Background
A tracheal bronchus is a congenital anomaly in which an accessory bronchus originates from the trachea about 2 to 6 cm proximal to the carina. The prevalence of right tracheal bronchus is 0.1%-2% and left tracheal bronchus is 0.3-1%1,2. Although usually asymptomatic, tracheal bronchi can cause recurrent pneumonia, chronic bronchitis or bronchiectasis. Atelectasis due to obstruction caused by an endotracheal tube (ETT) has been reported3,4,5. We present a case of refractory intraoperative hypoxemia in an infant with an undiagnosed aberrant right upper lobe bronchus arising directly from the trachea.
Case Description
A 19 month-old previously healthy female infant presented with fulminant liver failure following ingestion of amanita mushrooms and underwent deceased donor liver transplantation. Her postoperative course was complicated by direct hyperbilirubinemia in the setting of bile duct dilatation seen on serial abdominal ultrasound. She was scheduled for exploratory laparotomy and biliary revision.
The patient was pre-oxygenated and anesthesia was induced with sevoflurane followed by fentanyl, propofol and rocuronium. She was intubated with a 3.5 mm cuffed ETT that was secured at 11 cm at the lip. Oxygen saturation progressively declined to the high 80s despite 100% O2 and diminished right upper breath sounds were noted. ETT was readjusted to 9 cm at the lip and recruitment breaths were delivered. Scant secretions were noted on ETT suctioning. Albuterol was given for mild upsloping of ETCO2 tracing, though no wheezing was noted. Intraoperative CXR revealed an ETT above the thoracic inlet and low lung volumes. ABG revealed a significant A-a gradient with PaO2 71 on 100%. Patient developed tachycardia and hypotension, which resolved with brief low-dose dopamine infusion. Oxygen saturation gradually increased above 95%, though she remained on 100% O2. The case was canceled due to persistent hypoxia of unknown etiology.
The patient was transported to the ICU without complications. Postoperative CXR revealed new mild right upper lobe atelectasis. A chest CT angiogram did not demonstrate any evidence of pulmonary embolism (PE) but a right upper lobe tracheal bronchus was diagnosed about 2 cm proximal to the carina.
Discussion
Significant difficulties in airway management and hemodynamic disturbances have been reported with tracheal bronchi3,4. Our patient had no known history of cardiac or pulmonary shunting, however she developed refractory intraoperative hypoxemia with a significant A-a gradient following intubation despite delivery of 100% O2. Given the lack of evidence suggesting a diagnosis of PE, mucous plugging, bronchospasm or pulmonary edema, we hypothesize that the initial ETT position may have obstructed the tracheal bronchus resulting in right upper lobe collapse. Subsequent ETT repositioning and recruitment breaths may have resulted in temporary resolution of her lobar collapse. As demonstrated in this case, chest radiograph may be normal despite the presence of a tracheal bronchus and chest CT will reliably establish the diagnosis. Flexible bronchoscopy is the gold standard for diagnosis and may be helpful intraoperatively for delineating anatomy and avoiding bronchial obstruction due to ETT positioning. Although uncommon, anesthesiologists should consider a diagnosis of a tracheal bronchus in intubated patients with unexplained refractory hypoxemia.
