Effects of Anesthesia on Irradiated Animal

The relative influences of various anesthetics were investigated in mice and rats given whole-body irradiation of 200-1100 and 600-750 r respectively. The LD50 of radiation was 650 r in mice and approximates 700 r in rats. The 30-day mortality in rats was 0% at 625 and 650 r; 40% at 675 r, and 100% at 750 r. All of the anesthetic agents tested increased the mortality or morbidity, depending on the radiation dose. Chloroform and trifluoroethyl vinyl ether was most detrimental, halothane was least injurious, whereas cyclopropane and ethyl ether showed intermediate toxicity in irradiated animals. Hypercarbia and hypoxia developing during anesthesia did not appear to enhance mortality or morbidity following irradiation, however, burns (dipping rats in water at 62 deg C for 5 min) enhanced these effects in anesthetized-irradiated animals. Intravenous injection of lidocaine produced a higher mortality when carried out within a few hours after irradiation than 3 days later. It is concluded that halothane is the most satisfactory anesthetic agent following irradiation and that it is best given 24 hr or later after exposure. (H.H.D.)