The efficacy of atropine in the treatment of hemodynamically unstable bradycardia and atrioventricular block: prehospital and emergency department considerations

Abstract Objective: To determine the efficacy of atropine therapy in patients with hemodynamically compromising bradycardia or atrioventricular block (AVB) in the prehospital and emergency department settings. Methods: Design: Retrospective review of prehospital, emergency department, and hospital records. Participants: Prehospital patients with hemodynamically compromising bradycardia or AVB with evidence of spontaneous circulation who received atropine as delivered by emergency medical services personnel (advanced life support level). Setting: Urban/suburban fire department-based emergency medical service system with on-line medical control serving a population of approximately 1.6 million persons. Definitions: Hemodynamic instability was defined as the presence of any of the following: ischemic chest pain, dyspnea, syncope, altered mental status, and systolic blood pressure less than 90 mmHg. Bradycardia was defined as sinus bradycardia, junctional bradycardia, or idioventricular bradycardia (grouped as bradycardia) while AVB included first-, second- (types I and II), or third-degree (grouped as AVB). The response that occurred within one minute following each dose of atropine was defined as none, partial, complete, or adverse. Main results: Of 172 patients meeting entry criterion complete data was available for 131 (76.1%) and constitutes the study population. The mean age was 71 years. Fifty-one percent were female. Forty-five patients had AVB and 86 bradycardia. Patients with AVB were more likely to have a presenting systolic blood pressure less than 90 mmHg than those with bradycardia. In the 131 patients, responses to atropine were as follows: 26 (19.8%)=partial, 36 (27.5%)=complete, 65 (49.6%)=none, and 4 (2.3%)=adverse. Patients presenting with bradycardia (compared to AVB) more commonly: (1) received a single dose of atropine; (2) a lower total dose of atropine in the prehospital interval; (3) were more likely to arrive in the ED with a normal sinus rhythm; and (4) were less likely to receive additional atropine or isoproterenol in the ED. Those patients who achieved normal sinus rhythm over the total course of care were likely to have achieved that rhythm during the prehospital interval. There was no difference between groups in the likelihood of leaving the ED with a normal sinus rhythm achieved during the ED interval. Acute myocardial infarction was more common in patients presenting with AVB (55.5%) than with bradycardia (23.2%, P =0.001). Conclusions: Approximately one-half of patients who received atropine in the prehospital setting for compromising rhythms had either a partial or complete response to therapy. Adverse responses were uncommon. Those patients who presented with hemodynamically unstable bradycardia to EMS personnel responded more commonly to a single dose and a lower total dose of atropine compared to similar patients with AVB. Those patients who achieve normal sinus rhythm by ED discharge were likely to have achieved it during the prehospital interval.