Anaesthesia and efficacy of hyperbaric oxygen in radiation therapy

We have followed with great interest the data presented by Suit et al. (1979) in their recent letter as well as the letter by Hill and Bush (1979) concerning the effects of anaesthesia on the radiation response of tumour-bearing mice receiving hyperbaric oxygen therapy. We would like to suggest that the increased radiation response may be due in part to the inhibitory effects of pentobarbital on cell respiration. As seen in Fig. 1, the oxygen consumption of Ehrlich ascites tumour cells (ETC) and V79 lung cells is markedly inhibited in the presence of pentobarbital. Fifty per cent inhibition required approximately 0.5 mM drug for ETC and 0.6 mM for V79 lung cells. In vivo, alterations in oxygen utilization may also result from vasodilation and lowering of body temperature.