The influence of a heat pulse on the thermally induced damage to tumour microcirculation

The effect of an initial short period of higher-temperature heat application on the stoppage of the microcirculation in the experimental rhabdomyosarcoma BA1112 in 'sandwich' chambers was investigated. The treatment consisted of an initial heat pulse of 45 degrees C for 10 min which was followed by a continuous exposure at 42.5 degrees C for 3 hr. Using the 't1/2 per degrees C' rule, the time equivalent of the heat pulse was 94 min. Taking this contribution into account, the derived 50% stoppage time of 151 min is essentially the same as the 152 min observed for 42.5 degrees C only treatments. The data therefore indicate that the effect of a heat pulse in the treatment can be accounted for by the customary correction procedure of one time exposure doubling per degrees C. However, it appeared that the microcirculation in the surrounding tumour bed was impaired more than was expected by this treatment.