Tracheal Injury Prior to Sternotomy: A Cautionary Tale

Introduction

Sternotomy is routinely performed in cardiac surgery in order to allow access to the heart and mediastinal structures. Exposure to the sternum is facilitated through sharp dissection and electrocautery of subcutaneous tissue and periosteal fascia. This includes the division of the interclavicular ligament above the manubrium in the sternal notch. The interclavicular ligament overlies the proximal trachea (Figure 1). In this article, we describe a case of tracheal injury that occurred during electrocautery dissection of the subcutaneous and periosteal fascia prior to sternotomy. The incidence, mechanism, and ideal management of sternotomy-related tracheal injury, though a life-threatening complication, is rarely described in the literature.^1-7 The only other reported case with a confirmed similar mechanism of injury was repaired prior to the scheduled cardiac procedure. ¹ We describe the feasibility of completion of the cardiac procedure and repairing the tracheal injury after heparin reversal.

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Figure 1.

Anatomy of the superior mediastinum showing the interclavicular ligament and relation of the trachea to the posterior manubrium.

Case Report

A 63-year-old male with history of severe, multi-vessel coronary artery disease, nonischemic cardiomyopathy, peripheral vascular disease, and 45 pack-year smoking history presented for coronary artery bypass grafting (CABG). The preoperative airway and physical examination was notable for obesity (weighing 127 kg with a body mass index of 39.33 kg/m²).

Induction of general anesthesia was uneventful. The patient was intubated via direct laryngoscopy with an 8.0 mm Sheridan high-volume, tapered endotracheal tube (ETT; Teleflex Medical, Research Triangle Park, NC) in one attempt with a grade IIb Cormack-Lehane score; it was secured at 23 cm at the upper incisors. Mechanical ventilation was initiated with a minute ventilation of 6.5 L/min with 2 L/min of fresh gas flow. A transesophageal echocardiography (TEE) probe was placed without difficulty.

After sharp skin incision from the sternomanubrial junction to the xiphoid process with a number 15 scalpel blade, electrocautery (Bovie Medical Corporation, Clearwater, FL) was used to dissect the subcutaneous and periosteal fascia to the sternum. While dissecting the interclavicular ligament in the sternal notch superior to the manubrium (Figure 1), a sudden volume loss was noted on the ventilator. Gurgling was heard from the mouth and bubbling was noted at the superior aspect of the sternotomy incision. In verifying an intact circuit, the ETT pilot balloon was noted to be deflated and additional air added to the cuff immediately dissipated. No subcutaneous emphysema was noted. A tracheal injury was presumed and electrocautery was discontinued to minimize the fire risk. To aid with ventilation, the oropharynx was packed with 4 × 4 gauze around both the ETT and TEE probe with increased fresh gas flows and low-volume, low FiO₂ ventilation. Isoflurane was continued as the primary anesthetic as there was no evidence of significant residual leak after packing. There was no resultant hypoxia or hypercarbia with the lowest SpO₂ and highest EtCO₂ being 98% and 41%, respectively. The thoracic surgery team was called to the operating room for an intraoperative consult. An interdisciplinary discussion ensued and all agreed upon a plan to perform a bronchoscopic airway examination while on cardiopulmonary bypass (CPB) with a plan for ETT exchange at that time.

Once CPB was initiated, a flexible bronchoscopy confirmed a 3 mm full-thickness proximal tracheal burn approximately 7 cm above the carina (Figure 2). A decision was made to defer tracheal repair until after heparin reversal post CABG. An 11 French Cook Airway Exchange Catheter (Cook Medical, Bloomington, IN) was used to exchange the ETT. The ETT was advanced past the level of the tracheal injury, positioned above the carina via bronchoscopy, and the cuff was inflated. The old ETT was examined and found to have a thermal puncture approximating the size and shape of the Bovie tip in the cuff (Figure 3). The 4-vessel CABG proceeded without further complications.

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Figure 2.

Bronchoscopic image of the tracheal burn with bubble demonstrating air leak.

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Figure 3.

Damaged endotracheal tube demonstrating perforated cuff with burn marks.

After separating from CPB, administration of protamine (Fresnius Kabi, Lake Zurich, IL), and aortic and venous decannulation, the 3 mm tracheal injury was repaired with 0 Vicryl interrupted sutures and buttressed with strap muscles. The ETT was retracted to above the repair site, and no air leak was identified either on the ventilator or in the surgical field. The patient was transported to the intensive care unit in stable condition and extubated on postoperative day (POD) 1. He received standard postoperative antibiotics for 24 hours per institutional protocol without additional broad-spectrum coverage. He was discharged on POD 6 and had no pulmonary or mediastinal complications in follow-up visits out to 9 months.

Discussion

Sternotomy has been used as the primary exposure method for decades in cardiac surgery. Although often neglected, the proximity of the trachea to the sternum poses a significant risk for tracheal injury. Tracheal lacerations, including those related to cardiac surgery, pose a life-threatening complication, with morbidity and mortality estimates of up to 25% and 22%, respectively.^8,9 Symptoms and complications of tracheal injury include diffuse subcutaneous emphysema, hemoptysis, dyspnea, dysphonia, ventilator failure, airway obstruction, sepsis, mediastinitis, pneumothorax, pneumopericardium, and pneumomediastinum, which can be fatal if tension pneumothorax or tamponade physiology develop.^8,10

Causes may be either traumatic or iatrogenic by way of tracheal lacerations from bronchoscopy, mediastinoscopy, percutaneous or open tracheostomy, and laryngoscopy, particularly with the use of gum elastic endotracheal introducer (bougie) devices.^11,12 Tracheal rupture can occur during tracheal stenting or secondary to over-inflation of the ETT cuff in the setting of mechanical ventilation.^10,11 Inadvertent injury during thyroid, cardiac, and intrathoracic or transhiatal esophageal surgery have also been reported.^11,13 Both blunt and penetrating traumatic injuries may have concomitant esophageal involvement, which heightens the risk of sepsis and mediastinitis. ¹² Patients with proximal esophageal tumors status post neoadjuvant chemotherapy and radiation as well as patients with short, thick necks are high risk for tracheal injury during noncardiac procedures. ¹⁴

Iatrogenic tracheal laceration is reported in approximately 1/20,000 to 1/75,000 elective intubations with an overall reported incidence of 0.005% to 0.37% of intubations with a single lumen ETT and 0.05% to 1% of intubations with a double lumen ETT. ¹⁴ Of these, the incidence is higher by approximately 15% in those performed emergently. ¹⁴ Female and obese patients appear to be higher risk for laceration,^8,10 as are those with a short tracheosternal distance, which has been suggested to be those less than 19 mm. ⁶ Given the preponderance of obese patients in cardiac surgery, a heightened awareness of this complication is warranted. Likely partly due to their rarity, long diagnostic delays are frequently described (up to 66%, with a range of 1-72 hours to diagnosis), increasing the morbidity and mortality.^8,14

Tracheal injuries in the setting of sternotomy have only rarely been reported, with only 8 other cases in the current literature to our knowledge. Of these, only one was secondary to electrocautery, ⁴ 3 were from the sternal saw itself,^2-4 and 3 were of unconfirmed etiology after sternotomy.^5,6 The remaining case was from sharp dissection of the interclavicular ligament with scissors at which time tracheal rings were mistaken for the ligament and divided, emphasizing the proximity of the trachea to these structures (Figure 1). ⁷

Specific challenges exist when iatrogenic tracheal laceration occurs in the intraoperative setting, particularly when related to sternotomy with cardiac surgery. Surgical positioning with shoulder rolls, which cause neck extension and an anterior displacement of the trachea toward the manubrium, may predispose these patients to tracheal injury. ⁷ Likewise, dense adhesions due to a prior sternotomy or mediastinoscopy may increase the risk of difficult dissection, thus predisposing patients to injury. ³ While subcutaneous emphysema, pneumomediastinum, and pneumothoraces may be less likely to develop with an open chest, the inability to oxygenate and ventilate these already tenuous patients can be imminently life-threatening.

Similarly, an airway fire may result in disastrous consequences. Delayed diagnosis of intraoperative tracheal injury may easily occur if not alerted by obvious signs such as a large air leak or ruptured ETT cuff. While it is common practice to hold ventilation and deflate the lungs just prior to sternotomy, flow of oxygen through an unnoticed injury during the presternal dissection similarly predisposes the patient to airway fire. Therefore, we would suggest that FiO₂ should be kept as low as possible throughout sternal dissection and sternotomy to mitigate this risk. The distance from the trachea at the level of the sternal notch to the carinal trachea has been reported as 8.24 ± 1.16 cm, indicating that advancement of the ETT past the level of injury is a feasible option in most cases of a suprasternal tracheal injury. ¹⁵

Therefore, in the case of known tracheal injury, particularly in the setting of a ruptured ETT cuff, low FiO₂ ventilation is imperative until the ETT can be exchanged and the cuff advanced past the injury site. Until that time, we recommend throat packing while discontinuing electrocautery use.

Contamination from tracheal secretions may lead to postoperative mediastinitis or endocarditis when valves or other prostheses are subsequently inserted. However, no convincing evidence exists supporting the need to postpone the originally intended case for reason of infection. ⁵ Each of the previously described cases attempted tracheal repair prior to proceeding with the anticipated surgical procedure, with the exception of Takanami et al ² who aborted the initial procedure. At the time of this case, the existing literature was not known to us or our surgical colleagues and thus our collective decision was based on several factors. Although repair could have been performed prior to commencing CPB in our case, we preferred to wait until after reversal of anticoagulation to minimize airway bleeding risk and hematoma formation in the setting of muscle dissection for buttressing the repair. Likewise, given the theoretical infectious risk from further manipulation, particularly in that the electrocautery created a bloodless lesion, we felt delay was a reasonable approach. Additionally, since oxygenation and ventilation were not immediately compromised, we elected to wait until CPB had been initiated to perform a bronchoscopic examination and exchange the airway. This provided us the ability to examine the airway without the risk of hypoxemia while retracting and replacing the ETT. In the setting of profound respiratory compromise at the time of injury, we would also argue that the emergent use of CPB or extracorporeal membrane oxygenation (ECMO) to stabilize prior to repair would be arguably beneficial. Finally, though our repair occurred after decannulation from CPB, given that the sternum was still open with great vessels exposed, CPB or ECMO could have been reinitiated easily in the case of respiratory compromise during tracheal repair.

Multiple other options for treatment of such injuries exist for those without a surgically exposed trachea, ranging from conservative to surgical and endobronchial procedures. The standard of care for tracheal laceration has historically been tracheostomy or surgical repair via transcervical or thoracotomy approach, but many patients may be prohibitively high risk for surgery.^13,16,17 In rare circumstances, ECMO can be used to maintain oxygenation and ventilation during repair of a tracheal injury in patients without direct tracheal access at the time of noncardiac surgery. ¹⁸ Conservative therapies of broad spectrum antibiotics, airway humidification, and prolonged intubation are being increasingly endorsed as an alternative,^9,10,14,19 though its safety has been disputed ²⁰ and there remain no best practice guidelines for repair of tracheal injury. ⁸ Kayatta et al ⁵ have demonstrated that conservative management is possible when a tracheal injury cannot be repaired primarily. No consensus recommendations exist regarding the utility of broad spectrum antibiotics after primary repair, though our case demonstrates that this may not be necessary. The emerging practice of metal, silicone, and now polyurethane-coated nitinol stents with interval removal after healing poses a unique, less-invasive option for treatment.^21,22

Fortunately, in this case, the small 3 mm injury allowed for a simple primary repair, hence an early extubation on POD 1. However, in more severe cases, consideration may be given to a longer period of postoperative intubation and positioning patients in neck flexion position to maintain approximation of the wound. In some cases, placement of a Grillo stitch may be considered in discussion with surgical colleagues. Minimizing cough and agitation is also important. Alpha-2 agonists like dexmedetomidine (Pfizer, New York, NY) may be particularly helpful in these cases by maintaining patient comfort without impeding respiratory drive.

Beyond the acute postoperative and postinjury period during which the risk of mediastinitis, wound dehiscence, and air leaks are of concern, tracheal injury and repair are associated with late complications including tracheal stenosis and fistulous tracts. This population, therefore, merits interval follow-up to ensure freedom from these complications and a high index of suspicion should the patient present with dyspnea on exertion or stridor.

In summary, sternotomy-related tracheal injuries are rarely reported complications of cardiac surgery, which pose significant risk of morbidity and mortality. The cardiac surgery patient population, surgical positioning, and closely approximated suprasternal anatomy increase the risk of tracheal injury during sternotomy as well as delayed recognition and treatment in this population. No consensus exists regarding the optimal approach to and timing of such repairs, with no previous cases highlighting the possibility and benefits of delayed tracheal repair after separation from CPB. Anesthetic considerations for tracheal injury related to sternotomy are summarized in Table 1.

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Table 1.

Anesthetic Considerations for Tracheal Injury Related to Sternotomy.

Prevention

Understand the close spatial relationship between upper mediastinal structures (Figure 1)

Keep FiO2 as low as possible during soft tissue dissection and sternotomy

Take caution in obese and female patients as well as those with large shoulder rolls8,10

Short tracheosternal distance on CT may increase the likelihood (normal average is 19 mm) 6

More likely to happen with junior faculty and trainees 6

Variable presentation

Unrecognized

Subtle bubbling at site of laceration if distal to ETT

Audible air leak, volume loss/massive ventilator leak if ruptured ETT cuff

Subcutaneous emphysema, pneumothorax, or pneumomediastinum

Airway fire

Treatment

Decrease FiO2 to as low as possible

Consider throat packing

Discontinue electrocautery use

Have a multidisciplinary team discussion for risk-benefit assessment and management plan

Case completion: consider waiting for ETT exchange until on CPB versus immediate if acutely decompensating

Repair technique: conservative therapy (prolonged intubation, humidification, and antibiotics) versus minimally invasive stenting versus open repair

Timing of repair: prior to CPB versus after reversal of anticoagulation; discuss risk/benefits of aborting or delaying case if plans for prosthesis

Abbreviations: CT, computed tomography; ETT, endotracheal tube; CPB, cardiopulmonary bypass.