the process by pressing two buttons simultaneously if they are alert. If not deactivated, gel is ejected between the electrodes and patient’s skin and a shock between 75 and 150 joules is delivered. The vest contains a lithium‐ion battery pack that provides continuous power for 24 hours [29].
Some of the issues related to the success rate of WCDs in preventing SCD is patient compliance. The device should be worn at all times. It should only be removed when bathing and then only if someone is present to initiate lifesaving measures as appropriate. The device has been redesigned to make it more comfortable and lightweight. The sense of security that the WCD provides also contributes to patient compliance [29].
The trials to date have reported a 75% success rate of WCDs providing appropriate shock therapy. Like ICDs, however, the WCDs also produce inappropriate shocks when ventricular arrhythmia is not present. Although WCDs have built‐in patient response buttons to prevent inappropriate shocks, shocks are still delivered because patients forget how to deactivate the device. Patients also do not receive appropriate shocks due to incorrect positioning of the device or its electrodes [29].
When an EMS clinician encounters a WCD patient, a standard evaluation should be conducted. CPR can be performed with the device in place. However, if it is broadcasting an imminent shock, stop CPR. The device should be allowed to complete the defibrillation of the unconscious patient prior to proceeding. If external defibrillation is available, external pads can be placed after disconnecting the monitor from the electrode belt, or the vest can be removed altogether. Prior to removing the vest, the battery should be removed to prevent an inadvertent shock.
Pericardiocentesis
Pericardiocentesis may be indicated during resuscitation for pulseless electrical activity (PEA). If the PEA is the result of cardiac tamponade, pericardiocentesis may reverse that condition. Cardiac tamponade may be difficult to diagnose in the out‐of‐hospital setting. Tamponade may be suspected based on the patient’s clinical presentation. Prior to cardiac arrest, the patient may develop Beck’s triad of jugular venous distension, hypotension, and muffled heart sounds. If available, portable ultrasound can be used to detect tamponade.
Successful pericardiocentesis has been performed in the out‐of‐hospital setting by both EMS physicians and critical care transport teams [30, 31]. It should be used as a final resort when all other therapies have failed [32]. For procedure details, see Chapter 40. Aspiration of blood that does not clot suggests removal from the pericardial space, as opposed to intraventricular blood. Successful pericardiocentesis and the correction of the tamponade physiology should lead to restoration of spontaneous circulation.
Conclusion
Technological advances in both electrical and mechanical cardiac support devices mean that more people are living with them, including people in their homes. Thus, familiarity by EMS clinicians is important to effect optional care and safe transport.
Critical patients who are being supported by IABPs, ECMO, or nonportable VADs require special attention by expert teams when they must be transferred from one facility to another. Among the team members must be a specialist in managing the support device. Planning is key to moving patients safely and effectively.
EMS clinicians are likely to encounter patients with portable VADs, even if infrequently. Ideally, they would know of such patients in their communities before they are summoned for an emergency condition. In any case, they should be able to rapidly identify the presence of a VAD and the need for determination of whether or not pulsatile flow is expected. Patients with VAD‐related problems often require fluid resuscitation, unless the issue is a rare pump failure or power failure. In those cases, the dedicated hand pump should be used to restore blood flow or CPR initiated if the VAD has no hand pump. For problems not immediately indicating a VAD malfunction, such as stroke or GI bleeding, the patient should be treated as he or she would be in the absence of the VAD. It is prudent to attempt to get the patient to the hospital where the VAD was placed if feasible and appropriate.
EMS clinicians should be aware when their patient has a pacemaker or ICD. If the patient’s problem relates to a cardiac dysrhythmia, it is important to assess the ICD or pacemaker function. With a magnet, function can be suspended if it is emitting inappropriate, excessive electrical impulses or shocks.
EMS physicians should be capable of performing pericardiocentesis. Although ultrasound may be a helpful adjunct, the procedure can done using anatomical landmarks.
Acknowledgment
We acknowledge T.J. Doyle, MD, MPH, author of this chapter in the prior edition.
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