General Surgery · Year 3 · from General Surgery
Case 2: ARDS Following Aspiration Pneumonia
Patient Demographics
- Age: 58 years
- Sex: Male
- Occupation: Construction manager
Chief Complaint
"He aspirated during his surgery and now can't breathe on his own."
History of Present Illness
The patient underwent elective right hemicolectomy for colon cancer yesterday. During emergence from anesthesia, he vomited and aspirated gastric contents. He was reintubated immediately. Over the past 24 hours, he has developed progressively worsening hypoxemia despite increasing oxygen support. His chest X-ray has shown bilateral infiltrates. He is now on high ventilator settings with poor oxygenation.
Past Medical History
- Colon cancer (recent diagnosis)
- GERD (significant history, on PPI)
- Obesity (BMI 34)
- Obstructive sleep apnea
- Hypertension
Current Ventilator Settings
- Mode: Volume control
- Tidal volume: 550 mL (6-7 mL/kg ideal body weight)
- Rate: 24
- FiO2: 80%
- PEEP: 12 cmH2O
- Plateau pressure: 32 cmH2O
Arterial Blood Gas
- pH: 7.32
- PaCO2: 48 mmHg
- PaO2: 62 mmHg (on 80% FiO2)
- HCO3: 24 mEq/L
- P/F ratio: 77.5 (severe ARDS)
Laboratory Results
- WBC: 18,600/μL
- Hemoglobin: 11.2 g/dL
- Platelets: 186,000/μL
- Creatinine: 1.2 mg/dL
- Lactate: 2.4 mmol/L
Imaging
Chest X-ray:
- Bilateral diffuse alveolar infiltrates
- Consistent with ARDS
- No pneumothorax
Chest CT (if performed):
- Bilateral ground-glass opacities with dependent consolidation
- No pulmonary embolism
- Consistent with ARDS
Berlin Definition Assessment
- Timing: Within 1 week of known insult (aspiration)
- Chest imaging: Bilateral opacities not fully explained by effusion/collapse
- Origin of edema: Not fully explained by cardiac failure (ECHO normal)
- P/F ratio: 77.5 with PEEP ≥5 = Severe ARDS (<100)
Diagnosis
Severe ARDS secondary to aspiration pneumonia
Management - Lung Protective Ventilation (ARDSnet)
- Low tidal volume: Target 6 mL/kg ideal body weight (IBW)
- IBW: 80 kg → Target TV: 480 mL
- Plateau pressure: Target <30 cmH2O
- PEEP optimization: Use PEEP/FiO2 table (high PEEP strategy given severe ARDS)
- Permissive hypercapnia: Accept PaCO2 up to 60 if pH >7.25
- Conservative fluid strategy: Target CVP 4-8, maintain UOP
Adjunctive Therapies Considered
Prone positioning:
- Indicated for P/F <150 despite optimal ventilation
- Patient proned for 16 hours/day
- P/F ratio improved to 120 after proning
Neuromuscular blockade:
- Cisatracurium infusion for 48 hours
- Reduces ventilator dyssynchrony
- May improve outcomes in severe ARDS
Inhaled pulmonary vasodilators:
- Inhaled epoprostenol considered for refractory hypoxemia
- Not required as patient responded to proning
Clinical Course
- Day 1-3: Severe hypoxemia, continued prone positioning
- Day 4: P/F ratio improving (150), weaning FiO2
- Day 5: Supine, tolerating well
- Day 7: P/F ratio 220, passing spontaneous breathing trial
- Day 8: Extubated successfully
- Day 10: Transferred to floor on nasal cannula
Prevention of Future Aspiration
- Elevate head of bed 30-45 degrees
- Prokinetic agents for gastroparesis
- Consider post-pyloric feeding
- Optimize GERD management
Teaching Points
- ARDS = acute hypoxemic respiratory failure with bilateral infiltrates (Berlin Definition)
- P/F ratio determines severity (mild >200, moderate 100-200, severe <100)
- Low tidal volume ventilation (6 mL/kg IBW) is foundational
- Plateau pressure <30 cmH2O prevents ventilator-induced lung injury
- Prone positioning improves V/Q matching and survival in severe ARDS
- Conservative fluid management improves outcomes
- Aspiration is preventable - assess risk factors and implement precautions
Clinical Image
Image Description: Chest X-ray demonstrating bilateral diffuse alveolar infiltrates characteristic of acute respiratory distress syndrome (ARDS). The bilateral opacities are not fully explained by cardiac failure, effusion, or atelectasis.
Attribution: Image from Wikimedia Commons, Category:X-rays of the chest. Source: https://commons.wikimedia.org/wiki/Category:X-rays_of_the_chest