**5. Rehabilitation**

creates disturbances to blood flow, presence of a foreign body, endothelial injury, chronic illness, and non-physiologic shear stress—all of which increase the risk of thromboembolism. For patients on venoarterial ECMO, or in patients with an atrial septal defect or pulmonary arteriovenous malformation, thrombus from the ECMO circuit can travel to the systemic cir-

Cerebral ischemia can also occur without embolus. In patients on venoarterial ECMO with blood return in the femoral artery, it is possible for the great vessels to receive poorly oxygenated blood from the dysfunctional lungs, while the remainder of the body is perfused by well-oxygenated blood from the ECMO circuit. This phenomenon, known as Harlequin syndrome, can lead to chronic cerebral hypoxia [23]. Like other cerebrovascular events, this condition warrants immediate investigation and remedy. There are multiple solutions to this inadequate mixing, ranging from repositioning of the arterial return cannula within the femoral artery, conversion to veno-venoarterial ECMO (which delivers oxygenated blood to the right atrium as well as the arterial circulation), central cannulation of the aorta, or operative

Acute kidney injury (AKI) secondary to ECMO therapy is a relatively common occurrence and is associated with a fourfold increase in mortality when it progresses to chronic kidney disease or end-stage renal failure. The development of AKI is common in critical illness and the underlying disease process necessitating ECMO initiation places the patient at risk for AKI. Additionally, ECMO itself can exacerbate the progression of AKI, due to potential changes to renal perfusion, chronic inflammation resulting in renal injury, changes to endocrine homeostasis, as well as the risk of exposure to nephrotoxic substances during a period of prolonged critical care [24].

Patients on long-term ECMO therapy are at significant risk of infectious complications. The combined presence of critical illness, chronic blood-contacting medical devices, and an ICU stay greatly increase the likelihood of infection. Patients on long-term ECMO who develop a systemic infection have an increased mortality rate, possibility for loss of transplant candidacy, and increased complexity of care. Many patients decompensate to a level requiring ECMO as a result of an infectious process, with pneumonia a common presenting condition. Due to the presence of indwelling cannulae, bloodstream infection is a major concern in caring for the ECMO patient. For the long-term ECMO patient, prolonged exposure to nosocomial pathogens is of particular concern, as these pathogens are likely to exhibit multidrug resistance. Cannula site infections may also occur, which require re-cannulation at a distant site, as well as debridement and drainage of the infected cannulation site. Infection at a cannulation site places patients at risk for vascular complications, such as hemorrhage, hematoma, arteriovenous fistula formation, or development of an aneurysm or pseudoaneurysm. Treatment of the infected ECMO patient can be a particular challenge, and consultation with Infectious Disease specialists is often required. The gas exchange requirements of the ECMO circuit result in the development of a large surface area, which results in a large foreign attachment site for bacteria.

culation and potentially embolize in the cerebral vasculature.

cannulation of the subclavian vessels.

224 Advances in Extra-corporeal Perfusion Therapies

**4.5. Acute kidney injury**

**4.6. Infection**

Like all patients with organ failure, patients requiring ECMO therapy for cardiac or respiratory failure are critically ill and are subject to ICU-related complications, deconditioning, and muscle wasting. In the earliest applications of ECMO, patients were highly sedated and immobilized. With technological developments and advancements in ECMO patient management, the once sedated ECMO patient has now been awakened and extubated. In the population of patients with respiratory failure, the awake ECMO technique showed promising results, with improved survival over sedated ECMO patients and mechanically ventilated patients. Currently, patients on ECMO frequently receive physical therapy, with ambulatory physical therapy the goal for many patients.

Physical therapy in the ECMO patient begins with stationary strengthening and mobility exercises, performed supine while in their ICU bed. These typically consist of core strengthening, limb raises, and stretching. The patient is then progressed to exercises while sitting on their bed, with strengthening of their core and limbs, as well as sitting balance as a goal. When tolerating this, the patient can be transitioned to a chair to be out of bed for a period of each day. With assistance, the patient on ECMO can stand and then ambulate [27].

Patients who cannot ambulate due to either preexisting mobility deficits or incompatible cannulation sites can exercise using a stationary bicycle or an upper body hand bike. In general, access of the femoral vessels limits the ability of patients to ambulate while on ECMO, and for the long-term ECMO patient, transition to other cannulation sites may be necessary. Notably, femoral cannulation is not an absolute contraindication to ambulation, and many centers ambulate patients on ECMO despite venous and arterial access to the femoral vessels.

The approach to ambulatory physical therapy begins with patient preparation, with many centers electing to free the femoral vessels from cannulation as a first step. With adequate ECMO oxygenation, patients may then be extubated if possible; if patients are not candidates for extubation, placement of a tracheostomy can facilitate secretion management, weaning from the ventilator, and weaning of sedation. Following these preparatory procedures, the patient is ready to begin active physical therapy, culminating in ambulation. This is a resource-intensive task, requiring physicians, nurses, perfusionists, respiratory therapists, physical therapists, and assistants. Particular attention must be paid to cannula management, as cannula dislodgement has significant adverse consequences [28].
