Health Dictionary
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Acute respiratory distress syndrome resident survival guide
Introduction
Overview
Overview
Below is a table showing The Berlin definition of Acute Respiratory Distress Syndrome:[1]
| Acute Respiratory Distress Syndrome | |
|---|---|
| Timing | ❑ Within 1 week of a known clinical insult or new or worsening respiratory symptoms |
| Chest imaging i.e., CXR or CT |
❑ Bilateral opacities—not fully explained by effusions, lobar/lung collapse, or
nodules |
| Origin of edema | ❑ Respiratory failure not fully explained by cardiac failure or fluid overload ❑ Need objective assessment (e.g., echocardiography) to exclude hydrostatic edema if no risk factor present |
| Oxygenation (Corrected for altitude) |
|
| Mild | ❑ 200 mm Hg < PaO2/FiO2 ≤ 300 mmHg with PEEP or CPAP > 5 cm H2O |
| Moderate | ❑ 100 mm Hg < PaO2/FIO2 ≤ 200 mm Hg with PEEP ≥ 5 cm H2O |
| Severe | ❑ PaO2/FiO2 ≤ 100 mm Hg with PEEP ≥ 5 cm H2O |
Causes
Causes
Life Threatening Causes
Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated. This is a life-threatening condition with majority of patients requiring mechanical ventilation.
Common Causes
- Aspiration of gastric contents
- Drug overdoses e.g., Acetylsalicylic acid, narcotics
- Fat embolism
- Massive blood transfusion
- Near-drowning (fresh or salt water)
- Pancreatitis
- Pneumonia
- Sepsis (gram-positive/gram-negative bacteria, viruses, fungi, and parasites)
- Severe trauma
Management
Management
Characterize the symptoms:
❑ Chest pain ❑ Cough ❑ Cyanosis ❑ Diaphoresis ❑ Dyspnea ❑ Fever ❑ Hypotension ❑ Tachycardia ❑ Tachypnea | |||||||||||||||||||||||
Patient evaluation:
❑ Obtain a detailed history: ❑ 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:
| |||||||||||||||||||||||
| 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 pH > 7.45 – ↓RR | |||||||||||||||||||||||||||||
| Weaning | |||||||||||||||||||||||||||||
ARDSNet PEEP/FiO2 Ladder
| FiO2 | 0.3 | 0.4 | 0.4 | 0.5 | 0.5 | 0.6 | 0.7 | 0.7 | 0.7 | 0.8 | 0.9 | 0.9 | 0.9 | 1.0 |
| PEEP | 5 | 5 | 8 | 8 | 10 | 10 | 10 | 12 | 14 | 14 | 14 | 16 | 18 | 20 |
Weaning
Conduct DAILY CPAP trial:
❑ Criteria: ❑ Process: ♦ Set CPAP to ≤5 cmH20; FiO2 to ≤0.50 | |||||||||||||||||||||||||||||||||||||||
| RR ≤ 35 bpm for 5 mins | |||||||||||||||||||||||||||||||||||||||
| Yes | No | ||||||||||||||||||||||||||||||||||||||
Pressure support (PS) trial ♦ Set PEEP ≤ 5; FiO2 ≤ 0.50 Note – Set pressure support based on RR during the CPAP trial | Discontinue trial Return to previous A/C settings Reassess next day or as directed by physician Find out reasons for trial failure | ||||||||||||||||||||||||||||||||||||||
| CPAP RR < 25 | CPAP RR = 25 – 35 | ||||||||||||||||||||||||||||||||||||||
| Set PS at 5 cm H20; PEEP at 5 | Set PS at 20 cm H20; PEEP at 5 | ||||||||||||||||||||||||||||||||||||||
Assess for tolerance (for up to 2 hours):
❑ Sp02 ≥ 90 &/or PaO2 ≥ 60% ❑ Spontaneous VT ≥ 4 ml/kg PBW ❑ RR ≤ 35 bpm ❑ pH ≥ 7.30 ❑ No respiratory distress (any 2 or more) ♦ HR > 120% of baseline ♦ Marked accessory muscle use ♦ Abdominal paradox ♦ Diaphoresis ♦ Marked dyspnea | ♦ ↓ PS by 5 q 1-3 hours (for RR ≤ 35) or every 5 mins (for RR < 25) ♦ ↑ PS by 5 if RR > 35 Note – If PS is ≥ 10 cmH20 in the evening or RR > 35 @ PS of 20, resume A/C and attempt weaning the next day | ||||||||||||||||||||||||||||||||||||||
| No | Yes | ||||||||||||||||||||||||||||||||||||||
❑ ↑ PS by 5 when RR > 35 ❑ Attempt weaning as ordered by physician Note – PS of 5 or 10 cmH20 may be maintained overnight | Trial of unassisted breathing Extubated with face masks, nasal prongs oxygen, or room air or T-tube breathing or Trach mask breathing or CPAP ≤ 5 cmH20 with no PS or IMV assistance | ||||||||||||||||||||||||||||||||||||||
| Reassess for tolerance (same as above) | |||||||||||||||||||||||||||||||||||||||
| Tolerated (for at least 30 mins) | Not tolerated | ||||||||||||||||||||||||||||||||||||||
| Extubate | Resume pre-weaning A/C settings | ||||||||||||||||||||||||||||||||||||||
Dos
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.
Don’ts
Don’ts
References
References
- ↑ Ranieri, VM.; Rubenfeld, GD.; Thompson, BT.; Ferguson, ND.; Caldwell, E.; Fan, E.; Camporota, L.; Slutsky, AS.; Ranieri, V. (2012). “Acute respiratory distress syndrome: the Berlin Definition”. JAMA. 307 (23): 2526–33. doi:10.1001/jama.2012.5669. PMID 22797452. Unknown parameter
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ayokunle Olubaniyi, M.B,B.S [2]