To investigate the effect of mild hypothermia on the myocardial and microcirculation dysfunction induced by epinephrine during early post-resuscitation in a rat model of cardiac arrest and cardiopulmonary resuscitation (CPR).

Transesophageal cardiac pacing was performed in order to elicit cardiac arrest for 5 min in SD male rats. Totally 40 rats were randomly (random number) divided into 4 groups (n=10): normothermic control group (N), normothermic epinephrine group (N+E), hypothermic control group (H), and hypothermic epinephrine group (H+E). Chest compression was then initiated. Epinephrine (0.02 mg/kg) or saline was administrated at 1 min during CPR. Restoration of spontaneous circulation (ROSC) was recorded, and the rates of ROSC were observed. Myocardial and microcirculatory function were observed at 1, 2, 3, and 4 h during early post-resuscitation. Serum lactate level was assessed at baseline and ROSC 4 h.

The ROSC rates were 10/10 in the H+E group, 9/10 in the N+E group, 4/10 in the H group, and 1/10 in the N group, respectively. Ejection fraction (EF) and cardiac output (CO) in the H+E group were significantly higher than that of other groups (P<0.05). Total vessel density, perfused vessel density, proportion of perfused vessels, and microvascular flow index in the H+E group were also significantly higher than those of other groups during early post-resuscitation. The serum lactate level in the H+E group was significantly lower than that in the N+E and H groups..

Both epinephrine and mild hypothermia can improve the success rate of resuscitation. However, mild hypothermia can improve the epinephrine induced myocardial and microcirculatory dysfunction during postresuscitation in the rat cardiac arrest.

Cardiac arrest; Cardiopulmonary resuscitation; Epinephrine; Mild hypothermia; Myocardial dysfunction; Microcirculation