Combination of cardiac pacing and epinephrine does not always improve outcome of cardiopulmonary resuscitation

We hypothesized that the combination of cardiac pacing and epinephrine would yield a better efficacy for cardiopulmonary resuscitation (CPR) and the combination of 2 therapies at different opportunity would achieve the same results of CPR.Cardiac arrest was induced by clamping the tracheal tubes in 60 Sprague-Dawley rats. At 10 minutes of asphyxia, the animals were prospectively randomized into 5 groups (n = 12/group), and received saline (Sal-gro, 1 mL, intravenous [IV]), epinephrine (Epi-gro, 0.4 mg/kg, IV), pacing (Pac-gro, transesophageal cardiac pacing combined with saline 1 mL, IV), pacing + epinephrine group 1 (PE-gro1, transesophageal cardiac pacing combined with epinephrine 0.4 mg/kg, IV), or pacing + epinephrine group 2 (PE-gro2, transesophageal cardiac pacing combined with epinephrine 0.4 mg/kg, IV, 4 minutes after the transesophageal cardiac pacing initiating and failing to resuscitate the animals), followed by initiation of CPR.Restoration of spontaneous circulation in Sal-gro was lower than in Epi-gro, Pac-gro, PE-gro1, and PE-gro2 (16.67% vs 66.67%, 66.67%, 100%, and 100%; P < .05 or P < .001, respectively). The proportions of withdrawing ventilator and 2-hour survival proportions in Pac-gro and PE-gro2 were higher than in Epi-gro and PE-gro1 (8/8, 10/12 vs 1/8, 2/12, respectively, P < .01, and 7/8, 8/12 vs 1/8, 2/12, respectively, P < .05 or P < .01). Mean survival time in Pac-gro and PE-gro2 were longer than in Epi-gro and PE-gro1 (P < .05 or P < .01).Therefore, the combination of 2 therapies does not always improve outcome of CPR. It is obvious that the combination of transesophageal cardiac pacing with delayed administration of epinephrine yields a better outcome compared to the combination of 2 therapies at the same time during CPR in a rat asphyxia cardiac arrest model.