Intravenous adenosine as first-line prehospital management of narrow-complex tachycardias by EMS personnel without direct physician control

This study was conducted to evaluate the safety and efficacy of intravenous adenosine therapy for prehospital treatment of narrow-complex tachycardias with a presumptive field diagnosis of paroxysmal supraventricular tachycardia (PSVT) by paramedics without direct physician control. A ten-month prospective case series was designed in an urban EMS system that has paramedics operating under standing orders before physician radio contact. All patients with PSVT field diagnosis were included. Diagnosis of PSVT was made by regular, narrow-complex tachycardia with a heart rate greater than 160 beats/min by field ECG. Interpretation was performed solely by paramedics; ECG transmission was not available. In hemodynamically stable patients, vagal maneuvers were followed by intravenous placement and administration of adenosine as recommended by the manufacturer. If three adenosine boluses failed to convert the arrhythmia, patients were monitored and transported, with electrical cardioversion available. Data collection included demographics, history, medications, vital signs, and ECG tracings. Of 41 included patients, 31 were correctly diagnosed with PSVT (75.6%), with mean ventricular rate of 205 beats/min (SD 7 beats/min); one had sinus tachycardia; nine had atrial fibrillation (AF) (22%). Of the 31 cases correctly diagnosed as PSVT, 28 converted to sinus rhythm after adenosine (90.3%). Of those converted, 16 required a single dose (57.1%), nine required one additional dose (32.1%), and three required two additional doses (10.8%). None reverted to PSVT after adenosine conversion during the study period (conversion to arrival at emergency department). No significant difference in length of asystolic pause or in outcome was detected between the true PSVT cases and the AF cases receiving adenosine. There were no significant deleterious side effects in the adenosine group. It was concluded that adenosine is effective for prehospital treatment of narrow-complex tachycardias, and its safety profile appears to allow paramedic administration without "requisite" physician control. It should be used as directed by the manufacturer and may prove to be a valuable prehospital diagnostic adjunct in AF and hemodynamically stable abberant PSVT masked as wide-complex tachycardia.