Since its first report in 1971 [1], prognosis after Fontan surgery has improved through progress in surgical techniques and advances in perioperative management, with a 10-year post-operative survival rate of 95% [2]. However, various complications have been reported following surgery in the long term, such as heart failure, tachyarrhythmia, thromboembolism, pulmonary arteriovenous fistula, liver cirrhosis, protein-losing gastroenteropathy, and PB [3].
In PB, high central venous pressure inhibits lymphatic fluid drainage through the thoracic duct. As a result, the lymphatic fluid leaks into the bronchi and produces mucus plugs, which can form bronchial casts [4, 5]. These mucus plugs cause respiratory failure due to tracheobronchial tract obstruction, occasionally resulting in mortality. The incidence of PB is relatively rare (around 4%) [6]; however, its prognosis is poor, with a 5-year mortality of approximately 50% [7]. In the long term, therefore, PB is one of the most life-threatening complications of Fontan surgery.
Today, there are no established treatments for PB. Typically, treatments to improve cardiac function, fat-restricted diets, physical therapy, and pharmacotherapy are performed. In pharmacotherapy, expectorants, antibiotics, bronchodilators, steroids, heparin, and thrombolytics are used [8, 9]. When resistance to pharmacotherapy occurs, invasive treatments are performed, such as transcatheter intrapulmonary lymphatic embolization of intrapulmonary lymphatic vessels [10, 11], surgical thoracic duct ligation [12, 13], fenestration reopening [5, 14], and heart transplantation [15]. In our case, transcatheter intrapulmonary lymphatic embolization was planned because the patient had developed drug resistance, and the disease was worsening due to an increase in mucus plug discharge and repetition of pneumonia.
Scrupulous preanesthetic evaluation could possibly have helped to prevent the airway emergency in our patient. As the mucus plug had been discharged on the morning of surgery and a large amount of secretions and mucosal swelling were observed in the upper airway, the timing of operation should have been reconsidered. Moreover, preoperative steroids or thrombolytics might have been effective.
We selected general anesthesia with a cuffed endotracheal tube to achieve immobility intraoperatively and to secure the airway and respiration, as the procedures were planned through the internal jugular vein. A cuffed endotracheal tube was also appropriate as manual ventilation with a maximum airway pressure of 50 mmHg or higher was required during the respiratory tract obstruction caused by the mucus plugs. Although the bronchoscope worked poorly through the endotracheal tube (inner diameter 4.5 mm), we decided not to exchange the endotracheal tube intraoperatively because the risk to the patient was thought to be significant.
The ventilation mode during anesthesia in PB should be chosen carefully, as maintaining spontaneous breathing and cough reflexes may significantly aid in the expectoration of mucus plugs. We speculated that positive pressure ventilation pushed the mucus plugs deep into the peripheral airways and the elimination of cough reflexes made their expulsion difficult. Mucus plugs were expectorated after the recovery of the cough reflex, and the respiratory status was stabilized after the resumption of spontaneous breathing. Although spontaneous breathing is typically recommended to decrease pulmonary vascular resistance in Fontan circulation, there is also a risk of pulmonary vascular resistance elevation through the accumulation of CO2 in cases of insufficient spontaneous respiration.
In PB after Fontan surgery, we speculate that it is preferable to perform surgery in a facility where ECMO is immediately available. Our patient was transferred to a children’s hospital for the sake of safety, as ECMO was not available for young children in our institution. Respiratory tract obstruction recurred, and ECMO was initiated after the transfer. The use of ECMO in more invasive surgical treatments for PB has been reported [13, 14]. Given the high risk of critical airway obstruction, general anesthesia for a patient with PB should be planned with ECMO or CPB standby.