Perioperative respiratory management

🌬️ The Pre-Op Puff Check

• Smoking: Major risk for Postoperative Pulmonary Complications (PPCs). Advise cessation ≥4-8 weeks pre-op to ↓ risk.
• COPD/Asthma: Assess severity (e.g., FEV1/FVC < 0.7). Optimize with pre-op bronchodilators and/or steroids.
• Obstructive Sleep Apnea (OSA): Screen with 📌 STOP-BANG questionnaire. High risk for post-op hypoxemia and respiratory failure.
• Recent URI: Postpone elective surgery for 4-6 weeks to ↓ risk of laryngospasm/bronchospasm.

⭐ Smoking cessation >8 weeks pre-op significantly ↓ PPCs. Cessation <4 weeks may paradoxically ↑ airway reactivity and sputum.

🫁 Pathophysiology - Lungs Under Lockdown

• ↓ Functional Residual Capacity (FRC): The central event under general anesthesia (GA).
  • Supine position & neuromuscular blockade cause cephalad diaphragm shift.
  • Results in compression atelectasis, primarily in dependent lung zones.
• ↑ V/Q Mismatch:
  • Atelectasis creates an intrapulmonary shunt ($V/Q \approx 0$), causing hypoxemia.
  • Volatile anesthetics impair Hypoxic Pulmonary Vasoconstriction (HPV), worsening the shunt.
• ↓ Respiratory Control & Clearance:
  • Opioids & anesthetics blunt central chemoreceptor response to ↑ $CO_2$ and ↓ $O_2$.
  • ↓ Mucociliary clearance promotes secretion retention.

⭐ FRC can decrease by 15-20% within minutes of anesthesia induction, moving tidal breathing below closing capacity and predisposing to rapid desaturation.

🌬️ Management - Keeping Airways Awesome

• Pre-operative Strategy:

  • Risk Assessment: Use STOP-BANG for OSA; note smoking history.
  • Optimization: Mandate smoking cessation >4-8 weeks pre-op. Treat active infections. Optimize asthma/COPD with bronchodilators.

• Intra-operative Tactics:

  • Lung Protective Ventilation: Use low tidal volumes ($V_T$ = 6-8 mL/kg ideal body weight), apply PEEP (5-10 cmH₂O), and perform recruitment maneuvers.
  • Avoid high FiO₂ to prevent absorption atelectasis.

• Post-operative Care:

  • 📌 I COUGH: Incentive spirometry, Cough/deep breathing, Oral care, Understanding (patient education), Get moving (early mobilization), Head of bed elevation.
  • Prioritize regional analgesia over systemic opioids to facilitate effective breathing.

⭐ Postoperative pulmonary complications (PPCs), especially atelectasis, peak within the first 24-48 hours. They are a leading cause of morbidity after major non-cardiac surgery.

🌬️ Complications - When Breaths Go Bad

• Atelectasis (POD 1-2): Most common. Small airway collapse from ↓ lung volumes.
  • Presents with fever, tachypnea, ↓ breath sounds at bases.
  • Prevention/Tx: Incentive spirometry, deep breathing, early mobilization.
• Aspiration: Gastric contents enter lungs.
  • Pneumonitis: Immediate chemical injury.
  • Pneumonia: Bacterial infection, develops over days.
• Pneumonia (POD 3-5): Nosocomial infection (e.g., Pseudomonas, S. aureus).
  • Presents with fever, productive cough, consolidation on CXR.
• Pulmonary Embolism (PE): Sudden onset dyspnea, pleuritic chest pain, tachycardia.
• ARDS: Diffuse alveolar damage from sepsis, trauma. Hypoxemia refractory to O₂, bilateral infiltrates ("white-out").
• Laryngospasm/Bronchospasm: Airway hyperreactivity causing stridor or wheezing, often post-extubation.

⭐ Atelectasis is the most common cause of fever in the first 48 hours post-op. Often resolves with incentive spirometry and mobilization.

⚡ Biggest Takeaways

• Smoking cessation >4-8 weeks pre-op is crucial to ↓ postoperative pulmonary complications.
• General anesthesia consistently decreases functional residual capacity (FRC), leading to basilar atelectasis.
• Atelectasis is the most common cause of fever in the first 48 hours post-op; prevent with incentive spirometry.
• Aspiration pneumonitis risk is managed with strict NPO guidelines; high risk in obesity and emergency cases.
• Pulmonary embolism (PE) is a major preventable cause of postoperative mortality; prophylaxis is key.