Advanced radiological imaging in patients treated with Extracorporeal Memebrane Oxygenation

Abstract

Extracorporeal membrane oxygenation (ECMO) is the use of a modified heart-lung machine to support life during severe acute cardiac and/or respiratory failure. Patients on ECMO are at high risk for complications due to the severe underlying disease and to the ECMO procedure itself. The clinical evaluation of patients on ECMO may be unreliable and the diagnostic value of portable bedside imaging is limited. Advanced radiographic methods like CT are rarely used during ongoing ECMO and MRI has previously never been tested. There is also lack of knowledge of the long term respiratory function in survivors of severe acute respiratory distress syndrome (ARDS) and ECMO.

The frequency, indications, findings and effect on treatment of CT performed in patients during ECMO therapy, at the ECMO department Karolinska University Hospital, were retrospectively reviewed.

Paper I: It was found that CT had been performed in nearly half of the treated patients, most often due to suspected complications. In 57% of 104 CT occasions clinically significant findings were revealed. There were no complications to the CT examinations.

Paper II: In 25% of 118 performed thoraco-abdominal CT scans clinically important complications, dominated by hemothorax, massive pleural fluid, pericardial tamponade and abdominal hemorrhages, were revealed. The majority resulted in surgery or percutaneous drainage during ECMO, with high survival rates. Accordingly, the role of chest and abdominal CT during ECMO is to identify patients with complications where urgent invasive therapy is essential, when bedside imaging has been inconclusive.

Paper III: In 37% of 123 pediatric and adult patients on ECMO, intracranial hemorrhage or infarction was revealed with CT during the treatment. Large hemorrhages or pronounced general edema were reasons to discontinue the ECMO treatment, neurosurgical intervention was motivated in a few patients and in patients with lesions with expected fair prognosis, ECMO was continued with high survival. Thus, the main value of cranial CT is in differentiating patients who have no CNS complications or complications with good prognosis from those with poor prognosis where the treatment should be withdrawn.

Paper IV: Twenty-one adult long term survivors of severe ARDS and ECMO were studied in a follow-up program including CT of the lungs, pulmonary function tests and a dedicated questionnaire for evaluation of respiratory problems. It was found that lung parenchymal changes suggestive of fibrosis, pulmonary function abnormalities and subjective respiratory symptoms can be found more then one year after ECMO-treated severe ARDS. However, the impairments are most often mild and the majority has good physical and social functioning.

Paper V: In an experimental study, the ECMO system was tested for magnetic resonance imaging (MRI) compatibility, using a pig model. The study showed that MRI can safely be performed in living subjects. on ECMO with high quality images. In the future this may have an impact, especially on early diagnosis and treatment of cerebral complications in patients on ECMO.