CHAPTER 3 Anesthetic Considerations
Introduction
♦ Facility with placement and adjustment of right- and left-sided double-lumen endotracheal tubes (DLTs)
Patient Preparation and Monitoring
♦ Most patients are moderate to high anesthesia risks (i.e., American Society of Anesthesiologists [ASA] physical status class 3), and abnormal pulmonary function test results are expected.
♦ Reassuringly prepare the patient to anticipate that breathing will be uncomfortable on waking due to the effect of chest tubes and lung reexpansion.
♦ Patients who have had neoadjuvant radiation therapy or chemotherapy must be identified in advance and kept on the lowest acceptable FIO2 because they are more susceptible to hyperoxic lung injury.
♦ Radial artery catheters are placed for most cases unless the patient is especially healthy or the anticipated procedure is brief.
Double-Lumen Endotracheal Tube Placement
Applications
♦ DLTs are required for most thoracic cases: wedge resection, lobectomy, pneumonectomy, lung reduction, pleurodesis, decortication, and esophagectomy.
♦ They are not required for mediastinoscopy, sympathectomy, or pericardial window (i.e., subxyphoid approach).
♦ We exclusively use DLTs for any procedure requiring lung separation. Bronchial blockers do not allow adequate deflation or suctioning of the operated lung.
Routine Intubation
1. Insert the Mac blade into the right side of the mouth, and use the flange to sweep the tongue over to the left.
2. Advance the tip of the blade into the vallecula, and elevate the blade to reveal the vocal cords. In some patients, the view improves with the tip of the blade beneath the epiglottis.
3. Bend or curve the DLT at an angle of 30 to 45 degrees about 6 to 8 cm from the tip, and insert it from the right side of the mouth so that the tip approaches the vocal cords.
4. Depending on the relationship of the bronchial tip and the surrounding structures, one of two approaches is necessary:
a. If the alignment is suitable (with or without the stylet in place), pass the DLT beyond the vocal cords into the mid-trachea.
5. Because the DLT is often anteriorly directed at this stage, the leading edge may catch on the tracheal rings, preventing advancement of the tube. Additional gentle rotation and pressure may be necessary to “screw” the DLT into the mid-trachea, and it may be necessary to pass a fiberoptic bronchoscope through the bronchial lumen to help guide the DLT tip through the tracheal rings and into the appropriate bronchus.
Difficult Intubation
♦ Use of a DLT exchange catheter facilitates placement of a DLT in patients with an anterior larynx, limited aperture, or other difficult airway situations (Figure 3-1). The exchange catheter may be guided into the trachea using direct video laryngoscopy or advanced through a previously placed single-lumen endotracheal tube. The DLT is then passed over the catheter into the trachea. Care must be taken to pass the exchange catheter tip gently just past the vocal cords to avoid tracheal injury.
♦ Another safe approach to the difficult airway is to insert a fiberoptic bronchoscope into the trachea and pass the DLT directly over it. Maneuvers including jaw thrust, tongue retraction, and simultaneous laryngoscopy facilitate passage of the tube through the laryngeal inlet.
Achieving Optimal DLT Placement
Choice of Right versus Left DLT
♦ There is no risk of inadvertently stapling the cuff of a left DLT during left lobectomy or pneumonectomy.
♦ A complete view of the carina and the mainstem bronchus of the operated lung is obtained during bronchoscopy.
♦ Bronchoscopy through the tracheal lumen to check the distal cuff position does not interrupt ventilation of the nonoperated lung.
♦ If the tracheal (proximal) cuff is damaged by the patient’s teeth during insertion, lung isolation is still accomplished by the intact distal cuff.
♦ If a left DLT is used for left lung surgery, it is possible for pressure on the operated lung to occlude the tracheal lumen, which is ventilating the right lung, or to push the bronchial cuff back into the trachea.
♦ Right DLTs are easy to insert because the path to the right mainstem bronchus is more direct. A contralateral tube is imperative when a sleeve resection is performed (e.g., if a left-sided tube is used when the left mainstem bronchus is open during a bronchial sleeve), the tube interferes with suturing and the patient is not ventilated well.
Troubleshooting after Initial Insertion
♦ In 5% to 10% of cases, a left DLT goes down the right mainstem bronchus, despite the usual leftward rotation, as it is advanced. Withdraw the tube into the trachea, and advance it into the left bronchus under direct FOB vision.
♦ When the patient is turned lateral and flexed, the DLT usually retracts cephalad at least a centimeter and may need to be advanced to avoid herniation of the distal cuff over the carina. This is especially likely in edentulous patients. It is always easier to pull a DLT back than to advance it after it has become warm and flexible.
♦ Hypoxemia is usually a sign of an improperly placed tube; we rarely find it necessary to use continuous positive airway pressure (CPAP) for the operated lung or positive end-expiratory pressure (PEEP) greater than 5 cm to the nonoperated lung. During lobectomy, the oxygen saturation always improves after clamping of the arterial blood supply to the lobe.
♦ With a right DLT, if the distance to the takeoff of the RUL bronchus is very short, the distal cuff may herniate over the carina. In this event, connect the FOB to suction, and pass it down the left mainstem bronchus to deflate the left lung.
