The role of tracheostomy continues to evolve in critically ill patients. The improved design of endotracheal tubes and careful attention to sedation has minimized the traumatic consequences of intubation, making translaryngeal intubation for weeks both safe and tractable. On the other side, the improved techniques for performing tracheostomy, and the increasing ability to perform tracheostomy at the bedside has made tracheostomy safer and more available than it has been previously. Tracheostomy continues to have immediate and long-term complications that intensivists manage.
Indications for Tracheostomy
The least controversial indication for tracheostomy is upper airway obstruction, especially long-term or permanent airway obstruction. Tracheostomy is also widely accepted as preferable to transglottic intubation for long-term mechanical ventilation. Tracheostomy is also indicated when a patient will be unable to clear their airway secretions for a long period of time. Finally, tracheostomy is frequently used to facilitate liberation from mechanical ventilation.
Tracheostomy has several benefits in patients who will require long-term mechanical ventilation. It allows easier and safer access to the mouth, which allows improved oral hygiene. It is substantially more comfortable than translaryngeal intubation, so the need for both analgesics and sedation may be significantly reduced. Specially designed tracheostomy tubes allow for speech and even normal eating in patients who are either continuously or intermittently ventilated. There was a time when patients underwent tracheostomy after only very brief periods of translaryngeal intubation and mechanical ventilation (e.g., 7 to 10 days). The decision to perform a tracheostomy on a patient in these circumstances should not be motivated as much by the time that has already elapsed on mechanical ventilation, but rather by the amount of time it can be foreseen that they will require mechanical ventilation. If the patient will obviously require ventilation for the coming weeks, then it is quite reasonable to perform a tracheostomy for both their safety and comfort.58,59 Patients at high risk of the complications of translaryngeal intubation, such as diabetics, may benefit from earlier tracheostomy.
Tracheostomy has the great benefit of reducing the anatomic dead space, resulting in substantially greater alveolar ventilation for any given minute ventilation. This benefit may be of critical importance in patients whose strength is very closely matched to their requirement for minute ventilation, and who might not otherwise be easy to liberate from the ventilator. The ease of reinstituting mechanical ventilation, and the wide bore and short length of tracheostomy tubes are also of benefit in these circumstances.
Percutaneous versus Surgical Tracheostomy
There is a large and growing literature which clearly demonstrates that percutaneous and surgical tracheostomy are equally successful and safe in competent hands.60–62 Interestingly, the sum of the patients in all of the prospective studies published thus far is less than 600, limiting the statistical power of inferences about rare complications, such as death, pneumothorax, and posterior tracheal wall perforation, but certainly allowing the conclusion that the success rates and overall complication rates of the two procedures are very similar. Mortality of either procedure is now less than 1%, which is significantly lower than that reported in older literature. When performed at the bedside in the ICU, both percutaneous and surgical tracheostomy are significantly less expensive and easier to arrange than tracheostomy in the operating room. The difference in cost between the two procedures performed at the bedside is small, and likely to be outweighed by other institutional factors and considerations.
A variety of techniques for percutaneous tracheostomy have been described and are in widespread use. Briefly, after appropriate sedation, the patient's neck is extended to open the tracheal interspaces. The skin over tracheal interspaces below the cricoid cartilage is then anesthetized, prepped with an appropriate cleansing agent, and draped in the usual sterile fashion. A 2-cm horizontal incision is made, and the neck is bluntly dissected down to the trachea. The existing tracheal tube is then withdrawn to a position just below the vocal cords. A needle is then inserted into the trachea (usually under bronchoscopic guidance), and a wire threaded into the tracheal lumen. The tract is then mechanically dilated, and an appropriately sized tube inserted into the trachea. Commercially available kits are now available that replace multiple dilators with a single dilator (e.g., Blue Rhino PDT from Cook Critical Care, Bloomington, IN), which may save time and reduce the risk of the procedure as well. Two of the advantages of the percutaneous technique are the minimal sharp dissection involved, and the use of dilation to create the tract for the tracheostomy tube, both of which limit the bleeding associated with the procedure.
The literature about percutaneous tracheostomy clearly documents that it can be accomplished successfully and safely in the hands of competent practitioners. Some techniques incorporate bronchoscopic guidance, incurring additional expense, time delay, and need for additional operators to provide some increase in the safety of the procedure. Although simultaneous bronchoscopy is advocated by some authorities, many more experienced operators rarely if ever use it to facilitate the procedure. The speed with which percutaneous tracheostomy without the use of a bronchoscope can be accomplished is impressive, making it attractive as a procedure to emergently secure the obstructed airway in institutions with readily available kits and highly skilled operators. Morbid obesity and previous tracheostomy are frequently cited contraindications to percutaneous tracheostomy, but there are case series which suggest that the procedure can be performed safely in select patients with either diagnosis.63,64 There is no doubt that as with any other procedural skill, there is and will be significant variation across practitioners and institutions, which makes prescriptions about percutaneous tracheostomy inappropriate.
Minitracheostomy is a procedure that is sometimes performed in select critically ill patients to facilitate clearance of bronchial secretions.65 Minitrach allows repeated suctioning of the trachea below the cords without passing a tube through them at the cost of undergoing the procedure (which is generally performed at the bedside) with its attendant complications. The procedure itself is very similar to that described for percutaneous tracheostomy, except that it does not result in an airway. Minitracheostomy has been demonstrated to reduce the incidence of radiographic collapse, but has not otherwise been proven to improve outcomes.66,67 Minitracheostomy is commonly done at some centers, rarely done at most, and never done at others. This is unlikely to change unless studies demonstrating more dramatic benefit to the procedure are published.
Complications of Tracheostomy
The immediate complications of tracheostomy include hemorrhage, malpositioning of the tracheostomy tube, and pneumothorax/pneumomediastinum. Hemorrhage can occur as a consequence of bleeding from subcutaneous vessels, neck veins, and the thyroid gland. Most postoperative bleeding is venous in origin, and it may take hours for a noticeable hematoma to form. A hematoma in the neck can compress the trachea or cause it to deviate, resulting in increased airway pressures, a sensation of dyspnea on the part of the patient, and hypoventilation. Airway obstruction caused by a hematoma is best treated by decompression/evacuation, as all other therapies will fail to interrupt the cascade of events leading to deterioration and will allow the underlying process to progress.
Rarely, tracheostomy tubes may be placed into tissue planes in the neck instead of the trachea. Monitoring end-tidal carbon dioxide concentrations after the tube is inserted will aid in the timely recognition of this problem, allowing it to be quickly corrected. Tracheal positioning of the tracheostomy tube can be verified with auscultation, capnography, and fiberoptic bronchoscopy.
Pneumothorax and pneumomediastinum are consequences of invasion of these tissue planes, which can extend superiorly into the neck in some patients (particularly those with chronic obstructive pulmonary disease or on high amounts of PEEP). These complications are more likely to occur in situations in which the anatomy is difficult, such as patients with morbid obesity, previous neck surgery, or goiter. These complications are usually recognized on the routine chest radiograph taken postoperatively in these patients to confirm adequate positioning of the new tracheostomy tube.
Long-Term Complications of Tracheostomy
Tracheostomy tubes are frequently left in patients for months and occasionally years. This situation puts the patient at risk of complications due to chronic irritation or erosion of the trachea, including tracheoesophageal fistula, tracheoinnominate fistula, tracheomalacia, and tracheal stenosis.
The absence of a large epidemiologic database, the heterogeneity of patient populations undergoing tracheostomy in the ICU, and the high mortality in some patient populations that undergo the procedure make discussion of the complications of tracheostomy difficult.68 Tracheal stenosis is diagnosed in 40% to 60% of patients who have undergone tracheostomy, but it is unclear if this is a complication of their tracheostomy or their prior transglottic tracheal intubation.69,70 The high cuff pressures thought to be the major cause of the tissue injury that drives this process are more likely to be present during the early, acute phase of critical illness, when high airway pressures are present.71 On the other hand, the disruption of the tracheal cartilages caused by the presence of the tracheostomy tube may lead to instability, which may in turn cause tissue injury, which may be worsened by the immune response to both the tracheostomy tube and the purulent secretions that contaminate its tract. Given this, it is unsurprising that a majority of the tracheal stenoses attributed to tracheostomy occur at the level of entry into the trachea.
Tracheoinnominate fistula occurs in less than 1% of patients, typically within 1 month of undergoing insertion of a low-lying tracheostomy. Either the tip of the tube or its cuff erodes through the wall of the trachea and into the vessel, causing life-threatening bleeding which requires immediate surgical repair. Tracheoesophageal fistula occurs via the same mechanism, but entails erosion through the posterior wall of the trachea into the esophagus. Tracheoesophageal fistula is frequently difficult to diagnose, as it can present as recurrent pneumonia in a ventilated patient. Other more obvious symptoms include cuff leak refractory to inflation, aspiration of large quantities of tube feeds in spite of an appropriately inflated tracheostomy cuff, and gastric distention with large quantities of air. The diagnosis of a tracheoesophageal fistula can be established with either barium swallow or computed tomography scan. Treatment is usually surgical, although a variety of stents have been employed as an alternative.72