Lesions near the carina add some new challenges to the process of the tracheal resection and reconstruction discussed above.28,29 The procedure is intrathoracic, usually approached from a thoracotomy, and the lungs cannot be treated as a single entity. As in all thoracotomies, arterial monitoring is prudent and methods of postoperative analgesia, such as thoracic epidural catheters, are needed.
The considerations for induction of anesthesia are similar to those for surgery for higher lesions, although it is even more clear that surgical access to the airway, in the case of a complete obstruction, is not an option. Some authors suggest veno-venous bypass as a fallback technique.30 Severely obstructing tumor at the carina may be cored out bronchoscopically to provide an adequate initial airway (see Chapter 19, "Urgent Treatment of Tracheal Obstruction"). Once the bronchoscopic examination is completed, it is time to intubate the trachea. There are several options. If the airway is not too compromised, then the tube can sit above the lesion. The trachea will often be approached via thoracotomy, and the airway entered. Exposure cannot be assisted by collapse of the lung unless a blocker is passed into the surgical side. If the bronchus is already damaged, a blocker would be unwise, so small tidal volumes and some effort from the surgeon's assistants are required. Once the trachea is entered, a tube is passed on the field into the opposite mainstem bronchus, and single-lung ventilation is employed.
Some lesions are better addressed by a distal intubation from the start. Since the lesion is at or beyond the carina, the only option is endobronchial intubation (Figure 18-2). An endobronchial tube is chosen instead of a standard double-lumen tube, because the double-lumen tube is too bulky to permit tracheal surgery. Long flexible tubes of small diameter but sufficient length (>31 cm) to reach the bronchus are not currently widely available. It is possible to easily construct them by combining two tubes. An example is shown in Figure 18-3, using a Phycon, a silicone armored cuffed tube with its integral collar, and a length of standard PVC tubing placed in the collar with a friction fit. The lumen stays a constant diameter and the tube has the desirable properties of being more stiff in the upper portion and flexible and nonkinking in the lower portion. Note that the tip design in endobronchial tubes is important. There is not a long segment of bronchus in which the cuff and distal portion may sit, so a shorter cuff-to-end design is preferable. Trimming the end of an endotracheal tube will make the cuff incompetent since the cuff air channel runs beyond the cuff. The endobronchial tube is positioned under fiber-optic guidance. The jury-rigged nature of these tubes, as well as the extensive surgical manipulation of the region, causes frequent tube malpositioning. A fiberscope should be constantly at hand, as the anesthesiologist will be required to make frequent corrections as the operation proceeds.
Other creative endobronchial tubes have been fashioned by trimming the distal portion of the tracheal lumen off a double lumen (destroying the tracheal cuff), as shown in Figure 18-4. This leaves a single lumen in the distal trachea that ends in the bronchus. The endobronchial lumen is well designed for the bronchus, especially the right mainstem bronchus. The abbreviated tracheal lumen is in fact quite useful, allowing introduction of a fiber-optic bronchoscope, jet catheter, bronchial blocker, or oxygen insufflation. This modified double-lumen tube is less satisfactory, however, in greatly distorted airways, since the contour is designed for normal anatomy and has no protection against kinking once warmed and bent.
With endobronchial intubation, one lung will not be ventilated. As in all thoracotomies, the level of shunt and desaturation is variable and unpredictable. Standard maneuvers include suctioning, confirming
position, increasing FiO2, and varying the ventilatory patterns. Unlike many thoracotomies, it is not as easy to administer ventilation to the deflated lung. While the airway is intact, deflating the endobronchial cuff, blocking the mouth and nose, and delivering longer and larger tidal volumes can help. Alternatively, placing another endotracheal tube high in the trachea (ie, two endotracheal tubes, of small diameter) can allow differential ventilation, or at least constant positive airway pressure (CPAP). Another approach is to place an LMA after the endobronchial tube, and if it seals sufficiently, CPAP can then be administered. Finally, a jet catheter can be placed in the trachea. Indeed, a technique using two jet catheters has been described.31 The jet catheter has the advantage of not requiring a seal, but may not be effective if there is substantial distal obstruction. In extreme circumstances, blood flow to the pulmonary artery can be restricted, lessening shunt.
Once the airway is open, CPAP cannot be administered from above. A second tube can be placed from the field into the deflated lung, or a jet catheter can be used (see Figure 18-2c). The jet catheter has the advantage of being small enough to allow surgery to proceed, of not requiring an entire circuit, and that the length that needs to be placed in the trachea is very small. Since large tidal volumes are not needed on the surgical side, the force and mess of jetting is less.
The conduct of one-lung ventilation for carinal surgery requires all the considerations given to conventional pulmonary resection. Care with airway pressures and avoidance of overdistention are
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