Anaesthesia for COPD

Pathophysiology Relevant to Anaesthesia

Preoperative Assessment

History

• Dyspnea grading: FEV₁ <50% predicted → dyspnea on exertion; FEV₁ <25% (<1 L in men) → dyspnea at minimal activity, often with CO₂ retention and pulmonary hypertension
• Productive cough: volume, colour, and culture of sputum; treat active infection with antibiotics pre-op
• Exercise tolerance: inability to climb stairs or walk on level ground signals markedly reduced reserve
• Wheeze, recent exacerbations, recent hospitalisations

Investigations

• Spirometry (PFTs): FEV₁/FVC <0.7 confirms obstruction; FEV₁ % predicted grades severity (GOLD 1–4). However, PFT findings are NOT predictors of perioperative pulmonary complications and should not be used to deny surgery
• ABG: establish baseline; PaCO₂ >45 mmHg = chronic CO₂ retention → higher postoperative morbidity; PaO₂ helps gauge severity of hypoxaemia
• Chest X-ray: hyperinflation, bullae (critical — bullae + N₂O = risk of pneumothorax), increased lung markings
• ECG and ECHO: for cor pulmonale, right ventricular dysfunction, pulmonary hypertension
• ARISCAT score can stratify perioperative pulmonary risk (low <26, intermediate 26–44, high ≥45, with complication rates of 1.6%, 13.3%, and 42.1% respectively)

Risk Factors for Postoperative Pulmonary Complications

• Patient: COPD, advanced age, ASA class ≥2, smoking history, obesity, low functional capacity, pre-existing hypoxaemia, pulmonary hypertension, cor pulmonale, anaemia, poor nutritional status
• Procedure: thoracic > upper abdominal > aortic > neurosurgical; emergency surgery; duration >3 hours; general anaesthesia

Optimisation Before Elective Surgery

1. Smoking cessation ≥6–8 weeks before surgery — reduces secretions and carboxyhaemoglobin; even 24h cessation improves O₂-carrying capacity
2. Continue long-acting bronchodilators, anticholinergics (ipratropium, tiotropium), inhaled corticosteroids — on the day of surgery
3. Treat any active exacerbation aggressively before proceeding
4. Antibiotics for active sputum infection
5. Short course corticosteroids (e.g. prednisolone 40 mg/day × 2 days) for significant COPD/asthma
6. Chest physiotherapy, incentive spirometry, breathing exercises, postural drainage
7. Pulmonary rehabilitation in high-risk patients (prehabilitation — promising but evidence certainty remains low)
8. Discuss with patient: possible need for postoperative ICU admission and ventilation in high-risk cases (FEV₁ <50% predicted)

Choice of Anaesthesia

Regional vs General

• Regional anaesthesia is generally preferred where feasible — avoids airway manipulation, reduces postoperative opioid requirement, reduces risk of respiratory depression
• However: high spinal or epidural blocks decrease lung volumes, restrict accessory respiratory muscles, produce ineffective cough → dyspnea and retained secretions
• Interscalene blocks are relatively contraindicated due to risk of hemidiaphragmatic paralysis
• Position concerns (lithotomy, lateral decubitus) may worsen dyspnoea in awake patients

If General Anaesthesia Is Required

• Preoxygenation is essential — COPD patients desaturate rapidly at induction
• LMA vs ETT: avoid endotracheal intubation where possible (airway stimulation provokes bronchospasm); use LMA when appropriate
• Induction agents: propofol or ketamine preferred; ketamine has bronchodilatory properties
• Volatile agents (sevoflurane, desflurane, isoflurane) are bronchodilators — preferable to TIVA in bronchospasm-prone patients; however, in severe COPD, increased dead space makes end-tidal volatile concentration unreliable
• Avoid N₂O: contraindicated if bullae (pneumothorax risk) or pulmonary hypertension; also worsens V/Q mismatch
• Opioids: use with caution; respiratory depression risk; short-acting preferred (fentanyl/remifentanil)
• Neuromuscular blockers: use the minimum necessary; ensure complete reversal (residual block is a major risk factor for postoperative pulmonary complications); prefer sugammadex for reversal of rocuronium/vecuronium

Intraoperative Ventilation Strategy

Ventilator Settings

Permissive Hypercapnia

• Allow PaCO₂ to rise if needed to avoid dangerous airway pressures — PaCO₂ up to 70 mmHg may be tolerated short-term with adequate cardiovascular reserve
• Avoid rapid normalisation of CO₂ in chronic retainers (will cause post-hyperventilation alkalosis)
• Monitor arterial CO₂ directly (not just ETCO₂) — the arterial-to-end-tidal CO₂ gradient is widened due to increased dead space in COPD

iPEEP Management

1. Slow respiratory rate + prolonged expiratory time
2. Reduce tidal volume
3. Treat bronchospasm aggressively (nebulised salbutamol, ipratropium, IV hydrocortisone)
4. Apply low-level extrinsic PEEP (stents small airways open)

Intraoperative Complications

Postoperative Management

• Extubation criteria: adequate pain control, full reversal of NMB, minimal/no bronchospasm, secretions manageable, no significant hypercapnia, SpO₂ acceptable on moderate FiO₂
• Avoid early extubation in high-risk cases; plan for HDU/ICU postoperatively
• Regional analgesia / epidural postoperatively reduces the need for systemic opioids → fewer respiratory complications
• O₂ therapy: target SpO₂ 88–92% in confirmed CO₂ retainers (not high-flow); avoid hyperoxia suppressing hypoxic drive
• Chest physiotherapy, incentive spirometry, early mobilisation
• NIV/CPAP: useful for postoperative atelectasis and mild-to-moderate respiratory failure
• Monitor for delayed pulmonary complications: pneumonia, atelectasis, respiratory failure, exacerbation

Key Points Summary

• COPD is a major independent risk factor for postoperative pulmonary complications
• Preoperative optimisation is mandatory; only limited improvement may occur in a short preoperative window (unlike asthma)
• Regional anaesthesia is preferred but has its own respiratory caveats
• If GA: bronchodilating volatiles preferred; avoid N₂O in bullae/pulmonary hypertension
• Ventilate with slow rate and prolonged expiration; accept permissive hypercapnia; watch for iPEEP
• Pneumothorax must be excluded early when unexplained haemodynamic collapse occurs
• Postoperative epidural/regional analgesia and targeted O₂ therapy are important

• Morgan & Mikhail's Clinical Anesthesiology, 7e — Chapter 24 (COPD pathophysiology and anaesthetic considerations)
• Miller's Anesthesia, 10e — Chapter 28 (postoperative pulmonary complications, preoperative risk stratification)
• Barash, Cullen & Stoelting's Clinical Anesthesia, 9e — Chapter on thoracic anaesthesia and COPD assessment
• Miller's Anesthesia, 10e — Chapter 52 (vascular surgery: pulmonary assessment including COPD)