Early Hypotension Induced in the Rabbit by Whole Body X-Irradiation

¹ From the Department of Radiobiology, USAF School of Aviation Medicine, Randolph Field, Texas

Two different experiments were performed. In the first, the aortic blood pressure and the respiratory chest movements were continuously recorded on 21 rabbits that received 630 r total body x-irradiation at a dose rate of 10.6 r/min. and these recordings were compared with those of 15 control animals. All irradiated rabbits showed a pronounced initial reaction characterized by severe hypotension and acceleration of respiratory rate. This reaction became noticeable in the second half of the irradiation period; in the majority of animals circulatory collapse with a mean pressure of 50 mm Hg or less developed during the first postirradiation hour. Thereafter, all rabbits began to recover from the collapse with the exception of four animals that died. In the second experiment, blood of 16 animals irradiated under the conditions of the first experiment was withdrawn during the collapse phase and the plasma lyophilized. In comparison with control plasma, the lyophilized irradiated material produced a slight but consistent fall in blood pressure when injected into nonirradiated test rabbits.