Extracorporeal membrane oxygenation (ECMO) is progressively used in critically ill patients with cardiac or respiratory failure as a bridging option for potential organ recovery. However, ECMO survivors often suffer from poor neurocognitive outcome due to neurological complications such as microembolic (ME) strokes.

In venoarterial (va) ECMO circuits the pulmonary circulation, which usually serves as microembolic filter, may be bypassed and generated ME are prone to reach the brain in substantial amounts and potentially impair cerebral integrity. Although patient exposure to cerebral ME has been thoroughly investigated in cardiopulmonary bypass procedures, there is only limited research on cerebral ME in patients undergoing ECMO therapy.

The primary study goal of this study is to determine the load and nature of cerebral ME in critically ill patients under va-ECMO support. We also aim to compare the results to measurements in healthy subjects und intensive care unit (ICU) patients without extracorporeal support to get a better impression on the relevance of ME generation during ECMO support.

The addition of ICU patients was made according to reviewer suggestions after an initial submission to a medical journal.

Inclusion Criteria (for patients):

• Intensive care patients with cardiac or respiratory failure under va-ECMO therapy
• Age > 18 yrs.
• Signed informed consent

Exclusion Criteria:

• use of any other extracorporeal device including venovenous (vv) ECMO
• continuous renal replacement therapy
• medical history of severe mitral or aortic stenosis
• medical history of severe mitral or aortic regurgitation
• medical history of carotid stenosis > 70 %
• septicaemia
• medical history of vascular dementia or Alzheimer's disease
• inclusion in an other clinical study
• gravidity
• allergy against materials of one of the medical device used in the study

The study population consists of three patient groups with all receiving transcranial Doppler exam: 1. patients undergoing ECMO therapy in the ICU; 2. healthy volunteers, and 3. critically ill controls (patients on the ICU without ECMO)