Critical Care Medicine-Pulmonary Disorders>>>>>Lung Transplantation, Complications, and VV ECMO
Question 1#

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?

A. Initiation of veno-venous (VV) ECMO
B. Administration of inhaled nitric oxide
C. Therapeutic plasma exchange
D. Systemic anticoagulation

Correct Answer is B

Comment:

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.

References:

  1. Snell GI, Yusen RD, Weill D, et al. Report of the ISHLT Working Group on Primary Lung Graft Dysfunction, part I: definition and grading-A 2016 Consensus Group statement of the International Society for Heart and Lung Transplantation. J Heart Lung Transplant. 2017;36:1097- 1103.
  2. Diamond JM, Arcasoy S, Kennedy CC et al. Report of the International Society for Heart and Lung Transplantation Working Group on Primary Lung Graft Dysfunction, part II: epidemiology, risk factors, and outcomes-A 2016 Consensus Group statement of the International Society for Heart and Lung Transplantation. J Heart Lung Transplant. 2017;36:1104-1113.
  3. Porteous MK, Lee JC. Primary graft dysfunction after lung transplantation. Clin Chest Med. 2017;38:641-654.