ObjectivesTo evaluate instantaneous blood flow variations in the compression and relaxation phases of cardiopulmonary resuscitation (CPR) and the effect of epinephrine administration.DesignProspective, randomized, controlled trial.SettingExperimental laboratory in a university hospital.SubjectsTwenty-two anesthetized piglets.InterventionsA tracheostomy was performed and arterial, central venous, and pulmonary arterial catheters were inserted, followed by thoracotomy with placement of pulmonary arterial, aortic, and left anterior descending coronary arterial (extended study group) flow probes and a left atrial catheter. Ventricular fibrillation for 2 mins was followed by 10 mins of either open-chest (n equals 10) or closed-chest (n equals 12) CPR. Seven minutes after the initiation of CPR, all piglets received 0.5 mg of epinephrine iv; at 12 mins, direct current shocks were applied.Measurements and Main ResultsOpen-chest CPR generated greater systemic perfusion pressure than closed-chest CPR, especially during the relaxation phase, resulting in greater mean blood flow. With both open- and closed-chest CPR, antegrade pulmonary arterial and aortic blood flow occurred during compression, whereas antegrade left anterior descending coronary arterial blood flow occurred during relaxation. During relaxation, retrograde flow was found in the pulmonary artery and aorta. During compression, retrograde flow was found in the left anterior descending coronary artery. The administration of epinephrine had the following effects: a) increased the systemic perfusion pressure more during open- than closed-chest CPR; b) increased the systemic relaxation perfusion pressure more than the compression perfusion pressure; c) decreased mean pulmonary arterial and aortic blood flow, but substantially increased the mean left anterior descending coronary artery blood flow; and d) reduced the retrograde flow in the left anterior descending coronary artery.ConclusionsOpen-chest CPR generated greater systemic perfusion pressure and blood flow than closed-chest CPR. Epinephrine increased left anterior descending coronary artery blood flow but decreased total cardiac output, such that cerebral perfusion might be endangered. This problem will be studied separately.(Crit Care Med 1995; 23:1984-1996)