Anaesthetic Management — Three Special Cases

CASE 1: COPD Patient for Orthopaedic Surgery

Pathophysiology Relevant to Anaesthesia

• Air trapping → hyperinflation → intrinsic PEEP (auto-PEEP)
• V/Q mismatch → hypoxaemia
• Hypercapnia (chronic CO₂ retention)
• Increased work of breathing
• Reduced FEV₁/FVC ratio (obstructive pattern)
• Pulmonary hypertension and cor pulmonale (advanced disease)

Preoperative Assessment

• Severity and duration of COPD: GOLD classification (I–IV) based on FEV₁
• Exercise tolerance (functional capacity in METs)
• Current medications: bronchodilators (SABA, LABA, LAMA), inhaled corticosteroids, theophylline, oxygen therapy
• Recent exacerbations, hospitalisations, need for mechanical ventilation
• History of cor pulmonale, right heart failure, pulmonary hypertension
• Smoking history and current status

• Spirometry: FEV₁, FVC, FEV₁/FVC ratio — severity staging
• Chest X-ray: hyperinflation, bullae, consolidation, cardiomegaly
• ABG: chronic hypercapnia (high PaCO₂), compensated respiratory acidosis, baseline PaO₂
• ECG: right heart strain, P pulmonale, right bundle branch block, cor pulmonale changes
• Echocardiography: if pulmonary hypertension or RV dysfunction suspected
• Full blood count: secondary polycythaemia (elevated Hb/haematocrit)

• Continue all bronchodilators on the day of surgery
• Smoking cessation (ideally 8 weeks before — reduces secretions and mucociliary clearance improves)
• Treat active infection (course of antibiotics)
• Physiotherapy: chest physiotherapy, incentive spirometry
• Consider preoperative pulmonary rehabilitation for elective cases
• Theophylline levels if on xanthines
• Correct hypokalaemia (from beta-agonist/steroid use)
• Avoid adenosine and dipyridamole for cardiac stress testing — they can exacerbate bronchospasm in COPD patients on theophylline (Miller's, Chapter 29)

Anaesthetic Management — Intraoperative

Choice of Technique

• Spinal or epidural anaesthesia for lower limb surgery (hip/knee arthroplasty, tibial fractures) avoids airway instrumentation, PPV, and atelectasis
• Peripheral nerve blocks (femoral, sciatic, popliteal) are ideal for distal lower limb procedures
• Regional techniques preserve mucociliary function and avoid post-extubation bronchospasm
• Caveat: high spinal levels (>T6) impair accessory respiratory muscles → risk of respiratory compromise in severe COPD

• LMA preferred over ETT for spontaneous/low-pressure ventilation where applicable (avoids tracheal stimulation → bronchospasm)
• ETT if airway protection needed; consider deep extubation (extubate before airway reflexes return) to avoid cough/bronchospasm
• TIVA (propofol ± remifentanil) is advantageous — propofol has mild bronchodilator properties; volatile agents (sevoflurane, isoflurane) are also bronchodilators

Induction

• Pre-oxygenation essential
• Avoid histamine-releasing drugs (morphine, atracurium, mivacurium) → bronchospasm
• Preferred muscle relaxants: rocuronium (and reverse with sugammadex — avoids neostigmine-induced bronchospasm); if using neostigmine, co-administer glycopyrrolate
• Miller's specifically notes (Chapter 24) that neostigmine (anticholinesterase) can cause bronchospasm and should be used cautiously; sugammadex is the preferred reversal agent in COPD

Ventilation Strategy

• Avoid hyperventilation — COPD patients with chronic hypercapnia have a compensated bicarbonate elevation; rapidly normalising PaCO₂ leads to post-hypercapnic alkalosis
• Target permissive hypercapnia — allow PaCO₂ 45–55 mmHg (matching baseline)
• Prolonged expiratory phase: I:E ratio 1:3 to 1:4 to allow full exhalation and prevent auto-PEEP
• Low respiratory rate (8–12/min), moderate tidal volumes (6–8 mL/kg IBW)
• Avoid high PEEP (worsens hyperinflation and auto-PEEP)
• Minimise peak airway pressures → prevents bullae rupture and pneumothorax
• Watch for auto-PEEP (intrinsic PEEP): detect by disconnecting circuit at end-expiration

Bronchospasm Management

• Increase volatile agent concentration (potent bronchodilators)
• Nebulised salbutamol via circuit
• IV ketamine 0.5–1 mg/kg (bronchodilator)
• IV hydrocortisone / methylprednisolone
• IV aminophylline if refractory

Monitoring

• Standard ASA monitoring + capnography (ETCO₂ may underestimate PaCO₂ due to increased dead space — serial ABGs advisable for major/long surgeries)
• Arterial line for complex cases or those with severe COPD (ABG monitoring, haemodynamic instability)

Postoperative Management

• Early ambulation — reduces respiratory complications
• Avoid over-sedation — opioids → respiratory depression, CO₂ retention
• Multimodal analgesia: paracetamol, NSAIDs (with caution), nerve blocks, epidural (reduces opioid requirement and improves respiratory function)
• High-flow nasal oxygen or CPAP — prevents atelectasis; BiPAP if pre-existing chronic hypercapnia
• HDU/ICU monitoring if FEV₁ <50% predicted or baseline PaCO₂ >45 mmHg
• Chest physiotherapy and early physiotherapy
• Resume all bronchodilators and respiratory medications promptly
• Watch for pneumothorax (especially if bullae present)

CASE 2: Bronchopleural Fistula (BPF) — Anaesthetic Management

Definition and Aetiology

1. Rupture of lung abscess, bronchus, bulla, cyst, or parenchymal tissue into the pleural space
2. Erosion of bronchus by carcinoma or chronic inflammatory disease
3. Stump dehiscence of bronchial suture line after pulmonary resection (most common surgical cause)

Diagnosis

• Clinical: sudden dyspnoea, subcutaneous emphysema, contralateral tracheal deviation, decrease in fluid level on serial chest X-rays (post-pneumonectomy)
• In lobectomy patients: persistent air leak, purulent drainage, expectoration of purulent material
• After chest tube removal: fever, purulent sputum, new air-fluid level on CXR
• Confirmed by bronchoscopic examination; also by bronchography, sinograms, methylene blue injection into pleural space with recovery from sputum, or radionuclide (xenon) accumulation in pleural space

Anaesthetic Challenges (Miller's)

1. Need for lung isolation to protect healthy lung regions
2. Possibility of tension pneumothorax with positive-pressure ventilation
3. Possibility of inadequate ventilation due to air leak through the fistula

Preoperative Assessment of Fistula Size

• Intermittent air bubbling through chest tube water-seal → small fistula
• Continuous air bubbling → large BPF or bronchial rupture
• Quantification: difference between inhaled and exhaled tidal volumes
  • Non-intubated: tight-fitting mask with fast-responding spirometer
  • Intubated: spirometer attached directly to endotracheal tube
• Rule: the larger the air leak, the greater the need for lung isolation (DLT or bronchial blocker)

Preoperative Preparation

• Chest drain must be placed before induction to avoid tension pneumothorax with positive-pressure ventilation — this is mandatory
• Assess patient's overall fitness; septic patients may be on antibiotics
• If sepsis present: thoracic epidural catheter placement is not recommended (Miller's)

Intraoperative Anaesthetic Management

Lung Isolation Device

• Double-lumen tube (DLT) is the best choice for BPF:
  • Provides PPV to normal lung without loss of minute ventilation through the fistula
  • Prevents contamination of uninfected lung with infected material (especially when patient is in lateral decubitus)
  • For right-sided fistula (or post-right-pneumonectomy fistula): use left-sided DLT
  • For post-pneumonectomy fistula: endobronchial lumen placed in the uninvolved (non-fistula) lung

Golden Rule (Miller's):

"Lung isolation must be confirmed before positive-pressure ventilation or repositioning the patient."

Induction Technique Options (Miller's)

• Requires cooperative patient and excellent topical anaesthesia
• Ensures lung isolation before PPV commences
• Often not feasible

• Maintain spontaneous breathing during induction and intubation until lung isolation secured
• Avoids risk of inadequate PPV due to air leak
• Not well-tolerated in older patients with significant comorbidity

• Direct bronchoscopic guidance of DLT placement
• Acceptable when appropriate fibreoptic bronchoscopes available
• Commonly used in clinical practice

Alternative/Non-Surgical Approaches

• Thoracic epidural anaesthesia + IV sedation: for minimally invasive surgery in post-pneumonectomy BPF — avoids airway instrumentation entirely (discussed in Miller's under "Nonintubated Thoracic Surgery")
• One-way endobronchial valves: used in patients unfit for surgery, seal the fistula endobronchially
• High-frequency oscillatory ventilation (HFOV) with permissive hypercapnia: for multiple BPFs
  • Uses lower peak airway pressure and higher minimum airway pressure
  • Decreases BPF air leak; avoids barotrauma to non-operative lung
  • Advantage over conventional ventilation: reduces air leak across fistula
• Venovenous ECMO: described in complex cases (e.g., existing left BPF + right thoracotomy for tumour resection) — initiated before OLV to maintain oxygenation during lung collapse

Ventilation Principles

• After lung isolation: ventilate only the unaffected lung
• Use one-lung ventilation (OLV) strategies
• Minimise tidal volumes and airway pressures on the non-fistula side
• PEEP to pleural cavity (equal to intrathoracic PEEP) as an adjunct
• Differential lung ventilation as needed

Postoperative Management

• Early extubation in the operating room should be considered in all patients undergoing fistula repair → avoids barotrauma to the surgical stump from PPV in the postoperative period (Miller's)
• If PPV needed postoperatively: minimise peak airway pressures
• Chest tube drainage continued
• Monitor for residual air leak
• Antibiotics for empyema/infection
• Nutritional support; early physiotherapy

CASE 3: Male with Left ICD In Situ for Orthopaedic Surgery

Background: CIEDs in the Perioperative Period

Preoperative Assessment

• Type of device: ICD only vs. ICD with pacing function (CRT-D)
• Device interrogation report: within 6 months prior to surgery (for ICD); within 12 months for pacemaker
• Indication for ICD: primary prevention (cardiomyopathy, EF <35%) vs. secondary prevention (prior VT/VF arrest)
• Current ICD settings: detection thresholds, therapy zones, pacing mode
• Pacemaker dependency: if patient has concurrent pacing — is pacing-dependent? (critical if planning to temporarily inactivate ICD)
• Last discharge (appropriate/inappropriate); ICD battery status (end-of-life alert?)
• Underlying cardiac disease: cardiomyopathy, IHD, heart failure — assess LV function (echo), NYHA class
• Current medications: antiarrhythmics (amiodarone, sotalol), anticoagulants, antiplatelet agents
• Implant site: left-sided ICD — generator in left pectoral region, leads through left subclavian into RV/RA

Key Perioperative Concerns with ICD

1. Electromagnetic Interference (EMI)

• Electrocautery (monopolar) — most common and important source
• Radiofrequency ablation
• Lithotripsy devices
• Radiation therapy
• Direct mechanical interference during central venous catheter insertion (guidewire movement)

• Inappropriate ICD shock (EMI sensed as VF → device delivers unnecessary shock)
• Inappropriate changes in pacing rate
• Pacing inhibition (EMI sensed as intrinsic activity → pacing inhibited → asystole in pacing-dependent patient)
• Device damage or re-programming

2. Orthopedic Surgical Context — Specific Concerns

• Monopolar diathermy is commonly used in orthopaedic surgery → highest EMI risk
• If bipolar diathermy is used and kept >15 cm from device → risk is significantly reduced
• Surgical site (lower limb) is distant from the left-sided ICD — this reduces but does not eliminate EMI risk

Preoperative Planning (Miller's, Box 28.7 principles)

• Consult CIED care team (electrophysiologist/device clinic) preoperatively
• Joint plan between anaesthesiologist, surgeon, and EP team
• Interrogate device and obtain current settings report
• Determine whether ICD needs to be temporarily suspended (deactivated) or reprogrammed

• External defibrillator with pads in place and active throughout the procedure (mandatory)
• Pads should be positioned anterior-posterior (to avoid placing pads over ICD generator)
• Cardiac monitoring (ECG) continuously throughout surgery

Anaesthetic Management — Intraoperative

Monitoring

• Standard ASA monitoring: ECG (5-lead if possible), SpO₂, NIBP, capnography
• Ensure continuous ECG monitoring — to detect device malfunction, arrhythmia, pacing failure
• Have external defibrillator immediately available

Diathermy Precautions

• Bipolar diathermy preferred wherever possible
• If monopolar is essential:
  • Use short, infrequent bursts (<5 seconds)
  • Keep return electrode (dispersive pad) positioned such that current path does not cross the ICD generator and leads
  • For a left-sided ICD: return pad placed on left buttock/thigh (not right side) so current path is ipsilateral and distal to the device
  • The surgical site (lower limb orthopaedic) is well below the ICD — this is advantageous
  • Inform surgeon to avoid electrocautery near the device site

Choice of Anaesthetic Technique

• Regional anaesthesia (spinal/epidural) preferred for lower limb orthopaedic surgery:
  • Avoids EMI concerns entirely (no electrocautery to head/neck/chest)
  • However, if defibrillation is needed, standard paddles/pads still work
  • Monitor ECG throughout regardless
• General anaesthesia if required:
  • Avoid suxamethonium-induced muscle fasciculations → can generate EMI-like signals → inappropriate ICD detection; use RSI with high-dose rocuronium if rapid sequence needed
  • Muscle relaxants during maintenance: rocuronium preferred → reverse with sugammadex (avoids neostigmine → muscle fasciculations → EMI)
  • Hypothermia, acidosis, and electrolyte imbalance increase arrhythmia risk → maintain normothermia, correct electrolytes (K⁺, Mg²⁺)

Anticoagulation Management

• Patients with ICDs are often on anticoagulants (warfarin, DOACs) for AF or LV thrombus
• For neuraxial anaesthesia: manage per standard anticoagulation bridging guidelines
• Consult haematology/cardiology if bridging therapy needed
• Miller's (Chapter 28, Table 28.12) identifies high-risk patients for thromboembolism — these patients need bridging anticoagulation and careful timing

Postoperative Management

• Restore ICD function immediately after the procedure — device should be re-interrogated and reactivated in recovery room
• Continuous ECG monitoring until ICD reactivated
• Check device integrity: re-interrogate post-procedure to confirm no EMI-related reprogramming or damage
• Confirm appropriate sensing and therapy delivery capability

• Continue cardiac monitoring in recovery (HDU if high-risk)
• Resume anticoagulation as per surgical/anaesthetic plan
• Continue all cardiovascular medications
• Watch for arrhythmias in the early postoperative period (pain, hypoxia, electrolyte shifts are arrhythmia triggers)
• Liaise with CIED team for outpatient follow-up

Summary Comparison Table