should start with a division between “stable/no symptoms” and “symptomatic and unstable or borderline.” Those in the “stable/no symptoms” category should be observed, expeditiously transported, and monitored, with precautionary IV insertion and, if needed, oxygen. As a corollary, unstable patients with bradycardia or tachycardia should receive prompt electrical therapy (pacing or countershock), airway support, monitoring, and IV insertion occurring either in tandem with or after electrical therapy. EMS clinicians should save rhythm strips and give sedation if possible, but not withhold lifesaving treatment trying to “get a good strip” or titrating sedation. Unless the signs of instability are subtle, medical oversight contact should follow the initial treatment of unstable patients.
Summary
Evaluate prehospital dysrhythmias in patients in a way tailored to the time restraints, physical limitations, and outcome needs that are specific to the field setting. Decision trees should be simple and effective, focusing on treating patients and not rhythms per se. Protocols must identify and treat all unstable patients. Those without symptoms or with trivial symptoms do not require rhythm‐directed therapies. For symptomatic but stable patients, a few key steps should be taken to help manage each case.
References
1 1 Neumar RW, Shuster M, Callaway CW, et al. Executive summary: 2015 American Heart Association guidelines update for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2015; 132: S315–67.
2 2 Yealy DM, Kosowsky J. Dysrhythmias. In Walls R, Hockberger R, Gausche‐Hill M editors. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 9th ed. Philadelphia, PA: Elsevier/Saunders, 2018.
3 3 McCabe J, Menegazzi JJ, Adhar G, Paris PM. Intravenous adenosine in the prehospital treatment of supraventricular tachycardia. Ann Emerg Med. 1992; 21:358–61.
4 4 American Heart Association. Part 6: Electrical therapies: automated external defibrillators, defibrillation, cardioversion, and pacing. Circulation. 2010; 112:S706–19.
5 5 Scholten M, Szili‐Torok T, Klootwijk P, Jordaens L. Comparison of monophasic and biphasic shocks for transthoracic cardioversion of atrial fibrillation. Heart. 2003; 89:1032–4.
6 6 Tanabe S, Yasunaga H, Ogawa T, et al. Comparison of outcomes after use of biphasic or monophasic defibrillators among out‐of‐hospital cardiac arrest patients. Circ Cardiovasc Qual Outcomes. 2012; 5:689–96.
7 7 Hedges JR, Syverud SA, Dalsey WC, et al. Prehospital trial of emergency transcutaneous pacing. Circulation. 1987; 76:1337–40.
8 8 Paris PM, Stewart RD, Kaplan RM, Whipkey R. Transcutaneous pacing for bradyasystolic cardiac arrest in prehospital care. Ann Emerg Med. 1985; 14:320–3.
9 9 Dorian P, Case D, Schwartz B, et al. Amiodarone as compared with lidocaine for shock‐resistant ventricular fibrillation. N Engl J Med. 2002; 346:884–90.
10 10 Wrenn K. Management strategies in wide QRS complex tachycardia. Am J Emerg Med. 1991; 9: 592–7.
11 11 Wilber DJ, Baerman J, Olshansky B, et al. Adenosine sensitive ventricular tachycardia: clinical characteristics and response to catheter ablation. Circulation. 1993; 87:126–34.
12 12 O’Toole KS, Heller MB, Menegazzi JJ, Paris PM. Intravenous verapamil in the treatment of paroxysmal supraventricular tachycardia. Ann Emerg Med. 1990; 19:279–85.
13 13 Wang HE, O’Connor RE, Megargel RE, et al. The use of diltiazem for treating rapid atrial fibrillation in the out‐of‐hospital setting. Ann Emerg Med. 2001; 37:38–45.
14 14 McLean SA, Paul ID, Spector PS. Lidocaine‐induced conduction disturbance in patients with systemic hyperkalemia. Ann Emerg Med. 2000; 36: 626–7.
CHAPTER 11 Cardiac procedures and managing technology
Joanna L. Adams and David P. Thomson
Introduction
Cardiovascular collapse can occur from either mechanical pump failure or electrical failure. As technology continues to produce devices and procedures to support these patients, the EMS clinician is likely to encounter patients reliant on this technology. Many of these patients are managed by critical care teams during interfacility transports. There are also many patients who are dependent on these cardiac devices living outside the hospital who are encountered by prehospital EMS practitioners. Familiarity with these devices and how to troubleshoot them is paramount to appropriate care of these technology‐dependent patients by the EMS system. There are also procedures that the EMS physician should be knowledgeable about that can be used to stabilize patients suffering from cardiovascular collapse in the prehospital setting.
Short‐term mechanical circulatory support devices
Categories of short‐term mechanical circulatory support devices used to manage acute cardiogenic shock include intra‐aortic balloon pumps (IABPs), non‐IABP percutaneous mechanical circulatory support devices, extracorporeal membrane oxygenator (ECMO) pumps, and nonpercutaneous centrifugal pumps (cardiopulmonary bypass). Each improves end‐organ perfusion, reduces intracardiac filling pressures, reduces left ventricular volumes and myocardial oxygen consumption, and augments coronary perfusion. Each type of device results in specific complexities and challenges during interfacility transport. Often, the required expertise necessitates that an experienced team be involved. Teams may be composed of critical care paramedics, nurses, and physicians who are specially trained to address complications with these devices and able to support the patient in the event of device failure. For example, in the case of ECMO, it is important that a perfusionist or other specialist is part of the team and dedicated to managing the pump [1].
Intra‐aortic balloon pump
The IABP is used to help stabilize acutely ill cardiac patients. Its role is to provide support until short‐term recovery or definitive care. The IABP works by decreasing cardiac afterload, augmenting diastolic perfusion pressure, and increasing coronary artery perfusion [2]. The decrease in afterload reduces the workload on the heart, and the improved coronary artery circulation can increase oxygen supply to the myocardium. EMS clinicians will encounter IABP patients during interfacility transfers, often for more advanced cardiac care or surgery.
The most common indications for an IABP are acute myocardial infarction, cardiogenic shock, ventricular aneurysm, left ventricular failure, valve or papillary muscle rupture, or a combination of these factors [3]. Absolute contraindications for an IABP include aortic dissection, abdominal aortic aneurysm, and aortic valve incompetence. Relative contraindications include bleeding disorders and atherosclerosis [2].
The IABP catheter is inserted via the femoral artery and then advanced into the thoracic aorta. The tip of the balloon should be positioned 1‐2 cm distal to the origin of the subclavian artery and must be above the branches of the renal arteries. If the balloon is not placed correctly, occlusion of coronary, subclavian, or renal arteries could occur [2]. On a chest x‐ray, the tip of the catheter should be visible between the second and third intercostal space. When inflated, the balloon should not completely occlude the aortic lumen, as this can damage the aortic wall, and blood components [2]. Most devices have different‐sized balloons to be used based on patient weight or height. It is important to ensure the appropriate balloon volume is being used.
IABP function is dependent on precise timing. The balloon is cycled in conjunction with the cardiac cycle. It is important to remember the balloon is inflated during diastole, and deflated just prior to systole. While the balloon is inflated, blood is pushed both back toward the heart, as well as distal in the aorta. The result is increased blood flow to coronary and carotid arteries and increased systemic perfusion. The balloon is deflated very rapidly, and this rapid loss of volume reduces the pressure in the aorta. The result is that the left