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 HeartAssist 5 (ReliantHeart Inc.)

Axial pumps use a corkscrew and the Archimedes principle against gravity. The inflow and outflow pumps are in line with the impeller, resulting in a smaller size pump. In contrast, centrifugal pumps have the inflow and outflow cannulas at right angles to the flow. Right angles allow for less suction, which can decrease the risk of the ventricle collapsing around the inflow cannula or distortion of the interventricular septum. Both can result in right ventricular failure [11]. These continuous‐flow devices are found in 90% of patients with LVADs. Continuous‐flow devices have been shown to produce superior organ perfusion than first‐generation, pulsatile, devices [13].

Third‐generation LVADs represent a further technological step forward. They can use continuous flow, axial flow, or centrifugal pumps. The impeller is driven by electromagnets. This results in no contact between the impeller and the sides of the pump. Benefits include less trauma to blood components and less thrombus formation. The devices are also quieter and can last longer [11]. Fourth‐generation LVADs, currently in testing and trials, are exploring further advances in technology, including wireless monitoring and elimination of the driveline. This would remove the cabling from the pump, which must travel through the skin in order to connect to the power source. As driveline infections are a major source of LVAD complications, driveline removal could result in significantly less morbidity [11].

Figure 11.2 HeartMate II LVAD. LVAS, left ventricular assist system.

Source: Reproduced with permission of the Thoratec Corporation.

The results of these advancements in technology are devices that allow the patient to leave the hospital and function at home. Prior to discharge the patient and family are given extensive training on the operation and maintenance of the device and how to troubleshoot problems and alarms. The patient is followed by a hospital team and is given written instructions for EMS practitioners, which outline the device operation, emergency interventions, and hospital contact information [14].

LVAD complications can be divided into two categories: device problems and patient problems (Box 11.2). The most common problems consist of neurologic events, bleeding, and cardiac arrhythmias. Neurologic events include acute strokes and transient ischemic attacks. Thrombotic and hemorrhagic events can occur. The incidence of stroke in VAD patients has been reported ranging from 8% to 25%. The risk is increased for patients with stroke histories and those who have had device‐related infections [11].

The most commonly experienced forms of bleeding include epistaxis, gastrointestinal bleeding, and hematoma formation. Bleeding can result from trauma to blood components, from acquired von Willebrand disease, or from iatrogenic anticoagulation [15]. Most patients are given anticoagulants or antiplatelet drugs to reduce the risk of thrombus formation [16]. LVAD patients are also at increased risk of arrhythmias. Patients may have atrial fibrillation, often as a result of underlying disease. The LVAD will provide left ventricle support, but the loss of atrial “kick” may affect right ventricular function. LVAD patients may also suffer from ventricular arrhythmias. These arrhythmias may result from underlying disease, from irritation of the myocardium by the device, or from ventricular collapse or septal deviation from excessive pump function. Some patients may require an implanted cardioverter defibrillator [11, 16].

Infection is the most common complication, with infection rates ranging from 18% to 59% among LVAD patients. Infection is second only to heart failure as a cause of mortality in these patients. Infections can present at the surgical site, the driveline, the pump pocket, or the pump itself in the form of endocarditis [17].