Pericardial tamponade is one of the true emergencies in the practice of medicine. Since it is encountered infrequently, the diagnosis is often overlooked. Historical Review By injecting oil into the pericardial cavity, Cohnheim,1the first to experiment on animals, demonstrated that an increase in pericardial pressure causes a rise in venous pressure and a fall in arterial pressure. He concluded that the obstruction occurred at the venoatrial junction. Kuno2called attention to the dynamic interplay between increasing venous pressure and adrenaline. Using the heart-lung preparation, he increased the intrapericardial pressure until it matched the venous pressure, thus bringing the heart to a standstill, and he noted that raising the venous pressure would return blood flow. Kuno further observed that blood flow could also be restored with the injection of epinephrine, a fact that he attributed to a reduction in heart size and increase in the capacity of the