦ History of chest infection ❑ Examine the patient: ♦ Head/Neck - Neck veins (flat, no ↑JVP) ♦ Chest - No S3/S4, no murmurs ♦ Limbs - Hyperdynamic pulses, no edema

Urgent Labs: ❑ ABG ❑Calculate A-a gradient ❑ CBC ❑ Electrolytes ❑ BUN ❑ Creatinine ❑ CXR - normal-sized heart, peripheral distribution of infiltrates, air-bronchogram (80%) Consider additional tests, if necessary: ❑ Bronchoalveolar lavage - gram stain, culture & cytology ❑ Bronchoscopy ❑ BNP - <100 pg/mL ❑ CT ❑ Echocardiography ❑ EKG - sinus tachycardia, non-specific ST-T wave changes ❑ Lung biopsy ❑ PAWP - <15 mmHg

Diagnostic Criteria - The Berlin Definition

Emergent therapy ❑ Pulse oximetry ❑ Administer 100% oxygen - non-rebreather face masks, nasal prongs ❑ Initiate management of the underlying precipitating factor ❑ Consider right heart catheterization if hypotension persists

❑ Check vital signs ❑ Assess hemodynamic status: ♦ RR<35 bpm ♦ PaC02 <35 mmHg ♦ Sp02 >88%

Stable

Unstable

❑ Maintain Sp02 between 88-95% by adjusting Fi02 ❑ Treat underlying disease

❑ Transfer ICU ❑ Intubate (indications) ❑ Mechanical ventilation protocol

Supportive treatment ❑ Analgesia - morphine ❑ Conservative fluid management ❑ Conscious sedation - lorazepam ❑ DVT prophylaxis ❑ Glucose control ❑ Nurse 30-45 degrees head-up position ❑ Nutritional support (enteral feeds) ❑ NPO (in severely ill) ❑ Prevent pressure ulcers ❑ Stress ulcer prophylaxis - PPI

Mechanical Ventilation Protocol

❑ Calculate the predicted body weight (PBW) Males - 50 + 2.3 [height (inches) - 60] Females - 45.5 + 2.3 [height (inches) - 60] ❑ Ventilator mode - volume assist-control ❑ Set tidal volume (VT) to 8 ml/kg PBW ↓ ↓VT to 6 ml/kg PBW over the next 4 hours ❑ Flow rate - 60-80 lpm ❑ Ventilation rate - start at 18, adjust based on CO2 and ventilatory needs (max = 35 bpm) ❑ I:E ratio = 1:10 to 1:30 ❑ Adjust VT and RR to achieve pH and plateau pressure goals below

Oxygenation Goal - Pa02 = 55 - 60 mmHg or Sp02 = 88 - 95% ❑ Start at FiO2 of 1.0 (100% O2); PEEP of 5 cmH2O ❑ Check ABG/pulse oximeter

Sp02 < 88%

Sp02 > 95%

Adjust FiO2/PEEP based on ARDSnet PEEP/FiO2 ladder Monitor ABG Note - Maintain FiO2 < 0.6

↓FiO2 until Sp02 is > 95%

Assess perfusion ( BP, urine output)

Adequate

Inadequate

Strict input/output monitoring

Administer volume (fluid management)

Check plateau pressure Goal - Pplat ≤ 30 cmH20 ❑ Hold 'inspiratory hold' button for 0.5 seconds ❑ Check after each setting change or at least q 4hourly

> 30 cmH20 ↓VT by 1 ml/kg steps Min = 4 ml/kg

< 25 cmH20 & VT < 6 ml/kg ↑VT by 1 ml/kg until Pplat > 25 or VT = 6 ml/kg

< 30 + breath stacking or dys-synchrony May ↑ VT in 1 ml/kg to 7 or 8 ml/kg, if Pplat remains ≤ 30 cmH20

Achieve pH goal Goal = 7.30 - 7.45 pH 7.15 - 7.30 - ↑RR until pH > 7.30 or PaC02 < 25; max set RR = 35 pH <7.15 ❑↑RR to 35; if pH is still < 7.15, ↑VT by 1 ml/kg until pH > 7.15 - you may exceed Pplat target of 30 ❑ Give NaHC03 pH > 7.45 - ↓RR

Weaning

Dos

• Nurse patient in semi-recumbent position (30-45 degrees) to reduce the risk of hospital-acquired pneumonia, especially those on enteral feeds.
• Conscious sedation and analgesia to reduce oxygen consumption.
• FiO2 is usually kept below 0.5 to reduce oxygen toxicity.
• Daily spontaneous breathing trials.