A 45-year-old female with history of idiopathic pulmonary fibrosis is admitted to the intensive care unit (ICU) after compatible bilateral lung transplantation. The surgery required the use of intraoperative cardiopulmonary bypass (CPB). Postoperatively, she is on lung protective ventilation with low tidal volumes. She has progressive increase in oxygen requirements and is requiring an FiO2 of 0.7 with a PEEP of 10 to maintain saturations of 92%. At 24 hours, her PaO2 /FiO2 ratio is 175 and chest radiography reveals bilateral diffuse infiltrates. She has a HR of 90/min, BP of 105/76 mm Hg, and a CVP of 7 mm Hg. A bronchoscopy is performed which is unremarkable except for mild erythema in the bronchi.
Which of the following is the MOST appropriate next step in managing this patient?
Correct Answer: B
The most probable diagnosis in this patient with worsening hypoxemia after lung transplantation is primary graft dysfunction (PGD), which is most likely to improve with inhaled nitric oxide. PGD is a common complication occurring in the first 72 hours and is a leading cause for early morbidity and mortality. It is considered a form of ischemia-reperfusion injury and is characterized by hypoxemia associated with diffuse alveolar infiltrates on chest radiography. Donor risk factors for PGD include aspiration, chest trauma or lung contusion, undersized donor, and heavy alcohol use. Significant recipient risk factors for PGD are female sex, African American race, obesity, prior pleurodesis and a pretransplant diagnosis of idiopathic pulmonary fibrosis, sarcoidosis, or idiopathic pulmonary arterial hypertension. Operative risk factors include the use of CPB, prolonged ischemia time, high reperfusion FiO2 , and large volume blood transfusion.
Given the similarities between PGD and ARDS, management strategies for ARDS have been extrapolated to PGD. The mainstay of management involves lung protective ventilation with fluid restriction. In patients with severe PGD, inhaled nitric oxide and inhaled prostacyclins have been tried to improve oxygenation. Nitric oxide (NO) availability is reduced in ischemia-reperfusion injury, and animal studies have shown improved allograft function with NO treatment (B). Posttransplant ECMO (A) is generally reserved for patients with severe hypoxemia (PaO2 /FiO2 <100) who fail to improve with the above strategies. Patients who require ECMO for PGD have higher complication rates and poor outcomes when compared to those who improve with other supportive management. Hyperacute rejection is another rare complication and has to be ruled out by reviewing the results of pretransplant panel reactive antibody testing and the donor-recipient cross match. In the presence of donor-specific HLA antibodies, treatment of rejection includes therapeutic plasma exchange (C) and other immunosuppressive therapies. Systemic anticoagulation (D) is used in the treatment of pulmonary embolism and thrombosis of venous anastomosis.
Which of the following patients on mechanical lung support in ICU is best suited for lung transplantation?
Correct Answer: A
Lung transplantation is considered for patients with end-stage lung disease who carry an expected 2-year mortality rate of greater than 50%. Expected likelihood of survival at 90 days and 5 years posttransplantation are also taken into consideration when selecting candidates for transplantation. Mechanical ventilation and/or extracorporeal life support (ECLS) are considered as “relative” contraindications for lung transplantation. At the same time, it is important to review and rule out other absolute and relative contraindications in a patient on mechanical support. There is a growing interest in using ECMO in awake, nonintubated patients as a bridging modality. “Awake” ECMO (A) offers the advantage of participation in physical therapy and rehabilitation before transplant. Successful transplantation with better outcomes has been reported with this strategy when compared to traditional mechanical support.
A 58-year-old male patient is admitted to the hospital 6 months after receiving bilateral lung transplantation. He complains of increasing shortness of breath with a “barking” cough and inability to clear secretions over the past 2 months. He mentions that he has been sleeping in his recliner chair due to dyspnea when lying flat. He is afebrile with a HR of 88/min, BP of 140/80 mm Hg, SpO2 of 94% on room air, and a respiratory rate of 30/min. He is using his accessory neck muscles, and right-sided rhonchi are noted during the chest examination. Administration of bronchodilators fails to improve his symptoms. He is started on noninvasive positive pressure ventilation, which leads to a marked improvement.
Which of the following is the gold standard test to diagnose his condition?
Correct Answer: C
The patient described here has most likely developed tracheobronchomalacia with or without bronchial stenosis, which will require visualizing with a fiber-optic bronchoscope (C). Malacia is defined as greater than 50% reduction in the airway lumen during expiration. It can be localized to the anastomotic site or diffusely affect the donor airways. Clinical features include dyspnea that may be aggravated in the recumbent position, chronic “barking” cough, wheezing, inability to clear secretions, and recurrent infections. Spirometry (A) may show a reduction in FEV1 and forced expiratory flow at 25% to 75% but is not confirmatory. Variable obstructive pattern may be seen in flow-volume loops. A dynamic CT scan of the chest may show the respiratory change in airway lumen, but a standard CT scan will not be diagnostic (B). Bronchoscopy is the gold standard tool for diagnosing airway complications including tracheobronchomalacia. It allows for direct visualization of the dynamic luminal narrowing during expiration. It can be present alone or at a site of bronchial stenosis. A sputum culture (D) would help to diagnosis if this patient had pneumonia, but the chance of a pneumonia with the patient being afebrile and producing clear secretions is fairly low.
Management of tracheobronchomalacia can be challenging. Observation is recommended for asymptomatic disease. Medical management is initially considered for symptomatic disease and involves chest physiotherapy, mucolytics, and noninvasive positive pressure ventilation. More invasive options such as stenting and trachea-bronchoplasty may be considered for severe malacia that is localized to the central airways.
Three months after bilateral lung transplantation, a 50-year-old female patient is admitted to the ICU with complaints of worsening shortness of breath, low grade fever, and cough. She is compliant with her drug regimen consisting of prednisone, tacrolimus, azathioprine, valganciclovir, and trimethoprim-sulfamethoxazole. Examination reveals bilateral crackles and decreased breath sounds over the left lower chest wall. She has:
She is started on oxygen therapy, and a chest CT is obtained, which reveals bilateral ground glass opacities with a leftsided pleural effusion. Laboratory testing is unremarkable except for slight eosinophilia. Bronchioalveolar lavage reveals lymphocytic predominance and transbronchial biopsy is significant for dense perivascular and bronchial mononuclear infiltrates with a negative C4d staining.
Which of the following is the best next step in management?
Patient seems to be undergoing acute cellular rejection and will need to be treated with intravenous corticosteroids such as methylprednisone (A). Spirometry typically shows a decrease in FEV1 in acute rejection. CT scan findings in acute rejection include ground-glass opacities, interlobular septal thickening, pleural effusions, and lung volume loss. The gold standard test to diagnose rejection is flexible bronchoscopy with bronchoscopic alveolar lavage and transbronchial biopsy. Two main histopathological components used for grading are the severities of lymphocytic bronchiolitis and perivascular mononuclear cell infiltrates. Intravenous high-dose corticosteroids are the mainstay of treatment for symptomatic or high-grade acute cellular rejection. Other treatment options that have been used for acute cellular rejection include antithymocyte globulin, extracorporeal photopheresis, and alternative immunosuppressive agents such as alemtuzumab and sirolimus or everolimus. Acute rejection episodes are important risk factors for the development of chronic lung allograft dysfunction. Therefore, prevention and treatment of acute rejection by appropriate immunosuppressive regimen is essential. CMV pneumonitis is unlikely in a patient who is already on valganciclovir prophylaxis. Therefore, intravenous ganciclovir in this patient is not warranted (B).
The main differential diagnoses of acute cellular rejection include humoral rejection and infections. Humoral rejection can be hyperacute rejection or acute antibody-mediated rejection. Hyperacute rejection presents in the first 24 hours following transplantation and is due to preformed donor-specific antibodies (DSA). Acute antibody-mediated rejection presents later and is due to DSA that developed or increased in titers after transplantation. The diagnoses require demonstration of DSA along with ruling out other conditions. The histopathological hallmark of acute antibody-mediated rejection is subendothelial deposition of C4d demonstrated by immunohistochemistry but is not essential for diagnosis. Specific treatment options for humoral rejection include intravenous immunoglobulins (IvIg), therapeutic plasma exchange (D), rituximab (C), and bortezomib.
A 62-year-old male patient with end-stage emphysema undergoes left-sided single-lung transplantation. He arrives at the ICU after his surgery and is mechanically ventilated on volume assist control mode. The initial ventilator settings are FiO2 of 0.4, PEEP of 10 cm H2O, tidal volume of 380 mL, and respiratory rate of 20 breaths/minute. A few hours later, arterial blood gas reveals hypoxia with hypercapnia. In response, his ventilator settings are changed to FiO2 of 0.5, PEEP of 12 cm H2O, and respiratory rate of 26 breaths/min. One hour later, he has a HR of 120/min, BP of 80/60 mm Hg and SpO2 of 89%. Chest examination reveals bilateral air entry with coarse breath sounds on the left. Arterial blood gas shows worsening hypoxia and hypercapnia. He is started on norepinephrine, and FiO2 is further increased to 0.6.
What is the next best step in management of this patient?
The clinical picture in this patient is suggestive of clinically significant acute native lung hyperinflation. Recipients of single lung transplantation for emphysema are prone to develop native lung hyperinflation. The native lung is highly compliant when compared to the graft lung in patients with COPD. It has severe expiratory airflow limitation that can lead to dynamic hyperinflation and air trapping and hence will improve by decreasing the respiratory rate and PEEP (C). The patient has breath sounds bilaterally and hence does not need a chest tube (A). Increasing PEEP and respiratory rate (B) in this situation can worsen dynamic hyperinflation. Obtaining a CT scan will not help in the acute hemodynamic instability that this patient is in because it does not offer any additional information about his mechanical ventilation (D).
Acute hyperinflation with mediastinal shift to the opposite site can compromise hemodynamic and respiratory functions. The increase in intrathoracic pressure impairs venous return and causes hypotension, often requiring vasopressors. Marked compression of the graft lung results in atelectasis, hypoxia, and hypercapnia.
Positive pressure ventilation in such cases must be tailored to the characteristics of the native lung. The best approach to mechanical ventilation in these patients is to maximize the expiratory time by having a shorter inspiratory time and a lower respiratory rate with minimal PEEP. Acute symptomatic hyperinflation has also been treated by temporarily disconnecting the endotracheal tube from ventilator to allow deflation of the native lung. Ventilation can be very challenging if the graft lung develops edema or PGD. Severe respiratory or hemodynamic compromise in such patients can be treated with differential lung ventilation by placing a double-lumen tube. This allows for independent ventilation of the native and graft lungs with suitable ventilator settings.
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