The causes of adult tracheal stenosis are trauma, chronic inflammatory diseases, benign neoplasm, malignant neoplasm and collagen vascular diseases. The most common cause of tracheal stenosis continues to be trauma, which can be internal (prolonged endotracheal intubation, tracheotomy, flame burn injury) or external (blunt or penetrating neck trauma) (Chao et al., 2005
). Therapeutic strategies for these patients include surgical resection combined with appropriate reconstruction and interventional bronchoscopic procedures (dilation, laser tracheoplasty, and tracheobronchia stent) (Gaissert et al., 2006
; Bolliger et al., 2006
), but each has its own merits and limitations. For a short (<1 cm), membranous stenosis without damage to the cartilages, laser incisions followed by gentle dilatation or tracheal stent is the safe and complete treatment. But for complex tracheal stenosis, longer with circumferential hourglass-like contraction, scarring or malacia, surgical sleeve resection and end-to-end anastomosis are considered the standard curative treatment (Vergnon et al., 2000
). Laser tracheoplasty under bronchoscopic guidance has been proposed as a reliable method for treating benign tracheal tumors. However, if a tumor almost occludes the airway and causes severe respiratory insufficiency, any manipulation of the airway would precipitate increased oxygen consumption leading to further hypoxia and probable cardiac arrest. After careful consultation, we believed that laser tracheoplasty or tracheal stent would be unsuccessful for our two patients with critical tracheal stenosis, therefore we decided to carry out emergent surgery just under cardiopulmonary bypass.
The symptoms of central airway stenosis are distressing. Generally, when the patient presents stridor and tachypnea, the tracheal stenosis has reached about 50% of the tracheal diameter. When the patient has extreme respiratory insufficiency the tracheal stenosis has reached a critical level of 75% or more. For the latter, surgery and the anesthetic airway management are very difficult. Besides the degree of tracheal stenosis, the stenosed position is also important for anesthesia. For upper tracheal stenosis, a tracheal tube can be inserted below the stenosis under local anesthesia or cervical nerve block; for mild mid-level tracheal stenosis, a small tracheal tube can be inserted past the stenosis by the help of fiberoptic scope; for severe mid-level tracheal stenosis, a tracheal tube can be intubated rapidly above the stenosis first, then a smaller aseptic tracheal tube is placed in the main bronchus by the surgeon and single lung ventilation applied to maintain oxygenation during surgery. After tracheoplasty, the main bronchus tube is removed and a tracheal tube is placed at a suitable level. For the most severely obstructed patients with critical tracheal stenosis and at risk for complete respiratory failure at any time, conventional anesthetic technique would be catastrophic if attempts are made to insert a small tube which may cause complete obstruction of the airway. In many of these patients, the anatomy of the stenosis is such that they can only ventilate when breathing spontaneously.
Blind anesthesia induction and intubation can depress the patient’s auto-compensation, which could result in severe consequence of cardiac and respiration arrest, especially in patients who have had hypoxia because of the increase in oxygen consumption (Mentzelopoulos et al., 1999
). How to establish safe and efficient gas exchange is the key to the successful management of the patients with critical tracheal stenosis and to survival. It is reported that cardiopulmonary bypass is widely used in non-cardiac operations (Belmont et al., 1998
; Chuqhtai et al., 2002
; Goh et al., 1999
). It could allow gas exchange and good surgical access for the tracheal operations and avoid aggravating hypoxia and carbon dioxide accumulation which may result in cardiac arrest during normal anesthesia and tracheal intubation.
Our two patients were both with critical lower tracheal stenosis which required extraordinary anesthetic techniques. We inserted a tracheal tube up the stenosis for the first patient, but high airway pressure and severe hypercarbia developed (the PaCO2 reached 130 mmHg). Extracorporeal circulation was initiated with cannulation in the femoral artery and femoral vein immediately. To that patient, extracorporeal circulation was a lifesaving method. For the second patient, we drew lessons from the first case, established femoral-femoral cardiopulmonary bypass prior to induction of anaesthesia under local anesthesia, then intubated above the tracheal tumor orally under general anesthesia induction. After the surgeons had resected the tracheal stenosis and reconstructed the trachea with the support of normothermic extracorporeal circulation, we adjusted the tracheal tube depth to allow two lungs ventilation and then weaned the patient from cardiopulmonary bypass.
Although bypass may be the only safe and practical method of induction and maintenance of anesthesia for operation on the trachea if the lumen diameter is compromised severely (Mentzelopoulos et al., 1999
; Belmont et al., 1998
), systemic anticoagulation increases the risk of bleeding postoperatively especially for those patients who need extensive dissection and a prolonged time of extracorporeal circulation. In our first case, the patient required a second operation to be performed because of incision bleeding 48 h after the first operation.
In summary, surgical resection is lifesaving for the patients with critical lower tracheal stenosis and how to ensure effective gas exchange is crucial to the anesthetic management. Extracorporeal circulation by the femoral artery and femoral vein cannulation is an effective method of gas exchange even if the trachea is totally obstructed. Before the induction of anesthesia, the site and degree of obstruction should be carefully assessed and the set up for cardiopulmonary bypass should be considered to avoid exposing the patient to increased risks of conventional anesthesia.