Use of One-Lung Ventilation for Thoracic Surgery 洪明輝 台大醫院 麻醉部

Objectives Indication/contraindication of OLV Physiology changes of OLV Selection of the methods for OLV Management of common problems associated with OLV, especially hypoxemia

Introduction One-lung ventilation, OLV, means separation of the two lungs and each lung functioning independently by preparation of the airway OLV provides: Protection of healthy lung from infected/bleeding one Diversion of ventilation from damaged airway or lung Improved exposure of surgical field OLV causes: More manipulation of airway, more damage Significant physiologic change and easily development of hypoxemia

Indication Absolute Isolation of one lung from the other to avoid spillage or contamination Infection Massive hemorrhage Control of the distribution of ventilation Bronchopleural fistula Bronchopleural cutaneous fistula Surgical opening of a major conducting airway giant unilateral lung cyst or bulla Tracheobronchial tree disruption Life-threatening hypoxemia due to unilateral lung disease Unilateral bronchopulmonary lavage

Indication (continued) Relative Surgical exposure ( high priority) Thoracic aortic aneurysm Pneumonectomy Upper lobectomy Mediastinal exposure Thoracoscopy Surgical exposure (low priority) Middle and lower lobectomies and subsegmental resections Esophageal surgery Thoracic spine procedure Minimal invasive cardiac surgery (MID-CABG, TMR) Postcardiopulmonary bypass status after removal of totally occluding chronic unilateral pulmonary emboli Severe hypoxemia due to unilateral lung disease

Physiology of the LDP Upright position LDP, lateral decubitus position

Physiology of LDP Awake Closed chest Anesthetized . V Q V Q V Q ND       D      

Summary of V-Q relationships in the anesthetized, open-chest and paralyzed patients in LDP

Physiology of OLV The principle physiologic change of OLV is the redistribution of lung perfusion between the ventilated (dependent) and blocked (nondependent) lung Many factors contribute to the lung perfusion, the major determinants of them are hypoxic pulmonary vasoconstriction, HPV and gravity.

HPV HPV, a local response of pulmonary artery smooth muscle, decreases blood flow to the area of lung where a low alveolar oxygen pressure is sensed. The mechanism of HPV is not completely understood. Vasoactive substances released by hypoxia or hypoxia itself (K+ channel) cause pulmonary artery smooth muscle contraction HPV aids in keeping a normal V/Q relationship by diversion of blood from underventilated areas, responsible for the most lung perfusion redistribution in OLV HPV is graded and limited, of greatest benefit when 30% to 70% of the lung is made hypoxic. But effective only when there are normoxic areas of the lung available to receive the diverted blood flow

Factors Affecting Regional HPV HPV is inhibited directly by volatile anesthetics (not N20), vasodilators (NTG, SNP, dobutamine, many ß2-agonist), increased PVR (MS, MI, PE) and hypocapnia HPV is indirectly inhibited by PEEP, vasoconstrictor drugs (Epi, dopa, Neosynephrine) by preferentially constrict normoxic lung vessels

Gravity and V-Q Upright LDP

Shunt and OLV Physiological (postpulmonary) shunt About 2-5% CO, Accounting for normal A-aD02, 10-15 mmHg Including drainages from Thebesian veins of the heart The pulmonary bronchial veins Mediastinal and pleural veins Transpulmonary shunt increased due to continued perfusion of the atelectatic lung and A-aD02 may increase

Two-lung Ventilation and OLV

Methods of OLV Double-lumen endotracheal tube, DLT Single-lumen ET with a built-in bronchial blocker, Univent Tube Single-lumen ET with an isolated bronchial blocker Arndt (wire-guided) endobronchial blocker set Balloon-tipped luminal catheters Endobronchial intubation of a single-lumen ET

DLT Type: Carlens, a left-sided + a carinal hook White, a right-sided Carlens tube Bryce-Smith, no hook but a slotted cuff/Rt Robertshaw, most widely used All have two lumina/cuffs, one terminating in the trachea and the other in the mainstem bronchus Right-sided or left-sided available Available size: 41,39, 37, 35, 28 French (ID=6.5, 6.0, 5.5, 5.0 and 4.5 mm respectively)

Left DLT… Most commonly used The bronchial lumen is longer, and a simple round opening and symmetric cuff Better margin of safety than Rt DLT Easy to apply suction and/or CPAP to either lung Easy to deflate lung Lower bronchial cuff volumes and pressures Can be used Left lung isolation: clamp bronchial + ventilate/ tracheal lumen Right lung isolation: clamp tracheal + ventilate/bronchial lumen

…Left DLT More difficult to insert (size and curve, cuff) Risk of tube change and airway damage if kept in position for post-op ventilation Contraindication: Presence of lesion along DLT pathway Difficult/impossible conventional direct vision intubation Critically ill patients with single lumen tube in situ who cannot tolerate even a short period of off mechanical ventilation Full stomach or high risk of aspiration Patients, too small (<25-35kg) or too young (< 8-12 yrs)

Univent Tube... Developed by Dr. Inoue Movable blocker shaft in external lumen of a single-lumen ET tube Easier to insert and properly position than DLT (diff airway, C-s injury, pedi or critical pts) No need to change the tube for postop ventilation Selective blockade of some lobes of the lung Suction and delivery CPAP to the blocked lung

...Univent Tube Slow deflation (need suction) and inflation (short PPV or jet ventilation) Blockage of bronchial blocker lumen Higher endobronchial cuff volumes +pressure (just-seal volume recommended) Higher rate of intraoperative leak in the blocker cuff Higher failure rate if the blocker advanced blindly

Arndt Endobronchial Blocker set Invented by Dr. Arndt, an anesthesiologist Ideal for diff intubation, pre-existing ETT and postop ventilation needed Requires ETT > or = 8.0 mm Similar problems as Univent Inability to suction or ventilate the blocked lung

Other Methods of OLV Single-lumen ETT with a balloon-tipped catheter Including Fogarty embolectomy catheter, Magill or Foley, and Swan-Ganz catheter (children < 10 kg) Not reliable and may be more time-consuming Inability to suction or ventilate the blocked lung Endobronchial intubation of single-lumen ETT The easiest and quickest way of separating one lung from the other bleeding one, esp. from left lung More often used for pedi patients More likely to cause serious hypoxemia or severe bronchial damage

Management of OLV... Initial management of OLV anesthesia: Maintain two-lung ventilation as long as possible Use FIO2 = 1.0 Tidal volume, 10 ml/kg (8-12 ml/kg) Adjust RR (increasing 20-30%) to keep PaCO2 = 40 mmHg No PEEP (or very low PEEP, < 5 cm H2O) Continuous monitoring of oxygenation and ventilation (SpO2, ABG and ET CO2)

...Management of OLV If severe hypoxemia occurs, following steps be taken Check DLT position with FOB Check hemodynamic status CPAP (5-10 cm H2O, 5 L/min) to nondependent lung, most effective PEEP (5-10 cm H2O) to dependent lung, least effective Intermittent two-lung ventilation Clamp pulmonary artery ASAP Other causes of hypoxemia in OLV Mechanical failure of 02 supply or airway blockade Hypoventilation Resorption of residual 02 from the clamped lung Factors that decrease Sv02 (CO, 02 consumption)

Broncho-Cath CPAP System

Summary OLV widely used in cardiothoracic surgery Many methods can be used for OLV. Each of them have advantages + disadvantages. Optimal methods depends on indication, patient factors, equipment, skills + training FOB is the key equipment for OLV Principle physiologic change of OLV is the redistribution of pulmonary blood flow to keep an appropriate V/Q match Management of OLV is a challenge for the anesthesiologist, requiring knowledge, skill, vigilance, experience, and practice