Emergency Medical Services. Группа авторов

Figure 11.3 Emergency assessment of a patient with an LVAD.

Patients with continuous‐flow devices may not have reliable pulse oximetry readings due to low pulse pressures. As noted, a continuous‐flow device will not produce a palpable pulse or a measureable blood pressure. The EMS clinician will need to use other signs to assess perfusion, such as skin color, absence or presence of diaphoresis, and mental status changes. The patient should be placed on a cardiac monitor, and a 12‐lead ECG should be performed if possible, though the LVAD will create electrical noise on the ECG tracing. LVAD patients should also be exposed to examine for cable disconnections. The driveline skin site should not be routinely examined unless absolutely necessary, due to risk of infection. Clothes should not be cut with shears as there is risk of cutting the cables with disastrous results. For the same reasons, the patient should be moved carefully to prevent dislodgment. Patients showing signs and symptoms of another illness, such as stroke, should be assessed in the usual fashion, regardless of the assist device.

      Patients with evidence of hemodynamic compromise or hypoperfusion should have large‐bore IV access, and be volume resuscitated. Vasopressors are not generally a good initial therapy, as many problems are volume‐related, and vasopressors will increase afterload, which can worsen pump flow [11].

      Arrhythmias should only be treated if they are symptomatic. An LVAD patient with full left ventricle support may be able to tolerate ventricular tachycardia or fibrillation. If the arrhythmia requires treatment, the usual therapies can be used for rate control and rhythm conversion. The patient can also receive electrical therapy [11]. Defibrillator pads should not be placed over the device. Some devices may require that the system controller cables be disconnected prior to defibrillation to prevent damage to the electronics. The patient should also be examined for the presence of an implantable cardioverter defibrillator (ICD), which should provide the appropriate treatment in the event of ventricular arrhythmia [22].

      The decision of when to perform CPR can be a major conundrum in treating these patients. Knowledge of the device type and function is crucial. Patients with first‐generation LVADs producing pulsatile flow should not receive chest compressions. Instead the hand pump should be used. Second‐generation and later continuous‐flow devices will not have a hand pump. Chest compressions carry the risk that they may dislodge the device, resulting in exsanguination and death. On the other hand, if the LVAD is not pumping, the underlying left ventricle will not have the ability to maintain perfusion of organ systems. Patient survival is not likely. Lack of compressions may also result in a thrombus formation in the pump, resulting in obstruction to pump flow, and potential downstream embolic events. Awareness by EMS clinicians of the patient’s advanced directives regarding resuscitation may be important, as these patients have chronic severe disease. Ideally, device information, patient wishes and treatment plans, and contact information should be prepared prior to initial discharge from the hospital. In the event of an EMS contact with a patient who is hypoperfused and has a nonfunctioning pump, an attempt may be made to contact the LVAD coordinator for further recommendations. If the coordinator cannot be reached, and the patient is to be resuscitated, compressions should be started and transport initiated per local protocols [11].

      The LVAD patient should be transported to the hospital that placed the device if possible. These hospitals are usually tertiary care centers and should be capable of managing not only LVAD complications but also other issues, such as stroke or GI bleeding. If there are distance issues, air medical transport should be considered. This can shorten transit time and also provide critical care services. Regardless of transport mode, the LVAD patient should be transported with all device equipment, batteries, controllers, documentation, and caregivers (if possible).

Electrical cardiac support devices

      EMS personnel may also encounter patients in the field with short‐term electrical support devices, such as wearable cardioverter defibrillators (WCDs), or long‐term, implanted cardiac devices, such as implantable cardioverter defibrillators (ICDs) and pacemakers. The approach to a patient with an electrical cardiac support device who is suffering from a medical condition is to determine if the problem results from the device or the underlying medical condition. While these devices are generally safe and effective, thousands of patients have been affected by pacemaker and ICD malfunctions [23].

      Pacemakers

      Cardiac pacemakers are implanted in patients who suffer from bradycardic dysrhythmias. If the patient’s intrinsic rhythm falls below a set target, the pacemaker will provide an electrical stimulus to the myocardium.

Pacemakers are designated with a five‐letter code; the first three letters are referred to most often. The first letter indicates the chamber paced, the second letter indicates the chamber sensed, and the third letter the response after sensing (Box 11.3) [24, 25]. Pacemakers can be single chamber or dual chamber. The more common single‐chamber pacemaker is VVI, which paces the ventricle, senses the ventricle, and inhibits the output pulse if intrinsic ventricular activity is detected. The more common dual‐chamber pacemaker is DDD, which paces and senses in both the atrium and ventricle and has dual response to sensed intrinsic activity [25].

Box 11.3 Pacemaker codes

      Sources: Mulpuru SK, Madhavan M, McLeod CJ, Cha YM, Friedman PA. Cardiac pacemakers: function, troubleshooting, and management: part 1 of a 2‐part series. J Am Coll Cardiol. 2017; 69:189–210; Kenny T. The Nuts and Bolts of Implantable Device Therapy Pacemakers. Hoboken, NJ: Wiley & Sons, Ltd. 2015. Chapter 13, Pacemaker modes and codes; pp 140–52.

The EMS physician who responds to a pacemaker patient with a clinical issue should determine if the device is the problem. Vital signs and cardiac monitoring are the best tools. The first determinant is the heart rate. If the patient is markedly bradycardic,