Electrophysiology of atrial fibrillation and its prevention by coronary sinus pacing

OBJECTIVES: Prehospital providers are often unable to obtain intravenous (i.v.) access in cardiac arrest victims. While several drugs can be administered via the endotracheal (ET) route, serum drug levels are lower than those obtained with the i.v. route. The authors hypothesized that a 90-degree torso tilt after ET drug administration would increase drug levels. METHODS: A randomized, prospective, unblinded laboratory trial was conducted. Twenty-three mixed-breed domestic swine (20-25 kg) were sedated, anesthetized, instrumented, shocked into cardiac arrest, and randomized into three groups. Lidocaine was administered either i.v. (1.5 mg/kg), traditional ET (4.5 mg/kg), or ET followed by a 5-second 90-degree upright torso tilt (4.5 mg/kg). While standard CPR was performed, lidocaine levels were obtained at 0.5, 1, 2, 3, 4, and 5 minutes after administration. Repeated-measures ANOVA was used for data analysis (alpha = 0.05). RESULTS: Experimental ET compared with traditional ET administration produced significantly higher levels at all time points except 0.5 minutes. Comparing experimental ET with i.v. administration yielded significantly higher levels for the i.v. route at 0.5 and 1 minute and for the experimental ET route at 4 and 5 minutes. i.v. lidocaine administration resulted in significantly higher levels at 0.5, 1, and 2 minutes when compared with traditional ET administration. CONCLUSIONS: Endotracheal instillation of lidocaine followed by a 90-degree torso tilt resulted in better drug absorption, as evidenced by higher serum lidocaine levels, than did traditional recumbent ET delivery at all but the earliest time point and produced more sustained lidocaine levels than i.v. administration at 4 and 5 minutes. ET drug delivery followed by a 5-second 90-degree torso tilt and the mechanisms for this enhanced absorption warrant further investigation.