Thoracic Anesthesia + One-Lung Ventilation
Thoracic + Cardiac · 10 min read
OLV is uncomfortable physiology — half the lung deliberately collapsed under positive pressure ventilation to half. The body fights you (HPV is GOOD — preserve it) and the surgeon needs the operating field. The competent anesthesia provider keeps both happy.
Why OLV — surgical access
Thoracic surgery (lobectomy, pneumonectomy, esophagectomy, pleural procedures, thoracic aortic, mediastinal mass) requires UNILATERAL LUNG COLLAPSE for surgical access. Lung must be deflated, not just unventilated — venting through the breathing circuit allows passive collapse over 5-10 min. Without OLV: surgical field is moving + lungs are in the way. With OLV: lung collapses, surgeon operates in a quiet, exposed thorax.
Equipment — DLT vs bronchial blocker
DOUBLE-LUMEN TUBE (DLT): preferred for routine adult thoracic. Left-sided 35-39 Fr (female-male). Right-sided ONLY when left mainstem inaccessible. Confirms position with FIBEROPTIC bronchoscopy (auscultation alone misses 30%). Reposition checks after every patient turn. BRONCHIAL BLOCKER (Arndt, Cohen, EZ-blocker): single-lumen ETT + balloon catheter blocks bronchus. Advantages: easier intubation (difficult airway), postop ventilation without tube exchange. Disadvantages: smaller working lumen, slower lung deflation.
Lung anatomy + bronchial tree →Hypoxic pulmonary vasoconstriction — the friend
HPV: localized hypoxia in alveoli causes PULMONARY VASOCONSTRICTION at that level, redirecting blood flow to better-ventilated alveoli. During OLV, HPV reduces shunt fraction in non-ventilated lung from theoretical 100% to ~30-40%. PRESERVE HPV: avoid volatile >1 MAC (volatiles inhibit HPV slightly), avoid systemic vasoconstrictors that raise PVR, avoid hypothermia, avoid metabolic acidosis. TIVA propofol/remifentanil preserves HPV slightly better than 1.0 MAC volatile in most studies.
Ventilator strategy on OLV
Tidal volume 5-6 mL/kg of IBW (NOT 8 — over-distension of dependent lung worsens shunt). PEEP 5-10 on dependent (ventilated) lung. RR adjusted to maintain ETCO₂ 35-45. PCV mode often preferred (more even gas distribution, lower peak pressures). Plateau pressure ≤25 cm H₂O target. ACCEPTABLE permissive hypercapnia if needed (PaCO₂ up to 50-60 OK if pH >7.20). FiO₂ as needed to maintain SpO₂ 92-95%.
Hypoxia algorithm during OLV
When SpO₂ falls during OLV (incidence 5-10%): (1) FiO₂ 1.0; (2) verify DLT position with fiberoptic bronchoscopy (commonest cause of hypoxia is migration); (3) suction DLT/ETT; (4) CPAP 5-10 cm H₂O to NONDEPENDENT (non-ventilated, surgical) lung — recruits some non-ventilated alveoli, modest oxygenation improvement, minimal disturbance to surgery; (5) optimize PEEP on dependent lung 5-10; (6) intermittent two-lung ventilation if persistent; (7) clamp pulmonary artery to non-ventilated side (eliminates shunt, possible during pneumonectomy).
Pneumonectomy — restrictive fluid management
Post-pneumonectomy pulmonary edema (PPPE): mortality up to 50%. Mechanism: doubling of pulmonary blood flow into single remaining lung + lymphatic drainage disruption. PREVENTION: RESTRICTIVE crystalloid (1-3 mL/kg/h, total <2 L for case), vasopressors over fluids for hypotension, lung-protective ventilation, goal-directed fluid therapy with stroke volume variation if available. Postoperative: continued restriction × 24-48 h, conservative diuresis if euvolemic.
Re-expansion + extubation
End of surgery: gradual re-expansion of operative lung — recruit slowly with positive pressure 30-40 cm H₂O × 30 sec, monitor for hypotension. Pleural effusion or pneumothorax should be drained pre-extubation (chest tube already in for thoracic cases). Extubation: AWAKE, sitting up, after meeting standard criteria + adequate analgesia (thoracic epidural or paravertebral or ESP catheter). Postop: ICU/step-down for first 24 h, continued analgesia, pulmonary toilet, early ambulation.
References
- · Slinger Principles + Practice of Anesthesia for Thoracic Surgery 2e
- · Miller's Anesthesia 9e Ch 53
- · Anesth Analg 2018 OLV Strategies Review