Anaesthetic considerations in respiratory failure

Preoperative Assessment & Planning

• Determine type of respiratory failure: Type I (hypoxemic) vs. Type II (hypercapnic) - critical for management strategy
• Comprehensive respiratory history: Duration, severity, triggers, current medications, recent exacerbations
• Pulmonary function tests: FEV1, FVC, DLCO to assess severity and predict postoperative complications
• Arterial blood gas analysis: Baseline PaO₂, PaCO₂, pH to guide intraoperative management
• Optimize respiratory status preoperatively: Treat infections, optimize bronchodilators, consider pulmonary rehabilitation
• Assess comorbidities: Cardiac function, renal status, nutritional state which may be affected by chronic respiratory disease
• Review imaging: Chest X-ray, CT scans to identify anatomical abnormalities affecting ventilation
• Smoking cessation: At least 4-8 weeks before surgery to reduce complications

Intraoperative Management Considerations

• Airway management:
  • Anticipate difficult airway due to potential cervical spine limitations in COPD patients
  • Consider awake fiberoptic intubation for severe cases with risk of rapid desaturation
  • Prepare for potential need for difficult airway equipment
• Ventilation strategy:
  • Type I failure: Focus on oxygenation with appropriate PEEP, FiO₂, and recruitment maneuvers
  • Type II failure: Careful titration of minute ventilation to avoid worsening hypercapnia while preventing hypoxia
  • Avoid excessive tidal volumes (6-8 mL/kg ideal body weight) to prevent volutrauma
  • Permissive hypercapnia may be necessary in severe ARDS but requires careful monitoring
• Anesthetic selection:
  • Prefer short-acting agents with minimal respiratory depression
  • Titrate opioids carefully due to respiratory depressant effects
  • Consider total intravenous anesthesia (TIVA) for better control in severe cases
  • Avoid nitrous oxide in obstructive lung disease due to risk of air trapping
• Positioning considerations:
  • Head-up position may improve ventilation in some patients
  • Be cautious with extreme positions that may compromise respiratory mechanics

Monitoring Requirements

• Standard monitoring plus:
  • Continuous pulse oximetry with attention to desaturation patterns
  • Capnography (essential for detecting hypoventilation and airway issues)
  • Arterial line for continuous blood pressure monitoring and frequent ABGs
• Advanced respiratory monitoring:
  • Lung ultrasound for real-time assessment of lung sliding and aeration
  • Esophageal pressure monitoring in severe cases to assess transpulmonary pressure
  • Respiratory mechanics monitoring (compliance, resistance, auto-PEEP)
• Regular blood gas analysis:
  • Pre-intubation baseline
  • After intubation and ventilator setup
  • Periodically during prolonged procedures
  • Before extubation

Pharmacological Considerations

• Induction agents:
  • Ketamine: Beneficial in bronchospasm but may increase pulmonary pressures
  • Etomidate: Hemodynamically stable but may suppress adrenal function
  • Avoid propofol in hemodynamically unstable patients with respiratory failure
• Muscle relaxants:
  • Use cautiously - may prolong need for mechanical ventilation
  • Prefer short-acting agents (e.g., rocuronium over pancuronium)
  • Monitor depth of blockade with quantitative monitoring
  • Ensure complete reversal before extubation
• Opioids:
  • Titrate carefully; consider remifentanil for short procedures due to rapid clearance
  • Have naloxone readily available but use cautiously to avoid acute withdrawal of respiratory drive
• Bronchodilators:
  • Administer inhaled bronchodilators preoperatively for obstructive diseases
  • Have bronchodilators readily available intraoperatively

Extubation Considerations

• Extubation criteria must be stringent:
  • Adequate respiratory drive and pattern
  • Acceptable ABG on minimal support
  • Ability to maintain oxygenation on room air or minimal supplemental O₂
  • Absence of significant air trapping or dynamic hyperinflation
• Preparation for potential reintubation:
  • Have difficult airway equipment immediately available
  • Consider non-invasive ventilation (NIV) immediately post-extubation
  • Extubate during daytime with full team available if high risk
• Pharmacological preparation:
  • Administer bronchodilators pre-extubation for obstructive diseases
  • Consider corticosteroids for inflammatory conditions

Postoperative Management

• Enhanced monitoring: Extended monitoring in PACU or ICU based on severity
• Pain management:
  • Prefer regional techniques to minimize opioid requirements
  • If opioids necessary, use PCA with careful titration
  • Consider non-opioid alternatives (NSAIDs, acetaminophen, gabapentinoids)
• Early mobilization: Critical for preventing atelectasis and improving clearance
• Respiratory therapy:
  • Incentive spirometry
  • Chest physiotherapy
  • Early ambulation
• Non-invasive ventilation: Consider prophylactic NIV for high-risk patients
• Close monitoring for: Re-intubation signs, pneumonia, atelectasis, pulmonary edema

CRITICAL CONSIDERATION: Patients with pre-existing respiratory failure have significantly higher risk of postoperative respiratory complications, prolonged mechanical ventilation, and ICU admission. The decision to proceed with surgery should involve careful risk-benefit analysis with the surgical team and patient/family.

WARNING: Never underestimate the time required for adequate preoxygenation in patients with respiratory failure. Use denitrogenation with 100% oxygen for at least 3-5 minutes, and consider apneic oxygenation techniques for high-risk patients.