Reanimation of rats from body temperatures between 0 and 1° C by microwave diathermy

We have previously shown the possibility of reanimating the adult rat cooled to a body temperature of 0-1 C (Andjus, 1951; Andjus & Smith, 1954, 1955). The reanimation procedures described consisted, basically, of re-establishing the heart beat by local heating of the praecordium as the first step in resuscitation. The heating was achieved either by application of a hot metal spatula to the chest wall, or by using a focused beam of light as the heating device. The burns inevitably produced during heating by both techniques were in a great number of cases compatible with complete reanimation and long-term survival. Nevertheless, the possibility was not ruled out that a proportion of the secondary delayed deaths occurring after reanimation could be partially attributed to the thermal injury of peripheral tissues. Having at our disposal a magnetron microwave generator, we set out to investigate the possibility of using it for reanimation. It was hoped that burning of peripheral tissues would be avoided by the use of microwaves because of their satisfactory power of penetration. Furthermore, unlike the conventional diathermy apparatus which operates at a much lower frequency, it is possible with microwaves to achieve local heating of a small area.