• One Lung Anaesthesia
    • Indications
      • Absolute
        • Lung isolation
          • Infection
          • Massive haemorrhage
        • Control of ventilation
          • Bronchopleural fistula
          • Tracheobronchial tree disruption
          • Giant unilateral cyst/bulla
          • Open surgery to main bronchi
        • Unilateral lavage
          • Alveolar proteinosis
      • Relative
        • Surgical access
          • Thoracic aortic aneurysm
          • Pneumonectomy
          • Mediastinal surgery
          • Lobectomy
          • Pneumonectomy
        • Non-thoracic surgery
          • Spinal thoracic surgery
        • Severe hypoxaemia due to unilateral lung disease
    • Pre-op
      • History
        • Limited ET +/or cardiac problems increases risk of peri operative complications
      • Spirometry
        • FEV1 <2L is associated with 40% incidence of post op resp failure.
      • ABG
        • Hypoxaemia at rest increases risk
        • Hypercapnoea - unlikely to tolerate OLA
      • Evaluation of individual lung function
        • Predicts post op lung function after resection
        • Radio-isotope 133Xe or 99Tc
        • PPO FEV1 is pre-op FEV1 x proportion of non affected lung
        • PPO FEV1 of <0.85L is considered high risk
      • Further tests
        • Occlusion with PAFC to affected lung segment
    • Management of hypoxaemia
      • Increase FiO₂ to 1.0
      • Check tube position & exclude herniation
      • Suction
      • Check circuit and connections
      • Ensure adequate co
      • Insufflation of O₂ to non-ventilated lung
      • Apply CPAP to non-ventilated lung
      • Consider PEEP to ventilated lung
      • Intermittent inflation of collapsed lung
      • Clamping the appropriate PA may help
    • Post-op
      • CXR to rule out pneumothorax, haemothorax and chest drain positioning
    • Practical aspects
      • DLT used most commonly
        • 39-41 Fr males
        • 37-39 Fr females
        • Insert to ~29cm
      • L sided used more commonly
        • May not be possible in L pneumonectomy and proximal lesions
      • DLT has 2 curves
        • Distal curve is positioned so concave surface lies anteriorly until the tip is through the cords and then rotated 90 degrees and advanced
      • Check position clinically and with bronchoscope
      • Analgesia with epidural or paravertebral block
      • Bronchial blockers
        • Used in children if DLT too big and in patients where risk of aspiration is high who need ventilation post-op
        • Inserted under bronchoscopic vision
        • Allow suction and insufflation with O₂ but ventilation can't be done without loosing isolation
      • Endobronchial intubation with single lumen tube
        • Usually goes down R main but turn head to right and place tube concavity posterior to intubate L main
    • Anaesthesia
      • Aims
        • Decrease airway reflexes
        • Avoid HPV inhibition
        • Maintain normal CV status
    • Pulmonary blood flow & HPV during OLA
      • Inhaled gases at <1 MAC have minimal effect. N₂O inhibits HPV by ~ 10%.
      • IV agents propofol, ketamine, thiopentone and fentanyl have no effect
      • Vasodilators (GTN, SNP, NO, dobutamine, B-agonists) inhibit HPV
      • Vasoconstrictors (NA, adrenaline, phenylephrine) all increase shunt by directing flow to the collapsed lung. Dopamine has less effect so may be the vasopressor of choice.
      • High FiO₂ reduces shunt fraction
      • C.O. Effects are complex: low co may reduce CvO2 so impair arterial saturation in the presence of shunt. High co may increase PAP & increase perfusion to the non-ventilated lung so increase shunt fraction.
      • PEEP increases PVR so increases blood flow to the non-ventilated lung so increases shunt fraction
    • Physiology
      • Lateral decubitus position
        • 60% of blood flow goes to dependent lung
        • Ventilation preferentially to non-dependent lung
        • Compliance and FRC of dependent lung decreased by mediastinal weight, diaphragm and suboptimal positioning.
      • Chest opening
        • When chest is opened, compliance of non-dependent lung is increased leading to over-ventilation
        • This increases shunt in the dependent lung therefore increases the A/a gradient
      • Collapse of non-dependent lung
        • The non dependent lung is not ventilated so shunt is obligatory in addition to the shunt in the dependent lung
        • Blood in the non-dependent lung retains CO₂
        • Several mechanisms operate to decrease blood flow through the non-ventilated lung to ~20%
          • Gravity
          • HPV
          • Collapse causing mechanical obstruction to blood flow
    • CEACCP
      Link:ceaccp.oxfordjournals.org/content/2/3/83.full.pdf
    • CEACCP
      Link:ceaccp.oxfordjournals.org/content/10/4/117.full.pdf