The hemorrhagic syndrome of acute ionizing radiation illness produced in goats and swine by exposure to the atomic bomb at Bikini, 1946.

By E. P. CRONKITE, LT. COMDR., MC, USN T HE PROMINENCE and importance of the hemorrhagic syndrome of acute radiation illness have been amply demonstrated.’4 Shouse, Warren and Whipple4 described a severe intoxication in dogs produced by x-ray irradiation. Hemorrhage into all tissues was emphasized as an important factor causing death. This hemorrhagic syndrome was assumed to be the result of a rapid disappearance of platelets during the last few days of life. Dogs survived if a small area of the skeleton was shielded from radiation. This suggested to the authors that platelet production in the shielded area prevented the severe hemorrhage. However, they believed that other unknown factors may also have been concerned in the pathogenesis of the acute hemorrhage in the last day of life. Following the atomic bomb explosions at Hiroshima and Nagasaki, a severe hemorrhagic syndrome appeared in many casualties. ‘#{176} Warren5 observed whole blood coagulation times as long as four hours. In addition there was a marked reduction in circulating platelets and a depletion of megakaryocytes from the bone marrow. The above reports on human atomic bomb casualties emphasize the thrombocytopenia and in general tend to ascribe the appearance of the clotting defect to the thrombocytopenia which was usually present in the Japanese when the hemorrhagic phase of acute radiation illness appeared. Increased capillary fragility was also observed in the casualties. Allen et al.” 12 demonstrated a circulating anticoagulant with heparin-like properties in dogs after exposure to 450 r total body x-ray irradiation. The anticoagulant was neutralized by known antiheparin agents.’3’6 This preliminary paper based on the field tests at Bikini in July 1946 jS being reported because of the public and scientific interest in the atomic bomb tests. In addition, the data emphasize certain factors concerned with the hemorrhagic syndrome of radiation illness that are not widely appreciated at this time. It is fully recognized that the work was performed under field conditions and that in