Mechanism of action of epinephrine in resuscitation from asphyxial arrest.

To determine the relative importance of the alpha and beta adrenergic effects of epinephrine in resuscitation, 32 dogs were studied in four groups. Group A (alpha blocked) received phenoxybenzamine, 70 mg/kg; group B (beta blocked), propranolol 5 mg/kg; group C (alpha and beta blocked) both drugs; and group D (control), no drug. After this treatment and 5 min of asphyxial arrest, all animals received closed chest cardiac massage (CCCM), artificial ventilation (AR), and epinephrine, 1 mg, iv. Resumption of spontaneous circulation occurred with the following frequency: group A, 0/8; group B, 6/8, group C, 0/8, group D, 7/8. The difference in successful resuscitation of the alpha blocked animals and the not alpha blocked animals is statistically significant (P less than or equal to 0.01). It is concluded that the efficacy of epinephrine in aiding resumption of spontaneous circulation from asphyxial arrest is due to alpha adrenergic receptor stimulation and that beta receptor stimulation is not important in determining outcome.