Aminophylline in Bradyasystolic Cardiac Arrest

Out-of-hospital cardiac arrest treated by emergency medical services has an estimated incidence of 54.99 per 100,000 person years, which translates to some 155,000 episodes annually in the United States. Bradyasystole is the first recorded rhythm in up to 52 percent of cardiac arrests, and many additional patients with an initial cardiac arrest rhythm of ventricular fibrillation deteriorate to bradyasystole after defibrillation efforts. Survival to hospital discharge occurs in less than 3 percent of patients presenting with bradyasystole; however, due to its frequency, this rhythm accounts for over 17 percent of all cardiac arrest survivors. As a result, even a small improvement in survival from bradyasystolic cardiac arrest would result in thousands of lives saved annually.

Adenosine is an endogenous purine nucleoside that depresses the sinoatrial node, blocks atrioventricular conduction, inhibits the pacemaker activity of the His-Purkinje system and attenuates the effects of catecholamines. Since adenosine is produced and released by myocardial cells during ischemia and hypoxia, it may be a reversible factor in the etiology or perpetuation of bradyasystole. Aminophylline is a competitive antagonist of adenosine. The use of aminophylline for bradycardia and heart block has been described, and a number of anecdotal reports and small studies have been published on the use of aminophylline in cardiac arrest. We undertook this study to evaluate the effect of aminophylline during cardiopulmonary resuscitation (CPR) of patients with out-of-hospital bradyasystolic cardiac arrest unresponsive to initial therapy.

Inclusion criteria

• Cardiac arrest
• Bradyasystole either as the presenting rhythm or as a rhythm developing during the course of the resuscitation
• Endotracheally intubated and ventilated with 100% oxygen
• Intravenous (IV) access established
• Bradyasystolic without palpable pulses after 1 mg of epinephrine and 3 mg of atropine.

Exclusion criteria

• A do-not-resuscitate directive
• Pregnancy
• Evidence of hemorrhage, trauma or hypothermia as a cause of the cardiac arrest
• Renal dialysis
• Theophylline hypersensitivity
• Patients taking an oral theophylline product
• Resuscitations directed by a paramedic student under practicum supervision