You are caring for a recent lung transplant recipient in the intensive care unit who is intubated and on mechanical ventilation. According to a recent review article, which of the following interventions is MOST appropriate for this patient?
(A) Normalize tidal volume to 6 mL/kg of donor predicted body weight ✔
(B) Maintain positive end-expiratory pressure (PEEP) above 15 cm H2O X
(C) Maintain pH below 7.25 X
Read the discussion below.
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As the number of lung transplantations increases, it is critical for clinicians to understand best practices to care for patients undergoing this procedure. A recently published review described common complications after lung transplantation, associated risk factors, and key recommendations for patients in the intensive care unit following transplantation.
After lung transplantation, recipients are at risk for the same complications typical in other postcardiothoracic surgery patients (eg, hemorrhagic complications, tamponade, infection, arrhythmia, delirium) and many transplant-specific complications (Table 1). These include pneumonia (donor-associated or ventilator-associated), acute rejection, mechanical complications (eg, anastomotic dehiscence or pulmonary vein stricture), cardiogenic shock, phrenic nerve injury, and primary graft dysfunction. Primary graft dysfunction is defined as diffuse pulmonary infiltrates and hypoxemia without another identifiable cause that develop within 72 hours after lung transplantation. Primary graft dysfunction is relatively common (20%–30%) and carries a high risk of mortality. In addition to anatomic risk factors in donors (eg, lack of bronchial circulation, temporary lack of lymphatic drainage, lack of innervation), primary graft dysfunction is associated with grafts from donation after brain death, prolonged warm ischemic time, and undersized allografts. Recipient risk factors include underlying diagnosis (sarcoidosis, idiopathic pulmonary fibrosis, and pulmonary hypertension) and body mass index above 25 kg/m2. Intraoperative risk factors for primary graft dysfunction include the use of cardiopulmonary bypass, prolonged ischemic time, and a large volume of allogeneic blood product transfusion (Figure 1).
Table 1. Postoperative acute critical complications associated with lung transplantation. Used with permission, from Di Nardo M, Tikkanen J, Husain S, et al. Postoperative management of lung transplant recipients in the intensive care unit. Anesthesiology. 2022;136(3):482-499. doi:10.1097/ALN.0000000000004054
Figure 1. Donor, recipient, and donor–recipient interaction—associated risk factors for primary graft dysfunction. Used with permission, from Di Nardo M, Tikkanen J, Husain S, et al. Postoperative management of lung transplant recipients in the intensive care unit. Anesthesiology. 2022;136(3):482-499. doi:10.1097/ALN.0000000000004054. Information from Diamond JM, Arcasoy S, Kennedy CC, Eberlein M, 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(10):1104-1113. doi:10.1016/j.healun.2017.07.020
The authors of the review presented several key recommendations related to mechanical ventilation and hemodynamic management for lung transplant recipients. For mechanical ventilation, the general approach is to provide lung protective ventilation for all lung recipients and to pursue early extubation in those with evidence of normal allograft function. Recommendations for mechanical ventilation include a tidal volume of 6 mL/kg donor predicted body weight, positive end-expiratory pressure below 14 cm H2O, and plateau pressure below 30 cm H2O with a goal of SpO2 above 90% and pH above 7.25. With these settings, if the resultant PaO2/FIO2 ratio exceeds 200 and the pH is above 7.25, early extubation should be pursued.
For those recipients with evidence of or at high risk for primary graft dysfunction, a more conservative and nuanced approach is recommended. If the PaO2/FIO2 ratio is below 200, sedation should be continued, with tidal volume limited to 6 mL/kg donor predicted body weight and plateau pressure maintained below 25 cm H2O. If the PaO2/FIO2 ratio is below 150, neuromuscular blockade and inhaled nitric oxide should be considered. Finally, if the PaO2/FIO2 ratio is below 100, extracorporeal membrane oxygenation (ECMO) should be considered. Single lung transplant recipients may require small tidal volumes (4–6 mL/kg) in the setting of underlying fibrotic lung disease. Longer expiratory times may be appropriate for those with underlying obstructive lung disease.
From a hemodynamic perspective, the authors made the following recommendations for lung transplant recipients. The overall initial goals after lung transplantation are to minimize pulmonary wedge (or left atrial) pressure (≤10 mm Hg) and central venous pressure (≤7 mm Hg) while maintaining an adequate, but not excessive, cardiac index (2.2–2.5 L/min/m2). An elevated left atrial pressure can increase the risk of cardiogenic pulmonary edema, while an elevated cardiac output (cardiac index > 2.5 L/min/m2) will increase the risk of reperfusion injury and primary graft dysfunction. Cardiac output and lung perfusion should be allowed to gradually increase while closely monitoring for signs of hyperperfusion and primary graft dysfunction. Patients with a history of pulmonary hypertension are at particularly high risk of developing primary graft dysfunction because of their preexisting cardiac changes. These patients may exhibit left-sided diastolic dysfunction. Furthermore, a right ventricle that has hypertrophied in the setting of pulmonary hypertension may produce excessive cardiac output once a normal pulmonary vascular resistance is encountered after lung transplantation.
With an increasing lung transplant population and an expanding number of transplant centers, it is important for clinicians to understand the primary respiratory and cardiovascular management considerations for lung transplant recipients. This review provides anesthesiologists and other perioperative clinicians with a high-yield explanation of critical postoperative management principles for this patient population.
- Di Nardo M, Tikkanen J, Husain S, et al. Postoperative management of lung transplant recipients in the intensive care unit. Anesthesiology. 2022;136(3):482-499. doi:10.1097/ALN.0000000000004054
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