['To investigate if naloxone combined with epinephrine can increase the resuscitation rate in cardiac arrest rat models induced by asphyxia.', 'Twenty-four rats were allocated into SA group (treated with 1 mL of saline, n = 8), EP group (treated with epinephrine 5 microg/100g, n = 8), and NA group (treated with epinephrine 5 microg/100g in combination with naloxone100 microg/100g, n = 8). Eight minutes after asphyxia, cardiopulmonary resuscitation was initiated, and different drugs were used in different groups at the same time.', 'Rates of restoration of spontaneous circulation (ROSC) were 25%, 75%, and 87.5% in SA, EP, and NA groups, respectively. The rate of ROSC in the NA group was significantly higher than that in the other 2 experimental groups (P < .05). The average resuscitation time in the NA group was much lower than that in the other 2 cohorts.'] Does small-dose naloxone combined with epinephrine improve the resuscitation of cardiopulmonary arrest?