Anesthetic Considerations

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CHAPTER 3 Anesthetic Considerations

Karen S. Sibert, Robert A. Frantz

Introduction

Anesthesia for minimally invasive thoracic surgery involves many of the same techniques that anesthesiologists use for open thoracic procedures. Successful anesthetic management includes several components:

♦ Facility with placement and adjustment of right- and left-sided double-lumen endotracheal tubes (DLTs)

♦ Knowledge of tracheobronchial anatomy and skill with fiberoptic bronchoscopy

♦ Expertise with thoracic epidural analgesia

♦ Anesthesiologists dedicated to providing anesthesia for thoracic cases

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.

♦ If the patient is on bronchodilator therapy, provide treatment in the preoperative area.

♦ Discuss postoperative pain management, including the possibility of epidural analgesia.

♦ 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.

♦ A single, reliable, 18-gauge intravenous catheter is adequate for many minimally invasive cases.

♦ Radial artery catheters are placed for most cases unless the patient is especially healthy or the anticipated procedure is brief.

♦ Central venous access is required less frequently unless intravenous access is limited or substantial blood loss is anticipated; central lines are routinely placed for pneumonectomy, esophagectomy, and lung volume reduction surgery.

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 use of a video laryngoscope permits full visualization of the DLT tip as it passes between the vocal cords.

Routine Intubation

We developed a 5-step process for passage of the DLT into the larynx, most often with the use of a Mac 4 video laryngoscope.

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.

b. If the tip of the bronchial lumen impinges on the anterior or lateral laryngeal structures (i.e., anterior commissure) or the arytenoid cartilages, gently redirect or rotate the tube to guide the tip past the obstacles. It may be helpful to retract the stylet.

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.

Figure 3-1 Insertion of a soft-tipped exchange catheter into the trachea facilitates passage of a double-lumen endotracheal tube in a patient with a difficult airway.

Achieving Optimal DLT Placement

♦ Correct placement of a DLT can be achieved in one of two accepted ways:

• Insert the DLT into the trachea, and use fiberoptic bronchoscopy (FOB) to direct the tube down the appropriate mainstem bronchus.

• Insert the DLT to an estimated appropriate depth in the mainstem bronchus during the initial laryngoscopy (our usual practice), and use FOB to confirm placement and adjust the tube position as necessary.

Choice of Right versus Left DLT

In many institutions, left DLTs are used for all thoracic cases because of the perceived difficulty in situating right-sided tubes properly to ventilate the right upper lobe (RUL). We disagree; we routinely use right DLTs for most left lung cases, and left DLTs for all right lung cases. There are multiple advantages to this approach:

♦ 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.

♦ Always repeat fiberoptic bronchoscopy after lateral positioning to confirm proper tube placement.

♦ 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.

♦ After the patient is positioned laterally, the alignment of the RUL orifice on a right DLT may be altered. It may be difficult to regain perfect alignment, but the SaO₂ often is not adversely affected.

Related

Atlas of Minimally Invasive Thoracic Surgery (Vats)