Respiratory mechanics ppoFEV1% = preop FEV1% × (1- %Functional lung tissue removed/100) For example, after a right lower lobectomy a patient with a preoperative FEV1 (or DLCO) 70% of normal would be expected to have a postoperative FEV1 = 70% × (1 - 29/100) = 50% Ppo FEV1 >40% -Low risk 30-40%- mod risk < 30% - high riskSlinger PD, Johnston MR: Preoperative assessment: an anesthesiologists perspective. Thorac Surg Clin 15:11, 2005.
Cardiopulmonary Interaction Maximum oxygen consumption (Vo2max) Most useful predictor of post-thoracotomy outcome. Morbidity and mortality is unacceptably high- Vo2max <15 mL/kg/min. Few patients with a Vo2max >20 mL/kg/min have respiratory complications Stair climbing 5 flights - Vo2max >20 mL/kg/min 2 flights - Vo2max of 12 mL/kg/min 6-minute test (6MWT) <2000 ft (610 m) - Vo2max <15 mL/kg/min Patients with a decrease of Spo2 greater than 4% during exercise are at increased risk for morbidity and mortality.
Preoperative Optimization• Stop smoking, avoid industrial • Adjunct medication pollutants – Antibiotics—if purulent• Dilate airways sputum/bronchitis• Loosen secretions – Antacids, H2 blockers, or PPIs—if symptomatic reflux. – Airway hydration (humidifier/nebulizer) • Increased education, – Systemic hydration motivation, and facilitation of – Mucolytic and expectorant postoperative care drugs – Psychological preparation• Remove secretions – Preoperative pulmonary care training – Postural drainage • Incentive spirometry – Coughing • Secretion removal maneuvers – Chest physiotherapy – Preoperative exercise (percussion and vibration) – Weight loss/gain – Stabilize other medical problems
Summary of initial preoperativeassessment All patients: Cancer patients: Assess exercise tolerance consider the “4 Ms”: mass effects estimate predicted metabolic effects postoperative FEV1% Metastases discuss postoperative medications analgesia COPD patients: discontinue smoking Arterial blood gas analysis Patients with predicted Physiotherapy postoperative FEV1< 40%: bronchodilators DlCO Increased renal risk: Ventilation perfusion Scan Measure creatinine and VO2 max blood urea nitrogen
Double lumen tube Carlens tube Robertshaw tube Advantages Quickest to place successfully Disadvantages Repositioning rarely required Size selection more difficult Bronchoscopy to isolated lung Difficult to place in patients Suction to isolated lung with difficult airways or abnormal tracheas CPAP easily added Not optimal for postoperative Can alternate OLV to either ventilation lung easily Potential laryngeal trauma Placement still possible if bronchoscopy not available Potential bronchial trauma
Positioning• Position Change – W/f hypotension – Secure all lines and monitors – Make an initial “head-to-toe” survey – Check oxygenation, ventilation, hemodynamics, lines, monitors, and potential nerve injuries. – Reassess after repositioning – Recheck Endobronchial tube/blocker position and the adequacy of ventilation by auscultation and fiberoptic bronchoscopy after repositioning.
Treatment of Hypoxemia• Severe or precipitous desaturation: – Resume two-lung ventilation (if possible).• Gradual desaturation: – Ensure that delivered FIO2 is 1.0 – Check position of DLT or blocker with fiberoptic bronchoscopy – Ensure cardiac output is optimal; decrease volatile anesthetics to < 1 MAC – Apply a recruitment maneuver to the ventilated lung – Apply PEEP 5 cm H2O to the ventilated lung – Apply CPAP 1-2 cm H2O to the nonventilated lung (apply a – recruitment maneuver to this lung immediately before CPAP) – Intermittent reinflation of the nonventilated lung – Partial ventilation techniques of the nonventilated lung: • Oxygen insufflation • High-frequency ventilation • Lobar collapse (using a bronchial blocker) – Mechanical restriction of the blood flow to the nonventilated lung
Ventilation StrategiesParameter Suggested Guidelines/ Exceptions Maintain:Tidal volume 5-6 mL/kg Peak airway pressure < 35 cm H2O Plateau airway pressure < 25 cm H2OPositive end-expiratory Patients with COPD: no 5 cm H2Opressure added PEEP Maintain normal PaCO2; Pa-ETCO2 will usuallyRespiratory rate 12 breaths/min increase 1-3 mm Hg during OLV Pressure control for patients at risk of lung Volume or pressureMode injury (e.g., bullae, controlled pneumonectomy, post lung transplantation)
Thoracic Epidural Analgesia• Better preservation of the functional residual volume• Efficient mucociliary clearance• Alleviation of the inhibiting reflexes acting on the diaphragm• prevention of atelectasis and secondary infections
Postoperative Complications• Early Major Complications – Torsion of a remaining lobe after lobectomy – Dehiscence of a bronchial stump – Hemorrhage from a major vessel – Respiratory Failure – Cardiac Herniation
Anaesthetic management of bronchopleural fistulaBronchopleural fistula Communication from major bronchus to pleural space Commonly associated with pneumonectomy, trauma, abscess or empyema Relevant complications Pus may contaminate other lung-associated injuries with traumaSurgery Usually semi-elective Resuturing of bronchial stump, muscle flap to stump, drainage of abscess High risk surgery requiring GA and one-lung ventilation If incidental surgery, GA may be avoided, regional preferred Positioning still important to avoid soiling
Patient Commonly debilitated, may have coexistent medical problems Respiratory function assessed Clinical, spirometry, ABGs Routine assessment for thoracic surgery Consideration of epidural Decision to proceed Respiratory function optimized Chest drain inserted to avoid tension pneumothorax and drain pleural collection
Induction Objectives Maintain oxygenation and ventilation, avoid tension pneumothorax Avoid soiling good lung Protection of lung requires DLT, bronchial lumen to good side Small leak without infection may be manageable with single-lumen ETT Paediatric patients are typically too small for DLT or FOB --> blocker or endobronchial intubation Fistula reduces effectiveness of mask IPPV, so spontaneous ventilation Ideally awake DLT intubation Topical local anaesthetic to airway Position head-up and bad side down Sedation for intubation Alternatively spontaneously ventilating GA with DLT insertion when deep Verification of DLT position with differential ventilation or FOB
Maintenance IPPV to healthy lung Lung with fistula may benefit from small VT ventilation or CPAP below critical pressure for fistula or HFJV Emergence Avoid high airway pressures if fistula has been repaired Hand ventilation or SIMV Postoperative Epidural analgesia HDU monitoring post-op High incidence of arrhythmia post-thoracotomy